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Item Microbially mediated biogeochemical cycles in polar ice covered lakes(Montana State University - Bozeman, College of Agriculture, 2016) Michaud, Alexander Bryce Olson; Chairperson, Graduate Committee: John C. Priscu; Trista J. Vick-Majors, Mark L. Skidmore and John C. Priscu were co-authors of the article, 'Field testing of a clean, hot water drill used for access to subglacial aquatic environments' submitted to the journal 'Antarctic science' which is contained within this dissertation.; Mark L. Skidmore, Andrew C. Mitchell, Trista J. Vick-Majors, John C. Priscu, Carlo Barbante, Clara Turetta and Will vanGelder were co-authors of the article, 'Solute sources and geochemical processes in subglacial Lake Whillans, west Antarctica' in the journal 'Geology' which is contained within this dissertation.; John E. Dore, Trista J. Vick-Majors, Mark L. Skidmore and John C. Priscu were co-authors of the article, 'Microbial methane transformations beneath the west Antarctic ice sheet' submitted to the journal 'Science' which is contained within this dissertation.; This dissertation contains one article of which Alexander Bryce Olson Michaud is not the main author.Lakes are important sites for globally-relevant biogeochemical cycles mediated by microorganisms. In the Arctic, seasonally ice covered thermokarst lakes are a large component in Earth's carbon cycle due to their methane emissions from organic carbon degradation. In the Antarctic, over 400 unexplored lakes exist beneath the Antarctic ice sheet with unknown biogeochemical contributions to the Earth system. This dissertation seeks to investigate the biogeochemical role of microorganisms in the lake habitat and how they interact with the seasonal and permanent ice covers of lakes in polar environments. Microbiologically clean hot water drilling was used to access a subglacial lake beneath Antarctica's ice to collect, for the first time, intact sediment and water samples. Laboratory experiments on Arctic and Antarctic, seasonally and perennially, respectively, ice covered lakes were used to investigate the impact of lake ice freezing regimes on microorganisms. My results show that subglacial lake sediments beneath the West Antarctic Ice Sheet contain solute ratios that suggest relict marine sediments were deposited during previous interglacial periods. Microbial activity overprints the marine geochemical signature to produce fluxes of ions into the Subglacial Lake Whillans water column, which ultimately drains to the Southern Ocean. Microbial activity in Subglacial Lake Whillans is partially fueled by biologically-formed methane diffusing from below our deepest collected (~38 cm) subglacial sediment samples. The ice above Subglacial Lake Whillans appears to be an important source of molecular oxygen for microorganisms to drive oxidative physiologies. My experimental evidence shows microorganisms incorporate into lake ice cover to, potentially, avoid increasing stressors from progressive lake ice freezing. Taken together, the results from this dissertation reinforce the hypothesis that subglacial environments beneath the Antarctic ice sheet are habitats for life. Further, the microorganisms in subglacial lakes participate in globally-relevant biogeochemical cycles. Here, I extend the extent of the biosphere and show sediments at the base of ice sheets are an active component of the Earth system.Item Biogeochemical processes in Antarctic aquatic environments: linkages and limitations(Montana State University - Bozeman, College of Agriculture, 2016) Vick-Majors, Trista Juliana; Chairperson, Graduate Committee: John C. Priscu; John C. Priscu and Linda Amaral-Zettler were co-authors of the article, 'Modular community structure suggests metabolic plasticity during the transition to polar night in ice-covered antarctic lakes' in the journal 'The ISME journal ' which is contained within this dissertation.; John C. Priscu was a co-author of the article, 'Partitioning of inorganic carbon-fixation in permanently ice-covered Antarctic lakes' submitted to the journal 'Microbial ecology' which is contained within this dissertation.; Amanda Achberger, Pamela Santibanez, John E. Dore, Timothy Hodson, Alexander B. Michaud, Brent C. Christner, Jill Mikucki, Mark L. Skidmore, Ross Powell, W. Peyton Adkins, Carlo Barbante, Andrew Mitchell, Reed Scherer and John C. Priscu were co-authors of the article, 'Biogeochemistry and microbial diversity in the marine cavity beneath the McMurdo Ice Shelf, Antarctica' submitted to the journal 'Limnology and oceanography' which is contained within this dissertation.; Alexander B. Michaud and John C. Priscu were co-authors of the article, 'Subglacial carbon and nutrient fluxes fertilize the Southern Ocean under the Ross Ice Shelf' submitted to the journal 'Nature' which is contained within this dissertation.; This dissertation contains two articles of which Trista Juliana Vick-Majors is not the main author.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.Item Factors influecing the abundance of microorganisms in icy environments(Montana State University - Bozeman, College of Agriculture, 2016) Santibanez-Avila, Pamela Alejandra; Chairperson, Graduate Committee: John C. Priscu; Joseph R. McConnell and John C. Priscu were co-authors of the article, 'A flow cytometric method to measure prokaryotic records in ice cores: an example from the Wais Divide drilling site' submitted to the journal 'Journal of glaciology: instruments and methods' which is contained within this dissertation.; Mark Greenwood, Joseph R. McConnell and John C. Priscu were co-authors of the article, 'Prokaryotic concentration changes between the last glacial maximum and the early Holocene from the Wais Divide ice core' submitted to the journal 'Quaternary science reviews' which is contained within this dissertation.; Alexander B. Michaud, Trista J. Vick-Majors, Juliana D'Andrilli, Amy Chiuchiolo and John Priscu were co-authors of the article, 'Bacterial response to progressive freezing in perennially and seasonally ice-covered lakes' submitted to the journal 'Journal of geophysical research (JGR) biogeosciences' which is contained within this dissertation.Microbial life can easily live without us; we, however, cannot survive without the global catalysis and environmental transformations it provides' (Falkowski et al., 2008). Despite of the key role of microbes on Earth, microbial community characteristics are not explicitly part of climate models because our understanding of their responses to long-term environmental and climatic processes is limited. In this study, I developed a Flow Cytometric protocol to access a long-term record of non-photosynthetic prokaryotic cell concentration archived in the West Antarctic Ice-Sheet (WAIS; chapter 2). The WD ice core was retrieved between 2009 and 2011 to a depth of 3,405 m, extending back to 68,000 before 1950. Once a 17,400 year-record of prokaryotic cell concentration was acquired, I investigated its temporal variability and patterns, determined the potential sources of prokaryotic cells between the Last Glacial Maximum and the early Holocene, and assessed the environmental factors that might have the largest influence on the prokaryotic response (chapter 3). The observed patterns in the prokaryotic record are linked to large-scale controls of the Southern Ocean and West Antarctica Ice-Sheet. The main research findings presented here about the first prokaryotic record are: (i) airborne prokaryotic cell concentration does respond to long-term climatic and environmental processes, (ii) the processes of deglaciation, sea level rise and sea-ice fluctuation were key; the abundance of prokaryotic cells covariate with ssNa and black carbon, and (iii) the prokaryotic cell record variate on millennial time scale with cycles of 1,490-years. In addition, I studied 'congelation ice' (i.e., ice forms as liquid water freezes) from ice-covered lakes to understand prokaryotic cell segregation between liquid and solid phases during the physical freezing process. Five mesocosm experiments were designed to understand prokaryotic responses to the progressive freezing in concert with field observations from ice-covered lakes from Barrow, Alaska. As a result of this last study (chapter 4), I concluded that prokaryotic cells are preferentially incorporated in the ice with segregation coefficients (K eff) between 0.8 - 4.4, which are higher than for major ions. Prokaryotic cells avoid rejection more effectively from the ice matrix.Item Effects of toxaphene upon plankton and aquatic invertebrates in North Dakota lakes(Montana State University - Bozeman, College of Letters & Science, 1962) Needham, Robert G.Item Precambrian geology of Lake Plateau, Beartooth Mountains, Montana(Montana State University - Bozeman, College of Letters & Science, 1987) Richmond, Douglas P.Item Biological cycling of nitrogen in a Rocky Mountain alpine lake, with emphasis on the physiological and ecological effects of acidification(Montana State University - Bozeman, College of Letters & Science, 1989) Angelo, Robert Thomas