Deep coral reefs are not immune to the impacts of pollution, climate change

Deep coral reefs in a "twilight zone" in the oceans differ greatly from those near the surface, dampening the hope that they may serve as a refuge for marine life fleeing threats such as climate change and pollution. ] Coral reefs in shallow waters around the world are among the ecosystems most at risk from climate change. The Great Barrier Reef off Australia has undergone intense bleaching, bleaching due to the warm waters that can kill corals, in 2016 and 2017.

A team of American divers studied the little-known reefs Atlantic and Pacific oceans. 30 and 150 meters deep where the sunlight fades, most species of corals and fish do not look like those of the surface.

"We were surprised to find little overlap," said Luiz Rocha, of the California Academy of Sciences. The results published in the journal Science

Less than five percent of fish and corals were found in shallow and deep waters against the previous estimate of 60-75 percent scientists, based on the papers historical, he said. 19659002] "The potential of deep reefs to act as a refuge is much less than we expected," they wrote

and, like shallow reefs, deep reefs were also threatened by climate change, storms and pollution. Divers found, for example, plastic fishing nets entangled in deep corals of the Philippines and deep corals damaged by the warm waters of the Bahamas

Rocha said that scientists were trying to place temperature sensors in the Twilight zone. have been exposed to rising ocean temperatures, which are the most extreme at the surface.

Coral bleaching is observed near the island of Orpheus on the Great Barrier Reef in Australia. According to scientists, shallow reefs are completely different from those of deep reefs (Greg Torda / ARC Center for Excellence)

Deep reefs covered at least the same global oceanic area as shallow reefs. Some reefs, such as those at the mouth of the Amazon River, exist only in the depths.

The authors advocate better guarantees for deep reefs, for example by expanding protected areas and prohibiting bottom trawlers that can scratch the seabed. ] Among previous research, a 2016 study by the United Nations Environment Program found evidence that some deep reefs could act as "lifeboats" for nearby, shallower, connected reefs. But he said that in other cases, deep reefs "may be just as vulnerable as shallow reefs" to human pressures.