Coral Refugees

As the planet and oceans continue to heat up, sites where coral (珊瑚) has recently boomed are becoming less and less habitable. For instance, thanks to extreme ocean temperatures, much of Australia's Great Barrier Reef suffered mass bleaching in 2016 and 2017 that turned parades of colorful coral into dull, white masses.

【小题1】 By studying fossils in Daya Bay, just northeast of Hong Kong in the South China Sea, a team of researchers found that during periods of warming in the distant past, coral reefs migrated away from equatorial warm waters to the bay's more hospitable subtropical latitudes.

"We showed that the higher-latitude reefs up around China did grow during earlier warm periods," says Tara Clark, a paleontologist at the University of Wollongong in Australia. 【小题2】 There the researchers randomly collected dead corals and calculated their ages using radio isotopic (同位素的) dating techniques. The ancient reefs grew between 6,850 and 5,510years ago, the scientists reported in January in Geology, which coincides with a time when ocean temperatures around South China and nearby seas were one to two degrees Celsius warmer on average than they are today. 【小题3】 Of course, the idea of refuges for endangered reefs on the move is not new, but using the fossil record to help locate such places is relatively novel approach.

Although the fossil evidence suggests that Daya Bay could one day provide a heaven for corals, there are some hurdles in the way of making the refuge an inviting place, Clark says. 【小题4】 And Daya Bay is now heavily polluted, which could threaten its ability to sustain reefs. But in light of the new discovery, Clark says, "we might as well do the best we can to protect these areas, just in case."