Biology

Researchers say corals could survive climate change if carbon emissions are reduced

Hawaii’s coral reefs are teeming with life. Photo by Andre Seal

In a study published in Proceedings of the Royal Society B, researchers from the Toonen Bowen (ToBo) lab at the University of Hawaii’s Hawaii Institute of Marine Biology (HIMB) identified scenarios in which eight of the most common coral species found in Hawaii could adapt and survive ocean warming and acidification.

The corals studied are widespread throughout the Indo-Pacific region, which accounts for more than two-thirds of the planet’s coral reefs, and were found to be able to survive in a “low climate change scenario” in which laboratory conditions mirror a global reduction in carbon dioxide emissions.

Importantly, none of the species studied could survive a “business as usual” scenario of carbon dioxide emissions, a finding that suggests that reducing carbon dioxide emissions is essential for coral reef survival.

“This study shows that widespread and diverse coral species all show the potential to adapt to a changing climate, but that mitigation of climate change is essential to have any chance of adaptation,” explains Christopher Jury, a postdoctoral researcher at HIMB and lead author of the study.

“None of the coral species are likely to keep up with rapid climate change, but all eight species are likely to keep up with the slower rates of change targeted by the Paris Climate Agreement.”

Massive coral reef structures form over time through a process called coral calcification, in which individual coral organisms, or polyps, secrete a salt called calcium carbonate to build their own skeletons, which become limestone. Growth is slow—some coral colonies grow less than an inch per year—and researchers use coral growth rates as an indicator of the health of reef ecosystems.

For nearly a year, researchers from the ToBo lab used biodiverse, semi-enclosed outdoor “mesocosms” to simulate real-world conditions, controlling temperature and acidity levels and measuring the calcification responses of eight species of coral.

Corals can withstand climate change if carbon emissions are reduced

Pocillopora medulina. Credit: Keoki Stender

“When we analysed how corals would behave in warmer, more acidic environments, we found that about a quarter to half of their resistance is inherited through their genes,” explains Rob Toonen, professor at HIMB and lead researcher on the project. “This means that the ability to survive in future marine environments will be passed on to future generations, allowing corals to adapt to warmer and more acidic oceans.”

Global climate change is rapidly altering the environments to which coral reefs have adapted for millennia, and so far most predictions about the future of coral reefs have been pessimistic. These results are highly unexpected and welcome.

“This is quite surprising given that coral reefs are expected to collapse in Hawaii and globally under stress from climate change,” Julie emphasizes. “Most predictions say that corals will disappear almost completely and that reefs will collapse within a few decades because they cannot adapt fast enough to create meaningful change. This study shows that this is not true and shows that there is still an opportunity to protect coral reefs.”

Corals can withstand climate change if carbon emissions are reduced

Hamabozu goby. Photo by Keoki Stander.

Corals can withstand climate change if carbon emissions are reduced

Montipora Capitata. Credit: Keoki Stender

More than 500 million people depend on coral reefs for food, income and protection, and they are among the most biologically diverse ecosystems on Earth. They protect coastlines from storms and erosion, provide jobs for local communities and are a source of food, medicine and recreation.

The ability of corals to adapt to combined warming and acidification will play a key role in their response to global change over the coming decades. Most studies investigating corals’ adaptive capabilities have focused on heat tolerance. Little is known about corals’ ability to adapt to more acidic conditions, and few studies have investigated their ability to adapt to combined warming and acidification.

Growing evidence indicates that many coral species have a greater ability to adapt to a changing climate than commonly thought.

“We included eight of Hawaii’s most common coral species in our study, which account for approximately 95 percent of the corals on Hawaii’s reefs,” Julie said. “Understanding how these species respond to climate change will help us better understand how Hawaii’s reefs will change over time and how we can better allocate resources and plan for the future.”

Further information: Christopher P. Jury et al., “A broad range of coral adaptations to combined ocean warming and acidification.” Proceedings of the Royal Society B: Biological Sciences (2024). DOI: 10.1098/rspb.2024.1161

Courtesy of University of Hawaii at Manoa

Citation: Researchers say curtailed carbon emissions will help corals survive climate change (September 25, 2024) Retrieved September 25, 2024 from https://phys.org/news/2024-09-curtailed-carbon-emissions-corals-survive.html

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