Great Barrier Reef's corals withstood Yasi, study finds

THE Great Barrier Reef withstood the destruction wrought by massive category 5 tempest Cyclone Yasi better than expected.

THE Great Barrier Reef withstood the destruction wrought by massive category 5 tempest Cyclone Yasi better than expected, with many of its delicate corals toughing out the monster storm.

The surprising results of one of the first comprehensive examinations of damage to north Queensland's inshore reefs will be delivered in Cairns today, at the world's major coral reef science meeting.

Marine geoscientist Chris Perry will tell the international symposium that for reefs in the direct path of February 2011's cyclone, the damage appeared to be short-term, patchy and mostly minor.

"Our expectations were we'd see enormous changes on the reefs," Professor Perry told The Australian yesterday.

"We anticipated significant overall changes in reef structure.

"The eye of the storm was enormous, the wind speeds were gusting in excess of 280km/hr and (there were) big storm surges.

"On land, phenomenal damage was done. On the reef, (the damage was) very variable and very interesting."

Professor Perry, from the University of Exeter in Britain, and colleagues from Australia and New Zealand had already studied the health of several north Queensland reefs between 2006 and 2009.

This meant that after Cyclone Yasi smashed into the region, the scientists had detailed baseline information to use as a comparison.

Professor Perry and his team revisited four reefs in August last year, including three off Mission Beach that Yasi ploughed directly over.

Mud, sediment and sand were washed from the coral reefs at Dunk Island and Lugger Shoal, but there was "no evidence of major changes" as a result of Yasi, Professor Perry said.

He said it was possible the reefs had been protected from the biggest waves by the geography of the coastline.

The worst damage was at the southern-most reef examined by Professor Perry's team at Halifax Bay, near Ingham, 120km south of Mission Beach.

"A lot of the big, massive corals on the reef flat have essentially stayed there, but there's been a pruning of all the branch corals ... now they're rubble sheets," Professor Perry said.

"There's broken-up sticks of coral."

The scientist said the surprising impacts of Cyclone Yasi had broader implications for future severe weather events.

"The intensity of cyclones is predicted to increase as the climate changes and the sea surface temperature warms up," Professor Perry said.

"This (Cyclone Yasi) is about as big an event as you can get and what it shows is that impacts on the reef are very difficult to predict."

The International Coral Reef Symposium, which has attracted more than 2000 top scientists to Cairns this week, has been held every four years since 1969.