VOA常速英语2019--珊瑚礁：气候变化的晴雨表（在线收听）

Here in the northern Red Sea in the Bay of Aqaba, Israeli scientists have discovered something extraordinary. Despite higher water temperatures, these corals are healthy and even thriving. We found that corals are not bleaching. We’ve never witnessed any bleaching event which is so common elsewhere. To find out why, small corals were subjected to bleaching conditions in the laboratory. Their ruddy color is a sign of good health. Bleaching conditions are usually considered as 1 to 2 degrees above the summer maximum and there was no bleaching. We elevated the the temperature furthermore and only at 5 and 6 degrees above some maximum, they showed signs of stress and bleaching.

这里是亚喀巴湾的红海北部，以色列科学家有了惊人的发现。虽然水温升高，但这些珊瑚依然健康，甚至繁茂。我们发现，这些珊瑚并没有被漂白。我们没发现它们出现任何的漂白现象，但这种现象在其他地方十分常见。为了寻找原因，小珊瑚在实验室里经历了漂白的环境。它们颜色红润，表明十分健康。一般认为，漂白的环境是比夏天最高的温度还要高上一两度，但它们依然未出现漂白的现象。我们进一步升温，升至比最高温度高五六度的程度，它们才开始有压力并出现漂白现象。

But how can the coral here withstand such high temperatures when mass coral bleaching is occurring elsewhere? The answer may be found 18,000 years ago when the Red Sea was much hotter. In order to survive conditions, very hot conditions in the southern Red Sea, they had to be or undergo selection towards thermally resilient corals. Those that suffer from the hot, the very hot conditions down there didn’t survive, and so corals that we see here nowadays are the ones that are descendants of the ones that survived. The study also indicates that future generations of coral in the Bay of Aqaba will also be immune to bleaching. Think that although see what the temperature is rising in the Gulf of Aqaba, maybe at a rate that exceeds the global average, still we have about a hundred years before these corals will experience bleaching conditions or cross the bleaching threshold. Coral reefs are often the first indicator of climate change. Their loss would raise the risk of extinction of thousands of fish species and other marine life.

但这里的珊瑚为何可以经受得住这样的高温呢？毕竟其他地方的珊瑚都出现了大范围漂白的情况。答案可能要追溯到1.8万年前，那时候，红海温度比现在高。为了经受住当时的环境——红海南部的极高温度，这里的珊瑚必须要经受住物竞天择的过程，进化为耐热的珊瑚。经受不住高温的珊瑚没有存活下来，所以我们今天看到的珊瑚是经过淘汰的珊瑚的后代。该研究还表明，未来亚喀巴湾的珊瑚不会再出现漂白现象。虽然我们注意到亚喀巴湾的温度在上升，或许升温的速度要高于全球的平均速度，但我们至少还要过大概100年的时间，这里的珊瑚才会漂白，或者说超过可以出现漂白现象的阈值。珊瑚礁通常是气候变化的晴雨表。一旦珊瑚礁消失，上千种鱼类等海洋生物都将面临灭绝的危险。