@article {4941, title = {Biogeographic survey of soil bacterial communities across Antarctica}, journal = {Microbiome}, volume = {12}, year = {2024}, month = {01/2024}, abstract = {

Antarctica and its unique biodiversity are increasingly at risk from the effects of global climate change and other human influences. A significant recent element underpinning strategies for Antarctic conservation has been the development of a system of Antarctic Conservation Biogeographic Regions (ACBRs). The datasets supporting this classification are, however, dominated by eukaryotic taxa, with contributions from the bacterial domain restricted to Actinomycetota and Cyanobacteriota. Nevertheless, the ice-free areas of the Antarctic continent and the sub-Antarctic islands are dominated in terms of diversity by bacteria. Our study aims to generate a comprehensive phylogenetic dataset of Antarctic bacteria with wide geographical coverage on the continent and sub-Antarctic islands, to investigate whether bacterial diversity and distribution is reflected in the current ACBRs.

}, keywords = {LTER-MCM, Antarctic Conservation Biogeographic Regions (ACBRs), Antarctic soil microbiome, bioclimatic variables, biogeography, microbial diversity, regionalization, soils}, doi = {10.1186/s40168-023-01719-3}, url = {https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-023-01719-3}, author = {Varliero, Gilda and Lebre, Pedro H. and Byron Adams and Steven L. Chown and Peter Convey and Dennis, Paul G. and Fan, Dandan and Ferrari, Belinda and Frey, Beat and Hogg, Ian D. and Hopkins, David W. and Kong, Weidong and Makhalanyane, Thulani and Matcher, Gwynneth and Newsham, Kevin K. and Stevens, Mark I. and Weigh, Katherine V. and Cowan, Don A.} } @article {4926, title = {Long days and long nights: An integrative study reveals survival strategies of an Antarctic diatom during the cold and dark polar winter}, journal = {New Phytologist}, year = {2024}, month = {01/2024}, abstract = {

The vast majority of photosynthetic organisms on Earth have evolved under a circadian cycle, with many cellular processes being regulated by the predictable patterns of day and night. Polar algal species living in Arctic and Antarctic aquatic habitats are faced with bizarre light environments of continuous light during the short summer months and 24-h darkness during the winter, that is one long day transitioning into one long, cold night. It is well known that polar phytoplankton survive the winter and return in the summer to form blooms. In an article recently published in New Phytologist, Joli et al. (2023, doi: 10.1111/nph.19387) use an integrative approach to dissect how an Antarctic marine diatom not only survives the long, dark polar winter, but also recovers rapidly upon the onset of summer.

}, keywords = {LTER-MCM, aquatic habitats, circadian cycle, light environments, phytoplankton, polar}, issn = {0028-646X}, doi = {10.1111/nph.19536}, url = {https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19536}, author = {Rachael M. Morgan-Kiss} } @article {4940, title = {McMurdo Dry Valley lake edge {\textquoteleft}moats{\textquoteright}: The ecological intersection between terrestrial and aquatic polar desert habitat}, journal = {Antarctic Science}, year = {2024}, month = {04/2024}, pages = {1 - 17}, abstract = {

Aquatic ecosystems - lakes, ponds and streams - are hotspots of biodiversity in the cold and arid environment of Continental Antarctica. Environmental change is expected to increasingly alter Antarctic aquatic ecosystems and modify the physical characteristics and interactions within the habitats that they support. Here, we describe physical and biological features of the peripheral \‘moat\’ of a closed-basin Antarctic lake. These moats mediate connectivity amongst streams, lake and soils. We highlight the cyclical moat transition from a frozen winter state to an active open-water summer system, through refreeze as winter returns. Summer melting begins at the lakebed, initially creating an ice-constrained lens of liquid water in November, which swiftly progresses upwards, creating open water in December. Conversely, freezing progresses slowly from the water surface downwards, with water at 1 m bottom depth remaining liquid until May. Moats support productive, diverse benthic communities that are taxonomically distinct from those under the adjacent permanent lake ice. We show how ion ratios suggest that summer exchange occurs amongst moats, streams, soils and sub-ice lake water, perhaps facilitated by within-moat density-driven convection. Moats occupy a small but dynamic area of lake habitat, are disproportionately affected by recent lake-level rises and may thus be particularly vulnerable to hydrological change.

}, keywords = {LTER-MCM, connectivity, ecosystem, ice, microbial mats, transition}, issn = {0954-1020}, doi = {10.1017/S0954102024000087}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/mcmurdo-dry-valley-lake-edge-moats-the-ecological-intersection-between-terrestrial-and-aquatic-polar-desert-habitats/31D94DD51E651603482A3AE6E8A52A57}, author = {Stone, Michael S. and Devlin, Shawn and Ian Hawes and Kathleen A. Welch and Michael N. Gooseff and Cristina D. Takacs-Vesbach and Rachael M. Morgan-Kiss and Byron Adams and John E. Barrett and John C. Priscu and Peter T. Doran} } @article {4935, title = {Sentinel protist taxa of the McMurdo Dry Valley lakes, Antarctica: A review}, journal = {Frontiers in Ecology and Evolution}, volume = {12}, year = {2024}, month = {03/2024}, pages = {1323472}, abstract = {

High-latitude meromictic lakes such as those in the Antarctic McMurdo Dry Valleys (MDV) harbor aquatic ecosystems dominated by the microbial loop. Within this habitat, which is limited year-round by light and nutrients, protists, or single celled eukaryotes, play outsized roles in the food web as the dominant primary producers and the apex predators. Thus, the MDV lake ecosystem represents an ideal system to study the role of sentinel protist taxa in carbon and nutrient cycling. The perennially ice-covered lakes are part of the McMurdo Long Term Ecological Research (McM LTER; mcmlter.org) established in 1993. In this review we will highlight the diversity and trophic roles of the MDV lake protist community and compare environmental factors driving spatiotemporal patterns in key protist taxa in two lakes within the McM LTER, Lakes Bonney and Fryxell. We will then discuss lessons learned from manipulated experiments on the impact of current and future climate-driven environmental change on sensitive protist taxa. Last, we will integrate knowledge gained from 25 years of lab-controlled experiments on key photosynthetic protists to extend our understanding of the function of these extremophiles within the MDV aquatic food webs. Our research group has studied the distribution and function of the MDV microbial community for nearly two decades, training the next generation of scientists to tackle future problems of these globally significant microbes. This review article will also highlight early career scientists who have contributed to this body of work and represent the future of scientific understanding in the Anthropocene.

}, keywords = {LTER-MCM, Antarctica, Disturbance, McMurdo Dry Valley lakes, phytoplankton, protist}, doi = {10.3389/fevo.2024.1323472}, url = {https://www.frontiersin.org/articles/10.3389/fevo.2024.1323472}, author = {Rachael M. Morgan-Kiss and Popson, Devon and Pereira, Rochelle and Dolhi-Binder, J and Teufel, Amber G. and Li, Wei and Kalra, Isha and Sherwell, Shasten S. and Reynebeau, Emily and Cristina D. Takacs-Vesbach} } @article {4844, title = {Causes and characteristics of electrical resistivity variability in shallow (<4 m) soils in Taylor Valley, East Antarctica}, journal = {Journal of Geophysical Research: Earth Surface}, volume = {128}, year = {2023}, month = {02/2023}, pages = {e2022JF006696}, abstract = {

Airborne electromagnetic surveys collected in December 2011 and November 2018 and three soil sampling transects were used to analyze the spatial heterogeneity of shallow (\<4 m) soil properties in lower Taylor Valley (TV), East Antarctica. Soil resistivities from 2011 to 2018 ranged from \∼33 Ωm to \∼3,500 Ωm with 200 Ωm assigned as an upper boundary for brine-saturated sediments. Elevations below \∼50 m above sea level (masl) typically exhibit the lowest resistivities with resistivity increasing at high elevations on steeper slopes. Soil water content was empirically estimated from electrical resistivities using Archie\&$\#$39;s Law and range from \∼\<1\% to \∼68\% by volume. An increase in silt- and clay-sized particles at low elevations increases soil porosity but decreases hydraulic conductivity, promoting greater residence times of soil water at low elevations near Lake Fryxell. Soil resistivity variability between 2011 and 2018 shows soils at different stages of soil freeze-thaw cycles, which are caused predominantly by solar warming of soils as opposed to air temperature. This study furthers the understanding of the hydrogeologic structure of the shallow subsurface in TV and identifies locations of soils that are potentially prone to greater rates of thaw and resulting ecosystem homogenization of soil properties from projected increases in hydrological connectivity across the region over the coming decades.

}, keywords = {LTER-MCM, active layer, airborne electromagnetic surveys, McMurdo Dry Valleys, permafrost dynamics}, issn = {2169-9003}, doi = {10.1029/2022JF006696}, url = {https://onlinelibrary.wiley.com/doi/10.1029/2022JF006696}, author = {Gutterman, William S. and Peter T. Doran and Ross A. Virginia and John E. Barrett and Myers, Krista F. and Tulaczyk, Slawek M. and Foley, Neil T. and Jill A. Mikucki and Hilary A. Dugan and Grombacher, Denys and Bording, Thue S. and Auken, E.} } @article {4856, title = {Differentiating physical and biological storage of nitrogen along an intermittent Antarctic stream corridor}, journal = {Freshwater Science}, volume = {42}, year = {2023}, month = {09/2023}, abstract = {

In many temperate streams, biological uptake of N acts to attenuate the transport of excess N from allochthonous anthropogenic imports. Relatively few studies have determined how this N uptake relates to the magnitude of physical vs. biological N storage in the stream corridor, especially for intermittent systems where allochthonous N imports are often low and N transport may only occur during brief periods of streamflow. Glacial meltwater streams in the McMurdo Dry Valleys of Antarctica provide an excellent setting to quantify autochthonous N cycling and storage processes supported by abundant algal mats and well-connected hyporheic zones. We combined historic point-scale sediment and periphyton sample datasets with remote sensing-based modeling of periphyton coverage to estimate how much N was stored in periphyton biomass and the hyporheic zone of a 5-km long McMurdo Dry Valley stream corridor (\>100,000 m2). We contextualized these N storage calculations by estimating the magnitude of annual N imports to and exports from the stream corridor based on \>2 decades of streamflow and surface water data, source glacier ice cores and meltwater data, and past studies of local aeolian deposition and biological N fixation rates. We found that in this highly oligotrophic system, stream corridor-scale N storage was ~1000x that of total annual N import or export fluxes. More than 90\% of this temporarily stored N was autochthonous organic matter in the shallow (\<10 cm) hyporheic zone, which acts as a reservoir that sustains N availability in the water column. Despite its location in a polar desert devoid of higher-order vegetation, area-normalized N storage (~40 g N/m2) was greater than that reported for streams at lower latitudes (~1\–22 g N/m2). We also demonstrated that NH4+ sorption to stream sediment may be an important physicochemical N storage mechanism that responds to short-term fluctuations in streamflow and governs the mobility of inorganic N. Altogether, this research illustrates the importance of quantifying N storage within stream corridors when evaluating the significance of internal cycling and physical retention processes that modulate N availability.

}, keywords = {LTER-MCM, hyporheic zone, McMurdo LTER, nitrogen cycling, nutrient budget, organic matter, periphyton}, issn = {2161-9549}, doi = {10.1086/725676}, url = {https://www.journals.uchicago.edu/doi/10.1086/725676}, author = {Singley, Joel G. and Salvatore, Mark R. and Michael N. Gooseff and Diane M. McKnight and Eve-Lyn S. Hinckley} } @article {4942, title = {The distribution of surface soil moisture over space and time in eastern Taylor Valley, Antarctica}, journal = {Remote Sensing}, volume = {15}, year = {2023}, month = {06/2023}, pages = {3170}, abstract = {

Available soil moisture is thought to be the limiting factor for most ecosystem processes in the cold polar desert of the McMurdo Dry Valleys (MDVs) of Antarctica. Previous studies have shown that microfauna throughout the MDVs are capable of biological activity when sufficient soil moisture is available (~2\–10\% gravimetric water content), but few studies have attempted to quantify the distribution, abundance, and frequency of soil moisture on scales beyond that of traditional field work or local field investigations. In this study, we present our work to quantify the soil moisture content of soils throughout the Fryxell basin using multispectral satellite remote sensing techniques. Our efforts demonstrate that ecologically relevant abundances of liquid water are common across the landscape throughout the austral summer. On average, the Fryxell basin of Taylor Valley is modeled as containing 1.5 \± 0.5\% gravimetric water content (GWC) across its non-fluvial landscape with ~23\% of the landscape experiencing an average GWC \> 2\% throughout the study period, which is the observed limit of soil nematode activity. These results indicate that liquid water in the soils of the MDVs may be more abundant than previously thought, and that the distribution and availability of liquid water is dependent on both soil properties and the distribution of water sources. These results can also help to identify ecological hotspots in the harsh polar Antarctic environment and serve as a baseline for detecting future changes in the soil hydrological regime.

}, keywords = {LTER-MCM, Dry valleys, ecology, hydrology, remote sensing, soil moisture}, doi = {10.3390/rs15123170}, url = {https://www.mdpi.com/2072-4292/15/12/3170}, author = {Salvatore, Mark R. and Barrett, John E. and Fackrell, Laura E. and Sokol, Eric R. and Levy, Joseph S. and Kuentz, Lily C. and Gooseff, Michael N. and Adams, Byron J. and Power, Sarah N. and Knightly, J. Paul and Matul, Haley M. and Szutu, Brian and Doran, Peter T.} } @article {4833, title = {Ecological stoichiometry drives the evolution of soil nematode life history traits}, journal = {Soil Biology and Biochemistry}, volume = {177}, year = {2023}, month = {02/2023}, pages = {108891}, abstract = {

Ecological stoichiometry is a useful theoretical framework for understanding the sources and controls on nutrient availability that structure the composition and diversity of biotic communities. One such relationship is that organismal development rate is positively linked to cellular Phosphorus (P). We hypothesized that P availability, relative to other nutrients, e.g., nitrogen and carbon, would drive the evolution of traits associated with organismal growth and development. We examined the effects of P availability both in situ and in vitro, on free-living soil nematodes. We found that P-deficient environments produce predictable changes in the ecology and evolution of important life history traits. Our results identify altered rRNA gene copy number and subsequent changes in gene expression and protein synthesis as mechanisms by which P-deficiency influences these traits. These findings have important implications for explaining soil ecological and evolutionary patterns across multiple levels of organization, including the structure and functioning of organisms, populations, communities, and ecosystems.

}, keywords = {LTER-MCM, elemental stoichiometry, growth rate hypothesis, life history theory, molecular evolution, nematoda, rRNA}, doi = {10.1016/j.soilbio.2022.108891}, url = {https://www.sciencedirect.com/science/article/pii/S0038071722003480}, author = {Xue, Xia and Bishwo N. Adhikari and Ball, Becky and John E. Barrett and Miao, Jinxin and Perkes, Ammon and Martin, Mac and Breana L. Simmons and Diana H. Wall and Byron Adams} } @article {4843, title = {Extreme cold (-69.1{\textdegree}C) in the McMurdo Dry Valleys}, journal = {Antarctic Science}, volume = {30}, year = {2023}, month = {03/2023}, pages = {1-4}, keywords = {LTER-MCM, climate, extreme, meteorology, temperature, weather}, issn = {0954-1020}, doi = {10.1017/S0954102022000451}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/extreme-cold-691c-in-the-mcmurdo-dry-valleys/3516874750E5EF96365A26E8D49CA4EC}, author = {Peter T. Doran and Myers, Krista F. and Christopher P. McKay and David Bromwich} } @article {4937, title = {High salt-induced PSI-supercomplex is associated with high CEF and attenuation of state transitions}, journal = {Photosynthesis Research}, volume = {157}, year = {2023}, month = {09/2023}, pages = {65 - 84}, abstract = {

While PSI-driven cyclic electron flow (CEF) and assembly of thylakoid supercomplexes have been described in model organisms like Chlamydomonas reinhardtii, open questions remain regarding their contributions to survival under long-term stress. The Antarctic halophyte, C. priscuii UWO241 (UWO241), possesses constitutive high CEF rates and a stable PSI-supercomplex as a consequence of adaptation to permanent low temperatures and high salinity. To understand whether CEF represents a broader acclimation strategy to short- and long-term stress, we compared high salt acclimation between the halotolerant UWO241, the salt-sensitive model, C. reinhardtii, and a moderately halotolerant Antarctic green alga, C. sp. ICE-MDV (ICE-MDV). CEF was activated under high salt and associated with increased non-photochemical quenching in all three Chlamydomonas species. Furthermore, high salt-acclimated cells of either strain formed a PSI-supercomplex, while state transition capacity was attenuated. How the CEF-associated PSI-supercomplex interferes with state transition response is not yet known. We present a model for interaction between PSI-supercomplex formation, state transitions, and the important role of CEF for survival during long-term exposure to high salt.

}, keywords = {LTER-MCM, acclimation, Antarctica, Chlamydomonas, Cyclic electron flow, PSI-supercomplex, salinity, state transitions}, issn = {0166-8595}, doi = {10.1007/s11120-023-01032-y}, url = {https://link.springer.com/10.1007/s11120-023-01032-y}, author = {Kalra, Isha and Wang, Xin and Zhang, Ru and Rachael M. Morgan-Kiss} } @article {4839, title = {Impact of meltwater flow intensity on the spatiotemporal heterogeneity of microbial mats in the McMurdo Dry Valleys, Antarctica}, journal = {ISME Communications}, volume = {3}, year = {2023}, month = {01/2023}, pages = {3}, abstract = {

The meltwater streams of the McMurdo Dry Valleys are hot spots of biological diversity in the climate-sensitive polar desert landscape. Microbial mats, largely comprised of cyanobacteria, dominate the streams which flow for a brief window of time (~10 weeks) over the austral summer. These communities, critical to nutrient and carbon cycling, display previously uncharacterized patterns of rapid destabilization and recovery upon exposure to variable and physiologically detrimental conditions. Here, we characterize changes in biodiversity, transcriptional responses and activity of microbial mats in response to hydrological disturbance over spatiotemporal gradients. While diverse metabolic strategies persist between marginal mats and main channel mats, data collected from 4 time points during the austral summer revealed a homogenization of the mat communities during the mid-season peak meltwater flow, directly influencing the biogeochemical roles of this stream ecosystem. Gene expression pattern analyses identified strong functional sensitivities of nitrogen-fixing marginal mats to changes in hydrological activities. Stress response markers detailed the environmental challenges of each microhabitat and the molecular mechanisms underpinning survival in a polar desert ecosystem at the forefront of climate change. At mid and end points in the flow cycle, mobile genetic elements were upregulated across all mat types indicating high degrees of genome evolvability and transcriptional synchronies. Additionally, we identified novel antifreeze activity in the stream microbial mats indicating the presence of ice-binding proteins (IBPs). Cumulatively, these data provide a new view of active intra-stream diversity, biotic interactions and alterations in ecosystem function over a high-flow hydrological regime.

}, keywords = {LTER-MCM}, doi = {10.1038/s43705-022-00202-8}, url = {https://www.nature.com/articles/s43705-022-00202-8}, author = {Zoumplis, Angela and Kolody, Bethany C. and Kaul, Drishti and Zheng, Hong and Venepally, Pratap and Diane M. McKnight and Cristina D. Takacs-Vesbach and DeVries, Arthur L. and Allen, Andrew E.} } @article {4867, title = {Long-term changes in concentration and yield of riverine dissolved silicon from the poles to the tropics}, journal = {Global Biogeochemical Cycles}, year = {2023}, month = {08/2023}, abstract = {

Riverine exports of silicon (Si) influence global carbon cycling through the growth of marine diatoms, which account for \∼25\% of global primary production. Climate change will likely alter river Si exports in biome-specific ways due to interacting shifts in chemical weathering rates, hydrologic connectivity, and metabolic processes in aquatic and terrestrial systems. Nonetheless, factors driving long-term changes in Si exports remain unexplored at local, regional, and global scales. We evaluated how concentrations and yields of dissolved Si (DSi) changed over the last several decades of rapid climate warming using long-term datasets from 60 rivers and streams spanning the globe (e.g., Antarctic, tropical, temperate, boreal, alpine, Arctic systems). We show that widespread changes in river DSi concentration and yield have occurred, with the most substantial shifts occurring in alpine and polar regions. The magnitude and direction of trends varied within and among biomes, were most strongly associated with differences in land cover, and were often independent of changes in river discharge. These findings indicate that there are likely diverse mechanisms driving change in river Si biogeochemistry that span the land-water interface, which may include glacial melt, changes in terrestrial vegetation, and river productivity. Finally, trends were often stronger in months outside of the growing season, particularly in temperate and boreal systems, demonstrating a potentially important role of shifting seasonality for the flux of Si from rivers. Our results have implications for the timing and magnitude of silica processing in rivers and its delivery to global oceans.

}, keywords = {LTER-MCM, biogeochemistry, river, silica, silicon, stream, trends}, issn = {0886-6236}, doi = {10.1029/2022GB007678}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GB007678}, author = {Jankowski, Kathi Jo and Johnson, Keira and Sethna, Lienne and Julian, Paul and Wymore, Adam S. and Shogren, Arial J. and Thomas, Patrick K. and Sullivan, Pamela L. and Diane M. McKnight and McDowell, William H. and Heindel, Ruth C and Jones, Jeremy B. and Wollheim, Wilfred and Abbott, Benjamin and Deegan, Linda and Carey, Joanna C.} } @article {4864, title = {Nitrogen fixation facilitates stream microbial mat biomass across the McMurdo Dry Valleys, Antarctica}, journal = {Biogeochemistry}, year = {2023}, month = {07/2023}, abstract = {

Nitrogen (N) fixation is a fundamental mechanism by which N enters streams. Yet, because of modern N saturation, it is difficult to study the importance of N-fixation to stream nutrient budgets. Here, we utilized relatively simple and pristine McMurdo Dry Valley streams to investigate the role of N-fixing Nostoc abundance, streamwater dissolved inorganic N (DIN) concentration, and distance from the source glacier in regulating the elemental and isotopic composition of three microbial mat types (black, orange, and green) at the landscape scale. We found Nostoc-based black mats were the most enriched in δ15N, and δ15N signatures of mats increased where Nostoc was abundant, but did not surpass the atmospheric standard (δ15N \≈ 0\‰). Furthermore, green and orange mat δ15N signatures became more depleted with increasing DIN, indicating that mats utilize glacial meltwater-sourced N when available. The distance from the source glacier explained limited variability in mat δ15N across sites, indicating the influence of individual stream characteristics on N spiraling. To further explore longitudinal N spiraling processes generating observed δ15Ν patterns, we developed a simple steady-state mathematical model. Analysis of plausible scenarios with this model confirmed that streams both have the capacity to remove allochthonous DIN over the plausible range of inputs, and that internal N sources are required to account for δ15N signatures and observed DIN concentrations at stream outlets. Collectively, these data and modeling results demonstrate that N-fixation exerts substantial influence within and across these streams, and is presumably dependent upon interconnected organic matter reserves, mineralization rates, and geomorphology.

}, keywords = {LTER-MCM, biofilm, C, cyanobacteria, hyporheic zone, MCM LTER, mineralization, N, P biogeochemistry}, doi = {10.1007/s10533-023-01069-0}, url = {https://link.springer.com/article/10.1007/s10533-023-01069-0}, author = {Tyler J. Kohler and Singley, Joel G. and Wlostowski, Adam and Diane M. McKnight} } @article {4866, title = {Sediment oxygen consumption in Antarctic subglacial environments}, journal = {Limnology and Oceanography}, volume = {68}, year = {2023}, month = {07/2023}, pages = {1557 - 1566}, abstract = {

Oxygen consumption in aquatic sediments is an indicator of overall biological activity of the ecosystem. As such, rates of sedimentary oxygen utilization are well documented for much of the open oceans and freshwater lakes. However, there are few direct measurements of sedimentary oxygen consumption from Antarctic subglacial aquatic sediments. We report the first microsensor oxygen profiles and derived sedimentary oxygen consumption rates from beneath the Ross Ice Shelf and a subglacial lake beneath the West Antarctic Ice Sheet. Rates of oxygen consumption in these two environments are relatively low, but comparable to those reported from ice-free polar oceans and oligotrophic Arctic lakes. Our study demonstrates the presence of oxygen within Antarctic subglacial aquatic sediments and its importance for oxygen-consuming microorganisms living in these ecosystems.

}, keywords = {LTER-MCM}, issn = {0024-3590}, doi = {10.1002/lno.12366}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/10.1002/lno.12366}, author = {Alexander B. Michaud and John C. Priscu} } @mastersthesis {4857, title = {Snow distribution and influence in Taylor Valley, Antarctica, using remote sensing}, volume = {M.S.}, year = {2023}, month = {04/2023}, school = {Louisiana State University}, type = {masters}, address = {Baton Rouge, LA}, abstract = {

The McMurdo Dry Valleys is the largest ice-free area in Antarctica, but seasonal snow covers the valley floors sporadically throughout the year. In this study, a model to estimate areal snow coverage from satellite imagery was created. An area-volume model was created to estimate the amount of snow water equivalent (SWE) from the snow area extracted from the imagery. Snow cover influences the total albedo, the hydrologic budget, and the soil moisture and soil temperature in Taylor Valley (TV). Quantifying snow precipitation in TV is challenging because snow redistributes with winds, sublimates, or melts within a short period. Previous estimates found the amount of snow precipitation in TV is small, less than 100 mm/a. (SWE); even so, snow cover may influence processes in the valley. To better understand the controls and feedbacks of snow cover in the valley, a long-term record of spatially distributed abundance is required. This research creates a long-term record of snow cover data in TV using satellite images. The area of snowpacks was calculated by creating a classification scheme based on the brightness of panchromatic images. During the 2021-2022 field season, 250 m x 250 m sampling quadrats were surveyed to approximate how area and volume relate to SWE. Volumetric SWE was calculated by measuring in situ the length, width, depth, and density of each snowpack in the quadrat. There is a strong relationship between the area and the volume of the snowpacks (R2=0.942, P=0.182). With this information, estimates of the SWE can be made from the area calculated from satellite imagery. The average snow area for the entire extent of TV in late winter/early summer (September-December) from 2004 to 2022 is 65.26 km2, the average SWE is 0.0310 km3, and the average SWE depth is 75.72 mm. The amount of areal snow coverage is important when calculating the energy balance of TV, as well as understanding the availability of soil moisture to the soil ecosystem year-to-year. The available SWE can also influence seasonal surface and subsurface hydrology. While most precipitated snow in TV will sublimate or be redistributed by the wind, it is important to quantify how much snow has accumulated each season, especially with a warming climate, which could drastically influence snow accumulation and dynamics in TV.

}, keywords = {LTER-MCM}, url = {https://digitalcommons.lsu.edu/gradschool_theses/5749}, author = {McNulty, Katherine} } @article {4767, title = {An Antarctic alga that can survive the extreme cold}, journal = {Frontiers for Young Minds}, volume = {10}, year = {2022}, month = {05/2022}, pages = {740838}, abstract = {

Microscopic algae are tougher than you might think. Some can even survive the extreme cold. In this article, we describe one of the coolest algae of all, the Antarctic green alga called Chlamydomonas sp. UWO241. This one-celled super-organism lives deep in the frigid waters of a remote and permanently ice-covered lake in Antarctica. How does this little alga thrive in such a barren and unwelcoming place? Well, dive into this article to learn how studying the genome of UWO241 is helping scientists better understand this amazingly hardy alga.

}, keywords = {LTER-MCM}, doi = {10.3389/frym.2022.740838}, url = {https://kids.frontiersin.org/articles/10.3389/frym.2022.740838}, author = {Smith, David R. and Leung, Arthur and Zhang, Xi and Cvetkovska, Marina and Rachael M. Morgan-Kiss and H{\"u}ner, Norman P. A.} } @article {4814, title = {Antarctic lake phytoplankton and bacteria from near-surface waters exhibit high sensitivity to climate-driven disturbance}, journal = {Environmental Microbiology}, year = {2022}, month = {07/2022}, abstract = {

The McMurdo Dry Valleys (MDVs), Antarctica, represent a cold, desert ecosystem poised on the threshold of melting and freezing water. The MDVs have experienced dramatic signs of climatic change, most notably a warm austral summer in 2001\–2002 that caused widespread flooding, partial ice cover loss and lake level rise. To understand the impact of these climatic disturbances on lake microbial communities, we simulated lake level rise and ice-cover loss by transplanting dialysis-bagged communities from selected depths to other locations in the water column or to an open water perimeter moat. Bacteria and eukaryote communities residing in the surface waters (5 m) exhibited shifts in community composition when exposed to either disturbance, while microbial communities from below the surface were largely unaffected by the transplant. We also observed an accumulation of labile dissolved organic carbon in the transplanted surface communities. In addition, there were taxa-specific sensitivities: cryptophytes and Actinobacteria were highly sensitive particularly to the moat transplant, while chlorophytes and several bacterial taxa increased in relative abundance or were unaffected. Our results reveal that future climate-driven disturbances will likely undermine the stability and productivity of MDV lake phytoplankton and bacterial communities in the surface waters of this extreme environment.

}, keywords = {LTER-MCM}, doi = {10.1111/1462-2920.16113}, url = {https://onlinelibrary.wiley.com/doi/10.1111/1462-2920.16113}, author = {Sherwell, Shasten S. and Kalra, Isha and Li, Wei and Diane M. McKnight and John C. Priscu and Rachael M. Morgan-Kiss} } @article {4936, title = {Antibiotic resistance genes and taxa analysis from mat and planktonic microbiomes of Antarctic perennial ice-covered Lake Fryxell and Lake Bonney}, journal = {Antarctic Science}, volume = {34}, year = {2022}, month = {12/2022}, pages = {408 - 422}, abstract = {

The perennial ice-covered lakes of the Antarctic McMurdo Dry Valleys harbour oligotrophic microbial communities that are separated geographically from other aquatic systems. Their microbiomes include planktonic microbes as well as lift-off mat communities that emerge from the ice. We used the ShortBRED protein family profiler to quantify the antibiotic resistance genes (ARGs) from metagenomes of lift-off mats emerging from ice and from filtered water samples of Lake Fryxell and Lake Bonney. The overall proportion of ARG hits was similar to that found in temperate-zone rural ponds with moderate human inputs. Specific ARGs showed distinct distributions for the two lakes and for mat vs planktonic sources. Metagenomic taxa distributions showed that mat phototrophs consisted mainly of cyanobacteria or Betaproteobacteria, whereas the water column phototrophs were mainly protists. An enrichment culture of the Betaproteobacterium Rhodoferax antarcticus from a Lake Fryxell mat sample showed an unusual mat-forming phenotype not previously reported for this species. Its genome showed no ARGs associated with Betaproteobacteria but had ARGs consistent with a minor Pseudomonas component. The Antarctic lake mats and water showed specific ARGs distinctive to the mat and water sources, but overall ARG levels were similar to those of temperate water bodies with moderate human inputs.

}, keywords = {LTER-MCM, microbial mat, Rhodoferax, Taylor Valley}, issn = {0954-1020}, doi = {10.1017/S0954102022000360}, url = {https://www.cambridge.org/core/product/identifier/S0954102022000360/type/journal_article}, author = {Tallada, Sheetal and Hall, Grant and Barich, Daniel and Rachael M. Morgan-Kiss and Slonczewski, Joan L.} } @article {4713, title = {Blowin{\textquoteright} in the wind: Dispersal, structure, and metacommunity dynamics of aeolian diatoms in the McMurdo Sound region, Antarctica}, journal = {Journal of Phycology}, volume = {58}, year = {2022}, month = {02/2022}, pages = {36-54}, abstract = {

Diatom metacommunities are structured by environmental, historical, and spatial factors that are often attributed to organism dispersal. In the McMurdo Sound region (MSR) of Antarctica, wind connects aquatic habitats through delivery of inorganic and organic matter. We evaluated the dispersal of diatoms in aeolian material and its relation to the regional diatom metacommunity using light microscopy and 18S rRNA high-throughput sequencing. The concentration of diatoms ranged from 0 to 8.76 * 106 valves \· g-1 dry aeolian material. Up to 15\% of whole cells contained visible protoplasm, indicating that up to 3.43 * 104 potentially viable individuals could be dispersed in a year to a single 2 cm2\ site. Diatom DNA and RNA was detected at each site, reinforcing the likelihood that we observed dispersal of viable diatoms. Of the 50 known morphospecies in the MSR, 72\% were identified from aeolian material using microscopy. Aeolian community composition varied primarily by site. Meanwhile, each aeolian community was comprised of morphospecies found in aquatic communities from the same lake basin. These results suggest that aeolian diatom dispersal in the MSR is spatially structured, is predominantly local, and connects local aquatic habitats via a shared species pool. Nonetheless, aeolian community structure was distinct from that of aquatic communities, indicating that intrahabitat dispersal and environmental filtering also underlie diatom metacommunity dynamics. The present study confirms that a large number of diatoms are passively dispersed by wind across a landscape characterized by aeolian processes, integrating the regional flora and contributing to metacommunity structure and landscape connectivity.

}, keywords = {LTER-MCM, 18S rRNA, airborne, algae, assembly, Bacillariophyta, biogeography, connectivity, high-throughput sequencing}, issn = {0022-3646}, doi = {10.1111/jpy.13223}, url = {https://onlinelibrary.wiley.com/doi/10.1111/jpy.13223}, author = {Schulte, Nicholas O. and Khan, Alia L. and Smith, Emma W. and Zoumplis, Angela and Kaul, Drishti and Allen, Andrew E. and Adams, Byron J. and Diane M. McKnight} } @article {4766, title = {Cyclic electron flow (CEF) and ascorbate pathway activity provide constitutive photoprotection for the photopsychrophile, Chlamydomonas sp. UWO 241~(renamed Chlamydomonas priscuii)}, journal = {Photosynthesis Research}, volume = {151}, year = {2022}, month = {03/2022}, pages = {235 - 250}, abstract = {

Under environmental stress, plants and algae employ a variety of strategies to protect the photosynthetic apparatus and maintain photostasis. To date, most studies on stress acclimation have focused on model organisms which possess limited to no tolerance to stressful extremes. We studied the ability of the Antarctic alga Chlamydomonas sp. UWO 241 (UWO 241) to acclimate to low temperature, high salinity or high light. UWO 241 maintained robust growth and photosynthetic activity at levels of temperature (2 \°C) and salinity (700 mM NaCl) which were nonpermissive for a mesophilic sister species, Chlamydomonas raudensis SAG 49.72 (SAG 49.72). Acclimation in the mesophile involved classic mechanisms, including downregulation of light harvesting and shifts in excitation energy between photosystem I and II. In contrast, UWO 241 exhibited high rates of PSI-driven cyclic electron flow (CEF) and a larger capacity for nonphotochemical quenching (NPQ). Furthermore, UWO 241 exhibited constitutively high activity of two key ascorbate cycle enzymes, ascorbate peroxidase and glutathione reductase and maintained a large ascorbate pool. These results matched the ability of the psychrophile to maintain low ROS under short-term photoinhibition conditions. We conclude that tight control over photostasis and ROS levels are essential for photosynthetic life to flourish in a native habitat of permanent photooxidative stress. We propose to rename this organism Chlamydomonas priscuii.

}, keywords = {LTER-MCM, Antarctica, ascorbate, Cyclic electron flow, Photosystem I, Psychrophile, ROS}, doi = {10.1007/s11120-021-00877-5}, url = {https://link.springer.com/article/10.1007/s11120-021-00877-5}, author = {Stahl-Rommel, Sarah and Kalra, Isha and D{\textquoteright}Silva, Susanna and Hahn, Mark M. and Popson, Devon and Cvetkovska, Marina and Rachael M. Morgan-Kiss} } @article {4815, title = {Dissolved organic carbon chemostasis in Antarctic polar desert streams}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {127}, year = {2022}, month = {07/2022}, pages = {e2021JG006649}, abstract = {

Dissolved organic carbon (DOC) is a key variable impacting stream biogeochemical processes. The relationship between DOC concentration (C) and stream discharge (q) can elucidate spatial and temporal DOC source dynamics in watersheds. In the ephemeral glacial meltwater streams of the McMurdo Dry Valleys (MDV), Antarctica, the C-q relationship has been applied to dissolved inorganic nitrogen and weathering solutes including silica, which all exhibit chemostatic C-q behavior; but DOC-q dynamics have not been studied. DOC concentrations here are low compared to temperate streams, in the range of 0.1-2 mg C l-1, and their chemical signal clearly indicates derivation from microbial biomass (benthic mats and hyporheic biofilm). To investigate whether the DOC generation rate from these autochthonous organic matter pools was sufficient to maintain chemostasis for DOC, despite these streams\&$\#$39; large diel and interannual fluctuations in discharge, we fit the long-term DOC-q data to a power law and an advection-reaction model. Model outputs and coefficients of variation characterize the DOC-q relationship as chemostatic for several MDV streams. We propose a conceptual model in which hyporheic carbon storage, hyporheic exchange rates, and net DOC generation rates are key interacting components that enable chemostatic DOC-q behavior in MDV streams. This model clarifies the role of autochthonous carbon stores in maintaining DOC chemostasis and may be useful for examining these relationships in temperate systems, which typically have larger sources of bioavailable autochthonous organic carbon than MDV streams but where this autochthonous signal could be masked by a stronger allochthonous contribution.

}, keywords = {LTER-MCM, Antarctica, chemostasis, concentration-discharge, DOC, ephemeral streams, LTER}, doi = {10.1029/2021JG006649}, url = {https://onlinelibrary.wiley.com/doi/10.1029/2021JG006649}, author = {Torrens, Christa L. and Michael N. Gooseff and Diane M. McKnight} } @article {4718, title = {Elevational constraints on the composition and genomic attributes of microbial communities in Antarctic soils}, journal = {mSystems}, volume = {7}, year = {2022}, month = {01/2022}, pages = {e01330-21}, abstract = {

The inland soils found on the Antarctic continent represent one of the more challenging environments for microbial life on Earth. Nevertheless, Antarctic soils harbor unique bacterial and archaeal (prokaryotic) communities able to cope with extremely cold and dry conditions. These communities are not homogeneous, and the taxonomic composition and functional capabilities (genomic attributes) of these communities across environmental gradients remain largely undetermined. We analyzed the prokaryotic communities in soil samples collected from across the Shackleton Glacier region of Antarctica by coupling quantitative PCR, marker gene amplicon sequencing, and shotgun metagenomic sequencing. We found that elevation was the dominant factor explaining differences in the structures of the soil prokaryotic communities, with the drier and saltier soils found at higher elevations harboring less diverse communities and unique assemblages of cooccurring taxa. The higher-elevation soil communities also had lower maximum potential growth rates (as inferred from metagenome-based estimates of codon usage bias) and an overrepresentation of genes associated with trace gas metabolism. Together, these results highlight the utility of assessing community shifts across pronounced environmental gradients to improve our understanding of the microbial diversity found in Antarctic soils and the strategies used by soil microbes to persist at the limits of habitability.

}, keywords = {LTER-MCM, Antarctica, microbial ecology, soil microbiology, soils}, doi = {10.1128/msystems.01330-21}, url = {https://journals.asm.org/doi/full/10.1128/msystems.01330-21}, author = {Dragone, Nicholas B. and Henley, Jessica B. and Holland-Moritz, Hannah and Melisa A. Diaz and Hogg, Ian D. and W. Berry Lyons and Diana H. Wall and Byron Adams and Noah Fierer}, editor = {Mackelprang, Rachel} } @article {4834, title = {Lipid biomarkers from microbial mats on the McMurdo Ice Shelf, Antarctica: Signatures for life in the cryosphere}, journal = {Frontiers in Microbiology}, volume = {13}, year = {2022}, month = {06/2022}, pages = {903621}, abstract = {

Persistent cold temperatures, a paucity of nutrients, freeze-thaw cycles, and the strongly seasonal light regime make Antarctica one of Earth\’s least hospitable surface environments for complex life. Cyanobacteria, however, are well-adapted to such conditions and are often the dominant primary producers in Antarctic inland water environments. In particular, the network of meltwater ponds on the \‘dirty ice\’ of the McMurdo Ice Shelf is an ecosystem with extensive cyanobacteria-dominated microbial mat accumulations. This study investigated intact polar lipids (IPLs), heterocyte glycolipids (HGs), and bacteriohopanepolyols (BHPs) in combination with 16S and 18S rRNA gene diversity in microbial mats of twelve ponds in this unique polar ecosystem. To constrain the effects of nutrient availability, temperature and freeze-thaw cycles on the lipid membrane composition, lipids were compared to stromatolite-forming cyanobacterial mats from ice-covered lakes in the McMurdo Dry Valleys as well as from (sub)tropical regions and hot springs. The 16S rRNA gene compositions of the McMurdo Ice Shelf mats confirm the dominance of Cyanobacteria and Proteobacteria while the 18S rRNA gene composition indicates the presence of Ochrophyta, Chlorophyta, Ciliophora, and other microfauna. IPL analyses revealed a predominantly bacterial community in the meltwater ponds, with archaeal lipids being barely detectable. IPLs are dominated by glycolipids and phospholipids, followed by aminolipids. The high abundance of sugar-bound lipids accords with a predominance of cyanobacterial primary producers. The phosphate-limited samples from the (sub)tropical, hot spring, and Lake Vanda sites revealed a higher abundance of aminolipids compared to those of the nitrogen-limited meltwater ponds, affirming the direct affects that N and P availability have on IPL compositions. The high abundance of polyunsaturated IPLs in the Antarctic microbial mats suggests that these lipids provide an important mechanism to maintain membrane fluidity in cold environments. High abundances of HG keto-ols and HG keto-diols, produced by heterocytous cyanobacteria, further support these findings and reveal a unique distribution compared to those from warmer climates.

}, keywords = {LTER-MCM, Antarctica, bacteriohopanepolyol, cyanobacteria, heterocyte glycolipids, homeoviscous adaptation, intact polar lipid, microbial mats}, doi = {10.3389/fmicb.2022.90362110.3389/fmicb.2022.903621.s001}, url = {https://www.frontiersin.org/articles/10.3389/fmicb.2022.903621/full}, author = {Evans, Thomas W. and Kalambokidis, Maria J. and Jungblut, Anne D. and Millar, Jasmin L. and Bauersachs, Thorsten and Grotheer, Hendrik and Mackey, Tyler J. and Ian Hawes and Summons, Roger E.} } @article {4777, title = {Long-term stream hydrology and meteorology of a polar desert, the McMurdo Dry Valleys, Antarctica}, journal = {Hydrological Processes}, volume = {36}, year = {2022}, month = {06/2022}, pages = {e14623}, abstract = {

The McMurdo Dry Valleys (MDVs; 77.50\°S, 162.25\°E) make up the largest ice-free region of Antarctica at 3500 km2. Their position near the coast of the Ross Sea provides for a milder climate than much of the rest of the continent. Alpine and piedmont glaciers in the MDVs melt during the austral summer providing water to down gradient streams and terminal lakes on valley floors. There are currently 14 meteorological stations and 17 stream gauges operating across the MDVs, some with continuous records that go back to 1969. This relatively high density of monitoring stations reflects the fact that glaciers of different sizes and elevation ranges are the main source of water to streams. Thus, each glacier represents a different watershed. The bulk of these records start in the late 1980s/early 1990s. These data collection activities directly support research endeavors of the McMurdo Dry Valleys Long Term Ecological Research project, as well as a host of other science groups working in the MDVs. As such, both real time data and archived data from these sites is available through the online database interface of the project (https://mcmlter.org).

}, keywords = {LTER-MCM, Antarctica, LTER, McMurdo Dry Valleys, meltwater streams, polar desert, research catchment}, issn = {0885-6087}, doi = {10.1002/hyp.14623}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.14623}, author = {Gooseff, Michael N. and McKnight, Diane M. and Doran, Peter T. and Fountain, Andrew} } @article {4716, title = {Photosynthetic adaptation to polar life: Energy balance, photoprotection and genetic redundancy}, journal = {Journal of Plant Physiology}, volume = {268}, year = {2022}, month = {01/2022}, pages = {153557}, abstract = {

The persistent low temperature that characterize polar habitats combined with the requirement for light for all photoautotrophs creates a conundrum. The absorption of too much light at low temperature can cause an energy imbalance that decreases photosynthetic performance that has a negative impact on growth and can affect long-term survival. The goal of this review is to survey the mechanism(s) by which polar photoautotrophs maintain cellular energy balance, that is, photostasis to overcome the potential for cellular energy imbalance in their low temperature environments. Photopsychrophiles are photosynthetic organisms that are obligately adapted to low temperature (0-15 \°C) but usually die at higher temperatures (\≥20 \°C). In contrast, photopsychrotolerant species can usually tolerate and survive a broad range of temperatures (5-40 \°C). First, we summarize the basic concepts of excess excitation energy, energy balance, photoprotection and photostasis and their importance to survival in polar habitats. Second, we compare the photoprotective mechanisms that underlie photostasis and survival in aquatic cyanobacteria and green algae as well as terrestrial Antarctic and Arctic plants. We show that polar photopsychrophilic and photopsychrotolerant organisms attain energy balance at low temperature either through a regulated reduction in the efficiency of light absorption or through enhanced capacity to consume photosynthetic electrons by the induction of O2\ as an alternative electron acceptor. Finally, we compare the published genomes of three photopsychrophilic and one photopsychrotolerant alga with five mesophilic green algae including the model green alga, Chlamydomonas reinhardtii. We relate our genomic analyses to photoprotective mechanisms that contribute to the potential attainment of photostasis. Finally, we discuss how the observed genomic redundancy in photopsychrophilic genomes may confer energy balance, photoprotection and resilience to their harsh polar environment. Primary production in aquatic, Antarctic and Arctic environments is dependent on diverse algal and cyanobacterial communities. Although mosses and lichens dominate the Antarctic terrestrial landscape, only two extant angiosperms exist in the Antarctic. The identification of a single \‘molecular key\’ to unravel adaptation of photopsychrophily and photopsychrotolerance remains elusive. Since these photoautotrophs represent excellent biomarkers to assess the impact of global warming on polar ecosystems, increased study of these polar photoautotrophs remains essential.

}, keywords = {LTER-MCM, genomic redundancy, light, photoprotection, photopsychrophily, photopsychrotolerance, Photosynthesis, temperature}, doi = {10.1016/j.jplph.2021.153557}, url = {https://www.sciencedirect.com/science/article/pii/S0176161721001966}, author = {H{\"u}ner, Norman P. A. and Smith, David R. and Cvetkovska, Marina and Zhang, Xi and Alexander G. Ivanov and Szyszka-Mroz, Beth and Kalra, Isha and Rachael M. Morgan-Kiss} } @article {4735, title = {Ten scientific messages on risks and opportunities for life in the Antarctic}, year = {2022}, month = {02/2022}, institution = {Antarctic Environments Portal}, abstract = {

Initiated by the SCAR scientific research programme \“Antarctic Thresholds \– Ecosystem Resilience and Adaptation\” (AnT-ERA, 2013-2021), 26 experts synthesized knowledge on impacts and risks of climate-change on biological processes and ecosystem functions in the Antarctic. The ten main scientific messages that emerged addressed (1) accelerating marine and terrestrial biogeochemical cycles, (2) response to ocean acidification, (3) ecological changes in climate change hot spots, (4) unexpected dynamism of marine seafloor communities, (5) biodiversity shifts, (6) low temperature limitation of protein synthesis, (7) life intrinsically linked to changing sea ice conditions, (8) pollution, (9) genetically distinct terrestrial populations under threat, and (10) newly discovered habitats. Two-thirds of the literature included in this synthesis was published between 2010 and 2020 and only one-third was published earlier. The fast mounting, recent decadal evidence indicates various Antarctic biological communities now experience climate stress, or will experience such stress in the coming decades. The responses of organisms, ecosystem functions and services to environmental changes are complex and varied. Key knowledge gaps remain and need addressing to adequately assess future prospects for life in the Antarctic.

}, keywords = {LTER-MCM}, url = {https://environments.aq/publications/ten-scientific-messages-on-risks-and-opportunities-for-life-in-the-antarctic/}, author = {Gutt, Julian and Isla, Enrique and Xavier, Jos{\'e} C. and Adams, Byron J. and Ahn, In-Young and Cheng, C.-H. Christina and Colesie, Claudia and Cummings, Vonda J. and Griffiths, Huw J. and Hogg, Ian D. and McIntyre, Trevor and Meiners, Klaus M. and Pearce, David A. and Lloyd S. Peck and Piepenburg, Dieter and Reisinger, Ryan R. and Saba, Grace and Schloss, Irene R. and Signori, Camila N. and Smith, Craig R. and Vacchi, Marino and Verde, Cinzia and Diana H. Wall} } @article {4838, title = {The time is right for an Antarctic biorepository network}, journal = {Proceedings of the National Academy of Sciences}, volume = {119}, year = {2022}, month = {12/2022}, abstract = {

Antarctica is a central driver of the Earth\’s climate and health. The Southern Ocean surrounding Antarctica serves as a major sink for anthropogenic CO2 and heat, and the loss of Antarctic ice sheets contributes significantly to sea level rise and will continue to do so as the loss of ice sheets accelerates, with sufficient water stores to raise sea levels by 58 m. Antarctica\&$\#$39;s marine environment is home to a number of iconic species, and the terrestrial realm harbors a remarkable oasis for life, much of which has yet to be discovered. Distinctive oceanographic features of the Southern Ocean\—including the Antarctic Circumpolar Current, the Antarctic Polar Front, and exceptional depths surrounding the continent\—coupled with chronically cold temperatures have fostered the evolution of a vast number of uniquely coldadapted species, many of which are found nowhere else on the Earth. The Antarctic marine biota, for example, displays the highest level of species endemism on the Earth. However, warming, ocean acidification, pollution, and commercial exploitation threaten the integrity of Antarctic ecosystems. Understanding changes in the biota and its capacities for adaptation is imperative for establishing effective policies for mitigating the impacts of climate change and sustaining the Antarctic ecosystems that are vital to global health.

}, keywords = {LTER-MCM}, issn = {0027-8424}, doi = {10.1073/pnas.2212800119}, url = {https://www.pnas.org/doi/10.1073/pnas.2212800119}, author = {O{\textquoteright}Brien, Kristin M. and Crockett, Elizabeth L. and Byron Adams and Amsler, Charles D. and Appiah-Madson, Hannah J. and Collins, Allen and Desvignes, Thomas and Detrich, H. William and Distel, Daniel L. and Eppley, Sarah M. and Frable, Benjamin W. and Franz, Nico M. and Grim, Jeffrey M. and Kocot, Kevin M. and Mahon, Andrew R. and Mayfield-Meyer, Teresa J. and Jill A. Mikucki and Moser, William E. and Schmull, Michaela and Seid, Charlotte A. and Smith, Craig R. and Todgham, Anne E. and Watkins-Colwell, Gregory J.} } @article {4823, title = {Valley-floor snowfall in Taylor Valley, Antarctica, from 1995 to 2017: Spring, summer and autumn}, journal = {Antarctic Science}, volume = {34}, year = {2022}, month = {08/2022}, pages = {325-335}, abstract = {

We present an analysis of the 20 year snowfall dataset in Taylor Valley and the results of a new snow cover monitoring study. Snowfall has been measured at four sites in Taylor Valley from 1995 to 2017. We focus on valley-floor snowfall when wind does not exceed 5 m s-1, and we exclude winter from our analysis due to poor data quality. Snowfall averaged 11 mm water equivalent (w.e.) from 1995 to 2017 across all stations and ranged from 1 to 58 mm w.e. Standard deviations ranged from 3 to 17 mm w.e., highlighting the strong interannual variability of snowfall in Taylor Valley. During spring and autumn there is a spatial gradient in snowfall such that the coast received twice as much snowfall as more central and inland stations. We identified a changepoint in 2007 from increasing snowfall (3 mm w.e. yr-1) to decreasing snowfall (1 mm w.e. yr-1), which coincides with a shift from decreasing temperature to no detectable temperature trend. Daily camera imagery from 2007 to 2017 augments the snowfall measurements. The camera imagery revealed a near tripling of the average number of days with snow cover from 37 days between 2006 and 2012 to 106 days with snow cover between 2012 and 2017.

}, keywords = {LTER-MCM, automated weather station, camera, McMurdo Dry Valleys, snow cover, snow persistence}, doi = {10.1017/S0954102022000256}, url = {https://www.cambridge.org/core/product/identifier/S0954102022000256/type/journal_article}, author = {Myers, Madeline and Peter T. Doran and Myers, Krista F.} } @article {4578, title = {Antarctic ecosystems in transition {\textendash} life between stresses and opportunities}, journal = {Biological Reviews}, year = {2021}, month = {06/2021}, abstract = {

Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key messages emerged that have stakeholder-relevance and/or a high impact for the scientific community. They address (i) altered biogeochemical cycles, (ii) ocean acidification, (iii) climate change hotspots, (iv) unexpected dynamism in seabed-dwelling populations, (v) spatial range shifts, (vi) adaptation and thermal resilience, (vii) sea ice related biological fluctuations, (viii) pollution, (ix) endangered terrestrial endemism and (x) the discovery of unknown habitats. Most Antarctic biotas are exposed to multiple stresses and considered vulnerable to environmental change due to narrow tolerance ranges, rapid change, projected circumpolar impacts, low potential for timely genetic adaptation, and migration barriers. Important ecosystem functions, such as primary production and energy transfer between trophic levels, have already changed, and biodiversity patterns have shifted. A confidence assessment of the degree of \‘scientific understanding\’ revealed an intermediate level for most of the more detailed sub-messages, indicating that process-oriented research has been successful in the past decade. Additional efforts are necessary, however, to achieve the level of robustness in scientific knowledge that is required to inform protection measures of the unique Antarctic terrestrial and marine ecosystems, and their contributions to global biodiversity and ecosystem services.

}, keywords = {LTER-MCM, adaptation, benthic dynamism, biogeochemical cycles, climate change, invasion, new habitats, ocean acidification, Primary production, range shifts, sea ice}, doi = {10.1111/brv.12679}, url = {https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12679}, author = {Gutt, Julian and Isla, Enrique and Xavier, Jos{\'e} C. and Adams, Byron J. and Ahn, In-Young and Cheng, C.-H. Christina and Colesie, Claudia and Cummings, Vonda J. and di Prisco, Guido and Griffiths, Huw J. and Ian Hawes and Hogg, Ian D. and McIntyre, Trevor and Meiners, Klaus M. and Pearce, David A. and Lloyd S. Peck and Piepenburg, Dieter and Reisinger, Ryan R. and Saba, Grace and Schloss, Irene R. and Signori, Camila N. and Smith, Craig R. and Vacchi, Marino and Verde, Cinzia and Diana H. Wall} } @article {4769, title = {Antarctica during the Pandemic: Scaled-back field season prioritizes infrastructure, precious climate data}, journal = {BioScience}, volume = {71}, year = {2021}, month = {05/2021}, pages = {434 - 440}, keywords = {LTER-MCM}, issn = {0006-3568}, doi = {10.1093/biosci/biab031}, url = {https://academic.oup.com/bioscience/article/71/5/434/6188800}, author = {Mayer, Amy} } @article {4627, title = {Connectivity: Insights from the U.S. Long Term Ecological Research Network}, journal = {Ecosphere}, volume = {12}, year = {2021}, month = {05/2021}, pages = {e03432}, abstract = {

Ecosystems across the United States are changing in complex and surprising ways. Ongoing demand for critical ecosystem services requires an understanding of the populations and communities in these ecosystems in the future. This paper represents a synthesis effort of the U.S. National Science Foundation-funded Long-Term Ecological Research (LTER) network addressing the core research area of \“populations and communities.\” The objective of this effort was to show the importance of long-term data collection and experiments for addressing the hardest questions in scientific ecology that have significant implications for environmental policy and management. Each LTER site developed at least one compelling case study about what their site could look like in 50\–100 yr as human and environmental drivers influencing specific ecosystems change. As the case studies were prepared, five themes emerged, and the studies were grouped into papers in this LTER Futures Special Feature addressing state change, connectivity, resilience, time lags, and cascading effects. This paper addresses the \“connectivity\” theme and has examples from the Phoenix (urban), Niwot Ridge (alpine tundra), McMurdo Dry Valleys (polar desert), Plum Island (coastal), Santa Barbara Coastal (coastal), and Jornada (arid grassland and shrubland) sites. Connectivity has multiple dimensions, ranging from multi-scalar interactions in space to complex interactions over time that govern the transport of materials and the distribution and movement of organisms. The case studies presented here range widely, showing how land-use legacies interact with climate to alter the structure and function of arid ecosystems and flows of resources and organisms in Antarctic polar desert, alpine, urban, and coastal marine ecosystems. Long-term ecological research demonstrates that connectivity can, in some circumstances, sustain valuable ecosystem functions, such as the persistence of foundation species and their associated biodiversity or, it can be an agent of state change, as when it increases wind and water erosion. Increased connectivity due to warming can also lead to species range expansions or contractions and the introduction of undesirable species. Continued long-term studies are essential for addressing the complexities of connectivity. The diversity of ecosystems within the LTER network is a strong platform for these studies.

}, keywords = {LTER-MCM, alpine tundra, Antarctic polar desert, arid grassland, arid shrubland, coastal, estuary, salt marsh, Special Feature: Forecasting Earth{\textquoteright}s Ecosystems with Long-Term Ecological Research, urban ecosystem}, issn = {2150-8925}, doi = {10.1002/ecs2.v12.510.1002/ecs2.3432}, url = {https://onlinelibrary.wiley.com/doi/10.1002/ecs2.3432}, author = {Iwaniec, David M. and Michael N. Gooseff and Suding, Katharine N. and Johnson, David Samuel and Reed, Daniel C. and Debra P. C. Peters and Byron Adams and John E. Barrett and Bestelmeyer, Brandon T. and Castorani, Max C. N. and Cook, Elizabeth M. and Davidson, Melissa J. and Groffman, Peter M. and Hanan, Niall P. and Huenneke, L and Johnson, Pieter T. J. and Diane M. McKnight and Miller, Robert J. and Okin, Gregory S. and Preston, Daniel L. and Rassweiler, Andrew and Ray, Chris and Osvaldo E. Sala and Schooley, Robert and Seastedt, Timothy and Spasojevic, Marko J. and Vivoni, Enrique R.} } @mastersthesis {4762, title = {Controls on microbial mat coverage and diatom species turnover in Antarctic desert streams: A transplant experiment}, volume = {M.S.}, year = {2021}, school = {University of Colorado Boulder}, type = {masters}, address = {Boulder, CO}, abstract = {

This thesis evaluates how polar desert streams regulate benthic microbial mat coverage, chlorophyll-a biomass, and diatom species composition. Microbial mats growing on rocks (eplithon) and on sandy substrate (epipelon) were reciprocally transplanted among four glaciers meltwater streams and monitored through time. The selected study streams were Green Creek, Bowles Creek, Delta Stream, Von Guerard Stream in the Lake Fryxell Basin in the McMurdo Dry Valleys, Antarctica. These streams vary in length, streamflow intermittency, and diatom community composition of microbial mats. Results demonstrate that streams strongly control mat biomass (coverage and chlorophyll-a) differently for epilithon and epipelon. However, diatom species composition did not vary between these growth habitats but instead varied by stream, suggesting adaptive niche separation related to environmental conditions. Diatom species composition of transplants in Green Creek became dissimilar from their initial stream communities suggesting downstream dispersal and within stream connectivity regulates community assembly. This experiment confirms that environmental characteristics and intra-stream dispersal processes exert strong control over maintaining microbial mat coverage, biomass accrual, and diatom species composition.

}, keywords = {LTER-MCM, Antarctica, diatom, microbial mat, streams, transplant, turnover}, url = {https://www.proquest.com/docview/2634590982}, author = {Darling, Joshua P.}, editor = {Diane M. McKnight} } @article {4586, title = {Diatoms in hyporheic sediments trace organic matter retention and processing in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {02/2021}, pages = {e2020JG006097}, abstract = {

In low-nutrient streams in cold and arid ecosystems, the spiraling of autochthonous particulate organic matter (POM) may provide important nutrient subsidies downstream. Because of its lability and the spatial heterogeneity of processing in hyporheic sediments, the downstream transport and fate of autochthonous POM can be difficult to trace. In Antarctic McMurdo Dry Valley (MDV) streams, any POM retained in the hyporheic zone is expected to be derived from surface microbial mats that contain diatoms with long-lasting silica frustules. We tested whether diatom frustules can be used to trace the retention of autochthonous POM in the hyporheic zone and whether certain geomorphic locations promote this process. The accumulation of diatom frustules in hyporheic sediments, measured as biogenic silica, was correlated with loss-on-ignition organic matter and sorbed ammonium, suggesting that diatoms can be used to identify locations where POM has been retained and processed over long timescales, regardless of whether the POM remains intact. In addition, by modeling the upstream sources of hyporheic diatom assemblages, we found that POM was predominantly derived from N-fixing microbial mats of the genus Nostoc. In terms of spatial variability, we conclude that the hyporheic sediments adjacent to the stream channel that are regularly inundated by daily flood pulses are where the most POM has been retained over long timescales. Autochthonous POM is retained in hyporheic zones of low-nutrient streams beyond the MDVs, and we suggest that biogenic silica and diatom composition can be used to identify locations where this transfer is most prevalent.

}, keywords = {LTER-MCM, benthic processes, biogenic silica, biogeochemical cycles processes and modeling, carbon cycling, diatoms, groundwater/surface water interactions, hyporheic zone, McMurdo Dry Valleys, nitrogen cycling, particulate organic matter}, doi = {10.1029/2020JG006097}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG006097}, author = {Heindel, Ruth C and Darling, Joshua P. and Singley, Joel G. and Bergstrom, Anna J. and Diane M. McKnight and Lukkari, Braeden M. and Kathleen A. Welch and Michael N. Gooseff} } @article {4634, title = {Draft genome sequence of the Antarctic green alga Chlamydomonas sp. UWO241}, journal = {iScience}, volume = {24}, year = {2021}, month = {2021-02}, pages = {102084}, abstract = {

Antarctica is home to an assortment of psychrophilic algae, which have evolved various survival strategies for coping with their frigid environments. Here, we explore Antarctic psychrophily by examining the \∼212 Mb draft nuclear genome of the green alga Chlamydomonas\ sp. UWO241, which resides within the water column of a perennially ice-covered, hypersaline lake. Like certain other Antarctic algae, UWO241 encodes a large number (\≥37) of ice-binding proteins, putatively originating from horizontal gene transfer. Even more striking, UWO241 harbors hundreds of highly similar duplicated genes involved in diverse cellular processes, some of which we argue are aiding its survival in the Antarctic via gene dosage. Gene and partial gene duplication appear to be an ongoing phenomenon within UWO241, one which might be mediated by retrotransposons. Ultimately, we consider how such a process could be associated with adaptation to extreme environments but explore potential non-adaptive hypotheses as well.

}, keywords = {LTER-MCM}, issn = {25890042}, doi = {10.1016/j.isci.2021.102084}, url = {https://www.sciencedirect.com/science/article/pii/S2589004221000523}, author = {Zhang, Xi and Cvetkovska, Marina and Rachael M. Morgan-Kiss and H{\"u}ner, Norman P. A. and Smith, David Roy} } @article {4644, title = {From the Heroic Age to today: What diatoms from Shackleton{\textquoteright}s Nimrod expedition can tell us about the ecological trajectory of Antarctic ponds}, journal = {Limnology and Oceanography Letters}, year = {2021}, month = {07/2021}, abstract = {

Biological invasion and environmental change pose major threats to ecosystems. While long-term ecological change is commonly evaluated through sediment cores in lakes, it is generally not feasible for smaller ponds, and spatial resolution is limited. Here, we analyze pond diatom communities collected during Shackleton\&$\#$39;s Nimrod expedition at Cape Royds, Antarctica, to compare with the same waterbodies a century later. We find historical samples to be almost identical to modern counterparts, and provide no evidence of exotic introductions despite increasing human activity. However, a shift occurred in the pond nearest Shackleton\&$\#$39;s hut, Pony Lake, which was dominated by Luticola muticopsis a century ago, and was replaced by Craspedostauros laevissimus. Both are endemic species previously and currently present at Cape Royds, and we hypothesize that a shift in conductivity accompanying changing precipitation patterns may be responsible. Collectively, these results provide important data for assessing human and climate impacts among Antarctic lacustrine habitats.

}, keywords = {LTER-MCM}, issn = {2378-2242}, doi = {10.1002/lol2.10200}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/10.1002/lol2.10200}, author = {Tyler J. Kohler and Howkins, Adrian and Eric R. Sokol and Kopalov{\'a}, Kate{\v r}ina and Cox, Aneliya and Darling, Joshua P. and Michael N. Gooseff and Diane M. McKnight} } @article {4577, title = {Geochemistry of contrasting stream types, Taylor Valley, Antarctica}, journal = {GSA Bulletin}, volume = {133}, year = {2021}, month = {01/2021}, pages = {425-448}, abstract = {

The McMurdo Dry Valley region is the largest ice-free area of Antarctica. Ephemeral streams flow here during the austral summer, transporting glacial meltwater to perennially ice-covered, closed basin lakes. The chemistry of 24 Taylor Valley streams was examined over the two-decade period of monitoring from 1993 to 2014, and the geochemical behavior of two streams of contrasting physical and biological character was monitored across the seven weeks of the 2010\–2011 flow season. Four species dominate stream solute budgets: HCO3\–, Ca2+, Na+, and Cl\–, with SO42\–, Mg2+, and K+ present in significantly lesser proportions. All streams contain dissolved silica at low concentrations. Across Taylor Valley, streams are characterized by their consistent anionic geochemical fingerprint of HCO3 \> Cl \> SO4, but there is a split in cation composition between 14 streams with Ca \> Na \> Mg \> K and 10 streams with Na \> Ca \> Mg \> K.


Andersen Creek is a first-order proglacial stream representative of the 13 short streams that flow \<1.5 km from source to gage. Von Guerard is representative of 11 long streams 2\–7 km in length characterized by extensive hyporheic zones. Both streams exhibit a strong daily cycle for solute load, temperature, dissolved oxygen, and pH, which vary in proportion to discharge. A well-expressed diurnal co-variation of pH with dissolved oxygen is observed for both streams that reflects different types of biological control. The relative consistency of Von Guerard composition over the summer flow season reflects chemostatic regulation, where water in transient storage introduced during times of high streamflow has an extended opportunity for water-sediment interaction, silicate mineral dissolution, and pore-water exchange.

}, keywords = {LTER-MCM}, doi = {10.1130/B35479.1}, url = {https://pubs.geoscienceworld.org/gsa/gsabulletin/article/133/1-2/425/587799/Geochemistry-of-contrasting-stream-types-Taylor}, author = {Harmon, Russell S. and Leslie, Deborah L. and W. Berry Lyons and Kathleen A. Welch and Diane M. McKnight} } @article {4732, title = {The magnitude and climate sensitivity of isotopic fractionation from ablation of Antarctic Dry Valley lakes}, journal = {Arctic, Antarctic, and Alpine Research}, volume = {53}, year = {2021}, month = {12/2021}, pages = {352 - 371}, abstract = {

There has been extensive research on the effects of evaporation on the isotopic ratio of lacustrine and marine water bodies; however, there are limited data on how ablation or sublimation from lake or sea ice influences the isotopic ratio of the residual water body. This is a challenging problem because there remains uncertainty on the magnitude of fractionation during sublimation and because ablation can involve mixed-phase processes associated with simultaneous sublimation, melting, evaporation, and refreezing. This uncertainty limits the ability to draw quantitative inferences on changing hydrological budgets from stable isotope records in arctic, Antarctic, and alpine lakes. Here, we use in situ measurements of the isotopic ratio of water vapor along with the gradient diffusion method to constrain the isotopic ratio of the ablating ice from two lakes in the McMurdo Dry Valleys, Antarctica. We find that during austral summer, the isotopic fractionation of ablation was insignificant during periods of boundary layer instability that are typical during midday when latent heat is highest. This implies that the loss of mass during these periods did not yield any isotopic enrichment to the residual lake mass. However, fractionation increased after midday when the boundary layer stabilized and the latent heat flux was small. This diurnal pattern was mirrored on synoptic timescales, when following warm and stable conditions latent heat flux was low and dominated by higher fractionation for a few days. We hypothesize that the shifting from negligible to large isotopic fractionation reflects the development and subsequent exhaustion of liquid water on the surface. The results illustrate the complex and nonlinear controls on isotopic fractionation from icy lakes, which implies that the isotopic enrichment from ablation could vary significantly over timescales relevant for changing lake volumes. Future work using water isotope fluxes for longer periods of time and over additional perennial and seasonal ice-covered lake systems is critical for developing models of the isotopic mass balance of arctic and Antarctic lake systems.

}, keywords = {LTER-MCM, Dry Valley lakes, isotope fractionation, stable water isotopes}, issn = {1523-0430}, doi = {10.1080/15230430.2021.2001899}, url = {https://www.tandfonline.com/doi/full/10.1080/15230430.2021.2001899}, author = {Bellagamba, Anthony W. and Berkelhammer, Max and Winslow, Luke A. and Peter T. Doran and Myers, Krista F. and Devlin, Shawn and Ian Hawes} } @article {4690, title = {Meta-analysis of Cryogenian through modern quartz microtextures reveals sediment transport histories}, journal = {Journal of Sedimentary Research}, volume = {91}, year = {2021}, month = {09/2021}, pages = {929-944}, abstract = {

Quantitative analysis of quartz microtextures by means of scanning electron microscopy (SEM) can reveal the transport histories of modern and ancient sediments. However, because workers identify and count microtextures differently, it is difficult to directly compare quantitative microtextural data analyzed by different workers. As a result, the defining microtextures of certain transport modes and their probabilities of occurrence are not well constrained. We used principal-component analysis (PCA) to directly compare modern and ancient aeolian, fluvial, and glacial samples from the literature with nine new samples from active aeolian and glacial environments. Our results demonstrate that PCA can group microtextural samples by transport mode and differentiate between aeolian transport and fluvial and glacial transport across studies. The PCA ordination indicates that aeolian samples are distinct from fluvial and glacial samples, which are in turn difficult to disambiguate from each other. Ancient and modern sediments are also shown to have quantitatively similar microtextural relationships. Therefore, PCA may be a useful tool to constrain the ambiguous transport histories of some ancient sediment grains. As a case study, we analyzed two samples with ambiguous transport histories from the Cryogenian Br{\r a}vika Member (Svalbard). Integrating PCA with field observations, we find evidence that the Br{\r a}vika Member facies investigated here includes aeolian deposition and may be analogous to syn-glacial Marinoan aeolian units including the Bakoye Formation in Mali and the Whyalla Sandstone in South Australia.

}, keywords = {LTER-MCM}, issn = {1527-1404}, doi = {10.2110/jsr.2020.151}, url = {https://pubs.geoscienceworld.org/jsedres/article/91/9/929/607764/Meta-analysis-of-Cryogenian-through-modern-quartz}, author = {Reahl, Jocelyn N. and Cantine, Marjorie D. and Wilcots, Julia and Mackey, Tyler J. and Bergmann, Kristin D.} } @article {4597, title = {Metabolic capacity of the Antarctic cyanobacterium Phormidium pseudopriestleyi that sustains oxygenic photosynthesis in the presence of hydrogen sulfide}, journal = {Genes}, volume = {12}, year = {2021}, month = {03/2021}, pages = {426}, abstract = {

Sulfide inhibits oxygenic photosynthesis by blocking electron transfer between H2O and the oxygen-evolving complex in the D1 protein of Photosystem II. The ability of cyanobacteria to counter this effect has implications for understanding the productivity of benthic microbial mats in sulfidic environments throughout Earth history. In Lake Fryxell, Antarctica, the benthic, filamentous cyanobacterium Phormidium pseudopriestleyi creates a 1\–2 mm thick layer of 50 \µmol L\−1 O2 in otherwise sulfidic water, demonstrating that it sustains oxygenic photosynthesis in the presence of sulfide. A metagenome-assembled genome of P. pseudopriestleyi indicates a genetic capacity for oxygenic photosynthesis, including multiple copies of psbA (encoding the D1 protein of Photosystem II), and anoxygenic photosynthesis with a copy of sqr (encoding the sulfide quinone reductase protein that oxidizes sulfide). The genomic content of P. pseudopriestleyi is consistent with sulfide tolerance mechanisms including increasing psbA expression or directly oxidizing sulfide with sulfide quinone reductase. However, the ability of the organism to reduce Photosystem I via sulfide quinone reductase while Photosystem II is sulfide-inhibited, thereby performing anoxygenic photosynthesis in the presence of sulfide, has yet to be demonstrated.\ 

}, keywords = {LTER-MCM}, doi = {10.3390/genes12030426}, url = {https://www.mdpi.com/2073-4425/12/3/426}, author = {Lumian, Jessica E. and Jungblut, Anne D. and Dillon, Megan L. and Hawes, Ian and Peter T. Doran and Mackey, Tyler J. and Dick, Gregory J. and Grettenberger, Christen L. and Sumner, Dawn Y.} } @article {4715, title = {Research sites get closer to field camps over time: Informing environmental management through a geospatial analysis of science in the McMurdo Dry Valleys, Antarctica}, journal = {PLOS ONE}, volume = {16}, year = {2021}, month = {11/2021}, pages = {e0257950}, abstract = {

As in many parts of the world, the management of environmental science research in Antarctica relies on cost-benefit analysis of negative environmental impact versus positive scientific gain. Several studies have examined the environmental impact of Antarctic field camps, but very little work looks at how the placement of these camps influences scientific research. In this study, we integrate bibliometrics, geospatial analysis, and historical research to understand the relationship between field camp placement and scientific production in the McMurdo Dry Valleys of East Antarctica. Our analysis of the scientific corpus from 1907\–2016 shows that, on average, research sites have become less dispersed and closer to field camps over time. Scientific output does not necessarily correspond to the number of field camps, and constructing a field camp does not always lead to a subsequent increase in research in the local area. Our results underscore the need to consider the complex historical and spatial relationships between field camps and research sites in environmental management decision-making in Antarctica and other protected areas.

}, keywords = {LTER-MCM}, doi = {10.1371/journal.pone.0257950}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0257950}, author = {Chignell, Stephen M. and Myers, Madeline and Howkins, Adrian and Andrew G Fountain} } @phdthesis {4678, title = {Role of cyclic electron flow (CEF) and photosystem I (PSI) supercomplex formation during acclimation to long-term salinity stress in green algae: A comparative study}, volume = {PhD}, year = {2021}, month = {2021}, pages = {236}, school = {Miami University}, type = {Doctoral}, address = {Oxford, OH}, abstract = {Photosynthesis is one of the most important processes on Earth by which organisms convert solar energy into usable forms of energy. Linear electron flow (LEF) and cyclic electron flow (CEF) constitute two major pathways in photosynthesis. While LEF leads to production of both ATP and NADPH, CEF only produces ATP that helps balance the ATP:NADPH ratio required for carbon fixation. CEF also plays a major role during acclimation to several environmental stressors. However, the regulation and mechanism by which CEF operates is still not clearly understood. Recent studies have shown that formation of a protein supercomplex with PSI appears to be essential for induction of CEF in several model organisms. However, both supercomplex formation and CEF induction have been mainly studied under short-term, transitory stress conditions. In addition, the role and mechanism by which organisms may rely on CEF to survive in their natural habitat and acclimate to stress over a long period of time has not been considered. In this study we compared how three photosynthetic organisms (one model alga, Chlamydomonas reinhardtii; two extremophiles, C. sp. UWO241 and C. sp. ICE-MDV) utilize CEF to cope with their natural environment and adapt to steady-state environmental stress. To that end, the objectives of this thesis were i) to elucidate the role of CEF in long-term salinity acclimation ii) to understand the downstream changes associated with increased CEF, and iii) to identify whether PSI-supercomplexes are associated with increased CEF during salinity acclimation. We hypothesized that a stable PSI-supercomplex is required for high CEF, which in turn supports strong carbon fixation capacity for production of downstream metabolic products important for long-term acclimation to salinity stress. We showed for the first time, that increased CEF in UWO241 leads to excess ATP production and rewiring of downstream metabolism under high salinity. Next, we showed that a laboratory evolved salinity-tolerant strain of model C. reinhardtii uses constitutive upregulation of CEF to deal with salinity stress, which is in-turn associated with increased non-photochemical quenching and rewired carbon metabolism. Last, we show that CEF is involved in salinity acclimation in all three Chlamydomonas species, regardless of their salinity tolerance. We also show that PSI-supercomplexes are associated with increased CEF in these species. Characterization of high-salt supercomplex of C. reinhardtii revealed that it shares many similarities with the extensively described state 2 supercomplex, and that supercomplex composition might be species dependent rather than stress dependent.}, keywords = {LTER-MCM, acclimation, CEF, extremophile, Photosynthesis, salinity stress, supercomplex}, url = {https://www.proquest.com/docview/2572560585}, author = {Kalra, Isha}, editor = {Rachael M. Morgan-Kiss} } @article {4626, title = {The role of hyporheic connectivity in determining nitrogen availability: Insights from an intermittent Antarctic stream}, journal = {Journal of Geophysical Research: Biogeosciences}, year = {2021}, month = {04/2022}, abstract = {

Due to widespread manipulation of nitrogen (N), much research has focused on processes controlling the fate of anthropogenic N in streams. Yet, in a variety of oligotrophic systems, N fixed by periphyton is a significant driver of ecosystem metabolism. Due to difficulties partitioning allochthonous and autochthonous sources, there is limited information regarding how the latter is processed. Autochthonous N may be particularly important in alpine, arid, or polar environments. We test the hypothesis that the availability of remineralized autochthonous N is controlled by connectivity between the hyporheic zone and main channel due to the contrasting biogeochemical functions of benthic autotrophs (including N-fixing Nostoc) and hyporheic heterotrophs in an intermittent Antarctic stream. There, we collected surface water and hyporheic water concurrently at 4-6 hour intervals over a 32.5-hr period during one flow season and opportunistically throughout a second. Hyporheic water had 7 to 30 times greater nitrate-N concentrations relative to surface water across all flow conditions. In contrast, ammonium concentrations were generally lower, although similar among locations. Additionally, nitrate in hyporheic water was positively correlated with silica, an indicator of hyporheic residence time. A laboratory assay confirmed prior inferences that hyporheic microbial communities possess the functional potential to perform nitrification. Together, these findings suggest that remineralized autochthonous N accumulates in the hyporheic zone even as streamflow varies and likely subsidizes stream N availability\—which supports prior inferences from N stable isotope data at this site. These results highlight the importance of hyporheic connectivity in controlling autochthonous N cycling and availability in streams.

}, keywords = {LTER-MCM, Antarctica, autochthonous nitrogen, hyporheic zone, nitrogen cycling, streamflow}, issn = {2169-8953}, doi = {10.1029/2021JG006309}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JG006309}, author = {Singley, Joel G. and Gooseff, Michael N. and Diane M. McKnight and Eve-Lyn S. Hinckley} } @article {4648, title = {Supporting simultaneous air revitalization and thermal control in a crewed habitat with temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta}, journal = {Frontiers in Microbiology}, volume = {12}, year = {2021}, month = {08/2021}, pages = {709746}, abstract = {

Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station (C. vulgaris, 9\–27\°C; Chlorophyta-Ant, 4\–14\°C) and included a constant temperature control (10\°C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates (C. vulgaris; initial: 0.013 mgO2 L-1, final: 3.15 mgO2 L\–1 and Chlorophyta-Ant; initial: 0.653 mgO2 L\–1, final: 1.03 mgO2 L\–1) and culture growth, suggesting environmental acclimation. Antarctic sample conditions exhibited increases or sustainment of oxygen production rates normalized by biomass dry weight, while both C. vulgaris sample conditions decreased oxygen production per biomass. However, even with the temperature-induced reduction, cycled temperature C. vulgaris had a significantly higher normalized oxygen production rate than Antarctic Chlorophyta. Chlorophyll fluorometry measurements showed that the cycled temperature conditions did not overly stress both sample types (FV/FM: 0.6\–0.75), but the Antarctic Chlorophyta sample had significantly higher fluorometry readings than its C. vulgaris counterpart (F = 6.26, P \< 0.05). The steady state C. vulgaris condition had significantly lower fluorometry readings than all other conditions (FV/FM: 0.34), suggesting a stressed culture. This study compares the results to similar experiments conducted in steady state or diurnally cycled temperature conditions. Recommendations for surface system implementation are based off the presented results. The preliminary findings imply that both C. vulgaris and Antarctic Chlorophyta can withstand the dynamic temperature environment reflective of a thermal control loop and these data can be used for future design models.

}, keywords = {LTER-MCM, air revitalization, Antarctica, bioregenerative life support systems, Chlorophyta, McMurdo Dry Valleys, thermal control}, doi = {10.3389/fmicb.2021.709746}, url = {https://www.frontiersin.org/article/10.3389/fmicb.2021.709746}, author = {Matula, Emily E. and Nabity, James A. and Diane M. McKnight} } @article {4647, title = {Thermal legacy of a large paleolake in Taylor Valley, East Antarctica, as evidenced by an airborne electromagnetic survey}, journal = {The Cryosphere}, volume = {15}, year = {2021}, month = {08/2021}, pages = {3577 - 3593}, abstract = {

Previous studies of the lakes of the McMurdo Dry Valleys have attempted to constrain lake level history, and results suggest the lakes have undergone hundreds of meters of lake level change within the last 20 000 years. Past studies have utilized the interpretation of geologic deposits, lake chemistry, and ice sheet history to deduce lake level history; however a substantial amount of disagreement remains between the findings, indicating a need for further investigation using new techniques. This study utilizes a regional airborne resistivity survey to provide novel insight into the paleohydrology of the region. Mean resistivity maps revealed an extensive brine beneath the Lake Fryxell basin, which is interpreted as a legacy groundwater signal from higher lake levels in the past. Resistivity data suggest that active permafrost formation has been ongoing since the onset of lake drainage and that as recently as 1500\–4000 years BP, lake levels were over 60 m higher than present. This coincides with a warmer-than-modern paleoclimate throughout the Holocene inferred by the nearby Taylor Dome ice core record. Our results indicate Mid to Late Holocene lake level high stands, which runs counter to previous research finding a colder and drier era with little hydrologic activity throughout the last 5000 years.

}, keywords = {LTER-MCM}, doi = {10.5194/tc-15-3577-2021}, url = {https://tc.copernicus.org/articles/15/3577/2021/}, author = {Myers, Krista F. and Peter T. Doran and Tulaczyk, Slawek M. and Foley, Neil T. and Bording, Thue S. and Auken, Esben and Hilary A. Dugan and Jill A. Mikucki and Foged, Nikolaj and Grombacher, Denys and Ross A. Virginia} } @article {4613, title = {Year-round and long-term phytoplankton dynamics in Lake Bonney, a permanently ice-covered Antarctic lake}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {04/2021}, pages = {e2020JG005925}, abstract = {

Lake Bonney (McMurdo Dry Valleys, east Antarctica) represents a year-round refugium for life adapted to permanent extreme conditions. Despite intensive research since the 1960s, due to the logistical constraints posed by 4-months of 24-h darkness, knowledge of how the resident photosynthetic microorganisms respond to the polar winter is limited. In addition, the lake level has risen by more than 3 m since 2004: impacts of rapid lake level rise on phytoplankton community structure is also poorly understood. From 2004 to 2015 an in situ submersible spectrofluorometer (bbe FluoroProbe) was deployed in Lake Bonney during the austral summer to quantify the vertical structure of four functional algal groups (green algae, mixed algae, and cryptophytes, cyanobacteria). During the 2013\–2014 field season the Fluoroprobe was mounted on autonomous cable-crawling profilers deployed in both the east and west lobes of Lake Bonney, obtaining the first daily phytoplankton profiles through the polar night. Our findings showed that phytoplankton communities were differentially impacted by physical and chemical factors over long-term versus seasonal time scales. Following a summer of rapid lake level rise (2010\–2011), an increase in depth integrated chlorophyll a (chl-a) occurred in Lake Bonney caused by stimulation of photoautotrophic green algae. Conversely, peaks in chl-a during the polar night were associated with an increase in mixotrophic haptophytes and cryptophytes. Collectively our data reveal that phytoplankton groups possessing variable trophic abilities are differentially competitive during seasonal and long-term time scales owing to periods of higher nutrients (photoautotrophs) versus light/energy limitation (mixotrophs).

}, keywords = {LTER-MCM, algae, Antarctic, fluorometry, ice, lakes, light, profiling, winter}, issn = {2169-8953}, doi = {10.1029/2020JG005925}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG005925}, author = {Patriarche, Jeffrey D. and John C. Priscu and Cristina D. Takacs-Vesbach and Winslow, Luke A. and Myers, Krista F. and Heather N. Buelow and Rachael M. Morgan-Kiss and Peter T. Doran} } @proceedings {4575, title = {Change in Pictures: Creating best practices in archiving ecological imagery for reuse}, journal = {Biodiversity Information Science and Standards}, volume = {4}, year = {2020}, month = {09/2020}, abstract = {

The research data repository of the Environmental Data Initiative (EDI) is building on over 30 years of data curation research and experience in the National Science Foundation-funded US Long-Term Ecological Research (LTER) Network. It provides mature functionalities, well established workflows, and now publishes all \‘long-tail\’ environmental data. High quality scientific metadata are enforced through automatic checks against community developed rules and the Ecological Metadata Language (EML) standard. Although the EDI repository is far along in making its data findable, accessible, interoperable, and reusable (FAIR), representatives from EDI and the LTER are developing best practices for the edge cases in environmental data publishing. One of these is the vast amount of imagery taken in the context of ecological research, ranging from wildlife camera traps to plankton imaging systems to aerial photography. Many images are used in biodiversity research for community analyses (e.g., individual counts, species cover, biovolume, productivity), while others are taken to study animal behavior and landscape-level change.

Some examples from the LTER Network include: using photos of a heron colony to measure provisioning rates for chicks (Clarkson and Erwin 2018) or identifying changes in plant cover and functional type through time (Peters et al. 2020). Multi-spectral images are employed to identify prairie species. Underwater photo quads are used to monitor changes in benthic biodiversity (Edmunds 2015). Sosik et al. (2020) used a continuous Imaging FlowCytobot to identify and measure phyto- and microzooplankton. Cameras at McMurdo Dry Valleys assess snow and ice cover on Antarctic lakes allowing estimation of primary production (Myers 2019).

It has been standard practice to publish numerical data extracted from images in EDI; however, the supporting imagery generally has not been made publicly available. Our goal in developing best practices for documenting and archiving these images is for them to be discovered and re-used. Our examples demonstrate several issues. The research questions, and hence, the image subjects are variable. Images frequently come in logical sets of time series. The size of such sets can be large and only some images may be contributed to a dedicated specialized repository. Finally, these images are taken in a larger monitoring context where many other environmental data are collected at the same time and location.

Currently, a typical approach to publishing image data in EDI are packages containing compressed (ZIP or tar) files with the images, a directory manifest with additional image-specific metadata, and a package-level EML metadata file. Images in the compressed archive may be organized within directories with filenames corresponding to treatments, locations, time periods, individuals, or other grouping attributes. Additionally, the directory manifest table has columns for each attribute. Package-level metadata include standard coverage elements (e.g., date, time, location) and sampling methods. This approach of archiving logical \‘sets\’ of images reduces the effort of providing metadata for each image when most information would be repeated, but at the expense of not making every image individually searchable. The latter may be overcome if the provided manifest contains standard metadata that would allow searching and automatic integration with other images.

}, keywords = {LTER-MCM, data repository, ecological data, metadata}, doi = {10.3897/biss.4.59082}, url = {https://biss.pensoft.net/article/59082/}, author = {Gries, Corinna and Beaulieu, Stace and Brown, Ren{\'e}e F. and Gastil-Buhl, Gastil and Elmendorf, Sarah C. and Hsieh, Hsun-Yi and Kui, Li and Maurer, Greg and Porter, John H.} } @phdthesis {4587, title = {Characterization of spatial and environmental influences on stream diatoms and cyanobacteria}, volume = {Ph.D.}, year = {2020}, month = {2020}, school = {University of Colorado Boulder}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Primary producing algae form the basis of carbon fixation, oxygen production, and food webs in aquatic ecosystems globally. However, human activities disrupt climate and freshwater physicochemistry. These impacts alter the health of algal communities and the ecosystem services algae provide. Meanwhile, spatial processes like dispersal and landscape characteristics like geology also influence algal structure and function. Diatoms are indicators of stream health and are model organisms for understanding the processes underlying microbial biogeography. Benthic cyanobacteria present risks to human health through the proliferation of toxin-producing blooms. With this dissertation, I investigate the ecosystem processes that influence diatom and cyanobacterial community composition and taxon distributions. My goal is to advance the understanding of ecosystem controls on algal biogeography and to characterize taxon-specific autecology for use in environmental management. First, I measured the extent of wind-mediated dispersal of benthic diatoms across aquatic habitats to better understand how community composition is structured by spatial processes across the McMurdo Dry Valleys polar desert in Antarctica. I found that inter-habitat dispersal is common but less influential on community composition than intra-habitat factors such as environmental conditions. I then used non-linear, multivariable modeling to assess the relative influences of climate, watershed characteristics, and in-stream stressors on the relative abundances of 268 diatom taxa across gradients of human impact in the northeast United States. My results indicate diatom taxa are affected by different suites of environmental conditions but that taxa belong to ecological guilds based on shared responsiveness to environmental factors. Finally, I applied multivariable modeling towards understanding the effects of aquatic stressors, including herbicides and persistent organic pollutants, on the distributions of benthic cyanobacteria across northeast U.S. streams. I found that watershed characteristics, streamflow, and herbicides were more influential than light availability, water temperature, and nutrients on the distributions of potentially toxigenic cyanobacterial genera. Collectively, this research expands the knowledge of how benthic algal communities and taxon distributions are structured at large spatial scales along gradients of unimpacted and human-altered environmental conditions. I provide a novel modeling framework and taxon-specific autecological information that can be applied to environmental assessments of stream health and future algal research.

}, keywords = {LTER-MCM, algae, dispersal, environmental assessment, human disturbance, metacommunity ecology, species distribution models}, url = {https://www.proquest.com/docview/2476216263}, author = {Schulte, Nicholas O. and Diane M. McKnight} } @article {4419, title = {Chlamydomonas sp. UWO 241 exhibits high cyclic electron flow and rewired metabolism under high salinity}, journal = {Plant Physiology}, year = {2020}, month = {03/2020}, abstract = {

The Antarctic green alga Chlamydomonas sp. UWO 241 (UWO 241) is adapted to permanent low temperatures, hypersalinity, and extreme shade. one of the most striking phenotypes of UWO 241 is an altered photosystem I (PSI) organization and constitutive PSI cyclic electron flow (CEF). To date, little attention has been paid to CEF during long-term stress acclimation, and the consequences of sustained CEF in UWO 241 are not known. In this study, we combined photobiology, proteomics, and metabolomics to understand the underlying role of sustained CEF in high salinity stress acclimation. High salt-grown UWO 241 exhibited increased thylakoid proton motive flux and an increased capacity for non-photochemical quenching. Under high salt, a significant proportion of the upregulated enzymes were associated with the Calvin Benson Bassham Cycle, carbon storage metabolism, and protein translation. Two key enzymes of the Shikimate pathway, DAHP synthase and chorismate synthase, were also upregulated, as well as indole-3-glycerol phosphate synthase, an enzyme involved in the biosynthesis of L-tryptophan and indole acetic acid. In addition, several compatible solutes (glycerol, proline, and sucrose) accumulated to high levels in high salt-grown UWO 241 cultures. We suggest that UWO 241 maintains constitutively high CEF through the associated PSI-cytochrome b6f supercomplex to support robust growth and strong photosynthetic capacity under a constant growth regime of low temperatures and high salinity.

}, keywords = {LTER-MCM}, doi = {10.1104/pp.19.01280}, url = {http://www.plantphysiol.org/content/early/2020/04/03/pp.19.01280}, author = {Kalra, Isha and Wang, Xin and Cvetkovska, Marina and Jeong, Jooyeon and McHargue, William and Zhang, Ru and H{\"u}ner, Norman and Yuan, Joshua S. and Rachael M. Morgan-Kiss} } @article {4448, title = {Climate from the McMurdo Dry Valleys, Antarctica, 1986 {\textendash} 2017: Surface air temperature trends and redefined summer season}, journal = {Journal of Geophysical Research: Atmospheres}, year = {2020}, month = {05/2020}, abstract = {

The weather of the McMurdo Dry Valleys, Antarctica, the largest ice-free region of the Antarctica, has been continuously monitored since 1985 with currently 14 operational meteorological stations distributed throughout the valleys. Because climate is based on a 30-year record of weather, this is the first study to truly define the contemporary climate of the McMurdo Dry Valleys. Mean air temperature and solar radiation based on all stations were -20\°C and 102 W m-2, respectively. Depending on the site location, the mean annual air temperatures on the valleys floors ranged between -15\°C and -30\°C, and mean annual solar radiation varied between 72 W m-2 and 122 W m-2. Surface air temperature decreased by 0.7\°C per decade from 1986 to 2006 at Lake Hoare station (longest continuous record), after which the record is highly variable with no trend. All stations with sufficiently long records showed similar trend shifts in 2005 \±1 year. Summer is defined as November through February, using a physically based process: up-valley warming from the coast associated with a change in atmospheric stability.

}, keywords = {LTER-MCM, McMurdo Dry Valleys, summer season, weather observations}, doi = {10.1029/2019JD032180}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JD032180}, author = {Obryk, M. K. and Doran, P. T. and Fountain, A. G. and Myers, M. and McKay, C. P.} } @article {4395, title = {Energetic and environmental constraints on the community structure of benthic microbial mats in Lake Fryxell, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {96}, year = {2020}, month = {02/2020}, abstract = {

Ecological communities are regulated by the flow of energy through environments. Energy flow is typically limited by access to photosynthetically active radiation (PAR) and oxygen concentration (O2). The microbial mats growing on the bottom of Lake Fryxell, Antarctica, have well-defined environmental gradients in PAR and (O2). We analyzed the metagenomes of layers from these microbial mats to test the extent to which access to oxygen and light controls community structure. We found variation in the diversity and relative abundances of Archaea, Bacteria and Eukaryotes across three (O2) and PAR conditions: high (O2) and maximum PAR, variable (O2) with lower maximum PAR, and low (O2) and maximum PAR. We found distinct communities structured by the optimization of energy use on a millimeter-scale across these conditions. In mat layers where (O2) was saturated, PAR structured the community. In contrast, (O2) positively correlated with diversity and affected the distribution of dominant populations across the three habitats, suggesting that meter-scale diversity is structured by energy availability. Microbial communities changed across covarying gradients of PAR and (O2). The comprehensive metagenomic analysis suggests that the benthic microbial communities in Lake Fryxell are structured by energy flow across both meter- and millimeter-scales.

}, keywords = {LTER-MCM, Antarctica, energy, Lake Fryxell, microbial mat, Oxygen, Photosynthetically Active Radiation}, doi = {10.1093/femsec/fiz207}, url = {https://academic.oup.com/femsec/article/96/2/fiz207/5697196}, author = {Dillon, Megan L. and Ian Hawes and Jungblut, Anne D. and Mackey, Tyler J. and Eisen, Jonathan A. and Peter T. Doran and Sumner, Dawn Y.} } @article {4582, title = {Environmental control on the distribution of metabolic strategies of benthic microbial mats in Lake Fryxell, Antarctica}, journal = {PLoS ONE}, volume = {15}, year = {2020}, month = {04/2020}, pages = {e0231053}, abstract = {

Ecological theories posit that heterogeneity in environmental conditions greatly affects community structure and function. However, the degree to which ecological theory developed using plant- and animal-dominated systems applies to microbiomes is unclear. Investigating the metabolic strategies found in microbiomes are particularly informative for testing the universality of ecological theories because microorganisms have far wider metabolic capacity than plants and animals. We used metagenomic analyses to explore the relationships between the energy and physicochemical gradients in Lake Fryxell and the metabolic capacity of its benthic microbiome. Statistical analysis of the relative abundance of metabolic marker genes and gene family diversity shows that oxygenic photosynthesis, carbon fixation, and flavin-based electron bifurcation differentiate mats growing in different environmental conditions. The pattern of gene family diversity points to the likely importance of temporal environmental heterogeneity in addition to resource gradients. Overall, we found that the environmental heterogeneity of photosynthetically active radiation (PAR) and oxygen concentration ([O2]) in Lake Fryxell provide the framework by which metabolic diversity and composition of the community is structured, in accordance with its phylogenetic structure. The organization of the resulting microbial ecosystems are consistent with the maximum power principle and the species sorting model.

}, keywords = {LTER-MCM}, doi = {10.1371/journal.pone.0231053}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0231053}, author = {Dillon, Megan L. and Hawes, Ian and Jungblut, Anne D. and Mackey, Tyler J. and Eisen, Jonathan A. and Peter T. Doran and Sumner, Dawn Y.} } @article {4515, title = {Evaluating alternative metacommunity hypotheses for diatoms in the McMurdo Dry Valleys using simulations and remote sensing data}, journal = {Frontiers in Ecology and Evolution}, volume = {8}, year = {2020}, month = {09/2020}, abstract = {

Diatoms are diverse and widespread freshwater Eukaryotes that make excellent microbial subjects for addressing questions in metacommunity ecology. In the McMurdo Dry Valleys of Antarctica, the simple trophic structure of glacier-fed streams provides an ideal outdoor laboratory where well-described diatom assemblages are found within two cyanobacterial mat types, which occupy different habitats and vary in coverage within and among streams. Specifically, black mats of Nostoc spp. occur in marginal wetted habitats, and orange mats (Oscillatoria spp. and Phormidium spp.) occur in areas of consistent stream flow. Despite their importance as bioindicators for changing environmental conditions, the role of dispersal in structuring dry valley diatom metacommunities remains unclear. Here, we use MCSim, a spatially explicit metacommunity simulation package for R, to test alternative hypotheses about the roles of dispersal and species sorting in maintaining the biodiversity of diatom assemblages residing in black and orange mats. The spatial distribution and patchiness of cyanobacterial mat habitats was characterized by remote imagery of the Lake Fryxell sub-catchment in Taylor Valley. The available species pool for diatom metacommunity simulation scenarios was informed by the Antarctic Freshwater Diatoms Database, maintained by the McMurdo Dry Valleys Long Term Ecological Research program. We used simulation outcomes to test the plausibility of alternative community assembly hypotheses to explain empirically observed patterns of freshwater diatom biodiversity in the long-term record. The most plausible simulation scenarios suggest species sorting by environmental filters, alone, was not sufficient to maintain biodiversity in the Fryxell Basin diatom metacommunity. The most plausible scenarios included either (1) neutral models with different immigration rates for diatoms in orange and black mats or (2) species sorting by a relatively weak environmental filter, such that dispersal dynamics also influenced diatom community assembly, but there was not such a strong disparity\ in immigration rates between mat types. The results point to the importance of dispersal for understanding current and future biodiversity patterns for diatoms in this ecosystem, and more generally, provide further evidence that metacommunity theory is a useful framework for testing hypotheses about microbial community assembly.

}, keywords = {LTER-MCM, Antarctica, Bacillariophyceae, dispersal, Nostoc, stream ecology}, doi = {10.3389/fevo.2020.521668}, url = {https://www.frontiersin.org/article/10.3389/fevo.2020.521668/full}, author = {Eric R. Sokol and John E. Barrett and Tyler J. Kohler and Diane M. McKnight and Salvatore, Mark R. and Lee F. Stanish} } @inbook {4440, title = {Following the Astrobiology Roadmap: Origins, Habitability and Future Exploration}, booktitle = {Astrobiology: Current, Evolving, and Emerging Perspectives}, year = {2020}, publisher = {Caister Academic Press}, organization = {Caister Academic Press}, chapter = {1}, address = {Norfolk, United Kingdom}, abstract = {

Astrobiology asks three fundamental questions as outlined by the NASA Astrobiology Roadmap: 1. How did Life begin and evolve?; Is there Life elsewhere in the Universe?; and, What is the future of Life on Earth? As we gain perspective on how Life on Earth arose and adapted to its many niches, we too gain insight into how a planet achieves habitability. Here on Earth, microbial Life has evolved to exist in a wide range of habitats from aquatic systems to deserts, the human body, and the International Space Station (ISS). Landers, rovers, and orbiter missions support the search for signatures of Life beyond Earth, by generating data on surface and subsurface conditions of other worlds. These have provided evidence for water activity, supporting the potential for extinct or extant Life. To investigate the putative ecologies of these systems, we study extreme environments on Earth. Several locations on our planet provide analog settings to those we have detected or expect to find on neighboring and distant worlds. Whereas, the field of space biology uses the ISS and low gravity analogs to gain insight on how transplanted Earth-evolved organisms will respond to extraterrestrial environments. Modern genomics allows us to chronicle the genetic makeup of such organisms and provides an understanding of how Life adapts to various extreme environments.

}, keywords = {LTER-MCM}, doi = {10.21775/9781912530304.01}, url = {https://www.caister.com/astro}, author = {O{\textquoteright}Rourke, Aubrie and Zoumplis, Angela and Wilburn, Paul and Lee, Michael D. and Lee, Zhi and Vecina, Marissa and Mercader, Kysha} } @article {4471, title = {Geochemistry of aeolian material from the McMurdo Dry Valleys, Antarctica: Insights into Southern Hemisphere dust sources}, journal = {Earth and Planetary Science Letters}, volume = {547}, year = {2020}, month = {10/2020}, abstract = {

In the Southern Hemisphere, the major sources of dust and other aeolian materials are from Patagonia, South Africa, Australia, and New Zealand. Dust from Patagonia and New Zealand has been identified in ice cores throughout Antarctica, suggesting that during arid and windy periods, such as glacial periods, dust can be entrained and transported onto the continent. However, little information exists on modern Antarctic dust sources, transport, and its role in the Southern Hemisphere dust cycle. We present the first geochemical characterization of aeolian materials collected at five heights (between 5 cm and 100 cm) above the surface in four valleys within the McMurdo Dry Valleys, the largest ice-free area in Antarctica. Our mineralogy data indicate that these materials are primarily derived from local rocks of the McMurdo Volcanics, Ferrar Dolerite, Beacon Sandstone and Granite Harbor Intrusives, with varying contributions of each rock type dependent on the valley location. While major oxide, trace element and rare earth element data show that low elevation and coastal locations (with respect to the Ross Sea) are dominated by local sources, high elevation and inland locations have accumulated both local materials and dust from other distant Southern Hemisphere sources. This far-traveled material may not be accumulating today, but represents a paleo source that is resuspended from the soils. By geochemically \“fingerprinting\” aeolian materials from the MDV, we can better inform future studies on the transport of materials within Antarctica and between Southern Hemisphere land masses.

}, keywords = {LTER-MCM, aeolian material, Antarctica, major oxides, mineralogy, rare earth elements, trace elements}, doi = {10.1016/j.epsl.2020.116460}, url = {https://www.sciencedirect.com/science/article/pii/S0012821X20304040}, author = {Melisa A. Diaz and Welch, Susan A. and Sheets, J. M. and Kathleen A. Welch and Khan, Alia L. and Byron Adams and Diane M. McKnight and Craig S Cary and W. Berry Lyons} } @article {4418, title = {GIS tool to predict photosynthetically active radiation in a Dry Valley}, journal = {Antarctic Science}, year = {2020}, month = {04/2020}, abstract = {

Understanding primary productivity is a core research area of the National Science Foundation\&$\#$39;s Long-Term Ecological Research Network. This study presents the development of the GIS-based Topographic Solar Photosynthetically Active Radiation (T-sPAR) toolbox for Taylor Valley. It maps surface photosynthetically active radiation using four meteorological stations with ~20 years of data. T-sPAR estimates were validated with ground-truth data collected at Taylor Valley\&$\#$39;s major lakes during the 2014\–15 and 2015\–16 field seasons. The average daily error ranges from 0.13 mol photons m-2 day-1 (0.6\%) at Lake Fryxell to 3.8 mol photons m-2 day-1 (5.8\%) at Lake Hoare. We attribute error to variability in terrain and sun position. Finally, a user interface was developed in order to estimate total daily surface photosynthetically active radiation for any location and date within the basin. T-sPAR improves upon existing toolboxes and models by allowing for the inclusion of a statistical treatment of light attenuation due to cloud cover. The T-sPAR toolbox could be used to inform biological sampling sites based on radiation distribution, which could collectively improve estimates of net primary productivity, in some cases by up to 25\%.

}, keywords = {LTER-MCM, ArcMap, automated weather station, digital elevation model, ice-covered lakes, McMurdo Dry Valleys, R model, Taylor Valley}, doi = {10.1017/S0954102020000218}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/gis-tool-to-predict-photosynthetically-active-radiation-in-a-dry-valley/BD0BE4FF6A8F3DAAF32D698797287078}, author = {Acosta, Dimitri R. and Peter T. Doran and Myers, Madeline} } @article {4420, title = {A global database of soil nematode abundance and functional group composition}, journal = {Scientific Data}, volume = {7}, year = {2020}, month = {03/2020}, abstract = {

As the most abundant animals on earth, nematodes are a dominant component of the soil community. they play critical roles in regulating biogeochemical cycles and vegetation dynamics within and across landscapes and are an indicator of soil biological activity. Here,\ we present a comprehensive global dataset of soil nematode abundance and functional group composition. This dataset includes 6,825 georeferenced soil samples from all continents and biomes. For geospatial mapping purposes these samples are aggregated into 1,933 unique 1-km pixels, each of which is linked to 73 global environmental covariate data layers. Altogether,\ this dataset can help to gain insight into the spatial distribution patterns of soil nematode abundance and community composition, and the environmental drivers shaping these patterns.

}, keywords = {LTER-MCM}, doi = {10.1038/s41597-020-0437-3}, url = {https://www.nature.com/articles/s41597-020-0437-3}, author = {van den Hoogen, Johan and Geisen, Stefan and Diana H. Wall and Wardle, D and Traunspurger, Walter and de Goede, Ron G. M. and Byron Adams and Ahmad, Wasim and Ferris, Howard and Richard D. Bardgett and Bonkowski, Michael and Campos-Herrera, Raquel and Cares, Juvenil E. and Caruso, Tancredi and de Brito Caixeta, Larissa and Chen, Xiaoyun and Costa, Sofia R. and Creamer, Rachel and da Cunha e Castro, Jos{\'e} and Dam, Marie and Djigal, Djibril and Escuer, Miguel and Griffiths, Bryan S. and Guti{\'e}rrez, Carmen and Hohberg, Karin and Kalinkina, Daria and Kardol, Paul and Kergunteuil, Alan and Korthals, Gerard and Krashevska, Valentyna and Kudrin, Alexey A. and Li, Qi and Liang, Wenju and Magilton, Matthew and Marais, Mariette and Mart{\'\i}n, Jos{\'e} Antonio Rodr{\'\i}guez and Matveeva, Elizaveta and Mayad, El Hassan and Mzough, E. and Mulder, Christian and Mullin, Peter and Neilson, Roy and Nguyen, T. A. Duong and Uffe N. Nielsen and Okada, Hiroaki and Rius, Juan Emilio Palomares and Pan, Kaiwen and Peneva, Vlada and Pellissier, Lo{\"\i}c and Carlos Pereira da Silva, Julio and Pitteloud, Camille and Powers, Thomas O. and Powers, Kirsten and Quist, Casper W. and Rasmann, Sergio and Moreno, Sara S{\'a}nchez and Scheu, Stefan and Set{\"a}l{\"a}, Heikki and Sushchuk, Anna and Tiunov, Alexei V. and Trap, Jean and Vesterg{\r a}rd, Mette and Villenave, Cecile and Waeyenberge, Lieven and Wilschut, Rutger and Wright, Daniel G. and Keith, Aidan M. and Yang, Jiue-in and Schmidt, Olaf and Bouharroud, R. and Ferji, Z. and van der Putten, Wim H. and Routh, Devin and Crowther, Thomas Ward} } @article {4487, title = {Glycerol is an osmoprotectant in two Antarctic Chlamydomonas species from an ice-covered saline lake and is synthesized by an unusual bidomain enzyme}, journal = {Frontiers in Plant Science}, volume = {11}, year = {2020}, month = {08/2020}, abstract = {

Glycerol, a compatible solute, has previously been found to act as an osmoprotectant in some marine Chlamydomonas species and several species of Dunaliella from hypersaline ponds. Recently, Chlamydomonas reinhardtii and Dunaliella salina were shown to make glycerol with an unusual bidomain enzyme, which appears to be unique to algae, that contains a phosphoserine phosphatase and glycerol-3-phosphate dehydrogenase. Here we report that two psychrophilic species of Chlamydomonas (C. spp. UWO241 and ICE-MDV) from Lake Bonney, Antarctica also produce high levels of glycerol to survive in the lake\’s saline waters. Glycerol concentration increased linearly with salinity and at 1.3 M NaCl, exceeded 400 mM in C. sp. UWO241, the more salt-tolerant strain. We also show that both species expressed several isoforms of the bidomain enzyme. An analysis of one of the isoforms of C. sp. UWO241 showed that it was strongly upregulated by NaCl and is thus the likely source of glycerol. These results reveal another adaptation of the Lake Bonney Chlamydomonas species that allow them to survive in an extreme polar environment.

}, keywords = {LTER-MCM, Antarctica, Chlamydomonas, glycerol synthesis, glycerol-3-phosphate dehydrogenase, Lake Bonney, phosphoserine phosphatase}, doi = {10.3389/fpls.2020.01259}, url = {https://www.frontiersin.org/articles/10.3389/fpls.2020.01259/full}, author = {Raymond, James A. and Rachael M. Morgan-Kiss and Stahl-Rommel, Sarah} } @article {4297, title = {Methane production in the oxygenated water column of a perennially ice-covered Antarctic lake}, journal = {Limnology and Oceanography}, volume = {65}, year = {2020}, month = {01/2020}, abstract = {

Aerobic methane production in aquatic ecosystems impacts the global atmospheric budget of methane, but the extent, mechanism, and taxa responsible for producing this greenhouse gas are not fully understood. Lake Bonney (LB), a perennially ice-covered Antarctic lake, has cold hypersaline waters underlying an oxygenated freshwater layer. We present temporal methane concentration profiles in LB indicating methane production in the oxygenated (\>\ 200\% air saturation) water. Experiments amended with methylphosphonate (MPn) yielded methane generation, suggesting in situ methanogenesis via the carbon-phosphorus (C-P) lyase pathway. Enrichment cultures from the lake were used to isolate five bacterial strains capable of generating methane when supplied with MPn as the sole P source. Based on 16S rRNA gene sequencing, the isolates belong to the Proteobacteria (closely related to Marinomonas, Hoeflea, and Marinobacter genera) and Bacteroidetes (Algoriphagus genus). 16S rRNA metagenomic sequencing confirms the presence of these taxa in LB. None of the isolated species were reported to be capable to produce methane. In addition, orthologs of the phosphoenolpyruvate mutase gene (PepM) and methylphosphonate synthase (MPnS), enzymes involved in phosphonate and MPn biosynthesis, were widely spread in the LB shotgun metagenomic libraries; genes related to C-P lyase pathways (phn gene clusters) were also abundant. 16S rRNA and mcrA genes of anaerobic methanogens were absent in both 16S rRNA and metagenomics libraries. These data reveal that in situ aerobic biological methane production is likely a significant source of methane in LB.

}, keywords = {LTER-MCM}, doi = {10.1002/lno.11257}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lno.11257}, author = {Li, Wei and John E. Dore and Steigmeyer, August J. and Cho, Yong-Joon and Kim, Ok-Sun and Liu, Yongqin and Rachael M. Morgan-Kiss and Skidmore, Mark L. and John C. Priscu} } @article {4449, title = {Remote characterization of photosynthetic communities in the Fryxell basin of Taylor Valley, Antarctica}, journal = {Antarctic Science}, year = {2020}, month = {03/2020}, abstract = {

We investigate the spatial distribution, spectral properties and temporal variability of primary producers (e.g. communities of microbial mats and mosses) throughout the Fryxell basin of Taylor Valley, Antarctica, using high-resolution multispectral remote-sensing data. Our results suggest that photosynthetic communities can be readily detected throughout the Fryxell basin based on their unique near-infrared spectral signatures. Observed intra- and inter-annual variability in spectral signatures are consistent with short-term variations in mat distribution, hydration and photosynthetic activity. Spectral unmixing is also implemented in order to estimate mat abundance, with the most densely vegetated regions observed from orbit correlating spatially with some of the most productive regions of the Fryxell basin. Our work establishes remote sensing as a valuable tool in the study of these ecological communities in the McMurdo Dry Valleys and demonstrates how future scientific investigations and the management of specially protected areas could benefit from these tools and techniques.

}, keywords = {LTER-MCM, ecology, hydrology, McMurdo Dry Valleys, microbiology, remote sensing, spectroscopy}, doi = {10.1017/S0954102020000176}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/remote-characterization-of-photosynthetic-communities-in-the-fryxell-basin-of-taylor-valley-antarctica/8576F6BB1BCFDCA8409F5EA96CA00C6F}, author = {Salvatore, Mark R. and Borges, Schuyler R. and John E. Barrett and Eric R. Sokol and Lee F. Stanish and Power, Sarah N. and Morin, Paul} } @mastersthesis {4628, title = {Response of microbial communities to climatic disturbances in Lake Bonney, McMurdo Dry Valleys, Antarctica}, volume = {M.S.}, year = {2020}, month = {2020}, school = {Miami University}, type = {masters}, address = {Oxford, OH}, abstract = {

The McMurdo Dry Valleys is a polar desert ecosystem which composes the largest ice-free area in Antarctica, with the exception of perennially ice-covered lakes and ponds. The lakes in the valleys are the only landscape unit that support metabolic activity year-round. Recent increases in air temperature and solar radiation have led to a chain of disturbances altering the environmental conditions of these lakes. In this study, we test the impact of climatic disturbances on microbial communities in Lake Bonney, one of the lakes in the MDV. Through an integrated approach of combining field studies on natural communities in the lake (in situ) and laboratory experiments on algal isolates (ex situ), this study will attempt to understand how phytoplankton, eukaryal and bacterial communities respond to simulated disturbances. Results from the in situ experiments showed that the moat is a unique and stressful environment for under-ice communities and that under-ice shallow communities are highly sensitive to climatic disturbances. The ex situ experiments showed that certain phytoplankton species, like the chlorophytes, are more resistant to environmental alterations and thus will outcompete other phytoplankton species.

}, keywords = {LTER-MCM, climate change, McMurdo Dry Valleys, microbial communities, phytoplankton}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1595958688364877}, author = {Sherwell, Shasten S. and Rachael M. Morgan-Kiss} } @article {4413, title = {The seasonal evolution of albedo across glaciers and the surrounding landscape of Taylor Valley, Antarctica}, journal = {The Cryosphere}, volume = {14}, year = {2020}, month = {03/2020}, pages = {769-788}, abstract = {

The McMurdo Dry Valleys (MDVs) of Antarctica are a polar desert ecosystem consisting of alpine glaciers, ice-covered lakes, streams, and expanses of vegetation-free rocky soil. Because average summer temperatures are close to 0\ oC, the MDV ecosystem in general, and glacier melt dynamics in particular, are both closely linked to the energy balance. A slight increase in incoming radiation or change in albedo can have large effects on the timing and volume of meltwater. However, the seasonal evolution or spatial variability of albedo in the valleys has yet to fully characterized. In this study, we aim to understand the drivers of landscape albedo change within and across seasons. To do so, a box with a camera, GPS, and shortwave radiometer was hung from a helicopter that flew transects four to five times a season along Taylor Valley. Measurements were repeated over three seasons. These data were coupled with incoming radiation measured at six meteorological stations distributed along the valley to calculate the distribution of albedo across individual glaciers, lakes, and soil surfaces. We hypothesized that albedo would decrease throughout the austral summer with ablation of snow patches and increasing sediment exposure on the glacier and lake surfaces. However, small snow events (\<6\ mm water equivalent) coupled with ice whitening caused spatial and temporal variability of albedo across the entire landscape. Glaciers frequently followed a pattern of increasing albedo with increasing elevation, as well as increasing albedo moving from east to west laterally across the ablation zone. We suggest that spatial patterns of albedo are a function of landscape morphology trapping snow and sediment, longitudinal gradients in snowfall magnitude, and wind-driven snow redistribution from east to west along the valley. We also compare our albedo measurements to the MODIS albedo product and found that overall the data have reasonable agreement. The mismatch in spatial scale between these two datasets results in variability, which is reduced after a snow event due to albedo following valley-scale gradients of snowfall magnitude. These findings highlight the importance of understanding the spatial and temporal variability in albedo and the close coupling of climate and landscape response. This new understanding of landscape albedo can constrain landscape energy budgets, better predict meltwater generation on from MDV glaciers, and how these ecosystems will respond to changing climate at the landscape scale.

}, keywords = {LTER-MCM}, doi = {10.5194/tc-14-769-2020}, url = {https://www.the-cryosphere.net/14/769/2020/}, author = {Bergstrom, Anna J. and Michael N. Gooseff and Myers, Madeline and Peter T. Doran and Cross, Julian M.} } @article {4463, title = {Silicon isotopes reveal a non-glacial source of silicon to Crescent Stream, McMurdo Dry Valleys, Antarctica}, journal = {Frontiers in Earth Science}, volume = {8}, year = {2020}, month = {06/2020}, abstract = {

In high latitude environments, silicon is supplied to river waters by both glacial and non-glacial chemical weathering. The signal of these two end-members is often obscured by biological uptake and/or groundwater input in the river catchment. McMurdo Dry Valleys streams in Antarctica have no deep groundwater input, no connectivity between streams and no surface vegetation cover, and thus provide a simplified system for us to constrain the supply of dissolved silicon (DSi) to rivers from chemical weathering in a glacial environment. Here we report dissolved Si concentrations, germanium/silicon ratios (Ge/Si) and silicon isotope compositions (δ30SiDSi) in Crescent Stream, McMurdo Dry Valleys for samples collected between December and February in the 2014\−2015, 2015\−2016, and 2016\−2017 austral seasons. The δ30SiDSi compositions and DSi concentrations are higher than values reported in wet-based glacial meltwaters, and form a narrow cluster within the range of values reported for permafrost dominated Arctic Rivers. High\ δ30SiDSi\ compositions, ranging from +0.90\‰ to +1.39\‰, are attributed to (i) the precipitation of amorphous silica during freezing of waters in isolated pockets of the hyporheic zone in the winter and the release of Si from unfrozen pockets during meltwater-hyporheic zone exchange in the austral summer, and (ii) additional Si isotope fractionation via long-term Si uptake in clay minerals and seasonal Si uptake into diatoms superimposed on this winter-derived isotope signal. There is no relationship between\ δ30SiDSi\ compositions and DSi concentrations with seasonal and daily discharge, showing that stream waters contain DSi that is in equilibrium with the formation of secondary Si minerals in the hyporheic zone. We show that\ δ30SiDSi\ compositions can be used as tracers of silicate weathering in the hyporheic zone and possible tracers of freeze-thaw conditions in the hyporheic zone. This is important in the context of the ongoing warming in McMurdo Dry Valleys and the supply of more meltwaters to the hyporheic zone of McMurdo Dry Valley streams.

}, keywords = {LTER-MCM}, doi = {10.3389/feart.2020.00229}, url = {https://www.frontiersin.org/articles/10.3389/feart.2020.00229/full}, author = {Hirst, Catherine and Opfergelt, Sophie and Fran{\c c}ois Gaspard and Hendry, Katharine R. and Hatton, Jade E. and Sue Welch and Diane M. McKnight and W. Berry Lyons} } @article {4466, title = {Silicon isotopic composition of dry and wet-based glaciers in Antarctica}, journal = {Frontiers in Earth Science}, volume = {8}, year = {2020}, month = {07/2020}, abstract = {

Glaciers and ice sheets export significant amounts of silicon (Si) to downstream ecosystems, impacting local and potentially global biogeochemical cycles. Recent studies have shown Si in Arctic glacial meltwaters to have an isotopically distinct signature when compared to non-glacial rivers. This is likely linked to subglacial weathering processes and mechanochemical reactions. However, there are currently no silicon isotope (δ30Si) data available from meltwater streams in Antarctica, limiting the current inferences on global glacial silicon isotopic composition and its drivers. To address this gap, we present dissolved silicon (DSi), δ30SiDSi, and major ion data from meltwater streams draining a polythermal glacier in the region of the West Antarctic Peninsula (WAP; King George Island) and a cold-based glacier in East Antarctica [Commonwealth Stream, McMurdo Dry Valleys (MDV)]. These data, alongside other global datasets, improve our understanding of how contrasting glacier thermal regime can impact upon Si cycling and therefore the δ30SiDSi composition. We find a similar δ30SiDSi composition between the two sites, with the streams on King George Island varying between -0.23 and +1.23\‰ and the Commonwealth stream varying from -0.40 to +1.14\‰. However, meltwater streams in King George Island have higher DSi concentrations, and the two glacial systems exhibit opposite DSi \– δ30SiDSi trends. These contrasts likely result from differences in weathering processes, specifically the role of subglacial processes (King George Island) and, supraglacial processes followed by in-stream weathering in hyporheic zones (Commonwealth Stream). These findings are important when considering likely changes in nutrient fluxes from Antarctic glaciers under climatic warming scenarios and consequent shifts in glacial thermal regimes.

}, keywords = {LTER-MCM}, doi = {10.3389/feart.2020.00286}, url = {https://www.frontiersin.org/articles/10.3389/feart.2020.00286/full}, author = {Hatton, Jade E. and Hendry, Katharine R. and Hirst, Catherine and Opfergelt, Sophie and Henkel, Susann and Silva-Busso, Adri{\'a}n and Welch, Susan A. and Wadham, Jemma L. and W. Berry Lyons and Bagshaw, Elizabeth and Staubwasser, Michael and Diane M. McKnight} } @article {4331, title = {Vertical stratification and stability of biogeochemical processes in the deep saline waters of Lake Vanda, Antarctica}, journal = {Limnology and Oceanography}, volume = {65}, year = {2020}, month = {03/2020}, abstract = {

Lake Vanda is a permanently ice-covered lake in the McMurdo Dry Valleys of Antarctica. Its bottom waters remain stratified year-round because of a strong salinity-driven density gradient. We have assessed spatial patterns in and relationships between major biogeochemical processes in the water column of Lake Vanda. Samples were collected in the austral summers of 2008 and 2011 to measure concentrations of metabolites associated with a suite of biogeochemical processes across the deep salinity gradient. The shapes of the resulting geochemical profiles were consistent between 2008 and 2011. Metabolite production and consumption rates were estimated using a reactive transport model based on the assumption that vertical diffusion was the only activephysical transport process. We validated this model for nitrification by using stable isotope incubations to show that this process was only active at depths predicted by the model. No nitrification activity was observed at 68 m depth in spite of overlapping oxygen and ammonium gradients. We attribute this lack of activity to the competitive inhibition of ammonia monooxygenase by methane. Net nitrous oxide and nitrate consumption were observed in the oxic water column, providing evidence of aerobic denitrification. The depth of maximum net oxygen production did not coincide with the deep chlorophyll maxima (at 59.3, 63, and 68.2 m) measured in the same profile. Finally, the integrated sulfide oxidation rate was high compared with other oxidation processes, indicating that sulfide was an important electron donor for the water column microbial community.

}, keywords = {LTER-MCM}, doi = {10.1002/lno.11327}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lno.11327}, author = {Schutte, Charles A. and Samarkin, Vladimir A. and Peters, Brian and Madigan, Michael T. and Bowles, Marshall W. and Rachael M. Morgan-Kiss and Karen L. Casciotti and Joye, Samantha B.} } @article {4154, title = {The Antarctic psychrophiles Chlamydomonas spp. UWO241 and ICE-MDV exhibit differential restructuring of photosystem I in response to iron}, journal = {Photosynthesis Research}, volume = {9}, year = {2019}, month = {02/2019}, abstract = {

Chlamydomonas sp. UWO241 is a psychrophilic alga isolated from the deep photic zone of a perennially ice-covered Antarctic lake (east lobe Lake Bonney, ELB). Past studies have shown that C. sp. UWO241 exhibits constitutive downregulation of photosystem I (PSI) and high rates of PSI-associated cyclic electron flow (CEF). Iron levels in ELB are in the nanomolar range leading us to hypothesize that the unusual PSI phenotype of C. sp. UWO241 could be a response to chronic Fe-deficiency. We studied the impact of Fe availability in C. sp. UWO241, a mesophile, C. reinhardtii SAG11-32c, as well as a psychrophile isolated from the shallow photic zone of ELB, Chlamydomonas sp. ICE-MDV. Under Fe-deficiency, PsaA abundance and levels of photooxidizable P700 (ΔA820/A820) were reduced in both psychrophiles relative to the mesophile. Upon increasing Fe, C. sp. ICE-MDV and C. reinhardtii exhibited restoration of PSI function, while C. sp. UWO241 exhibited only moderate changes in PSI activity and lacked almost all LHCI proteins. Relative to Fe-excess conditions (200 μM Fe2+), C. sp. UWO241 grown in 18 μM Fe2+ exhibited downregulation of light harvesting and photosystem core proteins, as well as upregulation of a bestrophin-like anion channel protein and two CEF-associated proteins (NdsS, PGL1). Key enzymes of starch synthesis and shikimate biosynthesis were also upregulated. We conclude that in response to variable Fe availability, the psychrophile C. sp. UWO241 exhibits physiological plasticity which includes restructuring of the photo-chemical apparatus, increased PSI-associated CEF, and shifts in downstream carbon metabolism toward storage carbon and secondary stress metabolites.

}, keywords = {LTER-MCM, Antarctica, Cyclic electron flow, Iron, Photosystem I, Psychrophile}, issn = {0166-8595}, doi = {10.1007/s11120-019-00621-0}, url = {https://link.springer.com/article/10.1007/s11120-019-00621-0}, author = {Cook, Greg and Teufel, Amber and Kalra, Isha and Li, Wei and Wang, Xin and John C. Priscu and Rachael M. Morgan-Kiss} } @article {4153, title = {Biotic interactions are an unexpected yet critical control on the complexity of an abiotically driven polar ecosystem}, journal = {Communications Biology}, volume = {2}, year = {2019}, month = {02/2019}, abstract = {

Abiotic and biotic factors control ecosystem biodiversity, but their relative contributions remain unclear. The ultraoligotrophic ecosystem of the Antarctic Dry Valleys, a simple yet highly heterogeneous ecosystem, is a natural laboratory well-suited for resolving the abiotic and biotic controls of community structure. We undertook a multidisciplinary investigation to capture ecologically relevant biotic and abiotic attributes of more than 500 sites in the Dry Valleys, encompassing observed landscape heterogeneities across more than 200 km2. Using richness of autotrophic and heterotrophic taxa as a proxy for functional complexity, we linked measured variables in a parsimonious yet comprehensive structural equation model that explained significant variations in biological complexity and identified landscape-scale and fine-scale abiotic factors as the primary drivers of diversity. However, the inclusion of linkages among functional groups was essential for constructing the best-fitting model. Our findings support the notion that biotic interactions make crucial contributions even in an extremely simple ecosystem.

}, keywords = {LTER-MCM}, doi = {10.1038/s42003-018-0274-5}, url = {https://www.nature.com/articles/s42003-018-0274-5}, author = {Charles K. Lee and Laughlin, Daniel C. and Bottos, Eric M. and Caruso, Tancredi and Joy, Kurt and John E. Barrett and Brabyn, Lars and Uffe N. Nielsen and Byron Adams and Diana H. Wall and D. W. Hopkins and Pointing, Steve B. and McDonald, Ian R. and Cowan, Don A. and Banks, Jonathan C. and Stichbury, Glen A. and Jones, Irfon and Zawar-Reza, Peyman and Katurji, Marwan and Hogg, Ian D. and Sparrow, Ashley D. and Storey, Bryan C. and Allan Green, T. G. and Craig S Cary} } @phdthesis {4362, title = {Characterizing photobioregenerative technology for simulataneous thermal control and air revitalization of spacecraft and surface habitats}, volume = {Ph.D.}, year = {2019}, month = {11/2019}, school = {University of Colorado Boulder}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Algal photobioreactors have been researched as potential solutions to air revitalization in a spacecraft cabin environment by absorbing CO2 and producing O2 through photosynthesis. This photosynthesis, and consumption of produced biomass, theoretically provides a closed-loop solution for long-duration spaceflight. Addressing multiple spaceflight requirements simultaneously with algae has the potential to reduce launch mass, power and volume of future Environmental Control and Life Support (ECLS) systems. Additionally, inoculating algal culture into a water-based thermal cooling loops (flight-proven standard of active cooling found on the International Space Station (ISS)) could incorporate simultaneous air revitalization and thermal control into a common system. However, this imparts rapid, extreme thermal swings on algal cells not evolved for culture in a transient thermal environment. Therefore, the effect of dynamic thermal environments on the CO2/O2 turnover of algae was characterized to provide a first-order assessment of system feasibility. This research characterizes the effect of dynamic environments, both transient thermal environments and varying levels of CO2 concentration, on metabolic processes of the algal culture. Experiments using Antarctic algal species were included to investigate if cold-acclimated algae are more efficient than Chlorella at CO2/O2 turnover in the active cooling environment. The simultaneous heat and mass transfer coefficients of a nonporous, gas-permeable membrane were characterized, and membrane models developed for future design considerations. A photobioreactor system was designed with considerations for gravity-independence, prototyped, and tested using parameters defined by the ISS cabin environment. A failure modes and effect analysis distilled lessons learned from the previous experiments, which also informs the use of algae for bioregenerative life support. In conclusion, the resulting values from the previous characterization experiments, along with values found in literature, were used to make a first-order mass-balance comparison between current ISS ECLSS and photobioregenerative technologies. This work serves as an initial evaluation of the feasibility for using an algal photobioreactor for simultaneous air revitalization and active thermal control of a spacecraft or surface habitat.

}, keywords = {LTER-MCM}, url = {https://scholar.colorado.edu/asen_gradetds/258/}, author = {Matula, Emily E.} } @article {4332, title = {Community response of microbial primary producers to salinity is primarily driven by nutrients in lakes}, journal = {Science of the Total Environment}, volume = {696}, year = {2019}, month = {12/2019}, pages = {134001}, abstract = {

Higher microbial diversity was frequently observed in saline than fresh waters, but the underlying mechanisms remains unknown, particularly in microbial primary producers (MPP). MPP abundance and activity are notably constrained by high salinity, but facilitated by high nutrients. It remains to be ascertained whether and how nutrients regulate the salinity constraints on MPP abundance and community structure. Here we investigated the impact of nutrients on salinity constraints on MPP abundance and diversity in undisturbed lakes with a wide salinity range on the Tibetan Plateau. MPP community was explored using quantitative PCR, terminal restriction fragment length polymorphism and sequencing of cloning libraries targeting form IC cbbL gene. The MPP community structure was sorted by salinity into freshwater (salinity\<1\‰), saline (1\‰ \< salinity\<29\‰) and hypersaline (salinity\>29\‰) lakes. Furthermore, while MPP abundance, diversity and richness were significantly constrained with increasing salinity, these constraints were mitigated by enhancing total organic carbon (TOC) and total nitrogen (TN) contents in freshwater and saline lakes. In contrast, the MPP diversity increased significantly with the salinity in hypersaline lakes, due to the mitigation of enhancing TOC and TN contents and salt-tolerant MPP taxa. The mitigating effect of nutrients was more pronounced in saline than in freshwater and hypersaline lakes. The MPP compositions varied along salinity, with Betaproteobacteria dominating both the freshwater and saline lakes and Gammaproteobacteria dominating the hypersaline lakes. We concluded that high nutrients could mitigate the salinity constraining effects on MPP abundance, community richness and diversity. Our findings offer a novel insight into the salinity effects on primary producers and highlight the interactive effects of salinity and nutrients on MPP in lakes. These findings can be used as a baseline to illuminate the effects of increased anthropogenic activities altering nutrient dynamics on the global hydrological cycle and the subsequent responses thereof by MPP communities.

}, keywords = {LTER-MCM, cbbL, lake waters, microbial primary producers, nutrient, salinity}, doi = {10.1016/j.scitotenv.2019.134001}, url = {https://www.sciencedirect.com/science/article/pii/S0048969719339786}, author = {Yue, Linyan and Weidong Kong and Ji, Mukan and Liu, Jinbo and Rachael M. Morgan-Kiss} } @article {4150, title = {Differential incorporation of bacteria, organic matter, and inorganic ions into lake ice during ice formation}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {124}, year = {2019}, month = {02/2019}, pages = {585 - 600}, abstract = {

The segregation of bacteria, inorganic solutes, and total organic carbon between liquid water and ice during winter ice formation on lakes can significantly influence the concentration and survival of microorganisms in icy systems, and their roles in biogeochemical processes. Our study quantifies the distributions of bacteria and solutes between liquid and solid water phases during progressive freezing. We simulated lake ice formation in mesocosm experiments using water from perennially (Antarctica) and seasonally (Alaska and Montana, USA) ice covered lakes. We then computed concentration factors and effective segregation coefficients, which are parameters describing the incorporation of bacteria and solutes into ice. Experimental results revealed that, contrary to major ions, bacteria were readily incorporated into ice and did not concentrate in the liquid phase. The organic matter incorporated into the ice was labile, amino acid-like material, differing from the humic-like compounds that remained in the liquid phase. Results from a control mesocosm experiment (dead bacterial cells) indicated that viability of bacterial cells did not influence the incorporation of free bacterial cells into ice, but did have a role in the formation and incorporation of bacterial aggregates. Together, these findings demonstrate that bacteria, unlike other solutes, were preferentially incorporated into lake-ice during our freezing experiments, a process controlled mainly by the initial solute concentration of the liquid water source, regardless of cell viability.

}, keywords = {LTER-MCM}, doi = {10.1029/2018JG004825}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JG004825}, author = {Santib{\'a}{\~n}ez, Pamela and Alexander B. Michaud and Trista J. Vick-Majors and D{\textquoteright}Andrilli, Juliana and Amy Chiuchiolo and Hand, Kevin P. and John C. Priscu} } @article {4244, title = {Diurnal chemistry of two contrasting stream types, Taylor Valley, McMurdo Dry Valley Region, Antarctica}, journal = {E3S Web of Conferences}, volume = {98}, year = {2019}, month = {06/2019}, abstract = {

Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, whereas that for Von Guerard Stream is modulated by its resident algal mat community and through extensive hyporheic zone interaction and exchange.

}, keywords = {LTER-MCM}, doi = {10.1051/e3sconf/20199801020}, url = {https://www.e3s-conferences.org/articles/e3sconf/abs/2019/24/e3sconf_wri-162018_01020/e3sconf_wri-162018_01020.html}, author = {Harmon, Mark E. and Leslie, D.L. and W. Berry Lyons and Kathleen A. Welch and Diane M. McKnight}, editor = {Chudaev, O. and Kharaka, Y. and Harmon, R.S. and Millot, R. and Shouakar-Stash, O.} } @article {4152, title = {Drivers of protistan community autotrophy and heterotrophy in chemically stratified Antarctic lakes}, journal = {Aquatic Microbial Ecology}, volume = {82}, year = {2019}, month = {01/2019}, pages = {225 - 239}, abstract = {

Single-celled, eukaryotic microorganisms, known as protists, are responsible for 2 important, yet opposing, metabolic activities within aquatic food webs. They are major primary producers and highly active predators in marine and fresh water systems. While genomics has accelerated in recent years for this taxonomically diverse group, our understanding of the metabolic capabilities of most protists remains limited. It is also poorly understood how protist trophic mode is affected by biotic and abiotic factors, and therefore it is difficult to predict how events such as global climate change will affect the balance between autotrophic and heterotrophic activities in protist communities. To address open questions regarding how protist metabolic versatility is influenced by their environment, we characterized the potential for carbon fixation versus organic carbon degradation using enzymatic assays (RubisCO and β-D-glucosaminidase, respectively) within the water columns of ice-covered lakes in McMurdo Dry Valleys (MDV), Antarctica. Steep physical and chemical gradients in the water columns, microorganism domination and minimal allochthonous inputs makes the MDV lakes uniquely suited to investigate environment-microbe interactions. Spatial trends in RubisCO and β-D-glucosaminidase activities were lake-specific and vertically stratified within the water columns. Moreover, bottom-up drivers controlling the activity of C-fixation vs. organic C-degradation among the MDV protist communities were distinct between the upper photic vs. the deep, aphotic zones. We conclude that differential controls over major C-cycling enzymes have important implications on the influence of environmental change on the carbon and nutrient cycles in the MDV lakes.

}, keywords = {LTER-MCM, Antarctic lakes, Aquatic protists, Autotrophy, Heterotrophy, McMurdo Dry Valleys, RubisCO, β-D-glucosaminidase}, issn = {0948-3055}, doi = {10.3354/ame01891}, url = {https://www.int-res.com/abstracts/ame/v82/n3/p225-239/}, author = {Li, Wei and Dolhi-Binder, J and Cariani, ZE and Rachael M. Morgan-Kiss} } @article {4294, title = {Environmental controls on bacteriohopanepolyol profiles of benthic microbial mats from Lake Fryxell, Antarctica}, journal = {Geobiology}, year = {2019}, month = {07/2019}, abstract = {

Bacteriohopanepolyols (BHPs) are pentacyclic triterpenoid lipids that contribute to the structural integrity and physiology of some bacteria. Because some BHPs originate from specific classes of bacteria, BHPs have potential as taxonomically and environmentally diagnostic biomarkers. For example, a stereoisomer of bacteriohopanetetrol (informally BHT II) has been associated with anaerobic ammonium oxidation (anammox) bacteria and suboxic to anoxic marine environments where anammox is active. As a result, the detection of BHT II in the sedimentary record and fluctuations in the relative abundance of BHT II may inform reconstructions of nitrogen cycling and ocean redox changes through the geological record. However, there are uncertainties concerning the sources of BHT II and whether or not BHT II is produced in abundance in non-marine environments, both of which are pertinent to interpretations of BHT II signatures in sediments. To address these questions, we investigate the BHP composition of benthic microbial mats from Lake Fryxell, Antarctica. Lake Fryxell is a perennially ice-covered lake with a sharp oxycline in a density-stabilized water column. We describe the diversity and abundance of BHPs in benthic microbial mats across a transect from oxic to anoxic conditions. Generally, BHP abundances and diversity vary with the morphologies of microbial mats, which were previously shown to reflect local environmental conditions, such as irradiance and oxygen and sulfide concentrations. BHT II was identified in mats that exist within oxic to anoxic portions of the lake. However, anammox bacteria have yet to be identified in Lake Fryxell. We examine our results in the context of BHPs as biomarkers in modern and ancient environments.

}, keywords = {LTER-MCM, anammox, bacteriohopanepolyol, bacteriohopanetetrol isomer, biomarker, McMurdo Dry Valleys}, doi = {10.1111/gbi.12353}, url = {https://onlinelibrary.wiley.com/doi/full/10.1111/gbi.12353}, author = {Matys, Emily D. and Mackey, Tyler J. and Grettenberger, Christen and Mueller, Elliott and Jungblut, Anne D. and Sumner, Dawn Y. and Ian Hawes and Summons, Roger E.} } @article {4450, title = {The Geochemistry of Englacial Brine From Taylor Glacier, Antarctica}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {124}, year = {2019}, month = {03/2019}, abstract = {

Blood Falls is a hypersaline, iron-rich discharge at the terminus of the Taylor Glacier in the McMurdo Dry Valleys, Antarctica. In November 2014, brine in a conduit within the glacier was penetrated and sampled using clean-entry techniques and a thermoelectric melting probe called the IceMole. We analyzed the englacial brine sample for filterable iron (fFe), total Fe, major cations and anions, nutrients, organic carbon, and perchlorate. In addition, aliquots were analyzed for minor and trace elements and isotopes including δD and δ18O of water, δ34S and δ18O of sulfate, 234U, 238U, δ11B, 87Sr/86Sr, and δ81Br. These measurements were made in order to (1) determine the source and geochemical evolution of the brine and (2) compare the chemistry of the brine to that of nearby hypersaline lake waters and previous supraglacially sampled collections of Blood Falls outflow that were interpreted as end-member brines. The englacial brine had higher Cl\− concentrations than the Blood Falls end-member outflow; however, other constituents were similar. The isotope data indicate that the water in the brine is derived from glacier melt. The H4SiO4 concentrations and U and Sr isotope suggest a high degree of chemical weathering products. The brine has a low N:P ratio of ~7.2 with most of the dissolved inorganic nitrogen in the form of NH4+. Dissolved organic carbon concentrations are similar to end-member outflow values. Our results provide strong evidence that the original source of solutes in the brine was ancient seawater, which has been modified with the addition of chemical weathering products.

}, keywords = {LTER-MCM}, doi = {10.1029/2018JG004411}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JG004411}, author = {W. Berry Lyons and Jill A. Mikucki and German, Laura A. and Kathleen A. Welch and Sue Welch and Christopher B. Gardner and Tulaczyk, Slawek M. and Pettit, Erin C. and Kowalski, Julia and Dachwald, Bernd} } @article {4373, title = {The hydroecology of an ephemeral wetland in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Geophysical Research: Biogeosciences}, year = {2019}, month = {11/2019}, abstract = {

The McMurdo Dry Valleys (MDV) is a polar desert on the coast of East Antarctica where ephemeral wetlands become hydrologically active during warm and sunny summers when sub-surface flows are generated from melting snowfields. To understand the structure and function of polar wetland ecosystems, we investigated the hydroecology of one such wetland, the Wormherder Creek wetland, during the warm and sunny summer of 2008 \– 2009, when the wetland was hydrologically reactivated. Conservative tracer (LiCl) was injected for a 2-hour period into a stream above the wetland to determine flow path orientations and hydrologic residence times. Tracer results indicated that surface water is rapidly exchanged with wetland groundwater and wetland residence times may exceed two austral summers. Major ion concentrations were uniform in samples from surface water and shallow groundwater throughout the wetland. Microbial mats in the wetland had high autotrophic index values (the ratios of chlorophyll a [Chl-a]/ash-free dry mass [AFDM]), ranging from 9-38 μg Chl-a/mg AFDM, indicative of actively photosynthesizing mat communities. The diatom communities in the mats were relatively uniform compared to those in mats from regularly flowing MDV streams, with four endemic and one widespread diatom taxa of the genus Luticola accounting for an average of 86\% of the community. These results indicate that the hydrologic characteristics of the wetland contribute to uniform geochemical conditions. In turn, uniform geochemical conditions may explain the high autotrophic index values of the microbial mats and relatively low spatial variation of the diatom community.

}, keywords = {LTER-MCM, Antarctica, desert hydrology, diatom biodiversity, hyporheic interactions, wetlands}, doi = {10.1029/2019JG005153}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG005153}, author = {Wlostowski, Adam and Schulte, Nicholas O. and Byron Adams and Ball, Becky and Rhea M.M. Esposito and Michael N. Gooseff and W. Berry Lyons and Uffe N. Nielsen and Ross A. Virginia and Diana H. Wall and Kathleen A. Welch and Diane M. McKnight} } @mastersthesis {4165, title = {Impact of simulated polar night on Antarctic mixotrophic and strict photoautotrophic phytoplankton}, volume = {M.S.}, year = {2019}, month = {2018}, school = {Miami University}, type = {masters}, address = {Oxford, OH}, abstract = {

Phytoplankton in polar regions experience long periods of continuous darkness annually during the polar night. Due to difficulties in performing field work during this period, it is largely unknown how phytoplankton endure this extreme transition from 24-hour daylight in the fall to several months of total darkness in the austral winter. The primary goal of this study was to compare physiological and photosynthetic responses of several Antarctic phytoplankton of variable trophic abilities (pure photosynthetic vs. mixotrophic) to simulated polar night conditions, including the transition seasons before and after winter. Two distinct responses were observed to extended darkness: (1) strict photoautotrophs (Chlamydomonas sp. ICE-MDV and Chlamydomonas sp. UWO241) exhibited functional downregulation their photosynthetic processes in the winter, followed by a lag phase of several days during mimicked spring, and (2) mixotrophs (Isochrysis sp. MDV and Geminigera cryophila) maintained functional photosynthetic apparatus, increased heterotrophy through the winter, and exhibited immediate growth upon return to light incubation. These differing responses to mimicked polar night conditions could represent two different strategies for surviving the long period of darkness in the phytoplankton\’s natural environment.

}, keywords = {LTER-MCM, algae, Antarctic phytoplankton, chlorophyll fluorescence analysis, McMurdo Dry Valleys, Photosynthesis, phytoplankton, polar microbiology, polar night}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1547204599969081}, author = {Cariani, ZE and Rachael M. Morgan-Kiss} } @article {4140, title = {In a PICL: The sedimentary deposits and facies of perennially ice-covered lakes}, journal = {Sedimentology}, volume = {66}, year = {2019}, month = {04/2019}, abstract = {

Perennially ice-covered lakes can have significantly different facies than open-water lakes because sediment is transported onto the ice, where it accumulates, and sand grains preferentially melt through to be deposited on the lake floor. To characterize the facies in these lakes, sedimentary deposits from five Antarctic perennially ice-covered lakes were described using lake-bottom observations, underwater video and images, and sediment cores. One lake was dominated by laminated microbial mats and mud (derived from an abutting glacier), with disseminated sand and rare gravel. The other four lakes were dominated by laminated microbial mats and moderately well to moderately sorted medium to very coarse sand with sparse granules and pebbles; they contained minor interstitial or laminated mud (derived from streams and abutting glaciers). The sand was disseminated or localized in mounds and 1 m to more than 10 m long elongate ridges. Mounds were centimetres to metres in diameter; conical, elongate or round in shape; and isolated or deposited near or on top of one another. Sand layers in the mounds had normal, inverse, or no grading. Nine mixed mud and sand facies were defined for perennially ice-covered lakes based on the relative proportion of mud to sand and the style of sand deposition. While perennially ice-covered lake facies overlap with other ice-influenced lakes and glaciomarine facies, they are characterized by a paucity of grains coarser than granules, a narrow range in sand grain sizes, and inverse grading in the sand mounds. These facies can be used to infer changes in ice cover through time and to identify perennially ice-covered lakes in the rock record. Ancient perennially ice-covered lakes are expected on Earth and Mars, and their characterization will provide new insights into past climatic conditions and habitability.

}, keywords = {LTER-MCM}, doi = {10.1111/sed.12522}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12522}, author = {Rivera-Hernandez, Frances and Sumner, Dawn Y. and Mackey, Tyler J. and Ian Hawes and Dale T. Andersen} } @article {4186, title = {Influence of environmental drivers and potential interactions on the distribution of microbial communities from three permanently stratified Antarctic lakes}, journal = {Frontiers in Microbiology}, volume = {10}, year = {2019}, month = {05/2019}, abstract = {

The McMurdo Dry Valley (MDV) lakes represent unique habitats in the microbial world. Perennial ice covers protect liquid water columns from either significant allochthonous inputs or seasonal mixing, resulting in centuries of stable biogeochemistry. Extreme environmental conditions including low seasonal photosynthetically active radiation (PAR), near freezing temperatures, and oligotrophy have precluded higher trophic levels from the food webs. Despite these limitations, diverse microbial life flourishes in the stratified water columns, including Archaea, bacteria, fungi, protists, and viruses. While a few recent studies have applied next generation sequencing, a thorough understanding of the MDV lake microbial diversity and community structure is currently lacking. Here we used Illumina MiSeq sequencing of the 16S and 18S rRNA genes combined with a microscopic survey of key eukaryotes to compare the community structure and potential interactions among the bacterial and eukaryal communities within the water columns of Lakes Bonney (east and west lobes, ELB, and WLB, respectively) and Fryxell (FRX). Communities were distinct between the upper, oxic layers and the dark, anoxic waters, particularly among the bacterial communities residing in WLB and FRX. Both eukaryal and bacterial community structure was influenced by different biogeochemical parameters in the oxic and anoxic zones. Bacteria formed complex interaction networks which were lake-specific. Several eukaryotes exhibit potential interactions with bacteria in ELB and WLB, while interactions between these groups in the more productive FRX were relatively rare.

}, keywords = {LTER-MCM, Aquatic protists, environmental drivers, heterotrophic bacteria, interactions, McMurdo Dry Valley lakes}, doi = {10.3389/fmicb.2019.01067}, url = {https://www.frontiersin.org/articles/10.3389/fmicb.2019.01067/full}, author = {Li, Wei and Rachael M. Morgan-Kiss} } @article {4335, title = {Sabbea gen. nov., a new diatom genus (Bacillariophyta) from continental Antarctica}, journal = {Phytotaxa}, volume = {418}, year = {2019}, month = {09/2019}, abstract = {

The non-marine diatom flora of the Antarctic Continent includes several endemic taxa recorded over the past 100 years. One of these taxa, Navicula adminensis D.Roberts \& McMinn, was described from the Vestfold Hills, East Antarctica. Detailed light and scanning electron microscopy observations have shown that based on its morphological features, the species does not belong to the genus Navicula sensu stricto. To determine the most closely related genera to N. adminensis, the morpho- logical features of Adlafia, Kobayasiella, Envekadea, Stenoneis, Berkeleya, Climaconeis, and Parlibellus were compared with those of N. adminensis. Although each of these genera shows one or more similar features, none of them accommodates the salient morphological characteristics of N. adminensis. Therefore, a new genus, Sabbea gen. nov., is herein described, and Navicula adminensis is formally transferred to the new genus as Sabbea adminensis comb. nov. The genus Sabbea is characterized by uniseriate striae composed of small, rounded areolae occluded externally by individual hymenes, a rather simple raphe structure with straight, short proximal ends and short terminal raphe fissures, open girdle bands with double perforation and a very shallow mantle.

}, keywords = {LTER-MCM, Bacillariophyta, Cape Royds, East Antarctica, McMurdo Dry Valleys, new genus, Vestfold Hills}, doi = {10.11646/phytotaxa.418.1.2}, url = {https://www.mapress.com/j/pt/article/view/phytotaxa.418.1.2}, author = {Bishop, Jordan and Kopalov{\'a}, Kate{\v r}ina and Darling, Joshua P. and Schulte, Nicholas O. and Tyler J. Kohler and McMinn, Andrew and Sarah A. Spaulding and Diane M. McKnight and Bart Van de Vijver} } @article {4374, title = {The polar regions in a 2{\textdegree}C warmer world}, journal = {Science Advances}, volume = {5}, year = {2019}, month = {12/2019}, pages = {eaaw9883}, abstract = {

Over the past decade, the Arctic has warmed by 0.75\°C, far outpacing the global average, while Antarctic tem- peratures have remained comparatively stable. As Earth approaches 2\°C warming, the Arctic and Antarctic may reach 4\°C and 2\°C mean annual warming, and 7\°C and 3\°C winter warming, respectively. Expected consequences of increased Arctic warming include ongoing loss of land and sea ice, threats to wildlife and traditional human livelihoods, increased methane emissions, and extreme weather at lower latitudes. With low biodiversity, Antarctic ecosystems may be vulnerable to state shifts and species invasions. Land ice loss in both regions will contribute substantially to global sea level rise, with up to 3 m rise possible if certain thresholds are crossed. Mitigation efforts can slow or reduce warming, but without them northern high latitude warming may accelerate in the next two to four decades. International cooperation will be crucial to foreseeing and adapting to expected changes.

}, keywords = {LTER-MCM}, doi = {10.1126/sciadv.aaw9883}, url = {http://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aaw9883}, author = {Post, Eric and Alley, Richard B. and Christensen, Torben R. and Macias-Fauria, Marc and Forbes, Bruce C. and Michael N. Gooseff and Iler, Amy and Kerby, Jeffrey T. and Laidre, Kristin L. and Mann, Michael E. and Olofsson, Johan and Stroeve, Julienne C. and Ulmer, Fran and Ross A. Virginia and Wang, Muyin} } @article {4295, title = {Soil nematode abundance and functional group composition at a global scale}, journal = {Nature}, volume = {572}, year = {2019}, month = {08/2019}, abstract = {

Soil organisms are a crucial part of the terrestrial biosphere. Despite their importance for ecosystem functioning, few quantitative, spatially explicit models of the active belowground community currently exist. In particular, nematodes are the most abundant animals on Earth, filling all trophic levels in the soil food web. Here we use 6,759 georeferenced samples to generate a mechanistic understanding of the patterns of the global abundance of nematodes in the soil and the composition of their functional groups. The resulting maps show that 4.4 \± 0.64 \× 1020 nematodes (with a total biomass of approximately 0.3 gigatonnes) inhabit surface soils across the world, with higher abundances in sub-Arctic regions (38\% of total) than in temperate (24\%) or tropical (21\%) regions. Regional variations in these global trends also provide insights into local patterns of soil fertility and functioning. These high-resolution models provide the first steps towards representing soil ecological processes in global biogeochemical models and will enable the prediction of elemental cycling under current and future climate scenarios.

}, keywords = {LTER-MCM}, doi = {10.1038/s41586-019-1418-6}, url = {https://www.nature.com/articles/s41586-019-1418-6}, author = {van den Hoogen, Johan and Geisen, Stefan and Routh, Devin and Ferris, Howard and Traunspurger, Walter and Wardle, D and de Goede, Ron G. M. and Byron Adams and Ahmad, Wasim and Andriuzzi, Walter S. and Richard D. Bardgett and Bonkowski, Michael and Campos-Herrera, Raquel and Cares, Juvenil E. and Caruso, Tancredi and de Brito Caixeta, Larissa and Chen, Xiaoyun and Costa, Sofia R. and Creamer, Rachel and Mauro da Cunha Castro, Jos{\'e} and Dam, Marie and Djigal, Djibril and Escuer, Miguel and Griffiths, Bryan S. and Guti{\'e}rrez, Carmen and Hohberg, Karin and Kalinkina, Daria and Kardol, Paul and Kergunteuil, Alan and Korthals, Gerard and Krashevska, Valentyna and Kudrin, Alexey A. and Li, Qi and Liang, Wenju and Magilton, Matthew and Marais, Mariette and Mart{\'\i}n, Jos{\'e} Antonio Rodr{\'\i}guez and Matveeva, Elizaveta and Mayad, El Hassan and Mulder, Christian and Mullin, Peter and Neilson, Roy and Nguyen, T. A. Duong and Uffe N. Nielsen and Okada, Hiroaki and Rius, Juan Emilio Palomares and Pan, Kaiwen and Peneva, Vlada and Pellissier, Lo{\"\i}c and Carlos Pereira da Silva, Julio and Pitteloud, Camille and Powers, Thomas O. and Powers, Kirsten and Quist, Casper W. and Rasmann, Sergio and Moreno, Sara S{\'a}nchez and Scheu, Stefan and Set{\"a}l{\"a}, Heikki and Sushchuk, Anna and Tiunov, Alexei V. and Trap, Jean and van der Putten, W and Vesterg{\r a}rd, Mette and Villenave, Cecile and Waeyenberge, Lieven and Diana H. Wall and Wilschut, Rutger and Wright, Daniel G. and Yang, Jiue-in and Crowther, Thomas Ward} } @mastersthesis {4365, title = {Spatiotemporal impact of snow on underwater photosynthetically active radiation in Taylor Valley, East Antarctica}, volume = {M.S.}, year = {2019}, month = {08/2019}, school = {Louisiana State University}, type = {masters}, address = {Baton Rouge, LA}, abstract = {

The role of snow on underwater photosynthetically active radiation (UW PAR) in the McMurdo Dry Valleys (MDVs) has been understudied due to lack of a detailed snowfall record. Research has shown that a relationship between snow cover and UW PAR exists, but the extent has never been evaluated in great detail. Although annual snowfall values in the MDVs are low (3 to 50 mm water equivalent annually), trends of increasing snowfall on the continent under future warming conditions could lead to an increased role for snow in regulating UW PAR (and associated primary productivity). Here, I discuss evidence from the snowfall record, surface PAR, and UW PAR, of the influence of snowfall on UW PAR in the major lakes of Taylor Valley. This study aims to quantify the spatiotemporal impact of lake ice snow packs on UW PAR in Taylor Valley from field surveys, long-term UW PAR, and meteorological data. Lake Fryxell has the strongest seasonality to precipitation, which decreases inland. On average, Lake Fryxell also has the most days with snow cover on the lake ice. Lake Hoare is experiencing an increase in Fall snow persistence since the 2007 snow year. Snow less than 0.5 mm snow water equivalent (SWE) can suppress UW PAR by 40\%. The calendar day that snow falls often determines whether phototrophs will switch from photosynthesis to respiration, which suggests the importance to seasonality in determining the impact of snow on photoautotrophs and lake-wide carbon budget.

}, keywords = {LTER-MCM}, url = {https://digitalcommons.lsu.edu/gradschool_theses/4965}, author = {Myers, Madeline and Peter T. Doran} } @article {4156, title = {Aeolian material transport and its role in landscape connectivity in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Geophysical Research: Earth Surface}, volume = {123}, year = {2018}, month = {12/2018}, pages = {3323 - 3337}, abstract = {

Arid regions, particularly polar and alpine desert environments, have diminished landscape connectivity compared to temperate regions due to limited and/or seasonal hydrological processes. For these environments, aeolian processes play a particularly important role in landscape evolution and biotic community vitality through nutrient and solute additions. The McMurdo Dry Valleys (MDV) are the largest ice-free area in Antarctica and are potentially a major source of aeolian material for the continent. From this region, samples were collected at five heights (~5, 10, 20, 50, and 100 cm) above the surface seasonally for 2013 through 2015 from Alatna Valley, Victoria Valley, Miers Valley, and Taylor Valley (Taylor Glacier, East Lake Bonney, F6 (Lake Fryxell), and Explorer\’s Cove). Despite significant geological separation and varying glacial histories, low-elevation and coastal sites had similar major ion chemistries, as did high-elevation and inland locations. This locational clustering of compositions was also evident in scanning electron microscopy images and principal component analyses, particularly for samples collected at ~100 cm above the surface. Compared to published soil literature, aeolian material in Taylor Valley demonstrates a primarily down-valley transport of material toward the coast. Soluble N:P ratios in the aeolian material reflect relative nutrient enrichments seen in MDV soils and lakes, where younger, coastal soils are relatively N depleted, while older, up-valley soils are relatively P depleted. The aeolian transport of materials, including water-soluble nutrients, is an important vector of connectivity within the MDV and provides a mechanism to help \“homogenize\” the geochemistry of both soil and aquatic ecosystems.

}, keywords = {LTER-MCM}, doi = {10.1029/2017JF004589}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2017JF004589}, author = {Melisa A. Diaz and Byron Adams and Kathleen A. Welch and Sue Welch and Opiyo, Stephen O. and Khan, Alia L. and Diane M. McKnight and Craig S Cary and W. Berry Lyons} } @mastersthesis {4166, title = {Antarctic Chlamydomonas strains C. sp. UWO241 and ICE-MDV exhibit differential restructuring of the photosynthetic apparatus in response to iron}, volume = {M.S.}, year = {2018}, month = {2018}, school = {Miami University}, type = {masters}, address = {Oxford, OH}, abstract = {

As an integral cofactor for many redox-associated processes, iron (Fe) homeostasis is crucial in order to produce sufficient energy for the organism. Fe limitation, or excess, can cause major alterations in the function and structure of the photosynthetic apparatus. Photosynthetic psychrophiles grown under permanent low temperatures exhibit novel adaptations in their photosynthetic apparatus to deal with this permanent stress. The ice-covered lakes of the McMurdo Dry Valleys harbor many species of cold-adapted algae, including Chlamydomonas sp. UWO241 (UWO241). As a consequence of adaptation to multiple permanent extreme conditions, UWO241 exhibits a remodeled photosynthetic apparatus for maintaining redox poise. One unusual characteristic of UWO241 is the absence of a PSI-associated 77K fluorescence emission under a wide range of growth conditions. This phenotype resembles Fe deficiency in other model organisms such as C. reinhardtii. We hypothesized that adaptation to permanent iron deficiency in its native environment may contribute to this unusual phenotype. We compared the effect of Fe availability on the physiology and photobiology of UWO241 with the model C. reinhardtii as well as a second psychrophilic alga, Chlamydomonas sp. ICE-MDV (ICE). The impacts of a restructured photosynthetic apparatus on the unique Fe-associated phenotype in UWO241 will be discussed.

}, keywords = {LTER-MCM}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1525455621778836}, author = {Cook, Greg and Rachael M. Morgan-Kiss} } @phdthesis {4189, title = {Biogeochemistry, contaminant transport, and atmospheric exchange in glacial cryoconite meltwater of the McMurdo Dry Valleys, Antarctica}, volume = {Ph.D.}, year = {2018}, month = {2018}, pages = {245}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Polar regions serve as a global sink for many forms of semi-volatile pollution emitted from low- or midlatitudes of the populated world. This study examined the longrange atmospheric transport, fate, and phase partitioning of semi-volatile organic contaminants from air masses into meltwater and aeolian sediment on six glaciers in the McMurdo Dry Valleys of Antarctica. A novel low-cost, field-portable instrument was developed for the in-situ solid-phase extraction of trace contaminants in extreme environmental conditions without access to electricity or traditional laboratory facilities. Beyond polar research, this equipment is applicable for rapid field extraction and stabilization of samples assessing air and water quality after natural disasters. This is the first published study to identify the presence of anthropogenic perfluorinated compounds in the Transantarctic Mountain region and indicates a longer range of poleward contaminant transport than prior estimates in the Southern Hemisphere. Additional research examined the biochemistry and climatic variability of open and sealed cryoconite holes on glacial surfaces throughout the initial melt, equilibrium, and refreezing periods in 2013\–2015. High solute concentrations relative to glacial ice indicate that the pools can remain isolated from hydrologic connectivity for more than a decade. Microbial carbon cycling in pools enclosed by ice led to atmospheric disequilibrium and extreme pH. Analysis of unique air, liquid, and ice stratification in cryoconite holes revealed vertical patterns representing a highly accurate, multi-year record of past weather conditions sensitive enough to identify individual dates. This research identifies fluctuations in atmospheric contaminant transport, specific timeframes for deposition events, and may be used in back-trajectory models to help identify the source and variability of semi-volatile emissions in the Southern hemisphere.

}, keywords = {LTER-MCM, Antarctica, applied sciences, contaminant transport, cryoconite, earth sciences, glacier, hydrology, melt}, url = {https://search.proquest.com/docview/2048314678}, author = {Mass, Alex Q. and Diane M. McKnight} } @article {4159, title = {BioTIME: A database of biodiversity time series for the Anthropocene}, journal = {Global Ecology and Biogeography}, volume = {27}, year = {2018}, month = {07/2018}, pages = {760-786}, abstract = {

Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.

Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.

Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2). Time period and grain BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.

Major taxa and level of measurement:\ BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

Software format: .csv and .SQL.

}, keywords = {LTER-MCM, biodiversity, global, spatial, species richness, temporal, turnover}, doi = {10.1111/geb.12729}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12729}, author = {Dornelas, Maria and Ant{\~a}o, Laura H. and Moyes, Faye and Bates, Amanda E. and Magurran, Anne E. and Adam, Du{\v s}an and Akhmetzhanova, Asem A. and Appeltans, Ward and Arcos, Jos{\'e} Manuel and Arnold, Haley and Ayyappan, Narayanan and Badihi, Gal and Baird, Andrew H. and Barbosa, Miguel and Barreto, Tiago Egydio and B{\"a}ssler, Claus and Bellgrove, Alecia and Belmaker, Jonathan and Benedetti-Cecchi, Lisandro and Bett, Brian J. and Bjorkman, Anne D. and B{\l}a{\.z}ewicz, Magdalena and Blowes, Shane A. and Bloch, Christopher P. and Bonebrake, Timothy C. and Boyd, Susan and Bradford, Matt and Brooks, Andrew J. and Brown, James H. and Bruelheide, Helge and Budy, Phaedra and Carvalho, Fernando and Casta{\~n}eda-Moya, Edward and Chen, Chaolun Allen and Chamblee, John F. and Chase, Tory J. and Siegwart Collier, Laura and Collinge, Sharon K. and Condit, Richard and Cooper, Elisabeth J. and Cornelissen, J. Hans C. and Cotano, Unai and Kyle Crow, Shannan and Damasceno, Gabriella and Davies, Claire H. and Davis, Robert A. and Day, Frank P. and Degraer, Steven and Doherty, Tim S. and Dunn, Timothy E. and Durigan, Giselda and Duffy, J. Emmett and Edelist, Dor and Edgar, Graham J. and Elahi, Robin and Elmendorf, Sarah C. and Enemar, Anders and Ernest, S. K. Morgan and Escribano, Rub{\'e}n and Estiarte, Marc and Evans, Brian S. and Fan, Tung-Yung and Turini Farah, Fabiano and Loureiro Fernandes, Luiz and Farneda, F{\'a}bio Z. and Fidelis, Alessandra and Fitt, Robert and Fosaa, Anna Maria and Daher Correa Franco, Geraldo Antonio and Frank, Grace E. and Fraser, William R. and Garc{\'\i}a, Hernando and Cazzolla Gatti, Roberto and Givan, Or and Gorgone-Barbosa, Elizabeth and Gould, William A. and Gries, Corinna and Grossman, Gary D. and Gutierr{\'e}z, Julio R. and Hale, Stephen and Harmon, Mark E. and Harte, John and Haskins, Gary and Henshaw, Donald L. and Hermanutz, Luise and Hidalgo, Pamela and Higuchi, Pedro and Hoey, Andrew and Van Hoey, Gert and Hofgaard, Annika and Holeck, Kristen and Hollister, Robert D. and Holmes, Richard and Hoogenboom, Mia and Hsieh, Chih-hao and Hubbell, Stephen P. and Huettmann, Falk and Huffard, Christine L. and Hurlbert, Allen H. and Macedo Ivanauskas, Nat{\'a}lia and Jan{\'\i}k, David and Jandt, Ute and Ja{\.z}d{\.z}ewska, Anna and Johannessen, Tore and Johnstone, Jill and Jones, Julia and Jones, Faith A. M. and Kang, Jungwon and Kartawijaya, Tasrif and Keeley, Erin C. and Kelt, Douglas A. and Kinnear, Rebecca and Klanderud, Kari and Knutsen, Halvor and Koenig, Christopher C. and Kortz, Alessandra R. and Kr{\'a}l, Kamil and Kuhnz, Linda A. and Kuo, Chao-Yang and Kushner, David J. and Laguionie-Marchais, Claire and Lancaster, Lesley T. and Min Lee, Cheol and Lefcheck, Jonathan S. and L{\'e}vesque, Esther and Lightfoot, David and Lloret, Francisco and Lloyd, John D. and L{\'o}pez-Baucells, Adri{\`a} and Louzao, Maite and Madin, Joshua S. and Magn{\'u}sson, Borg{\th}{\'o}r and Malamud, Shahar and Matthews, Iain and McFarland, Kent P. and McGill, Brian and Diane M. McKnight and McLarney, William O. and Meador, Jason and Meserve, Peter L. and Metcalfe, Daniel J. and Meyer, Christoph F. J. and Michelsen, Anders and Milchakova, Nataliya and Moens, Tom and Moland, Even and Moore, Jon and Mathias Moreira, Carolina and M{\"u}ller, J{\"o}rg and Murphy, Grace and Myers-Smith, Isla H. and Myster, Randall W. and Naumov, Andrew and Neat, Francis and Nelson, James A. and Paul Nelson, Michael and Newton, Stephen F. and Norden, Natalia and Oliver, Jeffrey C. and Olsen, Esben M. and Onipchenko, Vladimir G. and Pabis, Krzysztof and Pabst, Robert J. and Paquette, Alain and Pardede, Sinta and Paterson, David M. and P{\'e}lissier, Rapha{\"e}l and Pe{\~n}uelas, Josep and P{\'e}rez-Matus, Alejandro and Pizarro, Oscar and Pomati, Francesco and Post, Eric and Prins, Herbert H. T. and John C. Priscu and Provoost, Pieter and Prudic, Kathleen L. and Pulliainen, Erkki and Ramesh, B. R. and Mendivil Ramos, Olivia and Rassweiler, Andrew and Rebelo, Jose Eduardo and Reed, Daniel C. and Reich, Peter B. and Remillard, Suzanne M. and Richardson, Anthony J. and Richardson, J. Paul and van Rijn, Itai and Rocha, Ricardo and Rivera-Monroy, Victor H. and Rixen, Christian and Robinson, Kevin P. and Ribeiro Rodrigues, Ricardo and de Cerqueira Rossa-Feres, Denise and Rudstam, Lars and Ruhl, Henry and Ruz, Catalina S. and Sampaio, Erica M. and Rybicki, Nancy and Rypel, Andrew and Sal, Sofia and Salgado, Beatriz and Santos, Flavio A. M. and Savassi-Coutinho, Ana Paula and Scanga, Sara and Schmidt, Jochen and Schooley, Robert and Setiawan, Fakhrizal and Shao, Kwang-Tsao and Shaver, Gaius R. and Sherman, Sally and Sherry, Thomas W. and Sici{\'n}ski, Jacek and Sievers, Caya and da Silva, Ana Carolina and Rodrigues da Silva, Fernando and Silveira, Fabio L. and Slingsby, Jasper and Smart, Tracey and Snell, Sara J. and Soudzilovskaia, Nadejda A. and Souza, Gabriel B. G. and Maluf Souza, Flaviana and Castro Souza, Vin{\'\i}cius and Stallings, Christopher D. and Stanforth, Rowan and Stanley, Emily H. and Mauro Sterza, Jos{\'e} and Stevens, Maarten and Stuart-Smith, Rick and Rondon Suarez, Yzel and Supp, Sarah} } @article {4110, title = {Catch and release: Hyporheic retention and mineralization of N-fixing Nostoc sustains downstream microbial mat biomass in two polar desert streams}, journal = {Limnology and Oceanography Letters}, volume = {3}, year = {2018}, month = {07/2018}, pages = {357 - 364}, abstract = {

Much work has been performed to investigate controls on nitrogen (N) uptake in streams, yet the fate of assimilated N is comparatively poorly resolved. Here, we use in-stream fixed N as an isotopic tracer to study the fate of assimilated N in glacial meltwater streams. We characterized\ d15N signatures of Oscillatorean, Chlorophyte, and N-fixing\ Nostoc\ mats over the lengths of two streams, and transported particulate organic matter (POM) in one. POM was isotopically most similar to\ Nostoc, which always had values near the atmospheric standard, suggesting N-fixation. Other mat types were depleted upstream, and became progressively enriched downstream, indicating a shift in N source. These results collectively show that\ Nostoc-derived N is mobilized, mineralized, and increasingly assimilated downstream as more depleted glacier-derived N is exhausted, demonstrating the importance of organic matter processing to balancing elemental budgets, and improving our understanding of nutrient cycling in lotic environments.

}, keywords = {LTER-MCM}, doi = {10.1002/lol2.10087}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lol2.10087}, author = {Tyler J. Kohler and Lee F. Stanish and Liptzin, D. and John E. Barrett and Diane M. McKnight} } @mastersthesis {4364, title = {Groundwater and thermal legacy of a large paleolake in Taylor Valley, East Antarctica as evidenced by airborne electromagnetic and sedimentological techniques}, volume = {M.S.}, year = {2018}, month = {07/2018}, school = {Louisiana State University}, type = {masters}, address = {Baton Rouge, LA}, abstract = {

During the Last Glacial Maximum, grounded ice in the Ross Sea extended into the otherwise ice-free McMurdo Dry Valleys, creating a series of large ice dammed paleolakes. Grounded ice within the mouth of Taylor Valley allowed for lake levels to reach elevations not possible at modern day and formed what is known as Glacial Lake Washburn (GLW). GLW extended from the eastern portion of Taylor Valley roughly 20 km west to a level ~300 m higher than modern day Lake Fryxell. The formation and existence of GLW has been debated, though previous studies correlate the timing of GLW with early Holocene grounded ice. Evidence of GLW has largely been constrained to the interpretation of glacial deposits and fluvial features such as lacustrine deposits, strandlines, and preserved paleodeltas. GIS and remote sensing techniques paired with regional resistivity data provide new insight into the paleohydrology of the region.

To quantify the extent of GLW, paleodelta locations were mapped using high resolution LiDAR digital elevation models and satellite imagery. Delta topset elevations were correlated between three streams in Fryxell basin to determine paleolake levels. Additionally, mean resistivity maps generated from airborne electromagnetic survey data (SkyTEM) reveal an extensive groundwater system within Fryxell basin which is interpreted as a legacy groundwater signal from GLW. Resistivity data suggests that active permafrost formation has been ongoing since onset of lake drainage, and that lake levels were over 60 m higher than modern only 1,000 \– 2,000 yr BP. This coincides with a warmer than modern paleoclimate inferred by ice core records, indicating a dynamic hydrological system that is highly sensitive to small changes in climate. As global temperatures increase, Lake Fryxell will continue to experience highly variable lake levels. Lakes and groundwater within the McMurdo Dry Valleys are critical to understanding impacts on the broader ecosystem which is largely driven by the availability of liquid water.

}, keywords = {LTER-MCM}, url = {https://digitalcommons.lsu.edu/gradschool_theses/4776}, author = {Myers, Krista F. and Peter T. Doran} } @article {4136, title = {Local and Regional Scale Heterogeneity Drive Bacterial Community Diversity and Composition in a Polar Desert}, journal = {Frontiers in Microbiology}, volume = {9}, year = {2018}, month = {08/2018}, abstract = {

The distribution of organisms in an environment is neither uniform nor random but is instead spatially patterned. The factors that control this patterning are complex and the underlying mechanisms are poorly understood. Soil microbes are critical to ecosystem function but exhibit highly complex distributions and community dynamics due in large part to the scale-dependent effects of environmental heterogeneity. To better understand the impact of environmental heterogeneity on the distribution of soil microbes, we sequenced the 16S rRNA gene from bacterial communities in the microbe-dominated polar desert ecosystem of the McMurdo Dry Valleys (MDV), Antarctica. Significant differences in key edaphic variables and alpha diversity were observed among the three lake basins of the Taylor Valley (Kruskal\–Wallis; pH: χ2 = 68.89, P \< 0.001, conductivity: χ2 = 35.03, P \< 0.001, observed species: χ2 = 7.98, P = 0.019 and inverse Simpson: χ2 = 18.52, P \< 0.001) and each basin supported distinctive microbial communities (ANOSIM R = 0.466, P = 0.001, random forest ratio of 14.1). However, relationships between community structure and edaphic characteristics were highly variable and contextual, ranging in magnitude and direction across regional, basin, and local scales. Correlations among edaphic factors (pH and soil conductivity) and the relative abundance of specific phyla were most pronounced along local environmental gradients in the Lake Fryxell basin where Acidobacteria, Bacteroidetes, and Proteobacteria declined while Deinococcus\–Thermus and Gemmatimonadetes increased with soil conductivity (all P \< 0.1). Species richness was most strongly related to the soil conductivity gradient present within this study system. We suggest that the relative importance of pH versus soil conductivity in structuring microbial communities is related to the length of edaphic gradients and the spatial scale of sampling. These results highlight the importance of conducting studies over large ranges of key environmental gradients and across multiple spatial scales to assess the influence of environmental heterogeneity on the composition and diversity of microbial communities.

}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2018.01928}, url = {https://www.frontiersin.org/article/10.3389/fmicb.2018.01928/full}, author = {Feeser, Kelli L. and David J. Van Horn and Heather N. Buelow and Colman, Daniel R. and McHugh, Theresa A. and Okie, Jordan G. and Schwartz, Egbert and Cristina D. Takacs-Vesbach} } @article {4068, title = {Near-surface refractory black carbon observations in the atmosphere and snow in the McMurdo Dry Valleys, Antarctica and potential impacts of foehn winds}, journal = {Journal of Geophysical Research: Atmospheres}, volume = {123}, year = {2018}, month = {01/2018}, pages = {2877 - 2887}, abstract = {

Measurements of light absorbing particles in the boundary layer of the high southern latitudes are scarce, particularly in the McMurdo Dry Valleys (MDV),\ Antarctica. During the 2013 - 2014 austral summer near-surface boundary layer refractory black carbon (rBC) aerosols were measured in air by a single particle soot photometer (SP2) at multiple locations in the MDV. Near-continuous rBC atmospheric measurements were collected at Lake Hoare Camp (LH) over two months and for several hours at more remote locations away from established field camps. We investigated periods dominated by both up and down-valley winds to explore the causes of differences in rBC concentrations and size distributions. Snow samples were also collected in a 1m pit on a glacier near the camp. The range of concentrations rBC in snow were 0.3 \– 1.2 \± 0.3 μg-rBC/L-H2O, and total organic carbon were 0.3 \– 1.4 \± 0.3 mg/L. The rBC concentrations measured in this snow pit are not sufficient to reduce surface albedo, however, there is potential for accumulation of rBC on snow and ice surfaces at low elevation throughout the MDV which were not measured as part of this study. At LH, the average background rBC mass aerosol concentrations was 1.3 ng/m3. rBC aerosol mass concentrations were slightly lower, 0.09 \– 1.3 ng/m3, at the most remote sites in the MDV. Concentration spikes as high as 200 ng/m3 were observed at LH, associated with local activities. During a foehn wind event, the average rBC mass concentration increased to 30-50 ng m-3. Here we show the rBC increase could be due to resuspension of locally produced BC from generators, rocket toilets, and helicopters, which may remain on the soil surface until redistributed during high wind events. Quantification of local production and long-range atmospheric transport of rBC to the MDV is necessary for understanding the impacts of this species on regional climate.\ 

}, keywords = {LTER-MCM}, doi = {10.1002/2017JD027696}, url = {http://doi.wiley.com/10.1002/2017JD027696}, author = {Khan, Alia L. and McMeeking, Gavin and Schwarz, Joshua P. and Xian, Peng and Kathleen A. Welch and W. Berry Lyons and Diane M. McKnight} } @inbook {4113, title = {Physiological and Biochemical Adaptations of Psychrophiles}, booktitle = {Extremophiles}, year = {2018}, publisher = {CRC Press}, organization = {CRC Press}, chapter = {9}, address = {Boca Raton}, abstract = {

The cold biosphere encompasses many microorganism-dominated habitats that rely on light-dependent primary production. Within these environments, there are numerous physical and chemical factors limiting metabolism and growth that the microorganisms must overcome. The psychrophilic microorganisms discussed herein integrate a complex spectrum of adaptive strategies to survive these physiological challenges, including genome evolution, enzyme structure and catalysis rate changes, cryoprotectant formation, and a multitude of photosynthetic adaptations. Psychrophilic organisms also hold the key to biotechnical advances and the future, such that psychrophilic enzymes are used for everything from laboratory reagents and industrial work to medical research and environmental sustainability. Researchers have learned to exploit psychrophiles\’ efficiency at low temperatures (i.e., cooler washing machines and energy-saving, cost-effective enzyme production), their higher energy activity (thus allowing lower concentrations of needed catalysts, reducing costs and procedure time), and their ability to contribute to hydrocarbon bioremediation. Although psychrophilic microbes exist in numerous habitats and undergo various adaptive strategies, an understanding of what makes an organism psychrophilic is still unknown in a large majority of cold-adapted organisms, and thus future investigations are needed regarding cold adaptation and their biotechnological potential. Even as research has increased over the last decade, new technological advances and high-throughput DNA sequencing will continue to provide information about cold adaptation or the mechanisms needed for survival in a changing world.

}, keywords = {LTER-MCM}, url = {https://www.taylorfrancis.com/books/e/9781498774932/chapters/10.1201\%2F9781315154695-9}, author = {Teufel, Amber G. and Rachael M. Morgan-Kiss} } @article {4107, title = {Spatial and temporal patterns of microbial mats and associated invertebrates along an Antarctic stream}, journal = {Polar Biology}, volume = {41}, year = {2018}, month = {10/2018}, pages = {1911{\textendash}1921}, abstract = {

Microbial biofilms are biological hotspots in many alpine and polar ecosystems, but the controls on and functional significance of their fauna are little known. We studied cyanobacterial mats and the underlying sediment in a glacial meltwater stream in the McMurdo Dry Valleys, Antarctica. We investigated mat biomass (total and phototrophic), diatoms, and micro-meiofauna (nematodes, rotifers, and tardigrades) at nine sites along a 1670 m stream reach in a cold, low-flow growing season, and in a warmer growing season in which peak flows (above 100 L s\−1) scoured the mats. Diatom and invertebrate communities were not related, but mat biomass in the low-flow year was negatively related to nematode abundance, including that of the omnivore\ Eudorylaimus. In the high-flow year that followed, invertebrate abundance was reduced in the mats, diatom community structure was altered, and mat biomass was higher. The difference in invertebrate abundance between years was greater in mats in upstream reaches, where the greatest increases in flow velocity may have occurred, and was negligible in mats in downstream reaches as well as in the sediment beneath the mats. Integrating our results with previous findings, we generate two predictive hypotheses to be tested in glacial meltwater streams: (1) under peak flows invertebrates decline in the microbial mats, while (2) the sediment beneath the mats is a refuge from the flow disturbance. Our results also suggest that, under stable flow conditions, microinvertebrate grazers could exert top-down control on microbial mat biomass.

}, keywords = {LTER-MCM, diatoms, Disturbance, Dry valleys, Epilithon, Microfauna, Stream flow}, doi = {10.1007/s00300-018-2331-4}, url = {http://link.springer.com/10.1007/s00300-018-2331-4}, author = {Andriuzzi, Walter S. and Lee F. Stanish and Breana L. Simmons and Chris Jaros and Byron Adams and Diana H. Wall and Diane M. McKnight} } @article {4139, title = {Stoichiometric Shifts in Soil C:N:P Promote Bacterial Taxa Dominance, Maintain Biodiversity, and Deconstruct Community Assemblages}, journal = {Frontiers in Microbiology}, volume = {9}, year = {2018}, month = {07/2018}, abstract = {

Imbalances in C:N:P supply ratios may cause bacterial resource limitations and constrain biogeochemical processes, but the importance of shifts in soil stoichiometry are complicated by the nearly limitless interactions between an immensely rich species pool and a multiple chemical resource forms. To more clearly identify the impact of soil C:N:P on bacteria, we evaluated the cumulative effects of single and coupled long-term nutrient additions (i.e., C as mannitol, N as equal concentrations NH4 + and NO3 \− , and P as Na3PO4) and water on communities in an Antarctic polar desert, Taylor Valley. Untreated soils possessed relatively low bacterial diversity, simplified organic C sources due to the absence of plants, limited inorganic N, and excess soil P potentially attenuating links between C:N:P. After 6 years of adding resources, an alleviation of C and N colimitation allowed one rare Micrococcaceae, an Arthrobacter species, to dominate, comprising 47\% of the total community abundance and elevating soil respiration by 136\% relative to untreated soils. The addition of N alone reduced C:N ratios, elevated bacterial richness and diversity, and allowed rare taxa relying on ammonium and nitrite for metabolism to become more abundant [e.g., nitrite oxidizing Nitrospira species (Nitrosomonadaceae), denitrifiers utilizing nitrite (Gemmatimonadaceae) and members of Rhodobacteraceae with a high affinity for ammonium]. Based on community co-occurrence networks, lower C:P ratios in soils following P and CP additions created more diffuse and less connected communities by disrupting 73\% of species interactions and selecting for taxa potentially exploiting abundant P. Unlike amended nutrients, water additions alone elicited no lasting impact on communities. Our results suggest that as soils become nutrient rich a wide array of outcomes are possible from species dominance and the deconstruction of species interconnectedness to the maintenance of biodiversity.

}, keywords = {LTER-MCM, ecological stoichiometry, Lake Fryxell Basin, McMurdo Dry Valleys, network community modeling, nutrient colimitation, Solirubrobacteriaceae}, doi = {10.3389/fmicb.2018.01401}, url = {https://www.frontiersin.org/article/10.3389/fmicb.2018.01401/full}, author = {Aanderud, Zachary T. and Saurey, Sabrina D. and Ball, Becky and Diana H. Wall and John E. Barrett and Muscarella, Mario E. and Griffin, Natasha A. and Ross A. Virginia and Byron Adams} } @article {4160, title = {Transit times and rapid chemical equilibrium explain chemostasis in glacial meltwater streams in the McMurdo Dry Valleys, Antarctica}, journal = {Geophysical Research Letters}, volume = {45}, year = {2018}, month = {12/2018}, pages = {13322 - 13331}, abstract = {

Fluid\  transit\  time\  is\  understood\  to\  be\  an\  important\  control\  on\  the\  shape\  of concentration-discharge (C-q) relationships, yet empirical evidence supporting this linkage is limited. We investigated C-q relationships for weathering-derived solutes across seven Antarctic glacial meltwate streams. We hypothesized that (H1) solute fluxes in McMurdo Dry Valley streams are reaction limited so that C-q\ relationships are characterized by dilution and that (H2) transit time explains between-stream variability in the degree of C-q dilution. Results show that C-q relationships are chemostatic because solute equilibrium times are shorter than stream corridor fluid transit times. Between-stream variability in the efficiency of solute production is positively correlated with transit time, suggesting that transit time is an important control on the solute export regime. These results provide empirical evidence for the controls on weathering-derived C-q relationships and have important implications for Antarctic ecosystems and solute export regimes of watersheds worldwide.

}, keywords = {LTER-MCM}, doi = {10.1029/2018GL080369}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080369}, author = {Wlostowski, Adam and Michael N. Gooseff and Diane M. McKnight and W. Berry Lyons} } @inbook {4100, title = {The Climate of Snow and Ice as Boundary Condition for Microbial Life in Psychrophiles: From Biodiversity to Biotechnology}, year = {2017}, publisher = {Springer}, organization = {Springer}, edition = {2}, abstract = {

The microclimate and structure of snow and ice are a boundary condition as well as a matrix for a large spectrum of microbial life under alpine and polar conditions. Biological activity critically depends on the supply of energy, water and nutrients, with solar radiation as the prime source of energy, varying with latitude and altitude. The energy balance at the snow or ice surface provides the boundary condition for the fluxes of energy and water to the snow and ice, with important latitudinal differences from the temperate to the polar regions. The extreme situations of sunlit rocks surrounded by snow and the environment of Antarctic cryoconite holes, where ice, water, solar radiation and nutrients interact in particular ways, closes this review on ice and its effect on microbial life.

}, keywords = {LTER-MCM}, isbn = {978-3-319-57056-3}, doi = {10.1007/978-3-319-57057-010.1007/978-3-319-57057-0_1}, url = {http://link.springer.com/content/pdf/10.1007/978-3-319-57057-0}, author = {Kuhn, Michael and Andrew G Fountain}, editor = {R. Margesin} } @article {4112, title = {A communal catalogue reveals Earth{\textquoteright}s multiscale microbial diversity}, journal = {Nature}, volume = {551}, year = {2017}, month = {11/2017}, chapter = {457}, abstract = {

Our growing awareness of the microbial world\’s importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth\’s microbial diversity.

}, keywords = {LTER-MCM}, doi = {10.1038/nature24621}, url = {https://www.nature.com/articles/nature24621}, author = {Thompson, Luke R. and Sanders, Jon G. and McDonald, Daniel and Amir, Amnon and Ladau, Joshua and Locey, Kenneth J. and Prill, Robert J. and Tripathi, Anupriya and Gibbons, Sean M. and Ackermann, Gail and Navas-Molina, Jose A. and Janssen, Stefan and Kopylova, Evguenia and V{\'a}zquez-Baeza, Yoshiki and Antonio Gonz{\'a}lez and Morton, James T. and Mirarab, Siavash and Zech Xu, Zhenjiang and Jiang, Lingjing and Haroon, Mohamed F. and Kanbar, Jad and Zhu, Qiyun and Jin Song, Se and Kosciolek, Tomasz and Bokulich, Nicholas A. and Lefler, Joshua and Brislawn, Colin J. and Humphrey, Gregory and Owens, Sarah M. and Hampton-Marcell, Jarrad and Berg-Lyons, Donna and McKenzie, Valerie and Noah Fierer and Fuhrman, Jed A. and Clauset, Aaron and Stevens, Rick L. and Shade, Ashley and Pollard, Katherine S. and Goodwin, Kelly D. and Jansson, Janet K. and Gilbert, Jack A. and Knight, Rob and The Earth Microbiome Project Consortium} } @article {4022, title = {Decadal ecosystem response to an anomalous melt season in a polar desert in Antarctica}, journal = {Nature Ecology \& Evolution}, volume = {1}, year = {2017}, month = {09/2017}, pages = {1334-1338}, keywords = {LTER-MCM}, doi = {10.1038/s41559-017-0253-0}, url = {https://www.nature.com/articles/s41559-017-0253-0}, author = {Michael N. Gooseff and John E. Barrett and Byron Adams and Peter T. Doran and Andrew G Fountain and W. Berry Lyons and Diane M. McKnight and John C. Priscu and Eric R. Sokol and Cristina D. Takacs-Vesbach and Martijn L. Vandegehuchte and Ross A. Virginia and Diana H. Wall} } @article {4002, title = {Dissolved black carbon in the global cryosphere: Concentrations and chemical signatures}, journal = {Geophysical Research Letters}, volume = {44}, year = {2017}, month = {06/2017}, pages = {6226-6234}, abstract = {

Black carbon (BC) is derived from the incomplete combustion of biomass and fossil fuels and can enhance glacial recession when deposited on snow and ice surfaces. Here we explore the influence of environmental conditions and the proximity to anthropogenic sources on the concentration and composition of dissolved black carbon (DBC), as measured by benzenepolycaroxylic acid (BPCA) markers, across snow, lakes, and streams from the global cryosphere. Data are presented from Antarctica, the Arctic, and high alpine regions of the Himalayas, Rockies, Andes, and Alps. DBC concentrations spanned from 0.62 μg/L to 170 μg/L. The median and (2.5, 97.5) quantiles in the pristine samples were 1.8 μg/L (0.62, 12), and nonpristine samples were 21 μg/L (1.6, 170). DBC is susceptible to photodegradation when exposed to solar radiation. This process leads to a less condensed BPCA signature. In general, DBC across the data set was composed of less polycondensed DBC. However, DBC from the Greenland Ice Sheet (GRIS) had a highly condensed BPCA molecular signature. This could be due to recent deposition of BC from Canadian wildfires. Variation in DBC appears to be driven by a combination of photochemical processing and the source combustion conditions under which the DBC was formed. Overall, DBC was found to persist across the global cryosphere in both pristine and nonpristine snow and surface waters. The high concentration of DBC measured in supraglacial melt on the GRIS suggests that DBC can be mobilized across ice surfaces. This is significant because these processes may jointly exacerbate surface albedo reduction in the cryosphere.\ 

}, keywords = {LTER-MCM}, doi = {10.1002/2017GL073485}, url = {http://doi.wiley.com/10.1002/2017GL073485}, author = {Khan, Alia L. and Wagner, Sasha and Jaff{\'e}, Rudolf and Xian, Peng and Williams, Mark and Armstrong, Richard and Diane M. McKnight} } @article {4064, title = {Freshwater diatom biogeography and the genus Luticola: an extreme case of endemism in Antarctica}, journal = {Polar Biology}, volume = {40}, year = {2017}, month = {03/2017}, pages = {1185-1196}, abstract = {

Historical views have characterized Antarctica as a frozen desert with low diversity, although recent studies suggest that this may not be true for microscopic organisms. For microbes, assessing endemism in the Antarctic region has been particularly important, especially against a backdrop of debate regarding their presumed cosmopolitan nature. To contribute to this conversation, we highlight the observed endemism of the freshwater diatom genus Luti- cola in Antarctica by synthesizing the results of a modern high-resolution taxonomy from the Continental, Maritime, and sub-Antarctic regions. We report that Luticola has one of the highest endemic rates of any diatom genus in Antarctica, in terms of total number of species (taxon endemism) and percentage of the entire genus (phylogenetic endemism). Of the over 200 species of Luticola globally, nearly 20\% (43) occur in the Antarctic, with 42 of these being endemic. Within regions, Maritime Antarctica has the largest number of Luticola species and endemics (28 and 23, respectively), followed by Continental Antarctica (14, 9) and sub-Antarctic islands (8, 6). Thus, 38 of the 42 endemics are found in a single region only. While the timing of Luticola diversi cation has not been established, fossil evidence suggests recent invasions and/or diversi cation over a relatively short geologic timescale. Understanding the origin and evolution of endemic diatom species in Antarctica will help us better understand microbial biogeography, as well as assess and interpret impacts of large-scale environmental change taking place at southern latitudes.

}, keywords = {LTER-MCM}, issn = {0722-4060}, doi = {10.1007/s00300-017-2090-7}, url = {https://link.springer.com/article/10.1007/s00300-017-2090-7}, author = {J. Patrick Kociolek and Kopalova, K and Hamsher, S. E. and Tyler J. Kohler and Bart Van de Vijver and Convey, Peter and Diane M. McKnight} } @article {4101, title = {High-resolution elevation mapping of the McMurdo Dry Valleys, Antarctica, and surrounding regions}, journal = {Earth System Science Data}, volume = {9}, year = {2017}, month = {07/2017}, pages = {435 - 443}, abstract = {

We present detailed surface elevation measurements for the McMurdo Dry Valleys, Antarctica derived from aerial lidar surveys flown in the austral summer of 2014\–2015 as part of an effort to understand geomorphic changes over the past decade. Lidar return density varied from 2 to \> 10 returns m\−2\ with an average of about 5 returns m\−2. Vertical and horizontal accuracies are estimated to be 7 and 3 cm, respectively. In addition to our intended targets, other ad hoc regions were also surveyed including the Pegasus flight facility and two regions on Ross Island, McMurdo Station, Scott Base (and surroundings), and the coastal margin between Cape Royds and Cape Evans. These data are included in this report and data release. The combined data are freely available at\ https://doi.org/10.5069/G9D50JX3.

}, keywords = {LTER-MCM}, doi = {10.5194/essd-9-435-2017}, url = {https://www.earth-syst-sci-data.net/9/435/2017/essd-9-435-2017.pdf}, author = {Andrew G Fountain and Fernandez-Diaz, Juan C. and Maciek K. Obryk and Joseph S. Levy and Michael N. Gooseff and David J. Van Horn and Morin, P and Shrestha, Ramesh} } @article {4023, title = {Hydrologic connectivity and implications for ecosystem processes - Lessons from naked watersheds}, journal = {Geomorphology}, volume = {277}, year = {2017}, month = {01/2017}, pages = {63 - 71}, abstract = {

Hydrologic connectivity has received great attention recently as our conceptual models of watersheds and water quality have evolved in the past several decades. However, the structural complexity of most temperate watersheds (i.e. connections among shallow soils, deep aquifers, the atmosphere and streams) and the dynamic seasonal changes that occur within them (i.e., plant senescence which impacts evapotranspiration) create significant challenges to characterizing or quantifying hydrologic connectivity. The McMurdo Dry Valleys, a polar desert in Antarctica, provide a unique opportunity to study hydrologic connectivity because there is no vegetative cover (and therefore no transpiration), and no deep aquifers connected to surface soils or streams. Glacier melt provides stream flow to well-established channels and closed-basin, ice-covered lakes on the valley floor. Streams are also connected to shallow hyporheic zones along their lengths, which are bounded at ~75 cm depth by ice-cemented permafrost. These hydrologic features and connections provide water for and underpin biological communities. Hence, exchange of water among them provides a vector for exchange of energy and dissolved solutes. Connectivity is dynamic on timescales of a day to a flow season (6\–12 weeks), as streamflow varies over these timescales. The timescales over which these connections occur is also dynamic. Exchanges between streams and hyporheic zones, for example, have been estimated to be as short as hours to as long as several weeks. These exchanges have significant implications for the biogeochemistry of these systems and the biotic communities in each feature. Here we evaluate the lessons we can learn about hydrologic connectivity in the MDV watersheds that are simplified in the context of processes occurring and water reservoirs included in the landscape, yet are sensitive to climate controls and contain substantial physical heterogeneity. We specifically explore several metrics that are simple and/or commonly employed in hydrologic analyses and interpret them in the context of connectivity between and among hydrologic features.

}, keywords = {LTER-MCM}, issn = {0169555X}, doi = {10.1016/j.geomorph.2016.04.024}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0169555X16302483}, author = {Michael N. Gooseff and Wlostowski, Adam and Diane M. McKnight and Chris Jaros} } @article {4115, title = {Impact of nitrogen and phosphorus on phytoplankton production and bacterial community structure in two stratified Antarctic lakes: a bioassay approach}, journal = {Polar Biology}, volume = {40}, year = {2017}, month = {05/2017}, chapter = {1007}, abstract = {

Arctic, Antarctic, and alpine ecosystems are recognized as sensors and sentinels of global change. As a consequence of their high sensitivity to minor climatic perturbations, permanently ice-covered lakes located in the McMurdo Dry Valleys (MDV), Antarctica, represent end members in the global network of inland bodies of water. Episodic climatic events in the form of increased summer glacial melt result in inputs of organic sediment and nutrients from glacial streams to these closed basins. Phytoplankton communities residing in the oligotrophic water columns are highly responsive to pulses in nutrient availability; however, there is a lack of understanding on whether specific phytoplankton groups are more competitive during a summer flood event and how shifts in the phytoplankton community may influence heterotrophic bacteria. A bioassay approach in 3-l bottles was used to investigate the influence of inorganic nitrogen and phosphorus availability on planktonic communities from the oligotrophic upper waters of two chemically distinct MDV lakes (Lakes Bonney and Fryxell) which differ in their external inputs and water column N/P stoichiometry. While microbial community responses varied between lakes and were nutrient-dependent, stimulation of phytoplankton biomass and productivity across all treatments was strongly linked with increased abundance of a single phytoplankton phylum (Chlorophyta). Despite stimulation of phytoplankton growth, primary and bacterial productivity was generally uncoupled; however, shifts in bacterial community diversity were observed in bioassays amended with either P or NP. We suggest that climate-associated increases in phytoplankton production and concomitant shifts in diversity will influence MDV bacterial community structure by altering the availability and composition of autochthonous carbon for heterotrophic production.

}, keywords = {LTER-MCM, Algal{\textendash}bacteria interactions, climate change, McMurdo Dry Valleys, Nutrient bioassay, Primary production}, issn = {0722-4060}, doi = {10.1007/s00300-016-2025-8}, url = {https://link.springer.com/article/10.1007/s00300-016-2025-8}, author = {Teufel, Amber G. and Li, Wei and Kiss, Andor J. and Rachael M. Morgan-Kiss} } @article {4029, title = {The influence of f{\"o}hn winds on Glacial Lake Washburn and palaeotemperatures in the McMurdo Dry Valleys, Antarctica, during the Last Glacial Maximum}, journal = {Antarctic Science}, volume = {29}, year = {2017}, month = {10/2017}, pages = {457-467}, keywords = {LTER-MCM}, doi = {10.1017/S0954102017000062}, url = {https://www.cambridge.org/core/product/identifier/S0954102017000062/type/journal_article}, author = {Maciek K. Obryk and Peter T. Doran and Waddington, E.D. and Christopher P. McKay} } @article {4114, title = {Multiple ice-binding proteins of probable prokaryotic origin in an Antarctic lake alga, Chlamydomonas sp. ICE-MDV (Chlorophyceae)}, journal = {Journal of Phycology}, volume = {53}, year = {2017}, month = {08/2017}, chapter = {848}, abstract = {

Ice-associated algae produce ice-binding proteins (IBPs) to prevent freezing damage. The IBPs of the three chlorophytes that have been examined so far share little similarity across species, making it likely that they were acquired by horizontal gene transfer (HGT). To clarify the importance and source of IBPs in chlorophytes, we sequenced the IBP genes of another Antarctic chlorophyte, Chlamydomonas sp. ICE-MDV (Chlamy-ICE). Genomic DNA and total RNA were sequenced and screened for known ice-associated genes. Chlamy-ICE has as many as 50 IBP isoforms, indicating that they have an important role in survival. The IBPs are of the DUF3494 type and have similar exon structures. The DUF3494 sequences are much more closely related to prokaryotic sequences than they are to sequences in other chlorophytes, and the chlorophyte IBP and ribosomal 18S phylogenies are dissimilar. The multiple IBP isoforms found in Chlamy-ICE and other algae may allow the algae to adapt to a greater variety of ice conditions than prokaryotes, which typically have a single IBP gene. The predicted structure of the DUF3494 domain has an ice-binding face with an orderly array of hydrophilic side chains. The results indicate that Chlamy-ICE acquired its IBP genes by HGT in a single event. The acquisitions of IBP genes by this and other species of Antarctic algae by HGT appear to be key evolutionary events that allowed algae to extend their ranges into polar environments.

}, keywords = {LTER-MCM}, doi = {10.1111/jpy.12550}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/jpy.12550}, author = {Raymond, James A. and Rachael M. Morgan-Kiss}, editor = {Valentin, K.} } @article {4018, title = {Thermal autecology describes the occurrence patterns of four benthic diatoms in McMurdo Dry Valley streams}, journal = {Polar Biology}, volume = {40}, year = {2017}, month = {06/2017}, pages = {2381-2396}, abstract = {

Benthic microbial mats in the glacial-fed melt- water streams are hotspots of productivity in the McMurdo Dry Valleys (MDV), Antarctica. Benthic diatoms are common in these mats and the[45 primarily endemic taxa represent the most diverse group of eukaryotes in the MDV. In this harsh polar desert, streams are thermally dynamic with daily water temperatures varying 6\–9 \°C and daily maximum temperatures as high as 15 \°C. Stream temperature may play a role in determining growth rates and survival strategies. To understand taxon-specific adaptations to their environment, we measured the growth rates of unialgal cultures of four diatom taxa (Psammothidium papilio, Hantzschia abundans, Hantzschia amphioxys, and Hantzschia amphioxys f. muelleri) under three temperature conditions (7.6, 10, and 15 \°C) that were representative of maximum daily stream temperatures. We found that P. papilio exhibited a constant growth rate across the full temperature range; this species is most common in streams that begin to flow early in the summer and with less variable thermal regimes. Growth rates for H. abundans were greatest at 15 \°C, but showed a non-linear relationship with temperature. H. amphioxys f. muelleri

grew faster than the other taxa studied and thrived at 10 \°C. Hantzschia amphioxys grew only at the two lower temperatures. These results aligned with the observed relationships between each taxon\’s relative abundance and stream temperatures in the long-term record maintained by the MDV Long-Term Ecological Research program. Overall, our observations suggest that differences in thermal optima may be one factor contributing to and maintaining the diversity of benthic diatom flora in the MDV.
}, keywords = {LTER-MCM}, doi = {10.1007/s00300-017-2151-y}, url = {https://link.springer.com/article/10.1007/s00300-017-2151-y}, author = {Darling, Joshua P. and Garland, Deena D. and Lee F. Stanish and Rhea M.M. Esposito and Eric R. Sokol and Diane M. McKnight} } @article {3713, title = {Aerobiology Over Antarctica {\textendash} A New Initiative for Atmospheric Ecology}, journal = {Frontiers in Microbiology}, volume = {776796194610314927235011365134445142846479110123936574}, year = {2016}, month = {02/2016}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2016.00016}, url = {http://journal.frontiersin.org/Article/10.3389/fmicb.2016.00016/abstract}, author = {Pearce, David A. and Alekhina, Irina A. and Terauds, Aleks and Wilmotte, Annick and Quesada, Antonio and Edwards, Arwyn and Dommergue, Aurelien and Sattler, Birgit and Byron Adams and Magalhaes, Catarina and Chu, Wan-Loy and Lau, Maggie C. Y. and Craig S Cary and Smith, David J. and Diana H. Wall and Eguren, Gabriela and Matcher, Gwynneth and Bradley, James A. and de Vera, Jean-Pierre and Elster, Josef and Hughes, Kevin A. and Cuthbertson, Lewis and Benning, Liane G. and Gunde-Cimerman, Nina and Convey, Peter and Hong, Soon Gyu and Pointing, Steve B. and Pellizari, Vivian H. and Vincent, Warwick F.} } @article {3717, title = {Biogeochemistry and microbial diversity in the marine cavity beneath the McMurdo Ice Shelf, Antarctica}, journal = {Limnology and Oceanography}, volume = {61}, year = {2016}, month = {11/2015}, pages = {572 - 586}, keywords = {LTER-MCM}, doi = {10.1002/lno.v61.210.1002/lno.10234}, url = {http://doi.wiley.com/10.1002/lno.v61.2http://doi.wiley.com/10.1002/lno.10234http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2Flno.10234}, author = {Trista J. Vick-Majors and Achberger, Amanda and Santib{\'a}{\~n}ez, Pamela and John E. Dore and Hodson, Timothy and Alexander B. Michaud and Brent C. Christner and Jill Ai, Jill. Mikucki and Skidmore, Mark L. and Powell, Ross and Adkins, W. Peyton and Barbante, Carlo and Mitchell, Andrew and Scherer, Reed and John C. Priscu} } @article {3917, title = {Dissolved black carbon in Antarctic lakes: chemical signatures of past and present sources}, journal = {Geophysical Research Letters}, year = {2016}, month = {06/2016}, abstract = {

The perennially ice-covered, closed-basin lakes in the McMurdo Dry Valleys, Antarctica, serve as sentinels for understanding the fate of dissolved black carbon from glacial sources in aquatic ecosystems. Here we show that dissolved black carbon can persist in freshwater and saline surface waters for thousands of years, while preserving the chemical signature of the original source materials. The ancient brines of the lake bottom waters have retained dissolved black carbon with a woody chemical signature, representing long-range transport of black carbon from wildfires. In contrast, the surface waters are enriched in contemporary black carbon from fossil fuel combustion. Comparison of samples collected 25\ years apart from the same lake suggests that the enrichment in anthropogenic black carbon is recent. Differences in the chemical composition of dissolved black carbon among the lakes are likely due to biogeochemical processing such as photochemical degradation and sorption on metal oxides.

}, keywords = {LTER-MCM}, doi = {10.1002/2016GL068609}, url = {http://doi.wiley.com/10.1002/2016GL068609}, author = {Khan, Alia L. and Jaff{\'e}, Rudolf and Ding, Yan and Diane M. McKnight} } @article {3714, title = {Evidence for dispersal and habitat controls on pond diatom communities from the McMurdo Sound Region of Antarctica}, journal = {Polar Biology}, year = {2016}, month = {02/2016}, keywords = {LTER-MCM}, issn = {0722-4060}, doi = {10.1007/s00300-016-1901-6}, url = {http://link.springer.com/10.1007/s00300-016-1901-6http://link.springer.com/content/pdf/10.1007/s00300-016-1901-6http://link.springer.com/content/pdf/10.1007/s00300-016-1901-6.pdfhttp://link.springer.com/article/10.1007/s00300-016-1901-6/fulltext.html}, author = {Sakaeva, A. and Eric R. Sokol and Tyler J. Kohler and Lee F. Stanish and Sarah A. Spaulding and Howkins, Adrian and Kathleen A. Welch and W. Berry Lyons and John E. Barrett and Diane M. McKnight} } @article {3951, title = {Hydrological Controls on Ecosystem Dynamics in Lake Fryxell, Antarctica}, journal = {PLOS ONE}, volume = {11}, year = {2016}, month = {07/2016}, pages = {e0159038}, keywords = {LTER-MCM}, doi = {10.1371/journal.pone.015903810.1371}, url = {http://dx.plos.org/10.1371/journal.pone.0159038}, author = {Herbei, Radu and Rytel, Alexander L. and W. Berry Lyons and Diane M. McKnight and Chris Jaros and Michael N. Gooseff and John C. Priscu}, editor = {Hewitt, Judi} } @phdthesis {4167, title = {Influence of abiotic drivers (light and nutrients) on photobiology and diversity of Antarctic lake phytoplankton communities}, volume = {Ph.D.}, year = {2016}, month = {2016}, school = {Miami University}, type = {doctoral}, address = {Oxford, OH}, abstract = {

Arctic, Antarctic, and alpine ecosystems are recognized as sensors and sentinels of global climate change. As a consequence of their high sensitivity to minor climatic perturbations, permanently ice-covered lakes located in the McMurdo Dry Valleys (MCM), Antarctica, represent end members in the global network of inland bodies of water. Episodic climatic events in the form of increased summer glacial melt result in inputs of organic sediment and nutrients from glacial streams to these closed basins. By better understanding how Antarctic lake communities respond to mimicked climate change, we can more accurately predict how they will react to further temperature changes in the future. We began by investigating the influence of inorganic nitrogen and phosphorus availability on planktonic communities residing in the oligotrophic upper waters of two chemically distinct MCM lakes (Lakes Bonney and Fryxell) which differ in their external inputs as well as water column N:P stoichiometry. Although microbial community responses varied between the lakes and were nutrient-dependent, stimulation of phytoplankton biomass and productivity across all treatments was strongly linked with increased abundance of a single phytoplankton phylum (Chlorophyta). Despite stimulation of phytoplankton growth, primary and bacterial productivity were largely uncoupled across all enrichments. We suggest that climate-associated shifts in phytoplankton diversity influence the bacterial community structure by altering the availability and composition of autochthonous carbon for heterotrophic production. To monitor the physiological adaptations that occur over time and depth, we then transplanted two dominant phytoplankton, Chlamydomonas sp. ICE- MDV and Isochrysis sp. MDV back into the Lake Bonney water column. Our results demonstrated that both organisms are specialists for surviving specific depths of the water column and are capable of acclimating to their native environment within a short period of time, and that the chlorophyte Chlamydomonas sp. ICE-MDV most likely makes this adjustment via photoacclimation and accumulating chlorophyll-a per cell. The final study presented here investigated whether or not the dominant chlorophyte, Chlamydomonas sp. ICE-MDV has retained the ability to respond to a diel 12-hour day/night cycle. Although light levels in MCM lakes remain low during the austral summers, daily irradiation varies by as much as tenfold during the course of the day, resulting in a circadian-like light cycle for organisms residing there. With decreased ice coverage on the lakes due to climate change and increased melt, it is likely that these light variations will become amplified over time. This study tested for the presence of a circadian rhythm under various light quality, light quantity, and temperature conditions and demonstrated that although a diel rhythm was maintained in terms of growth and several photochemical parameters, a true circadian rhythm was not identified. Although it is predicted that photosynthetic communities in polar regions will be more responsive to climate warming and episodic events, the complexity of these systems provides numerous challenges to understanding how these organism will adapt in the future.

}, keywords = {LTER-MCM, Antarctica, bacterial production, Chlamydomonas sp ICE MDV, Chlorophyll fluorescence, circadian rhythm, climate change, McMurdo Dry Valleys, nutrient amendment, photobiology, Primary production}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1468411564}, author = {Teufel, Amber G. and Rachael M. Morgan-Kiss} } @phdthesis {4168, title = {Influence of environmental drivers and interactions on the microbial community structures in permanently stratified meromictic Antarctic lakes}, volume = {Ph.D.}, year = {2016}, month = {2016}, school = {Miami University}, type = {doctoral}, address = {Oxford, OH}, abstract = {

The microbial loop plays important roles in the cycling of energy, carbon and elements in aquatic ecosystems. Viruses, bacteria, Archaea and microbial eukaryotes are key players in global carbon cycle and biogeochemical cycles. Investigating microbial diversity and community structure is crucial first step for understanding the ecological functioning in aquatic environment. Meromictic lakes are bodies of water and exhibit permanent stratification of major physical and chemical environmental factors. Microbial consortia residing in permanently stratified lakes exhibit relatively constant spatial stratification throughout the water column and are adapted to vastly different habitats within the same water. Pristine perennially-ice-covered lakes (Lake Bonney, Lake Fryxell and Lake Vanda) are meromictic lakes located in the McMurdo Dry Valleys (MDV) of Southern Victoria Land, Antarctica. The lakes have isolated water bodies and extremely stable strata that vary physically, chemically, and biologically within and between the water columns. The unique characteristics support microbially dominated food webs in these lakes.

In the research presented here, we gathered new understanding of how environmental drivers influence microbial community structure in these aquatic ecosystems. We explored the lake microbial ecology from three major approaches: 1). Assess trophic activities in the natural environment and identify potential environmental drivers impacting heterotrophic (β Glucosaminidase) and autotrophic (Ribulose 1,5 bisphosphate carboxylase) enzyme activities; 2). Resolve the protist community composition (i.e. autotrophic, heterotrophic and mixotrophic groups) based on high throughput sequencing and bioinformatics. Identify how the community structures correlate with specific environmental and biological factors; 3). Reveal the diversity of potential microbial interactions between the microorganisms in the MDV lakes at individual cell level, and investigate how the interactions vary between organisms with different nutritional strategies.

Studies of polar microbial communities on the cusp of environmental change will be important for predicting how microbial communities in low latitude aquatic systems will respond. This study expands the understanding of how environmental drivers interact with microbial communities in the Antarctica lakes, and provide new information to predict how the community structure will alter as response to climate changes.

}, keywords = {LTER-MCM}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1469757316}, author = {Li, Wei and Rachael M. Morgan-Kiss} } @article {4017, title = {Microbial Community Dynamics in Two Polar Extremes: The Lakes of the McMurdo Dry Valleys and the West Antarctic Peninsula Marine Ecosystem}, journal = {BioScience}, volume = {66}, year = {2016}, month = {Jan-10-2016}, pages = {829 - 847}, keywords = {LTER-MCM}, issn = {0006-3568}, doi = {10.1093/biosci/biw103}, url = {https://academic.oup.com/bioscience/article-lookup/doi/10.1093/biosci/biw103https://academic.oup.com/bioscience/article/66/10/829/2236137/Microbial-Community-Dynamics-in-Two-Polar-Extremes}, author = {Bowman, Jeff S. and Trista J. Vick-Majors and Rachael M. Morgan-Kiss and Cristina D. Takacs-Vesbach and Hugh W. Ducklow and John C. Priscu} } @article {4013, title = {Microbial Community Structure of Subglacial Lake Whillans, West Antarctica}, journal = {Frontiers in Microbiology}, volume = {7}, year = {2016}, month = {Oct-09-2017}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2016.01457}, url = {http://journal.frontiersin.org/Article/10.3389/fmicb.2016.01457/abstract}, author = {Achberger, Amanda and Brent C. Christner and Alexander B. Michaud and John C. Priscu and Skidmore, Mark L. and Trista J. Vick-Majors} } @article {3710, title = {Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake}, journal = {Applied and Environmental Microbiology}, volume = {82}, year = {2016}, month = {01/2016}, pages = {620 - 630}, keywords = {LTER-MCM}, issn = {0099-2240}, doi = {10.1128/AEM.02699-15}, url = {http://aem.asm.org/lookup/doi/10.1128/AEM.02699-15}, author = {Jungblut, Anne D. and Ian Hawes and Mackey, Tyler J. and Krusor, Megan and Peter T. Doran and Sumner, Dawn Y. and Eisen, Jonathan A. and Hillman, Colin and Goroncy, Alexander K.}, editor = {Stams, A. J.} } @phdthesis {4090, title = {Microbially mediated biogeochemical cycles in polar ice covered lakes}, volume = {Ph.D.}, year = {2016}, school = {Montana State University}, type = {doctoral}, address = {Bozeman, MT}, abstract = {

Lakes are important sites for globally-relevant biogeochemical cycles mediated by microorganisms. In the Arctic, seasonally ice covered thermokarst lakes are a large component in Earth\&$\#$39;s carbon cycle due to their methane emissions from organic carbon degradation. In the Antarctic, over 400 unexplored lakes exist beneath the Antarctic ice sheet with unknown biogeochemical contributions to the Earth system. This dissertation seeks to investigate the biogeochemical role of microorganisms in the lake habitat and how they interact with the seasonal and permanent ice covers of lakes in polar environments. Microbiologically clean hot water drilling was used to access a subglacial lake beneath Antarctica\&$\#$39;s ice to collect, for the first time, intact sediment and water samples. Laboratory experiments on Arctic and Antarctic, seasonally and perennially, respectively, ice covered lakes were used to investigate the impact of lake ice freezing regimes on microorganisms. My results show that subglacial lake sediments beneath the West Antarctic Ice Sheet contain solute ratios that suggest relict marine sediments were deposited during previous interglacial periods. Microbial activity overprints the marine geochemical signature to produce fluxes of ions into the Subglacial Lake Whillans water column, which ultimately drains to the Southern Ocean. Microbial activity in Subglacial Lake Whillans is partially fueled by biologically-formed methane diffusing from below our deepest collected (~38 cm) subglacial sediment samples. The ice above Subglacial Lake Whillans appears to be an important source of molecular oxygen for microorganisms to drive oxidative physiologies. My experimental evidence shows microorganisms incorporate into lake ice cover to, potentially, avoid increasing stressors from progressive lake ice freezing. Taken together, the results from this dissertation reinforce the hypothesis that subglacial environments beneath the Antarctic ice sheet are habitats for life. Further, the microorganisms in subglacial lakes participate in globally-relevant biogeochemical cycles. Here, I extend the extent of the biosphere and show sediments at the base of ice sheets are an active component of the Earth system.

}, keywords = {LTER-MCM}, url = {https://scholarworks.montana.edu/xmlui/handle/1/13793}, author = {Alexander B. Michaud}, editor = {John C. Priscu} } @article {3919, title = {Modeling the thickness of perennial ice covers on stratified lakes of the Taylor Valley, Antarctica}, journal = {Journal of Glaciology}, year = {2016}, month = {06/2016}, pages = {1 - 10}, chapter = {1}, abstract = {
A 1-D ice cover model was developed to predict and constrain drivers of long-term ice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 a (between 1996 and 2012) of ice thickness changes for the west lobe of Lake Bonney (average ice thickness = 3.53 m) and Lake Fryxell (average ice thickness = 4.22 m). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (cooling or warming). As such, shallow (\<20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.

}, keywords = {LTER-MCM}, issn = {0022-1430}, doi = {10.1017/jog.2016.69}, url = {http://www.journals.cambridge.org/abstract_S0022143016000691}, author = {Maciek K. Obryk and Peter T. Doran and J. A. Hicks and Christopher P. McKay and John C. Priscu} } @article {3959, title = {Nutrient treatments alter microbial mat colonization in two glacial meltwater streams from the McMurdo Dry Valleys, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {92}, year = {2016}, month = {03/2016}, pages = {fiw049}, abstract = {

Microbial mats are abundant in many alpine and polar aquatic ecosystems. With warmer temperatures, new hydrologic pathways are developing in these regions and increasing dissolved nutrient fluxes. In the McMurdo Dry Valleys, thermokarsting may release both nutrients and sediment, and has the potential to influence mats in glacial meltwater streams. To test the role of nutrient inputs on community structure, we created nutrient diffusing substrata (NDS) with agar enriched in N, P and N + P, with controls, and deployed them into two Dry Valley streams. We found N amendments (N and N + P) to have greater chlorophyll-a concentrations, total algal biovolume, more fine filamentous cyanobacteria and a higher proportion of live diatoms than other treatments. Furthermore, N treatments were substantially elevated in Bacteroidetes and the small diatom,\ Fistulifera pelliculosa. On the other hand, species richness was almost double in P and N + P treatments over others, and coccoid green algae and Proteobacteria were more abundant in both streams. Collectively, these data suggest that nutrients have the potential to stimulate growth and alter community structure in glacial meltwater stream microbial mats, and the recent erosion of permafrost and accelerated glacial melt will likely impact resident biota in polar lotic systems here and elsewhere.

}, keywords = {LTER-MCM}, doi = {10.1093/femsec/fiw049}, url = {http://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw049}, author = {Tyler J. Kohler and David J. Van Horn and Darling, Joshua P. and Cristina D. Takacs-Vesbach and Diane M. McKnight}, editor = {Wagner, Dirk} } @article {3958, title = {Patterns of bacterial biodiversity in the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {92}, year = {2016}, month = {08/2016}, pages = {fiw148}, abstract = {

Microbial consortia dominate glacial meltwater streams from polar regions, including the McMurdo Dry Valleys (MDV), where they thrive under physiologically stressful conditions. In this study, we examined microbial mat types and sediments found in 12 hydrologically diverse streams to describe the community diversity and composition within and across sites. Sequencing of the 16S rRNA gene from 129 samples revealed \∼24 000 operational taxonomic units (\<97\% DNA similarity), making streams the most biodiverse habitat in the MDV. Principal coordinate analyses revealed significant but weak clustering by mat type across all streams (ANOSIM R-statistic = 0.28) but stronger clustering within streams (ANOSIM R-statistic from 0.28 to 0.94). Significant relationships (P \< 0.05) were found between bacterial diversity and mat ash-free dry mass, suggesting that diversity is related to the hydrologic regimes of the various streams, which are predictive of mat biomass. However, correlations between stream chemistry and community members were weak, possibly reflecting the importance of internal processes and hydrologic conditions. Collectively, these results suggest that localized conditions dictate bacterial community composition of the same mat types and sediments from different streams, and while MDV streams are hotspots of biodiversity in an otherwise depauperate landscape, controls on community structure are complex and site specific.

}, keywords = {LTER-MCM}, doi = {10.1093/femsec/fiw148}, url = {http://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw148}, author = {David J. Van Horn and Wolf, Caitlin R. and Colman, Daniel R. and Jiang, Xiaoben and Tyler J. Kohler and Diane M. McKnight and Lee F. Stanish and Yazzie, Terrill and Cristina D. Takacs-Vesbach} } @article {3718, title = {Patterns of hydrologic connectivity in the McMurdo dry valleys, Antarctica: a synthesis of 20 years of hydrologic data}, journal = {Hydrological Processes}, volume = {30}, year = {2016}, month = {04/2016}, pages = {2958-2975}, chapter = {2958}, abstract = {

Streams in the McMurdo Dry Valleys (MDVs) of Antarctica moderate an important hydrologic and biogeochemical connection between upland alpine glaciers, valley-bottom soils, and lowland closed-basin lakes. Moreover, MDV streams are simple but dynamic systems ideal for studying interacting hydrologic and ecological dynamics. This work synthesizes 20\ years of hydrologic data, collected as part of the MDVs Long-Term Ecological Research project, to assess spatial and temporal dynamics of hydrologic connectivity between glaciers, streams, and lakes. Long-term records of stream discharge (Q), specific electrical conductance (EC), and water temperature (T) from 18 streams were analysed in order to quantify the magnitude, duration, and frequency of hydrologic connections over daily, annual, and inter-annual timescales. At a daily timescale, we observe predictable diurnal variations in Q, EC, and T. At an annual timescale, we observe longer streams to be more intermittent, warmer, and have higher median EC values, compared to shorter streams. Longer streams also behave chemostatically with respect to EC, whereas shorter streams are more strongly characterized by dilution. Inter-annually, we observe significant variability in annual runoff volumes, likely because of climatic variability over the 20 record years considered. Hydrologic connections at all timescales are vital to stream ecosystem structure and function. This synthesis of hydrologic connectivity in the MDVs provides a useful end-member template for assessing hydrologic connectivity in more structurally complex temperate watersheds.\ 

}, keywords = {LTER-MCM}, doi = {10.1002/hyp.10818}, url = {http://onlinelibrary.wiley.com/doi/10.1002/hyp.10818}, author = {Wlostowski, Adam and Michael N. Gooseff and Diane M. McKnight and Chris Jaros and W. Berry Lyons} } @article {1061, title = {Photoadaptation to the polar night by phytoplankton in a permanently ice-covered Antarctic lake}, journal = {Limnology and Oceanography}, volume = {61}, year = {2016}, month = {05/2015}, abstract = {

Photosynthetic microorganisms are a primary source of new organic carbon production in polar ecosystems. Despite their importance, relatively little is known about how they adapt to the bimodal solar cycles that exist at high latitudes. To understand how phytoplankton adapt to the extreme seasonal change in photoperiod, we transplanted cultures of a well-studied laboratory model for photosynthetic cold adaptation,\ Chlamydomonas raudensis\ UWO241, back to the water column of Lake Bonney (McMurdo Dry Valleys, Antarctica) at the depth from which it was originally cultured. The organism was suspended at this depth in dialysis tubing to allow the microalga to respond to the in situ light, temperature and dissolved ions. We then integrated in situ biological and chemical measurements with environmental molecular analyses and compared the responses of transplanted\ C. raudensis\ cultures with the natural phytoplankton community over the 6-week transition from Antarctic summer (24-h daylight) to polar night (24-h darkness). As solar radiation declined, natural communities exhibited a cessation of inorganic carbon fixation which was accompanied by a downregulation of expression of genes encoding for essential carbon fixation and photochemistry proteins. Transplanted\ C. raudensis\ cultures matched natural community trends in the regulation of photochemistry and carbon fixation gene expression, and shifted photochemical function to a shade adapted state in response to the polar night transition. We present a conceptual model for seasonal shifts in microbial community energy and carbon acquisition which integrates past cultivation-based studies in this model photopsychrophile with a body of recent work on adaptation of natural populations to polar night.

}, keywords = {LTER-MCM}, doi = {10.1002/lno.10107}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lno.10107}, author = {Rachael M. Morgan-Kiss and Michael P. Lizotte and Weidong Kong and John C. Priscu} } @article {4033, title = {Physiological Ecology of Microorganisms in Subglacial Lake Whillans}, journal = {Frontiers in Microbiology}, volume = {7}, year = {2016}, month = {Mar-10-2018}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2016.01705}, url = {http://journal.frontiersin.org/article/10.3389/fmicb.2016.01705/fullhttp://journal.frontiersin.org/article/10.3389/fmicb.2016.01705/full}, author = {Trista J. Vick-Majors and Mitchell, Andrew and Achberger, Amanda and Brent C. Christner and John E. Dore and Alexander B. Michaud and Jill A. Mikucki and Purcell, Alicia M. and Skidmore, Mark L. and John C. Priscu} } @phdthesis {4098, title = {Quantifying sources, distribution, and processing of light absorbing aerosols in the cryosphere: A comparison of dissolved and refractory black carbon in polar and high mountain regions}, volume = {Ph.D.}, year = {2016}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Light absorbing aerosols (LAAs) in snow and ice are one of the least understood parameters in global climate models due to complicated physical processes within the cryosphere and too few\ in situ\ observations. Ground observations are limited due to the difficulty of collecting and preserving samples for analysis from remote environments.
In order to help build a larger repository of ground observations, this dissertation explores the concentration and composition of black carbon (BC) in snow and glacial melt-water across the polar regions in the Arctic and Antarctic, as well as major mountain regions such as the Himalayas, Rockies, and Andes Mountains.

Three state-of-the-art methods for BC detection are applied in this dissertation. The first chapter identifies chemical signatures of past and present sources of dissolved black carbon (DBC) in Antarctic lakes, utilizing a DBC molecular marker method. Here we find that DBC with a woody signature is preserved in the deep, ancient brines of Antarctic lake bottom waters. In contrast, the surface waters are enriched in BC from fossil fuels. The second chapter, which also utilizes the DBC molecular marker

iii\ 

technique, explores DBC across the cryosphere. We show that DBC concentrations are surprisingly high in the bottom waters of Antarctic lakes compared to other remote regions of the cryosphere, even those located near point sources. Aged snow also contains higher DBC concentrations than fresh snow suggesting that dry deposition brings the majority of BC to the cryosphere. Additionally, the DBC composition across samples from the cryosphere are similar due to high amounts of solar exposure leading to photodegradation, except in fresh snow with a wildfire signature. The third and fourth chapters utilize the Single Particle Soot Photometer to measure refractory black carbon (rBC). The third chapter also applies spectral albedo measurements and the light absorption heating method to find that\ coal dust from an active mine in Svalbard, Norway significantly reduces the spectral reflectance of the surrounding Arctic surface snow.\ The fourth chapter reports aerosol rBC concentrations in the boundary layer of the McMurdo Dry Valleys, as well as in snow from the accumulation area of the Commonwealth Glacier. Here we determine that aerosol concentrations increase during high wind events, but there is no significant trend in deposition in the snow pit. This could be due to sporadic deposition during katabatic wind events.

These findings support the importance of real\ in-situ\ observations in order to fully understand the role of BC in the global carbon cycle. It is also evident that local environmental processes can control the concentrations and composition of BC in the cryosphere. These ground-based measurements will likely serve as ground validation for future remote sensing of snow/ice impurities and LAAs deposition models.

}, keywords = {LTER-MCM, applied sciences, black carbon, cryosphere, earth sciences, glacial melt, health and environmental sciences, light absorbing aerosols, polar regions, snow}, url = {https://search.proquest.com/docview/1834518541?accountid=14503}, author = {Khan, Alia L. and Diane M. McKnight} } @article {4030, title = {Responses of Antarctic Marine and Freshwater Ecosystems to Changing Ice Conditions}, journal = {BioScience}, volume = {66}, year = {2016}, month = {Jan-10-2016}, pages = {864 - 879}, keywords = {LTER-MCM}, issn = {0006-3568}, doi = {10.1093/biosci/biw109}, url = {https://academic.oup.com/bioscience/article-lookup/doi/10.1093/biosci/biw109https://academic.oup.com/bioscience/article/66/10/864/2415532/Responses-of-Antarctic-Marine-and-Freshwater}, author = {Maciek K. Obryk and Peter T. Doran and Friedlaender, Ari S. and Michael N. Gooseff and Li, Wei and Rachael M. Morgan-Kiss and John C. Priscu and Schofield, Oscar and Sharon E. Stammerjohn and Steinberg, Deborah K. and Hugh W. Ducklow} } @article {3875, title = {Stream biogeochemical and suspended sediment responses to permafrost degradation in stream banks in Taylor Valley, Antarctica}, journal = {Biogeosciences}, volume = {13}, year = {2016}, month = {03/2016}, pages = {1723 - 1732}, abstract = {

\ Stream channels in the McMurdo Dry Valleys are characteristically wide, incised, and stable. At typical flows, streams occupy a fraction of the oversized channels, providing habitat for algal mats. In January 2012, we discovered substantial channel erosion and subsurface thermomechanical erosion undercutting banks of the Crescent Stream. We sampled stream water along the impacted reach and compared concentrations of solutes to the long-term data from this stream (\ \∼\  20 years of monitoring). Thermokarst-impacted stream water demonstrated higher electrical conductivity, and concentrations of chloride, sulfate, sodium, and nitrate than the long-term medians. These results suggest that this mode of lateral permafrost degradation may substantially impact stream solute loads and potentially fertilize stream and lake ecosystems. The potential for sediment to scour or bury stream algal mats is yet to be determined, though it may offset impacts of associated increased nutrient loads to streams.

}, keywords = {LTER-MCM}, doi = {10.5194/bg-13-1723-2016}, url = {http://www.biogeosciences.net/13/1723/2016/bg-13-1723-2016.pdf}, author = {Michael N. Gooseff and David J. Van Horn and Sudman, Zachary and Diane M. McKnight and Kathleen A. Welch and W. Berry Lyons} } @article {3921, title = {Ultrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake}, journal = {Applied and Environmental Microbiology}, volume = {82}, year = {2016}, month = {06/2016}, pages = {3659 - 3670}, abstract = {

The McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescence-activated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (Flavobacteria\ and\ Methylobacteriaceae) were independently associated with two key MCM lake microalgae (Isochrysis\ and\ Chlamydomonas, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite ofChlamydomonas, a dominate primary producer in the shallow, nutrient-poor layers of the lake.

IMPORTANCE\ Single-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment.

}, keywords = {LTER-MCM}, issn = {0099-2240}, doi = {10.1128/AEM.00478-16}, url = {http://aem.asm.org/lookup/doi/10.1128/AEM.00478-16}, author = {Li, Wei and Podar, Mircea and Rachael M. Morgan-Kiss}, editor = {Kelly, R. M.} } @article {3248, title = {Antarctic microbial mats: A modern analog for Archean lacustrine oxygen oases}, journal = {Geology}, year = {2015}, month = {10/2015}, pages = {G36966.1}, abstract = {

The evolution of oxygenic photosynthesis was the most important geochemical event in

Earth history, causing the Great Oxidation Event (GOE) ~2.4 b.y. ago. However, evidence is mixed as to whether O2 production occurred locally as much as 2.8 b.y. ago, creating O2 oases, or initiated just prior to the GOE. The biogeochemical dynamics of possible O2 oases have been poorly constrained due to the absence of modern analogs. However, cyanobacteria in microbial mats in a perennially anoxic region of Lake Fryxell, Antarctica, create a 1\–2 mm O2-containing layer in the upper mat during summer, providing the first known modern analog for formation of benthic O2 oases. In Lake Fryxell, benthic cyanobacteria are present below the oxycline in the lake. Mat photosynthesis rates were slow due to low photon flux rate (1\–2 μmol m-2 s-1) under thick ice cover, but photosynthetic O2 production was sufficient to sustain up to 50 μmol O2 L-1, sandwiched between anoxic overlying water and anoxic sedi- ments. We hypothesize that Archean cyanobacteria could have similarly created O2 oases in benthic mats prior to the GOE. Analogous mats may have been at least partly responsible for geological evidence of oxidative weathering prior to the GOE, and habitats such as Lake Fryxell provide natural laboratories where the impact of benthic O2 oases on biogeochemical signatures can be investigated.\ 

}, keywords = {LTER-MCM}, issn = {0091-7613}, doi = {10.1130/G36966.1}, url = {http://geology.gsapubs.org/lookup/doi/10.1130/G36966.1}, author = {Sumner, Dawn Y. and Ian Hawes and Mackey, Tyler J. and Jungblut, Anne D. and Peter T. Doran} } @article {3306, title = {Antarctic streams as a potential source of iron for the Southern Ocean: Figure 1.}, journal = {Geology}, volume = {43}, year = {2015}, month = {11/2016}, pages = {1003 - 1006}, chapter = {1003}, abstract = {

Due to iron\’s role in oceanic primary production, there has been great interest in quantifying the importance of Fe in regions where concentrations are very low and macronutrients, nitrate and phosphate, are available. Measurements of filterable (i.e., \<0.4 μm) Fe concentrations in streams from Taylor Valley, McMurdo Dry Valleys, Antarctica, suggest that coastal-zone stream Fe input to the Southern Ocean could potentially play an important role in primary production in nearshore regions. Filterable Fe (fFe) data from streams in the McMurdo Dry Valleys were used to represent glacier meltwater that flows through ice-free landscape with the potential of transporting Fe to the Antarctic coastal zone. Estimates of potential fFe flux to the Antarctic Peninsula region using our mean fFe concentration of 10.6 \µg L\–1\ combined with an estimate of ice-free area for the Antarctic Peninsula result in an fFe flux of 1.2 \× 107\ g yr\–1. Although small compared to iceberg and aeolian Fe fluxes, future stream input to the Southern Ocean could increase due to glacier retreat and\ 

}, keywords = {LTER-MCM}, issn = {0091-7613}, doi = {10.1130/G36989.1}, url = {http://geology.gsapubs.org/lookup/doi/10.1130/G36989.1http://geology.geoscienceworld.org/lookup/doi/10.1130/G36989.1}, author = {W. Berry Lyons and Dailey, Kelsey R. and Kathleen A. Welch and Deuerling, Kelly M. and Sue Welch and Diane M. McKnight} } @article {3204, title = {Comparison of arsenic and molybdenum geochemistry in meromictic lakes of the McMurdo Dry Valleys, Antarctica: Implications for oxyanion-forming trace element behavior in permanently stratified lakes}, journal = {Chemical Geology}, volume = {404}, year = {2015}, month = {05/2015}, pages = {110 - 125}, chapter = {110}, abstract = {

Water samples were collected for arsenic (As) and molybdenum (Mo) analysis from different depths in Lakes Hoare and Fryxell, both of which are located in the Taylor Valley within the McMurdo Dry Valleys of Antarctica. Sampling depths within each lake were chosen to capture variations in As and Mo concentrations and As speciation in the oxic mixolimnia and anoxic monimolimnia of these meromictic lakes. Arsenic concentrations ranged from 0.67\ nmol\ kg\−\ 1\ to 3.54\ nmol\ kg\−\ 1\ in Lake Hoare and from 1.69\ nmol\ kg\−\ 1\ to 17.5\ nmol\ kg\−\ 1\ in Lake Fryxell. Molybdenum concentrations varied between 5.05\ nmol\ kg\−\ 1\ and 43\ nmol\ kg\−\ 1\ in Lake Hoare, and between 3.52\ nmol\ kg\−\ 1\ and 25.5\ nmol\ kg\−\ 1\ in Lake Fryxell. Concentrations of As and Mo generally increased with depth in the mixolimnion of each lake, consistent with uptake near the ice\–water interface by organic particles and/or Fe/Mn oxides/oxyhydroxides, followed by gravitational settling and regeneration/remineralization at depth in the vicinity of the redoxcline. Arsenic concentrations either remained constant (Hoare) or increased with depth (Fryxell) in the anoxic monimolimnia, whereas Mo exhibited dramatic decreases in concentrations across the redoxcline in both lakes. Geochemical modeling predicts that As and Mo occur as thioanions in the anoxic bottom waters of Lakes Hoare and Fryxell, and further that the contrasting behavior of both trace elements reflects the respective reactivity of their thioanions towards Fe-sulfide minerals such as mackinawite (FeS) and/or pyrite (FeS2). More specifically, the geochemical model suggests that Fe-sulfide mineral precipitation in the anoxic monimolimnia of both lakes regulates dissolved sulfide concentrations at levels that are too low for As-sulfide minerals (e.g., orpiment, realgar) to precipitate, whereas mackinawite and/or pyrite react(s) with particle reactive thiomolybdate anions, possibly forming an Fe\–Mo\–S mineral that precipitates and, hence, leads to Mo removal from solution.

}, keywords = {LTER-MCM}, issn = {00092541}, doi = {10.1016/j.chemgeo.2015.03.029}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0009254115001874http://api.elsevier.com/content/article/PII:S0009254115001874?httpAccept=text/xmlhttp://api.elsevier.com/content/article/PII:S0009254115001874?httpAccept=text/plain}, author = {Yang, Ningfang and Kathleen A. Welch and Mohajerin, T. Jade and Telfeyan, Katherine and Chevis, Darren A. and Grimm, Deborah A. and W. Berry Lyons and White, Christopher D. and Johannesson, Karen H.} } @article {3254, title = {Cyanobacterial diversity in benthic mats of the McMurdo Dry Valley lakes, Antarctica}, journal = {Polar Biology}, volume = {38}, year = {2015}, month = {01/2015}, pages = {1097 - 1110}, abstract = {
Perennially ice-covered, meromictic lakes in\ the McMurdo Dry Valleys, Antarctica, are useful models to\ study the relationship between cyanobacterial and environmental\ variables. They have rich benthic cyanobacterial\ mat accumulations and stable stratification of physical and\ chemical conditions. Here, we evaluated cyanobacteria\ from benthic mats from multiple depths in three geographically\ separated ice-covered lakes, Lakes Vanda,\ Hoare and Joyce, using 16S rRNA gene clone libraries. We\ identified 19 ribotypes, mostly Oscillatoriales and several
Chroococcales, as well as potentially novel cyanobacterial\ ribotypes. The majority of ribotype diversity was shared\ between lakes, and only a weak relationship between ribotype\ community structure and environmental variables\ was evident. Multivariate analysis of all lake\–depth combinations\ implied that photosynthetically active radiation,\ dissolved reactive phosphorus and conductivity were\ potentially important for shaping benthic communities in\ McMurdo Dry Valley lakes. Cyanobacterial-specific pigment\ signature analysis by high-performance liquid chromatography
showed that the cyanobacterial communities\ responded to light conditions similarly, irrespective of\ community composition. The results imply a capability\ within a suite of cyanobacteria to colonise, adapt and grow\ across broad environmental ranges and geographic space,\ and such adaptability may provide a high degree of community\ resistance and resilience to future climate-driven\ environmental change in Antarctic terrestrial aquatic
ecosystems.
}, keywords = {LTER-MCM}, issn = {0722-4060}, doi = {10.1007/s00300-015-1669-0}, url = {http://link.springer.com/10.1007/s00300-015-1669-0http://link.springer.com/content/pdf/10.1007/s00300-015-1669-0}, author = {Zhang, L. and Jungblut, Anne D. and Ian Hawes and Dale T. Andersen and Sumner, Dawn Y. and Mackey, Tyler J.} } @article {3012, title = {Deep groundwater and potential subsurface habitats beneath an Antarctic dry valley}, journal = {Nature Communications}, volume = {6}, year = {2015}, month = {Apr-04-2017}, pages = {6831}, abstract = {The occurrence of groundwater in Antarctica, particularly in the ice-free regions and along the coastal margins is poorly understood. Here we use an airborne transient electromagnetic (AEM) sensor to produce extensive imagery of resistivity beneath Taylor Valley. Regional-scale zones of low subsurface resistivity were detected that are inconsistent with the high resistivity of glacier ice or dry permafrost in this region. We interpret these results as an indication that liquid, with sufficiently high solute content, exists at temperatures well below freezing and considered within the range suitable for microbial life. These inferred brines are widespread within permafrost and extend below glaciers and lakes. One system emanates from below Taylor Glacier into Lake Bonney and a second system connects the ocean with the eastern 18 km of the valley. A connection between these two basins was not detected to the depth limitation of the AEM survey (~350 m).}, keywords = {LTER-MCM}, doi = {10.1038/ncomms7831}, url = {http://www.nature.com/doifinder/10.1038/ncomms7831}, author = {Jill A. Mikucki and Auken, E. and Tulaczyk, S and Ross A. Virginia and Schamper, C. and S{\o}rensen, K. I. and Peter T. Doran and Hilary A. Dugan and Foley, N.} } @article {3715, title = {Global environmental change and the nature of aboveground net primary productivity responses: insights from long-term experiments}, journal = {Oecologia}, volume = {177}, year = {2015}, month = {04/2015}, pages = {935 - 947}, keywords = {LTER-MCM}, issn = {0029-8549}, doi = {10.1007/s00442-015-3230-9}, url = {http://link.springer.com/10.1007/s00442-015-3230-9http://link.springer.com/content/pdf/10.1007/s00442-015-3230-9}, author = {Smith, Melinda D. and La Pierre, Kimberly J. and Collins, SL and Knapp, Alan K. and Gross, Katherine L. and John E. Barrett and Frey, Serita D. and Gough, Laura and Miller, Robert J. and Morris, James T. and Rustad, Lindsey E. and Yarie, John} } @article {3721, title = { Long-Term Hydrologic Control of Microbial Mat Abundance in McMurdo Dry Valley Streams, Antarctica.}, journal = {Ecosystems}, volume = {18}, year = {2015}, month = {03/2015}, pages = {310-327}, chapter = {310}, abstract = {

Given alterations in global hydrologic regime, we examine the role of hydrology in regulating stream microbial mat abundance in the McMurdo Dry Valleys, Antarctica. Here, perennial mats persist as a desiccated crust until revived by summer streamflow, which varies inter-annually, and has increased since the 1990s. We predicted high flows to scour mats, and intra-seasonal drying to slow growth. Responses were hypothesized to differ based on mat location within streams, along with geomorphology, which may promote (high coverage) or discourage (low coverage) accrual. We compared hydrologic trends with the biomass of green and orange mats, which grow in the channel, and black mats growing at stream margins for 16 diverse stream transects over two decades. We found mat biomass collectively decreased during first decade coinciding with low flows, and increased following elevated discharges. Green mat biomass showed the greatest correlations with hydrology and was stimulated by discharge in high coverage transects, but negatively correlated in low coverage due to habitat scour. In contrast, orange mat biomass was negatively related to flow in high coverage transects, but positively correlated in low coverage because of side-channel expansion. Black mats were weakly correlated with all hydrologic variables regardless of coverage. Lastly, model selection indicated the best combination of predictive hydrologic variables for biomass differed between mat types, but also high and low coverage transects. These results demonstrate the importance of geomorphology and species composition to modeling primary production, and will be useful in predicting ecological responses of benthic habitats to altered hydrologic regimes.

}, keywords = {LTER-MCM}, url = {http://link.springer.com/article/10.1007\%2Fs10021-014-9829-6}, author = {Tyler J. Kohler and Lee F. Stanish and Stenven Crisp and Koch, J. and Liptzin, D. and Baeseman, J. and Diane M. McKnight} } @article {3716, title = {Mitochondrial DNA analyses reveal widespread tardigrade diversity in Antarctica}, journal = {Invertebrate Systematics}, volume = {29}, year = {2015}, month = {12/2015}, pages = {578}, keywords = {LTER-MCM}, issn = {1445-5226}, doi = {10.1071/IS14019}, url = {http://www.publish.csiro.au/?paper=IS14019}, author = {Velasco-Castrillon, Alejandro and McInnes, Sandra J. and Schultz, Mark B. and Arroniz-Crespo, Maria and D{\textquoteright}Haese, Cyrille A. and Gibson, John A. E. and Byron Adams and Page, Timothy J. and Austin, Andrew D. and Cooper, Steven J. B. and Stevens, Mark I.} } @phdthesis {4087, title = {Physical and chemical controls on the abundance and composition of stream microbial mats from the McMurdo Dry Valleys, Antarctica}, volume = {Ph.D.}, year = {2015}, pages = {272}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

The McMurdo Dry Valleys of Antarctica are a cold, dry desert, yet perennial microbial mats are abundant in the ephemeral glacial meltwater streams that flow during austral summers. Three types of mats are present (orange, black, and green), and are primarily comprised of filamentous cyanobacteria,\ Nostoc, and chlorophytes, respectively. Mat types furthermore occupy distinct habitats within streams, utilizing the benthos, hyporheic zone, and water column, which expose them to different environmental conditions. Due to a lack of lateral inflows, allochthonous organic inputs, and negligible grazing activity, these streams are ideal for the controlled ecological study of microbial mats. Here, I investigated how mats will respond to physical disturbance, alterations in the hydrologic regime, and nutrient liberation from permafrost melt in the future. Specifically, I: 1) quantified and characterized the regrowth of mat biomass, community structure, and elemental stoichiometry after a scouring disturbance, 2) investigated how geomorphology and taxonomic identity influences the response of mat biomass to hydrologic regime in transects monitored over two decades, and 3) evaluated relationships between water chemistry and the elemental and isotopic composition of mat types over longitudinal and valley-wide gradients in Taylor Valley. I found that mats recovered ~20-50\% of their biomass over the course of an austral summer following scour. Algal communities were significantly different in composition between disturbed and control treatments, but all samples naturally varied in species and elemental stoichiometry over the study period. When the long- term record of mat biomass was compared with hydrologic variables, stream channel mats (orange and green) had the greatest correlations, while marginal mats (black) showed weaker relationships with flow regime. Relationships also differed as a function of stream geomorphology, indicating the importance of substrata and gradient in conjunction with discharge. Lastly, mats showed unique elemental and isotopic compositions. Green and orange mats within the stream channel most reflected water column nutrient concentrations, while black mats showed significant nitrogen fixation. These results highlight the importance of taxonomic identity and habitat to modeling primary production here and elsewhere, and provide insight to how stream microbial mat communities are formed, maintained, and ultimately persist in an isolated polar desert.

}, keywords = {LTER-MCM, algae, Antarctica, biological sciences, climate change, Disturbance, earth sciences, McMurdo Dry Valleys, microbial mats}, url = {https://search.proquest.com/docview/1690497718?accountid=14503}, author = {Tyler J. Kohler}, editor = {Diane M. McKnight} } @article {3712, title = {Potential for real-time understanding of coupled hydrologic and biogeochemical processes in stream ecosystems: Future integration of telemetered data with process models for glacial meltwater streams}, journal = {Water Resources Research}, volume = {51}, year = {2015}, month = {08/2015}, pages = {6725 - 6738}, keywords = {LTER-MCM}, doi = {10.1002/2015WR017618}, url = {http://doi.wiley.com/10.1002/2015WR017618http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2F2015WR017618}, author = {Diane M. McKnight and Cozzetto, K and Cullis, James D.S. and Michael N. Gooseff and Chris Jaros and Koch, J. and W. Berry Lyons and Neupauer, R. M. and Wlostowski, Adam} } @article {3189, title = {Pressure-driven, shoreline currents in a perennially ice-covered, pro-glacial lake in Antarctica, identified from a LiCl tracer injected into a pro-glacial stream}, journal = {Hydrological Processes}, volume = {29}, year = {2015}, month = {05-2015}, pages = {2212 - 2231}, abstract = {

The distribution of streamwater within ice-covered lakes influences sub-ice currents, biological activity and shoreline morphology. Perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica, provide an excellent natural laboratory to study hydrologic\–limnologic interactions under ice cover. For a 2\ h period on 17 December 2012, we injected a lithium chloride tracer into Andersen Creek, a pro-glacial stream flowing into Lake Hoare. Over 4\ h, we collected 182 water samples from five stream sites and 15 ice boreholes. Geochemical data showed that interflow travelled West of the stream mouth along the shoreline and did not flow towards the lake interior. The chemistry of water from Andersen Creek was similar to the chemistry of water below shoreline ice. Additional evidence for Westward flow included the morphology of channels on the ice surface, the orientation of ripple marks in lake sediments at the stream mouth and equivalent temperatures between Andersen Creek and water below shoreline ice. Streamwater deflected to the right of the mouth of the stream, in the opposite direction predicted by the Coriolis force. Deflection of interflow was probably caused by the diurnal addition of glacial runoff and stream discharge to the Eastern edge of the lake, which created a strong pressure gradient sloping to the West. This flow directed stream momentum away from the lake interior, minimizing the impact of stream momentum on sub-ice currents. It also transported dissolved nutrients and suspended sediments to the shoreline region instead of the lake interior, potentially affecting biological productivity and bedform development.

}, keywords = {LTER-MCM}, doi = {10.1002/hyp.v29.910.1002/hyp.10352}, url = {http://doi.wiley.com/10.1002/hyp.v29.9http://doi.wiley.com/10.1002/hyp.10352}, author = {Castendyk, Devin and Diane M. McKnight and Kathleen A. Welch and Niebuhr, Spencer and Chris Jaros} } @mastersthesis {4084, title = {Quantifying long-term geomorphology of Antarctic streams}, volume = {MS}, year = {2015}, pages = {185}, school = {University of Colorado}, type = {masters}, address = {Boulder, CO}, abstract = {

In 1994, 16 stream transects were established in the McMurdo Dry Valleys of Antarctica beginning a long term data set characterizing microbial communities and channel geometry. The transects were established to record microbial mat dynamics and stream geomorphology. To accomplish this, the transects were surveyed for points of interest outside and inside the stream channel. Beginning in 2010 the microbial surveys received ground based LiDAR support. This allowed for greater resolution in mapping and analyzing stream morphology than traditional surveying methods. The purpose of this study was to overlap the traditional methods of surveying individual points of interest with a data cloud representing the entire stream transect to be able to continue the microbial study into the future unabated. Using surveyed microbial mats as an indicator of a location in time, a history of channel elevations was created for 7 transects. In general, the streams have not changed significantly in the 20 year record, with exceptions being the steep channel of Bohner Stream, and Huey Creek, which receives large sediment loads from the sharply incised upstream channel, both of which saw large variations in maximum bed change exceeding 75cm and 150 cm respectively. In addition to creating an elevation history, relative bed change was plotted against the ash free dry mass of the microbial mats sampled to determine the resilience of the mats. It was found that microbial mats are more abundant in areas of near zero change. The four microbial mats studied however, which include green, black, orange, and red mats, differed greatly in adaptability with regards to bed change. Green microbial mats, which are typically hidden under large immobile rocks, were not often found in areas with any significant bed change. Conversely, orange mats were found in the most dynamic parts of the stream bed with outliers seen in areas with change exceeding 50 cm with. Finally black microbial mats had the largest values of ash free dry mass indicating the largest resilience to the scouring effects of high flow.

}, keywords = {LTER-MCM}, url = {https://search.proquest.com/docview/1727444346?accountid=14503}, author = {Crisp, Steven W.}, editor = {Diane M. McKnight} } @article {3215, title = {Recovery of Antarctic stream epilithon from simulated scouring events}, journal = {Antarctic Science}, volume = {27}, year = {2015}, month = {Jan-08-2015}, pages = {341 - 354}, abstract = {

Microbial mats are common in polar streams and often dominate benthic biomass. Climate change may be enhancing the variability of stream flows in the Antarctic, but so far studies investigating mat responses to disturbance have been limited in this region. Mat regrowth was evaluated following disturbance by experimentally scouring rocks from an ephemeral McMurdo Dry Valley stream over two summers (2001\–02 and 2012\–13). Mats were sampled at the beginning and resampled at the end of the flow season. In 2012\–13, mats were additionally resampled mid-season along with previously undisturbed controls. In 2001\–02 rocks regained 47\% of chlorophyll\ aand 40\% of ash-free dry mass by the end of the summer, while in 2012\–13 rocks regrew 18\% and 27\%, respectively. Mat stoichiometry differed between summers, and reflected differences in biomass and discharge.\ Oscillatoria\ spp. were greatest on scoured rocks and\ Phormidium\ spp. on undisturbed rocks. Small diatoms\ Humidophila\ andFistulifera\ spp. increased throughout the summer in all mats, with the latter more abundant in scoured communities. Collectively, these data suggest that mats are variable intra-annually, responsive to hydrology and require multiple summers to regrow initial biomass once lost. These results will aid the interpretation of long-term data, as well as inform Antarctic Specially Managed Area protocols.

}, keywords = {LTER-MCM}, issn = {0954-1020}, doi = {10.1017/S0954102015000024}, url = {http://www.journals.cambridge.org/abstract_S0954102015000024}, author = {Tyler J. Kohler and Ethan Chatfield and Michael N. Gooseff and John E. Barrett and Diane M. McKnight} } @article {3222, title = {A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond}, journal = {Antarctic Science}, volume = {27}, year = {2015}, month = {Jan-02-2015}, pages = {3 - 18}, abstract = {

Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to \‘scan the horizon\’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone

}, keywords = {LTER-MCM}, issn = {0954-1020}, doi = {10.1017/S0954102014000674}, url = {http://www.journals.cambridge.org/abstract_S0954102014000674}, author = {Kennicutt, M.C. and Steven L. Chown and Cassano, J.J. and Liggett, D. and Lloyd S. Peck and Massom, R. and Rintoul, S.R. and Storey, J. and Vaughan, D.G. and Wilson, T.J. and Allison, I. and Ayton, J. and Badhe, R. and Baeseman, J. and Barrett, P.J. and Elanor R. Bell and Bertler, N. and Bo, S. and Brandt, A. and David Bromwich and Craig S Cary and Clark, M.S. and Peter Convey and Costa, E.S. and Cowan, D. and Deconto, R. and Dunbar, R. and Elfring, C. and Escutia, C. and Francis, J. and Fricker, H.A. and Fukuchi, M. and Gilbert, N. and Gutt, J. and Havermans, C. and Hik, D. and Hosie, G. and Jones, C. and Kim, Y.D. and Le Maho, Y. and Lee, S.H. and Leppe, M. and Leitchenkov, G. and Li, X. and Lipenkov, V. and Lochte, K. and L{\'o}pez-Mart{\'\i}nez, J. and {\"u}decke, C. and W. Berry Lyons and Marenssi, S. and Miller, H. and Morozova, P. and Naish, T. and Nayak, S. and Ravindra, R. and Retamales, J. and Ricci, C.A. and Rogan-Finnemore, M. and Ropert-Coudert, Y. and Samah, A.A. and Sanson, L. and Scambos, T. and I.R. Schloss and Shiraishi, K. and Siegert, M.J. and Sim{\~o}es, J.C. and Storey, B. and Sparrow, M.D. and Diana H. Wall and Walsh, J.C. and Wilson, G. and Winther, J.G. and J.C. Xavier and Yang, H. and Sutherland, W.J.} } @article {1056, title = {Ciliate diversity, community structure and novel taxa in lakes of the McMurdo Dry Valleys, Antarctica}, journal = {Biological Bulleting}, volume = {227}, year = {2014}, month = {10/2014}, pages = {175-190}, chapter = {175}, abstract = {We report an in-depth survey of next-generation DNA sequencing of ciliate diversity and community structure in two permanently ice-covered McMurdo Dry Valley lakes during the austral summer and autumn (November 2007 and March 2008). We tested hypotheses on the relationship between species richness and environmental conditions including environmental extremes, nutrient status, and day length. On the basis of the unique environment that exists in these high-latitude lakes, we expected that novel taxa would be present. Alpha diversity analyses showed that extreme conditions-that is, high salinity, low oxygen, and extreme changes in day length-did not impact ciliate richness; however, ciliate richness was 30\% higher in samples with higher dissolved organic matter. Beta diversity analyses revealed that ciliate communities clustered by dissolved oxygen, depth, and salinity, but not by season (i.e., day length). The permutational analysis of variance test indicated that depth, dissolved oxygen, and salinity had significant influences on the ciliate community for the abundance matrices of resampled data, while lake and season were not significant. This result suggests that the vertical trends in dissolved oxygen concentration and salinity may play a critical role in structuring ciliate communities. A PCR-based strategy capitalizing on divergent eukaryotic V9 hypervariable region ribosomal RNA gene targets unveiled two new genera in these lakes. A novel taxon belonging to an unknown class most closely related to Cryptocaryon irritans was also inferred from separate gene phylogenies.}, keywords = {LTER-MCM}, author = {Yuan, Xu and Trista J. Vick-Majors and Rachael M. Morgan-Kiss and John C. Priscu and Linda A. Amaral-Zettler} } @article {1067, title = {Diel flow pulses drive particulate organic matter transport from microbial mats in a glacial meltwater stream in the McMurdo Dry Valleys}, journal = {Water Resources Research}, volume = {50}, year = {2014}, month = {01/2014}, pages = {86-97}, chapter = {86}, abstract = { Many glacial meltwater streams in the McMurdo Dry Valleys (MDV) of Antarctica contain abundant microbial mats, representing hot spots of primary production in a barren landscape. These mats persist through the winter in a freeze-dried state and grow in the summer, experiencing a dynamic hydrologic regime as streamflow varies on a diel cycle and with weather conditions. During diel peaks in flow these streams transport particulate organic matter (POM) to the downstream closed-basin lakes. We investigated the spatial and temporal dynamics of POM transport derived from the scouring of microbial mats in Von Guerard Stream of the MDV. The results show clockwise hysteresis effects in POM concentration over diel flood pulses and suggests that POM transport in the MDVs is supply limited. Further studies are required to confirm this and to identify the potential contributing sources of POM. The hysteresis effect was modeled using an approach derived from models of sediment transport in streams. Spatial variations in POM transport indicate that patch-scale variations in bed shear stress and benthic biomass also influence transport which is integrated downstream over several 100{\textquoteright}s of meters. Large variations in the POM transport dynamics between different diel flood pulses were found to be related to the time since a resetting flood event and the regrowth of potentially mobile benthic biomass, providing further evidence of the importance of supply limitation and flow variability in controlling the organic matter flux of stream ecosystems.}, keywords = {LTER-MCM}, doi = {10.1002/2013WR014061}, author = {Cullis, James D.S. and Lee F. Stanish and Diane M. McKnight} } @mastersthesis {4094, title = {Ecology and biogeography of freshwater diatoms in ponds of McMurdo Dry Valleys and parts of the Ross Island}, volume = {M.S.}, year = {2014}, school = {University of Colorado}, type = {masters}, address = {Boulder, CO}, abstract = {

The McMurdo Dry Valleys (MDVs) and the exposed coastal areas of the nearby Ross Island in Antarctica represent some of the coldest, driest places in the world. However, during the austral summer warmer temperatures and constant sunlight allow microbial life to flourish nearly anywhere there is water. Diatoms are single-celled algae encapsulated in a silica shell and diatom communities constitute an important component of the microbial mats that grow in the streams, lakes and ponds in these regions. As part of the Long Term Ecological Research station in the McMurdo Dry Valleys diatom communities have been studied extensively in the streams over the last 20 years. Although the diatoms present in pond microbial mats at Cape Royds have been previously studied, modern-day knowledge of the characteristics of diatom communities in ponds and small lakes throughout the region is limited. This work sought to find the relationships between water chemistry and diatom community structure in ponds. Because water flow is not a factor in ponds and small lakes, influences of salinity, nutrients, pH and other factors can be more easily distinguished. This study looked at 24 separate bodies of water in the Taylor Valley, Labyrinth region in Wright Valley, Cape Royds and McMurdo Station area on Ross Island. The results suggest that geography, dispersal and historical environmental conditions play a significant role in structuring diatom communities, in addition to water chemistry. The results also expand the knowledge of habitat preferences for some of the species present in this region.

}, keywords = {LTER-MCM, biological sciences, freshwater diatoms, health and environmental sciences, McMurdo Dry Valleys, ponds}, url = {https://search.proquest.com/docview/1655818365?accountid=14503}, author = {Sakaeva, A.}, editor = {Diane M. McKnight} } @phdthesis {4170, title = {Environmental impacts on RubisCO from green algal laboratory isolates to Antarctic lake communities}, volume = {Ph.D.}, year = {2014}, month = {2014}, school = {Miami University}, type = {doctoral}, address = {Oxford, OH}, abstract = {

Ribulose-1,5-bisphosphate carboxylase oxygenase (RubisCO) is found in a variety of autotrophic microorganisms ranging from green algae, cyanobacteria, and chemoautotrophic bacteria. As this enzyme has the potential to catalyze carboxylation (carbon fixation) or oxygenation (photorespiration) reactions, it is regulated in response to environmental variables at the levels of transcription, translation, and post-translation by the enzyme, RubisCO activase. A combination of laboratory experiments on green algal isolates and field experiments were utilized to gain insight on carbon fixation in permanently ice-covered Antarctic lakes. RubisCO was investigated as a potential target for cold adaptation of carbon fixation in the psychrophilic green alga, Chlamydomonas raudensis UWO241 (UWO241), isolated from Lake Bonney, Antarctica. RubisCO activity, stability, and whole cell carbon fixation were measured for the psychrophile and compared to a closely related mesophilic alga, C. raudensis SAG49.72 (SAG49.72). The effect of environmental factors including light and temperature on UWO241 and SAG49.72 RubisCO activation state, an indirect measurement of RubisCO activase activity, and abundance was investigated using a modified RubisCO carboxylase assay and immunoblotting, respectively. Lastly, maximum potential RubisCO carboxylase activity was determined using a modified activity assay in multiple ice covered Antarctic lakes including Lake Bonney. This data was complemented with lake depth profiles of enzyme abundance determined by quantitative real-time PCR and RubisCO-harboring organism diversity. While purified RubisCO of the psychrophilic green alga did not function optimally at low temperature, whole cell carbon fixation was greater under such conditions, suggesting that the overall process of carbon fixation is modified to function in UWO241. Increased RubisCO abundance at low temperature may contribute to this phenomenon. Low light levels may be important in regulation of RubisCO via RubisCO activase and should be further investigated. Based on community level RubsiCO activity and enzyme abundance, light and RubisCO harboring organisms including eukaryotic algae and cyanobacteria were positively correlated, but this was variable between lakes. Dark carbon fixation was potentially important in lakes west lobe Bonney and Fryxell and this community was negatively correlated with light. Results of targeted physiology and community level experiments led to development of a carbon fixation model for Lake Bonney.

}, keywords = {LTER-MCM, carbon fixation, green algae, ice-covered lakes, RubisCO}, url = {http://rave.ohiolink.edu/etdc/view?acc_num=miami1407056783}, author = {Jenna M. Dolhi and Rachael M. Morgan-Kiss} } @article {1062, title = {Radiocarbon abundance and reservoir effects in lakes of the McMurdo Dry Valleys, Antarctica}, journal = {Limnology and Oceanography}, volume = {59}, year = {2014}, month = {05/2014}, pages = {811-826}, chapter = {811}, keywords = {LTER-MCM}, author = {Peter T. Doran and Kenig, Fabien and Lawson Knoepfle and Jill A. Mikucki and W. Berry Lyons} } @article {3219, title = {The spatial structure of Antarctic biodiversity}, journal = {Ecological Monographs}, volume = {84}, year = {2014}, month = {05/2014}, pages = {203 - 244}, abstract = {

Patterns of environmental spatial structure lie at the heart of the most fundamental and familiar patterns of diversity on Earth. Antarctica contains some of the strongest environmental gradients on the planet and therefore provides an ideal study ground to test hypotheses on the relevance of environmental variability for biodiversity. To answer the pivotal question, \“How does spatial variation in physical and biological environmental properties across the Antarctic drive biodiversity?\” we have synthesized current knowledge on environmental variability across terrestrial, freshwater, and marine Antarctic biomes and related this to the observed biotic patterns. The most important physical driver of Antarctic terrestrial communities is the availability of liquid water, itself driven by solar irradiance intensity. Patterns of biota distribution are further strongly influenced by the historical development of any given location or region, and by geographical barriers. In freshwater ecosystems, free water is also crucial, with further important influences from salinity, nutrient availability, oxygenation, and characteristics of ice cover and extent. In the marine biome there does not appear to be one major driving force, with the exception of the oceanographic boundary of the Polar Front. At smaller spatial scales, ice cover, ice scour, and salinity gradients are clearly important determinants of diversity at habitat and community level. Stochastic and extreme events remain an important driving force in all environments, particularly in the context of local extinction and colonization or recolonization, as well as that of temporal environmental variability. Our synthesis demonstrates that the Antarctic continent and surrounding oceans provide an ideal study ground to develop new biogeographical models, including life history and physiological traits, and to address questions regarding biological responses to environmental variability and change.

}, keywords = {LTER-MCM}, issn = {0012-9615}, doi = {10.1890/12-2216.1}, url = {http://www.esajournals.org/doi/abs/10.1890/12-2216.1}, author = {Peter Convey and Steven L. Chown and Clarke, Andrew and Barnes, David K. A. and Bokhorst, Stef and Vonda Cummings and Hugh W. Ducklow and Francesco Frati and Green, T. G. Allan and Shulamit Gordon and Griffiths, Huw J. and Clive Howard-Williams and Huiskes, Ad H. L. and Johanna Laybourn-Parry and W. Berry Lyons and McMinn, Andrew and Morley, Simon A. and Lloyd S. Peck and Quesada, Antonio and Robinson, Sharon A. and Schiaparelli, Stefano and Diana H. Wall} } @article {3206, title = {Spring thaw ionic pulses boost nutrient availability and microbial growth in entombed Antarctic Dry Valley cryoconite holes}, journal = {Frontiers in Microbiology}, volume = {5}, year = {2014}, month = {12/2014}, abstract = {

The seasonal melting of ice entombed cryoconite holes on McMurdo Dry Valley glaciers provides oases for life in the harsh environmental conditions of the polar desert where surface air temperatures only occasionally exceed 0\°C during the Austral summer. Here we follow temporal changes in cryoconite hole biogeochemistry on Canada Glacier from fully frozen conditions through the initial stages of spring thaw toward fully melted holes. The cryoconite holes had a mean isolation age from the glacial drainage system of 3.4 years, with an increasing mass of aqueous nutrients (dissolved organic carbon, total nitrogen, total phosphorus) with longer isolation age. During the initial melt there was a mean nine times enrichment in dissolved chloride relative to mean concentrations of the initial frozen holes indicative of an ionic pulse, with similar mean nine times enrichments in nitrite, ammonium, and dissolved organic matter. Nitrate was enriched twelve times and dissolved organic nitrogen six times, suggesting net nitrification, while lower enrichments for dissolved organic phosphorus and phosphate were consistent with net microbial phosphorus uptake. Rates of bacterial production were significantly elevated during the ionic pulse, likely due to the increased nutrient availability. There was no concomitant increase in photosynthesis rates, with a net depletion of dissolved inorganic carbon suggesting inorganic carbon limitation. Potential nitrogen fixation was detected in fully melted holes where it could be an important source of nitrogen to support microbial growth, but not during the ionic pulse where nitrogen availability was higher. This study demonstrates that ionic pulses significantly alter the timing and magnitude of microbial activity within entombed cryoconite holes, and adds credence to hypotheses that ionic enrichments during freeze-thaw can elevate rates of microbial growth and activity in other icy habitats, such as ice veins and subglacial regelation zones

}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2014.00694}, url = {http://journal.frontiersin.org/article/10.3389/fmicb.2014.00694/abstract}, author = {Telling, J. and Alexandre M. Anesio and Martyn Tranter and Andrew G Fountain and Thomas H. Nylen and Hawkings, Jon and Singh, Virendra B. and Kaur, Preeti and Musilova, Michaela and Wadham, J. L.} } @article {1091, title = {Accelerated thermokarst formation in the McMurdo Dry Valleys, Antarctica}, journal = {Scientific Reports}, volume = {3}, year = {2013}, month = {07/2013}, keywords = {LTER-MCM}, doi = {10.1038/srep02269}, url = {http://www.nature.com/srep/2013/130724/srep02269/full/srep02269.html?WT.ec_id=SREP-20130730}, author = {Joseph S. Levy and Andrew G Fountain and Dickson, James L. and Head, James W. and Okal, Marianne and Marchant, David R. and Watters, Jaclyn} } @article {3217, title = {Antarctic Thresholds - Ecosystem Resilience and Adaptation (AnT-ERA), a new SCAR-biology programme}, journal = {Polarforschung}, volume = {82}, year = {2013}, month = {10/2013}, pages = {147-150.}, chapter = {147}, abstract = {

Stresses on Antarctic ecosystems result from environmental change, including extreme events, and from (other) human impacts. Consequently, Antarctic habitats are changing, some at a rapid pace while others are relatively stable. A cascade of responses from molecular through organismic to the community level are expected. The differences in biological complexity and evolutionary histories between both polar regions and the rest of the planet suggest that stresses on polar ecosystem function may have fundamentally different outcomes from those at lower latitudes. Polar ecosystem processes are therefore key to informing wider ecological debate about the nature of stability and potential changes across the biosphere. The main goal of AnT-ERA is to facilitate the science required to examine changes in biological processes in Antarctic and sub-Antarctic marine-, freshwater and terrestrial ecosystems. Tolerance limits, as well as thresholds, resistance and resilience to environmental change will be determined. AnT-ERA is classified into three overlapping themes, which represent three levels of biological organisation: (1) molecular and physiological performance, (2) population processes and species traits, (3) ecosystem function and services.

}, keywords = {LTER-MCM}, url = {http://epic.awi.de/34238/1/Polarforschung_82-2_147-150.pdf}, author = {Gutt, J. and Byron Adams and T Bracegirdle and Cowan, D. and Vonda Cummings and di Prisco, G. and Gradinger, R. and Isla, E. and McIntyre, T. and Murphy, E and Lloyd S. Peck and I.R. Schloss and Smith, C. and Suckling, C. C. and Takahashi, A. and Diana H. Wall and J.C. Xavier} } @article {3211, title = {Carbon Sequestration and Release from Antarctic Lakes: Lake Vida and West Lake Bonney (McMurdo Dry Valleys)}, journal = {Aquatic Geochemistry}, volume = {19}, year = {2013}, month = {03/2013}, pages = {135 - 145}, abstract = {

Perennial ice covers on many Antarctic lakes have resulted in high lake inorganic carbon contents. The objective of this paper was to evaluate and compare the brine and CO2\ chemistries of Lake Vida (Victoria Valley) and West Lake Bonney (Taylor Valley), two lakes of the McMurdo Dry Valleys (East Antarctica), and their potential consequences during global warming. An existing geochemical model (FREZCHEM-15) was used to convert measured molarity into molality needed for the FREZCHEM model, and this model added a new algorithm that converts measured DIC into carbonate alkalinity needed for the FREZCHEM model. While quite extensive geochemical information exists for ice-covered Taylor Valley lakes, such as West Lake Bonney, only limited information exists for the recently sampled brine of \>25\ m ice-thick Lake Vida. Lake Vida brine had a model-calculated pCO2\ =\ 0.60 bars at the field pH (6.20); West Lake Bonney had a model-calculated pCO2\ =\ 5.23\ bars at the field pH (5.46). Despite the high degree of atmospheric CO2supersaturation in West Lake Bonney, it remains significantly undersaturated with the gas hydrate, CO2\·6H2O, unless these gas hydrates are deep in the sediment layer or are metastable having formed under colder temperatures or greater pressures. Because of lower temperatures, Lake Vida could start forming CO2\·6H2O at lower pCO2\ values than West Lake Bonney; but both lakes are significantly undersaturated with the gas hydrate, CO2\·6H2O. For both lakes, simulation of global warming from current subzero temperatures (\−13.4\ \°C in Lake Vida and \−4.7\ \°C in West Lake Bonney) to 10\ \°C has shown that a major loss of solution-phase carbon as CO2\ gases and carbonate minerals occurred when the temperatures rose above 0\ \°C and perennial ice covers would disappear. How important these Antarctic CO2\ sources will be for future global warming remains to be seen. But a recent paper has shown that methane increased in atmospheric concentration due to deglaciation about 10,000\ years ago. So, CO2\ release from ice lakes might contribute to atmospheric gases in the future.

}, keywords = {LTER-MCM}, issn = {1380-6165}, doi = {10.1007/s10498-012-9184-1}, url = {http://link.springer.com/10.1007/s10498-012-9184-1http://link.springer.com/content/pdf/10.1007/s10498-012-9184-1}, author = {G. M. Marion and A. E. Murray and Wagner, Bernd and Christian H. Fritsen and Kenig, Fabien and Peter T. Doran} } @article {1093, title = {The carbon stable isotope biogeochemistry of streams, Taylor Valley, Antarctica}, journal = {Applied Geochemistry}, volume = {32}, year = {2013}, month = {05/2013}, pages = {26 - 36}, keywords = {LTER-MCM}, doi = {10.1016/j.apgeochem.2012.08.019}, author = {W. Berry Lyons and Leslie, D.L. and Harmon, R.S. and Klaus Neumann and Kathleen A. Welch and Bisson, K. M. and Diane M. McKnight} } @article {1077, title = {Characterization of fulvic acid fractions of dissolved organic matter during ice-out in a hyper-eutrophic, coastal pond in Antarctica}, journal = {Environmental Research Letters}, volume = {8}, year = {2013}, month = {12/2013}, pages = {045015}, abstract = {Dissolved humic material (HDOM) is ubiquitous to all natural waters and its source material influences its chemical structure, reactivity, and bioavailability. While terrestrially derived HDOM reference materials distributed by the International Humic Substances Society (IHSS) have been readily available to engineering and scientific communities, a microbially derived reference HDOM was not, despite the well-characterized differences in the chemistry and reactivity of HDOM derived from terrestrial versus microbial sources. To address this gap, we collected a microbial reference fulvic acid from Pony Lake (PLFA) for distribution through the IHSS. Pony Lake is a saline coastal pond on Ross Island, Antarctica, where the landscape is devoid of terrestrial plants. Sample collection occurred over a 17-day period in the summer season at Pony Lake. During this time, the dissolved organic carbon (DOC) concentrations increased nearly two-fold, and the fulvic acid fraction (collected using the XAD-8 method) accounted for 14.6\% of the DOC. During the re-concentration and desalting procedures we isolated two other chemically distinct fulvic acid fractions: (1) PLFA-2, which was high in carbohydrates and (2) PLFA-CER, which was high in nitrogen. The chemical characteristics (elemental analysis, optical characterization with UV{\textendash}vis and fluorescence spectroscopy, and 13C NMR spectroscopy) of the three fulvic acid fractions helped to explain their behavior during isolation.}, keywords = {LTER-MCM}, doi = {10.1088/1748-9326/8/4/045015}, author = {Kaelin M. Cawley and Diane M. McKnight and Penney L. Miller and Rose M. Cory and Fimmen, Ryan L and Guerard, Jennifer and Markus Dieser and Chris Jaros and Yu-Ping Chin and Christine M. Foreman} } @article {1078, title = {Characterization of IHSS Pony Lake fulvic acid dissolved organic matter by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and fluorescence spectroscopy}, journal = {Organic Geochemistry}, volume = {65}, year = {2013}, month = {12/2013}, pages = {19 - 28}, keywords = {LTER-MCM}, doi = {10.1016/j.orggeochem.2013.09.013}, url = {http://www.sciencedirect.com/science/article/pii/S0146638013002167}, author = {D{\textquoteright}Andrilli, Juliana and Christine M. Foreman and Marshall, Alan G. and Diane M. McKnight} } @article {1074, title = {CORRIGENDUM: Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth{\textquoteright}s most saline lake and implications for Mars}, journal = {Scientific Reports}, volume = {3}, year = {2013}, month = {3/2013}, keywords = {LTER-MCM}, doi = {10.1038/srep01424}, author = {Dickson, James L. and Head, James W. and Joseph S. Levy and Marchant, David R.} } @article {1097, title = {Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth{\textquoteright}s most saline lake and implications for Mars}, journal = {Scientific Reports}, volume = {3}, year = {2013}, month = {01/2013}, keywords = {LTER-MCM}, doi = {10.1038/srep01166}, url = {http://www.nature.com/srep/2013/130130/srep01166/full/srep01166.html?WT.ec_id=SREP-704-20130201}, author = {Dickson, James L. and Head, James W. and Joseph S. Levy and Marchant, David R.} } @article {1079, title = {Environmental factors influencing diatom communities in Antarctic cryoconite holes}, journal = {Environmental Research Letters}, volume = {8}, year = {2013}, month = {12/2013}, pages = {045006}, keywords = {LTER-MCM}, doi = {10.1088/1748-9326/8/4/045006}, url = {http://iopscience.iop.org/1748-9326/8/4/045006/pdf/1748-9326_8_4_045006.pdf}, author = {Lee F. Stanish and Bagshaw, Elizabeth and Diane M. McKnight and Andrew G Fountain and Martyn Tranter} } @article {1087, title = {The influence of stream thermal regimes and preferential flow paths on hyporheic exchange in a glacial meltwater stream}, journal = {Water Resources Research}, volume = {49}, year = {2013}, month = {09/2013}, pages = {5552 - 5569}, keywords = {LTER-MCM}, doi = {10.1002/wrcr.20410}, url = {http://onlinelibrary.wiley.com/doi/10.1002/wrcr.20410/pdf}, author = {Cozzetto, K and Kenneth E. Bencala and Michael N. Gooseff and Diane M. McKnight} } @article {1088, title = {Microbial growth under humic-free conditions in a supraglacial stream system on the Cotton Glacier, Antarctica}, journal = {Environmental Research Letters}, volume = {8}, year = {2013}, month = {09/2013}, pages = {035022}, abstract = {During the austral summers of 2004 and 2009, we sampled a supraglacial stream on the Cotton Glacier, Antarctica. The stream dissolved organic matter (DOM) was low (44{\textendash}48 μM C) and lacked detectable humic fluorescence signatures. Analysis of the excitation emissions matrices (EEMs) indicated that amino-acid fluorophores dominated, consistent with DOM of microbial origin, with little humic-like fluorescence. In most aquatic ecosystems, humic DOM attenuates harmful UV radiation and its absence may represent an additional stressor influencing the microbial community. Nonetheless, the stream contained an active microbial assemblage with bacterial cell abundances from 2.94 {\texttimes} 104 to 4.97 {\texttimes} 105 cells ml-1, and bacterial production ranging from 58.8 to 293.2 ng C l-1 d-1. Chlorophyll-a concentrations ranged from 0.3 to 0.53 μg l-1 indicating that algal phototrophs were the probable source of the DOM. Microbial isolates produced a rainbow of pigment colors, suggesting adaptation to stress, and were similar to those from other cryogenic systems (Proteobacteria and Bacteroidetes lineages). Supraglacial streams provide an example of contemporary microbial processes on the glacier surface and a natural laboratory for studying microbial adaptation to the absence of humics.}, keywords = {LTER-MCM}, doi = {10.1088/1748-9326/8/3/035022}, url = {http://iopscience.iop.org/1748-9326/8/3/035022}, author = {Christine M. Foreman and Rose M. Cory and Morris, Cindy E and Michael D. SanClements and Smith, Heidi J and John T. Lisle and Penney L. Miller and Yu-Ping Chin and Diane M. McKnight} } @article {1081, title = {Physicochemical and biological dynamics in a coastal Antarctic lake as it transitions from frozen to open water}, journal = {Antarctic Science}, volume = {25}, year = {2013}, month = {12/2013}, pages = {663{\textendash}675}, keywords = {LTER-MCM}, author = {Markus Dieser and Christine M. Foreman and Chris Jaros and John T. Lisle and Mark C. Greenwood and Johanna Laybourn-Parry and Penney L. Miller and Yu-Ping Chin and Diane M. McKnight} } @article {1105, title = {Antarctic Tardigrada: a first step in understanding molecular operational taxonomic units (MOTUs) and biogeography of cryptic meiofauna}, journal = {Invertebrate Systematics}, volume = {26}, year = {2012}, month = {12/2012}, pages = {526}, keywords = {LTER-MCM}, doi = {10.1071/IS12034}, author = {Czechowski, Paul and Sands, Chester J. and Byron Adams and D{\textquoteright}Haese, Cyrille A. and John A. E. Gibson and McInnes, Sandra J. and Stevens, Mark I.} } @article {3534, title = {At Limits of Life: Multidisciplinary Insights Reveal Environmental Constraints on Biotic Diversity in Continental Antarctica}, journal = {PLoS ONE}, volume = {7}, year = {2012}, month = {Jul-09-2013}, pages = {e44578}, abstract = {

Multitrophic communities that maintain the functionality of the extreme Antarctic terrestrial ecosystems, while the simplest of any natural community, are still challenging our knowledge about the limits to life on earth. In this study, we describe and interpret the linkage between the diversity of different trophic level communities to the geological morphology and soil geochemistry in the remote Transantarctic Mountains (Darwin Mountains, 80\°S). We examined the distribution and diversity of biota (bacteria, cyanobacteria, lichens, algae, invertebrates) with respect to elevation, age of glacial drift sheets, and soil physicochemistry. Results showed an abiotic spatial gradient with respect to the diversity of the organisms across different trophic levels. More complex communities, in terms of trophic level diversity, were related to the weakly developed younger drifts (Hatherton and Britannia) with higher soil C/N ratio and lower total soluble salts content (thus lower conductivity). Our results indicate that an increase of ion concentration from younger to older drift regions drives a succession of complex to more simple communities, in terms of number of trophic levels and diversity within each group of organisms analysed. This study revealed that integrating diversity across multi-trophic levels of biotic communities with abiotic spatial heterogeneity and geological history is fundamental to understand environmental constraints influencing biological distribution in Antarctic soil ecosystems.

}, keywords = {LTER-MCM}, doi = {10.1371/journal.pone.0044578}, url = {http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044578}, author = {Magalhaes, Catarina and Stevens, Mark I. and Craig S Cary and Ball, Becky and Storey, Bryan C. and Diana H. Wall and T{\"u}rk, Roman and Ruprecht, Ulrike}, editor = {de Bello, Francesco} } @article {1115, title = {Bacteria and diatom co-occurrence patterns in microbial mats from polar desert streams}, journal = {Environmental Microbiology}, year = {2012}, month = {10/2012}, keywords = {LTER-MCM}, doi = {10.1111/j.1462-2920.2012.02872.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1462-2920.2012.02872.x/abstract}, author = {Lee F. Stanish and Sean P. O{\textquoteright}Neill and Antonio Gonz{\'a}lez and Teresa M. Legg and Joseph Knelman and Diane M. McKnight and Sarah A. Spaulding and Diana R. Nemergut} } @article {3535, title = {Challenges to the Future Conservation of the Antarctic}, journal = {Science}, volume = {337}, year = {2012}, month = {Jan-07-2013}, pages = {158 - 159}, abstract = {

The Antarctic Treaty System, acknowledged as a successful model of cooperative regulation of one of the globe\&$\#$39;s largest commons (1), is under substantial pressure. Concerns have been raised about increased stress on Antarctic systems from global environmental change and growing interest in the region\&$\#$39;s resources (2,\ 3). Although policy-makers may recognize these challenges, failure to respond in a timely way can have substantial negative consequences. We provide a horizon scan, a systematic means for identifying emerging trends and assisting decision-makers in identifying policies that address future challenges (2,\ 3). Previous analyses of conservation threats in the Antarctic have been restricted to matters for which available evidence is compelling (4). We reconsider these concerns because they might escalate quickly, judging from recent rapid environmental change in parts of Antarctica and increasing human interest in the region (see the map). We then focus on a more distant time horizon.

}, keywords = {LTER-MCM}, issn = {0036-8075}, doi = {10.1126/science.1222821}, url = {http://www.sciencemag.org/cgi/doi/10.1126/science.1222821}, author = {Steven L. Chown and Lee, J. E. and Hughes, K. A. and Barnes, J. and Barrett, P.J. and D.M. Bergstrom and Convey, P. and Cowan, Don A. and Crosbie, K. and Dyer, G. and Frenot, Y. and Grant, S. M. and Herr, D. and Kennicutt, M. C. and Lamers, M. and Murray, A. and Possingham, H. P. and Reid, K. and Riddle, M. J. and Ryan, P. G. and Sanson, L. and Shaw, J. D. and Sparrow, M.D. and Summerhayes, C. and Terauds, A. and Diana H. Wall} } @article {1106, title = {Chemical analysis of ice vein microenvironments: II. Analysis of glacial samples from Greenland and Antarctica}, journal = {Journal of Glaciology}, volume = {58}, year = {2012}, month = {12/2012}, pages = {1109 - 1118}, keywords = {LTER-MCM}, doi = {10.3189/2012JoG12J112}, url = {http://www.montana.edu/priscu/DOCS/Publications/BarlettaEtAl2012IceVein.pdf}, author = {Barletta, Robert E. and John C. Priscu and Mader, Heidy M. and Jones, Warren L. and Roe, Christopher H.} } @article {1109, title = {Cyanobacterial diversity across landscape units in a polar desert: Taylor Valley, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {82}, year = {2012}, month = {11/2012}, pages = {268 - 278}, keywords = {LTER-MCM}, doi = {10.1111/j.1574-6941.2012.01297.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2012.01297.x/full}, author = {Alexander B. Michaud and Marie {\v S}aback{\'a} and John C. Priscu} } @article {1118, title = {Diversity and Expression of RubisCO Genes in a Perennially Ice-Covered Antarctic Lake during the Polar Night Transition}, journal = {Applied and Environmental Microbiology}, volume = {78}, year = {2012}, month = {04/2012}, pages = {4358-4366}, keywords = {LTER-MCM}, url = {http://aem.asm.org/content/78/12/4358.short}, author = {Weidong Kong and David C. Ream and John C. Priscu and Rachael M. Morgan-Kiss} } @article {1122, title = {The ecology of pulse events: insights from an extreme climatic event in a polar desert ecosystem}, journal = {Ecosphere}, volume = {3}, year = {2012}, month = {02/2012}, pages = {art17}, keywords = {LTER-MCM}, doi = {10.1890/ES11-00325.1}, url = {http://www.esajournals.org/doi/abs/10.1890/ES11-00325.1}, author = {Uffe N. Nielsen and Diana H. Wall and Byron Adams and Ross A. Virginia and Ball, Becky and Michael N. Gooseff and Diane M. McKnight} } @article {1110, title = {Evidence of form II RubisCO ( cbbM) in a perennially ice-covered Antarctic lake}, journal = {FEMS Microbiology Ecology}, volume = {82}, year = {2012}, month = {11/2012}, pages = {491 - 500}, keywords = {LTER-MCM}, doi = {10.1111/j.1574-6941.2012.01431.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2012.01431.x/full}, author = {Weidong Kong and Jenna M. Dolhi and Amy Chiuchiolo and John C. Priscu and Rachael M. Morgan-Kiss} } @article {1116, title = {Extreme streams: flow intermittency as a control on diatom communities in meltwater streams in the McMurdo Dry Valleys, Antarctica}, journal = {Canadian Journal of Fisheries and Aquatic Sciences}, volume = {69}, year = {2012}, month = {08/2012}, pages = {1405 - 1419}, keywords = {LTER-MCM}, doi = {10.1139/f2012-022}, url = {http://www.nrcresearchpress.com/doi/abs/10.1139/f2012-022$\#$.UH2NlWcnq9g}, author = {Lee F. Stanish and Tyler J. Kohler and Rhea M.M. Esposito and Breana L. Simmons and Uffe N. Nielsen and Diana H. Wall and Diana R. Nemergut and Diane M. McKnight} } @article {1104, title = {The geochemistry of upland ponds, Taylor Valley, Antarctica}, journal = {Antarctic Science}, volume = {24}, year = {2012}, month = {2/2012}, pages = {3 - 14}, keywords = {LTER-MCM}, doi = {10.1017/S0954102011000617}, url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online\&aid=8483351}, author = {W. Berry Lyons and Kathleen A. Welch and Christopher B. Gardner and Chris Jaros and Daryl L. Moorhead and Knoepfle, J and Peter T. Doran} } @article {3528, title = {Microbial life at -13 ~C in the brine of an ice-sealed Antarctic lake}, journal = {Proceedings of the National Academy of Sciences}, volume = {109}, year = {2012}, month = {12/2012}, pages = {20626 - 20631}, keywords = {LTER-MCM}, issn = {0027-8424}, doi = {10.1073/pnas.1208607109}, url = {http://www.pnas.org/cgi/doi/10.1073/pnas.1208607109}, author = {A. E. Murray and Kenig, Fabien and Christian H. Fritsen and Christopher P. McKay and Kaelin M. Cawley and R. L. Edwards and Kuhn, Emanuele and Diane M. McKnight and Nathaniel E Ostrom and Vivian Peng and Adrian Ponce and John C. Priscu and Samarkin, Vladimir A. and Ashley T Townsend and Protima Wagh and Seth A Young and Pung To Yung and Peter T. Doran} } @book {1123, title = {Poisson Reconstruction of Extreme Submersed Environments: The ENDURANCE Exploration of an Under-Ice Antarctic Lake}, series = {Advances in Visual Computing. ISVC 2012. Lecture Notes in Computer Science.}, volume = {7431}, year = {2012}, pages = {394 - 403}, publisher = {Springer Berlin Heidelberg}, organization = {Springer Berlin Heidelberg}, address = {Berlin, Heidelberg}, abstract = {

We evaluate the use of Poisson reconstruction to generate a 3D bathymetric model of West Lake Bonney, Antarctica. The source sonar dataset has been collected by the ENDURANCE autonomous ve- hicle in the course of two Antarctic summer missions. The reconstruction workflow involved processing 200 million datapoints to generate a high resolution model of the lake bottom, Narrows region and underwater glacier face. A novel and flexible toolset has been developed to automate the processing of the Bonney data.

}, keywords = {LTER-MCM}, isbn = {978-3-642-33179-4}, doi = {10.1007/978-3-642-33179-4_38}, url = {http://www.springerlink.com/content/hg97w43588229087/}, author = {Alessandro Febretti and Kristof Richmond and Gulati, Shilpa and Flesher, Christopher and Hogan, Bartholomew P. and Andrew Johnson and Stone, William C. and John C. Priscu and Peter T. Doran}, editor = {Bebis, George and Boyle, Richard and Parvin, Bahram and Koracin, Darko and Fowlkes, Charless and Wang, Sen and Choi, Min-Hyung and Mantler, Stephan and Schulze, J{\"u}rgen and Acevedo, Daniel and Mueller, Klaus and Papka, Michael} } @article {1130, title = {15N and 13C{14N} NMR investigation of the major nitrogen-containing segment in an aquatic fulvic acid: Evidence for a hydantoin derivative}, journal = {Magnetic Resonance in Chemistry}, volume = {49}, year = {2011}, month = {12/2011}, pages = {775 - 780}, keywords = {LTER-MCM}, doi = {10.1002/mrc.2816}, author = {Xiaowen Fang and Jingdong Mao and Rose M. Cory and Diane M. McKnight and Klaus Schmidt-Rohr} } @article {1140, title = {Determination of Dissolved Oxygen in the Cryosphere: A Comprehensive Laboratory and Field Evaluation of Fiber Optic Sensors}, journal = {Environmental Science \& Technology}, volume = {45}, year = {2011}, month = {01/2011}, pages = {700 - 705}, keywords = {LTER-MCM}, doi = {10.1021/es102571j}, author = {Bagshaw, Elizabeth and Wadham, J. L. and Mowlem, M. and Martyn Tranter and Eveness, J. and Andrew G Fountain and Telling, J.} } @phdthesis {4095, title = {Ecological controls on stream diatom communities in the McMurdo Dry Valleys, Antarctica}, volume = {Ph.D.}, year = {2011}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Diatoms are vital primary producers in aquatic ecosystems and useful indicators of environmental change. In climatically sensitive polar areas, diatoms have been used as beacons of climate change, allowing us to monitor physical, chemical, and biological changes. This research aims to improve our understanding of diatom ecology in the pristine and dynamic McMurdo Dry Valleys of Antarctica, where diatoms reside in stream microbial mats. These results aid in understanding how changes in hydrologic regime will affect stream microbial communities, biodiversity, and ecosystem function in a changing environment.

Relationships between hydrologic regime and diatom community composition were investigated using long-term data. Diatom communities were structured by stream physical features, and streams with more similar hydrologic characteristics had more similar communities. Variation in diatom community composition was best explained by hydrologic regime. Small diatoms increased in relative abundances with increasing streamflow, suggesting a role of diatom size in structuring communities. Overall, diatom communities were resistant to flood and drought-like conditions, suggesting an adaptation to frequent disturbances.

The importance of hydrologic regime on drift activity was investigated during three 24- hour experiments. Diel variations in drift could be attributed to diurnal flow peaks. Biomass and diatom cell densities followed a clockwise pattern with stream discharge and support the dominant role of hydraulic processes. The quality of source material differed between seasons and throughout the day. Drifting diatom communities were dominated by\ Fistulifera pelliculosa, which is rarely found in stream mats and suggests a different source. Modeling results suggest that the less firmly anchored marginal mats contribute more to the drift than channel mats in low- flow seasons, while the channel mats become more important during high-flow seasons.

The relationships between diatom and bacterial assemblages in microbial mats were assessed based on phylogenetic and functional relatedness in five Dry Valley streams. Significant relationships between diatom and bacterial communities were found, and co-occurrence analysis identified numerous correlations between individual diatom and bacterial taxa. A consistency in metabolic lifestyles of correlated taxa suggests that the relationships are ecologically relevant. Diatom and bacterial diversity showed opposite patterns, which indicate differences in environmental drivers of diversity for bacteria and eukaryotes.

}, keywords = {LTER-MCM, Antarctica, biological sciences, community ecology, diatoms, earth sciences, McMurdo Dry Valleys, streams}, url = {https://search.proquest.com/docview/915694114?accountid=14503}, author = {Lee F. Stanish}, editor = {Diane M. McKnight} } @article {1137, title = {High-resolution monitoring reveals dissolved oxygen dynamics in an Antarctic cryoconite hole}, journal = {Hydrological Processes}, volume = {25}, year = {2011}, month = {08/2011}, pages = {2868 - 2877}, keywords = {LTER-MCM}, doi = {10.1002/hyp.8049}, author = {Bagshaw, Elizabeth and Martyn Tranter and Wadham, J. L. and Andrew G Fountain and Mowlem, M.} } @article {1127, title = {The Holocene environmental history of Lake Hoare, Taylor Valley, Antarctica, reconstructed from sediment cores}, journal = {Antarctic Science}, volume = {23}, year = {2011}, month = {6/2011}, pages = {307 - 319}, keywords = {LTER-MCM}, doi = {10.1017/S0954102011000125}, url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online\&aid=8275374}, author = {Wagner, Bernd and Ortlepp, Sabrina and Peter T. Doran and Kenig, Fabien and Melles, Martin and Andy Burkemper} } @article {1131, title = {Hydrologic processes influence diatom community composition in Dry Valley streams}, journal = {Journal of the North American Benthological Society}, volume = {30}, year = {2011}, month = {12/2011}, pages = {1057-1073}, keywords = {LTER-MCM}, doi = {10.1899/11-008.1}, url = {http://www.jnabs.org/doi/abs/10.1899/11-008.1}, author = {Lee F. Stanish and Diana R. Nemergut and Diane M. McKnight} } @article {1135, title = {Hydrological Connectivity of the Landscape of the McMurdo Dry Valleys, Antarctica}, journal = {Geography Compass}, volume = {5}, year = {2011}, month = {09/2011}, pages = {666 - 681}, keywords = {LTER-MCM}, doi = {10.1111/j.1749-8198.2011.00445.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1749-8198.2011.00445.x}, author = {Michael N. Gooseff and Diane M. McKnight and Peter T. Doran and Andrew G Fountain and W. Berry Lyons} } @article {1125, title = {Protist diversity in a permanently ice-covered Antarctic Lake during the polar night transition}, journal = {The ISME Journal}, volume = {5}, year = {2011}, month = {9/2011}, pages = {1559 - 1564}, keywords = {LTER-MCM}, doi = {10.1038/ismej.2011.23}, url = {http://www.nature.com/ismej/journal/v5/n9/abs/ismej201123a.html}, author = {Scott Bielewicz and Elanor R. Bell and Weidong Kong and Iddo Friedberg and John C. Priscu and Rachael M. Morgan-Kiss} } @phdthesis {4085, title = {Removal of benthic algae in swift-flowing streams: The significance of spatial and temporal variation in shear stress and bed disturbance}, volume = {Ph.D.}, year = {2011}, pages = {263}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

In this thesis I investigate the role of spatial and temporal dynamics of flow, bed shear stress, and bed disturbance on the removal of benthic algal and the consequences for our understanding of the dynamics of stream ecosystems and the transport of organic matter in fluvial systems. I use data obtained from two specific case studies where benthic algal mats are key components in the overall system dynamics. The first case study investigates spatial and temporal variations in particular organic matter transport derived from the removal of benthic algae in a stream in the McMurdo Dry Valleys of Antarctica. The second case study uses a combination of field observations and analysis, one and two dimensional hydraulic modeling, and laboratory flume studies to investigate the controls on the removal of the stalk forming diatom\ Didymosphenia geminata. The results show that benthic algae growing in swift-flowing streams are well adapted to this environment. Hence the removal of organic material due to elevated shear stress alone is limited and effective control of nuisance blooms of benthic algae such as\ D. geminata\ requires flood events sufficiently high enough to results in wide spread disturbance of the stream substrate. These flow requirements are similar to the requirements for channel maintenance flows and could therefore be considered for inclusion in the operating rules for dams in order to maintain the diversity of stream ecosystems and functioning water supply infrastructure.

}, keywords = {LTER-MCM}, url = {https://search.proquest.com/docview/916604693?accountid=14503}, author = {Cullis, James D.S.}, editor = {Diane M. McKnight} } @article {1129, title = {Simulating unsteady flow, anabranching, and hyporheic dynamics in a glacial meltwater stream using a coupled surface water routing and groundwater flow model}, journal = {Water Resources Research}, volume = {47}, year = {2011}, month = {2011}, keywords = {LTER-MCM}, doi = {10.1029/2010WR009508}, author = {Koch, J. and Diane M. McKnight and Neupauer, R. M.} } @book {1146, title = {Spectral Methods to Advance Understanding of Dissolved Organic Carbon Dynamics in Forested Catchments}, series = {Ecological StudiesForest Hydrology and Biogeochemistry}, volume = {216}, year = {2011}, pages = {117 - 135}, publisher = {Springer Netherlands}, organization = {Springer Netherlands}, address = {Dordrecht}, keywords = {LTER-MCM}, isbn = {978-94-007-1363-5}, doi = {10.1007/978-94-007-1363-5_6}, url = {http://www.springerlink.com/content/lv9365ml54192m29/}, author = {Rose M. Cory and Elizabeth W. Boyer and Diane M. McKnight}, editor = {Levia, Delphis F. and Carlyle-Moses, Darryl and Tanaka, Tadashi} } @article {1138, title = {When a habitat freezes solid: microorganisms over-winter within the ice column of a coastal Antarctic lake}, journal = {FEMS Microbiology Ecology}, volume = {76}, year = {2011}, month = {06/2011}, pages = {401 - 412}, keywords = {LTER-MCM}, doi = {10.1111/j.1574-6941.2011.01061.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2011.01061.x/full}, author = {Christine M. Foreman and Markus Dieser and Mark Greenwood and Rose M. Cory and Johanna Laybourn-Parry and John T. Lisle and Chris Jaros and Penney L. Miller and Yu-Ping Chin and Diane M. McKnight} } @article {1148, title = {Abiotic nitrous oxide emission from the hypersaline Don Juan Pond in Antarctica}, journal = {Nature Geoscience}, volume = {3}, year = {2010}, month = {5/2010}, pages = {341 - 344}, keywords = {LTER-MCM}, doi = {10.1038/ngeo847}, url = {http://www.nature.com/ngeo/journal/v3/n5/full/ngeo847.html}, author = {Samarkin, Vladimir A. and Madigan, Michael T. and Bowles, Marshall W. and Karen L. Casciotti and John C. Priscu and Christopher P. McKay and Joye, Samantha B.} } @inbook {1168, title = {Antarctic McMurdo Dry Valley stream ecosystems as analog to fluvial systems on Mars}, booktitle = {Life in Antarctic Deserts and other Cold Dry Environments}, year = {2010}, pages = {139 - 159}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, address = {Cambridge}, keywords = {LTER-MCM}, isbn = {9780521889193}, doi = {10.1017/CBO9780511712258.005}, author = {Michael N. Gooseff and Diane M. McKnight and Carr, M. H. and Baeseman, J.}, editor = {Peter T. Doran and W. Berry Lyons and Diane M. McKnight} } @article {1157, title = {Design and deployment of a four-degrees-of-freedom hovering autonomous underwater vehicle for sub-ice exploration and mapping}, journal = {Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment}, volume = {224}, year = {2010}, month = {11/2010}, pages = {341 - 361}, keywords = {LTER-MCM}, doi = {10.1243/14750902JEME214}, author = {Stone, W and Bartholomew P Hogan and Flesher, C and Gulati, S and Kristof Richmond and Murarka, A and Kuhlman, G and Idharan, M and Siegel, V and Price, R M and Peter T. Doran and John C. Priscu} } @inbook {1170, title = {Diatoms as indicators of environmental change in Antarctic and subantarctic freshwaters}, booktitle = {The Diatoms Applications for the Environmental and Earth Sciences}, year = {2010}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, edition = {2}, keywords = {LTER-MCM}, isbn = {9780521509961}, url = {http://www.cambridge.org/us/academic/subjects/life-sciences/plant-science/diatoms-applications-environmental-and-earth-sciences-2nd-edition}, author = {Sarah A. Spaulding and Bart Van de Vijver and Hodgson, D and Diane M. McKnight and Elie Verleyen and Lee F. Stanish} } @article {1161, title = {Effect of instrument-specific response on the analysis of fulvic acid fluorescence spectra}, journal = {Limnology and Oceanography: Methods}, volume = {8}, year = {2010}, month = {07/2010}, pages = {67-78}, keywords = {LTER-MCM}, url = {http://www.aslo.org/lomethods/free/2010/0067.html}, author = {Rose M. Cory and Mathew P. Miller and Diane M. McKnight and Guerard, Jennifer and Penney L. Miller} } @article {4816, title = {Effect of unsteady flow on nitrate loss in an oligotrophic, glacial meltwater stream}, journal = {Journal of Geophysical Research}, volume = {115}, year = {2010}, month = {03/2010}, pages = {G01001}, abstract = {

The McMurdo Dry Valleys of Antarctica are among the coldest, driest ecosystems on Earth. During the austral summer, glacial meltwater supports cyanobacterial mat communities in some streams, but they are not ubiquitous. We conducted a nitrate (NO3-) enrichment tracer injection in Huey Creek to quantify NO3- loss in a Dry Valley stream where algal mats would not obscure hyporheic microbial processes. Unsteady streamflow led to diel variability in the tracer concentration and in surface/subsurface water and solute exchange. Subsequently, concentrations of NO3-, nitrite (NO2-), ammonium (NH4+), and dissolved organic carbon (DOC) varied significantly during the injection, with a net loss of NO3-, NO2-, and DOC, and production of nitrous oxide. These mass changes within a reach were often coincident with high streamflows. Reactivity also coincided with the highest DOC concentrations, suggesting that DOC is the primary limitation to heterotrophic microbial activity in the stream. Together, streamflow and DOC availability create the hot spots and hot moments that dominate NO3- reactivity and removal in this polar desert ecosystem. The combination of spatially and temporally variable hyporheic dynamics and solute availability underscore the limitations of common nutrient uptake metrics and transient storage models when unsteady flow conditions exist.

}, keywords = {LTER-MCM, Antarctica, hot spots/hot moments, hyporheic exchange, nitrogen cycling, unsteady flow}, doi = {10.1029/2009JG001030}, url = {http://doi.wiley.com/10.1029/2009JG001030}, author = {Koch, J. and Diane M. McKnight and Baeseman, J.} } @phdthesis {4190, title = {Hydrologic and biogeochemical implications of flooding in two catchments underlain by continuous permafrost}, volume = {Ph.D.}, year = {2010}, month = {2010}, pages = {206}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Flooding is a critical driver of ecosystem productivity. By rapidly increasing stream stage and velocity, floods mix water and solutes from the stream, hyporheic zone, and floodplains/riparian areas. Such mixing may spur biogeochemical activity. In catchments underlain by permafrost, flooding is more common due to both the potential for rapid ice melting and minimal storage potential in frozen soils. High latitude environments are often underlain by permafrost and are also areas of biogeochemical interest, due to large stores of carbon (C) and nitrogen (N), and the potential for rapid cycling. The increased complexity in groundwater/surface water hydrology during floods requires rigorous hydrologic analysis before biogeochemical trends can be correctly interpreted. This research aims to accurately quantify the hydrology and biogeochemical cycling of C and N in two high-latitude catchments utilizing stream tracer additions, synoptic sampling, and surface water (sw), groundwater (gw), and coupled sw/gw flow models.

Two catchments, in Alaska and Antarctica represent very different ecosystems, both characterized by continuous permafrost and shallow aquifers. In Antarctica, coupled surface water/groundwater flow modeling and tracer additions identify sources of DOC (dissolved organic carbon) and locations of denitrification. Mass balance calculations identify heightened water/sediment interactions at high flows, and increased C and N uptake when solutes return to the stream during low flows. In Alaska, discharge correlates to DOC and nitrate concentrations, indicating leaching and flushing of organic material from the hillslope during high discharge, with a greater potential for microbial processing of this organic material during low flows. Multiple tracer additions demonstrate a seasonal trend, with the greatest C and N uptake early in the summer, potentially related to shallower flowpaths.

Differences between discharge, flooding, and C and N cycling in these two catchments indicate the importance of stream size and morphology. Using tracer dilution and major ion and uranium isotope chemistry, we identify preferential flow near and beneath the stream, indicating erosion of the stream bed via soil piping and thermokarsting. We propose that channel evolution will lead to decreased stream/catchment interactions and subsequently decreased C and N uptake potential in these high-latitude catchments.

}, keywords = {LTER-MCM, carbon, catchments, earth sciences, flooding, nitrogen, permafrost, surface-groundwater interactions}, url = {https://search.proquest.com/docview/839008865}, author = {Koch, J. and Diane M. McKnight} } @book {1173, title = {Life in Antarctic Deserts and Other Cold Environments}, series = {Astrobiological Analogs}, volume = {5}, year = {2010}, pages = {307}, publisher = {Cambridge University Press.}, organization = {Cambridge University Press.}, address = {Cambridge}, keywords = {LTER-MCM, Planetary Science}, isbn = {9780511712258}, doi = {10.1017/CBO9780511712258}, url = {http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511712258}, author = {Peter T. Doran and W. Berry Lyons and Diane M. McKnight}, editor = {Diane M. McKnight and Michael N. Gooseff and Cristina D. Takacs-Vesbach and Jill A. Mikucki and Martyn Tranter and Sun, Henry J} } @phdthesis {1177, title = {Microbial interactions with dissolved organic matter in saline natural waters}, year = {2010}, school = {University of Colorado}, type = {doctoral}, keywords = {LTER-MCM}, doi = {LTER}, author = {Cawley, K} } @article {1167, title = {New insights into the origin and evolution of Lake Vida, McMurdo Dry Valleys, Antarctica {\textemdash} A noble gas study in ice and brines}, journal = {Earth and Planetary Science Letters}, volume = {289}, year = {2010}, month = {01/2010}, pages = {112 - 122}, keywords = {LTER-MCM}, doi = {10.1016/j.epsl.2009.10.034}, url = {http://www.sciencedirect.com/science/article/pii/S0012821X09006335}, author = {Jessica L. Malone and Clara M. Castro and Chris M. Hall and Peter T. Doran and Kenig, Fabien and Christopher P. McKay} } @article {1149, title = {Origin and tentative identification of tri to pentaunsaturated ketones in sediments from Lake Fryxell, East Antarctica}, journal = {Organic Geochemistry}, volume = {41}, year = {2010}, month = {4/2010}, pages = {386 - 397}, keywords = {LTER-MCM}, doi = {10.1016/j.orggeochem.2009.12.004}, author = {Jaraula, Caroline M.B. and Brassell, Simon C. and Rachael M. Morgan-Kiss and Peter T. Doran and Kenig, Fabien} } @article {1158, title = {Palaeoenvironmental implications derived from a piston core from east lobe Bonney, Taylor Valley, Antarctica}, journal = {Antarctic Science}, volume = {22}, year = {2010}, month = {10/2010}, pages = {522 - 530}, keywords = {LTER-MCM}, doi = {10.1017/S0954102010000556}, author = {Wagner, Bernd and Ortlepp, Sabrina and Kenig, Fabien and Peter T. Doran and Melles, Martin} } @article {1174, title = {Physiochemical properties influencing biomass abundance and primary production in Lake Hoare, Antarctica}, journal = {Ecological Modelling}, year = {2010}, keywords = {LTER-MCM}, doi = {LTER}, author = {Herbei, Radu and W. Berry Lyons and Johanna Laybourn-Parry and Christopher B. Gardner and John C. Priscu and Diane M. McKnight} } @inbook {1175, title = {Saline lakes and ponds in the McMurdo Dry Valleys: ecological analogs to martian paleolake environments}, booktitle = {Life in Antarctic Deserts and other Cold Dry Environments}, year = {2010}, pages = {160 - 194}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, address = {Cambridge}, keywords = {LTER-MCM}, isbn = {9780521889193}, doi = {10.1017/CBO9780511712258.006}, url = {http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511712258\&cid=CBO9780511712258A013}, author = {Jill A. Mikucki and W. Berry Lyons and Ian Hawes and Brian D. Lanoil and Peter T. Doran} } @article {1166, title = {Snow in the McMurdo Dry Valleys, Antarctica.}, journal = {International Journal of Climatology}, volume = {30}, year = {2010}, month = {04/2010}, pages = {633-642}, type = {Journal}, abstract = {

Snowfall was measured at 11 sites in the McMurdo Dry Valleys to determine its magnitude, its temporal changes, and spatial patterns. Annual values ranged from 3 to 50 mm water equivalent with the highest values nearest the coast and decreasing inland. A particularly strong spatial gradient exists in Taylor Valley, probably resulting from local uplift conditions at the coastal margin and valley topography that limits migration inland. More snow occurs in winter near the coast, whereas inland no seasonal pattern is discernable. This may be due, again, to local uplift conditions, which are common in winter. We find no influence of the distance to the sea ice edge. Katabatic winds play an important role in transporting snow to the valley bottoms and essentially double the precipitation. That much of the snow accumulation sublimates prior to making a hydrologic contribution underscores the notion that the McMurdo Dry Valleys are indeed an extreme polar desert. Copyright \© 2009 Royal Meteorological Society

}, keywords = {LTER-MCM, Biggie}, doi = {10.1002/joc.1933}, author = {Andrew G Fountain and Thomas H. Nylen and Andrew Monaghan and Hassan J. Basagic and David Bromwich} } @article {1154, title = {Spatial variations in the geochemistry of glacial meltwater streams in the Taylor Valley, Antarctica}, journal = {Antarctic Science}, volume = {22}, year = {2010}, month = {12/2010}, pages = {662 - 672}, keywords = {LTER-MCM}, doi = {10.1017/S0954102010000702}, url = {http://www.montana.edu/lkbonney/DOCS/Publications/WelchEtAl2010Geochemistry.pdf}, author = {Kathleen A. Welch and W. Berry Lyons and Whisner, Carla and Christopher B. Gardner and Michael N. Gooseff and Diane M. McKnight and John C. Priscu} } @conference {1164, title = {Toward autonomous scientific exploration of ice-covered lakes{\textemdash}Field experiments with the ENDURANCE AUV in an Antarctic Dry Valley}, booktitle = {2010 IEEE International Conference on Robotics and Automation (ICRA 2010)2010 IEEE International Conference on Robotics and Automation}, year = {2010}, month = {05/2010}, pages = {308 - 315}, publisher = {IEEE}, organization = {IEEE}, address = {Anchorage, AK}, keywords = {LTER-MCM}, isbn = {978-1-4244-5038-1}, doi = {10.1109/ROBOT.2010.5509224}, author = {Gulati, S and Kristof Richmond and Flesher, C and Bartholomew P Hogan and Murarka, A and Gregory Kuhlmann and Mohan Sridharan and Stone, W and Peter T. Doran} } @article {1197, title = {Accelerate Synthesis in Ecology and Environmental Sciences.}, journal = {Bioscience}, volume = {59}, year = {2009}, pages = {699-701}, keywords = {LTER-MCM}, doi = {LTER}, author = {Carpenter, S and Lundberg, P and Mangel, M and Merchant, N and Murdoch, W and Palmer, M and Debra P. C. Peters and Pickett, S and Smith, K and Diana H. Wall and Maggie K. Zimmerman and Armbrust, E and Arzberger, E and F. S. Chapin and Elser, J and Hackett, E and Ives, A and Kareiva, P and Leibold, M} } @article {1184, title = {A Contemporary Microbially Maintained Subglacial Ferrous "Ocean"}, journal = {Science}, volume = {324}, year = {2009}, month = {04/2009}, pages = {397-400}, type = {Journal}, abstract = {

An active microbial assemblage cycles sulfur in a sulfate-rich, ancient marine brine beneath Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet, with Fe(III) serving as the terminal electron acceptor. Isotopic measurements of sulfate, water, carbonate, and ferrous iron and functional gene analyses of adenosine 5\′-phosphosulfate reductase imply that a microbial consortium facilitates a catalytic sulfur cycle. These metabolic pathways result from a limited organic carbon supply because of the absence of contemporary photosynthesis, yielding a subglacial ferrous brine that is anoxic but not sulfidic. Coupled biogeochemical processes below the glacier enable subglacial microbes to grow in extended isolation, demonstrating how analogous organic-starved systems, such as Neoproterozoic oceans, accumulated Fe(II) despite the presence of an active sulfur cycle.

}, keywords = {LTER-MCM, Biggie}, doi = {10.1126/science.1167350}, url = {http://www.sciencemag.org/content/324/5925/397.short}, author = {Jill A. Mikucki and Pearson, A and Johnston, D and Turchyn, A and Farquhar, J and Schrag, D and Anbar, A and John C. Priscu and Lee, P} } @phdthesis {4191, title = {Controls on stream and hyporheic temperatures, Taylor Valley, Antarctica and large-scale climate influences on interannual flow variation in the Onyx River, Antarctica}, volume = {Ph.D.}, year = {2009}, month = {2009}, pages = {317}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

The McMurdo Dry Valleys comprise the largest ice-free polar desert on the continent of Antarctica. My Ph.D. research investigated summertime glacial meltwater streams flowing through this region. This work is presented in Chapters 2 through 6 of my thesis. Chapters 2-5 present the work I have done related to hyporheic processes while Chapter 6 focuses on the hydroclimatological investigations I have carried out.

More specifically, Chapter 2 addresses the question: what are the dominant processes controlling dry valley stream temperatures? In particular, this investigation quantified the role of hyporheic exchange. The study found that in the Dry Valleys, exchange acted to decrease stream temperatures, accounting for 6\–21\% of cooling.

Chapter 3 discusses a follow up tracer study to investigate whether the comparatively large daily changes in dry valley stream temperatures (6-9\°C) affect hyporheic processes, for instance through viscosity effects. Results showed that the hyporheic zone volume and exchange coefficient were lower during the warmer, afternoon stream/streambed temperature regime than during the cooler, morning one. A temperature-induced feedback mechanism that increases subsurface flow path preferentiality is proposed as a possible explanation for the reduction in hyporheic volume under warmer conditions. The tracer results also suggested a \“Swiss Cheese\” type conceptual model of the hyporheic zone in which flow takes place along paths weaving their way through isolated areas.

Chapter 4 presents work done to elucidate individual hyporheic flow path lengths and residence times. A streambed injection revealed some long (over 100 m) paths that were also fast, having subsurface travel times on par with the surface water. Hyporheic pipeflow is proposed as an explanation.

In Chapter 5 research is presented showing that nitrate and phosphate concentrations at specific locations in the hyporheic zone increase with the decreasing connectivity of that location to the stream.

Finally, Chapter 6 describes the large-scale climate conditions that prevailed during December and January during the highest and lowest flow summers of the Onyx River record, the longest flow record for Antarctica. Climate variables and regions in the Southern Hemisphere that had a statistically significant linear correlation to Onyx River flows were also identified. The highest flow summer on record, 2001-2, was found to have some unusual climate features when compared to the other high flow summers. It stands out as having an anomalous wind pattern that would have increased katabatic winds in the valleys, raising air temperatures and possibly depositing sediment on the glaciers, decreasing their albedo. It is also characterized by anomalously high incoming shortwave radiation. We postulate that those high levels may have been due in part to the unusually low concentrations of radiation absorbing stratospheric ozone prevalent over the valleys that particular summer.

}, keywords = {LTER-MCM, Antarctica, earth sciences, hydroclimatology, hyporheic flow paths, hyporheic zone, stream temperature}, url = {https://search.proquest.com/docview/304866366}, author = {Cozzetto, K and Diane M. McKnight} } @article {1180, title = {Environmental DNA sequencing primers for eutardigrades and bdelloid rotifers}, journal = {BMC Ecology}, volume = {9}, year = {2009}, month = {11/2009}, pages = {25}, keywords = {LTER-MCM}, doi = {10.1186/1472-6785-9-25}, author = {Robeson, Michael S and Costello, Elizabeth K and Freeman, Kristen R and Whiting, Jeremy and Byron Adams and Martin, Andrew P and Schmidt, Steve K} } @article {1181, title = {Lakes and reservoirs as regulators of carbon cycling and climate}, journal = {Limnology and Oceanography}, volume = {54 part 2}, year = {2009}, month = {11/2009}, pages = {2298{\textendash}2314}, keywords = {LTER-MCM}, doi = {10.4319/lo.2009.54.6_part_2.2298}, url = {http://aslo.org/lo/toc/vol_54/issue_6_part_2/2298.pdf}, author = {Lars J. Tranvik and John A. Downing and James B. Cotner and Steven A. Loiselle and Robert G. Striegl and Thomas J. Ballatore and Peter Dillon and Kerri Finlay and Kenneth Fortino and Lesley B. Knoll and Pirkko L. Kortelainen and Tiit Kutser and Soren Larsen and Isabelle Laurion and Dina M. Leech and S. Leigh McCallister and Diane M. McKnight and John M. Melack and Erin Overholt and Jason A. Porter and Yves Prairie and William H. Renwick and Fabio Roland and Bradford S. Sherman and David W. Schindler and Sebastian Sobek and Alain Tremblay and Michael J. Vanni and Antonie M. Verschoor and Eddie von Wachenfeldt and Gesa A. Weyhenmeyer} } @article {1194, title = {State of the Antarctic and the Southern Ocean climate system,}, journal = {Review of Geophysics}, volume = {47}, year = {2009}, keywords = {LTER-MCM}, doi = {LTER}, author = {Paul A. Mayewski and David Bromwich and Campbell, H and Hamilton, G and W. Berry Lyons and Maasch, K and Aoki, S and Xiao, C and van Ommen, T and Meredith, M and Summerhayes, C and Turner, J and Worby, A and John E. Barrett and Casassa, G and Bertler, N and T Bracegirdle} } @inbook {1207, title = {Bacteria in Subglacial Environments}, booktitle = {Psychrophiles: from biodiversity to biotechnology}, year = {2008}, pages = {51-71}, publisher = {Springer Verlag}, organization = {Springer Verlag}, address = {New York}, keywords = {LTER-MCM}, author = {Brent C. Christner and Skidmore, M and John C. Priscu and Martyn Tranter and Christine M. Foreman} } @article {1212, title = {Entry approach into pristine ice-sealed lakes - Lake Vida, East Antarctica, a model ecosystem}, journal = {Limnology and Oceanography-Methods}, volume = {6}, year = {2008}, pages = {542-547}, keywords = {LTER-MCM}, doi = {LTER}, author = {Peter T. Doran and Christian H. Fritsen and A. E. Murray and Kenig, Fabien and Christopher P. McKay and Kyne, J} } @article {1202, title = {Global decomposition experiment shows soil animal impacts on decomposition are climate dependent}, journal = {Global Change Biology}, volume = {14}, year = {2008}, month = {11/2008}, pages = {2661-2677}, keywords = {LTER-MCM}, doi = {10.1111/j.1365-2486.2008.01672.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2008.01672.x/full}, author = {Diana H. Wall and Mark A. Bradford and Mark G. StJohn and John A. Trofymow and Valerie Behan-Pelletier and David E. Bignell and J. Mark Dangerfield and William J. Parton and Josef Rusek and Winfried Voigt and Volkmar Wolters and Holley Zadeh Gardel and Fred O. Ayuke and Richard Bashford and Olga I. Beljakova and Patrick J. Bohlen and Alain Brauman and Stephen Flemming and Joh R. Henschel and Dan L. Johnson and T. Hefin Jones and Marcela Kovarova and J. Marty Kranabetter and Les Kutny and Kuo-Chuan Lin and Mohamed Maryati and Dominique Masse and Andrei Pokarzhevskii and Homathevi Rahman and Millor G. Sabara and Joerg-Alfred Salamon and Michael J. Swift and Amanda Varela and Heraldo L. Vasconcelos and Don White and Xiaming Zou} } @inbook {1214, title = {High-latitude rivers and streams.}, booktitle = {Polar Lakes and Rivers: Limnology of Arctic and Antarctic Aquatic Ecosystems}, year = {2008}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {Oxford}, keywords = {LTER-MCM}, doi = {LTER}, author = {Diane M. McKnight and Michael N. Gooseff and Warwick F. Vincent and Peterson, B}, editor = {Warwick F. Vincent and Johanna Laybourn-Parry} } @article {1204, title = {Hydrologic response to extreme warm and cold summers in the McMurdo Dry Valleys, East Antarctica}, journal = {Antarctic Science}, volume = {20}, year = {2008}, month = {05/16/2008}, pages = {499-509}, type = {Journal}, keywords = {LTER-MCM, Climate Response, streams}, doi = {10.1017/S0954102008001272}, author = {Peter T. Doran and Christopher P. McKay and Andrew G Fountain and Thomas H. Nylen and Diane M. McKnight and Chris Jaros and John E. Barrett} } @article {1216, title = {Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica}, journal = {Botany-Botanique}, volume = {12}, year = {2008}, pages = {1378-1392}, keywords = {LTER-MCM}, doi = {LTER}, author = {Rhea M.M. Esposito and Sarah A. Spaulding and Diane M. McKnight and De Vijver, B and Kopalova, K and Lubinski, D and Brenda L. Hall and Whittaker, T} } @article {1232, title = {Microbial community composition in soils of Northern Victoria Land, Antarctica}, journal = {Environmental Microbiology}, volume = {10}, year = {2008}, pages = {1713-1724}, keywords = {LTER-MCM}, doi = {LTER}, author = {Niederberger, T and McDonald, i and Hacker, A and Soo, R and John E. Barrett and Diana H. Wall and Craig S Cary} } @article {1238, title = {Bacterial diversity associated with Blood Falls, A subglacial outflow from the Taylor Glacier, Antarctica}, journal = {Applied and Environmental Microbiology}, volume = {73}, year = {2007}, pages = {4029-4039}, keywords = {LTER-MCM}, doi = {LTER}, author = {Jill A. Mikucki and John C. Priscu} } @article {1236, title = {Biogeochemical stoichiometry of Antarctic Dry Valley ecosystems}, journal = {Journal of Geophysical Research}, volume = {112}, year = {2007}, month = {02/2007}, pages = {G01010+12}, abstract = {

Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10\–106\ years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates.

}, keywords = {LTER-MCM, Biggie}, doi = {10.1029/2005JG000141}, author = {John E. Barrett and Ross A. Virginia and W. Berry Lyons and Diane M. McKnight and John C. Priscu and Andrew G Fountain and Diana H. Wall and Daryl L. Moorhead and Peter T. Doran} } @article {1244, title = {Mesoscale dynamics of ephemeral wetlands in the Antarctic Dry Valleys: Implications to production and distribution of organic matter}, journal = {Ecosystems}, year = {2007}, pages = {87-95}, keywords = {LTER-MCM}, doi = {LTER}, author = {Daryl L. Moorhead} } @article {1245, title = {Metabolic activity and diversity of cryoconites in the Taylor Valley, Antarctica}, journal = {Journal of Geophysical Research}, volume = {112}, year = {2007}, keywords = {LTER-MCM}, doi = {LTER}, author = {Christine M. Foreman and Sattler, B and Jill A. Mikucki and Porazinska, D and John C. Priscu} } @mastersthesis {1246, title = {Microbial Processes in the Moats of Lakes in the Taylor Valley, Antarctica}, volume = {M.S.}, year = {2007}, school = {Montana State University}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Moore, J} } @article {1235, title = {Reactivation of a cryptobiotic stream ecosystem in the McMurdo Dry Valleys, Antarctica: A long-term geomorphological experiment}, journal = {Geomorphology}, volume = {89}, year = {2007}, month = {09/2007}, pages = {186-204}, keywords = {LTER-MCM}, doi = {10.1016/j.geomorph.2006.07.025}, author = {Diane M. McKnight and Cathy M. Tate and Edmund D. Andrews and Dev K. Niyogi and Cozzetto, K and Kathleen A. Welch and W. Berry Lyons and D. G. Capone} } @mastersthesis {1250, title = {Stable Carbon Isotope Analyses of Sediments from Lake Fryxell, Antarctica}, volume = {M.S.}, year = {2007}, school = {University of Illinois, Chicago}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Moore-Topinka, N} } @proceedings {1251, title = {Trends in discharge and flow season timing of the Onyx River, Wright Valley, Antarctica since 1969}, journal = {Antarctica; A keystone in a changing world--online proceedings for the tenth international symposium}, year = {2007}, publisher = {U.S. Geological Survey Open-File Report 2007-1047}, keywords = {LTER-MCM}, doi = {LTER}, author = {Michael N. Gooseff and Diane M. McKnight and Peter T. Doran and W. Berry Lyons}, editor = {Alan Cooper and Carol Raymond and ISAES Editorial Team} } @article {1257, title = {Adaptation and acclimation of photosynthetic microorganisms to permanently cold environments}, journal = {Microbial and Molecular Biology Review}, volume = {70}, year = {2006}, month = {03/2006}, pages = {222-252}, abstract = {

Persistently cold environments constitute one of our world\&$\#$39;s largest ecosystems, and microorganisms dominate the biomass and metabolic activity in these extreme environments. The stress of low temperatures on life is exacerbated in organisms that rely on photoautrophic production of organic carbon and energy sources. Phototrophic organisms must coordinate temperature-independent reactions of light absorption and photochemistry with temperature-dependent processes of electron transport and utilization of energy sources through growth and metabolism. Despite this conundrum, phototrophic microorganisms thrive in all cold ecosystems described and (together with chemoautrophs) provide the base of autotrophic production in low-temperature food webs. Psychrophilic (organisms with a requirement for low growth temperatures) and psychrotolerant (organisms tolerant of low growth temperatures) photoautotrophs rely on low-temperature acclimative and adaptive strategies that have been described for other low-temperature-adapted heterotrophic organisms, such as cold-active proteins and maintenance of membrane fluidity. In addition, photoautrophic organisms possess other strategies to balance the absorption of light and the transduction of light energy to stored chemical energy products (NADPH and ATP) with downstream consumption of photosynthetically derived energy products at low temperatures. Lastly, differential adaptive and acclimative mechanisms exist in phototrophic microorganisms residing in low-temperature environments that are exposed to constant low-light environments versus high-light- and high-UV-exposed phototrophic assemblages.

}, keywords = {LTER-MCM, Biggie}, doi = {10.1128/​MMBR.70.1.222-252.2006}, author = {Rachael M. Morgan-Kiss and John C. Priscu and Pocock, T and Gudynaite-Savitch, L and Norman P.A. Huner} } @article {1259, title = {The aeolian flux of calcium, chloride and nitrate to the McMurdo Dry Valleys landscape: Evidence from snow pit analysis}, journal = {Antarctic Science}, volume = {18}, year = {2006}, pages = {497-505}, keywords = {LTER-MCM}, doi = {LTER}, author = {Witherow, R and Bertler, N and Kathleen A. Welch and W. Berry Lyons and Paul A. Mayewski and Sneed, S and Thomas H. Nylen and Handley, M and Andrew G Fountain} } @article {1256, title = {Antarctic Climate Cooling and Response of Diatoms in Glacial Meltwater Streams}, journal = {Geophysical Research Letters}, volume = {33}, year = {2006}, month = {04/2006}, pages = {L07406}, type = {Journal}, abstract = {

To understand biotic responses to an Antarctic cooling trend, we analyzed diatom samples from glacial meltwater streams in the McMurdo Dry Valleys, the largest ice-free area in Antarctica. Diatoms are abundant in these streams, and 24 of 40 species have only been found in the Antarctic. The percentage of these Antarctic diatom species increased with decreasing annual stream flow and increasing harshness of the stream habitat. The species diversity of assemblages reached a maximum when the Antarctic species accounted for 40\–60\% of relative diatom abundance. Decreased solar radiation and air-temperatures reduce annual stream flow, raising the dominance of these Antarctic species to levels above 60\%. Thus, cooling favors the Antarctic species, and lowers diatom species diversity in this region.

}, keywords = {LTER-MCM, Biggie}, doi = {10.1029/2006GL025903}, author = {Rhea M.M. Esposito and Horn, S and Diane M. McKnight and Cox, M and Grant, M and Sarah A. Spaulding and Peter T. Doran and Cozzetto, K} } @article {1266, title = {Environmental factors associated with deep chlorophyll maxima in dry valley lakes, South Victoria Land, Antarctica}, journal = {Arctic, Antarctic, and Alpine Research}, volume = {38}, year = {2006}, pages = {179-189}, keywords = {LTER-MCM}, doi = {LTER}, author = {Burnett, L and Daryl L. Moorhead and Ian Hawes and Clive Howard-Williams} } @article {1267, title = {Experimental investigations into processes controlling stream and hyporheic temperatures, Fryxell Basin, Antarctica}, journal = {Advances in Water Resources}, volume = {29}, year = {2006}, pages = {130-153}, keywords = {LTER-MCM}, doi = {LTER}, author = {Cozzetto, K and Diane M. McKnight and Thomas H. Nylen and Andrew G Fountain} } @article {1269, title = {Glacial and postglacial sedimentation in the Fryxell basin, Taylor Valley, Southern Victoria Land, Antarctica}, journal = {Palaeography, Palaeoclimatology, Palaeoecology}, volume = {341}, year = {2006}, pages = {320}, keywords = {LTER-MCM}, doi = {LTER}, author = {Wagner, B and Melles, M and Peter T. Doran and Kenig, Fabien and Forman, S and Pierau, R and Allan, P} } @article {1270, title = {Glacier mass balances (1993-2001) Taylor Valley, McMurdo Dry Valleys, Antarctica}, journal = {Journal of Glaciology}, volume = {52}, year = {2006}, pages = {451}, keywords = {LTER-MCM}, doi = {LTER}, author = {Andrew G Fountain and Thomas H. Nylen and MacClune, K and Gayle L. Dana} } @book {1271, title = {The Lost Seal}, year = {2006}, pages = {40}, publisher = {Moonlight Publishing LLC}, organization = {Moonlight Publishing LLC}, address = {Lafayette}, keywords = {LTER-MCM}, isbn = {978-0972342278}, doi = {LTER}, author = {Diane M. McKnight} } @thesis {1282, title = {A Qualitative Approach to Understanding the Rate of Weathering, Taylor Valley, Antarctica}, year = {2006}, school = {The Ohio State University}, type = {bachelors}, keywords = {LTER-MCM}, doi = {LTER}, author = {Miller, E} } @article {1284, title = {Simulating energy flow through a pelagic food web in Lake Fryxell, Antarctica}, journal = {Ecological Modelling}, volume = {192}, year = {2006}, pages = {457-472}, keywords = {LTER-MCM}, doi = {LTER}, author = {McKenna, K and Daryl L. Moorhead and Emily C. Roberts and Johanna Laybourn-Parry} } @article {1275, title = {Spatial and temporal active layer dynamics along three glacial meltwater streams in the McMurdo Dry Valleys, Antarctica}, journal = {Arctic Antarctic and Alpine Research}, volume = {38}, year = {2006}, pages = {42-53}, keywords = {LTER-MCM}, doi = {LTER}, author = {Peter A. Conovitz and Lee H. MacDonald and Diane M. McKnight} } @article {1258, title = {A stable isotopic investigation of a polar desert hydrologic system, McMurdo Dry Valleys, Antarctica}, journal = {Arctic, Antarctic, and Alpine Research}, volume = {38}, year = {2006}, month = {02/2006}, pages = {60-71}, keywords = {LTER-MCM}, doi = {10.1657/1523-0430(2006)038[0060:ASIIOA]2.0.CO;2}, author = {Michael N. Gooseff and W. Berry Lyons and Diane M. McKnight and Bruce H. Vaughn and Andrew G Fountain and Carolyn Dowling} } @article {1278, title = {Terrestrial ecosystem processes of Victoria Land, Antarctica}, journal = {Soil Biology and Biochemistry}, volume = {38}, year = {2006}, pages = {3019-3034}, keywords = {LTER-MCM}, doi = {LTER}, author = {John E. Barrett and Johnson N. Nkem and Sletten, R and Steltzer, H and Diana H. Wall and Wallenstein, M and Ross A. Virginia and D. W. Hopkins and Aislabie, J and Bargagli, R and Bockheim, J and Campbell, I and W. Berry Lyons and Daryl L. Moorhead} } @article {1291, title = {Biogeological Raman spectroscopic studies of Antarctic lacustrine sediments}, journal = {Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy}, volume = {61}, year = {2005}, keywords = {LTER-MCM}, author = {Moody, C and Villar, S and Edwards, H and Hodgson, D and Peter T. Doran and J.L. Bishop} } @article {1293, title = {Comment on {\textquoteleft}{\textquoteleft}El Ni{\~n}o suppresses Antarctic warming{\textquoteright}{\textquoteright} by N. Bertler et al.}, journal = {Geophysical Research Letters}, volume = {32}, year = {2005}, pages = {L07706}, keywords = {LTER-MCM, Tropical meteorology}, doi = {10.1029/2004GL021716}, author = {Peter T. Doran and Gary D. Clow and Christian H. Fritsen and Christopher P. McKay and Andrew N. Parsons and John C. Priscu and W. Berry Lyons and Walsh, J and Andrew G Fountain and Diane M. McKnight and Daryl L. Moorhead and Ross A. Virginia and Diana H. Wall} } @article {1310, title = {Contributions of Benthic Microbial Mats to Net Primary Production in Lake Hoare, Antarctica}, journal = {Antarctic Science}, volume = {17}, year = {2005}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and Schmeling, S and Ian Hawes} } @article {1298, title = {Glacial ice cores: a model system for developing extraterrestrial decontamination protocols}, journal = {Icarus}, volume = {174}, year = {2005}, pages = {572-584}, keywords = {LTER-MCM}, doi = {LTER}, url = {/reports/lakes/ChristnerEtAl2005Decontamination.pdf}, author = {Brent C. Christner and Jill A. Mikucki and Christine M. Foreman and Denson, J and John C. Priscu} } @article {1300, title = {Halogen geochemistry of the McMurdo Dry Valleys Lakes, Antarctica: clues to the origin of solutes and lake evolution}, journal = {Geochimica et Cosmochimica Acta}, volume = {69}, year = {2005}, pages = {305-323}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Kathleen A. Welch and Snyder, G and Olesik, J and Graham, E and G. M. Marion and Robert J. Poreda} } @phdthesis {1302, title = {Microbial Ecology of an Antarctic Subglacial Environment}, volume = {Ph.D.}, year = {2005}, school = {Montana State University}, type = {doctoral}, keywords = {LTER-MCM}, doi = {LTER}, author = {Jill A. Mikucki} } @inbook {1304, title = {Perennial Antarctic lake ice: A refuge for cyanobacteria in an extreme environment}, booktitle = {Life in Ancient Ice}, year = {2005}, pages = {22-49}, publisher = {Princeton University Press}, organization = {Princeton University Press}, keywords = {LTER-MCM}, url = {http://www.montana.edu/lkbonney/DOCS/Publications/PriscuEtAl2005CyanobacteriaRefuge.pdf}, author = {John C. Priscu and Edward E. Adams and Hans W. Paerl and Christian H. Fritsen and John E. Dore and John T. Lisle and Craig F. Wolf and Jill A. Mikucki}, editor = {S. O. Rogers and J. Castello} } @inbook {1306, title = {Polar lakes, streams, and springs as analogs for the hydrological cycle on Mars.}, booktitle = {Advances in Astrobiology and Biogeophysics}, year = {2005}, pages = {219-233}, publisher = {Springer Verlag}, organization = {Springer Verlag}, address = {Berlin, Heidelberg}, keywords = {LTER-MCM}, doi = {LTER}, url = {/reports/lakes/McKayEtAl2005StreamsSprings.pdf}, author = {Christopher P. McKay and Dale T. Andersen and Pollard, W and Heldmann, J and Peter T. Doran and Christian H. Fritsen and John C. Priscu} } @inbook {1307, title = {Polar Systems}, booktitle = {Millennium Ecosystem Assessment. Current State and Trends: Findings of the Condition and Trends Working Group}, year = {2005}, pages = {717-743}, publisher = {Island Press}, organization = {Island Press}, keywords = {LTER-MCM}, doi = {LTER}, author = {F. S. Chapin and McGuire, A and Nuttall, M and Ross A. Virginia and Young, O and Zimov, S and Christensen, T and Godduhn, A and Murphy, E and Diana H. Wall and Zockler, C and Berman, M and Callaghan, T and Peter Convey and A. S. Crepin and Danell, K and Hugh W. Ducklow and Forbes, B and Kofinas, G}, editor = {R. Hassan and R. Scholes and N. Ash} } @article {1288, title = {Sensitivity analysis of conservative and reactive stream transient storage models applied to field data from multiple-reach experiments}, journal = {Advances in Water Resources}, volume = {28}, year = {2005}, month = {05/2005}, pages = {479-492}, keywords = {LTER-MCM}, doi = {10.1016/j.advwatres.2004.11.012}, author = {Michael N. Gooseff and Kenneth E. Bencala and Durelle T. Scott and Robert L. Runkel and Diane M. McKnight} } @article {1325, title = {Changes in fulvic acid redox state through the oxycline of a permanently ice-covered Antarctic lake}, journal = {Aquatic Sciences}, volume = {66}, year = {2004}, pages = {1-20}, keywords = {LTER-MCM}, author = {Fulton, J and Diane M. McKnight and Christine M. Foreman and Rose M. Cory and Stedmon, C and Blunt, E} } @article {1319, title = {Denitrification and hydrologic transient storage in a glacial meltwater stream, McMurdo Dry Valleys, Antarctica}, journal = {Limnology and Oceanography}, volume = {49}, year = {2004}, month = {09/2004}, pages = {1884-1895}, keywords = {LTER-MCM}, doi = {10.4319/lo.2004.49.5.1884}, author = {Michael N. Gooseff and Diane M. McKnight and Robert L. Runkel and John H. Duff} } @article {1349, title = {Detritus, trophic dynamics and biodiversity.}, journal = {Ecology Letters}, volume = {7}, year = {2004}, pages = {584-600}, keywords = {LTER-MCM}, doi = {LTER}, author = {Moore, J and Morin, P and Nadelhoffer, K and Rosemound, A and Post , D and Sabo, J and Scow, K and Michael J. Vanni and Diana H. Wall and Berlow, E and David C. Coleman and Peter C. De Ruiter and Dong, Q and Hasting, A and Johnson, N and McCann, K and Melville, K} } @article {1321, title = {Evolution of cryoconite holes and their contribution to meltwater runoff from glaciers in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Glaciology}, volume = {50}, year = {2004}, month = {01/2004}, pages = {35-45}, keywords = {LTER-MCM}, doi = {10.3189/172756504781830312}, author = {Andrew G Fountain and Martyn Tranter and Thomas H. Nylen and Karen J. Lewis and Derek R. Mueller} } @inbook {1332, title = {Geochronology of high latitude lake sediments}, booktitle = {Long-Term Environmental Change in Arctic and Antarctic Lakes}, year = {2004}, publisher = {Kluwer Academic Publishers}, organization = {Kluwer Academic Publishers}, keywords = {LTER-MCM}, author = {Wolf, A and Miller, G and Olsen, C and Forman, S and Peter T. Doran and Holmgren, S}, editor = {Pienitz, R and Douglas, Marianne S. V. and J.P. Smol} } @article {1333, title = {Geomicrobiology of Blood Fall: An iron-rich saline discharge at the terminus of the Taylor Glacier, Antarctica}, journal = {Aquatic Geochemistry}, volume = {10}, year = {2004}, pages = {199-200}, keywords = {LTER-MCM}, author = {Jill A. Mikucki and Christine M. Foreman and Sattler, B and W. Berry Lyons and John C. Priscu} } @article {1353, title = {Gradient analysis of cryoconite ecosystems from two Polar glaciers}, journal = {Polar Biology}, volume = {27}, year = {2004}, pages = {66-74}, keywords = {LTER-MCM}, author = {Derek R. Mueller and Pollard, W} } @article {1354, title = {The impact of anhydrobiosis on the persistence of Scottnema lindsyae (Nematoda): a modeling analysis of population stability thresholds}, journal = {Polar Biology}, volume = {27}, year = {2004}, pages = {507-512}, keywords = {LTER-MCM}, author = {Weicht, T and Daryl L. Moorhead} } @article {1335, title = {Inorganic nitrogen and phosphorus dynamics of Antarctic glacial meltwater streams as controlled by hyporheic exchange and benthic autotrophic communities}, journal = {Journal of the North American Benthological Society}, volume = {23}, year = {2004}, pages = {171-188}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Robert L. Runkel and John H. Duff and Cathy M. Tate and Daryl L. Moorhead} } @article {1341, title = {Reach-scale cation exchange controls on major ion chemistry of an Antarctic glacial meltwater stream}, journal = {Special issue of Aquatic Geochemistry on the McMurdo Dry Valleys}, volume = {10}, year = {2004}, pages = {221-238}, keywords = {LTER-MCM}, author = {Michael N. Gooseff and Diane M. McKnight and Robert L. Runkel} } @article {1345, title = {Thermodynamic constraints on microbially mediated processes in lakes of the McMurdo Dry Valleys, Antarctica}, journal = {Geomicrobiology Journal}, volume = {21}, year = {2004}, pages = {1-17}, keywords = {LTER-MCM}, doi = {LTER}, author = {Lee, P and Jill A. Mikucki and Christine M. Foreman and John C. Priscu and G R DiTullio and Riseman, S and DeMora, S and Craig F. Wolf and Kester, L} } @article {1356, title = {Trophic interactions in a changing world: modelling aboveground-belowground interactions}, journal = {Basic and Applied Ecology}, volume = {5}, year = {2004}, pages = {515-528}, keywords = {LTER-MCM}, doi = {LTER}, author = {Schroter, D and Brussaard, L and De Deyn, G and Proveda, K and Brown, V and Berg, M and Wardle, D and Moore, J and Diana H. Wall} } @article {1358, title = {Biochemistry of Si in the McMurdo Dry Valley lakes, Antarctica}, journal = {The International Journal of Astrobiology}, volume = {1}, year = {2003}, pages = {737-749}, keywords = {LTER-MCM}, author = {Pugh, H and Kathleen A. Welch and W. Berry Lyons and John C. Priscu and Diane M. McKnight} } @inbook {1360, title = {Chemistry and lake dynamics of the Taylor Valley lakes, Antarctica: The importance of long-term monitoring.}, booktitle = {Antarctic Ecosystems: Models for Wider Ecological Understanding}, year = {2003}, publisher = {Caxton Press}, organization = {Caxton Press}, keywords = {LTER-MCM}, author = {Kathleen A. Welch and Klaus Neumann and W. Berry Lyons and Diane M. McKnight}, editor = {Clive Howard-Williams and W. Davidson and P. Broady} } @article {1361, title = {Determining long time-scale hyporheic zone flow paths in Antarctic streams}, journal = {Hydrological Processes}, volume = {17}, year = {2003}, pages = {1691-1710}, keywords = {LTER-MCM}, author = {Michael N. Gooseff and Diane M. McKnight and Robert L. Runkel and Bruce H. Vaughn} } @article {1357, title = {Formation and character of an ancient 19 m ice cover and underlying trapped brine in an}, journal = {Proceedings of National Academy of Sciences}, volume = {100}, year = {2003}, month = {01/2003}, pages = {26-31}, type = {Journal}, keywords = {LTER-MCM}, doi = {10.1073/pnas.222680999}, url = {http://www.pnas.org/content/100/1/26.short}, author = {Peter T. Doran and Christian H. Fritsen and Christopher P. McKay and John C. Priscu and Edward E. Adams} } @article {1364, title = {Glaciers of the McMurdo Dry Valleys: terrestrial analog for Martian polar sublimation}, journal = {Journal of Geophysical Research}, volume = {108}, year = {2003}, pages = {5031}, keywords = {LTER-MCM}, author = {Karen J. Lewis and Andrew G Fountain and Kargel, J and MacAyeal, D} } @article {1370, title = {Long-term perspectives on biodiversity-ecosystem function.}, journal = {Bioscience}, year = {2003}, pages = {89-98}, keywords = {LTER-MCM}, author = {Symstad, A and Chapin III, F and Diana H. Wall and Gross, K and Huenneke, L and Mittelbach, G and Debra P. C. Peters and Tilman, D} } @article {1371, title = {Organic matter and soil biota of upland wetlands in Taylor Valley, Antarctica}, journal = {Polar Biology}, volume = {26}, year = {2003}, pages = {1009-1019}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and John E. Barrett and Ross A. Virginia and Diana H. Wall and Porazinska, D} } @article {1369, title = {Surface glaciochemistry of Taylor Valley, southern Victoria Land, Antarctica and its relationship to stream chemistry.}, journal = {Hydrological Processes}, volume = {17}, year = {2003}, pages = {115-130}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Kathleen A. Welch and Andrew G Fountain and Gayle L. Dana and Bruce H. Vaughn and Diane M. McKnight} } @article {1377, title = {Antarctic climate cooling and terrestrial ecosystem response}, journal = {Nature}, volume = {415}, year = {2002}, month = {01/2002}, pages = {517-520}, type = {Journal}, keywords = {LTER-MCM, Climate Response}, doi = {10.1038/nature710}, author = {Peter T. Doran and John C. Priscu and W. Berry Lyons and John E. Walsh and Andrew G Fountain and Diane M. McKnight and Daryl L. Moorhead and Ross A. Virginia and Diana H. Wall and Gary D. Clow and Christian H. Fritsen and Christopher P. McKay and Andrew N. Parsons} } @article {1385, title = {The balance between photosynthesis and grazing in Antarctic mixotrophic cryptophytes during summer}, journal = {Freshwater Biology}, volume = {47}, year = {2002}, pages = {2060-2070}, keywords = {LTER-MCM}, author = {Marshall, W and Johanna Laybourn-Parry} } @mastersthesis {1388, title = {Climatic controls on interannual variation in streamflow in Fryxell Basin, Taylor Valley}, volume = {M.S.}, year = {2002}, school = {University of Colorado}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Chris Jaros} } @article {1378, title = {Direct observation of aluminosilicate weathering in the hyporheic zone of an Antarctic Dry Valley stream}, journal = {Geochimica et Cosmochimica Acta}, volume = {66}, year = {2002}, pages = {1335-1347}, keywords = {LTER-MCM}, author = {Maurice, P and Diane M. McKnight and Leff, L and Fulghun, J and Michael N. Gooseff} } @article {1379, title = {Distribution and life cycle of Scottnema lindsayae (Nematoda) in Antarctic soils: A modeling analysis of tempaerature responses}, journal = {Polar Biology}, volume = {25}, year = {2002}, pages = {118-125}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and Diana H. Wall and Ross A. Virginia and Andrew N. Parsons} } @mastersthesis {1391, title = {Interannual variation in phytoplankton dynamics in Lake Fryxell}, volume = {M.S.}, year = {2002}, school = {University of Colorado}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Van Matre, E} } @article {1382, title = {Recent Temperature Trends in the Antarctic}, journal = {Nature}, volume = {418}, year = {2002}, pages = {291-292}, keywords = {LTER-MCM}, author = {John E. Walsh and Gary D. Clow and Christian H. Fritsen and Christopher P. McKay and Andrew N. Parsons and Peter T. Doran and John C. Priscu and W. Berry Lyons and Andrew G Fountain and Diane M. McKnight and Daryl L. Moorhead and Ross A. Virginia and Diana H. Wall} } @article {1374, title = {Valley floor climate observations from the McMurdo Dry Valleys, Antarctica, 1986-2000}, journal = {Journal of Geophysical Research}, volume = {107}, year = {2002}, month = {12/2002}, pages = {4772-4784}, type = {Journal}, abstract = {

Climate observations from the McMurdo dry valleys, East Antarctica are presented from a network of seven valley floor automatic meteorological stations during the period 1986 to 2000. Mean annual temperatures ranged from \−14.8\°C to \−30.0\°C, depending on the site and period of measurement. Mean annual relative humidity is generally highest near the coast. Mean annual wind speed increases with proximity to the polar plateau. Site-to-site variation in mean annual solar flux and PAR is due to exposure of each station and changes over time are likely related to changes in cloudiness. During the nonsummer months, strong katabatic winds are frequent at some sites and infrequent at others, creating large variation in mean annual temperature owing to the warming effect of the winds. Katabatic wind exposure appears to be controlled to a large degree by the presence of colder air in the region that collects at low points and keeps the warm less dense katabatic flow from the ground. The strong influence of katabatic winds makes prediction of relative mean annual temperature based on geographical position (elevation and distance from the coast) alone, not possible. During the summer months, onshore winds dominate and warm as they progress through the valleys creating a strong linear relationship (r2\ = 0.992) of increasing potential temperature with distance from the coast (0.09\°C km\−1). In contrast to mean annual temperature, summer temperature lends itself quite well to model predictions, and is used to construct a statistical model for predicting summer dry valley temperatures at unmonitored sites.

}, keywords = {LTER-MCM, Biggie}, doi = {10.1029/2001JD002045}, author = {Peter T. Doran and Christopher P. McKay and Gary D. Clow and Gayle L. Dana and Andrew G Fountain and Thomas H. Nylen and W. Berry Lyons} } @article {1375, title = {Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys}, journal = {Water Resources Research}, volume = {38}, year = {2002}, month = {12/2002}, pages = {1279-1296}, type = {Journal}, keywords = {LTER-MCM, Biggie}, doi = {10.1029/2001WR000834}, url = {http://www.agu.org/pubs/crossref/2002/2001WR000834.shtml}, author = {Michael N. Gooseff and Diane M. McKnight and W. Berry Lyons and Blum, A} } @article {1398, title = {Bacterial dissolved organic carbon demand in antarctic dry valley lakes}, journal = {Limnology and Oceanography}, volume = {46}, year = {2001}, month = {07/2001}, pages = {1189-1194}, type = {Journal}, keywords = {LTER-MCM, Biggie}, doi = {10.4319/lo.2001.46.5.1189}, url = {http://www.jstor.org/stable/2671031}, author = {Cristina D. Takacs-Vesbach and John C. Priscu and Diane M. McKnight} } @article {1412, title = {Benthic primary production in two perennially ice-covered Antarctic lakes: comparisons of annual accumulation predicted from photosynthesis models with estimates from internal growth markers}, journal = {Antarctic Science}, volume = {13}, year = {2001}, pages = {18-27}, keywords = {LTER-MCM}, author = {Ian Hawes and Daryl L. Moorhead and Sutherland, J and Schmeling, J and Schwartz, A} } @article {1416, title = {Glacial cryoconite ecosystems: a bipolar comparison of algal communities and habitats}, journal = {Nova Hedwigia}, volume = {123}, year = {2001}, pages = {173-197}, keywords = {LTER-MCM}, author = {Derek R. Mueller and Warwick F. Vincent and Pollard, W and Christian H. Fritsen} } @mastersthesis {1417, title = {The influence of mixotroph growth on DOM chemistry in Pony Lake, a eutrophic coastal pond in Antarctica}, volume = {M.S.}, year = {2001}, school = {University of Colorado}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Brown, A} } @article {1402, title = {The influence of soil biodiversity on hydrological pathways and the transfer of materials between terrestrial and aquatic ecosystems}, journal = {Ecosystems}, volume = {4}, year = {2001}, keywords = {LTER-MCM}, author = {Richard D. Bardgett and Anderson, J. M. and Valerie Behan-Pelletier and Brussaard, L and David C. Coleman and Ettma, C and Moldenke, A and Schimel, J and Diana H. Wall} } @article {1404, title = {The McMurdo Dry Valleys Long-Term Ecological Research Program: new understanding of the biogeochemistry of the Dry Valley lakes: a review.}, journal = {Polar Geography}, volume = {25}, year = {2001}, pages = {202-217}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Kathleen A. Welch and John C. Priscu and Johanna Laybourn-Parry and Daryl L. Moorhead and Diane M. McKnight and Peter T. Doran and Martyn Tranter} } @phdthesis {1366, title = {Modeling hyporheic exchange influences on biogeochemical processes in dry valley streams, Antarctica}, volume = {Ph.D.}, year = {2001}, school = {University of Colorado}, type = {doctoral}, abstract = {

The ephemeral streams of the Dry Valleys of Antarctica provide habitat to benthic algal mats, and greatly control the quantity and quality of glacial melt water that enters closed basin Dry Valley lakes. Dry Valley watersheds are composed of streambeds and adjacent hyporheic zones. Hydrologic exchange of water and solutes between the stream and the hyporheic zone has the overall effect of increasing residence time in the stream/hyporheic system. Biogeochemical reactions (e.g. chemical weathering, nutrient assimilation) occur both in the water column and in the hyporheic zone. Field experiments and solute transport modeling were employed to elucidate the effects of rapid hyporheic exchange on biogeochemical cycling in Antarctic streams. The results presented here show that (1) large portions of the wetted zone that surrounds each stream is a hyporheic zone, and that stream water exchanges into and out of extended portions of this zone on the order of weeks, (2) the rapid exchange of stream water between the water column and the hyporheic zone controls the rate of weathering in streambed sediments, and (3) denitrification in streams is limited by the conversion of NO2\ to N2O, while the conversion of NO3\ to NO2\ occurs very quickly.

}, keywords = {LTER-MCM}, author = {Michael N. Gooseff} } @mastersthesis {1419, title = {Regrowth of cyanobacterial mats in Greek Creek and the impact of ecotourism}, volume = {M.S.}, year = {2001}, school = {University of Colorado}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Ethan Chatfield} } @article {1406, title = {Retrospective simulation of lake level rise in Lake Bonney based on recent 21-year record: indication of recent climate change in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Paleolimnology}, volume = {25}, year = {2001}, pages = {477-492}, keywords = {LTER-MCM, Climate Response}, author = {Bomblies, Arne and Diane M. McKnight and Edmund D. Andrews} } @mastersthesis {1413, title = {Sensitivity of carbon dynamics to changing light availability of benthic microbial mats in Lake Hoare, Antarctica}, volume = {M.S.}, year = {2001}, school = {University of Toledo}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Schmeling, J} } @article {1408, title = {Spectrofluorometric characterization of aquatic fulvic acid for determination of precursor organic material and general structural properties.}, journal = {Limnology and Oceanography}, volume = {46}, year = {2001}, pages = {38-48}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Elizabeth W. Boyer and Paul K. Westerhoff and Peter T. Doran and Thomas Kulbe and Dale T. Andersen} } @mastersthesis {1424, title = {Active layer dynamics and hyporheic zone storage in three streams in the McMurdo Dy Valleys, Antarctica}, volume = {M.S.}, year = {2000}, school = {University of Colorado}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Peter A. Conovitz} } @inbook {1426, title = {Climate and hydrologic variations and implications for lake and stream ecological response in the McMurdo Dry Valleys, Antarctica}, booktitle = {Climate Variability and Ecosystem Response at Long Term Ecological Research Sites}, year = {2000}, pages = {174-195}, publisher = {Oxford University Press}, organization = {Oxford University Press}, keywords = {LTER-MCM}, author = {Kathleen A. Welch and W. Berry Lyons and Diane M. McKnight and Chris Jaros and Andrew G Fountain and Thomas H. Nylen and Peter T. Doran and Clive Howard-Williams}, editor = {D. Greenland and D. G. Goodin and R. C. Smith} } @mastersthesis {1440, title = {Dynamics of the deep chlorophyll maximum within the lakes of the McMurdo Dry Valleys, Antarctica}, volume = {M.S.}, year = {2000}, school = {University of Toledo}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Burnett, L} } @inbook {1429, title = {Experimental Approaches to Investigate Belowground Animal Diversity}, booktitle = {Methods in Ecosystem Science}, year = {2000}, pages = {318-329}, publisher = {Springer Verlag}, organization = {Springer Verlag}, address = {New York}, keywords = {LTER-MCM}, author = {Diana W. Freckman and Reichman, O}, editor = {Osvaldo E. Sala and Jackson, R and Mooney, H and R. Howarth} } @article {1441, title = {Global biodiversity scenarios for the year 2100}, journal = {Science}, volume = {287}, year = {2000}, pages = {1770-1774}, keywords = {LTER-MCM}, doi = {LTER}, author = {Osvaldo E. Sala and Kinzig, A and Leemans, R and Lodge, D and Mooney, H and Oesterheld, M and Poff, N and Sykes, M and Walker, B and Walkder, M and Diana H. Wall and F. S. Chapin and Armesto, J and Berlow, E and Bloomfield, J and Dirzo, R and Huber-Sanwald, E and Huenneke, L and Jackson, R} } @article {1422, title = {Phytoplankton dynamics in a stably stratified Antarctic lake during winter darkness}, journal = {Journal of Phycology}, volume = {36}, year = {2000}, month = {10/2000}, pages = {852-861}, type = {Journal}, keywords = {LTER-MCM, Biggie, winter}, doi = {10.1046/j.1529-8817.2000.00031.x}, author = {Diane M. McKnight and B. L. Howes and C. D. Taylor and D. D. Goehringer} } @article {1421, title = {Stratification and dynamics of microbial loop communities in Lake Fryxell, Antarctica}, journal = {Freshwater Biology}, volume = {44}, year = {2000}, month = {12/2001}, pages = {649-661}, type = {Journal}, keywords = {LTER-MCM, Biggie, protozoa}, doi = {10.1046/j.1365-2427.2000.00612.x}, url = {http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2427.2000.00612.x/abstract}, author = {Emily C. Roberts and Johanna Laybourn-Parry and Diane M. McKnight and Novarino, G} } @article {1456, title = {Dry Valley streams in Antarctica: ecosystems waiting for water}, journal = {Bioscience}, volume = {49}, year = {1999}, pages = {985-995}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Dev K. Niyogi and Alexander S. Alger and Bomblies, Arne and Peter A. Conovitz and Cathy M. Tate} } @article {1459, title = {Geomicrobiology of sub-glacial ice above Vostok Station}, journal = {Science}, volume = {286}, year = {1999}, pages = {2141-2144}, keywords = {LTER-MCM}, doi = {10.1126/science.286.5447.2141}, author = {John C. Priscu and Edward E. Adams and W. Berry Lyons and Mary A. Voytek and David W. Mogk and Robert L. Brown and Christopher P. McKay and Cristina D. Takacs-Vesbach and Kathleen A. Welch and Craig F. Wolf and Julie D. Kirshtein and Recep Avci} } @article {1462, title = {Interactions underground: soil biodiversity, mutalism and ecosystem processes}, journal = {Bioscience}, volume = {49}, year = {1999}, pages = {109-119}, keywords = {LTER-MCM}, doi = {LTER}, author = {Diana H. Wall and John C. Moore} } @article {1447, title = {Physical controls on the Taylor Valley Ecosystem, Antarctica}, journal = {BioScience}, volume = {49}, year = {1999}, month = {12/1999}, pages = {961-972}, type = {Journal}, keywords = {LTER-MCM, Water availability}, author = {Andrew G Fountain and W. Berry Lyons and Melody B. Burkins and Gayle L. Dana and Peter T. Doran and Karen J. Lewis and Diane M. McKnight and Daryl L. Moorhead and Andrew N. Parsons and John C. Priscu and Diana H. Wall and Robert A. Wharton Jr. and Ross A. Virginia} } @article {1481, title = {Analysis of transient storage subject to unsteady flow: diel flow variation in an Antarctic stream}, journal = {Journal of the North American Benthological Society}, volume = {17}, year = {1998}, month = {06/1998}, pages = {143-154}, keywords = {LTER-MCM}, url = {http://www.jstor.org/stable/1467958}, author = {Robert L. Runkel and Diane M. McKnight and Edmund D. Andrews} } @article {1483, title = {Antarctic paleolake sediments and the search for extinct life on Mars}, journal = {Journal of Geophysical Research-Planets}, volume = {103}, year = {1998}, month = {05/1998}, pages = {28481-28493}, keywords = {LTER-MCM}, doi = {10.1029/98JE01713}, author = {Peter T. Doran and Robert A. Wharton Jr. and David J. DesMarais and Christopher P. McKay} } @mastersthesis {1537, title = {Climatic controls on streamflow generation from Antarctic glaciers}, volume = {M.S.}, year = {1998}, school = {University of Colorado Boulder}, type = {masters}, address = {Boulder, CO}, keywords = {LTER-MCM}, author = {Bomblies, Arne and Diane M. McKnight} } @article {1493, title = {Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica}, journal = {Antarctic Science}, volume = {10}, year = {1998}, pages = {124-133}, keywords = {LTER-MCM}, author = {Dale T. Andersen and Christopher P. McKay and Robert A. Wharton Jr.} } @inbook {1499, title = {Geochemical Linkages Among Glaciers, Streams, and Lakes Within the Taylor Valley, Antarctica}, booktitle = {Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, volume = {72}, year = {1998}, pages = {77-92}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Kathleen A. Welch and Klaus Neumann and Jeffrey K. Toxey and Robyn McArthur and Changela Williams and Diane M. McKnight and Daryl L. Moorhead} } @inbook {1500, title = {Glaciers of the McMurdo Dry Valleys, Southern Victoria Land, Antarctica}, booktitle = {Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, series = {Antarctic Research Series}, volume = {72}, year = {1998}, pages = {65-75}, keywords = {LTER-MCM}, author = {Andrew G Fountain and Gayle L. Dana and Karen J. Lewis and Bruce H. Vaughn and Diane M. McKnight} } @inbook {1501, title = {Hydrologic Processes Influencing Streamflow Variation in Fryxell Basin, Antarctica}, booktitle = {Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, series = {Antarctic Research Series}, volume = {72}, year = {1998}, pages = {93-108}, keywords = {LTER-MCM}, author = {Peter A. Conovitz and Diane M. McKnight and Lee H. MacDonald and Andrew G Fountain}, editor = {Harold R. House} } @article {1502, title = {Inorganic carbon-isotope distribution and budget in the Lake Hoare and Lake Fryxell basins, Taylor Valley, Antarctica}, journal = {Annals of Glaciology}, volume = {27}, year = {1998}, pages = {685-690}, keywords = {LTER-MCM}, author = {Klaus Neumann and W. Berry Lyons and D.J. Des Marais} } @article {1503, title = {A late holocene dessication of Lake Hoare and Lake Fryxell, McMurdo Dry Valleys, Antarctica}, journal = {Antarctic Science}, volume = {10}, year = {1998}, pages = {247-256}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Scott W. Tyler and Robert A. Wharton Jr. and Diane M. McKnight and Bruce H. Vaughn} } @article {1504, title = {Longitudinal Patterns in Algal Abundance and Species Distribution in Meltwater Streams in Taylor Valley, Southern Victoria Land, Antarctica, in Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, journal = {Antarctic Research Series}, volume = {72}, year = {1998}, pages = {109-127}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Alexander S. Alger and Cathy M. Tate and Gordon H Shupe and Sarah A. Spaulding} } @article {1505, title = {The McMurdo Dry Valley Ecosystem: Organization, Controls, and Linkages, in Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, journal = {Antarctic Research Series}, volume = {72}, year = {1998}, pages = {351-363}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and John C. Priscu} } @article {1508, title = {McMurdo Dry Valleys LTER: Stream discharge as a function of ambient temperature and incoming shortwave radiation in Taylor Valley, Antarctica}, journal = {Antarctic Journal of the United States - 1996 Review Issue (NSF 98-28)}, volume = {31}, year = {1998}, pages = {196-197}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and Diane M. McKnight} } @article {1515, title = {Mercury speciation and distribution in a polar desert lake (Lake Hoare, Antarctica) and two glacial meltwater streams}, journal = {Science of the Total Environment}, volume = {213}, year = {1998}, pages = {229-237}, keywords = {LTER-MCM}, author = {Vandal, G.M. and R.P. Mason and Diane M. McKnight and W. Fitzgerald} } @article {1517, title = {Modeling Nitrogen Transformations in Dry Valley Streams, Antarctica, in Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, journal = {Antarctic Research Series}, volume = {72}, year = {1998}, pages = {141-151}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and Diane M. McKnight and Cathy M. Tate} } @article {1482, title = {Perennial Antarctic Lake Ice: An Oasis for Life in a Polar Desert}, journal = {Science}, volume = {280}, year = {1998}, month = {06/1998}, pages = {2095-2098}, type = {Journal}, keywords = {LTER-MCM, Biggie}, doi = {10.1126/science.280.5372.2095}, url = {http://www.sciencemag.org/content/280/5372/2095.short}, author = {John C. Priscu and Christian H. Fritsen and Edward E. Adams and Stephen J. Giovannoni and Hans W. Paerl and Christopher P. McKay and Peter T. Doran and Douglas A. Gordon and Brian D. Lanoil and James L. Pinckney} } @inbook {1522, title = {Permanent Ice Covers of the McMurdo Dry Valleys Lakes, Antarctica: Liquid Water Contents}, booktitle = {Ecosystem Processes in a Polar Desert: The McMurdo Dry Valleys, Antarctica}, series = {Antarctic Research Series}, volume = {72}, year = {1998}, pages = {269-280}, keywords = {LTER-MCM}, author = {Christian H. Fritsen and Edward E. Adams and Christopher P. McKay and John C. Priscu} } @mastersthesis {1541, title = {Spatial-temporal patterns of primary production in phytoplankton communities of Taylor Valley lakes, Antartica: A modelling synthesis}, volume = {M.S.}, year = {1998}, school = {Texas Tech University}, type = {masters}, keywords = {LTER-MCM}, doi = {LTER}, author = {Davis, W} } @article {1532, title = {Structure and composition of the photochemical apparatus of the Antarctic green alga Chlamydomonas subcaudata}, journal = {Photosynthesis Research - Regular Paper}, volume = {56}, year = {1998}, pages = {303-314}, keywords = {LTER-MCM}, author = {Morgan, Rachael M. and Alexander G. Ivanov and John C. Priscu and Denis P. Maxwell and Norman P.A. Huner} } @article {1546, title = {Canada Stream: a glacial meltwater stream in Taylor Valley, South Victoria Land, Antarctica}, journal = {Journal of the North American Benthological Society}, volume = {16}, year = {1997}, pages = {14-17}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Cathy M. Tate} } @inbook {1548, title = {Carbon dynamics of aquatic microbial mats in the Antarctic dry valleys: A modelling synthesis}, booktitle = {Ecosystem Processes in Antarctic Ice-free Landscapes}, year = {1997}, pages = {181-196}, publisher = {Balkema Press, Rotterdam}, organization = {Balkema Press, Rotterdam}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and W. Shane Davis and Robert A. Wharton Jr.} } @inbook {1549, title = {Chemical weathering rates and reactions in the Lake Fryxell Basin, Taylor Valley : Comparison to temperate river basins}, booktitle = {Ecosystem Processes in Antarctic Ice-free Landscapes}, year = {1997}, pages = {147-154}, publisher = {Balkema Press, Rotterdam}, organization = {Balkema Press, Rotterdam}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Kathleen A. Welch and C. A. Nezat and K. Crick and Jeffrey K. Toxey and J.A. Mastrine and Diane M. McKnight} } @inbook {1550, title = {Climate history of the McMurdo Dry Valleys since the last glacial maximum: A synthesis}, booktitle = {Ecosystem Processes in Antarctic Ice-free Landscapes}, year = {1997}, pages = {155-162}, publisher = {Balkema Press, Rotterdam}, organization = {Balkema Press, Rotterdam}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Louis R. Bartek and Paul A. Mayewski and Peter T. Doran} } @article {1553, title = {Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica}, journal = {Journal of Paleolimnology}, volume = {17}, year = {1997}, pages = {403-420}, keywords = {LTER-MCM}, author = {Sarah A. Spaulding and Diane M. McKnight and E.F. Stoermer and Peter T. Doran} } @inbook {1554, title = {Ecological processes in a cold desert ecosystem: the abundance and species distribution of algal mats in glacial meltwater streams in Taylor Valley}, booktitle = {Institute of Arctic and Alpine Research}, series = {Occasional Paper}, volume = {51}, year = {1997}, pages = {108 pp}, publisher = {University of Colorado}, organization = {University of Colorado}, keywords = {LTER-MCM}, url = {http://instaar.colorado.edu/other/download/OP51-ECOLOGICAL-PROCESSES.pdf}, author = {Alexander S. Alger and Diane M. McKnight and Sarah A. Spaulding and Cathy M. Tate}, editor = {Gordon H Shupe and Kathleen A. Welch and R. L. Edwards and Edmund D. Andrews} } @article {1555, title = {Impact of Light Regimes on Productivity Patterns of Benthic Microbial Mats in an Antarctic Lake: A Modeling Study}, journal = {Limnology and Oceanography}, volume = {42}, year = {1997}, pages = {1561-1569}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and Craig F. Wolf and Robert A. Wharton Jr.} } @article {1560, title = {The microbial plankton of Lake Fryxell, southern Victoria Land, Antarctica during the summers of 1992 and 1994}, journal = {Polar Biology}, volume = {17}, year = {1997}, pages = {54-61}, keywords = {LTER-MCM}, author = {Johanna Laybourn-Parry and Mark R. James and Diane M. McKnight and John C. Priscu and Sarah A. Spaulding and Russell Shiel} } @article {1542, title = {Open-top Designs for Manipulating Field Temperature in High-Latitude Ecosystems}, journal = {Global Change Biology}, volume = {3}, year = {1997}, month = {12/1997}, pages = {20-32}, keywords = {LTER-MCM}, doi = {10.1111/j.1365-2486.1997.gcb136.x}, author = {G. M. Marion and G.H.R. Henry and Diana W. Freckman and J. Johnstone and G. Jones and M.H. Jones and E. Levesque and U. Molau and P. M{\O}LGAARD and Andrew N. Parsons and J. Svoboda and Ross A. Virginia} } @inbook {1564, title = {Species composition and primary production of algal communities in Dry Valley streams in Antarctica: Examination of the functional role of biodiversity}, booktitle = {Ecosystem Processes in Antarctic Ice-free Landscapes}, year = {1997}, pages = {171-179}, publisher = {Balkema Press, Rotterdam}, organization = {Balkema Press, Rotterdam}, keywords = {LTER-MCM}, author = {Dev K. Niyogi and Cathy M. Tate and Diane M. McKnight and John H. Duff and Alexander S. Alger} } @article {1569, title = {Determination of major element chemistry in terrestrial waters from Antarctica by ion chromatography}, journal = {Journal of Chromatography A}, volume = {739}, year = {1996}, pages = {257-263}, keywords = {LTER-MCM}, author = {Kathleen A. Welch and W. Berry Lyons and Graham, E and Klaus Neumann and James M. Thomas and D. Mikesell} } @article {1572, title = {Extreme Supersaturation of Nitrous Oxide in a Poorly Ventilated Antarctic Lake}, journal = {Limnol. Oceanogr}, volume = {41}, year = {1996}, pages = {1544-1551}, keywords = {LTER-MCM}, author = {John C. Priscu and Malcolm T. Downes and Christopher P. McKay} } @article {1574, title = {Geochemistry of aquatic humic substances in the Lake Fryxell Basin, Antarctica}, journal = {Biogeochemistry}, volume = {34}, year = {1996}, pages = {157-188}, keywords = {LTER-MCM}, author = {George R. Aiken and Diane M. McKnight and Richard A. Harnish and Robert Wershaw} } @article {1576, title = {Microcosms and Soil Ecology: Critical Linkages Between Field Studies and Modelling Food Webs}, journal = {Ecology}, volume = {77}, year = {1996}, pages = {694-705}, keywords = {LTER-MCM}, author = {John C. Moore and Peter C. De Ruiter and H. William Hunt and David C. Coleman and Diana W. Freckman} } @article {1587, title = {The influence of stream channel characteristics on streamflow and annual water budgets for lakes in Taylor Valley}, journal = {Antarctic Journal of the U.S.}, volume = {30}, year = {1995}, pages = {284-287}, keywords = {LTER-MCM}, author = {Harold R. House and Diane M. McKnight and Paul Von Guerard} } @article {1589, title = {McMurdo LTER: Algal mat distribution in glacial meltwater streams in Taylor Valley, southern Victoria Land, Antarctica}, journal = {Antarctic Journal of the United States}, volume = {30}, year = {1995}, pages = {287-289}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Cathy M. Tate} } @article {1594, title = {McMurdo LTER: Species composition and spatial distribution of algal mats in Green Creek, Taylor Valley, Antarctica}, journal = {Antarctic Journal of the U. S.}, volume = {30}, year = {1995}, pages = {289-291}, keywords = {LTER-MCM}, author = {Alexander S. Alger and Sarah A. Spaulding and Gordon H Shupe and Diane M. McKnight} } @article {1596, title = {Paleolakes on Mars}, journal = {Journal of Paleolimnology}, volume = {13}, year = {1995}, pages = {267-283}, keywords = {LTER-MCM}, author = {Robert A. Wharton Jr. and J. Crosby and Christopher P. McKay and J. Rice} } @article {1606, title = {Streamflow, water-temperature, and specific-conductance data for selected streams draining into Lake Fryxell, Lower Taylor Valley, Victoria Land, Antarctica, 1990-92}, journal = {U.S. Geological Survey. Open-File Report 94-545}, year = {1995}, keywords = {LTER-MCM}, author = {Paul Von Guerard and Diane M. McKnight and Richard A. Harnish and J. W. Gartner and Edmund D. Andrews} } @article {1611, title = {Aquatic fulvic acids in algal-rich antarctic ponds}, journal = {Limnology and Oceanography}, volume = {39}, year = {1994}, month = {07/1994}, pages = {1972-1979}, keywords = {LTER-MCM, Biggie}, author = {Diane M. McKnight and Edmund D. Andrews and Sarah A. Spaulding and George R. Aiken} } @article {1612, title = {Light transmission and reflection in perennially ice-covered Lake Hoare, Antarctica}, journal = {Journal Geophysics Research}, volume = {99}, year = {1994}, month = {06/1994}, pages = {20427-20444}, keywords = {LTER-MCM}, doi = {10.1029/94JC01414}, author = {Christopher P. McKay and Gary D. Clow and Dale T. Andersen and Robert A. Wharton Jr.} } @article {1617, title = {McMurdo LTER: Inorganic geochemical studies with special reference to calcium carbonate dynamics}, journal = {Antarctic Journal of the U.S.}, volume = {29}, year = {1994}, pages = {237-239}, keywords = {LTER-MCM}, author = {Kathleen A. Welch and W. Berry Lyons and John C. Priscu and R. L. Edwards and Diane M. McKnight and Harold R. House and Robert A. Wharton Jr.} } @article {1619, title = {McMurdo LTER: Primary production model of benthic microbial mats in Lake Hoare, Antarctica}, journal = {Antarctic Journal of the U.S.}, volume = {29}, year = {1994}, pages = {241-243}, keywords = {LTER-MCM}, author = {Daryl L. Moorhead and Robert A. Wharton Jr.} } @article {1620, title = {McMurdo LTER: Streamflow Measurements in Taylor Valley}, journal = {Antarctic Journal of the United States}, volume = {29}, year = {1994}, pages = {230-232}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Harold R. House and Paul Von Gerard} } @article {1627, title = {Phytoplankton population dynamics in perennially ice-covered Lake Fryxell, Antarctica}, journal = {Journal of Plankton Research}, volume = {16}, year = {1994}, pages = {527-541}, keywords = {LTER-MCM}, author = {Sarah A. Spaulding and Diane M. McKnight and Richard L. Smith and Richard Dufford} } @inbook {1628, title = {Stromatolite mats in Antarctic lakes}, booktitle = {Phanerozoic Stromatolites II}, year = {1994}, publisher = {Kluwer, Netherlands}, organization = {Kluwer, Netherlands}, keywords = {LTER-MCM}, author = {Robert A. Wharton Jr.} } @article {1632, title = {Dissolved Organic Material in Dry Valley Lakes: A Comparison of Lake Fryxell, Lake Hoare, and Lake Vanda, in Physical and Biogeochemical Processes in Antarctic Lakes}, journal = {Antarctic Research Series}, volume = {59}, year = {1993}, pages = {119-133}, keywords = {LTER-MCM}, author = {Diane M. McKnight and George R. Aiken and Edmund D. Andrews and E. C. Bowles and Richard A. Harnish} } @article {1636, title = {The geochemical evolution of terrestrial waters in the antarctic: the role of rock-water interactions, in Physical and Biogeochemical Processes in Antarctic Lakes}, volume = {59}, year = {1993}, pages = {135-143}, keywords = {LTER-MCM}, author = {W. Berry Lyons and Paul A. Mayewski} } @article {1642, title = {Perennial ice covers and their influence on antarctic lake ecosystems, in Physical and Biogeochemical Processes in Antarctic Lakes}, journal = {Antarctic Research Series}, volume = {59}, year = {1993}, pages = {53-70}, keywords = {LTER-MCM}, author = {Robert A. Wharton Jr. and Christopher P. McKay and Gary D. Clow and Dale T. Andersen} } @article {1644, title = {Potential hydrologic and geochemical consequences of the 1992 merging of Lake Chad with Lake Hoare in Taylor Valley}, journal = {Antarctic Journal of the U.S.}, volume = {28}, year = {1993}, pages = {249-251}, keywords = {LTER-MCM}, author = {Diane M. McKnight and Edmund D. Andrews} } @article {1645, title = {Stable isotopic biogeochemistry of carbon and nitrogen in a perennially ice-covered Antarctic lake}, journal = {Chemical Geology}, volume = {107}, year = {1993}, pages = {159-172}, keywords = {LTER-MCM}, author = {Robert A. Wharton Jr. and W. Berry Lyons and D.J. Des Marais} }