<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>32</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Trista J. Vick-Majors</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Biogeochemical processes in Antarctic aquatic environments: Linkages and limitations</style></title><secondary-title><style face="normal" font="default" size="100%">Land Resources and Environmental Sciences</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2016</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://search.proquest.com/openview/9118336399cac113f488d77fb07bce26/1?pq-origsite=gscholar&amp;cbl=18750&amp;diss=y</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Montana State University</style></publisher><volume><style face="normal" font="default" size="100%">Ph.D.</style></volume><pages><style face="normal" font="default" size="100%">228</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;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.&lt;/p&gt;</style></abstract><work-type><style face="normal" font="default" size="100%">doctoral</style></work-type></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Trista J. Vick-Majors</style></author><author><style face="normal" font="default" size="100%">Achberger, Amanda</style></author><author><style face="normal" font="default" size="100%">Santibáñez, Pamela</style></author><author><style face="normal" font="default" size="100%">John E. Dore</style></author><author><style face="normal" font="default" size="100%">Hodson, Timothy</style></author><author><style face="normal" font="default" size="100%">Alexander B. Michaud</style></author><author><style face="normal" font="default" size="100%">Brent C. Christner</style></author><author><style face="normal" font="default" size="100%">Jill Ai, Jill. Mikucki</style></author><author><style face="normal" font="default" size="100%">Skidmore, Mark L.</style></author><author><style face="normal" font="default" size="100%">Powell, Ross</style></author><author><style face="normal" font="default" size="100%">Adkins, W. Peyton</style></author><author><style face="normal" font="default" size="100%">Barbante, Carlo</style></author><author><style face="normal" font="default" size="100%">Mitchell, Andrew</style></author><author><style face="normal" font="default" size="100%">Scherer, Reed</style></author><author><style face="normal" font="default" size="100%">John C. Priscu</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Biogeochemistry and microbial diversity in the marine cavity beneath the McMurdo Ice Shelf, Antarctica</style></title><secondary-title><style face="normal" font="default" size="100%">Limnology and Oceanography</style></secondary-title><short-title><style face="normal" font="default" size="100%">Limnol. Oceanogr.</style></short-title></titles><dates><year><style  face="normal" font="default" size="100%">2016</style></year><pub-dates><date><style  face="normal" font="default" size="100%">11/2015</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">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</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">61</style></volume><pages><style face="normal" font="default" size="100%">572 - 586</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">2</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Trista J. Vick-Majors</style></author><author><style face="normal" font="default" size="100%">John C. Priscu</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Bacterioplankton productivity in lakes of the Taylor Valley, Antarctica, during the polar night transition</style></title><secondary-title><style face="normal" font="default" size="100%">Aquatic Microbial Ecology</style></secondary-title><short-title><style face="normal" font="default" size="100%">Aquat. Microb. Ecol.</style></short-title></titles><dates><year><style  face="normal" font="default" size="100%">2012</style></year><pub-dates><date><style  face="normal" font="default" size="100%">12/2013</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.int-res.com/abstracts/ame/v68/n1/p77-90</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">68</style></volume><pages><style face="normal" font="default" size="100%">77 - 90</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;&lt;span style=&quot;color: rgb(51, 51, 51); font-family: Arial, Helvetica, Geneva, Helvetica, sans-serif; font-size: 12px; line-height: 18px; text-align: justify;&quot;&gt;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&lt;/span&gt;&lt;span style=&quot;font-size: smaller; position: relative; bottom: 0.4em; color: rgb(51, 51, 51); font-family: Arial, Helvetica, Geneva, Helvetica, sans-serif; line-height: 18px; text-align: justify;&quot;&gt;&amp;minus;2&lt;/span&gt;&lt;span style=&quot;color: rgb(51, 51, 51); font-family: Arial, Helvetica, Geneva, Helvetica, sans-serif; font-size: 12px; line-height: 18px; text-align: justify;&quot;&gt;&amp;nbsp;d&lt;/span&gt;&lt;span style=&quot;font-size: smaller; position: relative; bottom: 0.4em; color: rgb(51, 51, 51); font-family: Arial, Helvetica, Geneva, Helvetica, sans-serif; line-height: 18px; text-align: justify;&quot;&gt;&amp;minus;1&lt;/span&gt;&lt;span style=&quot;color: rgb(51, 51, 51); font-family: Arial, Helvetica, Geneva, Helvetica, sans-serif; font-size: 12px; line-height: 18px; text-align: justify;&quot;&gt;. 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 &amp;gt;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.&lt;/span&gt;&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>32</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Trista J. Vick-Majors</style></author><author><style face="normal" font="default" size="100%">John C. Priscu</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Bacterioplakton dynamics in stratified lakes of the Taylor Valley, Antarctica during the transition to polar night</style></title><secondary-title><style face="normal" font="default" size="100%">Land Resources &amp; Environmental Sciences</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2010</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2010</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://scholarworks.montana.edu/xmlui/handle/1/2477</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Montana State University</style></publisher><pub-location><style face="normal" font="default" size="100%">Bozeman, MT</style></pub-location><volume><style face="normal" font="default" size="100%">M.S.</style></volume><pages><style face="normal" font="default" size="100%">83</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;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 -&amp;sup2;d -&amp;sup1;; range = 0.00 to 3.29 mg C m -&amp;sup2;d -&amp;sup1;), and also contained the greatest bacterial biomass (~10 ⁶ cells ml -&amp;sup1;) 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 &amp;quot;net heterotrophy&amp;quot;, which cannot be sustained unless the carbon balance of the TV lakes is reset by climatic events.&lt;/p&gt;</style></abstract><work-type><style face="normal" font="default" size="100%">masters</style></work-type></record></records></xml>