Response Of Microbial Community Structure And Protistan Grazing Pathways To Environmental Forcing In The Arabian Sea

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9311246 Landry The Arabian Sea is an intensely dynamic region of the world's oceans driven by strong seasonal reversals in monsoon winds. The region is interesting in the context of the Joint Global spatial scales "extremes" in ocean production systems -- coastal upwelling to open ocean oligotrophic -- under relatively constant tropical illumination. It is thus a natural laboratory to test conceptual linkages among physical forcing, food-wed structure, biogeochemical cycling and fluxes, and carbon burial in the sediments. The general goals of this project are to asses the roles of microzooplankton as consumers of bacterial and phytoplankton production and to contribute to understanding the relationships among plankton community structure, new production, and biogeochemical fluxes and their responses to physical forcing the Arabian Sea. The project is to be conducted during the spring (April) intermonsoon and summer (August) SW monsoon seasons, when the most dramatic differences should be evident. Abundance, biomass, and specific growth rates of bacteria and phytoplankton will be determined by flow cytometric, microscopic, and pigment analyses to determine their variations with season, depth and location. The dominant microzooplankton grazers on pico- and nanoplankton will be identified and quantified, and the impact of their grazing will be measured with a suite of complementary methods including dilution, fluorescently-labelled prey, size- fractionation, and specific metabolic inhibitors. Results of this project will contribute to understanding how global climate changes, which may affect prevailing forcing winds, will alter phytoplankton community structure and in turn how these changes in structure of the food web affect carbon storage and export from the upper water column.