Perth: Western Australia’s world-famous coral reefs have experienced their most severe bleaching event on record following the state’s ‘longest, largest and most intense’ marine heatwave, scientists have confirmed.
Between August 2024 and May 2025, prolonged above-average sea temperatures caused unprecedented heat stress, causing coral to expel the algae that provide them with life and colour, a process known as bleaching, which is often fatal. The impact spans 1,500 km of coastline, affecting areas that had previously escaped the worst effects of climate change.
The Australian Institute of Marine Science (AIMS) said many reefs endured between 15 and 30 weeks of heat stress, far beyond the eight weeks typically needed to kill coral. AIMS researcher James Gilmour stated that, “The length and intensity of the heat stress, and its footprint across multiple regions, is something we’ve never seen before on most of the reefs in Western Australia.”
The bleaching has struck regions once thought more resilient, including the Rowley Shoals, north Kimberley, and Ningaloo. Gilmour remarked that, “Areas which had given us hope because they’d rarely or not been bleached before have been hit hard this time. Finally, climate change has caught up with these reefs.”
This event is part of an ongoing global coral bleaching crisis, driven by record-breaking ocean temperatures over the past two years. The full extent of the damage in Western Australia will take months to assess.
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