Coral cover change associated to El Nino, Eastern Pacific, Costa Rica, 1992-2001

Changes in live and dead coral cover were documented at three localities off the Costa Rican central Pacific coast first in 1992 during the aftermath of the 1991-1992 El Nino; again in the period between 1994 and 1995, and last in January 2001. Recovery of coral communities after the 1991-1992 El Nino was expressed by a significant increase (similar to40 %) in 1994 of live coral cover at one locality (Manuel Antonio). A subsequent decrease (similar to50 %) in response to the very strong 1997-1998 episode was recorded at Manuel Antonio and Ballena, mainly due to partial tissue mortality of branching (Pocillopora spp.) and massive (Porites lobata) corals. Mortality of entire colonies associated to that event was scarce and confined to branching and nodular (Psammocora stellata) corals. This species was not found at one locality (Cambutal) in the 2001 survey and it is presumed locally extinct. The recovery of this coral and others will depend on recruits from surviving colonies in deeper waters and other coral communities in the vicinity. Within sites at a given locality, contrasting results in live coral cover variability were found. This is partially due to distinct coral assemblages, coral growth, physical exposure to tidal regime, and, related to the latter, variable duration and intensity of the warming event. In general, predominant meteorological conditions at the studied area are conducive to solar radiation (UV) stress during El Nino years and are related to changes in the atmosphere-ocean interactions in response to the warming events.