Marine heatwave cause of mass fish deaths and coral bleaching
Western Australia officials have linked more than 30,000 dead fish washing up on Gnoorea Beach to an extreme Category Three marine heatwave that is predicted only to worsen in the coming months while coral bleaching in the region intensifies.
An escalating marine heatwave has been identified as the cause of worsening fish kill events in Western Australia’s Pilbara, as coral bleaching events across the Kimberley, an area recognised as one of the world’s most precious wilderness regions, intensify.
The Department of Primary Industries and Regional Development has, this week, linked more than 30,000 dead fish washing up in recent weeks on Gnoorea Beach with an extreme Category Three marine heatwave event that is predicted only to worsen in coming months.
Authorities have issued a statement, sharing their belief that the climate change-driven marine heatwave is the ‘most likely cause’ of mass fish deaths off the WA coast. Experts say it is reminiscent of one of the most severe marine warming events ever recorded in the state.
The event occurred as a coral bleaching event has been unfolding since late last year in the Kimberley, where two reefs near Broome – Entrance Point reef and Coconut Wells reef – have bleached coral, due to highly elevated ocean temperatures at around four to five degrees above normal in recent months.
With the two events pointing at the stark reality of the increasingly damaging effects of climate change and a warming marine space, officials at the Western Australia Conservation Council warn that the region’s oceans are now “the new frontline” in an escalating climate crisis being driven “by fossil fuel extraction”.
Despite the mounting evidence and carbon emissions showing a recent uptick in activity, the conservation group has chastised those in the regional government enabling the expansion of the fossil fuel industry in the area.
“It’s critical that the next WA state government phases out fossil fuels and passes laws to limit climate pollution in line with international obligations,” said Mia Pepper, campaigns director at the Conservation Council of WA.
“It’s a tragic irony that thousands of dead fish are washing up on a beach just down the coast from Woodside’s Burrup Hub, the largest gas plant in the Southern Hemisphere, which the WA government just approved until 2070, by which time it would emit 6 billion tonnes of CO2, and consign our coral reefs to the history books.

Campaigns have been launched recently to halt plans made by the Australian energy company, Woodside, to drill more than 50 gas wells around Australia’s Scott Reef, an area home to some of Australia’s most important and biodiverse coral reefs. It’s an area that supports more than a thousand species, including reef-building corals and fish, endangered turtles and sea snakes, and migratory whales.
“It’s alarming that Woodside is seeking approval to drill Browse gas from underneath the precious and fragile Scott Reef, whose endangered turtles, whales, and sea snakes are now also at risk from ocean heatwaves directly driven by WA’s toxic gas industry.”
Earlier this month, some 30,000 fish washed up dead at Gnoorea Beach, around 1,500km north of Perth. Officials at the Department of Primary Industries and Regional Development (DPIRD) have since linked the event to a severe marine heatwave first detected in September last year. At the time, it was declared a ‘moderate heatwave’ but conditions worsened.
“It’s possible that prolonged thermal stress due to the ocean conditions is associated with the fish kill,” said a DPIRD spokesperson, Nathan Harrison.”Following the recent tropical cyclone, the marine heatwave strength has declined. However, we are moving into the higher-risk summer months.”
Sea surface temperatures in the region are currently between four to five degrees Celsius above the long-term average in the north coast bioregion and between two to three more in the Gascoyne bioregion. The Bureau of Meteorology now expects marine heatwave conditions to continue throughout January and February.
A study published in Environmental Research Letters this week has detailed unprecedented ocean temperatures across 2023 and 2024, during which ocean surface temperatures warmed four times faster than in the 1980s. While ocean temperatures were found to be rising at around 0.06 degrees Celsius per decade some forty years ago, today they are increasing at 0.27 degrees Celsius per decade.
In 2023 and 2024, global ocean temperatures hit record highs for 450 days straight. Some of that warming has been attributed to the natural warming event of El Niño in the Pacific, the rest, however, has been put down to warming sea surface temperatures. According to researchers, 44% of the record warmth was attributable to the oceans absorbing heat at an accelerated rate.
These temperature rises have contributed in no small way to the fourth mass coral bleaching event of recent years, impacting even in areas where corals are known for their robustness.
“Kimberley corals are known to be the most robust in the world and can withstand temperature ranges much more than corals elsewhere, but fragile ecosystems like the remote and precious Scott Reef are now at risk,” said Environs Kimberley Executive director, Martin Pritchard.
“70-90% of corals are predicted to die worldwide if temperatures remain at 1.5°C above pre-industrial levels. We are really concerned about the lack of any action or response from the Cook government to the dying coral reefs. It looks like they’re prepared to sign their death warrant by allowing the opening of new oil and gas frontiers like Woodside’s Burrup Hub and fracking in the Kimberley.”
IPCC scientists have warned, meanwhile, that should human-induced climate warming continue and fossil fuels not phased out, marine heatwave intensity, duration, and extent will continue accelerating “until much of the tropical Indian ocean is an almost permanent marine heatwave.”
Bill Hare, the ceo of Climate Analytics and a lead author of previous IPCC reports, said: “Phasing out fossil gas is critical. We need to cut carbon emissions to zero by 2050, yet gas companies like Woodside are set to continue pumping out gas from beneath WA’s coral reefs, under threat from these heatwaves, all the way to 2070, decades past our chance of keeping warming to 1.5°C.”

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