Larry's cool change good for reef

March 22, 2006

Coral reef at Heron Island. Photo: Ove Hoegh-Guldberg

Cyclone Larry has been a nightmare on land but underwater, it may have helped save the Great Barrier Reef from disaster. University of Queensland coral reef expert Professor Ove Hoegh-Guldberg said Larry's wind had cooled ocean temperatures that had skyrocketed this summer and threatened to bleach the corals of the Reef.

“Cyclones mix the water column and cool things down, so as we move into winter and with cyclones like this, the real threat of a major bleaching event has passed,” Director of UQ's Centre for Marine Studies Professor Hoegh-Guldberg said.

Professor Hoegh-Guldberg, who first identified widespread coral bleaching at the southern end of the Reef around the Keppel Islands in January, had feared more than 60 percent of the Reef might bleach as it did in 2002.

So far, he said about half of the coral in 1000 square kilometres of inshore reef from Mackay to Hervey Bay had bleached.

Prolonged coral bleaching can lead to coral death and the loss of coral reef habitats for a wide variety of marine life. This is a worry for scientists and reef enthusiasts because the Great Barrier Reef may house more than a million species.

Professor Hoegh-Guldberg said Cyclone Larry had left its mark on the land but the cyclone had moved too quickly across the reef to cause major damage.

“It was so intense and moved so quickly that it crossed the Great Barrier Reef in a matter of hours.

“In a way it's fortunate that it didn't linger and for that reason it's unlikely that it had major impacts on reef structure but we still need to do underwater surveys.”

He said the latest bleaching was the worst reef event since 2002 when the Reef around Townsville and Cairns was bleached. This time, bleaching only caused distress on the southern Great Barrier Reef.

UQ researchers are teaming up with NASA scientists to find out why different parts of the Reef have bleached in different events.

“It's prompting some very interesting questions about why it was so low on the Reef this year when it was so central in 2002.

“We're starting to do some projects here at UQ that are understanding how oceanography interacts with the geography of the bleaching.”

Source: University of Queensland