Enhanced acidification of global coral reefs driven by regional biogeochemical feedbacks

Physical uptake of anthropogenic CO 2 is the dominant driver of ocean acidification (OA) in the open ocean. Due to expected decreases in calcification and increased dissolution of CaCO 3 framework, coral reefs are thought to be highly susceptible to OA. However, biogeochemical processes can influence the p CO 2 and pH of coastal ecosystems on diel and seasonal time scales, potentially modifying the long‐term effects of increasing atmospheric CO 2 . By compiling data from the literature and removing the effects of short‐term variability, we show that the average p CO 2 of coral reefs throughout the globe has increased ~3.5‐fold faster than in the open ocean over the past 20 years. This rapid increase in p CO 2 has the potential to enhance the acidification and predicted effects of OA on coral reef ecosystems. A simple model demonstrates that potential drivers of elevated p CO 2 include additional anthropogenic disturbances beyond increasing global atmospheric CO 2 such as enhanced nutrient and organic matter inputs.