WASHINGTON: At a time when global warming is threatening the very survival of coral reefs, some coral populations already have genetic variants necessary to tolerate warm ocean waters, a new study says.

Humans can also help to spread these genes by mixing and matching corals from different latitudes may boost reef survival.

Worldwide, coral reefs have been badly damaged by rising sea surface temperatures.

“Our research found that corals do not have to wait for new mutations to appear. Averting coral extinction may start with something as simple as an exchange of coral immigrants to spread already existing genetic variants,” said Mikhail Matz, associate professor of integrative biology at The University of Texas at Austin.

“Coral larvae can move across oceans naturally, but humans could also contribute, relocating adult corals to jump-start the process,” Matz added.

The researchers crossed corals from naturally warmer areas of the Great Barrier Reef in Australia with corals from a cooler latitude nearly 300 miles to the south.

The scientists found that coral larvae with parents from the north, where waters were about two degrees Celsius warmer, were up to 10 times as likely to survive heat stress, compared with those with parents from the south.

Using genomic tools, the researchers identified the biological processes responsible for heat tolerance and demonstrated that heat tolerance could evolve rapidly based on existing genetic variation.

“This discovery adds to our understanding of the potential for coral to cope with hotter oceans,” said Line Bay, an evolutionary ecologist with the Australian Institute of Marine Science in Townsville.

“This is the occasion for hope and optimism about coral reefs and the marine life that thrive there,” Matz said.

The findings were outlined in the journal Science.