Coral bleaching in the Andamans

Reef rip-off in Andaman
Tapa Chakraborty The Telegraph Calcutta 31 Oct 10;

Oct. 31: An unusually hot summer and a delayed monsoon have combined to play havoc with one of the Andamans’ biggest tourist attractions: the multi-coloured coral reefs.

Some 80 per cent of the reefs up to a depth of 5-10 feet — the part visible from the shores and tourist boats — have decayed beyond recovery, a study by the Zoological Survey of India (ZSI) and the National Coral Reef Research Institute have found.

The reason is “bleaching” of the reefs by overheated seawater this summer — a process worsened by the rains’ late arrival.

Bleaching is a process in which reefs turn white or pale because the zooxanthellae — the symbiotic algae living within the corals’ tissues that give them their colour — are expelled owing to stress caused by a hostile environment.

Bleached coral can often recover over time, as the Andamans’ reefs themselves had recovered after a period of bleaching in 1998.

“But this time, between 60 per cent and 88 per cent of the coral reefs under five to ten feet of water are all gone. There is no chance of their revival now,” senior ZSI marine biologist C. Raghunathan told The Telegraph over the phone from Port Blair.

The Andamans are among the few spots that offer tourists both a tropical rainforest and coral reefs.

The reefs, often just 10-20 metres from the beach, are clearly visible from land, provide a habitat for thousands of marine species, and also protect the coast.

Their combined length around the islands in the region is about 14,700km, according to a United Nations estimate.

With the reefs bleached and dying, the colourful fishes swirling around them will be gone too. The healthier parts of the reefs are now under 15 feet of water — too far down for the tourists to see unless they dive in with scuba apparatus.

“The corals have lost their lustre and turned off-white and pale brownish. You can’t bear to look at them now,” said Raghunathan, who had been part of the survey by 20 ZSI scientists, conducted from August this year.

“Of the total 446 species of coral reefs in the Andamans, 120 have perished. Unfortunately, the largest reef formations in the Andaman Sea belong to these 120 species; they formed the largest segment.”

Scientists rued that the reefs, one of the richest marine ecosystems in South Asia, had survived the December 2004 tsunami only to fall prey to global warming.

Coral reefs survive well in a marine water temperature of 22 to 28 degrees Celsius. This summer, the temperatures had risen above 33 degrees and this had continued till June.

Growing water temperatures have been bleaching and threatening coral reefs at many places in the world, especially the region between the Andamans and northwestern Indonesia, for several years.

In May this year, P.M. Mohan, head of Pondicherry University’s department of ocean studies and marine biology, had sounded the alert about the coral bleaching in the Andaman Sea.

“We had initially thought the monsoon would halt the process of decay, but a delayed monsoon compounded the reefs’ plight,” Mohan said over the phone.

“The damage to the reefs under five-foot-deep water is there for everyone to see. The reefs look ghostly. If you go deeper, the gradations of decay is relatively less,” he added.

“All we can do is pray that the summer is not this blistering next year and that the monsoon arrives on time.”

The reefs have been affected across the Andaman Sea, those worst hit being located in northern Andaman and southern Nicobar, Mohan said. Reefs have been damaged also near the smaller islands such as Tarmugli, Jolly Buoy, Neil and Havlock Island and Red Skin Island, which form part of the Mahatma Gandhi Marine National Park and the Rani Jhansi Marine National Park.

Scientists now fear for the thousands of fish and other marine creatures that live in and around the coral reefs, using them as habitat and a place for hiding, feeding and reproduction.

Andrew Baird, an Australian reef expert from James Cook University, has noticed widespread coral decay in Thailand, Myanmar and Indonesia this summer.

Referring to this, Stuart Campbell, director of the Wildlife Conservation Society’s Indonesia Marine Program, recently wrote: “It’s a disappointing development, particularly... (because) these same corals proved resilient to other disruptions to this ecosystem, including the Indian Ocean Tsunami of 2004.”
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