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  The Australian 4 Aug 07
Coral bleaching as record cold hits Great Barrier Reef
 Matthew Warren, Environment writer

A RECORD cold snap across southern Queensland has triggered coral bleaching normally associated with the extremes of hot weather linked to climate change.

Scientists say the bleaching has been caused by a combination of cold waters, winds and air temperatures hitting exposed reefs around the Capricorn-Bunker group of islands at the southern end of the reef.

While other sections of the reef appear to have been spared by being fully submerged or far enough north to avoid the worst of the cold snaps in June and July, bleaching has been recorded by University of Queensland researchers on Heron Island, near Rockhampton.

The area is regarded as having some of the most pristine sections of accessible reef.

Coral expert Ove Hoegh-Guldberg, from the University of Queensland's Centre for Marine Studies, warned researchers along the reef to look for bleaching after Townsville experienced one of its coldest days on record, on June 20.

Strong and sustained southerly winds that brought heavy rain to much of southeast Queensland in June and July exacerbated the chilly conditions for coral exposed at low tide and weakened the algae on the coral needed to keep it healthy.

Professor Hoegh-Guldberg said the comfort zone for coral was between 19C and 27C but temperatures had fallen to 8C.

While bleaching from extreme heat affects entire reefs, the cold bleaching appears to be isolated to the tips of wide areas of coral exposed to the chill.

Professor Hoegh-Guldberg said the extreme variation in temperature might be more common as climate change caused hotter summers and colder winters.

CSIRO oceanographer David Griffin said the only noticeably cold currents were further south, around Fraser Island, suggesting water was being cooled at the surface by the air temperature.
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