@article {4515, title = {Evaluating alternative metacommunity hypotheses for diatoms in the McMurdo Dry Valleys using simulations and remote sensing data}, journal = {Frontiers in Ecology and Evolution}, volume = {8}, year = {2020}, month = {09/2020}, abstract = {

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 Nostoc spp. occur in marginal wetted habitats, and orange mats (Oscillatoria spp. and Phormidium 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\ 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.

}, keywords = {LTER-MCM, Antarctica, Bacillariophyceae, dispersal, Nostoc, stream ecology}, doi = {10.3389/fevo.2020.521668}, url = {https://www.frontiersin.org/article/10.3389/fevo.2020.521668/full}, author = {Eric R. Sokol and John E. Barrett and Tyler J. Kohler and Diane M. McKnight and Salvatore, Mark R. and Lee F. Stanish} } @article {3714, title = {Evidence for dispersal and habitat controls on pond diatom communities from the McMurdo Sound Region of Antarctica}, journal = {Polar Biology}, year = {2016}, month = {02/2016}, keywords = {LTER-MCM}, issn = {0722-4060}, doi = {10.1007/s00300-016-1901-6}, url = {http://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.html}, author = {Sakaeva, A. and Eric R. Sokol and Tyler J. Kohler and Lee F. Stanish and Sarah A. Spaulding and Howkins, Adrian and Kathleen A. Welch and W. Berry Lyons and John E. Barrett and Diane M. McKnight} } @mastersthesis {4094, title = {Ecology and biogeography of freshwater diatoms in ponds of McMurdo Dry Valleys and parts of the Ross Island}, volume = {M.S.}, year = {2014}, school = {University of Colorado}, type = {masters}, address = {Boulder, CO}, abstract = {

The McMurdo Dry Valleys (MDVs) and the exposed coastal areas of the nearby Ross Island in Antarctica represent some of the coldest, driest places in the world. However, during the austral summer warmer temperatures and constant sunlight allow microbial life to flourish nearly anywhere there is water. Diatoms are single-celled algae encapsulated in a silica shell and diatom communities constitute an important component of the microbial mats that grow in the streams, lakes and ponds in these regions. As part of the Long Term Ecological Research station in the McMurdo Dry Valleys diatom communities have been studied extensively in the streams over the last 20 years. Although the diatoms present in pond microbial mats at Cape Royds have been previously studied, modern-day knowledge of the characteristics of diatom communities in ponds and small lakes throughout the region is limited. This work sought to find the relationships between water chemistry and diatom community structure in ponds. Because water flow is not a factor in ponds and small lakes, influences of salinity, nutrients, pH and other factors can be more easily distinguished. This study looked at 24 separate bodies of water in the Taylor Valley, Labyrinth region in Wright Valley, Cape Royds and McMurdo Station area on Ross Island. The results suggest that geography, dispersal and historical environmental conditions play a significant role in structuring diatom communities, in addition to water chemistry. The results also expand the knowledge of habitat preferences for some of the species present in this region.

}, keywords = {LTER-MCM, biological sciences, freshwater diatoms, health and environmental sciences, McMurdo Dry Valleys, ponds}, url = {https://search.proquest.com/docview/1655818365?accountid=14503}, author = {Sakaeva, A.}, editor = {Diane M. McKnight} } @article {1079, title = {Environmental factors influencing diatom communities in Antarctic cryoconite holes}, journal = {Environmental Research Letters}, volume = {8}, year = {2013}, month = {12/2013}, pages = {045006}, keywords = {LTER-MCM}, doi = {10.1088/1748-9326/8/4/045006}, url = {http://iopscience.iop.org/1748-9326/8/4/045006/pdf/1748-9326_8_4_045006.pdf}, author = {Lee F. Stanish and Bagshaw, Elizabeth and Diane M. McKnight and Andrew G Fountain and Martyn Tranter} } @article {1122, title = {The ecology of pulse events: insights from an extreme climatic event in a polar desert ecosystem}, journal = {Ecosphere}, volume = {3}, year = {2012}, month = {02/2012}, pages = {art17}, keywords = {LTER-MCM}, doi = {10.1890/ES11-00325.1}, url = {http://www.esajournals.org/doi/abs/10.1890/ES11-00325.1}, author = {Uffe N. Nielsen and Diana H. Wall and Byron Adams and Ross A. Virginia and Ball, Becky and Michael N. Gooseff 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} } @phdthesis {4095, title = {Ecological controls on stream diatom communities in the McMurdo Dry Valleys, Antarctica}, volume = {Ph.D.}, year = {2011}, school = {University of Colorado}, type = {doctoral}, address = {Boulder, CO}, abstract = {

Diatoms are vital primary producers in aquatic ecosystems and useful indicators of environmental change. In climatically sensitive polar areas, diatoms have been used as beacons of climate change, allowing us to monitor physical, chemical, and biological changes. This research aims to improve our understanding of diatom ecology in the pristine and dynamic McMurdo Dry Valleys of Antarctica, where diatoms reside in stream microbial mats. These results aid in understanding how changes in hydrologic regime will affect stream microbial communities, biodiversity, and ecosystem function in a changing environment.

Relationships between hydrologic regime and diatom community composition were investigated using long-term data. Diatom communities were structured by stream physical features, and streams with more similar hydrologic characteristics had more similar communities. Variation in diatom community composition was best explained by hydrologic regime. Small diatoms increased in relative abundances with increasing streamflow, suggesting a role of diatom size in structuring communities. Overall, diatom communities were resistant to flood and drought-like conditions, suggesting an adaptation to frequent disturbances.

The importance of hydrologic regime on drift activity was investigated during three 24- hour experiments. Diel variations in drift could be attributed to diurnal flow peaks. Biomass and diatom cell densities followed a clockwise pattern with stream discharge and support the dominant role of hydraulic processes. The quality of source material differed between seasons and throughout the day. Drifting diatom communities were dominated by\ Fistulifera pelliculosa, which is rarely found in stream mats and suggests a different source. Modeling results suggest that the less firmly anchored marginal mats contribute more to the drift than channel mats in low- flow seasons, while the channel mats become more important during high-flow seasons.

The relationships between diatom and bacterial assemblages in microbial mats were assessed based on phylogenetic and functional relatedness in five Dry Valley streams. Significant relationships between diatom and bacterial communities were found, and co-occurrence analysis identified numerous correlations between individual diatom and bacterial taxa. A consistency in metabolic lifestyles of correlated taxa suggests that the relationships are ecologically relevant. Diatom and bacterial diversity showed opposite patterns, which indicate differences in environmental drivers of diversity for bacteria and eukaryotes.

}, keywords = {LTER-MCM, Antarctica, biological sciences, community ecology, diatoms, earth sciences, McMurdo Dry Valleys, streams}, url = {https://search.proquest.com/docview/915694114?accountid=14503}, author = {Lee F. Stanish}, editor = {Diane M. McKnight} } @article {1161, title = {Effect of instrument-specific response on the analysis of fulvic acid fluorescence spectra}, journal = {Limnology and Oceanography: Methods}, volume = {8}, year = {2010}, month = {07/2010}, pages = {67-78}, keywords = {LTER-MCM}, url = {http://www.aslo.org/lomethods/free/2010/0067.html}, author = {Rose M. Cory and Mathew P. Miller and Diane M. McKnight and Guerard, Jennifer and Penney L. Miller} } @article {4816, title = {Effect of unsteady flow on nitrate loss in an oligotrophic, glacial meltwater stream}, journal = {Journal of Geophysical Research}, volume = {115}, year = {2010}, month = {03/2010}, pages = {G01001}, abstract = {

The McMurdo Dry Valleys of Antarctica are among the coldest, driest ecosystems on Earth. During the austral summer, glacial meltwater supports cyanobacterial mat communities in some streams, but they are not ubiquitous. We conducted a nitrate (NO3-) enrichment tracer injection in Huey Creek to quantify NO3- loss in a Dry Valley stream where algal mats would not obscure hyporheic microbial processes. Unsteady streamflow led to diel variability in the tracer concentration and in surface/subsurface water and solute exchange. Subsequently, concentrations of NO3-, nitrite (NO2-), ammonium (NH4+), and dissolved organic carbon (DOC) varied significantly during the injection, with a net loss of NO3-, NO2-, and DOC, and production of nitrous oxide. These mass changes within a reach were often coincident with high streamflows. Reactivity also coincided with the highest DOC concentrations, suggesting that DOC is the primary limitation to heterotrophic microbial activity in the stream. Together, streamflow and DOC availability create the hot spots and hot moments that dominate NO3- reactivity and removal in this polar desert ecosystem. The combination of spatially and temporally variable hyporheic dynamics and solute availability underscore the limitations of common nutrient uptake metrics and transient storage models when unsteady flow conditions exist.

}, keywords = {LTER-MCM, Antarctica, hot spots/hot moments, hyporheic exchange, nitrogen cycling, unsteady flow}, doi = {10.1029/2009JG001030}, url = {http://doi.wiley.com/10.1029/2009JG001030}, author = {Koch, J. and Diane M. McKnight and Baeseman, J.} } @article {1267, title = {Experimental investigations into processes controlling stream and hyporheic temperatures, Fryxell Basin, Antarctica}, journal = {Advances in Water Resources}, volume = {29}, year = {2006}, pages = {130-153}, keywords = {LTER-MCM}, doi = {LTER}, author = {Cozzetto, K and Diane M. McKnight and Thomas H. Nylen and Andrew G Fountain} } @inbook {1554, title = {Ecological processes in a cold desert ecosystem: the abundance and species distribution of algal mats in glacial meltwater streams in Taylor Valley}, booktitle = {Institute of Arctic and Alpine Research}, series = {Occasional Paper}, volume = {51}, year = {1997}, pages = {108 pp}, publisher = {University of Colorado}, organization = {University of Colorado}, keywords = {LTER-MCM}, url = {http://instaar.colorado.edu/other/download/OP51-ECOLOGICAL-PROCESSES.pdf}, author = {Alexander S. Alger and Diane M. McKnight and Sarah A. Spaulding and Cathy M. Tate}, editor = {Gordon H Shupe and Kathleen A. Welch and R. L. Edwards and Edmund D. Andrews} }