13 December 2004

Warmer water may lead to coral growth - study

Coral reefs around the world could expand in size by up to a third because of increased ocean warming, according to a new Australian study which contradicts the long-held belief that global warming is destroying the reefs.

Previous research has predicted a decline of between 20 and 60 percent in the size of coral reefs by 2100 relative to pre-industrial levels because of increasing carbon dioxide levels caused by the greenhouse effect in ocean surface waters.

But the newly published research, by a team led by oceanographer Ben McNeil of Sydney's University of New South Wales, suggests that present coral reef calcification rates are not in decline and are equivalent to late 19th century levels.

"Our analysis suggests that ocean warming will foster considerably faster future rates of coral reef growth that will eventually exceed pre-industrial rates by as much as 35 percent by 2100," McNeil said in a statement on Monday.

"Our finding stands in stark contrast to previous predictions that coral reef growth will suffer large, potentially catastrophic, decreases in the future."

The research has been published in the latest edition of the journal Geophysical Research Letters by McNeil and colleagues Richard Matear of the government's Commonwealth Scientific and Industrial Research Organisation (CSIRO) and David Barnes of the Australian Institute of Marine Science, at Townsville in north-eastern Australia.

Experts say seawater surface temperatures and the quantity of carbonate in seawater dictate the growth rate of coral reefs which are built from calcium carbonate when red algae cement together a framework of coral skeletons and sediments.

The Australian scientists have observed the calcification-temperature relationship at significant reef-building colonies around the world in the Indo-Pacific and at massive Porites reef colonies in Australia, Hawaii, Thailand, the Persian Gulf and the South Pacific island of New Ireland.

They say the predicted increase in the rate of coral reef calcification is most likely due to an enhancement in in photosynthetic rates of red algae.

They used projections of ocean warming and Carbon dioxide concentration from a CSIRO climate model that accounts for atmosphere-ice and ocean carbon cycles.

A report released earlier this year by scientists at Queensland University found that the brightly coloured corals that make up the world-renowned Great Barrier Reef, one of the world's natural wonders, would be largely dead by 2050 because of rising sea temperatures.


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