|An episode of extremely high ocean temperatures
migrated from south to north throughout the Indian Ocean during the first
six months of 1998 causing considerable coral reef bleaching in its wake,
the National Oceanic and Atmospheric Administration reports.
Sea surface temperatures, exceeding the maximum values expected for any time during the year, were observed by NOAA's satellites to have exceeded levels critical to cause beaching where these waters overlay Indian Ocean coral reefs.
A somewhat similar episode occurred following the 1987 El Nino in the Indian Ocean; however, in 1988 the extreme sea surface temperature anomalies, toxic to corals, moderated sufficiently as the sun moved into the Northern Hemisphere. In that year, reefs in the Indian Ocean north of the equator were spared heavy bleaching.
In 1998, this has not been the case. Bleaching, earlier projected by NOAA, has been reported from the field on the following reefs: Seychelles; Kenya; Reunion; Mauritius; Somalia; Madagascar; Maldives; Indonesia; Sri Lanka; Gulf of Thailand [Siam]; Andaman Islands; Malaysia; Oman; India; and Cambodia.
This unprecedented round of bleaching in coral reefs throughout the Indian Ocean follows El Nino-related bleaching events during late-1997 and early-1998 both projected by NOAA's satellite HotSpot charts and documented by reef scientists in Mexico (Pacific), Panama (Pacific); Galapagos; Australia's Great Barrier Reef; Papua New Guinea; and American Samoa.
In the Indian Ocean, sea surface temperature anomalies appear to be coming less severe toward the end of June. The total area covered by "HotSpots" is now only in the northernmost fringes of the Indian Ocean. However, during June the Philippines and the Florida Keys regions have been seeing temperature anomalies sufficiently high that bleaching has been reported and biologists are concerned for reefs there.
Coral reefs -- the "rainforests of the oceans" -- support a variety of sea life and provide resources of significant economic importance such as fishing and recreation. Coral bleaching, induced by high water temperatures, has raised concerns about these fragile ecosystems. Coral bleaching occurs as coral tissue expels zooxanthellae, a type of algae that resides in the structure of the coral, and is essential to the coral's survival. Corals normally recover, unless high ocean temperatures persist for too long a period or become too warm.
Coral Reef "HotSpots" depicted as regions of yellow/orange in the NOAA/NESDIS charts highlight those anomalies that are equal to or above the annual maximum sea surface temperatures by +1 deg C or more.