Microzooplankton grazing on the coccolithophore and its role in the global calcium carbonate cycle.

Identifying mechanisms driving the substantial dissolution of biogenic CaCO (60 to 80%) in surface and mesopelagic waters of the global ocean is critical for constraining the surface ocean's alkalinity and inorganic carbon budgets. We examine microzooplankton grazing on coccolithophores, photosynthetic calcifying algae responsible for a majority of open-ocean CaCO production, as a mechanism driving shallow dissolution. We show that microzooplankton grazing dissolves 92 ± 7% of ingested coccolith calcite, which may explain 50 to 100% of the observed CaCO dissolution in supersaturated surface waters.