| Summary: | Thesis (M.Sc.)--Memorial University of Newfoundland, 2011. Biology Bibliography: leaves 118-135. Heterotrophic marine micorbes were studied across spatial and temporal scales in the northwest Atlantic to investigate microbial communities' structural and functional responses to climate-relevant environmental forcings. Cellular abundance, morphometric, and 16S RNA-targetted Fluorescent In Situ Hybridization (FISH) analyses were used to examine variation in microbe-mediated carbon flow as it pertained to grazing pressure, temperature-shifts, and dissolved organic matter (DOM) availability. Significant spatial differences in growth and biomass production versus experimental manipulations indicate climate-driven physical changes in the upper ocean may influence future basin-scale patterns of the biogeochemical cycling of carbon. Seasonal variation of cell size and growth during grazer-exclusion experiments points to the increasing importance of inorganic nutrient limitation on plankton dynamics in a warming ocean. Analysis of grazing control on microbial communities relative to current and predicted ocean temperatures also suggests impacts of a warming ocean on spring phytoplankton bloom initiation and on carbon cycling in the upper ocean.
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