Wednesday 7 December 2005

As the mercury rises so too does the possibility of coral bleaching, according to a north Queensland expert on climate change impacts on coral reefs.

Great Barrier Reef Marine Park Authority (GBRMPA) Climate Change Response Programme Manager, Paul Marshall, said there was a direct link between elevated water temperature and coral bleaching.

“Corals become stressed when water temperature increases 1.5-2 degrees celsius above the normal summer maximum. This causes coral to lose microscopic algae living in their tissue, causing the corals to turn bright white,” he said.

“A lot of the corals’ energy and colour comes from the algae. If hot conditions persist, then bleached corals are unable to regain their algae causing starvation and death.”

Dr Marshall said corals normally ranged from brown and green to yellow, blue and even pink.

“Bleached corals appear extremely pale or bone white. A bleached coral is still alive, but the loss of algae in the tissue renders it nearly transparent, revealing the bright white skeleton beneath. If temperatures stay warm enough for long enough, then the corals will die.”

Dr Marshall encouraged reef users to report any coral bleaching through GBRMPA’s online BleachWatch programme.

“The GBRMPA relies on the many and varied reef users to help identify coral bleaching incidents, enabling us to learn more about when and where bleaching occurs,” he said.

“All reef visitors can report coral bleaching online through the BleachWatch website, recording information on reef condition and bleaching observations.

“It takes a few minutes to fill out the reporting form, but reports like these play a vital role in detecting the onset and assessing the spatial extent and severity of bleaching.”

The last mass bleaching events occurred in 1998 and 2002, affecting over 60 per cent of the Great Barrier Reef. Up to 5 per cent of reefs suffered greater than 50 per cent coral mortality in each year respectively.