College of Agriculture

Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/4

As the foundation of the land grant mission at Montana State University, the College of Agriculture and the Montana Agricultural Experiment Station provide instruction in traditional and innovative degree programs and conduct research on old and new challenges for Montana’s agricultural community. This integration creates opportunities for students and faculty to excel through hands-on learning, to serve through campus and community engagement, to explore unique solutions to distinct and interesting questions and to connect Montanans with the global community through research discoveries and outreach.

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    Microbial Community Dynamics in Two Polar Extremes: The Lakes of the McMurdo Dry Valleys and the West Antarctic Peninsula Marine Ecosystem
    (2016-10) Bowman, Jeff S.; Oceanog, La Jolla; Vick-Majors, Trista J.; Morgan-Kiss, Rachael M.; Takacs-Vesbach, Cristina; Ducklow, Hugh W.; Priscu, John C.
    The Palmer and McMurdo LTER (Long Term Ecological Research) sites represent climatic and trophic extremes on the Antarctic continent. Despite these differences, the microbial components of the McMurdo lake and Palmer marine ecosystems share fundamental characteristics, including the production of organic carbon via autotrophy and its assimilation via heterotrophy. We leveraged 20+ years of observations at the Palmer and McMurdo LTERs to identify key differences in microbial ecosystem dynamics between these sites. Although the relationships between fundamental biological parameters, including autotrophy and heterotrophy, are different between these sites, recent climate events have influenced the coupling of these parameters. We hypothesize that for the lakes of the McMurdo LTER, decoupling is largely driven by physical processes, whereas in the coastal Antarctic, it is largely driven by biological processes. We combined this hypothesis with a new analysis of microbial community and metabolic structure to develop novel conceptual microbial food-web models.
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    Solute sources and geochemical processes in Subglacial Lake Whillans, West Antarctica
    (2016-05) Michaud, Alexander B.; Skidmore, Mark L.; Mitchell, Andrew C.; Vick-Majors, Trista J.
    Subglacial Lake Whillans (SLW), West Antarctica, is an active component of the subglacial hydrological network located beneath 800 m of ice. The fill and drain behavior of SLW leads to long (years to decades) water residence times relative to those in mountain glacier systems. Here, we present the aqueous geochemistry of the SLW water column and pore waters from a 38-cm-long sediment core. Stable isotopes indicate that the water is primarily sourced from basal-ice melt with a minor contribution from seawater that reaches a maximum of ∼6% in pore water at the bottom of the sediment core. Silicate weathering products dominate the crustal (non-seawater) component of lake- and pore-water solutes, and there is evidence for cation exchange processes within the clay-rich lake sediments. The crustal solute component ranges from 6 meq L–1 in lake waters to 17 meq L–1 in the deepest pore waters. The pore-water profiles of the major dissolved ions indicate a more concentrated solute source at depth (>38 cm). The combination of significant seawater and crustal components to SLW lake and sediment pore waters in concert with ion exchange processes result in a weathering regime that contrasts with other subglacial systems. The results also indicate cycling of marine water sourced from the sediments back to the ocean during lake drainage events.
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