Role of phytoplankton in marine silicon cycling

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Marine phytoplankton are key components of the Earth system. They contribute half of the world’s annual photosynthetic fixation of carbon and play a fundamental role in nutrient cycling in the ocean. Of all phytoplankton groups, diatoms account for 20% of Earth’s photosynthesis and are the main biological drivers of processes involved in the cycling of silicon, carbon, nitrogen and other nutrients. Production of silica cell walls by diatoms in surface waters, dissolution of this biogenic silica through the water column, and export of biogenic silica and associated carbon from surface to deep waters are some of the most important fluxes in the oceanic silicon and carbon cycles. This proposal describes an integrated field and laboratory program that will advance our understanding of these critical, but poorly known, processes of the silicon cycle. During the next 5 years, my objectives are to quantify: