Status of Coral Reefs of the World 2000
Status of Coral Reefs of the World 2000.pdf
Status of Coral Reefs of the World 2000.pdf
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The 1997-98 Mass <strong>Coral</strong> Bleaching and Mortality Event<br />
Bleaching <strong>the</strong>n followed <strong>the</strong> path <strong>of</strong> <strong>the</strong> solar zenith in <strong>the</strong> far West Pacific from September<br />
to November 1998, in: <strong>the</strong> Federated States <strong>of</strong> Micronesia in September; and Palau in<br />
September to November when <strong>the</strong>re was unprecedented coral mortality.<br />
A consistent feature <strong>of</strong> <strong>the</strong> wea<strong>the</strong>r during all <strong>the</strong>se bleaching events was <strong>the</strong> coincidence<br />
<strong>of</strong> a major shift <strong>of</strong> <strong>the</strong> SOI away from zero, which apparently induced particularly calm<br />
wea<strong>the</strong>r. For example, in <strong>the</strong> Indian Ocean, <strong>the</strong> monsoon winds stopped almost<br />
completely, resulting in doldrum-calm conditions and weak currents. Under <strong>the</strong>se<br />
conditions sea surface waters warmed above <strong>the</strong> temperature tolerance limits for corals<br />
and o<strong>the</strong>r symbiotic animals, without mixing with cooler oceanic and deeper waters. Warm<br />
waters <strong>of</strong>ten extended down as far as 30m or more. <strong>Coral</strong> bleaching consistently started<br />
about 4 to 6 weeks after <strong>the</strong> passage <strong>of</strong> <strong>the</strong> solar zenith.<br />
A critical question remains; was <strong>the</strong> 1997-98 event a one-in-a-thousand year event killing <strong>of</strong>f<br />
large old corals, or will bleaching events like 1997-98 become more frequent and severe in<br />
<strong>the</strong> future? <strong>Coral</strong> bleaching and mortality levels were closely associated with <strong>the</strong> El Niño<br />
and La Niña switches in climate that started in 1997 and ended in early 1999, with large<br />
deviations in <strong>the</strong> SOI. Many scientists now predict that major climate change events will<br />
become more frequent and severe, resulting in greater bleaching. It is apparent that when a<br />
strong La Niña (positive SOI) coincides with <strong>the</strong> nor<strong>the</strong>rn summer, bleaching will follow;<br />
likewise <strong>the</strong> major trigger for bleaching in <strong>the</strong> sou<strong>the</strong>rn hemisphere is when a strong El Niño<br />
(negative SOI) occurs in summer. <strong>Reefs</strong> closer to <strong>the</strong> equator will probably experience<br />
bleaching under ei<strong>the</strong>r El Niño or La Niña conditions.<br />
Thus, <strong>the</strong>se predicted scenarios mean that coral reefs will change in structure over <strong>the</strong> next<br />
few decades with a major reduction in <strong>the</strong> branching and plate forming species that are <strong>the</strong><br />
fastest growers and major contributors to coral reef accretion. In <strong>the</strong>ir place, reefs will have<br />
a lower pr<strong>of</strong>ile <strong>of</strong> slow growing, massive species, with lower coral cover and lower<br />
diversity in <strong>the</strong> medium term. This will probably reduce <strong>the</strong> capacity <strong>of</strong> reefs to act as<br />
breakwaters for fragile shorelines and provide sand and rock as building materials on low<br />
islands. Fish populations will probably drop as <strong>the</strong>re will be reduced structural complexity<br />
to shelter juveniles and <strong>the</strong> many small species, but changes will be gradual. The impacts<br />
on tourism are harder to predict. <strong>Coral</strong> reef tourism, one <strong>of</strong> <strong>the</strong> fastest growing sectors <strong>of</strong><br />
<strong>the</strong> market, and growth will continue via <strong>the</strong> many tourists visiting coral reef destinations for<br />
<strong>the</strong> first time. The only adverse affects may be felt with those few tourists who revisit coral<br />
reefs for diving, and become disillusioned with large areas <strong>of</strong> dead corals. However, <strong>the</strong>se<br />
tourists will probably seek new experiences and go to <strong>the</strong> many areas that will escape<br />
damage in <strong>the</strong> immediate future. Surveys <strong>of</strong> many tourists indicate that many are unaware<br />
that <strong>the</strong> corals are dead, as <strong>the</strong>y focus on fish and above water activities in <strong>the</strong> tourist resorts.<br />
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