Massive decline in Great Barrier Reef corals

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Australian scientists have found that coral growth in the Great Barrier Reef (GBR) has severely and suddenly declined to its lowest levels in four centuries.

Glenn De'ath, Janice Lough and Katharina Fabricius have published the results of their findings in a recent issue of the journal Science.

The researchers investigated 328 colonies of massive Porites corals from 69 reefs of the GBR, studying their calcification rates by using standard x-ray and gamma densitometry techniques.

The authors found strong declines in coral calcification for the period 1990"2005, with a decline of 14.2% since 1990.

The causes for this decline in coral calcification remain unknown, but the authors believe the causes are large-scale and that the changes observed are unprecedented within the past 400 years.

Unprecedented declineLikely causes for the decline in coral growth and calcification include space, water quality, salinity, diseases, irradiance, currents, oceanographic changes, temperature changes and carbonate saturation.

The experts believe that competition between neighbouring corals is likely to have intensified when coral cover has either remained similar or declined on most GBR reefs.

The study claims that diseases are not to blame for the decline, nor is cloud cover, which hasn't changed significantly across the Great Barrier Reef during this period.

The experts believe that the most likely cause of the decline are changes in the sea surface temperature and carbonate saturation levels.

For more information, see the paper: De'ath, G, JM Lough and KE Fabricius (2009) Declining coral calcification on the Great Barrier Reef. Science 323. Pp. 116"119.