02348nas a2200217 4500008004100000245023200041210006900273260001200342300001200354490000700366520154300373653001501916653002001931653000801951653002001959653001401979653002101993100002102014700002402035856007102059 2025 eng d00aChemical signatures of microbial life in an ecological end-member: Shifting hydroclimate and sediment fluxes influence DOM biogeochemistry in Lake Fryxell, a permanently ice-covered lake in the McMurdo Dry Valleys of Antarctica0 aChemical signatures of microbial life in an ecological endmember c04/2025 a24786780 v573 a

The ice-covered lakes in the McMurdo Dry Valleys (MDV) of Antarctica provide end-member ecosystems for understanding the production of dissolved organic matter (DOM) in aquatic ecosystems in the absence of vegetation on the landscape and under resource and nutrient constraints. Given these constraints, DOM in MDV lakes is derived solely from microbial phototrophs and heterotrophic bacteria, contrasting with the dominant terrestrial sources in temperate regions. Previous research developed fluorometric approaches for characterizing DOM, including in MDV lakes. In this study we leveraged these approaches along with contemporary molecular-based techniques to elucidate changes in DOM composition across the depth profile for Lake Fryxell in the MDV. The results showed that the presence of organic molecules containing sulfur increased at depth where anoxic conditions prevailed. To evaluate the influences of climate-induced rising lake levels and multiple flood events in the MDV, we compared recent and historical samples. The results indicated a remarkable consistency in source-related fluorescence metrics over time, whereas a twofold decrease in sulfur content of the fulvic acid fraction was observed in samples from above and below the oxycline. Biogeochemical processes associated with the influx of iron oxide–rich sediments during flood events may have contributed to this change, and similar processes may stimulate biogeochemical cycling and remineralization in temperate lakes during seasonal transitions.

10aAntarctica10abiogeochemistry10aDOM10alake metabolism10alimnology10anutrient cycling1 aRue, Garrett, P.1 aMcKnight, Diane, M. uhttps://www.tandfonline.com/doi/full/10.1080/15230430.2025.247867802735nas a2200325 4500008004100000022001400041245008600055210006900141260001200210490000700222520179000229653001502019653001302034653001002047653002202057653001002079100002602089700002402115700002502139700002102164700001802185700002502203700002102228700002202249700001902271700002402290700002102314700001702335856005702352 2025 eng d a0722-406000aA comprehensive survey of soil microbial diversity across the Antarctic continent0 acomprehensive survey of soil microbial diversity across the Anta c02/20250 v483 a

Antarctic soils are unique from those found nearly anywhere else on Earth yet can still harbor a broad diversity of microorganisms able to tolerate the challenging conditions typical of the continent. For these reasons, microbiologists have been drawn to Antarctica for decades. However, our understanding of which microbes thrive in Antarctic soils and how they to do so remains limited. To help resolve these knowledge gaps, we analyzed a collection of 200 archived Antarctic soils—from Livingston Island on the Antarctic Peninsula to Cape Hallett in northern Victoria Land. We analyzed the prokaryotic and fungal communities in these soils using both cultivation-independent marker gene sequencing and cultivation-dependent approaches (microbial isolation), paired with extensive soil geochemical analyses. Our cultivation-independent analyses indicate that colder, saltier, and drier soils harbor less diverse communities of bacteria and fungi, distinct from those found in soils with less challenging conditions. We also built a culture collection from a subset of these soils that encompasses more than 50 bacterial and fungal genera, including cold-tolerant organisms, such as <i>Cryobacterium</i> and <i>Cryomyces</i>. By directly comparing the diversity of our cultured isolates against our cultivation-independent data, we show that many of the more abundant Antarctic taxa are not readily cultivated and highlight bacterial and fungal taxa that should be the focus of future cultivation efforts. Together, we hope that our collection of isolates, the comprehensive data compiled from the cultivation-independent analyses, and our geochemical analyses will serve as a community resource to accelerate the study of Antarctic soil microbes.

10aAntarctica10abacteria10afungi10amicrobial ecology10asoils1 aDragone, Nicholas, B.1 aChildress, Mary, K.1 aVanderburgh, Caihong1 aWillmore, Rachel1 aHogg, Ian, D.1 aSancho, Leopoldo, G.1 aLee, Charles, K.1 aBarrett, John, E.1 aQuandt, Alisha1 aLeMonte, Joshua, J.1 aAdams, Byron, J.1 aFierer, Noah uhttps://link.springer.com/10.1007/s00300-025-03372-y02505nas a2200325 4500008004100000022001400041245012700055210006900182260001200251300001800263490000800281520146500289653001701754653003701771653002401808653002401832100002701856700002101883700002301904700002201927700002201949700002501971700002001996700002202016700002202038700002202060700002202082700001402104856006102118 2023 eng d a2169-900300aCauses and characteristics of electrical resistivity variability in shallow (<4 m) soils in Taylor Valley, East Antarctica0 aCauses and characteristics of electrical resistivity variability c02/2023 ae2022JF0066960 v1283 a

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'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.

10aactive layer10aairborne electromagnetic surveys10aMcMurdo Dry Valleys10apermafrost dynamics1 aGutterman, William, S.1 aDoran, Peter, T.1 aVirginia, Ross, A.1 aBarrett, John, E.1 aMyers, Krista, F.1 aTulaczyk, Slawek, M.1 aFoley, Neil, T.1 aMikucki, Jill, A.1 aDugan, Hilary, A.1 aGrombacher, Denys1 aBording, Thue, S.1 aAuken, E. uhttps://onlinelibrary.wiley.com/doi/10.1029/2022JF00669601795nas a2200205 4500008004100000022001400041245009300055210006900148260001200217520099200229653002501221653001901246653002401265100002101289700002901310700002201339700001701361700001701378856019401395 2023 eng d a0260-305500aChange at 85 degrees south: Shackleton Glacier region proglacial lakes from 1960 to 20200 aChange at 85 degrees south Shackleton Glacier region proglacial  c05/20233 a

Over the last two decades, anomalous warming events have been observed in coastal Antarctic regions. While these events have been documented in the Ross Sea sector, the Antarctic interior is believed to have been buffered from warming. In this work, we present data from lakes located near Mt. Heekin and Thanksgiving Valley (~85° S) along the Shackleton Glacier, which are believed to be the southern-most Antarctic dry valley lakes. In 2018, the lakes were characterized, repeat satellite images were examined, and lake water chemistry was measured. Our analysis shows that lake areas recently increased, and the water-soluble ion chemistry indicates a flushing of salts from periglacial soils, likely from increased glacial melt as illustrated by water isotope data. Our results show that high southern latitude ice-free areas have likely been affected by warm pulses over the past 60 years and these pulses may be quasi-synchronous throughout the Transantarctic Mountains.

10aAntarctic glaciology10aclimate change10ameltwater chemistry1 aDiaz, Melisa, A.1 aGardner, Christopher, B.1 aElliot, David, H.1 aAdams, Byron1 aLyons, Berry uhttps://www.cambridge.org/core/journals/annals-of-glaciology/article/change-at-85-degrees-south-shackleton-glacier-region-proglacial-lakes-from-1960-to-2020/565D96AD7AE72BD22C49CCB772867AC402923nas a2200181 4500008004100000245015400041210006900195260004800264300000700312490000900319520225400328653002202582653001502604653002902619100002002648700002502668856004802693 2023 eng d00aCharacterizing velocity gradients in the McMurdo Dry Valleys with high-resolution optical imagery, feature-tracking methods, and in situ observations0 aCharacterizing velocity gradients in the McMurdo Dry Valleys wit aBoulder, CObUniversity of Colorado Boulder a430 vM.S.3 a

In the water-limited McMurdo Dry Valleys – the largest ice-free region of Antarctica – glaciers are the only significant source of meltwater to ephemeral streams and ecosystems. Understanding changes to the flow of these glaciers, along with characterizing how they are growing or shrinking, can elucidate how these physical controls on the region’s hydrology and ecology are responding to changing environmental conditions. Because in situ observations are difficult to collect and discrete by nature, various computer vision techniques are increasingly used to track glacier surface velocities from satellite optical and radar datasets. The most common of these techniques is image cross-correlation in the form of template matching or particle image velocimetry (PIV). Although exact methods vary, generally, cross-correlation works by co-registering temporally offset image pairs using similarity in pixel values resulting from distinctive surface features, such as crevasses, large sastrugi and snow dunes. When surface features are well-resolved with respect to an image pair’s spatial resolution, and well-preserved relative to its temporal resolution, velocity estimates can have sub-pixel precision. However, when glaciers lack meaningful surface texture – a common occurrence for the low-gradient, frozen-bed glaciers of the McMurdo Dry Valleys – cross correlation performs poorly. Using high-resolution (sub-meter per pixel) imagery can help derive texture from minor cracks and small erratics on otherwise smooth, uncrevassed surfaces, but additional adaptations are needed to improve cross correlation performance. These include additional filtering and histogram stretching steps, along with informed search area windows. Velocity estimates derived from this workflow are shown to be comparable to recorded ranges, in situ measurements, and manual feature tracking, but provide a much higher spatial and temporal resolution dataset. Alongside contemporaneous analyses of glacier mass balance, terminal thickness and surface roughness, these glacier velocity data help characterize how glaciers are dynamically evolving in response to environmental conditions in the Dry Valleys.

10across correlation10acryosphere10aglacier surface velocity1 aVanderwilt, Mia1 aGooseff, Michael, N. uhttps://www.proquest.com/docview/291637751902136nas a2200205 4500008004100000245007300041210007100114260001200185520148400197653001901681653001901700653002301719653001701742653002601759653002301785653002001808100002701828700001701855856005801872 2022 eng d00aCommunity assembly in the wake of glacial retreat: A meta‐analysis0 aCommunity assembly in the wake of glacial retreat A meta‐analysi c09/20223 a

Antarctic biodiversity faces an unknown future with a changing climate. Most terrestrial biota is restricted to limited patches of ice-free land in a sea of ice, where they are adapted to the continent's extreme cold and wind and exploit microhabitats of suitable conditions. As temperatures rise, ice-free areas are predicted to expand, more rapidly in some areas than others. There is high uncertainty as to how species' distributions, physiology, abundance, and survivorship will be affected as their habitats transform. Here we use current knowledge to propose hypotheses that ice-free area expansion (i) will increase habitat availability, though the quality of habitat will vary; (ii) will increase structural connectivity, although not necessarily increase opportunities for species establishment; (iii) combined with milder climates will increase likelihood of non-native species establishment, but may also lengthen activity windows for all species; and (iv) will benefit some species and not others, possibly resulting in increased homogeneity of biodiversity. We anticipate considerable spatial, temporal, and taxonomic variation in species responses, and a heightened need for interdisciplinary research to understand the factors associated with ecosystem resilience under future scenarios. Such research will help identify at-risk species or vulnerable localities and is crucial for informing environmental management and policymaking into the future.

10achronosequence10aclimate change10acommunity assembly10adeglaciation10aecological succession10aglacial forefields10asoil ecosystems1 aPothula, Satyendra, K.1 aAdams, Byron uhttps://onlinelibrary.wiley.com/doi/10.1111/gcb.1642702219nas a2200349 4500008004100000022001400041245012300055210006900178260001200247520113200259653000901391653001901400653001601419653001201435653000901447653001301456100002001469700002501489700001601514700002501530700002101555700001701576700002501593700002501618700002101643700002501664700002601689700002201715700002301737700001801760856009101778 2022 eng d a0006-356800aCross-site comparisons of dryland ecosystem response to climate change in the US Long-Term Ecological Research Network0 aCrosssite comparisons of dryland ecosystem response to climate c c08/20223 a

Long-term observations and experiments in diverse drylands reveal how ecosystems and services are responding to climate change. To develop generalities about climate change impacts at dryland sites, we compared broadscale patterns in climate and synthesized primary production responses among the eight terrestrial, nonforested sites of the United States Long-Term Ecological Research (US LTER) Network located in temperate (Southwest and Midwest) and polar (Arctic and Antarctic) regions. All sites experienced warming in recent decades, whereas drought varied regionally with multidecadal phases. Multiple years of wet or dry conditions had larger effects than single years on primary production. Droughts, floods, and wildfires altered resource availability and restructured plant communities, with greater impacts on primary production than warming alone. During severe regional droughts, air pollution from wildfire and dust events peaked. Studies at US LTER drylands over more than 40 years demonstrate reciprocal links and feedbacks among dryland ecosystems, climate-driven disturbance events, and climate change.

10aANPP10aclimate change10aDisturbance10adrought10aLTER10awildfire1 aHudson, Amy, R.1 aPeters, Debra, P. C.1 aBlair, J.M.1 aChilders, Daniel, L.1 aDoran, Peter, T.1 aGeil, Kerrie1 aGooseff, Michael, N.1 aGross, Katherine, L.1 aHaddad, Nick, M.1 aPastore, Melissa, A.1 aRudgers, Jennifer, A.1 aSala, Osvaldo, E.1 aSeabloom, Eric, W.1 aShaver, Gaius uhttps://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biab134/665484002454nas a2200277 4500008004100000245020000041210006900241260001200310300001400322490000800336520152000344653001501864653001401879653002501893653001801918653001701936653000801953100002401961700001601985700002102001700001902022700001802041700002302059700002902082856006502111 2022 eng d00aCyclic electron flow (CEF) and ascorbate pathway activity provide constitutive photoprotection for the photopsychrophile, Chlamydomonas sp. UWO 241 (renamed Chlamydomonas priscuii)0 aCyclic electron flow CEF and ascorbate pathway activity provide  c03/2022 a235 - 2500 v1513 a

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.

10aAntarctica10aascorbate10aCyclic electron flow10aPhotosystem I10aPsychrophile10aROS1 aStahl-Rommel, Sarah1 aKalra, Isha1 aD'Silva, Susanna1 aHahn, Mark, M.1 aPopson, Devon1 aCvetkovska, Marina1 aMorgan-Kiss, Rachael, M. uhttps://link.springer.com/article/10.1007/s11120-021-00877-502179nas a2200121 4500008004100000245012700041210006900168260005300237490000900290520167300299100002701972856005801999 2021 eng d00aCauses and characteristics of electrical resistivity variability in shallow (<4 m) soils in Taylor Valley, East Antarctica0 aCauses and characteristics of electrical resistivity variability aBaton RougebLouisiana State Universityc07/20210 vM.S.3 a

The McMurdo Dry Valleys are the largest ice-free region in Antarctica and are characterized as a polar desert environment. Soils in the region are typically very dry (<1% soil water by weight) and remain frozen for most of the year. Increases in air temperature and incoming solar radiation during the austral summer generate meltwater from glaciers, ground ice, and snow patches supplying moisture to soils and altering the physical and chemical makeup of the subsurface. Previous studies have utilized airborne electromagnetic surveys (AEM) to analyze groundwater systems in the deep subsurface but have not yet examined soil moisture in the shallow (<4 m) subsurface. Here, I used electrical resistivity data from two AEM surveys (2011 and 2018) and soil geochemical data from three transects to characterize the spatial heterogeneity of soil properties in the near-subsurface of lower Taylor Valley. Soil resistivities from 2011 and 2018 range from 33.2 Ωm to 3535 Ωm with low elevations of <100 meters above sea level (masl) typically displaying the lowest resistivities and high elevations displaying greater resistivities. Liquid brine fractions were empirically estimated from electrical resistivity values using Archie’s Law and range from 0.3% to 68.2% for soils with resistivities <200 Ωm. Additionally, soil transect data show greater percentages of fine-grained sediments (<63 µm) exist at elevations <100 masl where soil resistivities begin decreasing. Resistivity variability in the subsurface is ultimately controlled by the site history, local and regional climate, soil salinity, soil moisture, soil lithology.

1 aGutterman, William, S. uhttps://digitalcommons.lsu.edu/gradschool_theses/541102885nas a2200241 4500008004100000245006300041210006200104260004100166300001200207520209300219653003102312653003602343653002402379653001902403653002402422100001602446700001702462700002302479700001702502700002402519700002502543856007502568 2021 eng d00aChemical weathering in the McMurdo Dry Valleys, Antarctica0 aChemical weathering in the McMurdo Dry Valleys Antarctica aHoboken, NJbJohn Wiley & Sons, Inc. a205-2163 a

While chemical weathering has not always been considered an active process in the McMurdo Dry Valleys (MDV), Antarctica, long‐term geochemical and hydrological investigations have provided an overall better understanding of chemical weathering in this polar desert environment. Liquid water on the landscape is limited to stream channels as well as shallow subsurface melt features, as there is no overland flow. Stream total suspended sediment loads are low, with the sources of sediment from stream channels, aeolian input, and/or from the surfaces of glaciers. MDV soils contain high concentrations of soluble salts with little clay material, but since absent of water, these soils are a minimal location of chemical weathering. Hyporheic zones exchange water during streamflow, and these areas control the stream geochemistry over various temporal scales. Hyporheic zones promote rapid aluminosilicate weathering by moving dilute glacial meltwater into intimate contact with sediment surfaces. Rapid weathering of the aluminosilicates in the streambed and hyporheic zones is the most plausible explanation for chemostasis observed in these streams, indicating that little to no catchment processes are necessary to explain the observed chemostasis in the MDV. Shallow subsurface waters with distinct geochemical signatures have much higher dissolved Si concentrations than the stream waters and indicate that they are responsible for enhanced aluminosilicate weathering in this polar desert environment. The dissolution of CaCO3 is also a major process in the hyporheic zones as generally the streams are unsaturated with respect to calcite. Cation‐exchange reactions are also important in the evolution from Na‐Cl brines to Ca‐Cl brines within the soil column, while authigenic CaCO3 can both dissolve and precipitate depending on the condition of the system. Recently, stream channel landscapes are changing due to the melting of buried ice, creating thermokarst and water track features, resulting in a sediment and solute influx to the stream.

10aaluminosilicate weathering10aCaCO3 dissolution/precipitation10achemical weathering10ahyporheic zone10aMcMurdo Dry Valleys1 aHunt, Allen1 aEgli, Markus1 aFaybishenko, Boris1 aLyons, Berry1 aLeslie, Deborah, L.1 aGooseff, Michael, N. uhttps://agupubs.onlinelibrary.wiley.com/doi/10.1002/9781119563952.ch1104166nas a2200565 4500008004100000022001400041245007900055210006900134260001200203300001100215490000700226520245300233653001802686653002702704653001902731653001902750653001202769653001202781653001502793653008902808653002002897100002302917700002502940700002602965700002702991700002103018700002503039700001703064700002203081700002903103700002603132700002403158700002603182700002403208700002103232700001603253700002703269700002403296700002303320700002203343700002403365700002303389700001503412700002203427700002103449700002203470700002603492700002403518856005803542 2021 eng d a2150-892500aConnectivity: Insights from the U.S. Long Term Ecological Research Network0 aConnectivity Insights from the US Long Term Ecological Research  c05/2021 ae034320 v123 a

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.

10aalpine tundra10aAntarctic polar desert10aarid grassland10aarid shrubland10acoastal10aestuary10asalt marsh10aSpecial Feature: Forecasting Earth’s Ecosystems with Long-Term Ecological Research10aurban ecosystem1 aIwaniec, David, M.1 aGooseff, Michael, N.1 aSuding, Katharine, N.1 aJohnson, David, Samuel1 aReed, Daniel, C.1 aPeters, Debra, P. C.1 aAdams, Byron1 aBarrett, John, E.1 aBestelmeyer, Brandon, T.1 aCastorani, Max, C. N.1 aCook, Elizabeth, M.1 aDavidson, Melissa, J.1 aGroffman, Peter, M.1 aHanan, Niall, P.1 aHuenneke, L1 aJohnson, Pieter, T. J.1 aMcKnight, Diane, M.1 aMiller, Robert, J.1 aOkin, Gregory, S.1 aPreston, Daniel, L.1 aRassweiler, Andrew1 aRay, Chris1 aSala, Osvaldo, E.1 aSchooley, Robert1 aSeastedt, Timothy1 aSpasojevic, Marko, J.1 aVivoni, Enrique, R. uhttps://onlinelibrary.wiley.com/doi/10.1002/ecs2.343201995nas a2200205 4500008004100000245012000041210006900161260004800230490000900278520132200287653001501609653001101624653001801635653001201653653001501665653001301680100002401693700002401717856004801741 2021 eng d00aControls on microbial mat coverage and diatom species turnover in Antarctic desert streams: A transplant experiment0 aControls on microbial mat coverage and diatom species turnover i aBoulder, CObUniversity of Colorado Boulder0 vM.S.3 a

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.

10aAntarctica10adiatom10amicrobial mat10astreams10atransplant10aturnover1 aDarling, Joshua, P.1 aMcKnight, Diane, M. uhttps://www.proquest.com/docview/263459098202111nas a2200205 4500008004100000245010700041210006900148260001200217300001600229490000700245520142400252100002401676700002201700700002501722700002101747700002101768700002001789700002501809856007101834 2021 eng d00aCounting carbon: Quantifying biomass in the McMurdo Dry Valleys through orbital and field observations0 aCounting carbon Quantifying biomass in the McMurdo Dry Valleys t c10/2021 a8597 - 86230 v423 a

We use correlative field studies and high-resolution multispectral remote sensing data from the WorldView-2 instrument to estimate the abundance of photosynthetically active biomass (photoautotrophs consisting primarily of microbial mats and mosses) in Canada Stream in Taylor Valley, McMurdo Dry Valleys (MDV), Antarctica. In situ field investigations were performed to (1) acquire ground validation targets for atmospherically correcting satellite imagery, (2) derive spectra of “pure” geologic and biological endmembers, (3) estimate photoautotroph cover from remote sensing data, and (4) convert these coverage estimates to biomass using data collected in the field. Our results suggest that, on the morning of 12 December 2018, the Canada Stream system contained more than 3,800 kg of photosynthetically active carbon. Extrapolating our unmixing results to the entirety of the Fryxell basin of Taylor Valley, Antarctica, we model the presence of more than 750,000 kg of photosynthetically active carbon across the landscape and carbon fixation rates roughly equivalent to five hectares of tropical rainforest. The ability to spatially and temporally quantify the amount of photosynthetically active biomass using remote sensing data in the MDV of Antarctica is a revolutionary development that will help elucidate the ecological drivers and environmental responses in this cold desert landscape.

1 aSalvatore, Mark, R.1 aBarrett, John, E.1 aBorges, Schuyler, R.1 aPower, Sarah, N.1 aStanish, Lee, F.1 aSokol, Eric, R.1 aGooseff, Michael, N. uhttps://www.tandfonline.com/doi/full/10.1080/01431161.2021.198155904249nas a2200253 4500008004100000245009000041210006900131260001200200490000600212520350100218653002003719653002003739653001303759100001903772700002003791700002203811700002403833700002503857700001903882700001203901700001703913700002103930856004403951 2020 eng d00aChange in Pictures: Creating best practices in archiving ecological imagery for reuse0 aChange in Pictures Creating best practices in archiving ecologic c09/20200 v43 a

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.

10adata repository10aecological data10ametadata1 aGries, Corinna1 aBeaulieu, Stace1 aBrown, Renée, F.1 aGastil-Buhl, Gastil1 aElmendorf, Sarah, C.1 aHsieh, Hsun-Yi1 aKui, Li1 aMaurer, Greg1 aPorter, John, H. uhttps://biss.pensoft.net/article/59082/03380nas a2200205 4500008004100000245009700041210006900138260005400207490001000261520267200271653001002943653001402953653002902967653002202996653002603018653003203044100002603076700002403102856004803126 2020 eng d00aCharacterization of spatial and environmental influences on stream diatoms and cyanobacteria0 aCharacterization of spatial and environmental influences on stre aBoulder, CObUniversity of Colorado Boulderc20200 vPh.D.3 a

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.

10aalgae10adispersal10aenvironmental assessment10ahuman disturbance10ametacommunity ecology10aspecies distribution models1 aSchulte, Nicholas, O.1 aMcKnight, Diane, M. uhttps://www.proquest.com/docview/247621626302207nas a2200205 4500008004100000245010800041210006900149260001200218520152500230100001601755700001401771700002301785700001901808700002201827700001401849700001901863700002101882700002901903856006901932 2020 eng d00aChlamydomonas sp. UWO 241 exhibits high cyclic electron flow and rewired metabolism under high salinity0 aChlamydomonas sp UWO 241 exhibits high cyclic electron flow and  c03/20203 a

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.

1 aKalra, Isha1 aWang, Xin1 aCvetkovska, Marina1 aJeong, Jooyeon1 aMcHargue, William1 aZhang, Ru1 aHüner, Norman1 aYuan, Joshua, S.1 aMorgan-Kiss, Rachael, M. uhttp://www.plantphysiol.org/content/early/2020/04/03/pp.19.0128001864nas a2200193 4500008004100000245012800041210006900169260001200238520119500250653002401445653001801469653002501487100001801512700001801530700002101548700001401569700001801583856006901601 2020 eng d00aClimate from the McMurdo Dry Valleys, Antarctica, 1986 – 2017: Surface air temperature trends and redefined summer season0 aClimate from the McMurdo Dry Valleys Antarctica 1986 2017 Surfac c05/20203 a

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.

10aMcMurdo Dry Valleys10asummer season10aweather observations1 aObryk, M., K.1 aDoran, P., T.1 aFountain, A., G.1 aMyers, M.1 aMcKay, C., P. uhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JD03218002977nas a2200121 4500008004100000245014300041210006900184260005700253490001000310520246100320100002202781856005202803 2019 eng d00aCharacterizing photobioregenerative technology for simulataneous thermal control and air revitalization of spacecraft and surface habitats0 aCharacterizing photobioregenerative technology for simulataneous aBoulder, CObUniversity of Colorado Boulderc11/20190 vPh.D.3 a

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.

1 aMatula, Emily, E. uhttps://scholar.colorado.edu/asen_gradetds/258/02939nas a2200241 4500008004100000245010800041210006900149260001200218300001100230490000800241520220100249653000902450653001602459653003202475653001302507653001302520100001602533700001802549700001402567700001502581700002902596856007202625 2019 eng d00aCommunity response of microbial primary producers to salinity is primarily driven by nutrients in lakes0 aCommunity response of microbial primary producers to salinity is c12/2019 a1340010 v6963 a

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.

10acbbL10alake waters10amicrobial primary producers10anutrient10asalinity1 aYue, Linyan1 aKong, Weidong1 aJi, Mukan1 aLiu, Jinbo1 aMorgan-Kiss, Rachael, M. uhttps://www.sciencedirect.com/science/article/pii/S004896971933978602475nas a2200229 4500008004100000020002200041245008100063210006900144260004400213300001300257520171900270653001201989653002202001653002502023653003102048653001702079100001502096700002102111700002302132700002402155856006602179 2019 eng d a978-3-030-16775-200aComplex Structure but Simple Function in Microbial Mats from Antarctic Lakes0 aComplex Structure but Simple Function in Microbial Mats from Ant aChambSpringer International Publishing a91 - 1203 a

Microbial mats growing under the permanent ice cover of Antarctic lakes occupy an exceptionally low-disturbance regime. Constant temperature, the absence of bioturbation or physical disturbance from wind action or ice formation allow mats to accumulate, as annual growth layers, over many decades or even centuries. In so doing they often assume decimetre scale, three-dimensional morphologies such as elaborate pinnacle structures and conical mounds. Here we combine existing and new information to describe microbial structures in three Antarctic lakes—simple prostrate mats in Lake Hoare, emergent cones in Lake Untersee and elaborate pinnacles in Lake Vanda. We attempt to determine whether structures emerge simply from uncoordinated organism-environment interactions or whether they represent an example of “emergent complexity”, within which some degree of self-organisation occurs to confer a holistic functional advantage to component organisms. While some holistic advantages were evident from the structures—the increase in surface area allows greater biomass and overall productivity and nutrient exchange with overlying water—the structures could also be understood in terms of potential interactions between individuals, their orientation and their environment. The data lack strong evidence of coordinated behaviour directed towards holistic advantages to the structure, though hints of coordinated behaviour are present as non-random distributions of structural elements. The great size of microbial structures in Antarctic lakes, and their relatively simple community composition, makes them excellent models for more focused research on microbial cooperation.

10abiofilm10amicrobial ecology10amicrobial structures10aself-organising structures10astromatolite1 aHawes, Ian1 aSumner, Dawn, Y.1 aJungblut, Anne, D.1 aHurst, Christon, J. uhttps://link.springer.com/chapter/10.1007/978-3-030-16775-2_401794nas a2200181 4500008004100000245015800041210006900199260001200268300001400280490000600294520113500300100002201435700002101457700001601478700002201494700002401516856007201540 2018 eng d00aCatch and release: Hyporheic retention and mineralization of N-fixing Nostoc sustains downstream microbial mat biomass in two polar desert streams0 aCatch and release Hyporheic retention and mineralization of Nfix c07/2018 a357 - 3640 v33 a

 

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.

 

1 aKohler, Tyler, J.1 aStanish, Lee, F.1 aLiptzin, D.1 aBarrett, John, E.1 aMcKnight, Diane, M. uhttps://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lol2.1008702937nas a2200157 4500008004100000245006000041210006000101260001200161300001400173490000700187520246500194100001702659700001402676700002402690856006502714 2017 eng d00aCa isotopic geochemistry of an Antarctic aquatic system0 aCa isotopic geochemistry of an Antarctic aquatic system c01/2017 a882 - 8910 v443 a

The McMurdo Dry Valleys, Antarctica, are a polar desert ecosystem. The hydrologic system of the dry valleys is linked to climate with ephemeral streams that flow from glacial melt during the austral summer. Past climate variations have strongly influenced the closed-basin, chemically stratified lakes on the valley floor. Results of previous work point to important roles for both in-stream processes (e.g., mineral weathering, precipitation and dissolution of salts) and in-lake processes (e.g., mixing with paleo-seawater and calcite precipitation) in determining the geochemistry of these lakes. These processes have a significant influence on calcium (Ca) biogeochemistry in this aquatic ecosystem, and thus variations in Ca stable isotope compositions of the waters can aid in validating the importance of these processes. We have analyzed the Ca stable isotope compositions of streams and lakes in the McMurdo Dry Valleys. The results validate the important roles of weathering of aluminosilicate minerals and/or CaCO3 in the hyporheic zone of the streams, and mixing of lake surface water with paleo-seawater and precipitation of Ca-salts during cryo-concentration events to form the deep lake waters. The lakes in the McMurdo Dry Valleys evolved following different geochemical pathways, evidenced by their unique, nonsystematic Ca isotope signatures. 

1 aLyons, Berry1 aBullen, T1 aWelch, Kathleen, A. uhttp://onlinelibrary.wiley.com/doi/10.1002/2016GL071169/full02723nas a2200229 4500008004100000245015600041210006900197260001200266300001600278490000700294520192000301100002202221700002102243700002402264700002002288700002502308700001702333700002402350700002902374700002502403856006502428 2017 eng d00aCharacterizing hyporheic exchange processes using high-frequency electrical conductivity-discharge relationships on subhourly to interannual timescales0 aCharacterizing hyporheic exchange processes using highfrequency  c05/2017 a4124 - 41410 v533 a

Concentration-discharge (C-Q) relationships are often used to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by complexity of the critical zone, such as numerous source waters and hydrochemical nonstationarity. Consequently, researchers must often ignore important runoff pathways and geochemical sources/sinks, especially the hyporheic zone because it lacks a distinct hydrochemical signature. Such simplifications limit efforts to identify processes responsible for the transience of C-Q hysteresis over time. To address these limitations, we leverage the hydrologic simplicity and long-term, high-frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone. We utilize a novel approach to decompose loops into subhysteretic EC-Q dynamics to identify individual mechanisms governing hysteresis across a wide range of timescales. We find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability and that the effects of hyporheic mixing processes on C-Q transience differ in short and long streams. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily to interannual timescales. Last, subhysteretic analysis reveals a period of interannual freshening of glacial meltwater streams related to the effects of unsteady flow on hyporheic exchange. The subhysteretic analysis framework we introduce may be applied more broadly to constrain the processes controlling C-Q transience and advance understanding of catchment evolution. 

1 aSingley, Joel, G.1 aWlostowski, Adam1 aBergstrom, Anna, J.1 aSokol, Eric, R.1 aTorrens, Christa, L.1 aJaros, Chris1 aWilson, Colleen, E.1 aHendrickson, Patrick, J.1 aGooseff, Michael, N. uhttp://onlinelibrary.wiley.com/doi/10.1002/2016WR019739/full01371nas a2200157 4500008004100000020002200041245012600063210006900189250000600258260001300264520081000277100001701087700001801104700002401122856006701146 2017 eng d a978-3-319-57056-300aThe Climate of Snow and Ice as Boundary Condition for Microbial Life in Psychrophiles: From Biodiversity to Biotechnology0 aClimate of Snow and Ice as Boundary Condition for Microbial Life a2 bSpringer3 a

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.

1 aMargesin, R.1 aKuhn, Michael1 aFountain, Andrew, G uhttp://link.springer.com/content/pdf/10.1007/978-3-319-57057-002880nas a2200625 4500008004100000245007400041210006900115260001200184490000800196520106500204100002301269700002101292700002101313700001601334700001801350700002301368700002201391700002301413700002201436700002001458700002701478700002001505700002301525700002801548700002301576700002201599700002101621700002401642700002001666700002401686700001601710700001501726700001801741700002201759700002701781700001901808700002401827700002201851700002101873700002801894700002201922700002201944700001701966700002101983700001902004700002202023700001802045700002702063700002302090700002302113700002202136700001602158700003202174856004802206 2017 eng d00aA communal catalogue reveals Earth’s multiscale microbial diversity0 acommunal catalogue reveals Earth s multiscale microbial diversit c11/20170 v5513 a

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.

1 aThompson, Luke, R.1 aSanders, Jon, G.1 aMcDonald, Daniel1 aAmir, Amnon1 aLadau, Joshua1 aLocey, Kenneth, J.1 aPrill, Robert, J.1 aTripathi, Anupriya1 aGibbons, Sean, M.1 aAckermann, Gail1 aNavas-Molina, Jose, A.1 aJanssen, Stefan1 aKopylova, Evguenia1 aVázquez-Baeza, Yoshiki1 aGonzález, Antonio1 aMorton, James, T.1 aMirarab, Siavash1 aXu, Zhenjiang, Zech1 aJiang, Lingjing1 aHaroon, Mohamed, F.1 aKanbar, Jad1 aZhu, Qiyun1 aSong, Se, Jin1 aKosciolek, Tomasz1 aBokulich, Nicholas, A.1 aLefler, Joshua1 aBrislawn, Colin, J.1 aHumphrey, Gregory1 aOwens, Sarah, M.1 aHampton-Marcell, Jarrad1 aBerg-Lyons, Donna1 aMcKenzie, Valerie1 aFierer, Noah1 aFuhrman, Jed, A.1 aClauset, Aaron1 aStevens, Rick, L.1 aShade, Ashley1 aPollard, Katherine, S.1 aGoodwin, Kelly, D.1 aJansson, Janet, K.1 aGilbert, Jack, A.1 aKnight, Rob1 aConsortium, The, Earth Micr uhttps://www.nature.com/articles/nature2462102219nas a2200133 4500008004100000245013600041210006900177260004400246490000900290520170700299100002502006700001702031856003702048 2017 eng d00aComparing the Weathering Environment of Permian and Modern Antarctic Proglacial Lake Sediments: Mineralogical and Geochemical Study0 aComparing the Weathering Environment of Permian and Modern Antar aColumbus, OHbThe Ohio State University0 vB.S.3 a

The Antarctic continent has been in a polar to subpolar position since the Permian period. Although it has experienced milder climates over this time period as evidenced by corals in the fossil record, Antarctica did undergo extensive glaciation during the Permian. This is based on the abundance of Permian tillites (sedimentary rocks derived from glacier tills) found in the Transantarctic Mountains. In this research, I have compared Permian age proglacial lake sediments that are associated with tilites to modern proglacial lake siltstones and mudstones from Antarctica. This was done to determine the climate, especially the amount of glacier melt that occurred when these Permian sediments were deposited. The modern lake sediments are deposited in perennially ice-covered lakes by ephemeral streams that only flow 6 to 12 weeks a year. The geochemical analyses of the Permian samples and the modern sediments from Lake Hoare in the McMurdo Dry Valleys suggest that the Permian samples are more highly chemically weathered than the modern sediments. The mineralogy of Lake Hoare sediments contain more primary minerals than chemical weathering produced minerals in the Pagoda Formation rocks, thus supporting the geochemical analysis that the Pagoda Formation minerals have been more weathered. All these data suggest that the Permian lake samples were deposited in a warmer, more hydrogeologically active environment than were the modern lake sediments. These data support previously published sedimentological and paleontological data that the Pagoda samples were deposited under more temperate or warm-based proglacial conditions than what is observed in the McMurdo Dry Valleys today.

1 aBrewster, Shelby, A.1 aLyons, Berry uhttp://hdl.handle.net/1811/8076303075nas a2200157 4500008004100000024003700041245014500078210006900223260003500292300000700327490002500334520248000359100002402839700001702863856003702880 2015 eng d ahttp://hdl.handle.net/1811/6888700aChemical Weathering and Mineralogy of McMurdo Dry Valley Streams: Examining the Controls of Current and Future Ephemeral Stream Geochemistry0 aChemical Weathering and Mineralogy of McMurdo Dry Valley Streams aOhio State Universityc05/2015 a380 vUndergraduate Theses3 a

The McMurdo Dry Valleys form the largest ice-free region in Antarctica and are the coldest, driest deserts in the world. But, for approximately 6-12 weeks per year in the austral summer, continuous sunlight and near-freezing temperatures create meltwater streams that descend from the surrounding alpine glaciers. These ephemeral streams are a distinctive feature in the barren dry valley landscape and are important sources of nutrients and solutes from the weathering of streambed and hyporheic zone materials. This setting has been a US National Science Foundation funded Long-Term Ecological Research (LTER) project since 1993. A major goal of the McMurdo LTER is to understand how liquid water, the primary limiting condition for life in Antarctica, is affected by climate variability. The McMurdo Dry Valleys are extremely climate-sensitive and even seemingly small variations in temperature can have a drastic effect on hydrological activity. The McMurdo LTER program has been successful in collecting and analyzing a large amount of stream data pertaining to weathering products but, a more comprehensive analysis and interpretation of the data have yet to be undertaken. Assessment of current and future stream geochemistry is critical to predict the impact of increased water flow due to glacier melt and increasing temperature which could greatly influence the ecological function and biologic diversity in the McMurdo Dry Valleys. Surface sediments were collected at multiple locations from ephemeral streams and analyzed using a scanning electron microscope and x-ray diffraction to determine sediment mineralogy and evidence of chemical weathering. Geochemical reactions were modeled using previously collected stream water data and the USGS PHREEQC software for the speciation calculations and the assessment of the solubility controlling solid phases. Chemical weathering was apparent through visible mineral alteration and the formation of secondary weathering products. Modeling results indicate that stream geochemistry will not significantly be affected by increased water temperature in the future. These results suggest stream geochemistry and chemical weathering may instead be controlled primarily through hydrologic exchange in the hyporheic zone.

1 aScheuermann, Jordan1 aLyons, Berry uhttp://hdl.handle.net/1811/6888708594nas a2200241 4500008004100000022001300041245020300054210006900257260001200326300001400338490000800352520755800360100001907918700002407937700002007961700002407981700002308005700002308028700001708051700002708068700002708095856023008122 2015 eng d a0009254100aComparison of arsenic and molybdenum geochemistry in meromictic lakes of the McMurdo Dry Valleys, Antarctica: Implications for oxyanion-forming trace element behavior in permanently stratified lakes0 aComparison of arsenic and molybdenum geochemistry in meromictic  c05/2015 a110 - 1250 v4043 a

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.

1 aYang, Ningfang1 aWelch, Kathleen, A.1 aMohajerin, Jade1 aTelfeyan, Katherine1 aChevis, Darren, A.1 aGrimm, Deborah, A.1 aLyons, Berry1 aWhite, Christopher, D.1 aJohannesson, Karen, H. uhttp://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/plain04455nas a2200121 4500008004100000245007900041210006900120260001200189520398300201100001604184700002304200856011004223 2015 eng d00aControls on diel soil CO2 flux across moisture gradients in a polar desert0 aControls on diel soil CO2 flux across moisture gradients in a po c06/20153 a

The McMurdo Dry Valleys of Antarctica are a climate-sensitive ecosystem, where future projected climate warming will increase liquid water availability to release soil biology from physical limitations and alter ecosystem processes. For example, many studies have shown that CO2 flux, an important aspect of the carbon cycle, is controlled by temperature and moisture, which often overwhelm biotic contributions in desert ecosystems. However, these studies used either single-point measurements during peak times of biological activity or diel cycles at individual locations. Here, we present diel cycles of CO2 flux from a range of soil moisture conditions and a variety of locations and habitats to determine how diel cycles of CO2 flux vary across gradients of wet-to-dry soil and whether the water source influences the diel cycle of moist soil. Soil temperature, water content and microbial biomass significantly influenced CO2 flux. Soil temperature explained most of the variation. Soil CO2 flux moderately increased with microbial biomass, demonstrating a sometimes small but significant role of biological fluxes. Our results show that over gradients of soil moisture, both geochemical and biological fluxes contribute to soil CO2 flux, and physical factors must be considered when estimating biological CO2 flux in systems with low microbial biomass.

1 aBall, Becky1 aVirginia, Ross, A. uhttp://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9776001&fileId=S095410201500025503959nas a2200205 4500008004100000022001400041245008900055210006900144260001200213300001600225490000700241520327000248100001403518700002303532700001503555700002303570700002103593700002203614856011703636 2015 eng d a0722-406000aCyanobacterial diversity in benthic mats of the McMurdo Dry Valley lakes, Antarctica0 aCyanobacterial diversity in benthic mats of the McMurdo Dry Vall c01/2015 a1097 - 11100 v383 a
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.
1 aZhang, L.1 aJungblut, Anne, D.1 aHawes, Ian1 aAndersen, Dale, T.1 aSumner, Dawn, Y.1 aMackey, Tyler, J. uhttp://link.springer.com/10.1007/s00300-015-1669-0http://link.springer.com/content/pdf/10.1007/s00300-015-1669-002223nas a2200205 4500008004100000245012900041210006900170260001200239300001200251490000700263520146400270100001701734700002401751700002401775700002501799700002201824700003301846700001501879856012301894 2014 eng d00aCharacterization of Growing Bacterial Populations in McMurdo Dry Valley Soils through Stable Isotope Probing with 18O-water.0 aCharacterization of Growing Bacterial Populations in McMurdo Dry c08/2014 a415-4250 v893 aSoil microbial communities of the McMurdo Dry Valleys, Antarctica (MDV) contain representatives from at least fourteen bacterial phyla. However, given low rates of microbial activity, it is unclear whether this richness represents functioning rather than dormant members of the community. We used stable isotope probing (SIP) with (18) O-water to determine if microbial populations grow in MDV soils. Changes in the microbial community were characterized in soils amended with H2 (18) O and H2 (18) O-organic matter. Sequencing the 16S rRNA genes of the heavy and light fractions of the bacterial community DNA shows that DNA of microbial populations was labeled with (18) O-water, indicating these micro-organisms grew in the MDV soils. Significant differences existed in the community composition of the heavy and light fractions of the H2 (18) O and H2 (18) O-organic matter amended samples (Anosim P < 0.05 of weighted Unifrac distance). Control samples and the light DNA fraction of the H2 (18) O amended samples were dominated by representatives of the phyla Deinococcus-Thermus, Proteobacteria, Planctomyces, Gemmatimonadetes, Actinobacteria and Acidobacteria, whereas Proteobacteria were more prevalent in the heavy DNA fractions from the H2 (18) O-water and the H2 (18) O-water-organic matter treatments. Our results indicate that SIP with H2 (18) O can be used to distinguish active bacterial populations even in this low organic matter environment.1 aSchwartz, E.1 aVan Horn, David, J.1 aBuelow, Heather, N.1 aGooseff, Michael, N.1 aBarrett, John, E.1 aTakacs-Vesbach, Cristina, D.1 aOkie, J.G. uhttps://mcm.lternet.edu/content/characterization-growing-bacterial-populations-mcmurdo-dry-valley-soils-through-stable02282nas a2200181 4500008004100000245010600041210006900147260001200216300001200228490000800240520160500248100001301853700002801866700002901894700002101923700003001944856012601974 2014 eng d00aCiliate diversity, community structure and novel taxa in lakes of the McMurdo Dry Valleys, Antarctica0 aCiliate diversity community structure and novel taxa in lakes of c10/2014 a175-1900 v2273 aWe 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.1 aYuan, Xu1 aVick-Majors, Trista, J.1 aMorgan-Kiss, Rachael, M.1 aPriscu, John, C.1 aAmaral-Zettler, Linda, A. uhttps://mcm.lternet.edu/content/ciliate-diversity-community-structure-and-novel-taxa-lakes-mcmurdo-dry-valleys-antarctica07866nas a2200205 4500008004100000022001400041245011200055210006900167260001200236300001400248490000700262520715200269100001907421700001907440700001807459700002707477700001807504700002107522856011707543 2013 eng d a1380-616500aCarbon Sequestration and Release from Antarctic Lakes: Lake Vida and West Lake Bonney (McMurdo Dry Valleys)0 aCarbon Sequestration and Release from Antarctic Lakes Lake Vida  c03/2013 a135 - 1450 v193 a

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.

1 aMarion, G., M.1 aMurray, A., E.1 aWagner, Bernd1 aFritsen, Christian, H.1 aKenig, Fabien1 aDoran, Peter, T. uhttp://link.springer.com/10.1007/s10498-012-9184-1http://link.springer.com/content/pdf/10.1007/s10498-012-9184-100663nas a2200193 4500008004100000245008400041210006900125260001200194300001200206490000700218100001700225700001700242700001700259700001900276700002400295700001900319700002400338856010700362 2013 eng d00aThe carbon stable isotope biogeochemistry of streams, Taylor Valley, Antarctica0 acarbon stable isotope biogeochemistry of streams Taylor Valley A c05/2013 a26 - 360 v321 aLyons, Berry1 aLeslie, D.L.1 aHarmon, R.S.1 aNeumann, Klaus1 aWelch, Kathleen, A.1 aBisson, K., M.1 aMcKnight, Diane, M. uhttps://mcm.lternet.edu/content/carbon-stable-isotope-biogeochemistry-streams-taylor-valley-antarctica02340nas a2200241 4500008004100000245013800041210006900179260001200248300001100260490000600271520148800277100002301765700002401788700002301812700001901835700002001854700002201874700001901896700001701915700001801932700002701950856012101977 2013 eng d00aCharacterization of fulvic acid fractions of dissolved organic matter during ice-out in a hyper-eutrophic, coastal pond in Antarctica0 aCharacterization of fulvic acid fractions of dissolved organic m c12/2013 a0450150 v83 aDissolved 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–vis and fluorescence spectroscopy, and 13C NMR spectroscopy) of the three fulvic acid fractions helped to explain their behavior during isolation.1 aCawley, Kaelin, M.1 aMcKnight, Diane, M.1 aMiller, Penney, L.1 aCory, Rose, M.1 aFimmen, Ryan, L1 aGuerard, Jennifer1 aDieser, Markus1 aJaros, Chris1 aChin, Yu-Ping1 aForeman, Christine, M. uhttps://mcm.lternet.edu/content/characterization-fulvic-acid-fractions-dissolved-organic-matter-during-ice-out-hyper00663nas a2200157 4500008004100000245019300041210006900234260001200303300001200315490000700327100002600334700002700360700002300387700002400410856007100434 2013 eng d00aCharacterization of IHSS Pony Lake fulvic acid dissolved organic matter by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and fluorescence spectroscopy0 aCharacterization of IHSS Pony Lake fulvic acid dissolved organic c12/2013 a19 - 280 v651 aD’Andrilli, Juliana1 aForeman, Christine, M.1 aMarshall, Alan, G.1 aMcKnight, Diane, M. uhttp://www.sciencedirect.com/science/article/pii/S014663801300216700625nas a2200145 4500008004100000245013000041210006900171260001100240490000600251100002300257700002000280700002100300700002400321856013400345 2013 eng d00aCORRIGENDUM: Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth’s most saline lake and implications for Mars0 aCORRIGENDUM Don Juan Pond Antarctica Nearsurface CaCl2brine feed c3/20130 v31 aDickson, James, L.1 aHead, James, W.1 aLevy, Joseph, S.1 aMarchant, David, R. uhttps://mcm.lternet.edu/content/corrigendum-don-juan-pond-antarctica-near-surface-cacl2-brine-feeding-earth%E2%80%99s-most-saline04191nas a2200445 4500008004100000022001400041245005900055210005900114260001600173300001400189490000800203520302300211100002203234700001603256700001903272700001503291700001803306700002003324700001503344700001903359700001603378700001303394700001503407700001803422700001303440700002203453700001503475700001503490700002303505700001303528700001903541700001703560700001503577700001703592700001803609700002003627700001603647700002003663856006203683 2012 eng d a0036-807500aChallenges to the Future Conservation of the Antarctic0 aChallenges to the Future Conservation of the Antarctic cJan-07-2013 a158 - 1590 v3373 a

The Antarctic Treaty System, acknowledged as a successful model of cooperative regulation of one of the globe'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's resources (23). 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 (23). 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.

1 aChown, Steven, L.1 aLee, J., E.1 aHughes, K., A.1 aBarnes, J.1 aBarrett, P.J.1 aBergstrom, D.M.1 aConvey, P.1 aCowan, Don, A.1 aCrosbie, K.1 aDyer, G.1 aFrenot, Y.1 aGrant, S., M.1 aHerr, D.1 aKennicutt, M., C.1 aLamers, M.1 aMurray, A.1 aPossingham, H., P.1 aReid, K.1 aRiddle, M., J.1 aRyan, P., G.1 aSanson, L.1 aShaw, J., D.1 aSparrow, M.D.1 aSummerhayes, C.1 aTerauds, A.1 aWall, Diana, H. uhttp://www.sciencemag.org/cgi/doi/10.1126/science.122282100624nas a2200169 4500008004100000245011500041210006900156260001200225300001600237490000700253100002500260700002100285700002100306700002200327700002500349856008000374 2012 eng d00aChemical analysis of ice vein microenvironments: II. Analysis of glacial samples from Greenland and Antarctica0 aChemical analysis of ice vein microenvironments II Analysis of g c12/2012 a1109 - 11180 v581 aBarletta, Robert, E.1 aPriscu, John, C.1 aMader, Heidy, M.1 aJones, Warren, L.1 aRoe, Christopher, H. uhttp://www.montana.edu/priscu/DOCS/Publications/BarlettaEtAl2012IceVein.pdf00683nas a2200205 4500008004100000245009900041210006900140260001200209100001700221700002300238700001700261700002200278700002100300700002600321700001700347700002200364700002000386700002200406856004900428 2012 eng d00aCross-biome metagenomic analyses of soil microbial communities and their functional attributes0 aCrossbiome metagenomic analyses of soil microbial communities an c11/20121 aFierer, Noah1 aLeff, Jonathan, W.1 aAdams, Byron1 aNielsen, Uffe, N.1 aBates, Scott, T.1 aLauber, Christian, L.1 aOwens, Sarah1 aGilbert, Jack, A.1 aWall, Diana, H.1 aCaporaso, Gregory uwww.pnas.org/cgi/doi/10.1073/pnas.121521011000532nas a2200145 4500008004100000245009700041210006900138260001200207300001400219490000700233100002700240700002100267700002100288856007700309 2012 eng d00aCyanobacterial diversity across landscape units in a polar desert: Taylor Valley, Antarctica0 aCyanobacterial diversity across landscape units in a polar deser c11/2012 a268 - 2780 v821 aMichaud, Alexander, B.1 aŠabacká, Marie1 aPriscu, John, C. uhttp://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2012.01297.x/full00534nas a2200169 4500008004100000245005300041210005300094260001200147300003200159490000900191100002500200700002500225700001000250700002000260700001700280856006700297 2010 eng d00aCulturing the Antarctic Nematode Plectus murrayi0 aCulturing the Antarctic Nematode Plectus murrayi c11/2010 apdb.prot5522 - pdb.prot55220 v20101 aAdhikari, Bishwo, N.1 aTomasel, Cecilia, M.1 aLi, G1 aWall, Diana, H.1 aAdams, Byron uhttp://cshprotocols.cshlp.org/content/2010/11/pdb.emo142.short00627nas a2200157 4500008004100000245011700041210006900158300001400227490000700241100001500248700001800263700002100281700002100302700002400323856012200347 2009 eng d00aComposition and Biodegradation of a Synthetic Oil Spilled on the Perennial Ice Cover of Lake Fryxell, Antarctica0 aComposition and Biodegradation of a Synthetic Oil Spilled on the a2708-27130 v431 aJaraula, C1 aKenig, Fabien1 aDoran, Peter, T.1 aPriscu, John, C.1 aWelch, Kathleen, A. uhttps://mcm.lternet.edu/content/composition-and-biodegradation-synthetic-oil-spilled-perennial-ice-cover-lake-fryxell01755nas a2200241 4500008004100000245006900041210006500110260001200175300001200187490000800199520109500207653001101302100002201313700001501335700001601350700001501366700001601381700001401397700001301411700002101424700001101445856005701456 2009 eng d00aA Contemporary Microbially Maintained Subglacial Ferrous "Ocean"0 aContemporary Microbially Maintained Subglacial Ferrous Ocean c04/2009 a397-4000 v3243 a

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.

10aBiggie1 aMikucki, Jill, A.1 aPearson, A1 aJohnston, D1 aTurchyn, A1 aFarquhar, J1 aSchrag, D1 aAnbar, A1 aPriscu, John, C.1 aLee, P uhttp://www.sciencemag.org/content/324/5925/397.short03833nas a2200217 4500008004100000245017200041210006900213260004600282300000800328490001000336520305700346653001503403653001903418653002103437653002503458653001903483653002303502100001603525700002403541856005003565 2009 eng d00aControls on stream and hyporheic temperatures, Taylor Valley, Antarctica and large-scale climate influences on interannual flow variation in the Onyx River, Antarctica0 aControls on stream and hyporheic temperatures Taylor Valley Anta aBoulder, CObUniversity of Coloradoc2009 a3170 vPh.D.3 a

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.

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