Biodiversity and ecosystem function of Arctic marine microbial food webs

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Marine single celled phytoplankton are responsible for half of the planet's oxygen production, and they are part of the complex assemblages of microscopic communities than make up marine microbial food webs. These webs are functionally diverse and in addition to the primary producers they contain primary and secondary grazers, predators, parasites, detritivores, and chemosynthetic microorganisms that mineralize organic nitrogen, carbon and other elements. These microbial communities are at the base of all higher food webs in the Arctic Ocean, and affect the life cycles of Arctic marine animals from zooplankton to seals, which are strongly linked to the predictable appearance of specific food sources during critical life stages. The major goal of my research is to define relationships among physical oceanographic conditions and microbial assemblages. We will address these and related questions by combining molecular biological approaches with other biological and physical oceanographic observations. This research will provide training for HQP at all levels and will include four PhD projects. The first will identify microbial food web complexes and will model carbon and energy pathways within the complexes. Since nitrogen supply and its biological transformations largely determine net primary productivity in the Arctic, the second student will develop protocols to target sequences coding for key genes to estimate and describe the diversity nitrogen processes across biogeographic provinces. The Arctic is highly salinity stratified and the third project will investigate nitrogen processing genes at the center of major water masses, where conditions change only slowly, and will compare these to the same genes along seawater density gradients, where conditions change rapidly. The fourth PhD project will run laboratory and field experiments to determine the ecological filters acting on indicator species and their gene expression. This research will harness emerging technologies to generate improved predictive understanding of the structure and functioning of cold ocean ecosystems, and of how Arctic marine communities and food webs will respond to accelerating climate change in the region.