Coral mortality associated with dino-flagellate blooms in the eastern Pacific (Costa Rica and Panama)

Coral reefs at Cano Island, Costa h c a , and Uva Island. Panama, were affected during severe dinoflagellate blooms in 1985. In the second half of 1985. mass mortality of reef fishes and invertebrates, especially reef corals, occurred during blooms of the dinoflagellates Cochlodinium catenatum and Gonyaulax monilata. At Cano Island, up to 100% coral mortality was observed between the surface and 3 m depth, with pocilloporid species and Tubastrea coccinea most severely affected. At Uva Island, only 13 % pocilloporid mortality occurred and this was confined to the shallowest reef areas ('-3 m). The copious amounts of mucus associated with C. catenatum, present in the water column to 1-3 m depth, and adhering to coral colonies, suggested that coral death was caused by smothering. Other conditions that may have affected reef organisms were the presence of toxlc G. monilata, and possible oxygen depletion due to the hlgh densities of phytoplankton and the decomposition of dead organisms. These dinoflagellate blooms have interfered with recovery of reefs disturbed d u r ~n g the 1982/83 El Nino warming event.