Mass coral bleaching event stretching to waters off Brisbane alarms marine scientists

southern end of the World Heritage-listed reef and large patches of white coral have been seen further south.

Divemaster Steve Clarke says corals have been under stress recently due to warm ocean temperatures.(ABC Wide Bay: Johanna Marie)

Steven Clarke, who has been diving off the Bundaberg coast for 12 years, said the ocean has been unusually warm in recent weeks, reaching up to 31 degrees Celsius.

He has observed changes to the coral and marine life at popular dive sites off Bargara including Barolin Rocks and Nudibranch Park.

“It’s basically just white coral. It’s not all the corals, but there are patches, lots of patches. It’s really sad to see,” Mr Clarke said.

But damage has also been seen further south off Hervey Bay too.

An underwater photo of corals that are turning white from heat stress

Breannah Mitchell is urging others to volunteer with the marine monitoring group.(ABC Wide Bay: Lucy Loram)

Breannah Mitchell, an ambassador with citizen science program CoralWatch based at the University of Queensland, said she was shocked to see the bleaching so far south.

“Bleached coral doesn’t mean that the coral is dead. It means that it’s actually starving to death,” Ms Mitchell said.

“It does have some time to recover. But if the water stays warm the coral will die.”


Warming oceans

Bleaching happens during marine heatwaves when coral becomes stressed and expels their zooxanthellae — single-celled algae that live within coral tissues and provide them with nutrients and colour.

CoralWatch project manager Diana Kleine said the bleaching observed off Bundaberg, Hervey Bay, and Moreton Bay was “related” to the current mass coral bleaching event on the Great Barrier Reef.

“We call a coral bleaching event a ‘mass coral bleaching event’ when several management areas experience severe bleaching,” she said.

“A mass bleaching event is related to climate change as oceans and land are getting warmer every year, and this trend of warmer water is causing more severe and more frequent bleaching.

“The best thing that we can do to reduce our global warming, and which will cause ocean temperatures to drop, is reducing carbon emissions.”

An underwater photo of corals that are turning white from heat stress

Ms Mitchell says she’s seen “dramatic changes” on the reef over the last 12 years.(Supplied: Hervey Bay CoralWatch)

University of Queensland professor of marine science John Pandolfi said thermal stress was starting to impact coral reefs all the way south to Moreton Bay, including Flinders Reef and Peel Island.

“There’s very, very high thermal stress going on in the bay right now and it hasn’t yet peaked,” he said.

“The longer that the thermal stress occurs and the longer that the algae are expelled from the tissue of the coral, the less chance the coral has of recovering.”

An underwater photo of corals that are turning white from heat stress

CoralWatch says corals off Bundaberg are suffering from thermal stress.(Supplied: Hervey Bay CoralWatch)

No green zone

The Great Barrier Marine Park Authority (GBRMPA) is conducting extensive monitoring of the fifth bleaching event across the World Heritage Site in eight years.

But Professor Pandolfi said reef zone monitoring was mostly done outside the park by university researchers and volunteers with programs like CoralWatch.

A person snorkeling underwater holding a camera

CoralWatch engages volunteers in coral health monitoring and publishes the survey data online.(Supplied: Hervey Bay CoralWatch)

He said that has led to a lack of data to understand what the true, widespread effects of the thermal stress really was.

“I think it would be good if the government could step up and start providing other funds on a continuous basis,” he said.

“So that we could really understand what the benthic ecology is of these coral reefs in the lead up to bleaching events and then afterwards.”

Ms Mitchell agreed.

“There has never been any data collected in Hervey Bay on the coral reefs here,” she said.

“The reefs that we have in Hervey Bay aren’t protected, there isn’t a green zone.”

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