Deep coral reefs in a "twilight zone" in the oceans differ sharply from those near the surface, dimming hopes they can be a refuge for marine life fleeing such threats as climate change and pollution, scientists said on Thursday.
Worldwide, coral reefs in shallow waters are among the ecosystems most threatened by climate change. The Great Barrier Reef off Australia suffered severe bleaching, a whitening driven by warm waters that can kill coral, in 2016 and 2017.
A U.S.-led team of divers who studied little-known reefs in the West Atlantic and Pacific Oceans between 30 and 150 meters (100 and 500 ft.) deep where sunlight fades, found most species of coral and fish were unlike those closer to the surface.