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Red Sea corals to persist, even as other corals succumb to global warming

Red Sea corals to persist, even as other corals succumb to global warming
Researchers studied corals in the Gulf of Aqaba, at the northern tip of the Red Sea, to gain understanding of their particular resistance to higher temperatures -- and learn how to better protect them. Photo by Romain Savary/EPFL

May 4 (UPI) -- New lab experiments have shed light on the ability of corals in the Red Sea's Gulf of Aqaba to survive rising ocean temperatures.

When marine heatwaves strike, the algae that provide corals with nutrients and their vibrant colors abandon their homes.

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The phenomenon, known as coral bleaching, has become more widespread throughout the reefs of Australia, the Maldives and the Caribbean.

However, corals living in the northern Red Sea -- where temperatures are already quite warm -- have proven mostly immune to coral bleaching.

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To better understand their resiliency, researchers collected coral samples from the Gulf of Aqaba and exposed them to a range of extreme conditions.

During each of the stress tests, scientists measured the physiological and genetic responses of the corals.

Researchers published the results of the experiments this week in the journal PNAS.

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"We already knew that corals in the Gulf of Aqaba, at the northern tip of the Red Sea, were particularly resistant to higher temperatures," lead study author Romain Savary said in a press release.

"But we wanted to study the full molecular mechanism behind this resistance," said Savary, a postdoctoral researcher at EPFL's Laboratory for Biological Geochemistry in Switzerland.

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Currently, the temperatures Aqaba corals experience during any given top out at 27 degrees Celsius, or roughly 80 degrees Fahrenheit.

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In the lab, scientists exposed the coral samples to water temperatures of 29.5, 32 and 34.5 degrees Celsius. Researchers turned up the water temperature for three hours at a time and, later, for an entire week.

During the experiments, scientists measured the gene expression of both the corals and their symbiotic algal companions.

The results of their experiments suggest the corals of the northern Red Sea are incredibly resilient and unlikely to lose their color even under the most dramatic ocean warming scenarios.

"The main thing we found is that these corals currently live in temperatures well below the maximum they can withstand with their molecular machinery, which means they're naturally shielded against the temperature increases that will probably occur over the next 100 or even 200 years," Savary said.

"Our measurements showed that at temperatures of up to 32 degrees Celsius, the corals and their symbiotic organisms were able to molecularly recover and acclimate to both short-term and long-term heat stress without any major consequences," Savary said.

The test results showed corals and their algal inhabitants enact a complex combination of genetic changes in response to rises in water temperature.

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"Romain's research gives us insight into the specific genetic factors that allow corals to survive," said study co-author Anders Meibom, head of the LGB.

"His study also indicates that an entire symphony of genetic expression is at work to give corals this extraordinary power," Meibom said.

While the new research could help scientists identify "super corals" that are especially resistant to marine heatwaves and coral bleaching, potentially aiding conservation efforts, researchers said the best way to protect coral reefs is to reduce greenhouse gas emissions and slow climate change.

If the planet continues to warm, saving the Great Barrier Reef using coral from the northern Red Sea won't be an option.

"Corals are highly dependent on their surroundings," said Meibom. "They can adapt to new environments only after a long, natural colonization process. What's more, the Great Barrier Reef is the size of Italy -- it would be impossible to repopulate it artificially."

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