Status of Coral Reefs of the World 2000

Status of Coral Reefs of the World: 2000
CASE STUDY 6: 1998 CORAL BLEACHING IN THE MESOAMERICAN BARRIER REEF
SYSTEM (MBRS)
This region experienced fewer large-scale bleaching events compared to other areas in
the Western Atlantic until recently. While coral bleaching was reported for much of the
Caribbean during 1983 and 1987, the first well-documented mass bleaching event in
Belize occurred in 1995 where 52% of coral colonies bleached, although only 10% had
partial mortality with a loss of 10-13% of coral cover. The 1995 bleaching also
affected Cayos Cochinos, Honduras, where 73% of scleractinian corals and 92% of
hydrocorals bleached and slightly higher mortality was reported. A less severe bleaching
event was reported in 1997, with little reported damage. However, during 1998, high
sea-surface temperatures first appeared in the region during August and intensified
during September. Reports soon followed of intense bleaching (more than 50% of
colonies) in the Yucatan in August-September, and then in Belize (September) and
Honduras (September-October). The first coral mortality was seen in the Yucatan in
early October, particularly on Agaricia tenuifolia colonies, where large scale mortality of
A. tenuifolia and Millepora spp. was seen in the central and southern Belize barrier reef.
Water temperatures decreased with the passage of Hurricane Mitch in late October,
and some branching corals started to recover, although massive corals remained
bleached into 1999. Extensive surveys showed that the 1998 bleaching event was
more severe than that in 1995. Shallow reef corals either died immediately or
recovered more rapidly compared to deeper depths, where recovery from bleaching was
slow, and significant remnant bleaching was observed up to 10 months later. Specific
findings from this study showed:
• An average coral mortality of 18% on shallow reefs and 14% on fore reefs
across the region;
• Up to 75% recent coral mortality occurred on localised patch and barrier
reefs in southern Belize;
• The highest mortality was on A. tenuifolia (>35%), M. complanata (28%),
and Montastraea annularis complex (25-50%)
• There was high recent mortality and disease on Montastraea annularis in the
region;
• There were low to moderate levels of bleaching mortality in Acropora
palmata;
• Remnant bleaching was still evident on fore reefs 10 months later (up to
44% of corals bleached); and
• A high incidence of coral disease afterwards on Belize shallow reefs (black
band) and Honduras and Belize fore reefs (white plague).
Caribbean and Atlantic Ocean
Bleaching in the Caribbean did not follow a clear pattern and varied across the region. Even
in areas where bleaching was severe, mortality was generally low, except when Hurricane
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