02991nas a2200229   4500008004100000245018700041210006900228260001200297490000700309520217100316653001802487653001102505653001602516653001402532653001802546653001102564100002102575700002202596700002402618700002402642856009502666       2024                        eng d00aDrifting along: Using diatoms to track the contribution of microbial mats to particulate organic matter transport in a glacial meltwater stream in the McMurdo Dry Valleys, Antarctica0 aDrifting along Using diatoms to track the contribution of microb  c05/20240 v153 a<p>Flow pulses mobilize particulate organic matter (POM) in streams from the surrounding landscape and streambed. This POM serves as a source of energy and nutrients, as well as a means for organismal dispersal, to downstream communities. In the barren terrestrial landscape of the McMurdo Dry Valleys (MDV) of Antarctica, benthic microbial mats occupying different in-stream habitat types are the dominant POM source in the many glacier-fed streams. Many of these streams experience daily flow peaks that mobilize POM, and diatoms recovered from underlying stream sediments suggest that mat-derived diatoms in the POM are retained there through hyporheic exchange. Yet, &lsquo;how much&rsquo; and &lsquo;when&rsquo; different in-stream habitat types contribute to POM diatom assemblages is unknown. To quantify the contribution of different in-stream habitat types to POM diatom assemblages, we collected time-integrated POM samples over four diel experiments, which spanned a gradient of flow conditions over three summers. Diatoms from POM samples were identified, quantified, and compared with dominant habitat types (i.e., benthic &lsquo;orange&rsquo; mats, marginal &lsquo;black&rsquo; mats, and bare sediments). Like bulk POM, diatom cell concentrations followed a clockwise hysteresis pattern with stream discharge over the daily flow cycles, indicating supply limitation. Diatom community analyses showed that different habitat types harbor distinct diatom communities, and mixing models revealed that a substantial proportion of POM diatoms originated from bare sediments during baseflow conditions. Meanwhile, orange and black mats contribute diatoms to POM primarily during daily flow peaks when both cell concentrations and discharge are highest, making mats the most important contributors to POM diatom assemblages at high flows. These observations may help explain the presence of mat-derived diatoms in hyporheic sediments. Our results thus indicate a varying importance of different in-stream habitats to POM generation and export on daily to seasonal timescales, with implications for biogeochemical cycling and the local diatom metacommunity.</p>10acyanobacteria10adiatom10aflow regime10ahydrology10amicrobial mat10aNostoc1 aStanish, Lee, F.1 aKohler, Tyler, J.1 aDarling, Joshua, P.1 aMcKnight, Diane, M.  uhttps://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1352666/full02541nas a2200241   4500008004100000245010600041210006900147260001200216520180200228653001202030653000602042653001802048653001902066653001302085653001902098653000602117653002202123100002202145700002202167700002102189700002402210856006502234       2023                        eng d00aNitrogen fixation facilitates stream microbial mat biomass across the McMurdo Dry Valleys, Antarctica0 aNitrogen fixation facilitates stream microbial mat biomass acros  c07/20233 a<p>Nitrogen (N) fixation is a fundamental mechanism by which N enters streams. Yet, because of modern N saturation, it is difficult to study the importance of N-fixation to stream nutrient budgets. Here, we utilized relatively simple and pristine McMurdo Dry Valley streams to investigate the role of N-fixing <i>Nostoc</i> abundance, streamwater dissolved inorganic N (DIN) concentration, and distance from the source glacier in regulating the elemental and isotopic composition of three microbial mat types (black, orange, and green) at the landscape scale. We found <i>Nostoc</i>-based black mats were the most enriched in δ15N, and δ15N signatures of mats increased where <i>Nostoc</i> was abundant, but did not surpass the atmospheric standard (δ15N &asymp; 0&permil;). Furthermore, green and orange mat δ15N signatures became more depleted with increasing DIN, indicating that mats utilize glacial meltwater-sourced N when available. The distance from the source glacier explained limited variability in mat δ15N across sites, indicating the influence of individual stream characteristics on N spiraling. To further explore longitudinal N spiraling processes generating observed δ15Ν patterns, we developed a simple steady-state mathematical model. Analysis of plausible scenarios with this model confirmed that streams both have the capacity to remove allochthonous DIN over the plausible range of inputs, and that internal N sources are required to account for δ15N signatures and observed DIN concentrations at stream outlets. Collectively, these data and modeling results demonstrate that N-fixation exerts substantial influence within and across these streams, and is presumably dependent upon interconnected organic matter reserves, mineralization rates, and geomorphology.</p>10abiofilm10aC10acyanobacteria10ahyporheic zone10aMCM LTER10amineralization10aN10aP biogeochemistry1 aKohler, Tyler, J.1 aSingley, Joel, G.1 aWlostowski, Adam1 aMcKnight, Diane, M.  uhttps://link.springer.com/article/10.1007/s10533-023-01069-001860nas a2200205   4500008004100000022001400041245015300055210006900208260001200277520112000289100002201409700002001431700002001451700002501471700001701496700002401513700002501537700002401562856006801586       2021                        eng d  a2378-224200aFrom the Heroic Age to today: What diatoms from Shackleton's <i>Nimrod</I> expedition can tell us about the ecological trajectory of Antarctic ponds0 aFrom the Heroic Age to today What diatoms from Shackletons iNimr  c07/20213 a<p>Biological invasion and environmental change pose major threats to ecosystems. While long-term ecological change is commonly evaluated through sediment cores in lakes, it is generally not feasible for smaller ponds, and spatial resolution is limited. Here, we analyze pond diatom communities collected during Shackleton&#39;s <em>Nimrod</em> expedition at Cape Royds, Antarctica, to compare with the same waterbodies a century later. We find historical samples to be almost identical to modern counterparts, and provide no evidence of exotic introductions despite increasing human activity. However, a shift occurred in the pond nearest Shackleton&#39;s hut, Pony Lake, which was dominated by <em>Luticola muticopsis</em> a century ago, and was replaced by <em>Craspedostauros laevissimus</em>. Both are endemic species previously and currently present at Cape Royds, and we hypothesize that a shift in conductivity accompanying changing precipitation patterns may be responsible. Collectively, these results provide important data for assessing human and climate impacts among Antarctic lacustrine habitats.</p>1 aKohler, Tyler, J.1 aHowkins, Adrian1 aSokol, Eric, R.1 aKopalová, Kateřina1 aCox, Aneliya1 aDarling, Joshua, P.1 aGooseff, Michael, N.1 aMcKnight, Diane, M.  uhttps://aslopubs.onlinelibrary.wiley.com/doi/10.1002/lol2.1020003261nas a2200241   4500008004100000245013300041210006900174260001200243490000600255520247400261653001502735653002202750653001402772653001102786653001902797100002002816700002202836700002202858700002402880700002402904700002102928856007002949       2020                        eng d00aEvaluating alternative metacommunity hypotheses for diatoms in the McMurdo Dry Valleys using simulations and remote sensing data0 aEvaluating alternative metacommunity hypotheses for diatoms in t  c09/20200 v83 a<p>Diatoms are diverse and widespread freshwater Eukaryotes that make excellent microbial subjects for addressing questions in metacommunity ecology. In the McMurdo Dry Valleys of Antarctica, the simple trophic structure of glacier-fed streams provides an ideal outdoor laboratory where well-described diatom assemblages are found within two cyanobacterial mat types, which occupy different habitats and vary in coverage within and among streams. Specifically, black mats of <em>Nostoc</em> spp. occur in marginal wetted habitats, and orange mats (<em>Oscillatoria</em> spp. and <em>Phormidium</em> spp.) occur in areas of consistent stream flow. Despite their importance as bioindicators for changing environmental conditions, the role of dispersal in structuring dry valley diatom metacommunities remains unclear. Here, we use MCSim, a spatially explicit metacommunity simulation package for R, to test alternative hypotheses about the roles of dispersal and species sorting in maintaining the biodiversity of diatom assemblages residing in black and orange mats. The spatial distribution and patchiness of cyanobacterial mat habitats was characterized by remote imagery of the Lake Fryxell sub-catchment in Taylor Valley. The available species pool for diatom metacommunity simulation scenarios was informed by the Antarctic Freshwater Diatoms Database, maintained by the McMurdo Dry Valleys Long Term Ecological Research program. We used simulation outcomes to test the plausibility of alternative community assembly hypotheses to explain empirically observed patterns of freshwater diatom biodiversity in the long-term record. The most plausible simulation scenarios suggest species sorting by environmental filters, alone, was not sufficient to maintain biodiversity in the Fryxell Basin diatom metacommunity. The most plausible scenarios included either (1) neutral models with different immigration rates for diatoms in orange and black mats or (2) species sorting by a relatively weak environmental filter, such that dispersal dynamics also influenced diatom community assembly, but there was not such a strong disparity&nbsp;in immigration rates between mat types. The results point to the importance of dispersal for understanding current and future biodiversity patterns for diatoms in this ecosystem, and more generally, provide further evidence that metacommunity theory is a useful framework for testing hypotheses about microbial community assembly.</p>10aAntarctica10aBacillariophyceae10adispersal10aNostoc10astream ecology1 aSokol, Eric, R.1 aBarrett, John, E.1 aKohler, Tyler, J.1 aMcKnight, Diane, M.1 aSalvatore, Mark, R.1 aStanish, Lee, F.  uhttps://www.frontiersin.org/article/10.3389/fevo.2020.521668/full02300nas a2200289   4500008004100000245009400041210006900135260001200204490000800216520140200224653002001626653001501646653002001661653002401681653001401705653001901719100001901738700002501757700002401782700002601806700002201832700001901854700002501873700002401898700002401922856006401946       2019                        eng d00a<i>Sabbea gen. nov.</i>, a new diatom genus (Bacillariophyta) from continental Antarctica0 aiSabbea gen novi a new diatom genus Bacillariophyta from contine  c09/20190 v4183 a<p>The non-marine diatom flora of the Antarctic Continent includes several endemic taxa recorded over the past 100 years. One of these taxa, <em>Navicula adminensis</em> D.Roberts &amp; McMinn, was described from the Vestfold Hills, East Antarctica. Detailed light and scanning electron microscopy observations have shown that based on its morphological features, the species does not belong to the genus <em>Navicula sensu stricto</em>. To determine the most closely related genera to <em>N. adminensis</em>, the morpho- logical features of <em>Adlafia</em>, <em>Kobayasiella</em>, <em>Envekadea</em>, <em>Stenoneis</em>, <em>Berkeleya</em>, <em>Climaconeis</em>, and <em>Parlibellus</em> were compared with those of <em>N. adminensis</em>. Although each of these genera shows one or more similar features, none of them accommodates the salient morphological characteristics of N. adminensis. Therefore, a new genus, <em>Sabbea gen. nov.</em>, is herein described, and <em>Navicula adminensis</em> is formally transferred to the new genus as <em>Sabbea adminensis comb. nov.</em> The genus <em>Sabbea</em> is characterized by uniseriate striae composed of small, rounded areolae occluded externally by individual hymenes, a rather simple raphe structure with straight, short proximal ends and short terminal raphe fissures, open girdle bands with double perforation and a very shallow mantle.</p>10aBacillariophyta10aCape Royds10aEast Antarctica10aMcMurdo Dry Valleys10anew genus10aVestfold Hills1 aBishop, Jordan1 aKopalová, Kateřina1 aDarling, Joshua, P.1 aSchulte, Nicholas, O.1 aKohler, Tyler, J.1 aMcMinn, Andrew1 aSpaulding, Sarah, A.1 aMcKnight, Diane, M.1 aVan de Vijver, Bart  uhttps://www.mapress.com/j/pt/article/view/phytotaxa.418.1.201794nas a2200181   4500008004100000245015800041210006900199260001200268300001400280490000600294520113500300100002201435700002101457700001601478700002201494700002401516856007201540       2018                        eng d00aCatch and release: Hyporheic retention and mineralization of N-fixing <i>Nostoc</i> 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<p>&nbsp;</p><div title="Page 1"><div><div><p>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&nbsp;d15N signatures of Oscillatorean, Chlorophyte, and N-fixing&nbsp;Nostoc&nbsp;mats over the lengths of two streams, and transported particulate organic matter (POM) in one. POM was isotopically most similar to&nbsp;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&nbsp;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.</p></div></div></div><p>&nbsp;</p>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/lol2.1008702308nas a2200217   4500008004100000022001400041245010100055210006900156260001200225300001400237490000700251520161900258100002501877700001601902700002001918700002201938700002401960700001801984700002402002856006402026       2017                        eng d  a0722-406000aFreshwater diatom biogeography and the genus Luticola: an extreme case of endemism in Antarctica0 aFreshwater diatom biogeography and the genus Luticola an extreme  c03/2017  a1185-11960 v403 a<p>Historical views have characterized Antarctica as a frozen desert with low diversity, although recent studies suggest that this may not be true for microscopic organisms. For microbes, assessing endemism in the Antarctic region has been particularly important, especially against a backdrop of debate regarding their presumed cosmopolitan nature. To contribute to this conversation, we highlight the observed endemism of the freshwater diatom genus Luti- cola in Antarctica by synthesizing the results of a modern high-resolution taxonomy from the Continental, Maritime, and sub-Antarctic regions. We report that Luticola has one of the highest endemic rates of any diatom genus in Antarctica, in terms of total number of species (taxon endemism) and percentage of the entire genus (phylogenetic endemism). Of the over 200 species of Luticola globally, nearly 20% (43) occur in the Antarctic, with 42 of these being endemic. Within regions, Maritime Antarctica has the largest number of Luticola species and endemics (28 and 23, respectively), followed by Continental Antarctica (14, 9) and sub-Antarctic islands (8, 6). Thus, 38 of the 42 endemics are found in a single region only. While the timing of Luticola diversi cation has not been established, fossil evidence suggests recent invasions and/or diversi cation over a relatively short geologic timescale. Understanding the origin and evolution of endemic diatom species in Antarctica will help us better understand microbial biogeography, as well as assess and interpret impacts of large-scale environmental change taking place at southern latitudes.</p>1 aKociolek, J. Patrick1 aKopalova, K1 aHamsher, S., E.1 aKohler, Tyler, J.1 aVan de Vijver, Bart1 aConvey, Peter1 aMcKnight, Diane, M.  uhttps://link.springer.com/article/10.1007/s00300-017-2090-700939nas a2200217   4500008004100000022001400041245011900055210006900174260001200243100001600255700002000271700002200291700002100313700002500334700002000359700002400379700001700403700002200420700002400442856025500466       2016                        eng d  a0722-406000aEvidence for dispersal and habitat controls on pond diatom communities from the McMurdo Sound Region of Antarctica0 aEvidence for dispersal and habitat controls on pond diatom commu  c02/20161 aSakaeva, A.1 aSokol, Eric, R.1 aKohler, Tyler, J.1 aStanish, Lee, F.1 aSpaulding, Sarah, A.1 aHowkins, Adrian1 aWelch, Kathleen, A.1 aLyons, Berry1 aBarrett, John, E.1 aMcKnight, Diane, M.  uhttp://link.springer.com/10.1007/s00300-016-1901-6http://link.springer.com/content/pdf/10.1007/s00300-016-1901-6http://link.springer.com/content/pdf/10.1007/s00300-016-1901-6.pdfhttp://link.springer.com/article/10.1007/s00300-016-1901-6/fulltext.html02591nas a2200193   4500008004100000245013100041210006900172260001200241300001100253490000700264520191200271100002202183700002402205700002402229700003302253700002402286700001702310856007002327       2016                        eng d00aNutrient treatments alter microbial mat colonization in two glacial meltwater streams from the McMurdo Dry Valleys, Antarctica0 aNutrient treatments alter microbial mat colonization in two glac  c03/2016  afiw0490 v923 a<p><span style="color: rgb(3, 3, 3); font-family: Helvetica, Arial, sans-serif; font-size: 14px; line-height: 21px; background-color: rgb(255, 255, 254);">Microbial mats are abundant in many alpine and polar aquatic ecosystems. With warmer temperatures, new hydrologic pathways are developing in these regions and increasing dissolved nutrient fluxes. In the McMurdo Dry Valleys, thermokarsting may release both nutrients and sediment, and has the potential to influence mats in glacial meltwater streams. To test the role of nutrient inputs on community structure, we created nutrient diffusing substrata (NDS) with agar enriched in N, P and N + P, with controls, and deployed them into two Dry Valley streams. We found N amendments (N and N + P) to have greater chlorophyll-a concentrations, total algal biovolume, more fine filamentous cyanobacteria and a higher proportion of live diatoms than other treatments. Furthermore, N treatments were substantially elevated in Bacteroidetes and the small diatom,&nbsp;</span><em style="outline: 0px; font-variant-numeric: inherit; font-stretch: inherit; font-size: 14px; line-height: 21px; font-family: Helvetica, Arial, sans-serif; color: rgb(3, 3, 3); background-color: rgb(255, 255, 254);">Fistulifera pelliculosa</em><span style="color: rgb(3, 3, 3); font-family: Helvetica, Arial, sans-serif; font-size: 14px; line-height: 21px; background-color: rgb(255, 255, 254);">. On the other hand, species richness was almost double in P and N + P treatments over others, and coccoid green algae and Proteobacteria were more abundant in both streams. Collectively, these data suggest that nutrients have the potential to stimulate growth and alter community structure in glacial meltwater stream microbial mats, and the recent erosion of permafrost and accelerated glacial melt will likely impact resident biota in polar lotic systems here and elsewhere.</span></p>1 aKohler, Tyler, J.1 aVan Horn, David, J.1 aDarling, Joshua, P.1 aTakacs-Vesbach, Cristina, D.1 aMcKnight, Diane, M.1 aWagner, Dirk  uhttp://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw04902226nas a2200229   4500008004100000245011100041210006900152260001200221300001100233490000700244520146700251100002401718700002201742700002301764700001901787700002201806700002401828700002101852700002001873700003301893856007001926       2016                        eng d00aPatterns of bacterial biodiversity in the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica0 aPatterns of bacterial biodiversity in the glacial meltwater stre  c08/2016  afiw1480 v923 a<p>Microbial consortia dominate glacial meltwater streams from polar regions, including the McMurdo Dry Valleys (MDV), where they thrive under physiologically stressful conditions. In this study, we examined microbial mat types and sediments found in 12 hydrologically diverse streams to describe the community diversity and composition within and across sites. Sequencing of the 16S rRNA gene from 129 samples revealed &sim;24 000 operational taxonomic units (&lt;97% DNA similarity), making streams the most biodiverse habitat in the MDV. Principal coordinate analyses revealed significant but weak clustering by mat type across all streams (ANOSIM R-statistic = 0.28) but stronger clustering within streams (ANOSIM R-statistic from 0.28 to 0.94). Significant relationships (P &lt; 0.05) were found between bacterial diversity and mat ash-free dry mass, suggesting that diversity is related to the hydrologic regimes of the various streams, which are predictive of mat biomass. However, correlations between stream chemistry and community members were weak, possibly reflecting the importance of internal processes and hydrologic conditions. Collectively, these results suggest that localized conditions dictate bacterial community composition of the same mat types and sediments from different streams, and while MDV streams are hotspots of biodiversity in an otherwise depauperate landscape, controls on community structure are complex and site specific.</p>1 aVan Horn, David, J.1 aWolf, Caitlin, R.1 aColman, Daniel, R.1 aJiang, Xiaoben1 aKohler, Tyler, J.1 aMcKnight, Diane, M.1 aStanish, Lee, F.1 aYazzie, Terrill1 aTakacs-Vesbach, Cristina, D.  uhttp://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw14800595nas a2200157   4500008004100000245013400041210006900175260001200244300000800256490000800264100002200272700002500294700002400319700002500343856006900368       2015                        eng d00aThe genus Luticola D.G.Mann (Bacillariophyta) from the McMurdo Sound Region, Antarctica, with the description of four new species0 agenus Luticola DGMann Bacillariophyta from the McMurdo Sound Reg  c10/2015  a1030 v2081 aKohler, Tyler, J.1 aKopalová, Kateřina1 aVan de Vijver, Bart1 aKociolek, J. Patrick  uhttps://www.biotaxa.org/Phytotaxa/article/view/phytotaxa.208.2.102538nas a2200205   4500008004100000245010400041210006900145260001200214300001200226490000700238520189000245100002202135700002102157700001902178700001302197700001602210700001702226700002402243856006502267       2015                        eng d00a Long-Term Hydrologic Control of Microbial Mat Abundance in McMurdo Dry Valley Streams, Antarctica.0 aLongTerm Hydrologic Control of Microbial Mat Abundance in McMurd  c03/2015  a310-3270 v183 a<p><span style="color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: 13px; line-height: 20.8px;">Given alterations in global hydrologic regime, we examine the role of hydrology in regulating stream microbial mat abundance in the McMurdo Dry Valleys, Antarctica. Here, perennial mats persist as a desiccated crust until revived by summer streamflow, which varies inter-annually, and has increased since the 1990s. We predicted high flows to scour mats, and intra-seasonal drying to slow growth. Responses were hypothesized to differ based on mat location within streams, along with geomorphology, which may promote (high coverage) or discourage (low coverage) accrual. We compared hydrologic trends with the biomass of green and orange mats, which grow in the channel, and black mats growing at stream margins for 16 diverse stream transects over two decades. We found mat biomass collectively decreased during first decade coinciding with low flows, and increased following elevated discharges. Green mat biomass showed the greatest correlations with hydrology and was stimulated by discharge in high coverage transects, but negatively correlated in low coverage due to habitat scour. In contrast, orange mat biomass was negatively related to flow in high coverage transects, but positively correlated in low coverage because of side-channel expansion. Black mats were weakly correlated with all hydrologic variables regardless of coverage. Lastly, model selection indicated the best combination of predictive hydrologic variables for biomass differed between mat types, but also high and low coverage transects. These results demonstrate the importance of geomorphology and species composition to modeling primary production, and will be useful in predicting ecological responses of benthic habitats to altered hydrologic regimes.</span></p>1 aKohler, Tyler, J.1 aStanish, Lee, F.1 aCrisp, Stenven1 aKoch, J.1 aLiptzin, D.1 aBaeseman, J.1 aMcKnight, Diane, M.  uhttp://link.springer.com/article/10.1007%2Fs10021-014-9829-603401nas a2200241   4500008004100000245013400041210006900175260004000244300000800284490001000292520259800302653001002900653001502910653002402925653001902949653001602968653001902984653002403003653001903027100002203046700002403068856006703092       2015                        eng d00aPhysical and chemical controls on the abundance and composition of stream microbial mats from the McMurdo Dry Valleys, Antarctica0 aPhysical and chemical controls on the abundance and composition   aBoulder, CObUniversity of Colorado  a2720 vPh.D.3 a<p>&nbsp;</p><div title="Page 4"><div><div><p>The McMurdo Dry Valleys of Antarctica are a cold, dry desert, yet perennial microbial mats are abundant in the ephemeral glacial meltwater streams that flow during austral summers. Three types of mats are present (orange, black, and green), and are primarily comprised of filamentous cyanobacteria,&nbsp;Nostoc, and chlorophytes, respectively. Mat types furthermore occupy distinct habitats within streams, utilizing the benthos, hyporheic zone, and water column, which expose them to different environmental conditions. Due to a lack of lateral inflows, allochthonous organic inputs, and negligible grazing activity, these streams are ideal for the controlled ecological study of microbial mats. Here, I investigated how mats will respond to physical disturbance, alterations in the hydrologic regime, and nutrient liberation from permafrost melt in the future. Specifically, I: 1) quantified and characterized the regrowth of mat biomass, community structure, and elemental stoichiometry after a scouring disturbance, 2) investigated how geomorphology and taxonomic identity influences the response of mat biomass to hydrologic regime in transects monitored over two decades, and 3) evaluated relationships between water chemistry and the elemental and isotopic composition of mat types over longitudinal and valley-wide gradients in Taylor Valley. I found that mats recovered ~20-50% of their biomass over the course of an austral summer following scour. Algal communities were significantly different in composition between disturbed and control treatments, but all samples naturally varied in species and elemental stoichiometry over the study period. When the long- term record of mat biomass was compared with hydrologic variables, stream channel mats (orange and green) had the greatest correlations, while marginal mats (black) showed weaker relationships with flow regime. Relationships also differed as a function of stream geomorphology, indicating the importance of substrata and gradient in conjunction with discharge. Lastly, mats showed unique elemental and isotopic compositions. Green and orange mats within the stream channel most reflected water column nutrient concentrations, while black mats showed significant nitrogen fixation. These results highlight the importance of taxonomic identity and habitat to modeling primary production here and elsewhere, and provide insight to how stream microbial mat communities are formed, maintained, and ultimately persist in an isolated polar desert.</p></div></div></div><p>&nbsp;</p>10aalgae10aAntarctica10abiological sciences10aclimate change10aDisturbance10aearth sciences10aMcMurdo Dry Valleys10amicrobial mats1 aKohler, Tyler, J.1 aMcKnight, Diane, M.  uhttps://search.proquest.com/docview/1690497718?accountid=1450304273nas a2200193   4500008004100000022001400041245007400055210006900129260001600198300001400214490000700228520366500235100002203900700002103922700002503943700002203968700002403990856006504014       2015                        eng d  a0954-102000aRecovery of Antarctic stream epilithon from simulated scouring events0 aRecovery of Antarctic stream epilithon from simulated scouring e  cJan-08-2015  a341 - 3540 v273 a<p><span style="color: rgb(98, 98, 98); font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; font-size: 12px; line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">Microbial mats are common in polar streams and often dominate benthic biomass. Climate change may be enhancing the variability of stream flows in the Antarctic, but so far studies investigating mat responses to disturbance have been limited in this region. Mat regrowth was evaluated following disturbance by experimentally scouring rocks from an ephemeral McMurdo Dry Valley stream over two summers (2001&ndash;02 and 2012&ndash;13). Mats were sampled at the beginning and resampled at the end of the flow season. In 2012&ndash;13, mats were additionally resampled mid-season along with previously undisturbed controls. In 2001&ndash;02 rocks regained 47% of chlorophyll&nbsp;</span><em style="outline: 0px; font-size: 12px; font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; color: rgb(98, 98, 98); line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">a</em><span style="color: rgb(98, 98, 98); font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; font-size: 12px; line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">and 40% of ash-free dry mass by the end of the summer, while in 2012&ndash;13 rocks regrew 18% and 27%, respectively. Mat stoichiometry differed between summers, and reflected differences in biomass and discharge.&nbsp;</span><em style="outline: 0px; font-size: 12px; font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; color: rgb(98, 98, 98); line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">Oscillatoria</em><span style="color: rgb(98, 98, 98); font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; font-size: 12px; line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">&nbsp;spp. were greatest on scoured rocks and&nbsp;</span><em style="outline: 0px; font-size: 12px; font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; color: rgb(98, 98, 98); line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">Phormidium</em><span style="color: rgb(98, 98, 98); font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; font-size: 12px; line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">&nbsp;spp. on undisturbed rocks. Small diatoms&nbsp;</span><em style="outline: 0px; font-size: 12px; font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; color: rgb(98, 98, 98); line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">Humidophila</em><span style="color: rgb(98, 98, 98); font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; font-size: 12px; line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">&nbsp;and</span><em style="outline: 0px; font-size: 12px; font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; color: rgb(98, 98, 98); line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">Fistulifera</em><span style="color: rgb(98, 98, 98); font-family: 'Arial Unicode MS', Arial, Helvetica, sans-serif; font-size: 12px; line-height: 21.6000003814697px; background-color: rgb(241, 241, 241);">&nbsp;spp. increased throughout the summer in all mats, with the latter more abundant in scoured communities. Collectively, these data suggest that mats are variable intra-annually, responsive to hydrology and require multiple summers to regrow initial biomass once lost. These results will aid the interpretation of long-term data, as well as inform Antarctic Specially Managed Area protocols.</span></p>1 aKohler, Tyler, J.1 aChatfield, Ethan1 aGooseff, Michael, N.1 aBarrett, John, E.1 aMcKnight, Diane, M.  uhttp://www.journals.cambridge.org/abstract_S095410201500002400743nas a2200205   4500008004100000245013500041210006900176260001200245300001600257490000700273100002100280700002200301700002500323700002400348700002200372700002000394700002400414700002400438856007500462       2012                        eng d00aExtreme streams: flow intermittency as a control on diatom communities in meltwater streams in the McMurdo Dry Valleys, Antarctica0 aExtreme streams flow intermittency as a control on diatom commun  c08/2012  a1405 - 14190 v691 aStanish, Lee, F.1 aKohler, Tyler, J.1 aEsposito, Rhea, M.M.1 aSimmons, Breana, L.1 aNielsen, Uffe, N.1 aWall, Diana, H.1 aNemergut, Diana, R.1 aMcKnight, Diane, M.  uhttp://www.nrcresearchpress.com/doi/abs/10.1139/f2012-022#.UH2NlWcnq9g