@article {4150, title = {Differential incorporation of bacteria, organic matter, and inorganic ions into lake ice during ice formation}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {124}, year = {2019}, month = {02/2019}, pages = {585 - 600}, abstract = {

The segregation of bacteria, inorganic solutes, and total organic carbon between liquid water and ice during winter ice formation on lakes can significantly influence the concentration and survival of microorganisms in icy systems, and their roles in biogeochemical processes. Our study quantifies the distributions of bacteria and solutes between liquid and solid water phases during progressive freezing. We simulated lake ice formation in mesocosm experiments using water from perennially (Antarctica) and seasonally (Alaska and Montana, USA) ice covered lakes. We then computed concentration factors and effective segregation coefficients, which are parameters describing the incorporation of bacteria and solutes into ice. Experimental results revealed that, contrary to major ions, bacteria were readily incorporated into ice and did not concentrate in the liquid phase. The organic matter incorporated into the ice was labile, amino acid-like material, differing from the humic-like compounds that remained in the liquid phase. Results from a control mesocosm experiment (dead bacterial cells) indicated that viability of bacterial cells did not influence the incorporation of free bacterial cells into ice, but did have a role in the formation and incorporation of bacterial aggregates. Together, these findings demonstrate that bacteria, unlike other solutes, were preferentially incorporated into lake-ice during our freezing experiments, a process controlled mainly by the initial solute concentration of the liquid water source, regardless of cell viability.

}, keywords = {LTER-MCM}, doi = {10.1029/2018JG004825}, url = {https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JG004825}, author = {Santib{\'a}{\~n}ez, Pamela and Alexander B. Michaud and Trista J. Vick-Majors and D{\textquoteright}Andrilli, Juliana and Amy Chiuchiolo and Hand, Kevin P. and John C. Priscu} } @article {4176, title = {Inorganic carbon fixation in ice-covered lakes of the McMurdo Dry Valleys}, journal = {Antarctic Science}, volume = {72}, year = {2019}, month = {04/2019}, abstract = {

Inorganic carbon fixation, usually mediated by photosynthetic microorganisms, is considered to form the base of the food chain in aquatic ecosystems. In high-latitude lakes, lack of sunlight owing to seasonal solar radiation limits the activity of photosynthetic plankton during the polar winter, causing respiration-driven demand for carbon to exceed supply. Here, we show that inorganic carbon fixation in the dark, driven by organisms that gain energy from chemical reactions rather than sunlight (chemolithoautotrophs), provides a significant influx of fixed carbon to two permanently ice-covered lakes (Fryxell and East Bonney). Fryxell, which has higher biomass per unit volume of water, had higher rates of inorganic dark carbon fixation by chemolithoautotrophs than East Bonney (trophogenic zone average 1.0 \µg C l\−1 d\−1\ vs 0.08 \µg C l\−1 d\−1, respectively). This contribution from dark carbon fixation was partly due to the activity of ammonia oxidizers, which are present in both lakes. Despite the potential importance of new carbon input by chemolithoautotrophic activity, both lakes remain net heterotrophic, with respiratory demand for carbon exceeding supply. Dark carbon fixation increased the ratio of new carbon supply to respiratory demand from 0.16 to 0.47 in Fryxell, and from 0.14 to 0.22 in East Bonney.

}, keywords = {LTER-MCM, ammonia oxidation, carbon budget, chemoautotrophy, chemolithoautotrophy}, issn = {0954-1020}, doi = {10.1017/S0954102019000075}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/inorganic-carbon-fixation-in-icecovered-lakes-of-the-mcmurdo-dry-valleys/4B5CA9E91C85B307EFDA69F8D7B5BFD9}, author = {Trista J. Vick-Majors and John C. Priscu} } @phdthesis {4034, title = {Biogeochemical processes in Antarctic aquatic environments: Linkages and limitations}, volume = {Ph.D.}, year = {2016}, pages = {228}, school = {Montana State University}, type = {doctoral}, abstract = {

The research presented in this dissertation focused on microbially-mediated biogeochemical processes and microbial ecology in Antarctic lakes and seawater. The major objective of my research was to examine the impact of environmentally imposed energetic constraints on nutrient cycling in mirobially-dominated systems. I used three ice-covered aquatic environments as natural laboratories for my investigations. The permanently ice-covered lakes of the McMurdo Dry Valleys (MCM) are located in Victoria Land, East Antarctica. The MCM have been studied intensively as part of the McMurdo Long Term Ecological Research Project since 1993. My work built on the extensive MCM dataset via high-throughput DNA sequencing to examine microbial communities from all three domains of life during the transition to winter, and by quantifying rates of dark inorganic carbon-fixation. This worked showed the importance of flexible metabolisms in the microbial ecosystems of the MCM lakes. The ocean beneath the McMurdo Ice Shelf (MIS) is the gateway between the Ross Sea and the dark ocean of the Ross Ice Shelf cavity. The area supports a biological carbon pump that is important in ocean biogeochemistry. Ice shelves around Antarctica are under threat of collapse, but little is known about the ecosystems beneath them. My work used a combination of biogeochemical measurements and assessment of microbial community structure to characterize the ecosystem beneath the MIS and its connections to the open ocean. The data showed the importance of nutrients advected from open water to the MIS cavity and projected an organic carbon deficit farther from the ice shelf edge. Subglacial Lake Whillans lies 800 m beneath the surface of the West Antarctic Ice Sheet near the end of a hydrological continuum that terminates in the ocean beneath the Ross Ice Shelf. Primarily through the use of biogeochemical rate measurements and determinations of organic matter quantity and quality, this work established the presence of an active microbial ecosystem in the subglacial lake, and estimated the annual subglacial flux of carbon and nutrients to the ocean under the ice shelf. Together, these projects show the importance of microbial activity in regional biogeochemical processes and of metabolic flexibility under energy-limited conditions.

}, keywords = {LTER-MCM}, url = {https://search.proquest.com/openview/9118336399cac113f488d77fb07bce26/1?pq-origsite=gscholar\&cbl=18750\&diss=y}, author = {Trista J. Vick-Majors} } @article {3717, title = {Biogeochemistry and microbial diversity in the marine cavity beneath the McMurdo Ice Shelf, Antarctica}, journal = {Limnology and Oceanography}, volume = {61}, year = {2016}, month = {11/2015}, pages = {572 - 586}, keywords = {LTER-MCM}, doi = {10.1002/lno.v61.210.1002/lno.10234}, url = {http://doi.wiley.com/10.1002/lno.v61.2http://doi.wiley.com/10.1002/lno.10234http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2Flno.10234}, author = {Trista J. Vick-Majors and Achberger, Amanda and Santib{\'a}{\~n}ez, Pamela and John E. Dore and Hodson, Timothy and Alexander B. Michaud and Brent C. Christner and Jill Ai, Jill. Mikucki and Skidmore, Mark L. and Powell, Ross and Adkins, W. Peyton and Barbante, Carlo and Mitchell, Andrew and Scherer, Reed and John C. Priscu} } @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 {4013, title = {Microbial Community Structure of Subglacial Lake Whillans, West Antarctica}, journal = {Frontiers in Microbiology}, volume = {7}, year = {2016}, month = {Oct-09-2017}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2016.01457}, url = {http://journal.frontiersin.org/Article/10.3389/fmicb.2016.01457/abstract}, author = {Achberger, Amanda and Brent C. Christner and Alexander B. Michaud and John C. Priscu and Skidmore, Mark L. and Trista J. Vick-Majors} } @article {4033, title = {Physiological Ecology of Microorganisms in Subglacial Lake Whillans}, journal = {Frontiers in Microbiology}, volume = {7}, year = {2016}, month = {Mar-10-2018}, keywords = {LTER-MCM}, doi = {10.3389/fmicb.2016.01705}, url = {http://journal.frontiersin.org/article/10.3389/fmicb.2016.01705/fullhttp://journal.frontiersin.org/article/10.3389/fmicb.2016.01705/full}, author = {Trista J. Vick-Majors and Mitchell, Andrew and Achberger, Amanda and Brent C. Christner and John E. Dore and Alexander B. Michaud and Jill A. Mikucki and Purcell, Alicia M. and Skidmore, Mark L. and John C. Priscu} } @article {1056, title = {Ciliate diversity, community structure and novel taxa in lakes of the McMurdo Dry Valleys, Antarctica}, journal = {Biological Bulleting}, volume = {227}, year = {2014}, month = {10/2014}, pages = {175-190}, chapter = {175}, abstract = {We report an in-depth survey of next-generation DNA sequencing of ciliate diversity and community structure in two permanently ice-covered McMurdo Dry Valley lakes during the austral summer and autumn (November 2007 and March 2008). We tested hypotheses on the relationship between species richness and environmental conditions including environmental extremes, nutrient status, and day length. On the basis of the unique environment that exists in these high-latitude lakes, we expected that novel taxa would be present. Alpha diversity analyses showed that extreme conditions-that is, high salinity, low oxygen, and extreme changes in day length-did not impact ciliate richness; however, ciliate richness was 30\% higher in samples with higher dissolved organic matter. Beta diversity analyses revealed that ciliate communities clustered by dissolved oxygen, depth, and salinity, but not by season (i.e., day length). The permutational analysis of variance test indicated that depth, dissolved oxygen, and salinity had significant influences on the ciliate community for the abundance matrices of resampled data, while lake and season were not significant. This result suggests that the vertical trends in dissolved oxygen concentration and salinity may play a critical role in structuring ciliate communities. A PCR-based strategy capitalizing on divergent eukaryotic V9 hypervariable region ribosomal RNA gene targets unveiled two new genera in these lakes. A novel taxon belonging to an unknown class most closely related to Cryptocaryon irritans was also inferred from separate gene phylogenies.}, keywords = {LTER-MCM}, author = {Yuan, Xu and Trista J. Vick-Majors and Rachael M. Morgan-Kiss and John C. Priscu and Linda A. Amaral-Zettler} } @article {1085, title = {Modular community structure suggests metabolic plasticity during the transition to polar night in ice-covered Antarctic lakes}, journal = {The ISME Journal}, year = {2014}, month = {10/2013}, keywords = {LTER-MCM}, doi = {10.1038/ismej.2013.190}, url = {http://www.nature.com/ismej/journal/vaop/ncurrent/full/ismej2013190a.html}, author = {Trista J. Vick-Majors and John C. Priscu and Linda A. Amaral-Zettler} } @article {3527, title = {Bacterioplankton productivity in lakes of the Taylor Valley, Antarctica, during the polar night transition}, journal = {Aquatic Microbial Ecology}, volume = {68}, year = {2012}, month = {12/2013}, pages = {77 - 90}, abstract = {

Research on the lakes of the McMurdo Dry Valleys, Antarctica, is typically conducted during the period of 24 h sunlight (October to January) when logistical support is readily available. As part of the International Polar Year initiative, we obtained logistical support to study microbial dynamics in the permanently ice-covered lakes of the Taylor Valley during the transition from 24 h of sunlight to the complete darkness of the polar night (mid-April). Our study focused on the perennially ice-covered lakes Fryxell (FRX), East Lobe Bonney (ELB), and West Lobe Bonney (WLB), all of which are chemically stratified and have food webs dominated by microorganisms. Depth-integrated bacterioplankton productivity (BP; leucine incorporation [Leu] and thymidine incorporation [TdR]) in the lakes ranged from 1.2 to 3.4 mg C m\−2\ d\−1. Overall, summer was characterized by relatively high rates of BP and photoautotrophic primary productivity. Rapid decreases in photosynthetically active radiation marked a subsequent transition period, which was characterized by variable cell counts and decreasing Leu:TdR ratios (ratios \>1 signify a physiological shift from growth to maintenance mode). Finally, cell counts decreased and Leu:TdR increased by as much as 280\% during the fall, revealing a distinct change in the physiological state of the bacterioplankton as light-mediated primary productivity ceased. Our data reveal that the shift in physiological state may result from a switch from contemporary phytoplankton-excreted carbon to other sources of dissolved organic carbon, which can support the bacterioplankton populations through the winter.

}, keywords = {LTER-MCM}, issn = {0948-3055}, doi = {10.3354/ame01604}, url = {http://www.int-res.com/abstracts/ame/v68/n1/p77-90}, author = {Trista J. Vick-Majors and John C. Priscu} } @article {1113, title = {Microbial dynamics and flagellate grazing during transition to winter in Lakes Hoare and Bonney, Antarctica}, journal = {FEMS Microbiology Ecology}, volume = {82}, year = {2012}, month = {11/2012}, pages = {449 - 458}, keywords = {LTER-MCM}, doi = {10.1111/j.1574-6941.2012.01423.x}, url = {http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2012.01423.x/full}, author = {Jill Thurman and Jacqueline Parry and Philip J. Hill and John C. Priscu and Trista J. Vick-Majors and Amy Chiuchiolo and Johanna Laybourn-Parry} } @mastersthesis {4194, title = {Bacterioplakton dynamics in stratified lakes of the Taylor Valley, Antarctica during the transition to polar night}, volume = {M.S.}, year = {2010}, month = {2010}, pages = {83}, school = {Montana State University}, type = {masters}, address = {Bozeman, MT}, abstract = {

Limnological research on the lakes of the McMurdo Dry Valleys (MCM), Antarctica, is typically carried out during the austral spring-summer (October January) when logistical support is readily available; the current study marks the first sampling effort during the summer-fall transition (January-April). Sampling during the darkness of winter is logistically difficult and expensive, and my study is an important step towards understanding the year-round ecology of the dry valley lakes. Bacterial productivity, measured as protein synthesis and DNA replication, and bacterial cell numbers were measured 10-12 times between October 2007 and April 2008 in Lakes Fryxell (FRX) and the east and west lobes of Lake Bonney (ELB and WLB). Lake Fryxell was the most productive (bacterial) lake on average by an order of magnitude (average = 1.24 mg C m -\²d -\¹; range = 0.00 to 3.29 mg C m -\²d -\¹), and also contained the greatest bacterial biomass (~10 $^{6}$ cells ml -\¹) by 1 to 3 orders of magnitude. If bacterial production were directly linked to organic carbon supplied by photosynthetic primary production, a decrease in bacterial production would be expected during the sunset; however, no statistically significant change in bacterial production (a=0.05) was observed during the summer-fall transition. A distinct decoupling of bacterial protein production and DNA replication was detected in FRX and ELB of the lakes as the season progressed, and was present in WLB throughout the season, indicating either a shift towards a lower growth-rate in response to decreasing light or nutrient supply, or a mechanism for dealing with the perennially low temperatures, low light, and nutrient poor conditions in the lakes. Overall, it appears that bacterial communities remain active during the darkness of winter, when the lakes enter a period of \"net heterotrophy\", which cannot be sustained unless the carbon balance of the TV lakes is reset by climatic events.

}, keywords = {LTER-MCM}, url = {https://scholarworks.montana.edu/xmlui/handle/1/2477}, author = {Trista J. Vick-Majors and John C. Priscu} }