January 2, 2009

Great Barrier Reef Growth Slowing

Scientists said on Thursday that coral growth in Australia's Great Barrier Reef has fallen to its lowest rate for 400 years, in a troubling sign for the world's oceans.

Glen De'ath and colleagues at the Australian Institute of Marine Science believe the slow growth could threaten a variety of marine ecosystems that rely on the reef and signal similar problems for other similar organisms worldwide.

The Great Barrier Reef is the largest coral bed in the world, composed of over 2,900 individual reefs and 900 islands. Climate change and pollution are threatening coral reefs everywhere.

"These organisms are central to the formation and function of ecosystems and food webs, and precipitous changes in the biodiversity and productivity of the world's oceans may be imminent," the researchers wrote in the journal Science.

Coral reefs are delicate undersea structures resembling rocky gardens made by tiny animals called coral polyps, which are central to the formation and function of ecosystems and food webs for tens of thousands of other marine organisms.

The reefs are also important for the protection of coastlines. They provide a critical source of food for millions of people, attract tourists and are potential storehouses of medicines for cancer and other diseases.

The researchers looked at 328 massive porites corals from 69 reefs and found the skeletal records indicate that calcification -- or the deposit of calcium carbonate -- by these creatures has declined by 13.3 percent throughout the Barrier Reef since 1990.

Global warming and the increasing acidity and decreasing carbonate content of seawater is likely responsible for the decline, they wrote.

The researchers said verification of the causes of this decline should be made a high priority, as such a decline is unprecedented in at least the past 400 years.

The reefs cover about 154,000 sq miles of tropical ocean floor, but needs sustained sunlight, warmer waters and high levels of carbonate to flourish.

Australia's Great Barrier Reef is the largest collection of 2,900 reefs along 1,300 miles of Australia's northeast coast in a marine park the size of Germany.

Changes in biodiversity are imminent, both at the Great Barrier Reef and at other reef systems throughout the world's oceans, scientists said.


Image Caption: Satellite image of part of the Great Barrier Reef adjacent to the Queensland coastal areas of Proserpine and Mackay. (NASA)


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