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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 suffered a severe discoloration, a bleaching caused by warm waters that can kill corals, in 2016 and 2017.
A team of American divers having studied little-known reefs in the western Atlantic and Pacific oceans between 30 and 150 meters deep where sunlight fades, most species of corals and fish did not look like those on the surface.
"We were surprised to find little overlap," said senior author Luiz Rocha of the California Academy of Sciences at Reuters of findings published in the science journal.
Less than five percent of fish and corals According to historical records, it was found in shallow and deep waters against the previous estimate of 60 to 75% of scientists, according to him.
"The potential for deep reefs to act as a refuge is much less than previously hoped," they wrote. And like shallow reefs, deep reefs have also been threatened by climate change, storms and pollution.
Divers found plastic fishing nets entangled in the deep waters of the Bahamas.
Rocha said scientists were trying to place temperature sensors in the twilight zone to see how deep the reefs were exposed to rising ocean temperatures, which are the most extreme at the surface. around the world like shallow reefs, he felt. 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. A 2016 study by the United Nations Environment Program showed that some deep reefs could be "lifeboats" for nearby, but connected, shallow reefs.
to be as vulnerable as shallow reefs to human pressures
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