Some coral reefs can withstand climate change thanks to algae: NPR

Australia’s Great Barrier Reef is being hit hard by climate change, but new research shows how some corals are more resilient to heat.

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Australia’s Great Barrier Reef is being hit hard by climate change, but new research shows how some corals are more resilient to heat.

Sam McNeill/AP

As the climate warms, time is running out for coral reefs. So scientists around the world are looking for corals that can withstand heat better.

Now, new research shows how those “super corals” can survive: less roommate drama.

Reefs depend on an important partnership between corals and the algae that inhabit the coral tissue. Algae use sunlight to make food for corals and in return get a nice place to live.

But when the oceans warm, that relationship deteriorates and the corals kick out the algae. Without their roomies, corals can die, turning a ghostly white, bleached color.

Still, some corals seem to resist bleaching better than others. A new study shows that those corals depend on algae that are better able to withstand the heat.

The researchers hope that identifying these capabilities will help develop new conservation tools to protect the world’s reefs as temperatures rise. About one-quarter of all marine life depends in some way on coral reefs, while half a billion people around the world depend on reefs for their food and livelihoods.

“Heat stress can kill a lot of corals really quickly,” says Kate Quigley, a research scientist at James Cook University and the Minderoo Foundation in Australia. “I hope that nature has some mechanism so that we can do our work together.”

Heat waves are becoming more common in the ocean

Stretching more than 1,000 miles, Australia’s Great Barrier Reef was once thought too big to fail. But over the past seven years the reef has been repeatedly hit by underwater heat waves, resulting in Four mass bleaching events.

When the water temperature rises, the tiny algae inside the coral begin to produce toxins. Corals, also under stress from heat, begin to expel algae. In the process of evicting their tenants, corals lose a major food source.

This is not an immediate death sentence for coral reefs, however. When temperatures drop, corals can recover. But as ocean heat waves become more common, that recovery becomes harder and harder to achieve.

Healthy corals on the Great Barrier Reef’s magnetic islands were able to survive the bleaching events.

Mina Hatayama


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Mina Hatayama


Healthy corals on the Great Barrier Reef’s magnetic islands were able to survive the bleaching events.

Mina Hatayama

Still, even on the Great Barrier Reef, small pockets of coral have been able to withstand the heat waves that have hit in recent years.

“These reefs were really cooking but for some reason, they were resilient,” Quigley said.

Some corals have roommates who can take the heat

Quigley and his colleagues, along with others, looked at samples of these reefs and identified some of their key strategies In a new study In the journal Science Advances.

For one, surviving corals contain strains of algae that can withstand more heat. They were able to quickly build up their algal communities after heat waves, essentially recruiting the fastest new tenants.

“It really helps identify the reefs that we really need to make sure we’re protecting,” says Quigley. “These resilient reefs, the reefs that are naturally good at surviving, we need to make sure we’re relieving them of other stresses.”

Quigley also found that heat-resistant algae were abundant on reefs after ocean heat waves, but unlike corals that survived well, other corals couldn’t take advantage.

“It would be amazing if corals could just change,” said Patrick Buerger, a research fellow in coral reef resilience at Macquarie University in Sydney, Australia, who was not involved in the study. “Unfortunately, switching is not as common as we had hoped.”

Super corals can only live for so long

In addition to protecting the reefs that are home to these “super corals,” some researchers hope that those corals can also be used to restore reefs damaged by climate change and other impacts. But there may not be many to choose from.

“Even if we can engineer some super-duper corals, there may be species that will live on a future Earth,” said Lupita Ruiz-Jones, an assistant professor at Chaminade University in Honolulu who was not part of the research. . “And I think that’s the really sad part for me — just imagining this world where there’s so much less beauty in our water.”

With recent discoveries, researchers are now also focusing on algae as a key part of helping reefs survive. In Australia, a team of researchers is exposing algae to high temperatures, in an effort to develop Strains that are super-tolerant of heat.

While it’s hoped that these algae could help save reefs in the future, researcher Patrick Buerger says it likely won’t help all coral species. And even the hardiest corals can only withstand so much. Currently, Earth is on track to warm to just under 3 degrees Celsius by 2100, a level that Will wipe out almost all coral reefs.

“Action has to be on climate change,” he says. “It’s a short-term solution that might buy corals some time to adapt. But the main focus has to be on climate. There’s no silver bullet to the problem.”

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