Postdoctoral Fellowship: OPP-PRF: Deciphering the Role of Phytoplankton Community Composition in Southern Ocean Carbon Fluxes

Carbon primarily leaves the atmosphere by dissolving in the ocean or by being used in photosynthesis by land plants. While the physical processes that modulate Southern Ocean carbon fluxes are relatively well understood, the biological processes controlling the fluxes are less constrained, due in part to uncertainties in phytoplankton spatial and temporal variability. Characterizing the phytoplankton community composition of the Southern Ocean is important because different types of phytoplankton will use different amounts of carbon. Projections of changes in Southern Ocean carbon flux are hampered since most models do not differentiate different types of phytoplankton when parameterizing carbon fluxes. This research will improve understanding of how different phytoplankton species will change the amount of carbon entering the surface ocean and being exported to depth in the Southern Ocean, constraining climate projections. The researchers will tackle this problem by mapping phytoplankton community composition and characterizing the physical environment (e.g., mixed layer depth, ice cover, time of year, macronutrient concentrations, ocean temperature, region) in which each taxa dominates. Using a combination of atmospheric reanalyses, ship-based measurements, and profiling biogeochemical SOCCOM floats, researchers will then estimate how much carbon enters the ocean, how much carbon is exported to the deep ocean, and the total amount of phytoplankton. Finally, they will analyze these estimates in concert with phytoplankton community composition to quantify how efficiently each taxa exports carbon to the deep ocean. Synthesizing modeled phytoplankton community composition with estimates of carbon fluxes in the ocean will enable researchers to explore the role of phytoplankton diversity in Southern Ocean carbon fluxes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.