Amid an intense underwater heatwave, aerial surveys outlined on Friday have confirmed the Australia icon, tourism drawcard and world heritage-listed site is undergoing its seventh mass bleaching event since 1998 and its fifth since 2016.

The bleaching took place in 1998, 2002, 2016, 2017, 2020, 2022 and now 2024. Apart from heat stress, the world's largest coral reef is under threat from pollution and groundwater run off.

The surveys, conducted by the Great Barrier Reef Marine Park Authority in collaboration with scientists from the Australian Institute of Marine Science, spanned two-thirds of the marine park covering more than 300 reefs, from Cape Melville to just north of Bundaberg.

Ms Plibersek said the reef is going through a "tough time" and she said he was mindful that Australians, especially local communities and businesses along the Reef, will be concerned.

"We've had some bad news about the Great Barrier Reef," the minister said in a video posted to X.

"Our scientists have told us that we're facing a mass bleaching event. This is the seventh mass bleaching event since 1998. And it follows a lot of mass bleaching in the northern hemisphere summer."

The marine park authority said the mass bleaching off the east of Australia accords with similar reports from reefs around the world during the past 12 months as a "result of climate change-driven elevated ocean temperatures, amplified by El Nino conditions in the Pacific Ocean."

"Aerial surveys of the reef have revealed prevalent shallow water coral bleaching on most surveyed reefs and results are consistent with patterns of heat stress that has built up over summer," the authority said.

"Heat stress has not been even across the reef, and coral bleaching observed is variable.

"Bleaching of corals does not always result in coral mortality, with some corals being able to recover if conditions cool."

Environmental group WWF-Australia said five mass bleaching events in eight years show the pressure climate change is putting on the reef.

"WWF is very concerned that this bleaching event is unfolding in an area where corals have not been previously exposed to these extreme temperatures. Unless we see a significant drop off in temperatures in the next few weeks, the risk of significant coral mortality is high," said WWF-Australia Head of Oceans Richard Leck.

After heavy government lobbying, the Great Barrier Reef narrowly avoided an 'in danger' listing last year on the UN's list of World Heritage sites, with UNESCO noting the Albanese government having taken positive steps to protect the reef.

However, it warned it was still under "serious threat" and Australia was granted more time to report back on how these threats are being addressed.

The Greens and the Australian Conservation Foundation have called on the Albanese government to stop approving coal and gas projects.

"Coral bleaching is caused by excessive ocean heat, which is being fuelled by the continued burning of fossil fuels - coal, oil and gas," said ACF's CEO Kelly O'Shanassy.

Greens senator Peter Whish-Wilson has described it as "an underwater bushfire" ripping through the reef with Labor "pouring petrol on it" with coal and gas projects.

"The only thing that will save the Great Barrier Reef is an end to fossil fuels," he said.

The minister said climate change is the biggest risk to the reef.

"We've legislated to reach net zero, with a 43 per cent emissions reduction target by 2030 and committed to reaching 82 per cent renewable energy by 2030," she said.

"And we're investing a record $1.2 billion in the reef including to ensure we have the best science on reef adaptation and resilience.

"We need to act on climate change. We need to protect our special places and the plants and animals that call them home. And that is exactly what we are doing."

There are further aerial surveys in the pipeline.