Selective breeding offers hope for heat-stressed coral reefs

09 Jun 2025 – A groundbreaking study has revealed that selectively breeding corals can enhance their heat tolerance and offer a lifeline – albeit short term – for global reef systems in the face of escalating ocean temperatures fuelled by climate change.

Researchers from Minderoo Foundation, in collaboration with The University of Western Australia, James Cook University, the University of Bremen and Texas A&M, have successfully bred heat-tolerant corals at Ningaloo, a World Heritage-listed reef system off Australia’s north-west coast under increasing threat from marine heatwaves and bleaching events.

The study found that selectively bred coral offspring with at least one ‘parent’ from reefs in areas with warmer ocean temperatures had double the survival rate under extreme heat stress, compared to those corals from cooler areas.

“This marks the first successful demonstration of how selectively breeding Indian Ocean corals can boost heat tolerance and signals a crucial tool to aid reef survival in the short term,” Dr Andrew Forrest AO said.

“Of course, the only real and lasting solution to ending the destruction of coral reefs is the complete phase out of fossil fuels.”

In March 2025, for the first time ever, World Heritage-listed reefs on either side of Australia bleached in unison – Ningaloo in the west and the Great Barrier Reef in the east.

Mass global bleaching that began in 2023 has spread to at least 82 countries and territories, impacting almost 84 per cent of the world’s reefs.

“Coral reefs support the livelihoods of millions of people globally, provide critical shoreline protection and support more than a quarter of the ocean’s biodiversity, but have suffered steep declines globally,” Dr Forrest said.

“The world must arrest warming ocean temperatures urgently or face the very real prospect of the death of a majority of coral reefs globally within 50 years.”

The Minderoo-led study assessed the heat tolerance of two widespread reef-building Acropora species at Ningaloo. Researchers compared corals from two distinct locations along the reef: a warmer northern site, and a cooler southern site.

“We wanted to see if the small temperature differences between these two relatively close locations had resulted in corals with enhanced heat tolerances,” Dr Kate Quigley, a molecular ecologist and Principal Research Scientist at Minderoo Foundation, said.

“Coral babies with at least one parent from the warmer reef exhibited significantly higher survival rates under heat stress.”

Specifically, larvae with one parent from the warmer population doubled their ability to survive at very high temperatures of 35.5°C, compared to larvae only bred from parental corals from the cooler population.

“This is the first study to demonstrate that selective breeding can effectively enhance heat tolerance in corals within the Indian Ocean, effectively doubling their heat tolerance with this method in one critical species,” Dr Quigley said.

“These findings are crucial for developing strategies to protect coral reefs as marine heatwaves become more frequent and intense. It could provide us with time as we transition away from the use of fossil fuels, which are driving these extreme climate impacts.”

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