Global Response of Coral Reef Benthic Calcium Carbonate Dissolution to Ocean Acidification

Ocean acidification (OA) is predicted to have a significant impact on the future of coral reefs, mainly through the reduced formation of calcium carbonate (CaCO3). However, the dissolution of stored CaCO3 has largely been overlooked in the OA community. CaCO3 sediments represent the largest reservoir of carbonate minerals in coral reefs and result from the accumulation and storage of CaCO3 material over thousands of years. This presentation will demonstrate the in situ drivers of dissolution in coral reef carbonate sands and how they will respond to increasing average pCO2 (ocean acidification). In situ benthic incubations at coral reefs around the world show that aragonite saturation in the overlying water is a strong predictor of CaCO3 sediment dissolution and most reefs show a similar response to increasing average pCO2 (OA). However, every reef shows a different net sediment dissolution starting condition and the effect of end of century OA conditions on net sediment dissolution is different for every reef. The rate at which sediments are predicted to dissolve by the year 2100 has important implications on the net accretion of coral reefs and their future survival. Quantifying the global dissolution kinetics of CaCO3 sediments is clearly just as important as estimating calcification rates when predicting how OA will impact coral reef ecosystems