Bleach Prospects for Reef Recovery

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Science  09 Jun 2006:
Vol. 312, Issue 5779, pp. 1442-1443
DOI: 10.1126/science.312.5779.1442d

Coral bleaching, whereby corals lose their photosynthetic algal symbionts, is now widespread throughout tropical reefs. Loss of algae from corals severely reduces nutrient flow through these ecosystems, with worrying impacts on the diversity and biomass of other reef-dwelling organisms, especially fish. Evidence is fast accumulating that warming events trigger these events. Less is known, however, about the ability of reef communities to recover from bleaching. Graham et al. assessed the changes that took place after the bleaching of 75 to 90% of coral in the Seychelles in 1998, the result of a strong El Niño event that year. A total of 50,000 m2 were surveyed. The structure of the reef habitats changed markedly after the death of branching and soft corals. By 2005, the structural complexity of the reefs was reduced, and the habitats were dominated by rubble, encrusting corals, and algal fields. There were concomitant reductions in fish diversity, including some local extinctions. The recovery of the reefs has been slower than typically observed in more-continental reefs, probably because of the isolation of the Seychelles, which would reduce the rate of dispersal of larvae from elsewhere. If bleaching events are regular, the prospects for recovery are not good. — AMS

Proc Natl. Acad. Sci. U.S.A. 103, 8425 (2006).

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