Reef Community Changes Associated with the 2009–2010 El Niño in the Southern Mexican Pacific

Abstract

Abstract: We surveyed coral reefs communities before (September 2007–March 2009) and during (September 2009) the 2009–2010 El Nino event on the coast of Oaxaca, southern Mexican Pacific to evaluate community changes associated with the warming event. From May 2009 to December 2010, we recorded positive deviations from the historical in situ sea surface temperature values. There were differences among the coral species Pocillopora damicornis, Pavona gigantea, and Porites panamensis with significant reductions in chlorophyll a and Symbiodinium density during El Nino, resulting in bleaching (>13%) and increase in algal coverage (mainly geniculate coralline algae). Concurrently, echinoderm and fish assemblages also experienced significant modifications; abundances of the sea urchins Eucidaris thouarsii and Centrostephanus coronatus increased during the warming event, whereas Diadema mexicanum declined; meanwhile, fish species such as Thalassoma lucasanum declined in favor of Stegastes acapulcoensis and Haemul...