Scientists may have found a solution to save the world’s coral reefs, as a new study found that shading them for just a few hours a day reduces bleaching.
Coral reefs across the world are suffering due to extreme weather events brought about by climate change. These events lead to widespread coral bleaching—a process that causes corals to become white, completely losing their once-vibrant colors.
The process is brought about by stressors that take a toll on coral health. Drastic changes in water temperatures, light and nutrient availability can all cause corals to bleach. While bleaching alone does not cause death, it can increase the likelihood of coral dying.
These bleaching events are increasing across the globe, and once these corals die, they rarely come back. As a result, researchers are frantically searching for ways to prevent this from happening.
Some severe mass bleaching events have occurred in some of the most famous coral reefs in the world. One of the worst bleaching events was on Australia’s Great Barrier Reef between 2016 to 2017, which caused bleaching across 91 percent of the reef.
“Despite being one of the best managed coral reef ecosystems in the world, the Great Barrier Reef is under imminent threat from climate change and has suffered four mass bleaching events since 2016,” Peter Butcherine, a research fellow at Australia’s Southern Cross University and lead author of the study published in Frontiers in Marine Science, told Newsweek. “This summer, 2023-24, there is an elevated bleaching risk due to the El Nino conditions, resulting in higher water temperature. In the future, the consequences of climate change, including more intense and frequent marine heatwaves and tropical storms, pose a significant risk to the Great Barrier Reef.
“Strong action to reduce climate change is required across the globe; however, addressing climate change alone is no longer likely to be enough to protect the Reef. The interventions from the Reef Restoration and Adaptation Program (RRAP) are likely to be needed in addition to reducing global greenhouse gas emissions and continued best-practice reef management.”
The Great Barrier Reef is an extremely important part of Australia’s surrounding ecosystem. Like other reefs, it provides a home to thousands of marine species.
Now, researchers involved in the Cooling and Shading subprogram of the Reef Restoration and Adaptation Program (RRAP), have found that shading can drastically improve the situation.
“We show that intermittent shading under controlled conditions can moderate light stress and slow bleaching,” Butcherine said in a release detailing the findings. “Reducing sunlight by 30 percent for four hours around solar noon can slow the onset of the bleaching response in some thermally-stressed shallow corals.”
To reach these findings, researchers used two species of stony corals, Turbinaria reniformis, commonly known as yellow scroll coral, and Duncanopsammia axifuga, or whisker coral. Fragments of the corals were covered with 30 percent of shading for four hours from noon—which recreated conditions on a cloudy day—or for 24 hours.
Shaded corals bleached a lot less than ones that were unshaded, the study found. Those that were shaded for 24 hours also bleached less than those shaded for four hours in the middle of the day.
“The complex nature of coral interactions with their environment means there are likely to be a range of responses to shading. We showed that coral species can respond differently when shaded, but these differences were not necessarily detrimental, just different from each other,” Butcherine said.
Shading also delayed the bleaching in the corals by “up to three degrees heating weeks (DHW).” According to the study, corals begin DHW once the water temperature starts to surpass the “maximum monthly mean water temperature by more than 1°C.”
When it passes this threshold, the bleaching process begins.
“This work directly informs the development of cooling and shading interventions to help protect the Great Barrier Reef during future bleaching events,” said Daniel Harrison, Ph.D., a researcher at Southern Cross University and program lead of RRAP Cooling and Shading. “Coral reefs are a critically important ecosystem so it is vital to investigate all the possible ways we can help them survive climate change.”
Artificial coverings, and seawater fogging systems, could all work to shade important reefs in the future, protecting them from conditions that cause them to bleach.
“The primary limitation of the fogging intervention is the atmospheric conditions, where low wind speed and high humidity are required, both of which occur during summer over the Great Barrier Reef,” Butcherine told Newsweek. “The fog generators under development require no in-water infrastructure, allowing them to be deployed relatively quickly and move freely between reefs. However, more research and development is required before the current technologies can be ready for scaled-up deployment in the field. So far, our field trials have delivered some promising results and suggest we could create sufficient fog cover over tens of hectares of reef.”