Behaviour
The coral reefs off the Pacific coast of Central America are thin and small relative to their counterparts in the Indo-Pacific and Caribbean. They are subject to periodic stresses such as El Niño events. In 1982–1983, 50 to 90% of the corals in the region were lost. A large increase in the population of Diadema mexicanum resulted and there was an increase in damage to the reefs caused by their spines. Diadema mexicanum is a herbivore and an important member of the reef community and plays a significant role in controlling algal growth. By limiting this growth they are capable of preserving coral by reducing competition for space and light. However, when the populations of sea urchins get too large their spines cause excessive abrasion to the corals and bioerosion of the reef. Nevertheless, the reduction in algae present is beneficial for the settlement of coral larvae.