© 1992 by The Society for Integrative and Comparative Biology
Sporadic Disturbances in Fluctuating Coral Reef Environments: El Niño and Coral Reef Development in the Eastern Pacific1
Division of Marine Biology & Fisheries, Rosenstiel School of Marine & Atmospheric Science, 4600 Rickenbacker Causeway, University of Miami Miami, Florida 33149-1098
Department of Geology, College of Charleston Charleston, South Carolina 24924
The disastrous effects of the intense 1982–83 El Niño-Southern Oscillation (ENSO) bring new insight into the long-term development of eastern Pacific coral reefs. The 1988–83 ENSO sea surface warming event caused extensive reef coral bleaching (loss of symbiotic zooxanthellae), resulting in up to 70–95% coral mortality on reefs in Costa Rica, Panama, Colombia and Ecuador. In the Galapagos Islands (Ecuador), most coral reefs experienced >95% coral mortality. Also, several coral species experienced extreme reductions in population size, and local and regional extinctions. The El Niño event spawned secondary disturbances, such as increased predation and bioerosion, that continue to impact reef-building corals. The death of Pocillopora colonies with their crustacean guards eliminated coral barriers now allowing the corallivore Acanthaster planci access to formerly protected coral prey. Sea urchins and other organisms eroded disturbed corals at rates that exceed carbonate production, potentially resulting in the elimination of existing reef buildups. In other reefbuilding regions following extensive, catastrophic coral mortality, rapid recovery often occurs through the growth of surviving corals, recruitment of new corals from nearby source populations, and survival of consolidated reef surfaces. In the eastern Pacific, however, the return of upwelling conditions and the survival of coral predators and bioeroders hamper coral reef recovery by reducing recruitment success and eroding coral reef substrates. Thus, coral reef growth that occurs between disturbance events is not conserved. Repeated El Niño disturbances, which have occurred throughout the recent geologic history of the eastern Pacific, prevent coral communities from increasing in diversity and limit the development and persistence of significant reef features. The poor development of eastern Pacific coral reefs throughout Holocene and perhaps much of Pleistocene time may result from recurrent thermal disturbances of the intensity of the 1982–83 El Niño event.