Heat waves are roasting reefs, but some corals may be resilient

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It’s no secret that warming ocean waters have devastated many of the world’s coral reefs. For instance, a 2016 marine heat wave killed 30 percent of coral in the Great Barrier Reef, a study published online April 18 in Nature reports. But some coral species may be able to adapt and survive in warmer waters for another century, or even two, a second team reports April 19 in PLOS Genetics. And that offers a glimmer of hope for future ocean biodiversity.

“What we’ve just experienced [in the Great Barrier Reef] is one hell of a natural selection experiment,” says coral reef expert Terry Hughes of James Cook University in Townsville, Australia. In total, about 50 percent of the reef’s corals have died since 2016, he says. A bright side, maybe: “The ones that are left are tougher.”

While the marine heat wave particularly damaged staghorn corals (Acropora millepora), this species may ultimately prove to be one of the resilient ones, Mikhail Matz, a biologist at the University of Texas at Austin, and his colleagues report in PLOS Genetics. A new analysis shows the branching, fast-growing coral — a key reef builder — is genetically diverse enough to survive for another 100 to 250 years, depending on how quickly the planet warms. Other studies have suggested coral reefs may not last this century.

What happens to coral reefs affects vast underwater ecosystems, and the hundreds of millions of people who depend on those ecosystems for fishing, tourism and more. So scientists want to understand how corals might fare as climate change brings longer and stronger marine heat waves (SN: 4/10/18, p. 5).

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