by V.S. Sambandan
COLOMBO, FEB. 5. They acted as a shield during Sri Lanka's worst natural disaster, but more than half of the coral reefs along the island nation's coastal waters are estimated to have been damaged in the December 26 tsunami.
"In several places they bore the brunt of the waves and dissipated the fury of the tsunami. They died like warriors on the battlefront, but lowered the damage on the coasts. They were the first line of protection," N. Sureshkumar, head of Environmental Studies in Sri Lanka's National Aquatic Resources Research and Development Agency (NARA) said.
Of the 680 sq km of the island's coral reefs "around 200 sq km to 300 sq km have been affected to varying degrees," Arjan Rajasuriya, a Research Officer at NARA's Coral Reef Research Project, said.
A preliminary study by NARA describes the impact of the tsunami on the corals as "highly varied." There was "almost total destruction" of the reefs at Dutch Bay, off eastern Trincomallee. The living component on the Dutch Bay reefs, which was nearly 52 per cent in 2003, had fallen to 12 per cent in January 2005, after the tsunami.
The "recently dead coral" — which had survived the tsunami, but had died owing to its after-effects — had increased from 3 per cent in 2003 to 10 per cent in 2005. "There is a possibility of continued loss due to sedimentation and other factors," Mr. Rajasuriya said.
The December tsunami was the second major attack on Sri Lanka's coral reefs, which were extensively damaged in 1998 in a round of coral bleaching, after a rise in the temperature of the seawater. "The reefs were just recovering, when the tsunami struck," he said. The two main causes for the current damage were "the debris of the 1998 coral bleaching and the impact of wave action."
The worst damage was to the fringing reefs, which are close to the coast, while the offshore reefs — largely concentrated in the Gulf of Mannar — were unaffected as that region was outside the path of the tsunami. The Dutch Bay in eastern Sri Lanka, which escaped the coral bleaching a few years ago, was badly affected in the tsunami.
The immediate impact of the destruction, Mr. Rajasuriya said, was "on the corals themselves" as "most of them are smothered with rubble and sediments." Attempts are also on to start removing non-biodegradable material from amid the corals through local efforts. "They are not lost forever," said a NARA scientist.
In some places, such as at Unawatuna on the southern coast, the seabed morphology had increased the tsunami's fury.
"Even there corals played the role of dissipaters of the tsunami. The impact of the waves could have been much more devastating but for the corals," Mr. Sureshkumar said.
Posted February 6, 2005