TY - JOUR T1 - Impact of meltwater flow intensity on the spatiotemporal heterogeneity of microbial mats in the McMurdo Dry Valleys, Antarctica JF - ISME Communications Y1 - 2023 A1 - Zoumplis, Angela A1 - Kolody, Bethany C. A1 - Kaul, Drishti A1 - Zheng, Hong A1 - Venepally, Pratap A1 - Diane M. McKnight A1 - Cristina D. Takacs-Vesbach A1 - DeVries, Arthur L. A1 - Allen, Andrew E. AB -

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.

VL - 3 UR - https://www.nature.com/articles/s43705-022-00202-8 IS - 1 ER - TY - JOUR T1 - Limits to the three domains of life: Lessons from community assembly along an Antarctic salinity gradient JF - Extremophiles Y1 - 2022 A1 - Jiang, Xiaoben A1 - David J. Van Horn A1 - Okie, Jordan G. A1 - Heather N. Buelow A1 - Schwartz, Egbert A1 - Colman, Daniel R. A1 - Feeser, Kelli L. A1 - Cristina D. Takacs-Vesbach KW - Antarctica KW - inter-domain response KW - McMurdo Dry Valleys KW - salinity KW - species richness patterns AB -

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.

VL - 26 UR - https://link.springer.com/article/10.1007/s00792-022-01262-3 IS - 1 ER - TY - JOUR T1 - Year‐round and long‐term phytoplankton dynamics in Lake Bonney, a permanently ice‐covered Antarctic lake JF - Journal of Geophysical Research: Biogeosciences Y1 - 2021 A1 - Patriarche, Jeffrey D. A1 - John C. Priscu A1 - Cristina D. Takacs-Vesbach A1 - Winslow, Luke A. A1 - Myers, Krista F. A1 - Heather N. Buelow A1 - Rachael M. Morgan-Kiss A1 - Peter T. Doran KW - algae KW - Antarctic KW - fluorometry KW - ice KW - lakes KW - light KW - profiling KW - winter AB -

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).

VL - 126 UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG005925 IS - 4 JO - J Geophys Res Biogeosci ER - TY - JOUR T1 - Local and Regional Scale Heterogeneity Drive Bacterial Community Diversity and Composition in a Polar Desert JF - Frontiers in Microbiology Y1 - 2018 A1 - Feeser, Kelli L. A1 - David J. Van Horn A1 - Heather N. Buelow A1 - Colman, Daniel R. A1 - McHugh, Theresa A. A1 - Okie, Jordan G. A1 - Schwartz, Egbert A1 - Cristina D. Takacs-Vesbach AB -

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.

VL - 9 UR - https://www.frontiersin.org/article/10.3389/fmicb.2018.01928/full JO - Front. Microbiol. ER - TY - JOUR T1 - Decadal ecosystem response to an anomalous melt season in a polar desert in Antarctica JF - Nature Ecology & Evolution Y1 - 2017 A1 - Michael N. Gooseff A1 - John E. Barrett A1 - Byron Adams A1 - Peter T. Doran A1 - Andrew G Fountain A1 - W. Berry Lyons A1 - Diane M. McKnight A1 - John C. Priscu A1 - Eric R. Sokol A1 - Cristina D. Takacs-Vesbach A1 - Martijn L. Vandegehuchte A1 - Ross A. Virginia A1 - Diana H. Wall VL - 1 UR - https://www.nature.com/articles/s41559-017-0253-0 IS - 9 JO - Nat Ecol Evol ER - TY - JOUR T1 - Decoupled responses of soil bacteria and their invertebrate consumer to warming, but not freeze-thaw cycles, in the Antarctic Dry Valleys JF - Ecology Letters Y1 - 2017 A1 - Matthew Knox A1 - Andriuzzi, Walter S. A1 - Heather N. Buelow A1 - Cristina D. Takacs-Vesbach A1 - Byron Adams A1 - Diana H. Wall AB -

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.

VL - 20 UR - http://onlinelibrary.wiley.com/doi/10.1111/ele.12819/full IS - 10 JO - Ecol Lett ER - TY - JOUR T1 - Niche specialization of bacteria in permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica JF - Environmental Microbiology Y1 - 2017 A1 - Kwon, Miye A1 - Kim, Mincheol A1 - Cristina D. Takacs-Vesbach A1 - Lee, Jaejin A1 - Hong, Soon Gyu A1 - Kim, Sang Jong A1 - John C. Priscu A1 - Kim, Ok-Sun AB -

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.

VL - 19 UR - https://onlinelibrary.wiley.com/doi/pdf/10.1111/1462-2920.13721 IS - 6 JO - Environ Microbiol ER - TY - JOUR T1 - Primary productivity as a control over soil microbial diversity along environmental gradients in a polar desert ecosystem JF - PeerJ Y1 - 2017 A1 - Kevin M. Geyer A1 - Cristina D. Takacs-Vesbach A1 - Michael N. Gooseff A1 - John E. Barrett AB -

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. 

VL - 5 UR - https://peerj.com/articles/3377/ IS - 10 ER - TY - JOUR T1 - Microbial Community Dynamics in Two Polar Extremes: The Lakes of the McMurdo Dry Valleys and the West Antarctic Peninsula Marine Ecosystem JF - BioScience Y1 - 2016 A1 - Bowman, Jeff S. A1 - Trista J. Vick-Majors A1 - Rachael M. Morgan-Kiss A1 - Cristina D. Takacs-Vesbach A1 - Hugh W. Ducklow A1 - John C. Priscu VL - 66 UR - 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 IS - 10 JO - BioScience ER - TY - JOUR T1 - Microbial Community Responses to Increased Water and Organic Matter in the Arid Soils of the McMurdo Dry Valleys, Antarctica JF - Frontiers in Microbiology Y1 - 2016 A1 - Heather N. Buelow A1 - Winter, Ara S. A1 - David J. Van Horn A1 - John E. Barrett A1 - Michael N. Gooseff A1 - Schwartz, Egbert A1 - Cristina D. Takacs-Vesbach VL - 7 UR - http://journal.frontiersin.org/article/10.3389/fmicb.2016.01040 IS - e23484S2237R25e97876e16410550e61217386e14510884660e19953e2527e661032901141 JO - Front. Microbiol. ER - TY - JOUR T1 - Nutrient treatments alter microbial mat colonization in two glacial meltwater streams from the McMurdo Dry Valleys, Antarctica JF - FEMS Microbiology Ecology Y1 - 2016 A1 - Tyler J. Kohler A1 - David J. Van Horn A1 - Darling, Joshua P. A1 - Cristina D. Takacs-Vesbach A1 - Diane M. McKnight ED - Wagner, Dirk AB -

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.

VL - 92 UR - http://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw049 IS - 4 JO - FEMS Microbiology Ecology ER - TY - JOUR T1 - Patterns of bacterial biodiversity in the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica JF - FEMS Microbiology Ecology Y1 - 2016 A1 - David J. Van Horn A1 - Wolf, Caitlin R. A1 - Colman, Daniel R. A1 - Jiang, Xiaoben A1 - Tyler J. Kohler A1 - Diane M. McKnight A1 - Lee F. Stanish A1 - Yazzie, Terrill A1 - Cristina D. Takacs-Vesbach AB -

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.

VL - 92 UR - http://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw148 IS - 10 JO - FEMS Microbiology Ecology ER - TY - JOUR T1 - Niche and metabolic principles explain patterns of diversity and distribution: theory and a case study with soil bacterial communities JF - Proceedings of the Royal Society B: Biological Sciences Y1 - 2015 A1 - Okie, Jordan G. A1 - David J. Van Horn A1 - Storch, David A1 - John E. Barrett A1 - Michael N. Gooseff A1 - Kopsova, Lenka A1 - Cristina D. Takacs-Vesbach AB -

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.

 

 

VL - 282 UR - http://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2014.2630 IS - 1809 JO - Proc. R. Soc. B ER - TY - JOUR T1 - Autonomous Year-Round Sampling and Sensing to Explore the Physical and Biological Habitability of Permanently Ice-Covered Antarctic Lakes JF - Marine Technology Society Journal Y1 - 2014 A1 - Winslow, Luke A. A1 - Hilary A. Dugan A1 - Heather N. Buelow A1 - Cronin, Kyle D. A1 - John C. Priscu A1 - Cristina D. Takacs-Vesbach A1 - Peter T. Doran AB -

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.

VL - 48 UR - 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 IS - 5 JO - mar technol soc j ER - TY - JOUR T1 - Bacterial community composition of divergent soil habitats from a polar desert. JF - FEMS Microbiology Ecology Y1 - 2014 A1 - Kevin M. Geyer A1 - Adam E. Altrichter A1 - Cristina D. Takacs-Vesbach A1 - Michael N. Gooseff A1 - John E. Barrett AB - 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 VL - 89 IS - 2 ER - TY - JOUR T1 - Characterization of Growing Bacterial Populations in McMurdo Dry Valley Soils through Stable Isotope Probing with 18O-water. JF - FEMS Microbiology Ecology. Y1 - 2014 A1 - Schwartz, E. A1 - David J. Van Horn A1 - Heather N. Buelow A1 - Michael N. Gooseff A1 - John E. Barrett A1 - Cristina D. Takacs-Vesbach A1 - Okie, J.G. AB - 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. VL - 89 IS - 2 ER - TY - JOUR T1 - Soil microbial responses to increased moisture and organic resources along a salinity gradient in a polar desert. JF - Applied and Environmental Microbiology. Y1 - 2014 A1 - David J. Van Horn A1 - Okie, J.G. A1 - Heather N. Buelow A1 - Michael N. Gooseff A1 - John E. Barrett A1 - Cristina D. Takacs-Vesbach AB - 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. VL - 80 IS - 10 ER - TY - JOUR T1 - Environmental controls over bacterial communities in polar desert soils JF - Ecosphere Y1 - 2013 A1 - Kevin M. Geyer A1 - Adam E. Altrichter A1 - David J. Van Horn A1 - Cristina D. Takacs-Vesbach A1 - Michael N. Gooseff A1 - John E. Barrett VL - 4 IS - 10 ER - TY - JOUR T1 - Factors Controlling Soil Microbial Biomass and Bacterial Diversity and Community Composition in a Cold Desert Ecosystem: Role of Geographic Scale JF - PLoS ONE Y1 - 2013 A1 - David J. Van Horn A1 - Van Horn, M. Lee A1 - John E. Barrett A1 - Michael N. Gooseff A1 - Adam E. Altrichter A1 - Kevin M. Geyer A1 - Lydia H. Zeglin A1 - Cristina D. Takacs-Vesbach VL - 8 UR - http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0066103 IS - 6 ER - TY - JOUR T1 - Seasonal controls on snow distribution and aerial ablation at the snow-patch and landscape scales, McMurdo Dry Valleys, Antarctica JF - The Cryosphere Y1 - 2013 A1 - Eveland, Jeffery A1 - Michael N. Gooseff A1 - Lampkin, Derrick J. A1 - John E. Barrett A1 - Cristina D. Takacs-Vesbach VL - 7 UR - http://www.the-cryosphere.net/7/917/2013/tc-7-917-2013.html IS - 3 ER - TY - JOUR T1 - Spatial and temporal patterns of snow accumulation and aerial ablation across the McMurdo Dry Valleys, Antarctica JF - Hydrological Processes Y1 - 2013 A1 - Eveland, Jeffery A1 - Michael N. Gooseff A1 - Lampkin, Derrick J. A1 - John E. Barrett A1 - Cristina D. Takacs-Vesbach VL - 27 UR - http://onlinelibrary.wiley.com/doi/10.1002/hyp.9407/pdf IS - 20 ER - TY - JOUR T1 - Bacterial Community Structure Along Moisture Gradients in the Parafluvial Sediments of Two Ephemeral Desert Streams JF - Microbial Ecology Y1 - 2011 A1 - Lydia H. Zeglin A1 - Clifford N. Dahm A1 - John E. Barrett A1 - Michael N. Gooseff A1 - Shannon K. Fitpatrick A1 - Cristina D. Takacs-Vesbach VL - 61 UR - http://www.springerlink.com/content/r83j53334v5n505w/ IS - 3 ER - TY - CHAP T1 - Factors promoting microbial diversity in the McMurdo Dry Valleys T2 - Life in Antarctic Deserts and other Cold Dry Environments: Astrobiological Analogues Y1 - 2010 A1 - Cristina D. Takacs-Vesbach A1 - Lydia H. Zeglin A1 - Michael N. Gooseff A1 - John E. Barrett A1 - John C. Priscu JF - Life in Antarctic Deserts and other Cold Dry Environments: Astrobiological Analogues T3 - Cambridge Astrobiology PB - Cambridge University Press VL - 5 SN - 9780521889193 UR - http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511712258&cid=CBO9780511712258A015 ER - TY - CHAP T1 - The legacy of aqueous environments on soils of the McMurdo Dry Valleys: contexts for future exploration of martian soils T2 - Life in Antarctic Deserts and other Cold Dry Environments Y1 - 2010 A1 - John E. Barrett A1 - Poage, M A1 - Michael N. Gooseff A1 - Cristina D. Takacs-Vesbach JF - Life in Antarctic Deserts and other Cold Dry Environments PB - Cambridge University Press CY - Cambridge VL - 5 SN - 9780521889193 UR - http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511712258&cid=CBO9780511712258A010 ER - TY - BOOK T1 - Life in Antarctic Deserts and Other Cold Environments T2 - Astrobiological Analogs Y1 - 2010 A1 - Peter T. Doran A1 - W. Berry Lyons A1 - Diane M. McKnight ED - Diane M. McKnight ED - Michael N. Gooseff ED - Cristina D. Takacs-Vesbach ED - Jill A. Mikucki ED - Martyn Tranter ED - Sun, Henry J KW - Planetary Science JF - Astrobiological Analogs PB - Cambridge University Press. CY - Cambridge VL - 5 SN - 9780511712258 UR - http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511712258 ER - TY - JOUR T1 - Hydrologic characteristics of lake- and stream-side riparian wetted margins in the McMurdo Dry Valleys, Antarctica JF - Hydrological Processes Y1 - 2009 A1 - Northcott, M A1 - Michael N. Gooseff A1 - John E. Barrett A1 - Lydia H. Zeglin A1 - Cristina D. Takacs-Vesbach A1 - Humphrey, J VL - 23 ER - TY - JOUR T1 - Landscape Distribution of Microbial Activity in the McMurdo Dry Valleys: Linked Biotic Processes, Hydrology, and Geochemistry in a Cold Desert Ecosystem JF - Ecosystems Y1 - 2009 A1 - Lydia H. Zeglin A1 - Sinsabaugh, R A1 - John E. Barrett A1 - Michael N. Gooseff A1 - Cristina D. Takacs-Vesbach VL - 12 ER - TY - JOUR T1 - Spatial variation in soil active-layer geochemistry across hydrologic margins in polar desert ecosystems. JF - Hydrology and Earth System Sciences Y1 - 2009 A1 - John E. Barrett A1 - Michael N. Gooseff A1 - Cristina D. Takacs-Vesbach VL - 13 ER - TY - JOUR T1 - Thermal Characterisation of Active Layer Across a Soil Moisture Gradient in the McMurdo Dry Valleys, Antarctica JF - Permafrost and Periglacial Processes Y1 - 2009 A1 - Ikard, S A1 - Michael N. Gooseff A1 - John E. Barrett A1 - Cristina D. Takacs-Vesbach VL - 20 ER - TY - THES T1 - Microbial diversity and function at aquatic- terrestrial interfaces in desert ecosystems. T2 - Department of Biology Y1 - 2008 A1 - Lydia H. Zeglin JF - Department of Biology PB - University of New Mexico VL - Ph.D. ER - TY - JOUR T1 - Stoichiometry of soil enzyme activity at global scale. JF - Ecology Letters Y1 - 2008 A1 - Sinsabaugh, R A1 - Gallo, M A1 - Gartner, T A1 - Hobbie, S A1 - Holland, K A1 - Keeler, B A1 - Powers, J A1 - Stursova, M A1 - Cristina D. Takacs-Vesbach A1 - Waldrop, M A1 - Wallenstein, M A1 - Lauber, M A1 - Zak, D A1 - Lydia H. Zeglin A1 - Weintraub, M A1 - Ahmed, B A1 - Allison, S A1 - Crenshaw, C A1 - Contosta, A A1 - Cusack, D A1 - Frey, S VL - 11 ER - TY - JOUR T1 - Controls on the spatial dimensions of wetted hydrologic margins of two antarctic lakes JF - Vadose Zone Journal Y1 - 2007 A1 - Michael N. Gooseff A1 - John E. Barrett A1 - Melissa L. Northcott A1 - D. Brad Bate A1 - Kenneth R. Hill A1 - Lydia H. Zeglin A1 - Bobb, M A1 - Cristina D. Takacs-Vesbach VL - 6 IS - 4 ER - TY - THES T1 - Spatial Patterns of Bacterial Diversity in Cold Desert Riparian Zones. Y1 - 2006 A1 - Bobb, M PB - University of New Mexico VL - B.S. ER - TY - JOUR T1 - Bacterial dissolved organic carbon demand in antarctic dry valley lakes JF - Limnology and Oceanography Y1 - 2001 A1 - Cristina D. Takacs-Vesbach A1 - John C. Priscu A1 - Diane M. McKnight KW - Biggie VL - 46 UR - http://www.jstor.org/stable/2671031 IS - 7 ER - TY - JOUR T1 - Carbon transformations in a perennially ice-covered Antarctic lake Y1 - 1999 A1 - John C. Priscu A1 - Craig F. Wolf A1 - Cristina D. Takacs-Vesbach A1 - Christian H. Fritsen A1 - Johanna Laybourn-Parry A1 - Emily C. Roberts A1 - Birgit Sattl ER - TY - THES T1 - Factors Affecting the Distribution and Dynamics of Bacterioplankton Biomass and Diversity in Taylor Valley Lakes, Antarctica Y1 - 1999 A1 - Cristina D. Takacs-Vesbach PB - Montana State University VL - Ph.D. ER - TY - JOUR T1 - Geomicrobiology of sub-glacial ice above Vostok Station JF - Science Y1 - 1999 A1 - John C. Priscu A1 - Edward E. Adams A1 - W. Berry Lyons A1 - Mary A. Voytek A1 - David W. Mogk A1 - Robert L. Brown A1 - Christopher P. McKay A1 - Cristina D. Takacs-Vesbach A1 - Kathleen A. Welch A1 - Craig F. Wolf A1 - Julie D. Kirshtein A1 - Recep Avci VL - 286 IS - 5447 ER - TY - JOUR T1 - Bacterioplankton dynamics in the McMurdo Dry Valley lakes, Antarctica: Production and biomass loss over four seasons JF - Microbial Ecology Y1 - 1998 A1 - Cristina D. Takacs-Vesbach A1 - John C. Priscu VL - 36 IS - 3 ER - TY - JOUR T1 - The role of phytoplankton extracellular release in bacterioplankton growth of Taylor Valley Lakes, Antarctica JF - Antarctic Journal of the United States - 1996 Review Issue (NSF 98-28) Y1 - 1998 A1 - Cristina D. Takacs-Vesbach A1 - John C. Priscu VL - 31 IS - 2 ER - TY - JOUR T1 - Bacterial growth in Antarctic lakes: The role of phytoplankton extracellular release JF - Bacterial growth in Antarctic lakes: The role of phytoplankton extracellular Y1 - 1996 A1 - Cristina D. Takacs-Vesbach A1 - John C. Priscu ER - TY - JOUR T1 - Responses of bacterial growth to inorganic and organic nutrient enrichment in the lakes of the dry valleys, Antarctica JF - Antarctic Journal of the US Y1 - 1995 A1 - Cristina D. Takacs-Vesbach A1 - John C. Priscu VL - 30 ER -