Coral reef nightlife becomes more predatory with artificial light
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Graphical abstract
view moreCredit: Emma Weschke
Artificial light can wake sleeping fish and attract predators, changing nighttime coral reef communities, according to new research using novel underwater infrared cameras.
The study, published today in Global Change Biology, was conducted by an international team of scientists from the UK, France, French Polynesia and Chile and the first large-scale experiment to investigate the impact of light pollution on the nightlife of coral reefs.
Lead author, Dr Emma Weschke, from the University of Bristol’s School of Biological Sciences, said: “When the sun sets, coral reefs undergo a dramatic transformation. The vibrant fish we see in the day retreat to sleep among the corals and elusive nocturnal species emerge from caves and cervices in pursuit of prey.”
Senior author, Professor Andy Radford, also from Bristol, added: “The night usually brings a veil of darkness that allows marine life to hide from nocturnal predators. But artificial light generated by human activities exposes coral reef inhabitants to unexpected danger.”
Using purpose built underwater infrared night-vision cameras, the scientists could film the reef at night without interfering with fish behaviour. This is because fish cannot see in infrared.
A larger number of fish species were present on artificially illuminated reefs at night compared to control sites with no artificial light. Further investigation revealed these species were predatory fish—feeding on the zooplankton, small fish and invertebrates.
Dr Weschke said: “Many of the species detected on artificially lit reefs were not nocturnal fish, but those that are only usually active during the day. Finding that light pollution can cause fish to stay awake later than usual is concerning because sleep—like for us—is likely essential for regenerating energy and maintaining fitness.”
Professor Radford explained: “Artificial light makes it much easier for predators to locate and capture prey, reducing their foraging effort. Which is why we think that greater numbers are being attracted to artificially illuminated coral reefs at night.”
The changes observed in the nightlife on the reef were observed after an average of 25 consecutive nights exposure to artificial light. Only a few nights of exposure were not long enough to elicit any noticeable changes in fish communities compared to controls.
“This is positive news as it suggests that there could be low-cost solutions that are quick to implement,” said co-author Professor Steve Simpson, also of Bristol’s School of Biological Sciences. “Reducing the impacts of artificial light could help build resilience on valuable coral reefs.”
Dr Weschke added: “Unlike greenhouse gasses and plastics, artificial light is a pollutant that doesn’t leave a residue when switched off.
“Limiting artificial light in both its intensity and duration, prioritising it for essential needs and reducing aesthetic use, will help reestablish naturally dark nights that marine ecosystems evolved with.”
The work was conducted by researchers from the University of Bristol, UK, Centre de Recherches Insulaires et Observatoire de l’Environnement (CRIOBE), French Polynesia and Pontificia Universidad Católica de Chile.
Emma Weschke deploying infrared cameras
Credit
Jules Schligler
Still from video of reef at night exposed to artificial light
Credit
Emma Weschke
Paper:
‘Artificial light increases nighttime prevalence of predatory fishes, altering community composition on coral reefs’ by Emma Weschke et al in Global Change Biology.
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DOI: 10.1111/gcb.70002
Journal
Global Change Biology
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Artificial light increases nighttime prevalence of predatory fishes, altering community composition on coral reefs
Article Publication Date
18-Dec-2024
New study highlights the correlation between live corals and fishing yields
Research led by Woods Hole Oceanographic Institution predicts lower fishing yields as corals struggle to survive
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Fish swim among Australia’s Great Barrier Reef. In the past 30 years, coral bleaching caused by ocean warming has contributed to a 19% loss of the world’s coral reef area.
view moreCredit: Credit: Konrad Hughen/©Woods Hole Oceanographic Institution
Woods Hole, Mass. (Dec. 19, 2024) - What does a decline in healthy coral reefs mean for fisheries? A new study published in Marine Resource Economics, led by the Woods Hole Oceanographic Institution (WHOI), examines the correlation between fish yield and live coral habitats. Researchers analyzed the yields of nine fisheries dependent on Australia’s Great Barrier Reef from 2016 to 2020. Results show that substantial losses could occur if the restoration of coral reefs is not prioritized.
In 2024, the Great Barrier Reef experienced one of the worst bleaching events in its history. According to the Australian Marine Institute, an aerial survey of the Great Barrier Marine Park showed bleaching across 73% of surveyed reefs. These vulnerable ecosystems rely on the microscopic algae called zooxanthellae for survival. These algae also contribute to coral’s vibrant colors. Elevated ocean temperatures stress corals, causing them to expel the algae, resulting in bleaching. If warming persists, the algae may not return, leaving the coral bleached and at risk of dying. In the past 30 years, coral bleaching caused by ocean warming has contributed to a 19% loss of the world’s coral reef area.
“This rapid loss of coral will force fish capable of living independently of them to move elsewhere. Less concentrated populations can lead to smaller yields for fisheries,” said Marine (Yaqin) Liu, an environmental economist at WHOI. “For fish that rely on reefs for food or shelter, such as butterflyfish and coral trout, yields will shrink as their populations do.”
The study identifies coral trout and saddletail snappers as the two most vulnerable fisheries, both relying on outer-shelf reefs as their primary habitats. The study shows that if the live coral cover of the Great Barrier Reef were to be reduced from 30% to 25%, the maximum sustainable yield of coral trout would drop by 8% and 19% for saddletail snappers. With a drop of live coral cover from 10% to 5%, the maximum sustainable yield of the coral trout fishery would drop by 27% and saddletail snapper would drop 56%.
"Coral trout and saddletail snapper are part of Queensland, Australia’s line fishery, an industry with $27-31 million gross value,” explained Qingran Li, an assistant professor of economics and financial studies at Clarkson University in New York. “While this methodology of this study does not lend itself to making dollar predictions, we can expect a decline in fishing yields to have substantial economic impacts, such as loss of jobs and reduced export."
As ocean temperatures continue to rise, coral casualty events such as bleaching are more likely to occur. Reefs host 25% of marine life and protect coastal communities from the impacts of major storms. They also support millions in tourism and fishing annually.
“It is important to support claims about climate change with hard data. Responsible fisheries are already safeguarding coral reefs by integrating sustainable approaches, but human impacts like ocean warming and acidification further threaten coral reefs and fisheries yields,” Liu continued. “WHOI’s Reef Solutions Team continues to study and develop innovative ways to restore and strengthen coral reefs, with a goal of taking successful learnings and implementing them globally.”
About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu.
About Clarkson University
Clarkson University is a proven leader in technological education, research, innovation, and sustainable economic development. With its main campus in Potsdam, N.Y., and additional graduate programs and research facilities in the Capital Region and Hudson Valley, Clarkson faculty have a direct impact on more than 7,800 students annually through nationally recognized undergraduate and graduate STEM-designated degrees in engineering, business, science, and health professions; executive education, industry-relevant credentials, and K-12 STEM programs. Alumni earn salaries among the top 2% in the nation: one in five already leads in the c-suite. To learn more go to www.clarkson.edu
Journal
Marine Resource Economics
Method of Research
Data/statistical analysis
Subject of Research
Animals
Article Title
Impacts of Reef Degradation on Commercial Fisheries
Article Publication Date
18-Dec-2024
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