Coral bleaching to become an annual affair

The Hindu , Thursday, October 04, 2007
Correspondent : K.S. Sudhi
KOCHI: Coral bleaching caused by climate changes may become an annual affair from 2040, posing serious threats to the coral population in the Indian waters, warn scientists.

Once bleaching becomes a regular affair, it will be difficult for the corals to recover and this will lead to its death. Eventually, the country may lose its coral cover by the second half of the century, say scientists of the Central Marine Fisheries Research Institute (CMFRI) who have studied the possible effects of climate change on the Indian coral reefs as part of an Indian Council for Agriculture Research project.

Major coral reefs exist in India in the Lakshadweep, the Gulf of Mannar, the Andaman and Nicobar Islands and the Gulf of Kutch and massive bleaching was reported in these areas in 1998 and 2002.

According to the scientists, bleaching is the rapid loss of pigmentation of corals caused by the expulsion of zooxanthallae, an alga found inside or attached to the corals. It is this alga that gives colour and nutrition to the corals.

The scientists say that the increase in sea surface temperature (SST) has become the villain for coral reefs. Corals are extremely vulnerable to an increase in the SST. If the SST increases by one degree above the threshold limit for corals and if the temperature rise persists for more than 15 days, the bleaching process will set in. In this case, it will also be difficult for the corals to come back to life.

A team of scientists of the Institute consisting of M. Rajagopalan, E. Vivekanandan and Rani Mary George have also projected the possible SST for the next century. It is found that the SST will exceed the thermal threshold for corals from 2030 to 2040 and the number of bleaching incidents will go up during this period, says Dr. Vivekanandan.

The rise in sea level, one of the outcomes of global warming, may also prove to be disastrous for corals. Once the sea level increases, the alga in the coral may find it difficult to get sunlight for survival. Corals are found mostly flourishing in shallow waters with a depth of around 20 metres. Once the water level increases, the penetration of sunlight will become less, affecting the growth and reproduction of algae, Dr. Vivekanandan said.

Global warming has also resulted in the sea water turning more acidic. An increased acidic level will result in the eroding of calcium deposits of which coral reefs are made. The loss of coral reefs will have far-reaching consequences as they support around one million marine organisms worldwide.

A large number of marine organisms also depend on corals for their food and shelter. The destruction of corals will certainly upset the structure and functions of the marine ecosystem, he said.

 
SOURCE : The Hindu, Thursday, 04 October 2007
 


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