Scientists warn of catastrophic coral bleaching on Great Barrier Reef

21/1/2025 10:36

The cycle of coral bleaching on Australia's Great Barrier Reef has hit catastrophic levels, experts have warned.

In a study published on Tuesday, a team of marine scientists from the University of Sydney tracked the health of 462 coral colonies in the southern part of the iconic reef over a period of 161 days during the 2023-24 global marine heat wave.

They found that 66 percent of the colonies had been affected by coral bleaching by February 2024. By April, that figure rose to 80 percent.

Coral bleaching is a phenomenon that occurs when coral experiencing heat stress expel the symbiotic algae living in their tissue, turning the coral completely white. Bleached corals are not dead but face an increased risk of mortality.

The new study found that 44 percent of the tracked colonies affected by bleaching had died by July 2024, with some types of coral experiencing a 95 percent mortality rate.

"Our findings underscore the urgent need for action to protect coral reefs, which are not only biodiversity hotspots but also crucial for food security and coastal protection," Maria Byrne, lead author of the study from the University of Sydney's School of Life and Environmental Sciences, said.

"The southern Great Barrier Reef, despite its protected status, was not immune to the extreme heat stress that triggered this catastrophic bleaching event."

Co-author Ana Vila Concejo said the findings should act as a "wake-up call" for policymakers and conservationists that the resilience of coral reefs is being tested like never before.

The Australian Institute of Marine Science (AIMS) in March 2024 confirmed that the reef was experiencing a mass coral bleaching event.

It was the fifth mass bleaching event on the Great Barrier Reef in eight years.