@article {4373, title = {The hydroecology of an ephemeral wetland in the McMurdo Dry Valleys, Antarctica}, journal = {Journal of Geophysical Research: Biogeosciences}, year = {2019}, month = {11/2019}, abstract = {

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

}, keywords = {LTER-MCM, Antarctica, desert hydrology, diatom biodiversity, hyporheic interactions, wetlands}, doi = {10.1029/2019JG005153}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JG005153}, author = {Wlostowski, Adam and Schulte, Nicholas O. and Byron Adams and Ball, Becky and Rhea M.M. Esposito and Michael N. Gooseff and W. Berry Lyons and Uffe N. Nielsen and Ross A. Virginia and Diana H. Wall and Kathleen A. Welch and Diane M. McKnight} } @article {4018, title = {Thermal autecology describes the occurrence patterns of four benthic diatoms in McMurdo Dry Valley streams}, journal = {Polar Biology}, volume = {40}, year = {2017}, month = {06/2017}, pages = {2381-2396}, abstract = {

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

grew faster than the other taxa studied and thrived at 10 \°C. Hantzschia amphioxys grew only at the two lower temperatures. These results aligned with the observed relationships between each taxon\’s relative abundance and stream temperatures in the long-term record maintained by the MDV Long-Term Ecological Research program. Overall, our observations suggest that differences in thermal optima may be one factor contributing to and maintaining the diversity of benthic diatom flora in the MDV.
}, keywords = {LTER-MCM}, doi = {10.1007/s00300-017-2151-y}, url = {https://link.springer.com/article/10.1007/s00300-017-2151-y}, author = {Darling, Joshua P. and Garland, Deena D. and Lee F. Stanish and Rhea M.M. Esposito and Eric R. Sokol and Diane M. McKnight} } @article {1116, title = {Extreme streams: flow intermittency as a control on diatom communities in meltwater streams in the McMurdo Dry Valleys, Antarctica}, journal = {Canadian Journal of Fisheries and Aquatic Sciences}, volume = {69}, year = {2012}, month = {08/2012}, pages = {1405 - 1419}, keywords = {LTER-MCM}, doi = {10.1139/f2012-022}, url = {http://www.nrcresearchpress.com/doi/abs/10.1139/f2012-022$\#$.UH2NlWcnq9g}, author = {Lee F. Stanish and Tyler J. Kohler and Rhea M.M. Esposito and Breana L. Simmons and Uffe N. Nielsen and Diana H. Wall and Diana R. Nemergut and Diane M. McKnight} } @article {1216, title = {Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica}, journal = {Botany-Botanique}, volume = {12}, year = {2008}, pages = {1378-1392}, keywords = {LTER-MCM}, doi = {LTER}, author = {Rhea M.M. Esposito and Sarah A. Spaulding and Diane M. McKnight and De Vijver, B and Kopalova, K and Lubinski, D and Brenda L. Hall and Whittaker, T} } @article {1256, title = {Antarctic Climate Cooling and Response of Diatoms in Glacial Meltwater Streams}, journal = {Geophysical Research Letters}, volume = {33}, year = {2006}, month = {04/2006}, pages = {L07406}, type = {Journal}, abstract = {

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

}, keywords = {LTER-MCM, Biggie}, doi = {10.1029/2006GL025903}, author = {Rhea M.M. Esposito and Horn, S and Diane M. McKnight and Cox, M and Grant, M and Sarah A. Spaulding and Peter T. Doran and Cozzetto, K} }