Climate extremes triggered rare coral disease and mass mortality on the Great Barrier Reef
Findings suggest climate change is happening too quickly for corals to adjust.
image:
Lead author Professor Maria Byrne from the University of Sydney on the Great Barrier Reef.
view moreCredit: The University of Sydney
University of Sydney marine biologists have identified a devastating combination of coral bleaching and a rare necrotic wasting disease that wiped out large, long-lived corals on the Great Barrier Reef during the record 2024 marine heatwave.
The study, led by Professor Maria Byrne and Sydney Horizon Fellow Dr Shawna Foo, found that bleaching triggered by extreme ocean temperatures was followed by an unprecedented outbreak of black band disease that killed massive Goniopora corals, also known as flowerpot or daisy coral, at One Tree Reef on the southern Great Barrier Reef.
“This research shows that the compounding impact of disease – which appeared after the onset of bleaching – is what killed the Goniopora. These are very long-lived corals that would normally survive bleaching,” said Professor Byrne, a professor of marine biology in the School of Life and Environmental Sciences.
Their study is published today in Proceedings of the Royal Society B.
Black band disease is a bacterial necrotic infection that invades living coral, forming a black band that crosses the infected coral, usually killing the colony. Common in Caribbean reefs, it is rare in Australian waters.
The 2024 El Niño brought the highest sea temperatures on record to the Great Barrier Reef, with marine heatwave conditions persisting for months. During this period, 75 percent of Goniopora colonies at One Tree Reef bleached. Initially only a few (4 percent) showed signs of black band disease. By April, however, the disease had spread aggressively, invading more than half the bleached colonies.
Tracking 112 tagged Goniopora colonies over a year, the team found that three-quarters had died by October 2024, while only one quarter showed partial recovery. Population surveys of more than 700 colonies revealed the same pattern: widespread bleaching, rapid disease progression and high mortality.
Black band disease has been known for decades in the Caribbean, often linked to pollution or nutrient runoff, but it is extremely rare on the Great Barrier Reef. Its sudden appearance in One Tree Reef’s pristine waters marks the first recorded epizootic (an animal epidemic) event of this kind on the Great Barrier Reef and demonstrates how heat stress can turn even resilient coral species into disease victims.
“Normally these massive corals withstand environmental stress, but the combination of record heat and infection was catastrophic,” said Dr Shawna Foo, an ARC DECRA Fellow in the School of Life and Environmental Sciences. “It’s a stark example of how multiple stressors can act together to undermine reef resilience.”
The findings highlight the importance of long-term in-water monitoring made possible by the University’s One Tree Island Research Station, which provides vital infrastructure for studying coral ecosystems under natural conditions.
At the global level, the research sends an urgent warning.
“The current trajectory of climate change is progressing too quickly for corals to adjust,” the authors write. “Coral reefs are in danger, with recurrent anomalous heatwaves and mass coral bleaching being the greatest threat to their survival.”
Professor Byrne said the loss of these large, structure-forming corals will have lasting effects on reef biodiversity, coastal protection and food security.
“Coral reefs support more than a billion people worldwide. What we’re witnessing is a collapse in the natural resilience of these ecosystems. Ambitious global action to reduce emissions is now the only path to their survival.”
Download photos and videos of affected corals and the research at this link.
Interviews
Professor Maria Byrne | maria.byrne@sydney.edu.au | +61 452 176 609
Dr Shawna Foo | shawna.foo@sydney.edu.au
Media enquiries
Marcus Strom | marcus.strom@sydney.edu.au | +61 474 269 459
Outside of work hours, please call +61 2 8627 0246 (directs to a mobile number) or email media.office@sydney.edu.au.
Research
Byrne, M. et al ‘Marine heatwave-driven mortality of bleached colonies of the massive coral Goniopora is exacerbated by a black band disease epizootic’. (Proceedings of the Royal Society B: Biological Sciences 2025). DOI: 10.1098/rspb.2025.1912
Declaration
The authors declare no competing interests. Funding was received from the Australian Research Council
Journal
Proceedings of the Royal Society B Biological Sciences
Method of Research
Observational study
Subject of Research
Animals
Article Title
Marine heatwave-driven mortality of bleached colonies of the massive coral Goniopora is exacerbated by a black band disease epizootic
Article Publication Date
10-Dec-2025
Affected Goniopora cluster in February on One Tree Island at the Great Barrier Reef. With swimmer for scale
Goniopora coral cluster infected with black band disease at One Tree Island on the Great Barrier Reef.
Coral infected with black band disease at One Tree Island on the Great Barrier Reef.
Credit
The University of Sydney
Connection and protection boost health in coral reefs
University of Oxford
image:
Coral reef in Fiji, 2019. Credit: Emily Darling
view moreCredit: Credit: Emily Darling
Coral reefs may seem like paradise, but they are being degraded by a range of global and local factors, including climate change, poor water quality, and overfishing. New research reveals that connections between reefs help stabilise reef health, reducing the risk of collapse, and that a dual approach – improving conditions on both land and sea – may be the best way to protect these crucial ecosystems. The study was a collaboration between the University of Oxford, the University of Toronto, the National Research Council of Italy, and the Wildlife Conservation Society (WCS).
By developing a mathematical model of a network of coral reefs in Fiji, researchers simulated future reef conditions when managed in three different ways: reducing fishing pressure (increasing herbivore grazing), reducing environmental run-off (decreasing coral mortality), and the two interventions combined. Addressing these two local pressures is a focus as many reefs in Fiji are climate refugia with reduced impacts from global warming and coral bleaching, and show natural recovery to acute events like cyclones.
When considering local pressures, reducing the combination of fishing and pollution provided the best outcomes for reefs, showing the value of coordinated actions on land and in the ocean. Importantly, this result was robust to uncertainty in important reef conditions, indicating that it may be relevant for real-world decision-making in reef systems in Fiji and beyond.
They also discovered that fishery closures that improve grazing in less than half of the reef network can lead to increases in coral cover across the entire system due to larval dispersal connections. This result highlights the usefulness of planning conservation around networks of locations connected by coral larval dispersal, rather than isolated reefs – an approach that remains uncommon but proves powerful in revealing how connections between reefs influence long-term outcomes.
Lead researcher Dr Ariel Greiner (Department of Biology, University of Oxford) explained: “For too long, coral reefs have been managed in isolation. Our research shows that when we account for connections between reefs, we find that they are far more stable than previously thought. Protecting a few key reefs can help sustain high coral cover across the entire network – the key is identifying which ones to protect. We also illustrate that strategies that address both overfishing and land-based pollution together deliver the strongest and most lasting results.”
The study also revealed that the dispersal of juvenile corals likely stabilises long-term reef dynamics, lowering the risk of a coral-dominated reef tipping into a non-coral-dominated state – an indicator of poor reef health. Dr Ariel Greiner said: “Our study shows that when we include realistic dispersal connectivity between many reefs, the duality of coral- or non-coral-dominated reefs that we see in models of single or pairs of reefs disappears when we consider entire networks of reefs. This is a novel, unexpected, and exciting result with impacts for coral reef management, and for our understanding of coral reef dynamics globally.”
The study used a value of information (VOI) analysis in combination with a mathematical model, which is novel for marine conservation. This combination of methods can inform more effective conservation planning by allowing modellers and decision-makers to assess the robustness and impact of management actions across large spatial scales and long timeframes, improving our ability to anticipate risks and design resilient strategies for the future.
“This study shows how modelling can help forecast the long-term consequences of today’s conservation decisions and pinpoint the actions that build lasting resilience for reefs facing multiple pressures,” said Dr Emily Darling (Director of Coral Reefs at WCS), a co-author of the study. “What’s powerful about these findings is their practicality: when we focus on climate-resilient coral reefs, coordinated efforts to reduce fishing pressure and improve water quality can generate outsized benefits across entire reef networks. This gives decision-makers a realistic path to protect ecosystems while supporting the communities who depend on them.”
The researchers next plan to look similarly at other coral reef systems around the world and extend the models to more explicitly include human dynamics – for example, exploring the impact of tourism-funded conservation initiatives – and to better understand under what conditions the dispersal of young coral and macroalgae will stabilise local reef dynamics.
Notes to editors:
For media enquiries and interview requests, contact Dr Ariel Greiner: ariel.greiner@biology.ox.ac.uk
The study ‘Dispersal can spread management benefits: Insights from a modeled Fijian coral reef network’ has been published in Ecological Applications: https://esajournals.onlinelibrary.wiley.com/doi/10.1002/eap.70156
About the University of Oxford
Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the tenth year running, and number 3 in the QS World Rankings 2024. At the heart of this success are the twin-pillars of our ground-breaking research and innovation and our distinctive educational offer.
Oxford is world-famous for research and teaching excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research alongside our personalised approach to teaching sparks imaginative and inventive insights and solutions.
Through its research commercialisation arm, Oxford University Innovation, Oxford is the highest university patent filer in the UK and is ranked first in the UK for university spinouts, having created more than 300 new companies since 1988. Over a third of these companies have been created in the past five years. The university is a catalyst for prosperity in Oxfordshire and the United Kingdom, contributing around £16.9 billion to the UK economy in 2021/22, and supports more than 90,400 full time jobs.
Journal
Ecological Applications
Article Title
Dispersal can spread management benefits: Insights from a modeled Fijian coral reef network
Coral reef in Fiji, 2019. Credit: Emily Darling
Beach in the Vatu-i-ra seascape in Fiji, 2019. Credit: Stacy Jupiter
Oyster larvae on drugs move slowly and are stressed
Study finds that exposure to addictive drugs like fentanyl and ketamine affect the behavior and survival rates of oyster larvae
Washington, D.C., December 9, 2025 – The discharge and prevalence of psychoactive drugs in surface waters has raised concerns about potential risks to ecosystems and public health. Yet there is limited information on the ecotoxicity of these compounds in marine environments and aquaculture.
A study presented on Dec. 9 at the annual meeting of the Society for Risk Analysis in Washington, D.C., sheds light on the potential impacts of residual drug discharges on marine organisms. The findings suggest that traces of fentanyl, ketamine and benzoylecgonine (a byproduct of cocaine) can affect the swimming behavior and survival rates of oyster larvae living in contaminated saltwater environments.
“High drug consumption, continuous discharge and persistence contribute to the presence of drugs of abuse in surface waters, exposing aquatic organisms to chronic, low-level doses,” says Gustavo Salcedo, lead author of the study and a PhD candidate in the Francis College of Engineering at the University of Massachusetts Lowell.
Researchers from the University of Massachusetts Lowell investigated the physiological and molecular effects of three commonly detected psychoactive drugs - fentanyl (a synthetic opioid), ketamine (an anesthetic drug) and benzoylecgonine - on the larvae of C. virginica oysters (known as commonly farmed Eastern oysters). For the physiological assessment, three-day-old larvae were exposed to environmentally relevant concentrations of the drugs in saltwater over two weeks. Their survival and swimming behavior were monitored. For the molecular analysis, larvae were exposed to drugs for 12 hours, with changes in the expression of four stress biomarker genes (mapk14, hsp70, sod1, and gst) measured at different time points.
Key Findings:
After two weeks of exposure, survival declined in all treatments and doses.
Benzoylecgonine caused the greatest reduction in survival rate (62-76% lower than normal)
Larvae exposed to ketamine showed significantly decreased swimming speeds - most becoming completely motionless.
Notable shifts in swimming behaviors were observed. Motion changed from predominantly rectilinear (normal movement) to circular (fentanyl) or motionless (benzoylecgonine and ketamine).
Larvae exposed to benzoylecgonine showed a seven-fold increase in sod1 expression after four hours -- indicating a stress response in the oyster larvae.
“Our findings highlight the need for ecological risk assessments of these emerging contaminants in marine ecosystems – an area much less studied than freshwater environments,” adds Sheree Pagsuyoin, principal investigator of the study and associate professor in civil engineering at UMass Lowell.
More information on the study: https://www.sciencedirect.com/science/article/pii/S0147651325009340
###
EDITORS NOTE:
This research will be presented on December 9 at 8:30 EST at the Society for Risk Analysis (SRA) Annual Conference at the Downtown Westin Hotel in Washington, D.C. SRA Annual Conference welcomes press attendance. Please contact Emma Scott at emma@bigvoicecomm.com to register.
About Society for Risk Analysis
The Society for Risk Analysis (SRA) is a multidisciplinary, global organization dedicated to advancing the science and practice of risk analysis. Founded in 1980, SRA brings together researchers, practitioners, and policymakers from diverse fields including engineering, public health, environmental science, economics, and decision theory. The Society fosters collaboration and communication on risk assessment, management, and communication to inform decision-making and protect public well-being. SRA supports a wide range of scholarly activities, publications, and conferences. Learn more at www.sra.org.
No comments:
Post a Comment