The long term effect of coral bleaching on coral reefs
The plight of
The group of international and local scientists, led by Mr. Nicholas Graham from the
Coral bleaching occurs when the seawater temperatures rise above normal limits, which in the
The research showed that, while the 1998 event was devastating in the short term, the main long-term impacts are down to the damaged reefs being largely unable to reseed and recover. Reseeding of coral reefs with new coral larvae has been one of the main limiting factors that have affected the recovery of reefs in the inner islands. The 1998 bleaching event killed more than 90% of corals in the inner islands. With very little live corals remaining after this event, compounded with the islands’ isolated location, far from other major coral reef systems, the low amount of larvae that are being produced is resulting in the slow recovery that is being presently observed. With such low coral cover many of the reefs are simply collapsing into rubble which becomes covered by unsightly algae.
The current findings follow the publication of an article in 2005 in the Coral Reef Degradation in The Indian Ocean Status Report by scientists from the Seychelles Centre for Marine Research and the Department of Environment in which they showed that more than 60% of the carbonate reefs being monitored in the inner granitic islands are undergoing degradation or recovering very slowly.
The collapse of the reef structure is also impacting the reef fish population. Four fish species (a type of butterfly fish, two types of wrasses and a type of damsel fish) that were found in 1994 were not observed in 2005 and are thought to have become locally extinct. Additional 6 fish species (a type of file fish, three types of butterfly fish and two damsel fish) were found to be at critically low levels, threatening the survival of the population. The 2005 surveys have shown that the diversity of fish at heavily affected sites has reduced by as much as 50%.
General scientific opinion believes that mass coral bleaching events such as that observed in 1998 will become more frequent and that by 2036 it may become an annual event. At such rates many corals will more than likely become locally extinct. The impact of these repeated coral bleaching events will be felt even more so when the height of the reefs reduces and bigger waves make their way to the shore line causing increased coastal erosion and damage to coastal properties.
Local scientists point out that the world wide coverage of the study is also attracting global scrutiny of the measures
(Department of Environment &