Heat Stress and Rare Disease Wipe Out Goniopora Coral Colonies on Great Barrier Reef

Key facts

• Three-quarters of Goniopora corals at One Tree Reef have died after bleaching and black band disease.
• The losses occurred during the fourth global mass bleaching event, affecting 84% of reefs worldwide.
• Extreme heat weakened corals, enabling rapid, unprecedented spread of the disease.
• Goniopora are usually thermally tolerant, making the event a major warning for global reef resilience.
• Severe bleaching triggered by extreme ocean temperatures was followed by an unprecedented outbreak of black band disease (BBD).
• Black band disease (BBD) is a rare but aggressive bacterial infection that kills coral tissue as it spreads across a colony.
• Black band disease, common in the Caribbean but historically rare in the southern Great Barrier Reef, appeared in a few colonies in February 2024.
• By April, 61 per cent of bleached colonies were infected, and the disease spread in an epizootic-like manner.
• The disease occurred only on corals that had bleached.
• During the bleaching event, water temperatures exceeded 28°C for 74 consecutive days.
• Temperatures peaked at 34-35°C during the year.
• One Tree Reef’s (OTR) offshore location means it is largely sheltered from coastal stressors like pollution and nutrient loading, which are often associated with BBD.
• The current trajectory of climate change is progressing too quickly for corals to adjust.
• Recurrent anomalous heatwaves and mass bleaching are the greatest threat to coral reef survival.
• The loss of these large, structure-forming corals would have long-term repercussions on reef biodiversity, coastal protection and food security.