ITMEMS Statement on Coral Bleaching

Ray Berkelmans rayb at
Tue Jan 5 18:14:16 EST 1999

International Tropical Marine Ecosystems Management Symposium (ITMEMS)
                  Statement on Coral Bleaching


A summit meeting on coral bleaching by world experts on coral bleaching
held in Townsville on 24 November 1998 released the following statement on
the status of reefs following the 1998 global coral bleaching event.

Tropical sea surface temperatures in 1997/98 have been higher than at any
other time in the modern record. Record SST increases over the tropics in
the past 15 years are not explained by existing climate models. The coral
bleaching associated with the high sea surface temperatures has affected
almost all species of corals.  Loss of some corals more than 1000 years
old indicates the severity of this event. Associated reef invertebrates
have been severely affected by unusually high sea temperatures.

Global coral bleaching and die off is unprecedented in geographic extent,
depth and severity, though it is highly spatially variable.  The only
major reef region spared from coral bleaching appears to be the Central
Pacific.  In some portions of the Indian Ocean, mortality is as high as

Coral bleaching is a general response to environmental stress, in
particular high temperature but also high irradiance, fluctuating
salinities, silt or combinations of these factors.

High seawater temperature may be related to global warming.  According to
the IPCC 1998, global temperature has significantly increased since 1860.
Corals live on the upper edge of their temperature tolerance, with high
temperatures directly damaging aspects of their physiology.  Thus, an
increase by about 2 degrees Celsius as predicted by IPCC for the next 50
years is of concern.  We do not know how much of this temperature increase
will affect the tropics, or whether corals can adapt to predicted
temperature increases.

Current projections of global warming suggest there will be increased
frequency of coral bleaching and coral mortality.

These events will eventually have important negative consequences for
biodiversity, fisheries, tourism and shore protection provided by coral

There is a need for a cross disciplinary research effort (including
ecologists, climatologists, chemists, oceanographers and remote sensors)
to evaluate the immediate and ultimate causes of coral bleaching, its link
to climate change, and the effect of coral bleaching on the ecosystem as a

ITMEMS recommends that a multi-disciplinary taskforce be immediately set
up to thoroughly inform the IPCC on coral reef issues prior to their next
report due in 2001.

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