@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 {4589, title = {How long do population level field experiments need to be? Utilising data from the 40-year-old LTER network}, journal = {Ecology Letters}, year = {2021}, month = {02/2021}, abstract = {

We utilise the wealth of data accessible through the 40-year-old Long-Term Ecological Research (LTER) network to ask if aspects of the study environment or taxa alter the duration of research necessary to detect consistent results. To do this, we use a moving-window algorithm. We limit our analysis to long-term (\> 10 year) press experiments recording organismal abundance. We find that studies conducted in dynamic abiotic environments need longer periods of study to reach consistent results, as compared to those conducted in more moderated environments. Studies of plants were more often characterised by spurious results than those on animals. Nearly half of the studies we investigated required 10 years or longer to become consistent, where all significant trends agreed in direction, and four studies (of 100) required longer than 20 years. Here, we champion the importance of long-term data and bolster the value of multi-decadal experiments in understanding, explaining and predicting long-term trends.

}, keywords = {LTER-MCM, data mining, isothermality, long-term, moving window, population dynamics, time series, trajectory}, doi = {10.1111/ele.13710}, url = {https://onlinelibrary.wiley.com/doi/10.1111/ele.13710}, author = {Cusser, Sarah and Helms, Jackson and Bahlai, Christie A. and Haddad, Nick M.} } @mastersthesis {4588, title = {Hydrologic response to foehn winds in the McMurdo Dry Valleys, Southern Victoria Land, Antarctica}, volume = {M.S.}, year = {2021}, month = {2020}, school = {University of Colorado Boulder}, type = {masters}, address = {Boulder, CO}, abstract = {

In the McMurdo Dry Valleys (MDVs), foehn winds are a principal vector of landscape connectivity that facilitate movement of materials between glaciers, streams, soils, lakes and other parts of the ecosystem. While previous publications show that turbulent, warm and dry foehn winds indirectly relate to an increase in lake level rise via an increase in degree days above freezing (DDAF), the direct quantified impact of foehn winds to streamflow and lake level rise remains unclear. The MDVs are the largest ice-free region of Antarctica, which experience minimal precipitation. Valley bottoms contain permanently ice-covered closed basin lakes filled with meltwater from outlet glaciers via stream channels. In Taylor Valley, several meteorological stations and lake monitoring stations record average measurements of weather conditions and lake conditions on 15 to 20-minute intervals. In this thesis, the meteorological definition of foehn winds is refined and hydrologic response to foehn winds is evaluated. During the austral summer streamflow season (November - February), foehn winds are predicted to increase meltwater generation and closed-basin lake level rise. Past publications have shown that foehn wind events contribute to lake ice sublimation year-round, whereas melt does not typically occur in nonsummer months. Analysis of non-summer lake ice ablation utilizing recent lake stage and ablation data is also explored herein. Although a significant correlation was not found, summer foehn winds appear to promote above average daily lake level rise given sufficient air temperatures. Daily average lake level rise is greater for longer periods (i.e., 4-day average daily rise \> 3-day average daily rise, etc.) indicating that there is at least a 4-day post-foehn impact on lake level rise during the summer. Lake ice ablation in non-summer months is shown to have a significant relationship with increasing foehn wind occurrence and wind-run. Because foehn winds are expected to increase with global warming, these hydrologic relationships aid in predicting the future of the McMurdo Dry Valley ecosystem in a warming world.

}, keywords = {LTER-MCM, Antarctica, foehn, foehn winds, hydrologic, katabatic, McMurdo, wind}, url = {https://www.proquest.com/docview/2488126937}, author = {Beane, Samuel J. and Michael N. Gooseff} } @phdthesis {4761, title = {Heterotrophic protists as useful models for studying microbial food webs in a model soil ecosystem and the universality of complex unicellular life}, volume = {PhD}, year = {2019}, school = {Brigham Young University}, type = {doctoral}, address = {Provo, UT}, abstract = {

Heterotrophic protists, consisting largely of the Cercozoa, Amoebozoa, Ciliophora, Discoba and some Stramenopiles, are a poorly characterized component of life on Earth. They play an important ecological role in soil communities and provide key insights into the nature of one of life\’s most enigmatic evolutionary transitions: the development of the complex unicell. Soil ecosystems are crucial to the functioning of global biogeochemical cycles (e.g. carbon and nitrogen) but are at risk of drastic change from anthropogenic climate change. Heterotrophic protists are the primary regulators of bacterial diversity in soils and as such play integral roles in biogeochemical cycling, nutrient mobilization, and trophic cascades in food webs under stress. Understanding the nature of these changes requires examining the rates, diversity, and resiliency of interactions that occur between soil organisms. However, soils are the most taxonomically diverse ecosystems on Earth and disentangling the complexities of dynamic and varied biotic interactions in them requires a unique model system. The McMurdo Dry Valleys of Antarctica, one of the harshest terrestrial environments on Earth, serve as a model soil ecosystem owing to their highly reduced biological diversity. Exploring the functioning of heterotrophic protists in these valleys provides a way to test the applicability of this model system to other soil food webs. However, very little is known about their taxonomic diversity, which is a strong predictor of function. Therefore, I reviewed the Antarctic literature to compile a checklist of all known terrestrial heterotrophic protists in Antarctica. I found significant geographical, methodological, and taxonomic biases and outlined how to address these in future research programs. I also conducted a molecular survey of whole soil communities using 18 shotgun metagenomes representing major landscape features of the McMurdo Dry Valleys. The results revealed the dominance of Cercozoa and point to an Antarctic heterotrophic protist soil community that is taxonomically diverse and reflects the structure and composition of communities at lower latitudes. To investigate whether biotic interactions or abiotic factors were a larger driver for Antarctic heterotrophic protists, I conducted variation partitioning using environmental data (e.g. moisture, pH and electrical conductivity). Biotic variables were more significant and accounted for more of the variation than environmental variables. Taken together, it is clear that heterotrophic protists play key ecological roles in this ecosystem. Deeper insights into the ecology of these organisms in the McMurdo Dry Valleys also have implications for the search for complex unicellular life in our universe. I discuss the theoretical underpinnings of searching for these forms of life outside of Earth, conclude that they are likely to occur, and postulate how future missions could practically search for complex unicells.

}, keywords = {LTER-MCM, heterotrophic soil protists, key evolutionary innovations, life on Mars, McMurdo Dry Valleys, network analysis, shotgun metagenomics, universal complex unicellular life}, url = {https://www.proquest.com/docview/2310631977}, author = {Thompson, Andrew R.}, editor = {Adams, Byron J.} } @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} } @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} } @phdthesis {4161, title = {Hydrologic connectivity in the McMurdo Dry Valleys, Antarctica: Water-mediated mass and energy fluxes in streams and soils}, volume = {Ph.D.}, year = {2017}, school = {University of Colorado Boulder}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Chapter 1 synthesizes 20 years of stream gauge observations (discharge, water temperature, and specific conductance) to assess patterns of hydrologic connectivity between glaciers, streams and lakes. Results reveal hydrologic patterns across daily, annual and inter-annual timescales, which together characterize the hydrologic regime of MDV streams. Also, stream gauge data display a relationship between stream length and hydrologic regime. Longer streams are more intermittent, warmer, and saltier than shorter streams. This work provides physical context for understanding biological differences among MDV streams, while providing a methodological template for quantifying hydrologic connectivity.

Chapter 2 investigates the nature of concentration-discharge relationships for weathering-derived solutes in MDV streams. The relative simplicity of MDV \“watersheds\” permits the use of concentration-discharge relationships to infer hydrologic and chemical mixing dynamics occurring along the river corridor. Long-term stream geochemical data show that weathering derived solutes exhibit chemostatic C-Q relationships. Chemostasis implies that rates of solute production and/or mobilization scale proportionately with stream discharge. A numerical weathering and solute transport model suggests that chemostasis is maintained by a positive relationship between weathering rate and discharge along the stream corridor.

Finally, Chapters 3 and 4 investigate water-mediated energy fluxes within the soil habitat. Nematode communities in MDV are highly sensitive to the thermodynamic regime of active layer soils. Soil moisture and air temperature data were collected across natural wetness gradients adjacent to fluvial features to assess the control of soil moisture on the soil thermal regime. Observations show that wetter soils freeze less frequently and more gradually than drier soils. Also, a numerical soil heat transfer model suggests that increases in soil moisture and air temperature result in warmer average habitat temperature, an extension of the duration of time the soil habitat spends above freezing, and a reduction in the rate and frequency of freezing. The results of this chapter provide a physical context for understanding current and future patterns of ecosystem structure and function in MDV soils.

}, keywords = {LTER-MCM}, url = {https://scholar.colorado.edu/cven_gradetds/77/}, author = {Wlostowski, Adam and Michael N. Gooseff} } @article {4015, title = {High levels of intraspecific genetic divergences revealed for Antarctic springtails: evidence for small-scale isolation during Pleistocene glaciation}, journal = {Biological Journal of the Linnean Society}, volume = {119}, year = {2016}, month = {Jan-09-2016}, pages = {166 - 178}, keywords = {LTER-MCM}, doi = {10.1111/bij.12796}, url = {https://academic.oup.com/biolinnean/article-lookup/doi/10.1111/bij.12796https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111\%2Fbij.12796}, author = {Bennett, Kristi R. and Hogg, Ian D. and Byron Adams and Hebert, Paul D. N.} } @article {3707, title = {High-resolution ground-penetrating radar profiles of perennial lake ice in the McMurdo Dry Valleys, Antarctica: Horizon attributes, unconformities, and subbottom penetration}, journal = {GEOPHYSICS}, volume = {81}, year = {2016}, month = {01/2016}, pages = {WA13 - WA20}, keywords = {LTER-MCM}, issn = {0016-8033}, doi = {10.1190/geo2015-0159.1}, url = {http://library.seg.org/doi/10.1190/geo2015-0159.1}, author = {Hilary A. Dugan and Arcone, Steven A. and Maciek K. Obryk and Peter T. Doran} } @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 {4091, title = {Hydrological and Biogeochemical Modeling of Taylor Valley Lakes, East Antarctica}, volume = {Ph.D.}, year = {2014}, school = {University of Illinois}, type = {doctoral}, address = {Chicago, IL}, abstract = {

Taylor Valley, McMurdo Dry Valleys, East Antarctica contains three perennially ice-covered lakes located in closed basins. The lakes respond to climatic changes on seasonal and decadal scales due to their existence on a very narrow climatic spectrum. The climate has to be sufficiently warm during the austral summer to induce glacial melt yet cold enough to maintain the ice covers year round. This thesis is focused on better understanding and constraining the sensitivity of past and present lakes to changes in climatic forcings. Melt water generation for large proglacial lakes, that existed during the Last Glacial Maximum, is attributed to strong westerly winds that increase surface air temperature above freezing, prolonging the melt season. The high frequency of westerly winds during the Last Glacial Maximum, based on the ice core record from Taylor Dome, is responsible for generation of enough glacial melt to sustain large proglacial lakes during this time period, suggesting that summer surface air temperatures were as warm as present day. Contemporary lakes are much smaller, however, the effect of strong westerly winds on modern lakes is equally profound. Strong winds are responsible for aeolian sediment deposition on the surface of the ice covers. The deposited sediment, on the other hand, absorbs more solar radiation and preferentially decreases the ice thickness around it. The localized ice thinning allows a greater amount of light penetration into the water column, which is negatively correlated with chlorophyll-a concentration. This negative correlation does not indicate changes in biomass; rather, it is a result of the short-term photo-adaptation of phytoplankton to the light intensity by increasing/decreasing light harvesting antenna size. The ice thicknesses in Taylor Valley lakes have been fluctuating since the first measurements were obtained. A one-dimensional physics-based ice thickness model was developed capable of reproducing 16 years of ice thickness trends for two different lakes. The model is based on surface radiative fluxes while considering heat fluxes from the water column. Deep lakes with well-developed temperature maximum can facilitate or hinder ice thickness growth/decay due to the heat flux from the underlying water column. This finding suggests that not all perennially ice-covered lakes can be used as a proxy for climatic changes.

}, keywords = {LTER-MCM}, url = {http://hdl.handle.net/10027/18909}, author = {Maciek K. Obryk}, editor = {Peter T. Doran} } @article {3209, title = {Hyperspectral measurements of wet, dry and saline soils from the McMurdo Dry Valleys: soil moisture properties from remote sensing}, journal = {Antarctic Science}, volume = {26}, year = {2014}, month = {10/2014}, pages = {565 - 572}, abstract = {

Soil moisture is a spatially heterogeneous quantity in the McMurdo Dry Valleys of Antarctica that exerts a large influence on the biological community and on the thermal state of Dry Valleys permafrost. The goal of this project was to determine whether hyperspectral remote sensing techniques could be used to determine soil moisture conditions in the Dry Valleys. We measured the spectral reflectance factors of wetted soil samples from the Dry Valleys under natural light conditions and related diagnostic spectral features to surface layer soil moisture content. Diagnostic water absorption features in the spectra at 1.4 \µm and 1.9 \µm were present in all samples, including samples doped with high concentrations of chloride salts. The depth of the 1.4 \µm absorption is shown to increase linearly with increasing gravimetric water content. These results suggest that airborne hyperspectral imaging of the Dry Valleys could generate soil moisture maps of this environment over large spatial areas using non-invasive remote-sensing techniques.

}, keywords = {LTER-MCM}, issn = {0954-1020}, doi = {10.1017/S0954102013000977}, url = {http://www.journals.cambridge.org/abstract_S0954102013000977}, author = {Joseph S. Levy and Nolin, Anne and Andrew G Fountain and Head, James W.} } @article {1095, title = {How big are the McMurdo Dry Valleys? Estimating ice-free area using Landsat image data}, journal = {Antarctic Science}, volume = {25}, year = {2013}, month = {02/2013}, pages = {119 - 120}, keywords = {LTER-MCM}, doi = {10.1017/S0954102012000727}, author = {Joseph S. Levy} } @article {1121, title = {Hypersaline {\textquotedblleft}wet patches{\textquotedblright} in Taylor Valley, Antarctica}, journal = {Geophysical Research Letters}, volume = {39}, year = {2012}, month = {03/2012}, keywords = {LTER-MCM}, doi = {10.1029/2012GL050898}, author = {Joseph S. Levy and Andrew G Fountain and Kathleen A. Welch and W. Berry Lyons} } @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} } @mastersthesis {4163, title = {Hydrologic controls of nutrient fluxes in glacial meltwater streams at inter-annual, seasonal, and daily timescales in the McMurdo Dry Valleys, Antarctica}, volume = {M.S.}, year = {2011}, school = {Pennsylvania State University}, type = {masters}, abstract = {

In the McMurdo Dry Valleys of Antarctica, glaciers are hydrologically linked to closed-basin lakes at the valley floor by glacial meltwater streams. Streams flow through porous, well-defined channels with extensive chemically active hyporheic zones. Temporally varying dynamics of meltwater generation and sub-stream thaw depth are thought to control the potential for the hyporheic zone and benthic communities to influence transport of nutrients and dissolved ions downstream. Using the McMurdo LTER database, patterns in stream discharge, electrical conductivity (both with 15-minute sampling intervals), and solute chemistry (weekly sampling intervals) were examined on eight MDV streams from 1990-2008. Discharge and electrical conductivity values were highly variable among streams. Discharge values were highly dependent upon glacial source area, but meteorological and topographical complexities create large variability at all time scales. The longer streams were found to have much higher electrical conductivity values than the shorter streams, suggesting that there are more opportunities for hyporheic weathering reactions along longer stream reaches. Weekly sampled water solutes from each stream\&$\#$39;s entire record were plotted against the discharge recorded at the time when the sample was taken. Silicate concentrations displayed a decreasing logarithmic relationship, while nutrient concentrations had no apparent relationship. This suggests that with the exception to bioreactive solutes, the majority of hyporheic interactions could possibly be characterized by electrical conductivity and discharge. To attain information on in-stream nutrient dynamics and nutrient fluxes, glacial source water at the upper reach of Green Creek and stream outlet water at the lower reach of Green Creek were sampled hourly for two separate diel periods during the 2008-09 austral summer. Both dates were in late January under two distinct flow conditions (~0.5 L/s and ~10 L/s). Under low flow conditions, nutrient cycling was found to be uptake dominated. High flow conditions showed both uptake and regeneration with much higher nutrient loads, but as in the low flow conditions, no apparent temporal trends were found. Nutrient concentrations could not be predicted using the two parameters of discharge and electrical conductivity with in-stream nutrient dynamics likely too complicated at the sub-daily scale.

}, keywords = {LTER-MCM, Antarctica, biogeochemistry, chemical weathering, discharge, electrical conductivity, glacial melt, glaciers, hydrology, hyporheic, MCM LTER, McMurdo Dry Valleys, nutrient fluxes, nutrients, polar desert, solute chemistry, stream chemistry, streamflow, water chemistry}, url = {https://etda.libraries.psu.edu/catalog/11568}, author = {Weaver, Mitchell R. and Michael N. Gooseff} } @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} } @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} } @article {1186, title = {Hydrologic characteristics of lake- and stream-side riparian wetted margins in the McMurdo Dry Valleys, Antarctica}, journal = {Hydrological Processes}, volume = {23}, year = {2009}, pages = {1255-1267}, keywords = {LTER-MCM}, doi = {LTER}, author = {Northcott, M and Michael N. Gooseff and John E. Barrett and Lydia H. Zeglin and Cristina D. Takacs-Vesbach and Humphrey, J} } @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} } @booklet {1242, title = {Hidden Assets: Biodiversity Below-Surface.}, year = {2007}, publisher = {UNESCO-SCOPE Policy Brief $\#$5}, keywords = {LTER-MCM}, doi = {LTER}, url = {http://www.icsu-scope.org/unesco/USPB05_SOIL_En.pdf}, author = {Diana H. Wall and Valerie Behan-Pelletier} } @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} } @article {1460, title = {History of McMurdo Dry Valley Lakes, Antarctica, from stable chlorine isotope data}, journal = {Geology}, volume = {27}, year = {1999}, keywords = {LTER-MCM}, doi = {LTER}, author = {W. Berry Lyons and Frape, S and Kathleen A. Welch} } @article {1479, title = {How soils structure communities in the McMurdo Dry Valleys, Antarctica}, journal = {Bioscience}, volume = {48}, year = {1999}, pages = {973-983}, keywords = {LTER-MCM} } @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} }