Anthropogenic greenhouse gas emissions have caused an increase in the global surface temperature of approximately 1°C since pre-industrial times, making ocean water warmer and more acidic. This has led to unprecedented mass coral bleaching events which – combined with growing local pressures – have made coral reefs one of the most threatened ecosystems on Earth.

But there might be a glimmer of hope for the world’s reefs, as researchers in Hawaii’s Kāne’ohe Bay have found a set of “supercorals” that can tolerate warmer temperatures and more acidic waters. These corals even bounced back after sewage decimated the bay less than 30 years ago. The researchers collected branches of three dominant coral species from about two dozen colonies in Kāne’ohe Bay and Waimānalo Bay, just 11 miles to the southeast. Then, back in the laboratory, they exposed some of the corals to warm or acidic waters in aquariums for five weeks. They found corals from Kāne’ohe Bay tolerated warmer and more acidic waters better than the corals from Waimānalo Bay. The corals from Kāne’ohe Bay also grew more than twice as fast as the Waimānalo Bay corals.

While the findings provide some hope about the future of these remarkable ecosystems, scientists warn that if we don’t substantially reduce climate change, even the very tough corals from Kane’ohe Bay would die under the temperatures they might see in a few decades.