New research indicates that the proliferation of lethal coral diseases is closely associated with rising ocean temperatures, with dire implications for the future. If current warming trends persist, coral disease is projected to become endemic in reefs worldwide within the next century, threatening entire ecosystems and adversely affecting coastal communities.
In a comprehensive meta-analysis, scientists from UNSW Sydney examined 108 studies on coral health, specifically focusing on disease symptoms observed in coral reefs. By correlating these findings with sea surface temperature records, the researchers assessed the impact of climate change, particularly ocean warming, on the prevalence of coral diseases globally. Their analysis revealed a threefold increase in coral disease over the past 25 years, reaching a global average of 9.92 percent. Disturbingly, their modeling also predicts that by 2100, disease prevalence could skyrocket to 76.8 percent if temperatures continue to rise along the current trajectory—representing the most conservative worst-case scenario.
Samantha Burke, the lead author of the study and a Ph.D. candidate at the School of Biological, Earth & Environmental Sciences, emphasizes that these findings underscore the devastating consequences of rising temperatures on coral reefs and the urgent need for swift action to mitigate climate change.
Notably, the research indicates that even under more conservative estimates of rising ocean temperatures, the widespread occurrence of coral disease is expected. Ms. Burke highlights the seriousness of coral disease as a significant cause of coral mortality and reef degradation. She emphasizes that even if ocean temperatures remain within conservative bounds, the modeling suggests a worsening situation for coral reefs globally.
Based on the available data, the study suggests that the Pacific Ocean is more susceptible to intensified coral disease compared to the Atlantic Ocean and Indian Ocean. However, Ms. Burke cautions that distinguishing the sole influence of warming ocean temperatures from other stressors affecting corals remains challenging. Nevertheless, she emphasizes the escalating prevalence of coral disease worldwide and warns that without urgent action to address rising temperatures, more corals will succumb to disease.
The critical role of coral reefs in the marine ecosystem cannot be understated. They support approximately a quarter of the world’s fish population and are vital for coastal communities that rely on reefs for fisheries and tourism. Additionally, reefs provide crucial protection against storms and coastal erosion.
Coral disease occurs when the coral’s immune system is compromised, usually due to pathogen infections, such as bacteria or fungi. These infections inflict diseases upon the corals, which differ from coral bleaching—an event where stressed corals expel the symbiotic zooxanthellae algae responsible for their vibrant coloration.
Ms. Burke explains that while certain diseases progress rapidly, most corals that contract diseases ultimately perish. Given the slow growth rate of reefs, the recovery of affected corals becomes uncertain, leading to the potential loss of entire reef sections.
Corals are sensitive organisms that rely on specific environmental conditions, including water temperature, salinity, and quality, for survival. When corals exist outside their optimal range, they experience stress, which hampers their growth, reproduction, and overall resilience.
While infectious pathogens like bacteria and fungi contribute to coral disease, stressed corals are more susceptible to infection. Rising water temperatures can exacerbate the virulence and growth rate of disease-causing organisms.
As ocean temperatures continue to rise, coral stress intensifies, leading to a compromised immune response. Increasing temperatures also create favorable conditions for disease-causing pathogens.
Many coral diseases are identified based on their visual appearance, such as black band disease or yellow band disease. However, the exact pathogens responsible for these diseases are often unknown.
Ms. Burke emphasizes the importance of further research into coral disease to facilitate effective disease interventions and highlight the multifaceted threats faced by coral reef ecosystems. She stresses that resolving coral disease is a complex task that requires comprehensive action on both large and small scales. Simply waiting for a universal antibiotic-like solution would be inadequate. Consequently, urgent measures to mitigate rising temperatures should be prioritized as a starting point in developing effective strategies to combat coral disease.
Reference: “The impact of rising temperatures on the prevalence of coral diseases and its predictability: A global meta-analysis” by Samantha Burke, Patrice Pottier, Malgorzata Lagisz, Erin L. Macartney, Tracy Ainsworth, Szymon M. Drobniak, and Shinichi Nakagawa, 6 June 2023, Ecology Letters.
DOI: 10.1111/ele.14266
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Frequently Asked Questions (FAQs) about coral disease prevalence
What is the impact of climate change on coral disease prevalence?
Rising ocean temperatures due to climate change are leading to an increased spread of deadly coral diseases. According to research, coral disease is projected to become endemic to reefs worldwide by the next century. The prevalence of coral disease has tripled over the past 25 years, reaching 9.92 percent globally. If temperatures continue to rise, disease prevalence could reach as high as 76.8 percent by 2100.
Why is coral disease a concern?
Coral disease has devastating effects on coral reefs and the ecosystems they support. Diseased corals are more likely to die, resulting in the potential loss of entire reef sections. Coral reefs play a critical role in marine biodiversity, providing habitat for a quarter of the world’s fish population. They are also essential for coastal communities that rely on reefs for fisheries, tourism, and protection against storms and erosion.
What causes coral disease?
Coral disease occurs when the coral’s immune system is compromised, usually due to infections by pathogens such as bacteria or fungi. Stressed corals, often caused by factors like rising water temperatures, are more susceptible to these infections. While the exact pathogens responsible for coral diseases are not always known, research is ongoing to better understand the complex interactions between corals, pathogens, and environmental factors.
What can be done to mitigate coral disease?
Mitigating coral disease requires addressing the underlying cause—climate change and rising ocean temperatures. Urgent action is needed to reduce greenhouse gas emissions and implement measures to limit global warming. Protecting coral reef ecosystems through conservation efforts, promoting sustainable fishing practices, and minimizing pollution and other stressors can also help enhance coral resilience and reduce disease prevalence.
What are the potential consequences if coral disease prevalence continues to rise?
If coral disease prevalence continues to increase, entire reef ecosystems could be eradicated, leading to significant ecological and economic consequences. The loss of coral reefs would not only impact marine biodiversity but also affect coastal populations that rely on reefs for their livelihoods and protection. Swift action is crucial to prevent further deterioration of coral health and to safeguard the invaluable services provided by coral reefs.
More about coral disease prevalence
- Ecology Letters: The impact of rising temperatures on the prevalence of coral diseases and its predictability: A global meta-analysis
- UNSW Sydney: Research on Coral Disease and Climate Change
- NOAA Coral Reef Conservation Program: Climate Change and Coral Disease
- National Geographic: Coral Reefs
- IUCN Red List of Threatened Species: Coral Reefs
