SYDNEY - A sharp slowdown in coral growth on Australia's Great Barrier Reef since 1990 is a warning sign that precipitous changes in the world's oceans may be imminent, scientists said Friday.
Strong evidence points to the cause being a combination of warmer seas and higher acidity from increased levels of atmospheric carbon dioxide, Australian Institute of Marine Science researchers reported.
"The data suggest that this severe and sudden decline in calcification is unprecedented in at least 400 years," said Glenn De'ath, principal author of a paper published Friday in the international journal Science.
The research shows that corals on the reef have slowed their growth by more than 14 percent since the "tipping point" year of 1990 and on current trends the corals would stop growing altogether by 2050.
"It is cause for extreme concern that such changes are already evident, with the relatively modest climate changes observed to date, in the world's best protected and managed coral reef ecosystem," said co-author Janice Lough.
Coral skeletons form the backbone of reef ecosystems and provide the habitat for tens of thousands of plant and animal species and more acidic oceans will affect many sea creatures, not just coral, a statement on the report said.
"All calcifying organisms that are central to the function of marine ecosystems and food webs will be affected, and precipitous changes in the biodiversity and productivity of the world's oceans may be imminent," it added.
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The findings are based on analyses of annual growth bands -- like rings on trees -- extending back in time up to 400 years.
Rising sea temperatures are blamed on global warming caused by the build-up in the atmosphere of greenhouse gases such as carbon dioxide -- which is also blamed for higher acidity in sea water.
A UN report warned in 2007 that the Great Barrier Reef, described as the world's largest living organism, could be killed by climate change within decades.
The World Heritage site and major tourist attraction, stretching over more than 345,000 square kilometres (133,000 sq miles) off Australia's east coast, could become "functionally extinct", the report said.
The journal Science is published by the American Association for the Advancement of Science.