Coral bleaching on the Great Barrier Reef is “major and significant”, federal Environment Minister Greg Hunt says.

Mr Hunt was commenting after he received his latest briefing from the Reef 2050 Independent Expert Panel about the current bleaching.

The Minister’s comments come as prominent naturalist Sir David Attenborough declared the reef to be in “grave danger”.

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“The event is still unfolding and the full extent and severity of bleaching may take several weeks to manifest,” Mr Hunt said.

He said the most severe bleaching had been observed between Cape York and Cooktown on the far northern part of the reef.

It has increased between Cooktown and Tully with moderate to severe bleaching listed.

“If major disturbances such as bleaching events occur more regularly, this will affect the reef’s ability to recover,” Mr Hunt said.

Of 520 reefs, only four showed no evidence of bleaching. Photo: Getty

Coral bleaching occurs due to increases in water temperature.

Bleaching can kill or stunt the recovery of the coral.

‘Twin perils threaten its very existence’

In a documentary being aired on the ABC this weekend, Sir David said while the reef had proven itself to be resilient, it was in “grave danger”.

“The twin perils brought by climate change, an increase in the temperature of the ocean and in its acidity threaten its very existence,” Sir David said.

“Do we really care so little about the Earth on which we live that we don’t wish to protect one of its greatest wonders from the consequences of our behaviour.”

The Great Barrier Reef Marine Park Authority is expected to release an update on the state of the reef in coming days.

Australian Institute of Marine Science chief executive John Gunn said while there had been bleaching across the northern reef, there has been some growth elsewhere.

“In the south, we’ve seen an almost doubling in the amount of coral that we last saw in 2012,” Mr Gunn said.

“From a really low base, it’s the worst conditions for the reef previously but it has rebounded quite excitingly.

“The centre of the reef has rebounded as well.”

But Mr Gunn said coral cover had dropped across northern sections of the reef.

“Largely we can see this is the result, as in 2012, of storms, bleaching and crown of thorns that are the primary killers of the Great Barrier Reef,” he said.

-ABC