02546nas a2200241 4500008004100000022001400041245007500055210006900130260001200199490000700211520184500218653001302063653001102076653001202087653002402099653001902123653001702142100002102159700002402180700002402204700002202228856005402250 2024 eng d a2045-775800aHabitat suitability of biocrust communities in a cold desert ecosystem0 aHabitat suitability of biocrust communities in a cold desert eco c07/20240 v143 a

Drylands are unique among terrestrial ecosystems in that they have a significant proportion of primary production facilitated by non-vascular plants such as colonial cyanobacteria, moss, and lichens, i.e., biocrusts, which occur on and in the surface soil. Biocrusts inhabit all continents, including Antarctica, an increasingly dynamic continent on the precipice of change. Here, we describe in-situ field surveying and sampling, remote sensing, and modeling approaches to assess the habitat suitability of biocrusts in the Lake Fryxell basin of Taylor Valley, Antarctica, which is the main site of the McMurdo Dry Valleys Long-Term Ecological Research Program. Soils suitable for the development of biocrusts are typically wetter, less alkaline, and less saline compared to unvegetated soils. Using random forest models, we show that gravimetric water content, electrical conductivity, and snow frequency are the top predictors of biocrust presence and biomass. Areas most suitable for the growth of dense biocrusts are soils associated with seasonal snow patches. Using geospatial data to extrapolate our habitat suitability model to the whole basin predicts that biocrusts are present in 2.7 × 105 m2 and contain 11–72 Mg of aboveground carbon, based on the 90% probability of occurrence. Our study illustrates the synergistic effect of combining field and remote sensing data for understanding the distribution and biomass of biocrusts, a foundational community in the carbon balance of this region. Extreme weather events and changing climate conditions in this region, especially those influencing snow accumulation and persistence, could have significant effects on the future distribution and abundance of biocrusts and therefore soil organic carbon storage in the McMurdo Dry Valleys.

10abiocrust10acarbon10adryland10ahabitat suitability10aremote sensing10asoil ecology1 aPower, Sarah, N.1 aThomas, Valerie, A.1 aSalvatore, Mark, R.1 aBarrett, John, E. uhttps://onlinelibrary.wiley.com/toc/20457758/14/702764nas a2200253 4500008004100000022001400041245011400055210006900169260001200238300001100250490000700261520197300268653001502241653002102256653002702277653002202304653001502326653001302341100002102354700002502375700002402400700002402424856006202448 2024 eng d a0885-608700aThe hydrologic and geochemical contributions from snow to streamflow in the McMurdo Dry Valleys of Antarctica0 ahydrologic and geochemical contributions from snow to streamflow c06/2024 ae151950 v383 a

The glacial meltwater streams in the McMurdo Dry Valleys (MDVs), Antarctica only flow during the austral summer and contain abundant algal mats which grow at the onset of flow. Their relative abundance in stream channels of this polar desert make the streams biogeochemical hot spots. The MDVs receive minimal precipitation as snow, which is redistributed by wind and deposited in distinct locations, some of which become persistent snow patches each year. Previous studies identified that MDV streamflow comes from a combination of glacier ice and snow, although snow was assumed to contribute little to the overall water budget. This study uses a combination of satellite imagery, terrain analysis, and field measurements to determine where snow patches accumulate and persist across MDV watersheds, and to quantify the potential hydrologic and biogeochemical contributions of snow patches to streams. Watersheds near the coast have the highest snow-covered area and longest snow persistence. Many of these snow patches accumulate within the stream channels, which results in the potential to contribute to streamflow. During the summer of 2021–2022, stream channel snow patches had the potential to contribute anywhere between <1% and 90% of the total annual discharge in Lake Fryxell Basin streams, and may increase with different hydrometeorological conditions. On average the potential inputs from snow patches to streamflow was between 12% and 25% of the annual discharge during the 2021–2022 season, as determined by snow area and SWE. Snow patches in the majority of the watersheds had higher nitrogen and phosphorous concentrations than stream water, and six streams contained snow with higher N:P ratios than the average N:P in the stream water. This suggests that if such patches melt early in the summer, these nutrient and water inputs could occur at the right time and stoichiometry to be crucial for early season algal mat growth.

10aAntarctica10aephemeral stream10apolar desert hydrology10arunoff generation10asnow patch10asnowmelt1 aWright, Anna, T.1 aGooseff, Michael, N.1 aBergstrom, Anna, J.1 aWelch, Kathleen, A. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.1519502098nas a2200265 4500008004100000022001400041245010400055210006900159260001200228300001200240490000800252520131200260653001601572653001501588653001801603653002501621653002101646653001301667653002201680100001601702700001401718700001401732700002901746856005701775 2023 eng d a0166-859500aHigh salt-induced PSI-supercomplex is associated with high CEF and attenuation of state transitions0 aHigh saltinduced PSIsupercomplex is associated with high CEF and c09/2023 a65 - 840 v1573 a

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.

10aacclimation10aAntarctica10aChlamydomonas10aCyclic electron flow10aPSI-supercomplex10asalinity10astate transitions1 aKalra, Isha1 aWang, Xin1 aZhang, Ru1 aMorgan-Kiss, Rachael, M. uhttps://link.springer.com/10.1007/s11120-023-01032-y01774nas a2200229 4500008004100000245011600041210006900157260001200226520104400238653001601282653001801298653001401316653001801330653002401348653001601372653001501388100001801403700001901421700002501440700002101465856005801486 2021 eng d00aHow long do population level field experiments need to be? Utilising data from the 40‐year‐old LTER network0 aHow long do population level field experiments need to be Utilis c02/20213 a

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.

10adata mining10aisothermality10along-term10amoving window10apopulation dynamics10atime series10atrajectory1 aCusser, Sarah1 aHelms, Jackson1 aBahlai, Christie, A.1 aHaddad, Nick, M. uhttps://onlinelibrary.wiley.com/doi/10.1111/ele.1371002835nas a2200217 4500008004100000245010200041210006900143260005400212490000900266520215600275653001502431653001002446653001602456653001502472653001402487653001202501653000902513100002202522700002502544856004802569 2021 eng d00aHydrologic response to foehn winds in the McMurdo Dry Valleys, Southern Victoria Land, Antarctica0 aHydrologic response to foehn winds in the McMurdo Dry Valleys So aBoulder, CObUniversity of Colorado Boulderc20200 vM.S.3 a

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.

10aAntarctica10afoehn10afoehn winds10ahydrologic10akatabatic10aMcMurdo10awind1 aBeane, Samuel, J.1 aGooseff, Michael, N. uhttps://www.proquest.com/docview/248812693703820nas a2200217 4500008004100000245015200041210006900193260004000262490000800302520300700310653003203317653003303349653001703382653002403399653002103423653002503444653003903469100002503508700002103533856004803554 2019 eng d00aHeterotrophic protists as useful models for studying microbial food webs in a model soil ecosystem and the universality of complex unicellular life0 aHeterotrophic protists as useful models for studying microbial f aProvo, UTbBrigham Young University0 vPhD3 a

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.

10aheterotrophic soil protists10akey evolutionary innovations10alife on Mars10aMcMurdo Dry Valleys10anetwork analysis10ashotgun metagenomics10auniversal complex unicellular life1 aThompson, Andrew, R.1 aAdams, Byron, J. uhttps://www.proquest.com/docview/231063197702639nas a2200301 4500008004100000245008400041210006900125260001200194520169800206653001501904653002101919653002401940653002701964653001301991100002102004700002602025700001702051700001602068700002502084700002502109700001702134700002202151700002302173700002002196700002402216700002402240856007302264 2019 eng d00aThe hydroecology of an ephemeral wetland in the McMurdo Dry Valleys, Antarctica0 ahydroecology of an ephemeral wetland in the McMurdo Dry Valleys  c11/20193 a

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.

10aAntarctica10adesert hydrology10adiatom biodiversity10ahyporheic interactions10awetlands1 aWlostowski, Adam1 aSchulte, Nicholas, O.1 aAdams, Byron1 aBall, Becky1 aEsposito, Rhea, M.M.1 aGooseff, Michael, N.1 aLyons, Berry1 aNielsen, Uffe, N.1 aVirginia, Ross, A.1 aWall, Diana, H.1 aWelch, Kathleen, A.1 aMcKnight, Diane, M. uhttps://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG00515301634nas a2200217 4500008004100000245010200041210006900143260001200212300001400224490000600238520092200244100002401166700002901190700002201219700002101241700002501262700002401287700001301311700002101324856007101345 2017 eng d00aHigh-resolution elevation mapping of the McMurdo Dry Valleys, Antarctica, and surrounding regions0 aHighresolution elevation mapping of the McMurdo Dry Valleys Anta c07/2017 a435 - 4430 v93 a

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.

1 aFountain, Andrew, G1 aFernandez-Diaz, Juan, C.1 aObryk, Maciek, K.1 aLevy, Joseph, S.1 aGooseff, Michael, N.1 aVan Horn, David, J.1 aMorin, P1 aShrestha, Ramesh uhttps://www.earth-syst-sci-data.net/9/435/2017/essd-9-435-2017.pdf02751nas a2200181 4500008004100000022001300041245010100054210006900155260001200224300001200236490000800248520216000256100002502416700002102441700002402462700001702486856006602503 2017 eng d a0169555X00aHydrologic connectivity and implications for ecosystem processes - Lessons from naked watersheds0 aHydrologic connectivity and implications for ecosystem processes c01/2017 a63 - 710 v2773 a

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.

1 aGooseff, Michael, N.1 aWlostowski, Adam1 aMcKnight, Diane, M.1 aJaros, Chris uhttp://linkinghub.elsevier.com/retrieve/pii/S0169555X1630248302884nas a2200133 4500008004100000245012700041210006900168260004800237490001000285520235800295100002102653700002502674856005102699 2017 eng d00aHydrologic connectivity in the McMurdo Dry Valleys, Antarctica: Water-mediated mass and energy fluxes in streams and soils0 aHydrologic connectivity in the McMurdo Dry Valleys Antarctica Wa aBoulder, CObUniversity of Colorado Boulder0 vPh.D.3 a

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.

1 aWlostowski, Adam1 aGooseff, Michael, N. uhttps://scholar.colorado.edu/cven_gradetds/77/00691nas a2200157 4500008004100000245015400041210006900195260001600264300001400280490000800294100002400302700001800326700001700344700002400361856014800385 2016 eng d00aHigh levels of intraspecific genetic divergences revealed for Antarctic springtails: evidence for small-scale isolation during Pleistocene glaciation0 aHigh levels of intraspecific genetic divergences revealed for An cJan-09-2016 a166 - 1780 v1191 aBennett, Kristi, R.1 aHogg, Ian, D.1 aAdams, Byron1 aHebert, Paul, D. N. uhttps://academic.oup.com/biolinnean/article-lookup/doi/10.1111/bij.12796https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fbij.1279600649nas a2200169 4500008004100000022001400041245017800055210006900233260001200302300001600314490000700330100002200337700002300359700002200382700002100404856005400425 2016 eng d a0016-803300aHigh-resolution ground-penetrating radar profiles of perennial lake ice in the McMurdo Dry Valleys, Antarctica: Horizon attributes, unconformities, and subbottom penetration0 aHighresolution groundpenetrating radar profiles of perennial lak c01/2016 aWA13 - WA200 v811 aDugan, Hilary, A.1 aArcone, Steven, A.1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttp://library.seg.org/doi/10.1190/geo2015-0159.100639nas a2200205 4500008004100000245007600041210006900117260001200186300001300198490000700211100001700218700002500235700001700260700002400277700001700301700002500318700002100343700001700364856005200381 2016 eng d00aHydrological Controls on Ecosystem Dynamics in Lake Fryxell, Antarctica0 aHydrological Controls on Ecosystem Dynamics in Lake Fryxell Anta c07/2016 ae01590380 v111 aHerbei, Radu1 aRytel, Alexander, L.1 aLyons, Berry1 aMcKnight, Diane, M.1 aJaros, Chris1 aGooseff, Michael, N.1 aPriscu, John, C.1 aHewitt, Judi uhttp://dx.plos.org/10.1371/journal.pone.015903802874nas a2200133 4500008004100000245008500041210006900126260004000195490001000235520241400245100002202659700002102681856003802702 2014 eng d00aHydrological and Biogeochemical Modeling of Taylor Valley Lakes, East Antarctica0 aHydrological and Biogeochemical Modeling of Taylor Valley Lakes  aChicago, ILbUniversity of Illinois0 vPh.D.3 a

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.

1 aObryk, Maciek, K.1 aDoran, Peter, T. uhttp://hdl.handle.net/10027/1890901695nas a2200181 4500008004100000022001400041245013500055210006900190260001200259300001400271490000700285520107500292100002101367700001601388700002401404700002001428856006501448 2014 eng d a0954-102000aHyperspectral measurements of wet, dry and saline soils from the McMurdo Dry Valleys: soil moisture properties from remote sensing0 aHyperspectral measurements of wet dry and saline soils from the  c10/2014 a565 - 5720 v263 a

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.

1 aLevy, Joseph, S.1 aNolin, Anne1 aFountain, Andrew, G1 aHead, James, W. uhttp://www.journals.cambridge.org/abstract_S095410201300097700495nas a2200121 4500008004100000245009100041210006900132260001200201300001400213490000700227100002100234856011800255 2013 eng d00aHow big are the McMurdo Dry Valleys? Estimating ice-free area using Landsat image data0 aHow big are the McMurdo Dry Valleys Estimating icefree area usin c02/2013 a119 - 1200 v251 aLevy, Joseph, S. uhttps://mcm.lternet.edu/content/how-big-are-mcmurdo-dry-valleys-estimating-ice-free-area-using-landsat-image-data00514nas a2200145 4500008004100000245006300041210005600104260001200160490000700172100002100179700002400200700002400224700001700248856010300265 2012 eng d00aHypersaline “wet patches” in Taylor Valley, Antarctica0 aHypersaline wet patches in Taylor Valley Antarctica c03/20120 v391 aLevy, Joseph, S.1 aFountain, Andrew, G1 aWelch, Kathleen, A.1 aLyons, Berry uhttps://mcm.lternet.edu/content/hypersaline-%E2%80%9Cwet-patches%E2%80%9D-taylor-valley-antarctica00636nas a2200169 4500008004100000245009700041210006900138260001200207300001600219490000700235100002300242700002000265700001900285700002400304700001500328856012300343 2011 eng d00aHigh-resolution monitoring reveals dissolved oxygen dynamics in an Antarctic cryoconite hole0 aHighresolution monitoring reveals dissolved oxygen dynamics in a c08/2011 a2868 - 28770 v251 aBagshaw, Elizabeth1 aTranter, Martyn1 aWadham, J., L.1 aFountain, Andrew, G1 aMowlem, M. uhttps://mcm.lternet.edu/content/high-resolution-monitoring-reveals-dissolved-oxygen-dynamics-antarctic-cryoconite-hole00641nas a2200181 4500008004100000245011500041210006900156260001100225300001400236490000700250100001800257700002100275700002100296700001800317700001900335700002000354856008500374 2011 eng d00aThe Holocene environmental history of Lake Hoare, Taylor Valley, Antarctica, reconstructed from sediment cores0 aHolocene environmental history of Lake Hoare Taylor Valley Antar c6/2011 a307 - 3190 v231 aWagner, Bernd1 aOrtlepp, Sabrina1 aDoran, Peter, T.1 aKenig, Fabien1 aMelles, Martin1 aBurkemper, Andy uhttp://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=827537403517nas a2200349 4500008004100000245015900041210006900200260003400269490000900303520243200312653001502744653002002759653002402779653001402803653002802817653001702845653001302862653001402875653001402889653001302903653002402916653002002940653001402960653001702974653002102991653002103012653001503033653002003048100002503068700002503093856004903118 2011 eng d00aHydrologic controls of nutrient fluxes in glacial meltwater streams at inter-annual, seasonal, and daily timescales in the McMurdo Dry Valleys, Antarctica0 aHydrologic controls of nutrient fluxes in glacial meltwater stre bPennsylvania State University0 vM.S.3 a

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'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.

10aAntarctica10abiogeochemistry10achemical weathering10adischarge10aelectrical conductivity10aglacial melt10aglaciers10ahydrology10ahyporheic10aMCM LTER10aMcMurdo Dry Valleys10anutrient fluxes10anutrients10apolar desert10asolute chemistry10astream chemistry10astreamflow10awater chemistry1 aWeaver, Mitchell, R.1 aGooseff, Michael, N. uhttps://etda.libraries.psu.edu/catalog/1156800494nas a2200145 4500008004100000245008600041210006900127260001200196300001400208490000700222100002100229700002400250700002400274856005000298 2011 eng d00aHydrologic processes influence diatom community composition in Dry Valley streams0 aHydrologic processes influence diatom community composition in D c12/2011 a1057-10730 v301 aStanish, Lee, F.1 aNemergut, Diana, R.1 aMcKnight, Diane, M. uhttp://www.jnabs.org/doi/abs/10.1899/11-008.100581nas a2200169 4500008004100000245008600041210006900127260001200196300001400208490000600222100002500228700002400253700002100277700002400298700001700322856007200339 2011 eng d00aHydrological Connectivity of the Landscape of the McMurdo Dry Valleys, Antarctica0 aHydrological Connectivity of the Landscape of the McMurdo Dry Va c09/2011 a666 - 6810 v51 aGooseff, Michael, N.1 aMcKnight, Diane, M.1 aDoran, Peter, T.1 aFountain, Andrew, G1 aLyons, Berry uhttp://onlinelibrary.wiley.com/doi/10.1111/j.1749-8198.2011.00445.x03183nas a2200229 4500008004100000245011200041210006900153260004600222300000800268490001000276520245700286653001102743653001502754653001902769653001302788653001302801653001502814653003702829100001302866700002402879856005002903 2010 eng d00aHydrologic and biogeochemical implications of flooding in two catchments underlain by continuous permafrost0 aHydrologic and biogeochemical implications of flooding in two ca aBoulder, CObUniversity of Coloradoc2010 a2060 vPh.D.3 a

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.

10acarbon10acatchments10aearth sciences10aflooding10anitrogen10apermafrost10asurface-groundwater interactions1 aKoch, J.1 aMcKnight, Diane, M. uhttps://search.proquest.com/docview/83900886500683nas a2200169 4500008004100000245011900041210006900160300001400229490000700243100001700250700002500267700002200292700002200314700003300336700001600369856012800385 2009 eng d00aHydrologic characteristics of lake- and stream-side riparian wetted margins in the McMurdo Dry Valleys, Antarctica0 aHydrologic characteristics of lake and streamside riparian wette a1255-12670 v231 aNorthcott, M1 aGooseff, Michael, N.1 aBarrett, John, E.1 aZeglin, Lydia, H.1 aTakacs-Vesbach, Cristina, D.1 aHumphrey, J uhttps://mcm.lternet.edu/content/hydrologic-characteristics-lake-and-stream-side-riparian-wetted-margins-mcmurdo-dry-valleys00521nas a2200157 4500008004100000245003800041210003600079260003600115100002400151700002500175700002500200700001600225700002500241700002800266856006900294 2008 eng d00aHigh-latitude rivers and streams.0 aHighlatitude rivers and streams aOxfordbOxford University Press1 aMcKnight, Diane, M.1 aGooseff, Michael, N.1 aVincent, Warwick, F.1 aPeterson, B1 aVincent, Warwick, F.1 aLaybourn-Parry, Johanna uhttps://mcm.lternet.edu/content/high-latitude-rivers-and-streams00775nas a2200217 4500008004100000245010100041210006900142260001500211300001200226490000700238653002100245653001200266100002100278700002700299700002400326700002200350700002400372700001700396700002200413856012200435 2008 eng d00aHydrologic response to extreme warm and cold summers in the McMurdo Dry Valleys, East Antarctica0 aHydrologic response to extreme warm and cold summers in the McMu c05/16/2008 a499-5090 v2010aClimate Response10astreams1 aDoran, Peter, T.1 aMcKay, Christopher, P.1 aFountain, Andrew, G1 aNylen, Thomas, H.1 aMcKnight, Diane, M.1 aJaros, Chris1 aBarrett, John, E. uhttps://mcm.lternet.edu/content/hydrologic-response-extreme-warm-and-cold-summers-mcmurdo-dry-valleys-east-antarctica00380nas a2200109 4500008004100000245004700041210004400088260003300132100002000165700002900185856005600214 2007 eng d00aHidden Assets: Biodiversity Below-Surface.0 aHidden Assets Biodiversity BelowSurface bUNESCO-SCOPE Policy Brief #51 aWall, Diana, H.1 aBehan-Pelletier, Valerie uhttp://www.icsu-scope.org/unesco/USPB05_SOIL_En.pdf00681nas a2200181 4500008004100000245012100041210006900162300001200231490000700243100001700250700002400267700001400291700001400305700001400319700001900333700002300352856012400375 2005 eng d00aHalogen geochemistry of the McMurdo Dry Valleys Lakes, Antarctica: clues to the origin of solutes and lake evolution0 aHalogen geochemistry of the McMurdo Dry Valleys Lakes Antarctica a305-3230 v691 aLyons, Berry1 aWelch, Kathleen, A.1 aSnyder, G1 aOlesik, J1 aGraham, E1 aMarion, G., M.1 aPoreda, Robert, J. uhttps://mcm.lternet.edu/content/halogen-geochemistry-mcmurdo-dry-valleys-lakes-antarctica-clues-origin-solutes-and-lake00489nas a2200121 4500008004100000245008700041210006900128490000700197100001700204700001300221700002400234856010900258 1999 eng d00aHistory of McMurdo Dry Valley Lakes, Antarctica, from stable chlorine isotope data0 aHistory of McMurdo Dry Valley Lakes Antarctica from stable chlor0 v271 aLyons, Berry1 aFrape, S1 aWelch, Kathleen, A. uhttps://mcm.lternet.edu/content/history-mcmurdo-dry-valley-lakes-antarctica-stable-chlorine-isotope-data00401nas a2200097 4500008004100000245007500041210006900116300001200185490000700197856009900204 1999 eng d00aHow soils structure communities in the McMurdo Dry Valleys, Antarctica0 aHow soils structure communities in the McMurdo Dry Valleys Antar a973-9830 v48 uhttps://mcm.lternet.edu/content/how-soils-structure-communities-mcmurdo-dry-valleys-antarctica00605nas a2200157 4500008004100000245008700041210006900128300001100197490000700208100002400215700002400239700002300263700002400286700002200310856011500332 1998 eng d00aHydrologic Processes Influencing Streamflow Variation in Fryxell Basin, Antarctica0 aHydrologic Processes Influencing Streamflow Variation in Fryxell a93-1080 v721 aConovitz, Peter, A.1 aMcKnight, Diane, M.1 aMacDonald, Lee, H.1 aFountain, Andrew, G1 aHouse, Harold, R. uhttps://mcm.lternet.edu/content/hydrologic-processes-influencing-streamflow-variation-fryxell-basin-antarctica