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A new study on how coral reacts to global climate change has some researchers optimistic that at least a few of the polychromatic reefs crucial to underwater ecosystems may be better able to adjust to a warming world than was previously thought.
That's good news, given that coral reefs soften the blow of storms headed to areas where people live, and nurture a kaleidoscopic array of fish that provide a livelihood and food for people around the globe.
But coral reefs aren’t out of hot water yet.
The new study’s findings stem from research on a single coral species in a remote Pacific Ocean lagoon that laps the shores of Ofu Island in American Samoa. The findings could well apply to corals around the world, explained Stephen Palumbi, a marine biologist at Stanford University's Hopkins Marine Station in Pacific Grove, Calif., and the study's lead author.
"If that is true, then perhaps corals around the world have a slightly longer period of time before global ocean warming completely does them in. … As the oceans warm, they will pick up some of the slack, but we don't know what the limits of that are. We don't know when they are going to get maxed out," he told NBC News.
"As the oceans warm, they will pick up some of the slack, but we don't know what the limits of that are. We don't know when they are going to get maxed out."
What the researchers do know is that the coral Acropora hyacinthus is able to adjust its physiology to the gradual, annual rise in ocean warmth due to the forces of global climate change. Some colonies have also evolved adaptations over generations that appear to afford even greater resilience to warming. The finding is reported Thursday in the journal Science.
"It sends a very clear message that all of the doom and gloom we are hearing about coral reefs — while we don't want to take these threats any less seriously — we might have more time than we think" to deal with the challenges posed by climate change, Elizabeth McLeod, an Austin, Texas-based coral reef expert who studies climate adaptation science for The Nature Conservancy, told NBC News.
McLeod, who was not involved with the study, added the caveat that "this is one particular species in one very special place. There are other places like it in the world, but it is not the common trend. So, for us, it is really about learning what are the conditions that make the place special and how do we use that information to prioritize areas for protection."
One lagoon, two pools
Palumbi and his colleagues conducted their research in a lagoon with two pools of water on the shoreward side of a barrier reef. One pool is shallower than the other and thus heats up more at low tide — to 95 degrees Fahrenheit, which had been considered too high for corals to survive. But, in fact, corals of the same species thrive in both pools. The researchers wanted to know why.
To find out, they swapped some pieces of coral from both pools and let them grow in their respective new environments for several years. They then exposed the corals to heat stress tests and performed genetic analyses.
"As we learn more information about corals that are potentially genetically resistant … we can be selecting ones that are more likely to survive a stressful climate."
Their findings suggest that corals are able to acclimate to warmer waters and that way deal with higher heat stress about 50 times faster than they would adapt through evolutionary change alone. But there is also an evolutionary aspect given that the corals from the warm pool that stayed in the warm pool performed the best.
"That there are differences from corals between two pools is not necessarily surprising," Cynthia Riginos, who studies ecological and evolutionary genetics at the University of Queensland in Brisbane, Australia, told NBC News via email. "Adaptive differences — that is, DNA-based differences — might underlie those fixed effects, but there are several other equally plausible explanations."
Informing conservation management
Regardless of what underlies the differences, the findings suggest that the corals already adapted to warm water ought to become a conservation priority "so that when the ocean is warm, there is a repository of warm water adapted coral that might be able to still live," Palumbi said.
Nor are these corals necessarily resilient to other known threats from global climate change such as ocean acidification, though it's possible such corals exist, Palumbi said.
What's more, the acclimation to warmer water is a gradual process that is unlikely to offer much protection from a bulge of warm water that suddenly appears over a reef and sits there for several months, triggering a mass bleaching event. This happened during the 1997-98 El Niño with dire consequences for corals around the world.
"This information also has implications for more controversial ideas like selective breeding of heat resistant corals," McLeod said of the new study. "As we learn more information about corals that are potentially genetically resistant … we can be selecting ones that are more likely to survive a stressful climate."