Some coral populations already have genetic variants necessary to tolerate warm ocean waters, according to a study out Thursday that called for the spread of such genes to help corals survive global warming.

"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 study author Mikhail Matz of the University of Texas in a statement.

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

Worldwide, coral reefs have been badly damaged by rising sea surface temperatures. Bleaching -- a process that can cause widespread coral death due to loss of the symbiotic algae that corals depend on for food -- has been linked to warming waters.

Some corals, however, have higher tolerance for elevated temperatures, though until now no one understood why some adapted differently than others.

In the new study, researchers crossed corals from naturally warmer areas of the Great Barrier Reef in Australia with corals from a cooler latitude nearly 300 miles (480 kilometers) to the south.

They 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.

Furthermore, the study showed that when corals from the north cross with corals from the south, they can pass their tolerance for heat on to their offspring.

"This discovery adds to our understanding of the potential for coral to cope with hotter oceans," added study author Line Bay of the Australian Institute of Marine Science.

The findings were published in the U.S. journal Science.

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