Flow Cytometry and Biogeochemistry. The genomics revolution has highlighted an amazing level of diversity in phytoplankton for both taxonomy and metabolic potential. We utilize flow cytometry as a tool to assist in generating physiological information for discrete phytoplankton populations from a range of natural environments. This includes cell properties such as cell carbon, nitrogen and phosphorus quotas and lipid content, as well as physiological rate processes such as ambient nutrient uptake rates. This information we share with our ecosystem modeling colleagues to improve the 'reality' of these models.
Phytoplankton Biogeography and Biogeochemical Cycles. A widely held belief in marine biogeochemistry is that the biological sequestration of carbon to the ocean interior, the biological carbon pump, is largely determined by phytoplankton cell size. In this paradigm biogeographic provinces dominated by small (pico- and nano-) phytoplankton do not contribute to the biological carbon pump. Over the past decade data has been accumulating on the quantitative importance of these pico- and nanophytoplankton to the ocean's biological carbon pump. Our group has conducted research in the Sargasso Sea, the subArctic North Pacific and the Bering Sea to study the relationships between phytoplankton communities growing the sunlit ocean and those sinking to the ocean interior.
Microbial Ecosystem Responses to Climate and Ocean Change. This research has focused in two areas; the loss of seasonal sea ice in the Bering Sea due to regional warming, and ocean acidification in the Sargasso Sea. Our research in the Bering Sea has focused on how changes in phytoplankton assemblage in warm and cold years impacts the flow of carbon up through the food chain all the way to harvestable fisheries. Our ocean acidification research in the Sargasso Sea has focused on the response of the whole microbial community, not just the calcifiers, and in particular how ocean acidification impacts the elemental stoichiometry of specific populations, the relative abundance of these populations and ultimately the biological carbon pump.