Status of Coral Reefs

There has been significant bleaching of hard and soft corals in widely separate parts of the world from mid-1997 to the last months of 1998. Much of this bleaching coincided with a large El Niño event, immediately switching over to a strong La Niña. Some of the reports by experienced observers are of unprecedented bleaching in places as widespread as (from west to east) the Middle East, East Africa, the Indian Ocean, South, Southeast and East Asia, far West and far East Pacific, the Caribbean, and the Atlantic Ocean. There was a wide spectrum of reports on bleaching ranging from: • catastrophic bleaching with massive mortality, often near 95% of shallow (and sometimes deep-water) corals such as in Bahrain, the Maldives, Sri 15 COMPILED BY CLIVE WILKINSON Coral bleaching followed the climate switch from El Niño in the East Pacific (low SOI values) to La Niña (high SOI) around Australia and Asia. Status of Coral Reefs of the World: 1998 Lanka, Thailand, Singapore, and parts of Tanzania; through • severe bleaching over large areas with significant mortality (around 50% to 70%) with recovery of larger, more resistant species (Kenya, Tanzania, the Seychelles, Thailand, Vietnam, Japan and Belize); to • severe bleaching only in some of the reefs, with a mix of recovery and mortality (around 20% to 50% in places), for example Oman, Madagascar, the Great Barrier Reef, parts of Indonesia and the Philippines, Taiwan, Palau, French Polynesia, the Galapagos, the Bahamas, Cayman Islands, Florida, Bermuda, Brazil; and • finally, on large areas of the worlds reefs, insignificant or no bleaching was observed. Bleaching was most pronounced in shallow water (less than 15 m) and particularly affected staghorn and plate A c r o p o r a and other fast growing species, with a high proportion of coral death. Slower growing massive species, like P o r i t e s, also bleached, but many recovered within 1 or 2 months. Some people commented that bleaching like this had not been seen in 40 years of observations. While this was occurring, there were large areas of the world where bleaching was not observed. Little or insignificant bleaching was seen in the Red Sea, southern Indian Ocean, Andaman Sea, most of Indonesia, large parts of the Great Barrier Reef, most of the central Pacific and many parts of the southern and eastern Caribbean. In some places with no bleaching, severe bleaching similar to that observed above had occurred in past years, with significant recovery since then. The consensus is that this is probably the most severe bleaching event ever observed, but there were far more observations and observers this year, and a greater degree of interest in reporting bleaching. Many of the bleaching reports, possibly 80%, are estimates and the reports of bleaching may be exaggerated because bleached corals are particularly dramatic. However, amongst the reports there are actual measurements which often are close to the estimates. Much of this interest has arisen because regular, real-time reports are available on sea-surface temperatures over the internet and on e-mail lists through the National Oceanographic and Atmospheric Administration of the USA. Now the large questions are whether observed bleaching will result in death or recovery of the corals, and whether there is potential for the damaged reefs to bounce back and recover from this event. But the most important question is whether this is just a severe, one-off event, as it now appears, or whether events like this will occur more frequently as the world’s atmosphere and waters warm up.