Heatwave, disease ‘catastrophic’ combo for hardy corals
A marine heat wave and the subsequent emergence of a rare, tissue-killing disease on the Great Barrier Reef wiped out typically heat-tolerant coral varieties.
Marine scientists say the combination of record heat and infection is “catastrophic” for the One Tree Reef region studied, suggesting tropical corals are struggling to withstand increasing pressures.
Goniopora, also known as potted or daisy corals, are long-lived corals that often bounce back after bleaching events caused by heat stress.
Monitoring of corals at the southeastern tip of the World Heritage-listed reef following unprecedented marine heatwaves in 2024 triggered by El Niño and global warming has revealed that 75 per cent of heat-tolerant Goniopora colonies have bleached.
The corals then contracted black band disease, more common in the Caribbean but unusual in Australian waters, which spread aggressively by April, infecting half of the bleached colonies.
Three-quarters of resistant coral colonies had died by October, and only a quarter had made a partial recovery
Bacterial necrotic infection forms a black band that crosses infected corals and often kills infested colonies.
It is often linked to pollution or nutrient runoff.
Queensland is a known hotspot for deforestation and land clearing in catchments draining into the Great Barrier Reef; This causes erosion, which washes debris into waterways, sending sediments, nutrients and pesticides downstream and into the ocean.
Study leaders Professor Maria Byrne and Dr Shawna Foo said the findings showed that climate change was happening too quickly for corals to adapt.
“Normally these huge corals are resilient to environmental stress, but the combination of record heat and infection was disastrous,” said Dr Foo, a lecturer in the university’s School of Life and Environmental Sciences.
Prof Byrne said the destruction of reef-building structural corals would devastate biodiversity, coastal protection and food security.
“Coral reefs support more than a billion people worldwide,” the marine biology professor said.
“Ambitious global action to reduce emissions is now the only way for them to survive.”
The world’s tropical reefs are the first climate-driven ecosystem to surpass the “tipping point” of irreversible decline, a report prepared by 160 researchers around the world ahead of this year’s COP30 climate summit suggests.
