Biologists fear they will now start to see coral mortality in world’s southern-most reef

This article is more than 1 year old

This article is more than 1 year old

Researchers have documented what they are describing as the most severe coral bleaching to hit the world’s southern-most reef at Lord Howe Island.

Scientists from Newcastle University, James Cook University, the University of New South Wales and the National Oceanic and Atmospheric Administration have spent the past two weeks surveying corals around the island in the far south Pacific Ocean after they were alerted to bleaching in isolated areas.

Bill Leggat, a coral biologist at Newcastle University, said the worst of the bleaching was in shallow water closer to the shoreline.

“It’s quite variable but where it’s severe it is actually quite severe,” he said.

“Some of the sites are looking at 80-90% bleaching going very close inshore.”

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Other reef sites the scientists surveyed showed bleaching levels of 50%, 30% and some areas with as little as 5% bleaching.

Lord Howe Island was named a Unesco world heritage site in 1982. It is habitat for species that are found nowhere else on earth.

The bleaching has occurred over the past summer, with March the peak month of the year for coral bleaching due to warmer ocean temperatures.

Scientists have documented three bleaching events at Lord Howe Island in the past but it has been some years since it last occurred.

Leggat said although the bleaching was isolated to shallow areas, for scientists to be documenting 90% bleaching in some parts signalled the latest event “is really quite severe”.

“As far as we know it’s the most severe we’ve ever seen it on Lord Howe Island,” he said.

“Our concern now is we’re going to start seeing coral mortality.”

Leggat said some areas still remained healthy but researchers doing surveys last week could see the bleaching was progressing.

They will return in April to conduct fresh surveys to assess whether it has caused coral mortality.

While much of Australia’s focus on coral bleaching has been centred on the Great Barrier Reef, it is a worldwide occurrence due to climate change.

“Reefs around the world are being affected everywhere,” Leggat said.

“We’re starting to see beaching in sites where wouldn’t have previously expected to see it.”