Spatial and temporal variation in the population structures, carbon use and climate responses of heterotrophic microbial communities in coastal and offshore northwest Atlantic sites

Murphy, Ryan M. J. (Ryan Matthew John) (2010) Spatial and temporal variation in the population structures, carbon use and climate responses of heterotrophic microbial communities in coastal and offshore northwest Atlantic sites. Masters thesis, Memorial University of Newfoundland.

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Abstract

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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