concept

Bioerosion

The breakdown of reef limestone caused by living organisms, not by waves or chemistry alone. Parrotfish scrape whole mouthfuls of coral framework to eat the algae on it; boring sponges, molluscs and worms tunnel into the skeleton from within; endolithic algae and bacteria erode it at the microscopic scale. This is the "debit" side of the [[carbonate-budget]]: a healthy reef still builds faster than it is ground down, but once live coral declines, bioerosion wins and the foundation begins to hollow out and collapse.