Conservation of Coral Reefs after the 1998 Global Bleaching Event

Abstract

Large-scale coral bleaching has happened repeatedly in the Pacific and Indian oceans and the Caribbean since 1982. Previously it was observed only on a small scale (Williams and Bunkley-Williams 1990; Jokiel & Coles 1990; Glynn 1988, 1991; Goreau et al. 1993; Goreau & Hayes 1994, 1995). The 1998 bleaching event was globally the most extensive such event recorded except in the Caribbean and Central Pacific where a comparison of year-by year temperature and bleaching maps show that it was comparable with the largest previous events (T.G. et al., unpublished data). Global analyses of coral bleaching are rare, but critical to an understanding of the widespread ecological effect of bleaching events. We reviewed data, both published and unpublished, on the 1998 event and discuss the potential broad-scale implications for coral reef conservation. Large-scale coral reef bleaching is triggered by positive sea surface temperature (SST) anomalies, although other stress factors also can cause small-scale bleaching. The term bleaching hotspot has been coined to describe SST anomalies that approximate or exceed by 1.0° C or more the SST expected climatologically during the warmest month of the year as seen from NOAA's satellite derived observations (portrayed on monthly ocean features analysis maps [Goreau & Hayes 1994] or NOAA's new, twice-weekly Bleaching Hotspot Chart [Strong et al. 1997; Goreau et al. 1997]). Many areas of the tropical oceans were influenced by unprecedented elevations in sea surface temperature during 1998 due to a severe El Nino Southern Oscillation (ENSO), and the Indian Ocean's 11-year oscillation, superimposed on a recently noted warming over the northern hemisphere tropics (Strong et al. 1997).