Hot Spots of Carbon and Alkalinity Cycling in the Coastal Oceans

Ocean calcium carbonate (CaCO₃) production and preservation play a key role in the global carbon cycle. Coastal and continental shelf (neritic) environments account for more than half of global CaCO₃ accumulation. Previous neritic CaCO₃ budgets have been limited in both spatial resolution and ability to project responses to environmental change. Here, a 1° spatially explicit budget for neritic CaCO₃ accumulation is developed. Globally gridded satellite and benthic community area data are used to estimate community CaCO₃ production. Accumulation rates (PgC yr^-1) of four neritic environments are calculated: coral reefs/banks (0.084), seagrass-dominated embayments (0.043), and carbonate rich (0.037) and poor (0.0002) shelves. This analysis refines previous neritic CaCO₃ accumulation estimates (~0.16) and shows almost all coastal carbonate accumulation occurs in the tropics, >50% of coral reef accumulation occurs in the Western Pacific Ocean, and 80% of coral reef, 63% of carbonate shelf, and 58% of bay accumulation occur within three global carbonate hot spots: the Western Pacific Ocean, Eastern Indian Ocean, and Caribbean Sea. These algorithms are amenable for incorporation into Earth System Models that represent open ocean pelagic CaCO₃ production and deep-sea preservation and assess impacts and feedbacks of environmental change.