Corals suffer blow

Three months after the Indian Ocean tsunami, divers are still pulling mattresses and metal from the coral-lined bays of Thai paradise isles, although experts say overall reef damage is not that bad.

However, in other countries hit by the Dec 26 killer wave, the delicate "rain forests of the sea" have sustained injuries that could last for centuries.

"Corals grow very slowly, and many species suffered a blow on 'Black Sunday'. It will take them hundreds of years to acquire normal size again," said D.V. Rao of the Zoological Survey of India (ZSI).

Particularly hard hit were India’s remote Andaman and Nicobar islands, home to around 175 coral species, where surveys have showed silt stirred by the tsunami is choking the fragile ecosystems that attract thousands of tourists each year.

"Coral of this particular area did not suffer a direct blow from the tsunami, but the deposition of sand, mud and other debris due to the tsunami is threatening the corals," said the ZSI’s Jaya Bhaskaran.

On the southern Thai island of Phi Phi – the backdrop to cult Leonardo di Caprio movie The Beach – scores of backpackers and divers have started an ad hoc clean-up operation to rid the bay of the worst of the debris swept into the sea.

Despite a daily haul of anything from corrugated iron roofing to tailor’s dummies, dive operators are confident Phi Phi will retain its reputation as a mecca for lovers of the underwater world.

"There’s some great diving out there at the moment. The visibility is amazing," said Steve Goff, an English dive-shop owner on Phi Phi.

Scientists said other prime-time reefs in Thailand, where a government marine survey suggests only 13% of 174 sites had been severely affected, had also escaped the worst of the impact.

James Conley of Britain-based Coral Cay Conservation, which has just completed a study of the Similan Islands, a tropical chain 50km off the mainland, described overall reef damage as "pretty much insignificant at the archipelago level."

"Human disturbance from before has left far greater damage than the tsunami," Conley said. "The tsunami was the worst that nature could have thrown at the reefs, but they have bounced back," he said.

Others hope the monsoon season, which starts around May, will help stir up the water anew and wash tsunami sediment off the coral, allowing it to "breathe" more easily.

"Getting rid of sediment is not easy, but monsoon storms and currents can really help remove it," said Niphon Phongsuwan, a Thai marine biologist on the southern Thai resort island of Phuket.

In the remote Maldives archipelago 800km off the toe of India, coral reefs still recovering from severe damage suffered during the 1998 El Nino had a lucky escape.

The waters surrounding the idyllic chain of 1,200 tiny palm-fringed islands are home to 8,920 sqkm of reef – or around 5% of the world’s coral – and have helped turn the Maldives into a scuba diving paradise.

"While our reefs escaped direct damage, its fragility and sensitivity to even slight climatic changes warrants the implementation of additional measures to safeguard its health," said Maldives President Maumoon Abdul Gayoom.

A report compiled by the Australian Government found that while there was damage to coral and movement of sediments, they varied in intensity and overall tsunami damage to the Maldives’ reefs was relatively minor.

"However, the report has pointed out that the tsunami had unfortunately retarded the promising re-growth of our coral gardens after the 1998 El Nino bleaching incident," Gayoom added.