Ningaloo and Great Barrier Reef hit by ‘profoundly distressing’ simultaneous coral bleaching events

 Footage shows coral bleaching on Ningaloo reef as Great Barrier Reef hit at the same time – video

 Scientists say widespread damage to both world heritage-listed reefs is ‘heartbreaking’ as WA reef accumulates highest amount of heat stress on record

 Graham Readfearn

Great Barrier Reef

 Ningaloo
 

 

Australia’s two world heritage-listed reefs – Ningaloo on the west coast and the Great Barrier Reef on the east – have been hit simultaneously by coral bleaching that reef experts have called “heartbreaking” and “a profoundly distressing moment”.

Teams of scientists on both coasts have been monitoring and tracking the heat stress and bleaching extending across thousands of kilometres of marine habitat, which is likely to have been driven by global heating.

 

On the Great Barrier Reef, bleaching is being detected from around Townsville to the tip of Cape York, a distance of about 1,000km.

On Western Australia’s famous Ningaloo reef, waters have accumulated the highest amount of heat stress on record during an extended marine heatwave that has hit coral reefs all along the state’s vast coastline.

Paul Gamblin, the chief executive of the Australian Marine Conservation Society, said history would “record this profoundly distressing moment” when two world famous reefs both suffered widespread damage at the same time.

Corals begin to bleach at about 4DHW, and 8DHW can kill heat-sensitive corals. Scientists say levels up to 16DHWs have been detected on the Ningaloo coast. Photograph: David Juszkiewicz/Curtin University

Dr Zoe Richards, an associate professor and coral scientist at Curtin University, spent 10 days monitoring the health of Ningaloo reefs and the neighbouring Exmouth Gulf earlier this month.

She said in shallower areas known for their clear waters, which are popular with tourists, she had seen up to 90% of corals bleached and evidence of corals dying. Even slow-growing corals that were hundreds of years old were bleaching, she said.

Ningaloo last experienced widespread bleaching only three years ago.

 

The WA government, which is coordinating monitoring across reefs there, said bleaching had also been reported at Kimberley, Ashmore Reef, Rowley Shoals, Barrow Island, Dampier Archipelago, inshore Pilbara and Exmouth Gulf.

Richards said: “This isn’t isolated to Ningaloo – this is happening across the entire north-west shelf. There has never been this scale of impacts in WA. I am not aware of this ever happening before. Climate change has definitely caught up with the reefs in WA.”

Corals lose the algae that give them their colour and most of their nutrients if ocean waters get too warm. If bleaching is not severe, corals can recover, but studies show they are less able to reproduce and are more susceptible to disease.

Coral reef experts use a metric known as degree heating weeks (DHW) to show how much heat corals have accumulated. Generally, corals begin to bleach at about 4DHW, and 8DHW can kill heat-sensitive corals.

Dr Jessica Benthuysen, an oceanographer at the Australian Institute of Marine Science (Aims), first saw signs of heat accumulating in WA last August. By the end of December, she said, some areas had sea surface temperatures 4C hotter than normal.

Benthuysen said levels up to 16DHWs had been detected on the Ningaloo coast, which were the highest on record.

Bleaching at Lakeside Reef Front, Ningaloo. Paul Gamblin of the AMCS says scientists have warned of widespread damage from underwater heatwaves and cyclones to both reefs ‘for decades’. Photograph: Zoe Richards/Curtin University

Coral bleaching at Mesa Back Reef at Ningaloo in WA. Photograph: Chris Fulton/Australian Institute of Marine Science

The US government’s Coral Reef Watch says DHWs between 12 and 16 are enough to cause coral death across multiple species.

The federal government’s Great Barrier Reef Marine Park Authority has coordinated monitoring flights over northern reefs, finding low to high levels of bleaching on most reefs. Underwater checks found bleaching at 24 of 30 reefs surveyed.

Bleaching was worse farther north – there is no concern for reefs in the park’s southern section.

Last summer was the worst bleaching event on record for the reef and the fifth major outbreak in eight years, hitting all across the marine park.

Dr Neal Cantin, a coral reef biologist at Aims who was on the monitoring flights, said bleaching was generally worse closer to shore but there was “high to medium” bleaching on reefs from Cairns to the far north. He said in the far north, heat stress was between six and 13DHWs, which was “capable of causing mortality”.

Dr Roger Beeden, the chief scientist at the authority, said detailed analysis of the data from the flights was still being analysed, but he said the lack of recovery time for corals between major events was worrying.

“It’s the frequency as well as the severity that makes us most concerned,” he said.

Dr Emily Howells, a coral scientist from Southern Cross University who has been at the Australian Museum’s research station on Lizard island since February, said this was now the sixth summer in a row that bleaching had been seen there.

The island, in the north of the reef, was badly hit by bleaching last summer and scientists at Aims who visited in subsequent months said the area had lost one-third of its live corals due to the heat.

Howells said there was less coral mortality this year, “but that’s because a lot of the sensitive corals died last summer”.

“There just isn’t enough opportunity for these coral communities to bounce back. It’s heartbreaking,” she said.

“We’re making it more and more challenging for the corals. The solution is having stronger action on climate change. The longer we wait, the worse it will get.”

 

Northern parts of the Great Barrier Reef have also been heavily affected by flooding from torrential rains. James Cook University’s TropWATER group has recorded flood waters carrying sediments and nutrients in a plume across 700km of the coast and extending as far as 100km offshore.

Jane Waterhouse, a reef water quality expert at TropWATER, said major flood events appeared to be happening more often and flood plumes were reaching farther offshore.

“River discharge carries pollutants, sediments and nutrients,” she said. “You get muddy water that cuts the light that seagrass and corals need to grow, and that nutrient also allows algae to grow.”

Gamblin said the widespread damage from underwater heatwaves and cyclones to both reefs was “what our world-renowned scientists have been warning us about for decades”.

He said fossil fuel companies were “doubling down” to get more mega projects running, pointing to areas around Scott Reef in WA being targeted for expansion by Woodside.

He said: “More mega polluting projects up at places like Scott Reef will make a tragic situation worse. What will our children say to us?”

 

 

‘Catastrophic’: Great Barrier Reef hit by its most widespread coral bleaching, study finds

 

Rising water temperatures began to turn the corals of One Tree Island reef white in early 2024. Photograph: Sydney University

 

 More than 40% of individual corals monitored around One Tree Island reef bleached by heat stress and damaged by flesh-eating disease

 

More than 40% of individual corals monitored around a Great Barrier Reef island were killed last year in the most widespread coral bleaching outbreak to hit the reef system, a study has found.

Scientists tracked 462 colonies of corals at One Tree Island in the southern part of the Great Barrier Reef after heat stress began to turn the corals white in early 2024. Researchers said they encountered “catastrophic” scenes at the reef.

Only 92 coral colonies escaped bleaching entirely and by July, when the analysis for the study ended, 193 were dead and a further 113 were still showing signs of bleaching.

 

Prof Maria Byrne, a marine biologist at the University of Sydney and lead author of the study, has been researching and visiting the island for 35 years.

“Seeing those really massive colonies die was really devastating,” she said. “I have gone from being really sad to being really cranky. We have been trying to get the message across about climate change for ages.”

 

 

Shows mass coral bleaching on Great Barrier Reef amid global heat stress event 

 

In November the Australian Institute of Marine Science visited eight reefs in the same Capricorn-Bunker sector of the reef. They found the single largest annual decline in hard coral cover in that area since monitoring started in the mid-1980s, with coral cover dropping by 41%.

Similar falls in coral cover were also recorded by Aims scientists in parts of the northern section of the reef, where one government scientist has described seeing a “graveyard of corals”.

Corals at One Tree Island reef have suffered also from a flesh-eating disease known as black band. Photograph: Sydney University

Byrne and colleagues set up the study in early February last year. The team used temperature loggers, video and direct observations to track the welfare of 12 different types of coral.

The scientists wrote in the study: “As corals can recover from mild bleaching when water cools, there is a perception that while bleaching is bad, it is not necessarily catastrophic. What we observed at [One Tree Reef] was by contrast, catastrophic.”

One genus of coral – Goniopora, which is long-lived and forms large boulders covered by vibrant flower-like polyps – was observed bleached and then afflicted with a flesh-eating disease known as black band.

Byrne said it was the worst bleaching recorded at One Tree reef. The corals that were still white at the end of their study could recover, or could die, she said.

 

Dr Shawna Foo, a coral reef scientist at the University of Sydney and study co-author, has worked on the island for several years but said that after tracking the corals for five months “it was hard to recognise” many of the colonies, because they were either “covered with algae, dead or crumbling”

“It’s horrible to see this happen to somewhere I know really well but we were expecting this to happen because we have seen it in other parts of the reef, and other parts of the world,” she said.

March is usually the peak month for heat stress on the reef. The Great Barrier Reef Marine Park Authority said last week temperatures were currently up to 1.2C above average across most of the marine park.

 Great Barrier Reef suffering ‘most severe’ coral bleaching on record – video

 

The US government’s Coral Reef Watch program is projecting parts of the reef, north of Cooktown, will be subjected to heat stress and potentially more widespread bleaching by mid-February.

Richard Leck, the head of oceans at WWF-Australia, said: “We are yet to see the full data about last summer’s coral bleaching, but it’s clear there has been major mortality in areas from the north and this new research shows major mortality in the south.

“The reef is under more heat stress this summer, especially in the north, and there’s a risk we could see another back-to-back bleaching event. It’s a case of Russian roulette whether that occurs or not.

“We know the reef is under increasing pressure from climate change and its world heritage status is under increasing pressure.”

The Australian government has been asked by Unesco to report on the condition of the reef by early next month, and Leck said it was “vital an accurate representation of the reef’s health is given, and new and increased efforts to protect the reef are committed to”.