CORDIO Status Report 1999.pdf

Executive Summary
The reports in this volume summarize the extent of
damage to the coral reefs of the Indian Ocean caused by
the elevated temperatures in 1998. Most of the reports
also contain information on the status of reefs 6 to 12
months after the events of 1998, thus describing the fate
of dead corals, the first signs of recovery in some areas,
and the secondary damage to other organisms dependent
on the reef, such as fish. A brief summary of the
results is given here.
EAST AFRICA
• Several areas suffered very high coral mortality. For
example, surveys in Kiunga and Malindi (Kenya),
Misali and Mafia (Tanzania), and Pemba and
Inhacca (Mozambique) showed that 90–100% of the
corals died after exposure to water temperatures that
exceeded 32°C, mainly in March and April 1998.
The mortality of corals culminated around mid-
May. In some areas, however, corals continued to die
until October.
• Following the event in 1998, coral cover appears to
have been reduced to between 10 to 50% of previous
levels in most areas along the coast of Kenya,
Tanzania and northern Mozambique. In some areas
the reduction is greater, i.e. up to or above 90%.
• Initial investigations indicate that fish communities
associated with coral reefs were affected by the coral
mortality and that, in general, herbivorous species
increased while corallivorous species decreased.
• In most affected areas, the cover of algal turf on
bleached and dead reefs increased significantly. On
Kenyan reefs, for example, algal cover in many areas
increased up to 200% as a result of the newly available
substrate.
INDIAN OCEAN ISLANDS
• Coral mortality ranged from 50–90% over extensive
areas of shallow reefs in Seychelles, Comoros,
Madagascar and Chagos. In some areas (around
Mahe, Seychelles), mortality was close to 100%.
• By the end of 1998, algal turf covered coral reefs
throughout much of the region.
• Monitoring of potentially toxic, epiphytic dinoflagellates
has shown drastically increased concentrations
in areas with dead corals.
• By early 1999, much of the dead coral in Chagos was
reported to be eroded to rubble, preventing recolonisation.
In Socotra Archipelago, coral rubble has been
washed ashore and can be found in piles on the beach.
• Preliminary assessments of the reef fish communities
in Chagos indicate that abundance and diversity have
decreased to less than 25% of their former levels.
SOUTH ASIA REGION
• Bleaching was reported down to a depth of 40 m in
Sri Lanka and 30 m in Maldives, as a result of water
temperatures of approximately 35°C during the
period April to June, 1998.
• In Sri Lanka and Maldives, nearly 90% of the corals
died in many areas. In the Hikkaduwa and Bar reefs
of Sri Lanka, close to 100% of the corals died, and by
the end of 1998, these reefs were covered by thick
algal turf. In May 1999, large areas of reefs in
Maldives showed few signs of recovery.
• In India, surveys indicated mortality between 50 and
90% in the reefs in Gulf of Mannar, Andaman
Islands and Lakshadweep.
• Assessments of the reef fish communities showed
drastic reductions in butterfly fish numbers in Sri
Lankan reefs.
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