The extent and intensity of the 1998 mass bleaching event on the reefs of Mauritius, Indian Ocean

The most severe and large scale-bleaching event on record occurred in 1998 world-wide. In Mauritius, three surveys covering 2 habitats at 4-5 sites were conducted to describe and quantify the event. Bleaching was recorded at all sites and habitats. However, relatively few corals were bleached (<10%) except at one localised site (Le Bouchon: 38.6%) indicating that Mauritius was one of the few islands in the Indian Ocean to have sustained a comparatively mild bleaching episode. On the reef flat Acropora species were generally more susceptible to bleaching than non-Acropora species. In contrast on the reef slopes, non-Acropora species were more affected than the Acropora species. Furthermore, susceptibility to bleaching differed within colonies and species. The main cause of this bleaching event was most likely due to an increase in seawater temperature and solar radiation, exacerbated by lowered salinity from higher seasonal rainfall.