Temporal Variations in Calcium Carbonate Dissolution Rates Under Ambient and Elevated pCO2 in a Shallow Coral Reef Lagoon

Dissolution of permeable calcium carbonate (CaCO3) sand on coral reefs is likely driven by environmental dissolution (overlying bulk seawater chemistry), benthic metabolism, and bioerosion. Most studies on dissolution are confined to laboratory, mesocosm, or rare in situ studies, but none of these have considered seasonal variations. Coral reefs exhibit high natural variability of carbonate chemistry on spatial and temporal scales, driven by processes such as photosynthesis, respiration, calcification and CaCO3 dissolution. This inherent variability of reef biogeochemistry complicates projections for the effects of ongoing ocean acidification on coral reef ecosystems. In order to understand future responses of coral reef ecosystems to elevated carbon dioxide (CO2) it is necessary to first understand the natural variability of the carbonate chemistry and dissolution rates and the controls on these processes. This is particularly important in the context of a possible shift from net calcification to net dissolution of reefs which some models project for the end of the century. This study investigated CaCO3 dissolution rates under both ambient and elevated CO2 levels in relation to seasonal variations in water column physico-chemical properties and benthic metabolism