GBR Bleaching - final summary

Paul Marshall p.marshall at
Thu Jul 11 11:00:50 EDT 2002

Dear colleagues

Most of you will be aware the Great Barrier reef experienced a mass
coral bleaching event early this year. This event was more severe than
the event of 1998. This makes the bleaching event of 2002 the worst ever
recorded for the GBR.

In response to this event, the Great Barrier Reef Marine Park Authority
implemented a comprehensive survey of coral bleaching in collaboration
with AIMS, CRC Reef and NOAA. A summary of this program and an overview
of the bleaching event is now available on the GBRMPA web site (under
"Hot Topics"):

Below is a brief summary of the results of the program:

* Underwater surveys found that few reefs had completely escaped the
effects of coral bleaching. However, the majority of reefs appear likely
to survive the bleaching event with only minimal coral death. Extensive
mortality was recorded on only a few of the inshore reefs surveyed,
where up to 90% of corals were dead.

* The first signs of substantial bleaching were reported in January
2002. The worst of the bleaching event was over by April 2002.

* Aerial surveys found that coral bleaching was evident from the air at
almost 60% of the 641 reefs surveyed. Inshore reefs were more severely
affected by bleaching, as was the case in 1998. However, in 2002 many
offshore reefs were also affected.

* The effects of bleaching were highly variable, varying from negligible
to severe, even between reefs that were similar distances offshore.
Bleaching was generally most severe in shallower water, and strong
patterns of species susceptibilities were generally evident across the
sites surveyed.

* Further surveys are planned for later in 2002 when the fate of corals
that bleached during the Summer will be studied further.

* Should warm water events increase in severity, duration, or frequency
in the future, coral bleaching is likely to become increasingly severe
on the GBR.

We are continuing to analyse and interpret data collected from this
event and will add additional information as it becomes available.

We would like to offer special thanks to our partners in this monitoring
program, especially NOAA, AIMS and the CRC Reef, and to the many
individuals who submitted bleaching reports to our Online Bleaching
Reporting Program.


Paul Marshall
Research & Monitoring Coordination
Great Barrier Reef Marine Park Authority

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