Browsing by Author "Morgan-Kiss, Rachael M."
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Item 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.Item Responses of Antarctic Marine and Freshwater Ecosystems to Changing Ice Conditions(2016-10) Obryk, Maciej K.; Doran, Peter T.; Friedlaender, Ari S.; Gooseff, Michael N.; Morgan-Kiss, Rachael M.; Priscu, John C.; Schofield, Oscar; Stammerjohn, Sharon E.; Steinberg, Deborah K.; Ducklow, Hugh W.Polar regions are warming more rapidly than lower latitudes, and climate models predict that this trend will continue into the coming decades. Despite these observations and predictions, relatively little is known about how polar ecosystems have responded and will continue to respond to this change. Two Long-Term Ecological Research (LTER) sites, located in contrasting environments in Antarctica, have been studying marine and aquatic terrestrial ecosystems for more than two decades. We use data from these research areas to show that the extent and thickness of ice covers are highly sensitive to short- and long-term climate variation and that this variation significantly influences ecosystem processes in these respective environments. Declining sea-ice extent and duration diminishes phytoplankton blooms as a consequence of reduced water stratification, whereas the thinning of lake-ice cover enhances phytoplankton blooms because of increased penetrating light into the water column. Both responses have cascading effects on upper trophic levels.