Coral And Algal Response To The 1998 El Niño Coral Bleaching And Mortality On Kenya’s Southern Reef Lagoons

Abstract

The 1998 interaction between the El Niño and the Indian Ocean dipole produced one of the warmest years in recent records (McPhaden, 1999; Saji, 1999; Webster et al., 1999) and is reported to have caused extensive coral bleaching and mortality throughout the western Indian Ocean (Strong et al., 1998; Goreau et al., 1999; Wilkinson et al., 1999). Previous observations of coral bleaching in Kenya were recorded in 1987 and 1994 with the 1987 event causing significant mortality in corals and other benthic invertebrates (McClanahan, unpublished data and observations). The East African coast has a strong seasonal cycle and these bleaching events occurred at the end of the warm north-east monsoon, usually beginning in March, during the local annual peak of solar irradiance and water temperature (McClanahan, 1988). The recent 1998 coral bleaching event was the most severe in terms of the mortality of benthic organisms, particularly corals, and, therefore, efforts were made to document this event and to determine the sensitivity of coral genera to this disturbance, the role of reef management and in particular, the role of herbivory, on the ecological outcome of this coral mortality.