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What has happened, and where
Western Australia has experienced an unprecedented marine heatwave that drove the most widespread bleaching event ever recorded in the state.
Scientists report bleaching and mortality across roughly 1,500 kilometres of coral reef habitat, from Ashmore and Scott Reef through the Rowley Shoals and down to Ningaloo.
The Australian Institute of Marine Science confirms extreme heat stress and extensive coral death, with some sites recording mortality rates near 90 per cent[1].
The WA Coral Bleaching Group notes that Degree Heating Weeks, a measure of cumulative thermal stress, exceeded previously observed levels at multiple locations, including the Rowley Shoals[2].
Timing and intensity
The marine heatwave developed around August 2024 and persisted into May 2025 along the WA coast.
Researchers characterise it as the longest, largest and most intense heatwave on record for Western Australia, a scale that left little refuge for shallow or offshore reef systems[1][2].
Field teams and aerial surveys documented bleaching from the inshore Kimberley and Pilbara to offshore oceanic reefs, and at iconic Ningaloo sites such as Turquoise Bay and Coral Bay[5][6].
Why it is so severe this time
Sea surface temperatures around Australia in 2024 were the hottest on record, which primed reefs for bleaching when heat persisted into summer.
The Bureau of Meteorology’s annual statement shows Australian regional seas were about 0.89 degrees above the long-term average in 2024, a significant deviation that increases bleaching risk[3][7].
This local record heat overlays a global fourth mass coral bleaching event, confirmed by NOAA, in which about 84 per cent of the world’s reef area has experienced bleaching-level heat stress since January 2023[4].
Ningaloo, Rowley Shoals and other hotspots
Ningaloo, a World Heritage–listed fringing reef, had largely escaped past global bleaching episodes, but has now suffered widespread bleaching and coral death.
New reporting and footage indicate that shallow lagoon and back-reef habitats sustained severe damage, with bleaching documented at Bundegi, Tantabiddi and Coral Bay[6].
At the Rowley Shoals and other offshore reefs, scientists observed extreme stress, with sections showing very little live coral remaining after the peak heat passed[2].
Ecological and economic stakes
Coral reefs occupy less than one per cent of the ocean floor, yet support around a quarter of marine species, including fisheries that underpin regional livelihoods.
Bleaching does not always kill corals immediately, but it weakens them, slows growth and increases disease risk, which can cascade through reef food webs.
Tourism and coastal protection values at Ningaloo and other WA reefs are significant, and repeated heatwaves shorten recovery windows between disturbances[4][8].
Signals from monitoring and media
AIMS and partner agencies synthesised aerial and in-water observations to confirm statewide bleaching, using satellite heat-stress metrics and site surveys.
National broadcasters and independent outlets have reported on the scale and severity, highlighting that this is the worst bleaching on record for Western Australia.
Coverage emphasises the unusual breadth of the event and the high mortality at some sites, reinforcing the scientific assessments[1][5][9].
What comes next, and what can be done
Short-term management focuses on protecting remaining healthy patches, limiting local stressors such as pollution and overfishing, and supporting community science to track recovery.
Some experimental interventions, including assisted evolution and cloud brightening, are being explored, but these cannot substitute for emissions reductions at scale.
Scientists consistently conclude that stabilising global temperatures by rapidly cutting greenhouse gas emissions is the only viable path to preserve functioning coral reef ecosystems in Western Australia and globally[2][4].
How to follow updates
Check AIMS and the WA Coral Bleaching Group for technical updates on heat stress and survey results as spring approaches.
Follow NOAA Coral Reef Watch for near-real-time Degree Heating Week maps and seasonal outlooks that indicate when and where thermal stress may intensify.
Local conservation groups provide site-level reports and imagery that can help communities understand conditions at familiar beaches and reef lagoons[1][4][6].
References
- Australian Institute of Marine Science, “Worst bleaching event on record for WA coral reefs following long lasting and widespread marine heatwave.” aims.gov.au
- The Guardian, “WA’s longest and most intense marine heatwave killed coral across 1,500km stretch.” 12 August 2025. theguardian.com
- UNSW Newsroom summary of Bureau of Meteorology Annual Climate Statement 2024, “Australia’s ocean surface was the hottest on record in 2024.” 6 February 2025. unsw.edu.au
- NOAA Coral Reef Watch, “Current Global Bleaching: Status Update.” Updated 10 August 2025. coralreefwatch.noaa.gov
- International Coral Reef Initiative, “2024, 2025 Western Australia Bleaching Summary.” 12 August 2025. icriforum.org
- Australian Marine Conservation Society, “Ningaloo Reef suffers widespread coral bleaching, new footage shows.” 17 February 2025. marineconservation.org.au
- 9News, “Australia recorded hottest ocean surface temperatures on record in 2024, BOM says.” 6 February 2025. 9news.com.au
- The Guardian, “How a marine heatwave is threatening Australia’s spectacular coral reefs.” 14 August 2025. theguardian.com
- ABC News, “Western Australia’s ‘catastrophic’ bleaching event leaves parts of the Ningaloo Reef devastated.” 12 August 2025. abc.net.au