#Status of Coral Reefs 2002 - International Coral Reef Action Network

Coral Bleaching and Mortality
coral growth on Madagascar is encouraging, but in many areas this is just balancing
damage from anchors and pollution from the land. The major impacts were, however in
the Comoros and Seychelles. Reefs in the Comoros appear to be recovering well, for
example the corals in the Moheli MPA had recovered about half of their former coral cover
to about 20% by early 2002, with even better prospects as recruitment was strong in 2002.
The situation is less encouraging in the Seychelles with very low rates of natural recovery,
even in the protected areas. Most recovery is in deeper water.
CORAL RECOVERY, AND FISH COMMUNITY RESPONSES AFTER 1998 BLEACHING
AT ALDABRA, SEYCHELLES
The Aldabra Marine Programme (AMP) set up 11 permanent monitoring sites at
Aldabra Atoll, southern Seychelles, to follow reef recovery after the 1998 El Niño
bleaching. Aldabra is a World Heritage Site with virtually no anthropogenic impacts.
AMP monitored changes in the coral communities using video transects, 1m 2 quadrats
for coral recruits, and visual fish counts. In 1998, about 40% of the hard corals on the
outer reef were recently bleached and 22% corals died in shallow water (10m). Few
corals died in deeper water (20m) despite very severe bleaching. Coral mortality was
at least 50% at St. Pierre Island, approximately 450km northeast of Aldabra. Many
massive colonies bleached, but often had live polyps around the base. Now there is 3 -28%
live coral cover in shallow water around Aldabra, and 0.2-36% in deep water. The
highest coral cover is on the sheltered north western end and decreases steadily
towards the more exposed south eastern end. Cover on islands east of Aldabra ranges
between 12-32% in shallow water and 17-30% in deep water. Live coral cover at
Aldabra did not increase significantly between 1999 and 2002, although the trend is
rising from year to year suggesting recovery. Coral recruitment is high at Aldabra,
ranging from 1-13 per m 2 in 2001 and 1-14 in 2002. St. Pierre and Assumption islands
also have high recruitment, but it is low on Astove with only 1% in both shallow and
deep water. Thus recovery is well underway on Aldabra and the nearby islands, and
should accelerate, however, poor coral recruitment and an extensive bloom of
Caulerpa algae, are delaying recovery at Astove. AMP counted 221 fish species from 38
families in February 2002 at Aldabra, which is higher than 211 species from 35 families
in 1999 and 205 species from 40 families in 2001, but less than the 251 fish species
identified in 1998. The combined count is 289 species, which indicates a healthy fish
population. The degree of habitat complexity on Aldabra is important as there were
more fish in very structured habitats, irrespective of whether the coral was live or
dead. Fish numbers have fluctuated between 1,501 fish per 100m 2 in 2001 to
approximately 3,000 fish per 100m 2 in 1999 and 2002; probably due to large passing
schools of some species. AMP will continue monitoring the corals and fishes at Aldabra
and other sites in the southern Seychelles, and is including sites under more
anthropogenic pressures. From: Raymond Buckley, Ben Stobart, Nigel Downing,
Kristian Teleki, Larry LeClair and Martin Callow; web site: www.aldabra.org
35