Coral reefs can adapt to climate change: study

Cool-water corals can adapt to a slightly warmer ocean, but only if global greenhouse gas emissions are reduced, according to a study.
Researchers at The University of California, Davis in the US found that some corals in the normally cool waters of the Cook Islands carry genetic variants that predispose them to heat tolerance.
This could help the population adapt more quickly to rising temperatures. However, the preliminary results show they may not adapt quickly enough to outpace climate change.
"These corals are not going to adapt at an unlimited rate," said Rachael Bay, a postdoctoral scholar at the University of California, Davis.

"Keeping these reefs around requires curbing emissions," said Bay, lead author of the study published in the journal Science Advances.
In previous work, the researchers identified genes that make some individual corals more heat tolerant than others.

In the current study, they found these warm water variants in corals in the Cook Islands, at low levels.
To test how well the corals could use these genes to adapt to future climate change, the scientists ran computer simulations based on projections by the UN Intergovernmental Panel for Climate Change.
In a business-as-usual scenario, emissions continue to rise rapidly throughout the 21st century, and temperatures rise between 2 and 3.7 degrees Celsius, researchers said.

The least severe scenario is where warming does not exceed 1.8 degrees Celsius by 2100. In between is the moderate scenario suggested by the Paris Accord, in which emissions peak and then rapidly decline by about 2040, they said.
In the simulations, corals could survive under the mild and moderate scenarios. However, under the more severe scenarios, adaptation was not fast enough to prevent extinction.
This research focused specifically on tabletop corals. Further study is needed to understand the broader implications for other coral species, researchers said.