Browsing by Author "Vick-Majors, Trista Juliana"

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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.