@article {4940, title = {McMurdo Dry Valley lake edge {\textquoteleft}moats{\textquoteright}: The ecological intersection between terrestrial and aquatic polar desert habitat}, journal = {Antarctic Science}, year = {2024}, month = {04/2024}, pages = {1 - 17}, abstract = {

Aquatic ecosystems - lakes, ponds and streams - are hotspots of biodiversity in the cold and arid environment of Continental Antarctica. Environmental change is expected to increasingly alter Antarctic aquatic ecosystems and modify the physical characteristics and interactions within the habitats that they support. Here, we describe physical and biological features of the peripheral \‘moat\’ of a closed-basin Antarctic lake. These moats mediate connectivity amongst streams, lake and soils. We highlight the cyclical moat transition from a frozen winter state to an active open-water summer system, through refreeze as winter returns. Summer melting begins at the lakebed, initially creating an ice-constrained lens of liquid water in November, which swiftly progresses upwards, creating open water in December. Conversely, freezing progresses slowly from the water surface downwards, with water at 1 m bottom depth remaining liquid until May. Moats support productive, diverse benthic communities that are taxonomically distinct from those under the adjacent permanent lake ice. We show how ion ratios suggest that summer exchange occurs amongst moats, streams, soils and sub-ice lake water, perhaps facilitated by within-moat density-driven convection. Moats occupy a small but dynamic area of lake habitat, are disproportionately affected by recent lake-level rises and may thus be particularly vulnerable to hydrological change.

}, keywords = {LTER-MCM, connectivity, ecosystem, ice, microbial mats, transition}, issn = {0954-1020}, doi = {10.1017/S0954102024000087}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/mcmurdo-dry-valley-lake-edge-moats-the-ecological-intersection-between-terrestrial-and-aquatic-polar-desert-habitats/31D94DD51E651603482A3AE6E8A52A57}, author = {Stone, Michael S. and Devlin, Shawn and Ian Hawes and Kathleen A. Welch and Michael N. Gooseff and Cristina D. Takacs-Vesbach and Rachael M. Morgan-Kiss and Byron Adams and John E. Barrett and John C. Priscu and Peter T. Doran} } @article {4935, title = {Sentinel protist taxa of the McMurdo Dry Valley lakes, Antarctica: A review}, journal = {Frontiers in Ecology and Evolution}, volume = {12}, year = {2024}, month = {03/2024}, pages = {1323472}, abstract = {

High-latitude meromictic lakes such as those in the Antarctic McMurdo Dry Valleys (MDV) harbor aquatic ecosystems dominated by the microbial loop. Within this habitat, which is limited year-round by light and nutrients, protists, or single celled eukaryotes, play outsized roles in the food web as the dominant primary producers and the apex predators. Thus, the MDV lake ecosystem represents an ideal system to study the role of sentinel protist taxa in carbon and nutrient cycling. The perennially ice-covered lakes are part of the McMurdo Long Term Ecological Research (McM LTER; mcmlter.org) established in 1993. In this review we will highlight the diversity and trophic roles of the MDV lake protist community and compare environmental factors driving spatiotemporal patterns in key protist taxa in two lakes within the McM LTER, Lakes Bonney and Fryxell. We will then discuss lessons learned from manipulated experiments on the impact of current and future climate-driven environmental change on sensitive protist taxa. Last, we will integrate knowledge gained from 25 years of lab-controlled experiments on key photosynthetic protists to extend our understanding of the function of these extremophiles within the MDV aquatic food webs. Our research group has studied the distribution and function of the MDV microbial community for nearly two decades, training the next generation of scientists to tackle future problems of these globally significant microbes. This review article will also highlight early career scientists who have contributed to this body of work and represent the future of scientific understanding in the Anthropocene.

}, keywords = {LTER-MCM, Antarctica, Disturbance, McMurdo Dry Valley lakes, phytoplankton, protist}, doi = {10.3389/fevo.2024.1323472}, url = {https://www.frontiersin.org/articles/10.3389/fevo.2024.1323472}, author = {Rachael M. Morgan-Kiss and Popson, Devon and Pereira, Rochelle and Dolhi-Binder, J and Teufel, Amber G. and Li, Wei and Kalra, Isha and Sherwell, Shasten S. and Reynebeau, Emily and Cristina D. Takacs-Vesbach} } @article {4839, title = {Impact of meltwater flow intensity on the spatiotemporal heterogeneity of microbial mats in the McMurdo Dry Valleys, Antarctica}, journal = {ISME Communications}, volume = {3}, year = {2023}, month = {01/2023}, pages = {3}, abstract = {

The meltwater streams of the McMurdo Dry Valleys are hot spots of biological diversity in the climate-sensitive polar desert landscape. Microbial mats, largely comprised of cyanobacteria, dominate the streams which flow for a brief window of time (~10 weeks) over the austral summer. These communities, critical to nutrient and carbon cycling, display previously uncharacterized patterns of rapid destabilization and recovery upon exposure to variable and physiologically detrimental conditions. Here, we characterize changes in biodiversity, transcriptional responses and activity of microbial mats in response to hydrological disturbance over spatiotemporal gradients. While diverse metabolic strategies persist between marginal mats and main channel mats, data collected from 4 time points during the austral summer revealed a homogenization of the mat communities during the mid-season peak meltwater flow, directly influencing the biogeochemical roles of this stream ecosystem. Gene expression pattern analyses identified strong functional sensitivities of nitrogen-fixing marginal mats to changes in hydrological activities. Stress response markers detailed the environmental challenges of each microhabitat and the molecular mechanisms underpinning survival in a polar desert ecosystem at the forefront of climate change. At mid and end points in the flow cycle, mobile genetic elements were upregulated across all mat types indicating high degrees of genome evolvability and transcriptional synchronies. Additionally, we identified novel antifreeze activity in the stream microbial mats indicating the presence of ice-binding proteins (IBPs). Cumulatively, these data provide a new view of active intra-stream diversity, biotic interactions and alterations in ecosystem function over a high-flow hydrological regime.

}, keywords = {LTER-MCM}, doi = {10.1038/s43705-022-00202-8}, url = {https://www.nature.com/articles/s43705-022-00202-8}, author = {Zoumplis, Angela and Kolody, Bethany C. and Kaul, Drishti and Zheng, Hong and Venepally, Pratap and Diane M. McKnight and Cristina D. Takacs-Vesbach and DeVries, Arthur L. and Allen, Andrew E.} } @article {4759, title = {Limits to the three domains of life: Lessons from community assembly along an Antarctic salinity gradient}, journal = {Extremophiles}, volume = {26}, year = {2022}, month = {04/2022}, pages = {15}, abstract = {

Extremophiles exist among all three domains of life; however, physiological mechanisms for surviving harsh environmental conditions differ among Bacteria, Archaea and Eukarya. Consequently, we expect that domain-specific variation of diversity and community assembly patterns exist along environmental gradients in extreme environments. We investigated inter-domain community compositional differences along a high-elevation salinity gradient in the McMurdo Dry Valleys, Antarctica. Conductivity for 24 soil samples collected along the gradient ranged widely from 50 to 8355 \µS cm-1. Taxonomic richness varied among domains, with a total of 359 bacterial, 2 archaeal, 56 fungal, and 69 non-fungal eukaryotic operational taxonomic units (OTUs). Richness for bacteria, archaea, fungi, and non-fungal eukaryotes declined with increasing conductivity (all P\ \<\ 0.05). Principal coordinate ordination analysis (PCoA) revealed significant (ANOSIM R\ =\ 0.97) groupings of low/high salinity bacterial OTUs, while OTUs from other domains were not significantly clustered. Bacterial beta diversity was unimodally distributed along the gradient and had a nested structure driven by species losses, whereas in fungi and non-fungal eukaryotes beta diversity declined monotonically without strong evidence of nestedness. Thus, while increased salinity acts as a stressor in all domains, the mechanisms driving community assembly along the gradient differ substantially between the domains.

}, keywords = {LTER-MCM, Antarctica, inter-domain response, McMurdo Dry Valleys, salinity, species richness patterns}, doi = {10.1007/s00792-022-01262-3}, url = {https://link.springer.com/article/10.1007/s00792-022-01262-3}, author = {Jiang, Xiaoben and David J. Van Horn and Okie, Jordan G. and Heather N. Buelow and Schwartz, Egbert and Colman, Daniel R. and Feeser, Kelli L. and Cristina D. Takacs-Vesbach} } @article {4613, title = {Year-round and long-term phytoplankton dynamics in Lake Bonney, a permanently ice-covered Antarctic lake}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {04/2021}, pages = {e2020JG005925}, abstract = {

Lake Bonney (McMurdo Dry Valleys, east Antarctica) represents a year-round refugium for life adapted to permanent extreme conditions. Despite intensive research since the 1960s, due to the logistical constraints posed by 4-months of 24-h darkness, knowledge of how the resident photosynthetic microorganisms respond to the polar winter is limited. In addition, the lake level has risen by more than 3 m since 2004: impacts of rapid lake level rise on phytoplankton community structure is also poorly understood. From 2004 to 2015 an in situ submersible spectrofluorometer (bbe FluoroProbe) was deployed in Lake Bonney during the austral summer to quantify the vertical structure of four functional algal groups (green algae, mixed algae, and cryptophytes, cyanobacteria). During the 2013\–2014 field season the Fluoroprobe was mounted on autonomous cable-crawling profilers deployed in both the east and west lobes of Lake Bonney, obtaining the first daily phytoplankton profiles through the polar night. Our findings showed that phytoplankton communities were differentially impacted by physical and chemical factors over long-term versus seasonal time scales. Following a summer of rapid lake level rise (2010\–2011), an increase in depth integrated chlorophyll a (chl-a) occurred in Lake Bonney caused by stimulation of photoautotrophic green algae. Conversely, peaks in chl-a during the polar night were associated with an increase in mixotrophic haptophytes and cryptophytes. Collectively our data reveal that phytoplankton groups possessing variable trophic abilities are differentially competitive during seasonal and long-term time scales owing to periods of higher nutrients (photoautotrophs) versus light/energy limitation (mixotrophs).

}, keywords = {LTER-MCM, algae, Antarctic, fluorometry, ice, lakes, light, profiling, winter}, issn = {2169-8953}, doi = {10.1029/2020JG005925}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG005925}, author = {Patriarche, Jeffrey D. and John C. Priscu and Cristina D. Takacs-Vesbach and Winslow, Luke A. and Myers, Krista F. and Heather N. Buelow and Rachael M. Morgan-Kiss and Peter T. Doran} } @article {4136, title = {Local and Regional Scale Heterogeneity Drive Bacterial Community Diversity and Composition in a Polar Desert}, journal = {Frontiers in Microbiology}, volume = {9}, year = {2018}, month = {08/2018}, abstract = {

The distribution of organisms in an environment is neither uniform nor random but is instead spatially patterned. The factors that control this patterning are complex and the underlying mechanisms are poorly understood. Soil microbes are critical to ecosystem function but exhibit highly complex distributions and community dynamics due in large part to the scale-dependent effects of environmental heterogeneity. To better understand the impact of environmental heterogeneity on the distribution of soil microbes, we sequenced the 16S rRNA gene from bacterial communities in the microbe-dominated polar desert ecosystem of the McMurdo Dry Valleys (MDV), Antarctica. Significant differences in key edaphic variables and alpha diversity were observed among the three lake basins of the Taylor Valley (Kruskal\–Wallis; pH: χ2 = 68.89, P \< 0.001, conductivity: χ2 = 35.03, P \< 0.001, observed species: χ2 = 7.98, P = 0.019 and inverse Simpson: χ2 = 18.52, P \< 0.001) and each basin supported distinctive microbial communities (ANOSIM R = 0.466, P = 0.001, random forest ratio of 14.1). However, relationships between community structure and edaphic characteristics were highly variable and contextual, ranging in magnitude and direction across regional, basin, and local scales. Correlations among edaphic factors (pH and soil conductivity) and the relative abundance of specific phyla were most pronounced along local environmental gradients in the Lake Fryxell basin where Acidobacteria, Bacteroidetes, and Proteobacteria declined while Deinococcus\–Thermus and Gemmatimonadetes increased with soil conductivity (all P \< 0.1). Species richness was most strongly related to the soil conductivity gradient present within this study system. We suggest that the relative importance of pH versus soil conductivity in structuring microbial communities is related to the length of edaphic gradients and the spatial scale of sampling. These results highlight the importance of conducting studies over large ranges of key environmental gradients and across multiple spatial scales to assess the influence of environmental heterogeneity on the composition and diversity of microbial communities.

}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2018.01928}, url = {https://www.frontiersin.org/article/10.3389/fmicb.2018.01928/full}, author = {Feeser, Kelli L. and David J. Van Horn and Heather N. Buelow and Colman, Daniel R. and McHugh, Theresa A. and Okie, Jordan G. and Schwartz, Egbert and Cristina D. Takacs-Vesbach} } @article {4022, title = {Decadal ecosystem response to an anomalous melt season in a polar desert in Antarctica}, journal = {Nature Ecology \& Evolution}, volume = {1}, year = {2017}, month = {09/2017}, pages = {1334-1338}, keywords = {LTER-MCM}, doi = {10.1038/s41559-017-0253-0}, url = {https://www.nature.com/articles/s41559-017-0253-0}, author = {Michael N. Gooseff and John E. Barrett and Byron Adams and Peter T. Doran and Andrew G Fountain and W. Berry Lyons and Diane M. McKnight and John C. Priscu and Eric R. Sokol and Cristina D. Takacs-Vesbach and Martijn L. Vandegehuchte and Ross A. Virginia and Diana H. Wall} } @article {4024, title = {Decoupled responses of soil bacteria and their invertebrate consumer to warming, but not freeze-thaw cycles, in the Antarctic Dry Valleys}, journal = {Ecology Letters}, volume = {20}, year = {2017}, month = {10/2017}, pages = {1242-1249}, abstract = {

Altered temperature profiles resulting in increased warming and freeze\–thaw cycle (FTC) frequency pose great ecological challenges to organisms in alpine and polar ecosystems. We performed a laboratory microcosm experiment to investigate how temperature variability affects soil bacterial cell numbers, and abundance and traits of soil microfauna (the microbivorous nematode Scottnema lindsayae) from McMurdo Dry Valleys, Antarctica. FTCs and constant freezing shifted nematode body size distribution towards large individuals, driven by higher mortality among smaller individuals. FTCs reduced both bacterial and nematode abundance, but bacterial cell numbers also declined under warming, demonstrating decoupled consumer\–prey responses. We predict that higher occurrence of FTCs in cold ecosystems will select for large body size within soil microinvertebrates and overall reduce their abundance. In contrast, warm temperatures without FTCs could lead to divergent responses in soil bacteria and their microinvertebrate consumers, potentially affecting energy and nutrient transfer rates in soil food webs of cold ecosystems.

}, keywords = {LTER-MCM}, doi = {10.1111/ele.12819}, url = {http://onlinelibrary.wiley.com/doi/10.1111/ele.12819/full}, author = {Matthew Knox and Andriuzzi, Walter S. and Heather N. Buelow and Cristina D. Takacs-Vesbach and Byron Adams and Diana H. Wall} } @article {4103, title = {Niche specialization of bacteria in permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica}, journal = {Environmental Microbiology}, volume = {19}, year = {2017}, month = {06/2017}, pages = {2258 - 2271}, abstract = {

Perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica, are chemically stratified with depth and have distinct biological gradients. Despite long-term research on these unique environments, data on the structure of the microbial communities in the water columns of these lakes are scarce. Here, we examined bacterial diversity in five ice-covered Antarctic lakes by 16S rRNA gene-based pyrosequencing. Distinct communities were present in each lake, reflecting the unique biogeochemical characteristics of these environments. Further, certain bacterial lineages were confined exclusively to specific depths within each lake. For example, candidate division WM88 occurred solely at a depth of 15 m in Lake Fryxell, whereas unknown lineages of\ Chlorobi\ were found only at a depth of 18 m in Lake Miers, and two distinct classes of\ Firmicutes\ inhabited East and West Lobe Bonney at depths of 30 m. Redundancy analysis revealed that community variation of bacterioplankton could be explained by the distinct conditions of each lake and depth; in particular, assemblages from layers beneath the chemocline had biogeochemical associations that differed from those in the upper layers. These patterns of community composition may represent bacterial adaptations to the extreme and unique biogeochemical gradients of ice-covered lakes in the McMurdo Dry Valleys.

}, keywords = {LTER-MCM}, doi = {10.1111/emi.2017.19.issue-610.1111/1462-2920.13721}, url = {https://onlinelibrary.wiley.com/doi/pdf/10.1111/1462-2920.13721}, author = {Kwon, Miye and Kim, Mincheol and Cristina D. Takacs-Vesbach and Lee, Jaejin and Hong, Soon Gyu and Kim, Sang Jong and John C. Priscu and Kim, Ok-Sun} } @article {4021, title = {Primary productivity as a control over soil microbial diversity along environmental gradients in a polar desert ecosystem}, journal = {PeerJ}, volume = {5}, year = {2017}, month = {07/2017}, pages = {e3377}, abstract = {

Primary production is the fundamental source of energy to foodwebs and ecosystems, and is thus an important constraint on soil communities. This coupling is particularly evident in polar terrestrial ecosystems where biological diversity and activity is tightly constrained by edaphic gradients of productivity (e.g., soil moisture, organic carbon availability) and geochemical severity (e.g., pH, electrical conductivity). In the McMurdo Dry Valleys of Antarctica, environmental gradients determine numerous properties of soil communities and yet relatively few estimates of gross or net primary productivity (GPP, NPP) exist for this region. Here we describe a survey utilizing pulse amplitude modulation (PAM) fluorometry to estimate rates of GPP across a broad environmental gradient along with belowground microbial diversity and decomposition. PAM estimates of GPP ranged from an average of 0.27 mmol O2/m2/s in the most arid soils to an average of 6.97 mmol O2/m2/s in the most productive soils, the latter equivalent to 217 g C/m2/y in annual NPP assuming a 60 day growing season. A diversity index of four carbon-acquiring enzyme activities also increased with soil productivity, suggesting that the diversity of organic substrates in mesic environments may be an additional driver of microbial diversity. Overall, soil productivity was a stronger predictor of microbial diversity and enzymatic activity than any estimate of geochemical severity. These results highlight the fundamental role of environmental gradients to control community diversity and the dynamics of ecosystem-scale carbon pools in arid systems.\ 

}, keywords = {LTER-MCM}, doi = {10.7717/peerj.3377}, url = {https://peerj.com/articles/3377/}, author = {Kevin M. Geyer and Cristina D. Takacs-Vesbach and Michael N. Gooseff and John E. Barrett} } @article {4017, title = {Microbial Community Dynamics in Two Polar Extremes: The Lakes of the McMurdo Dry Valleys and the West Antarctic Peninsula Marine Ecosystem}, journal = {BioScience}, volume = {66}, year = {2016}, month = {Jan-10-2016}, pages = {829 - 847}, keywords = {LTER-MCM}, issn = {0006-3568}, doi = {10.1093/biosci/biw103}, url = {https://academic.oup.com/bioscience/article-lookup/doi/10.1093/biosci/biw103https://academic.oup.com/bioscience/article/66/10/829/2236137/Microbial-Community-Dynamics-in-Two-Polar-Extremes}, author = {Bowman, Jeff S. and Trista J. Vick-Majors and Rachael M. Morgan-Kiss and Cristina D. Takacs-Vesbach and Hugh W. Ducklow and John C. Priscu} } @article {3952, title = {Microbial Community Responses to Increased Water and Organic Matter in the Arid Soils of the McMurdo Dry Valleys, Antarctica}, journal = {Frontiers in Microbiology}, volume = {7}, year = {2016}, month = {07/2016}, chapter = {1040}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2016.01040}, url = {http://journal.frontiersin.org/article/10.3389/fmicb.2016.01040}, author = {Heather N. Buelow and Winter, Ara S. and David J. Van Horn and John E. Barrett and Michael N. Gooseff and Schwartz, Egbert and Cristina D. Takacs-Vesbach} } @article {3959, title = {Nutrient treatments alter microbial mat colonization in two glacial meltwater streams from the McMurdo Dry Valleys, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {92}, year = {2016}, month = {03/2016}, pages = {fiw049}, abstract = {

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,\ Fistulifera pelliculosa. 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.

}, keywords = {LTER-MCM}, doi = {10.1093/femsec/fiw049}, url = {http://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw049}, author = {Tyler J. Kohler and David J. Van Horn and Darling, Joshua P. and Cristina D. Takacs-Vesbach and Diane M. McKnight}, editor = {Wagner, Dirk} } @article {3958, title = {Patterns of bacterial biodiversity in the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {92}, year = {2016}, month = {08/2016}, pages = {fiw148}, abstract = {

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 \∼24 000 operational taxonomic units (\<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 \< 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.

}, keywords = {LTER-MCM}, doi = {10.1093/femsec/fiw148}, url = {http://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw148}, author = {David J. Van Horn and Wolf, Caitlin R. and Colman, Daniel R. and Jiang, Xiaoben and Tyler J. Kohler and Diane M. McKnight and Lee F. Stanish and Yazzie, Terrill and Cristina D. Takacs-Vesbach} } @article {3522, title = {Niche and metabolic principles explain patterns of diversity and distribution: theory and a case study with soil bacterial communities}, journal = {Proceedings of the Royal Society B: Biological Sciences}, volume = {282}, year = {2015}, month = {05/2015}, pages = {2630}, abstract = {

The causes of biodiversity patterns are controversial and elusive due to complex environmental variation, covarying changes in communities, and lack of baseline and null theories to differentiate straightforward causes from more complex mechanisms. To address these limitations, we developed general diversity theory integrating metabolic principles with niche-based community assembly. We evaluated this theory by investigating patterns in the diversity and distribution of soil bacteria taxa across four orders of magnitude variation in spatial scale on an Antarctic mountainside in low complexity, highly oligotrophic soils. Our theory predicts that lower temperatures should reduce taxon niche widths along environmental gradients due to decreasing growth rates, and the changing niche widths should lead to contrasting α- and β-diversity patterns. In accord with the predictions, α-diversity, niche widths and occupancies decreased while β-diversity increased with increasing elevation and decreasing temperature. The theory also successfully predicts a hump-shaped relationship between α-diversity and pH and a negative relationship between α-diversity and salinity. Thus, a few simple principles explained systematic microbial diversity variation along multiple gradients. Such general theory can be used to disentangle baseline effects from more complex effects of temperature and other variables on biodiversity patterns in a variety of ecosystems and organisms.

}, keywords = {LTER-MCM}, issn = {0962-8452}, doi = {10.1098/rspb.2014.2630}, url = {http://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2014.2630}, author = {Okie, Jordan G. and David J. Van Horn and Storch, David and John E. Barrett and Michael N. Gooseff and Kopsova, Lenka and Cristina D. Takacs-Vesbach} } @article {3214, title = {Autonomous Year-Round Sampling and Sensing to Explore the Physical and Biological Habitability of Permanently Ice-Covered Antarctic Lakes}, journal = {Marine Technology Society Journal}, volume = {48}, year = {2014}, month = {Jan-09-2014}, pages = {8 - 17}, abstract = {

The lakes of the McMurdo Dry Valleys, Antarctica, are some of the only systems on our planet that are perennially ice-covered and support year-round metabolism. As such, these ecosystems can provide important information on conditions and life in polar regions on Earth and on other icy worlds in our solar system. Working in these extreme environments of the Dry Valleys poses many challenges, particularly with respect to data collection during dark winter months when logistical constraints make fieldwork difficult. In this paper, we describe the motivation, design, and challenges for this recently deployed instrumentation in Lake Bonney, a lake that has been the subject of summer research efforts for more than 40 years. The instrumentation deployed includes autonomous water, phytoplankton, and sediment samplers as well as cable-mounted profiling platforms with dissolved gas and fluorometry sensors. Data obtained from these instruments will allow us, for the first time, to define the habitability of this environment during the polar night. We include lessons learned during deployment and recommendations for effective instrument operation in these extreme conditions.

}, keywords = {LTER-MCM}, issn = {00253324}, doi = {10.4031/MTSJ.48.5.6}, url = {http://openurl.ingenta.com/content/xref?genre=article\&issn=0025-3324\&volume=48\&issue=5\&spage=8http://www.ingentaconnect.com/content/mts/mtsj/2014/00000048/00000005/art00002}, author = {Winslow, Luke A. and Hilary A. Dugan and Heather N. Buelow and Cronin, Kyle D. and John C. Priscu and Cristina D. Takacs-Vesbach and Peter T. Doran} } @article {1054, title = {Bacterial community composition of divergent soil habitats from a polar desert.}, journal = {FEMS Microbiology Ecology}, volume = {89}, year = {2014}, month = {08/2014}, pages = {490-494}, type = {Short Communication}, chapter = {490}, abstract = {Edaphic factors such as pH, organic matter, and salinity are often the most significant drivers of diversity patterns in soil bacterial communities. Desert ecosystems in particular are model locations for examining such relationships as food web complexity is low and the soil environment is biogeochemically heterogeneous. Here, we present the findings from a 16S rRNA gene sequencing approach used to observe the differences in diversity and community composition among three divergent soil habitats of the McMurdo Dry Valleys, Antarctica. Results show that alpha diversity is significantly lowered in high pH soils, which contain higher proportions of the phyla Acidobacteria and Actinobacteria, while mesic soils with higher soil organic carbon (and ammonium) content contain high proportions of Nitrospira, a nitrite-oxidizing bacteria. Taxonomic community resolution also had a significant impact on our conclusions, as pH was the primary predictor of phylum-level diversity, while moisture was the most significant predictor of diversity at the genus level. Predictive power also increased with increasing taxonomic resolution, suggesting a potential increase in nic}, keywords = {LTER-MCM}, doi = {10.1111/1574-6941.12306}, author = {Kevin M. Geyer and Adam E. Altrichter and Cristina D. Takacs-Vesbach and Michael N. Gooseff and John E. Barrett} } @article {1055, title = {Characterization of Growing Bacterial Populations in McMurdo Dry Valley Soils through Stable Isotope Probing with 18O-water.}, journal = {FEMS Microbiology Ecology.}, volume = {89}, year = {2014}, month = {08/2014}, pages = {415-425}, chapter = {415}, abstract = {Soil 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.}, keywords = {LTER-MCM}, doi = {10.1111/1574-6941.12349}, author = {Schwartz, E. and David J. Van Horn and Heather N. Buelow and Michael N. Gooseff and John E. Barrett and Cristina D. Takacs-Vesbach and Okie, J.G.} } @article {1064, title = {Soil microbial responses to increased moisture and organic resources along a salinity gradient in a polar desert.}, journal = {Applied and Environmental Microbiology.}, volume = {80}, year = {2014}, month = {05/2014}, pages = {3034-3043}, chapter = {3034}, abstract = {Microbial communities in extreme environments often have low diversity and specialized physiologies suggesting a limited resistance to change. The McMurdo Dry Valleys (MDV) are a microbially dominated, extreme ecosystem currently undergoing climate change-induced disturbances, including the melting of massive buried ice, cutting through of permafrost by streams, and warming events. These processes are increasing moisture across the landscape, altering conditions for soil communities by mobilizing nutrients and salts and stimulating autotrophic carbon inputs to soils. The goal of this study was to determine the effects of resource addition (water/organic matter) on the composition and function of microbial communities in the MDV along a natural salinity gradient representing an additional gradient of stress in an already extreme environment. Soil respiration and the activity of carbon-acquiring extracellular enzymes increased significantly (P < 0.05) with the addition of resources at the low- and moderate-salinity sites but not the high-salinity site. The bacterial community composition was altered, with an increase in Proteobacteria and Firmicutes with water and organic matter additions at the low- and moderate-salinity sites and a near dominance of Firmicutes at the high-salinity site. Principal coordinate analyses of all samples using a phylogenetically informed distance matrix (UniFrac) demonstrated discrete clustering among sites (analysis of similarity [ANOSIM], P < 0.05 and R > 0.40) and among most treatments within sites. The results from this experimental work suggest that microbial communities in this environment will undergo rapid change in response to the altered resources resulting from climate change impacts occurring in this region.}, keywords = {LTER-MCM}, doi = {10.1128/AEM.03414-13}, author = {David J. Van Horn and Okie, J.G. and Heather N. Buelow and Michael N. Gooseff and John E. Barrett and Cristina D. Takacs-Vesbach} } @article {1084, title = {Environmental controls over bacterial communities in polar desert soils}, journal = {Ecosphere}, volume = {4}, year = {2013}, month = {10/2013}, pages = {art127}, keywords = {LTER-MCM}, doi = {10.1890/ES13-00048.1}, author = {Kevin M. Geyer and Adam E. Altrichter and David J. Van Horn and Cristina D. Takacs-Vesbach and Michael N. Gooseff and John E. Barrett} } @article {1092, title = {Factors Controlling Soil Microbial Biomass and Bacterial Diversity and Community Composition in a Cold Desert Ecosystem: Role of Geographic Scale}, journal = {PLoS ONE}, volume = {8}, year = {2013}, month = {06/2013}, pages = {e66103}, keywords = {LTER-MCM}, doi = {10.1371/journal.pone.0066103.s003}, url = {http://www.plosone.org/article/info\%3Adoi\%2F10.1371\%2Fjournal.pone.0066103}, author = {David J. Van Horn and Van Horn, M. Lee and John E. Barrett and Michael N. Gooseff and Adam E. Altrichter and Kevin M. Geyer and Lydia H. Zeglin and Cristina D. Takacs-Vesbach} } @article {1089, title = {Seasonal controls on snow distribution and aerial ablation at the snow-patch and landscape scales, McMurdo Dry Valleys, Antarctica}, journal = {The Cryosphere}, volume = {7}, year = {2013}, month = {09/2013}, pages = {917 - 931}, keywords = {LTER-MCM}, doi = {10.5194/tc-7-917-2013}, url = {http://www.the-cryosphere.net/7/917/2013/tc-7-917-2013.html}, author = {Eveland, Jeffery and Michael N. Gooseff and Lampkin, Derrick J. and John E. Barrett and Cristina D. Takacs-Vesbach} } @article {1090, title = {Spatial and temporal patterns of snow accumulation and aerial ablation across the McMurdo Dry Valleys, Antarctica}, journal = {Hydrological Processes}, volume = {27}, year = {2013}, month = {09/2013}, pages = {2864 - 2875}, keywords = {LTER-MCM}, doi = {10.1002/hyp.9407}, url = {http://onlinelibrary.wiley.com/doi/10.1002/hyp.9407/pdf}, author = {Eveland, Jeffery and Michael N. Gooseff and Lampkin, Derrick J. and John E. Barrett and Cristina D. Takacs-Vesbach} } @article {1128, title = {Bacterial Community Structure Along Moisture Gradients in the Parafluvial Sediments of Two Ephemeral Desert Streams}, journal = {Microbial Ecology}, volume = {61}, year = {2011}, month = {4/2011}, pages = {543 - 556}, keywords = {LTER-MCM}, doi = {10.1007/s00248-010-9782-7}, url = {http://www.springerlink.com/content/r83j53334v5n505w/}, author = {Lydia H. Zeglin and Clifford N. Dahm and John E. Barrett and Michael N. Gooseff and Shannon K. Fitpatrick and Cristina D. Takacs-Vesbach} } @inbook {1171, title = {Factors promoting microbial diversity in the McMurdo Dry Valleys}, booktitle = {Life in Antarctic Deserts and other Cold Dry Environments: Astrobiological Analogues}, series = {Cambridge Astrobiology}, volume = {5}, year = {2010}, pages = {221-257}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, keywords = {LTER-MCM}, isbn = {9780521889193}, doi = {10.1017/CBO9780511712258.008}, url = {http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511712258\&cid=CBO9780511712258A015}, author = {Cristina D. Takacs-Vesbach and Lydia H. Zeglin and Michael N. Gooseff and John E. Barrett and John C. Priscu} } @inbook {1172, title = {The legacy of aqueous environments on soils of the McMurdo Dry Valleys: contexts for future exploration of martian soils}, booktitle = {Life in Antarctic Deserts and other Cold Dry Environments}, volume = {5}, year = {2010}, pages = {78 - 109}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, address = {Cambridge}, keywords = {LTER-MCM}, isbn = {9780521889193}, doi = {10.1017/CBO9780511712258.003}, url = {http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511712258\&cid=CBO9780511712258A010}, author = {John E. Barrett and Poage, M and Michael N. Gooseff and Cristina D. Takacs-Vesbach} } @book {1173, title = {Life in Antarctic Deserts and Other Cold Environments}, series = {Astrobiological Analogs}, volume = {5}, year = {2010}, pages = {307}, publisher = {Cambridge University Press.}, organization = {Cambridge University Press.}, address = {Cambridge}, keywords = {LTER-MCM, Planetary Science}, isbn = {9780511712258}, doi = {10.1017/CBO9780511712258}, url = {http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511712258}, author = {Peter T. Doran and W. Berry Lyons and Diane M. McKnight}, editor = {Diane M. McKnight and Michael N. Gooseff and Cristina D. Takacs-Vesbach and Jill A. Mikucki and Martyn Tranter and Sun, Henry J} } @article {1186, title = {Hydrologic characteristics of lake- and stream-side riparian wetted margins in the McMurdo Dry Valleys, Antarctica}, journal = {Hydrological Processes}, volume = {23}, year = {2009}, pages = {1255-1267}, keywords = {LTER-MCM}, doi = {LTER}, author = {Northcott, M and Michael N. Gooseff and John E. Barrett and Lydia H. Zeglin and Cristina D. Takacs-Vesbach and Humphrey, J} } @article {1189, title = {Landscape Distribution of Microbial Activity in the McMurdo Dry Valleys: Linked Biotic Processes, Hydrology, and Geochemistry in a Cold Desert Ecosystem}, journal = {Ecosystems}, volume = {12}, year = {2009}, pages = {562-573}, keywords = {LTER-MCM}, doi = {LTER}, author = {Lydia H. Zeglin and Sinsabaugh, R and John E. Barrett and Michael N. Gooseff and Cristina D. Takacs-Vesbach} } @article {1193, title = {Spatial variation in soil active-layer geochemistry across hydrologic margins in polar desert ecosystems.}, journal = {Hydrology and Earth System Sciences}, volume = {13}, year = {2009}, pages = {2349-2358}, keywords = {LTER-MCM}, doi = {LTER}, author = {John E. Barrett and Michael N. Gooseff and Cristina D. Takacs-Vesbach} } @article {1196, title = {Thermal Characterisation of Active Layer Across a Soil Moisture Gradient in the McMurdo Dry Valleys, Antarctica}, journal = {Permafrost and Periglacial Processes}, volume = {20}, year = {2009}, pages = {27-39}, keywords = {LTER-MCM}, doi = {10.1002/ppp.634}, author = {Ikard, S and Michael N. Gooseff and John E. Barrett and Cristina D. Takacs-Vesbach} } @phdthesis {1219, title = {Microbial diversity and function at aquatic- terrestrial interfaces in desert ecosystems.}, volume = {Ph.D.}, year = {2008}, school = {University of New Mexico}, type = {doctoral}, keywords = {LTER-MCM}, doi = {LTER}, author = {Lydia H. Zeglin} } @article {1224, title = {Stoichiometry of soil enzyme activity at global scale.}, journal = {Ecology Letters}, volume = {11}, year = {2008}, pages = {1252-1264}, keywords = {LTER-MCM}, doi = {LTER}, author = {Sinsabaugh, R and Gallo, M and Gartner, T and Hobbie, S and Holland, K and Keeler, B and Powers, J and Stursova, M and Cristina D. Takacs-Vesbach and Waldrop, M and Wallenstein, M and Lauber, M and Zak, D and Lydia H. Zeglin and Weintraub, M and Ahmed, B and Allison, S and Crenshaw, C and Contosta, A and Cusack, D and Frey, S} } @article {1240, title = {Controls on the spatial dimensions of wetted hydrologic margins of two antarctic lakes}, journal = {Vadose Zone Journal}, volume = {6}, year = {2007}, pages = {841-848}, keywords = {LTER-MCM}, doi = {10.2136/​vzj2006.0161}, author = {Michael N. Gooseff and John E. Barrett and Melissa L. Northcott and D. Brad Bate and Kenneth R. Hill and Lydia H. Zeglin and Bobb, M and Cristina D. Takacs-Vesbach} } @thesis {1276, title = {Spatial Patterns of Bacterial Diversity in Cold Desert Riparian Zones.}, volume = {B.S.}, year = {2006}, school = {University of New Mexico}, type = {bachelors}, keywords = {LTER-MCM}, doi = {LTER}, author = {Bobb, M} } @article {1398, title = {Bacterial dissolved organic carbon demand in antarctic dry valley lakes}, journal = {Limnology and Oceanography}, volume = {46}, year = {2001}, month = {07/2001}, pages = {1189-1194}, type = {Journal}, keywords = {LTER-MCM, Biggie}, doi = {10.4319/lo.2001.46.5.1189}, url = {http://www.jstor.org/stable/2671031}, author = {Cristina D. Takacs-Vesbach and John C. Priscu and Diane M. McKnight} } @article {1450, title = {Carbon transformations in a perennially ice-covered Antarctic lake}, year = {1999}, keywords = {LTER-MCM}, author = {John C. Priscu and Craig F. Wolf and Cristina D. Takacs-Vesbach and Christian H. Fritsen and Johanna Laybourn-Parry and Emily C. Roberts and Birgit Sattl} } @phdthesis {1458, title = {Factors Affecting the Distribution and Dynamics of Bacterioplankton Biomass and Diversity in Taylor Valley Lakes, Antarctica}, volume = {Ph.D.}, year = {1999}, school = {Montana State University}, type = {doctoral}, keywords = {LTER-MCM}, author = {Cristina D. Takacs-Vesbach} } @article {1459, title = {Geomicrobiology of sub-glacial ice above Vostok Station}, journal = {Science}, volume = {286}, year = {1999}, pages = {2141-2144}, keywords = {LTER-MCM}, doi = {10.1126/science.286.5447.2141}, author = {John C. Priscu and Edward E. Adams and W. Berry Lyons and Mary A. Voytek and David W. Mogk and Robert L. Brown and Christopher P. McKay and Cristina D. Takacs-Vesbach and Kathleen A. Welch and Craig F. Wolf and Julie D. Kirshtein and Recep Avci} } @article {1487, title = {Bacterioplankton dynamics in the McMurdo Dry Valley lakes, Antarctica: Production and biomass loss over four seasons}, journal = {Microbial Ecology}, volume = {36}, year = {1998}, pages = {239-250}, keywords = {LTER-MCM}, author = {Cristina D. Takacs-Vesbach and John C. Priscu} } @article {1528, title = {The role of phytoplankton extracellular release in bacterioplankton growth of Taylor Valley Lakes, Antarctica}, journal = {Antarctic Journal of the United States - 1996 Review Issue (NSF 98-28)}, volume = {31}, year = {1998}, pages = {211-212}, keywords = {LTER-MCM}, author = {Cristina D. Takacs-Vesbach and John C. Priscu} } @article {1568, title = {Bacterial growth in Antarctic lakes: The role of phytoplankton extracellular release}, journal = {Bacterial growth in Antarctic lakes: The role of phytoplankton extracellular}, year = {1996}, keywords = {LTER-MCM}, author = {Cristina D. Takacs-Vesbach and John C. Priscu} } @article {1602, title = {Responses of bacterial growth to inorganic and organic nutrient enrichment in the lakes of the dry valleys, Antarctica}, journal = {Antarctic Journal of the US}, volume = {30}, year = {1995}, pages = {303-305}, keywords = {LTER-MCM}, author = {Cristina D. Takacs-Vesbach and John C. Priscu} }