The experimental system described here provides constraints on the relative balance of gross dissolution and precipitation fluxes contributing to the observed net dissolution rate of calcite in seawater. We show that our dissolution rates fit well within a framework that accounts for the geometry of the dissolving mineral surface. We further show that carbonic anhydrase (CA) catalyzes calcite dissolution, which implicates the hydration of aqueous CO 2 as a rate-limiting step for calcite dissolution in seawater. The presence of carbonic anhydrase in carbonate-rich environments such as coral reefs or sinking marine particles is poorly understood. However, our findings suggest that CA activity would significantly enhance the rate at which alkalinity is cycled between solids and seawater in these environments.

Abstract