Status of Coral Reefs of the World 2000

Status of Coral Reefs of the World: 2000
CORAL BLEACHING AND MORTALITY OF 1998
Comoros
The coral reefs experienced extremely widespread coral bleaching in 1998. Approximately
50% of the corals were bleached at Moheli, which had been renowned for its pristine
reefs. There was 40 to 50% coral bleaching at the Mitsamiouli monitoring site, with
Acropora species being the worst affected. Socioeconomic impact assessments are being
conducted under the CORDIO project, but already professional fishing has been severely
hit, with reductions in benthic fish catches. There are no reliable data on the correlation
between corals observed bleached and subsequent mortality, and many corals were
partially bleached and recovered.
Madagascar
Coral bleaching affected many coral sites in Madagascar, few data were available at the
time of this report, moreover the database software and the corresponding data were not
functional in Madagascar. However, brief reports from the 1999 monitoring surveys indicate
that the Nosy-Antafana Marine Park was affected directly, with a reduction in reef flat coral
cover and increases in the cover of algae.
BLEACHING IN THE SEYCHELLES
The shallow coral reefs of the Seychelles granite islands suffered severe damage
following the 1997/1998 mass coral bleaching event, and signs of recovery are slight.
Live coral cover was reduced to less than 10% on most reefs around the inner islands,
with high partial mortality of colonies. Dead standing coral is present on sheltered
reefs, while exposed reefs have already been reduced to rubble. Zoanthids,
anemones, and encrusting red and green calcareous algae have colonised shallow reef
slopes and lagoons, and soft corals are growing on deeper reef slopes. Branching and
tabular Acropora species and branching Pocillopora species have died on all reefs,
with the only live corals left being massive species, (Porites, Goniopora, Acanthastrea
and Diploastrea). The only areas with some coral cover either had low coral diversity or
in shallow stressed environments such as the high turbidity Beau Vallon Bay and near
the harbour on Mahe. Therefore most coral species have survived somewhere in the
islands, but diversity on an individual reef has been severely reduced down to about
10 species. Recruitment of branching Acropora and Pocillopora corals is low, with
35% of sites showing no recruitment, and elsewhere some recruits (1-10cm diameter)
were observed on limestone pavement, dead standing coral and rubble. These small
colonies will be very vulnerable to predation from fish and urchins, and abrasion from
mobile unconsolidated substrates during storms. Death and erosion of the reef edge
has exposed many lagoons and shores to wave action, and there are signs of beach
erosion on some islands such as La Digue. There is an urgent need to monitor
recruitment and to protect live coral and recovering reefs, especially in those areas
affected by activities on land, fishing and anchoring. Contributed by: John Turner,
School of Ocean Sciences, University of Wales, Bangor, UK, e-mail J.turner @
bangor.ac.uk
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