BRITISH divers are helping to develop a fresh way of transplanting coral grown in floating nurseries to restore reefs off the coast of Thailand damaged by the Boxing Day tsunami in 2004, writes Michael Sheridan.

The technique requires tiny fragments of coral to be grown in netted cages suspended in the sea, protected from grazing fish and strong currents. This improves the coral’s chances of survival.

The first crop has been transplanted onto badly damaged reefs at Koh Phai, a small island near the resort of Krabi on the west coast. The divers will now apply the method to other reefs off the islands of Phuket and Phi Phi, where thousands of holidaymakers died.

They have also created an artificial reef and may use specially designed concrete cylinders with many crevices to create beds for coral larvae to grow.

The teams adopted this method because they discovered that traditional “coral rehabilitation”, which involved sinking concrete blocks or marine wrecks offshore to allow coral to grow on them, did more harm than good in seas with strong currents, such as the Andaman Sea, and in waters with a high degree of sediment or pollution.

“Some rehabilitation work in the past unwittingly destroyed the reefs, partly due to inadequate knowledge of coral biology,” explained Nalinee Thongtham, the Thai marine biologist who heads the project. “Natural recovery of degraded coral reefs is only possible if coral seeds or coral larvae are still available in the area and environmental factors are right for the coral to regrow.”

She said the researchers discovered that in the wake of a storm the seabed is strewn with coral debris, easily tossed about by strong waves. In these conditions coral larvae have little chance of survival.

Benefiting from sympathy and attention after the disaster the Thais turned to Israel’s National Institute of Oceanography, which pioneered the new method in the Red Sea.

Six countries, including the UK, are now collaborating on the project. They have employed the local expertise of Andrew Hewett, a Briton who runs a diving school on Phi Phi, and who narrowly escaped the tsunami with his family. Two years on, he is enjoying the task of rebuilding the reefs that attracted many of his customers.

“One project is a floating coral nursery that is home to about 1,100 coral fragments,” he said. “This allows them to grow without additional pressure from predators, since the nursery floats about 16ft off the sea bottom and 16ft from the surface.” Later this month 300 divers will attend one of the largest coral planting dives ever held, to help transplant the coral fragments.

Foreign funding has paid for the creation of an experimental artificial reef, consisting of 100 concrete blocks, each 5ft square. “By using the concrete blocks we help reduce the damage caused by divers to natural reefs,” he explained. “At present our experienced divers are helping to stack the concrete blocks into pyramids underwater.” These blocks will become the home for the coral fragments, now growing in the floating coral nursery.

Although the concrete “reef” is less attractive than a natural one, the divers are confident that it will become an interesting dive site. “Already fish have taken up residence and are watching us as we lift the one-ton blocks into place,” he said.

For Hewett and many others who lost friends and colleagues in the tsunami the experiments are about much more than science. They offer a chance for the survivors to generate life in a place where so many lives were swept away.

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