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Some corals show genetic resistance to global warming

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Identifying coral species that can survive hot water temps may help conservation efforts. Photo courtesy NOAA.

‘Climate change is coming’

By Summit Voice

FRISCO — Here in the Colorado high country, the pine beetle epidemic that wiped out huge swaths of forest is one of the most visible signs of climate change. But in the midst of the destruction, you can find a few isolated lodgepole pines that survived the beetle invasion, standing as lone green giants in a sea of gray and brown tree skeletons.

There’s some speculation that there is enough genetic variation within the species that certain individual trees are able to repel the insects — and the same may be true of corals, another type of ecoystem that’s feeling the pain of global warming.

After a detailed genetic study of shallow-reef corals near Ofu Island in American Samoa, researchers from Stanford say that some corals are genetically “front-loaded” to withstand heat stress, with heat-stress genes already turned on and ready to work even before the eat stress began.

“It’s like already having your driver’s license and boarding pass out when you get close to the TSA screener at the airport, rather than starting to fumble through your wallet once you get to the front of the line,” said study co-author Stephen Palumbi, a senior fellow at the Stanford Woods Institute for the Environment and director of Stanford’s Hopkins Marine Station. “If we can find populations most likely to resist climate change and map them, then we can protect them. It’s of paramount importance because climate change is coming.”

Coral reefs are crucial sources of fisheries, aquaculture and storm protection for about 1 billion people worldwide. These highly productive ecosystems are constructed by reef-building corals, but overfishing and pollution plus rising temperatures and acidity have destroyed half of the world’s reef-building corals during the past 20 years. The onslaught of climate change makes it imperative to understand how corals respond to extreme temperatures and other environmental stresses.

Researchers have long known that certain corals withstand stresses better than others, the molecular mechanisms behind this enhanced resilience remained unclear. For their study, Palumbi, lead author Daniel Barshis, a Stanford postdoctoral scholar, and other researchers looked at how shallow-reef corals to determine how they survive waters that often get hotter 90 degrees during summer-time low tides.

Using cutting-edge DNA sequencing technology, the scientists examined the corals’ gene expression when subjected to water temperatures up to 95 degrees.

“These technologies are usually applied to human genome screens and medical diagnoses, but we’re now able to apply them to the most pressing questions in coral biology, like which genes might help corals survive extreme heat,” said Barshis.

Heat-resistant and heat-sensitive corals had a similar reaction to experimental heat: hundreds of genes “changed expression” or turned on to reduce and repair damage. But the ones most able to withstand the warm temperatures were the ones with heat-stress genes switched on in advance.

The findings show that DNA sequencing can offer broad insights into the differences that may allow some organisms to persist longer amid future changes to global climate. “We’re going to put a lot of effort into protecting coral reefs, but what happens if we wake up in 30 years and all our efforts are in vain because those corals have succumbed to climate change,” Palumbi said.

As with strong corals, finding species most likely to endure climate change – “resilience mapping” – is the first step toward protecting them, Palumbi said. “The solutions that we’re looking for must, at least partially, be out there in the world.”

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