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Last Updated: Sunday, 23 January 2005, 00:31 GMT
Sri Lanka reefs 'survive tsunami'
Divers with rubble collected from coral reefs
Divers in affected areas have already been clearing reef debirs
Coral reefs around the coast of Sri Lanka may have suffered much less damage from the Indian Ocean tsunami than was initially feared, early surveys have suggested.

As well as causing so much loss of life and devastation on land, it was feared that the giant waves would have destroyed coral reef systems around the affected countries.

But marine biologists are now reporting that their first findings are that the situation is not as bad as feared.

"We have found some things that reflect the situation on land - and some things that don't," Jerker Tamelander, marine programme co-ordinator of the World Conservation Union in Sri Lanka, told BBC World Service's Science In Action programme.

"One thing is that damage is very patchy. It varies a lot, from one area to another, and it varies a lot within a certain area.

"A lot of the mechanical damage seems to have been caused by boats washing over coral reefs, and in turn pushing over large boulders, so there's very site-specific damage - whereas on the broad scale, the mechanical damage is much less."

Motorbikes and TV sets

Mr Tamelander has completed a survey of reefs of Sri Lanka's south-west coast, conducting a rapid assessment of environmental damage to coral reefs and sea-grass beds.

The area was badly affected on land, with "significant destruction" of terrestrial ecosystems. But in comparison, the underwater coral has not been so badly affected.

Satellite image of Kalutara on Sri Lanka's south-west coast
Sri Lanka's south-west coast was badly hit in the tsunami

Mr Tamelander explained that much of what damage there was had been caused by rubble depositing on the coral.

Some of this had come from material washed back from land - "including motorbikes and TV sets" - that resulted in "quite significant amounts of debris on several reefs".

But there had also been damage caused by rubble which dated back to a mass coral mortality in 1998, triggered by rising sea temperatures.

The damage from the mortality was taken up by the wave and deposited again - but again this was less than expected.

Mr Tamelander said that one of the reasons for the minimal damage was that the volume of water had been so vast that when the wave retreated, it washed the debris across the reef and then out into deeper water.

'Pleasantly surprised'

Meanwhile, the survey also analysed marine and fish populations - and again found that the tsunami had had little obvious effect.

While Mr Tamelander was unable to immediately say whether there was a clear change in fish populations, he said that the fish looked "reasonably normal, both in terms of species composition and abundance".

Bleached coral
Mass bleaching in 1998 produced debris that battered living reefs

However he warned there may be problems yet, with the potential destruction to fish habitats and nursery grounds.

"If coral reefs and mangroves and sea-grass beds are severely damaged, this will reduce the reproductive success of fish - quite significantly in many cases," he said.

He now plans to head to the eastern side of Sri Lanka, where there are coral reefs that survived the 1998 bleaching to a much higher degree.

The force of the tsunami was potentially greater there than in the south-west.

He said that so far, however, he was "pleasantly surprised" by what had been found in Sri Lanka and also the Gulf of Mannar, in India.

"There are reports of several reefs in Thailand that have also withstood the impact very well," he said.

"At the same time, we have as yet unconfirmed or unquantified damage that is quite severe - but this is quite preliminary, and we need broader surveys to say more."

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