Coral Bleaching, Diseases and Mortality in the Western Indian Ocean

Abstract

The western Indian Ocean generally receives less scientific attention regarding corals and coral reefs than other regions, but it has not been spared many of the deteriorating effects of either bleaching or diseases (McClanahan 2000). Both factors, but particularly bleaching, are among the leading causes of reef degradation in the region and this was made abundantly clear in 1998 when most of the region was exposed to one of the warmest El Niño Southern Oscillation (ENSO) events in at least the past 200 years (McPhaden 1999; Cole et al. 2000). This ENSO caused 50–60% mortality and reduced coral cover to <10% of the substratum in many of the region’s reefs (Goreau et al. 2000). It was fol-lowed by an additional ENSO and bleaching event in 2003 and somewhat mysterious and large-scale mortality of corals by unknown disease in 2002. These events have elevated these past curiosities to the top of the coral reef scientific and conservation agenda. Coral reef investigators are now attempting to understand these events, and their full consequences to reef and fisheries ecology and possible mitigation by management. Below, I describe a few of the recent notable events and discuss some questions and topics for future research.