Status of Coral Reefs of the World 2000

Status of Coral Reefs of the World: 2000
transect. Turf algae (2.8%) were the only living material. This shallow zone (1m low tide)
was severely impacted during the 1998 El Niño with around 95% coral mortality. In 2000,
some living corals appeared (0.9%), along with zoanthids (Palythoa - 10%) and algae
(12.3% - calcareous and macroalgae -Turbinaria). There were no new Acropora recruits,
but the calcareous algae will constitute a good substrate for new coral settlement. On the
outer slope, there was a low cover of living corals (2.1%), mostly massive forms and some
soft corals. All the branching Acropora disappeared during the 1998 bleaching event.
Some coral recovery was observed in 2000 with 0.5% branching Acropora, and a definite
increase, although not quantified, of non-Acropora forms, mostly massive and soft corals.
Algae were just 6.2% of cover, mostly calcareous algae (2.3%) and a few Turbinaria sp.
The Silhouette site was added in 2000. The reef flat is heavily impacted by the south-east
monsoons and has always had low coral cover. The site at 2m depth has no Acropora, a 9%
cover of non-Acropora (encrusting and massive corals), and some soft zoanthids (Palythoa).
Most of the cover (over 50%) was dead coral rubble and sand. The outer slope (5-6m
depth) had alive and dead massive corals (>15%) scattered over a sandy zone, with
submassive corals (>15%), some encrusting corals, and 0.7% branching, very young
Acropora which showed signs of fish grazing. This site appeared to escape most of the 1998
El Niño bleaching, possibly due to better water exchange with the cooler deeper waters.
COMPARISON OF 1997 – 2000 DATA
Coral cover on the Ternay Bay outer slope dropped from 54.6% in November 1997 to 3.5%
in June 1998, 2.1% in January 1999 and 5.1% in March 2000. Acropora was more affected
(29.1% in 1997, 0% in 1998 and 1999, and 0.5% in 2000) than non-Acropora massive
corals (25.5% in 1997, 3.5% in 1998, 2.1% in 1999 and 4.6% in 2000). Soft corals appear to
be fast growing, opportunistic species. As a reflection of these changes, abiotic forms
went from 37% in 1997 to 92.3% in 1998, 92.8% in 1998 and 86.8% in 2000. These losses
can be attributed to the 1998 bleaching phenomenon, as human activities are limited, and
recovery is predicted for good coral cover, provided bleaching does not happen again
within the next few years. A similar pattern was evident on the reef flat with a total loss of
coral after the 1998 bleaching event; here recovery is predicted to be very slow.
MAIN PROBLEMS AFFECTING THE COASTAL ENVIRONMENT
Comoros
These islands experience both natural and anthropogenic disturbances, with the major
impact being the global warming in 1997-98 which caused extensive coral bleaching and
mortality in large areas, particularly to species of Acropora. The majority of reefs e.g. the
small islands of Nioumachouioi, are subjected to strong swells from Monsoons and
particularly from cyclones which destruct the more fragile corals, especially acroporids.
However, this damage was always within natural recovery capacity and is now insignificant
compared with anthropogenic degradations.
Blast or dynamite fishing is one of the major damaging factors, and is currently practised in
Moheli, where the entire reef flat bordering these small islands is covered with newly-broken
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