Reef recovery 20 years after the 1982-1983 El Niño massive mortality

Abstract

For over 20 years the El Niño-Southern Oscillation (ENSO) has caused damage to the coralreefs of the eastern Pacific and other regions. In themid-1980s scientists estimated that coral cover wasreduced by 50-100% in several countries across theregion. Almost 20 years (2002) after the 1982-1983 event, we assessed the recovery of the virtually destroyed reefs at Cocos Island (Costa Rica), previously evaluated in 1987 and reported to have less than 4% live coral cover. We observed up to two fold increase in live coral cover which varied among reefs surveyed in 1987 and 2002. Most new recruits and adults belonged to the main reef building species from pre-1982 ENSO, Porites lobata, suggesting that a disturbance as outstanding as El Niño was not suYcient to change the role or composition of the dominant species, contrary to phase shifts reported for the Caribbean. During the 1990s, new species were observed growing on the reefs. Notably, Leptoseris scabra, considered to be rare in the entire PaciWc, was commonly found in the area. Recovery may have begun with the sexual and asexual recruits of the few surviving colonies of P. lobata and Pavona spp. and with long distance transport of larvae from remote reefs. We found an overall 23% live coral cover by 2002 and with one reef above 58% indicating that Cocos Island coral reefs are recovering.