 Thirteen thousand years ago, as the last ice age ended, entire stretches of Australia’s Great Barrier Reef perished. 三万年前，随着最后一个冰河时期的结束，澳大利亚的大堡礁整个消失了。 Rising sea levels blanketed the world’s largest collection of corals with sediment coming off the newly inundated land, blocking the sunlight corals need to grow. 上升的海平面用来自最新淹没的大陆的沉积物将珊瑚覆盖了起来，阻断了它们生长所需的阳光。 The reef eventually recovered, but it took hundreds to thousands of years. 珊瑚礁最后还是恢复了过来，不过花去了成千上万年。 This near death and eventual resurrection wasn’t a one-off, according to a new study that reveals the reef’s shifting boundaries over geological time. 这种死而复生的涅槃不是只要只此一次而已，根据最新研究显示在地质时期上来看，珊瑚礁不断变动着边界。 It’s a tale that has played out five times over the past 30,000 years—and it may be happening again today. 涅槃传说在过去的三万年里上演了五次—而今天，则可能会再次上演。 The study “holds some really important lessons” for understanding how resilient corals are in the face of change, and how quickly they recover after catastrophic events, says Kim Cobb, a paleoclimatologist at the Georgia Institute of Technology in Atlanta, who wasn’t involved in the work. 这项研究对于我们认识珊瑚礁如何适应环境的改变以及它们在灾难性事件之后多快能恢复“有重要的作用”，吉姆.科布说，她是一名来自亚特兰大的佐治亚技术学院的古气候学家，并未参与此次研究。 Today’s rate of sea level rise is moderate—about 10% of the rate 13,000 years ago—but going forward it may accelerate dramatically, she says. 今天的海平面上升的速率不算很高—约为13000年前速率的10%—不过将来可能会迅速增加，她说。 To conduct the study, scientists used underwater sonar to locate places on the sea floor, beyond the current reef, where corals may have grown in the past. 为了开展这次研究，科学家们利用了水下声纳来定位海床上和目前的珊瑚礁外的位置，这是珊瑚过去曾生长的地方。 Then, they drilled 20 holes, extracting rock cores that contained fossil corals and sediments deposited over the past 30,000 years, spanning part of the last ice age and the warm millennia that followed. 接着，他们钻了20个孔，来提取岩核，其中就版含有过去三万年间的珊瑚化石和沉积物，这段时间包含了最后的冰河时期的一部分还有接下来更为温暖的时期。 The reef migrated up and down during that time, the team found, closely tracking changes in sea level at a rate of up to 20 vertical meters per thousand years. 这支团队发现，珊瑚礁在这段时间里有盛有衰，他们密切追踪着海平面的变化，其速率大约为每千年垂直上升20米。 And when sea level reached its lowest point 21,000 years ago—118 meters below today’s level, its lost water locked up in massive ice caps—corals survived on the outer terraces of Australia’s continental shelf, the team reports today in Nature Geosciences. 而当21000年前海平面到达最低值时—比今天的海平面低118米，损失的水分被锁在了大规模冰架上—位于澳洲大陆架外部区域的珊瑚礁幸存了下来，这支团队今天在《自然地理》上发表了结果。 Scientists have long wondered where the Great Barrier Reef went during the last ice age, says Jody Webster, a marine geologist at The University of Sydney in Australia and the lead author of the study. 科学家们一直好奇在最后一个冰河时期阶段大堡礁去哪儿了，乔迪.韦伯斯特说，她是澳大利亚悉尼大学的一名海洋地质学家，也是这次研究的第一作者。 “We were able to find it.” “我们就能够找到答案。” But the reef couldn’t always keep up with changing sea levels. 不过珊瑚礁并不是总能跟上海平面变化的节奏。 The researchers identified five times when it appeared to die off—twice during the cool down of the last ice age, when falling sea levels exposed corals to air; and three times 10,000 to 17,000 years ago, when glacial melt caused sea levels to rise rapidly. 研究员们发现了有五次，珊瑚礁几乎灭亡的时期—两次是在上个冰河时期冷却期之后，那时下降的海平面使珊瑚礁暴露在了空气中；有三次是在10000到17000年前，当时冰川融化导致海平面迅速上升。 “We haven’t drilled or sampled everything,” says Webster, so he and his colleagues can’t confirm how extensive the die-off was. “我们还没有进行钻探和取样，”韦伯斯特说，于是他和他的同事们还不能确认这种灭绝有多彻底。 But they think corals persisted in some places along the continental shelf during those times, allowing reefs in other locations to re-establish within 2000 years. 不过他们认为在那种时期里大陆架周围某些地方的珊瑚仍然存活着，这样它们才能够在2000年内的时间里在别处复苏。 The historical die-offs are similar to “what we’re seeing right now on the Great Barrier Reef,” says Mark Eakin, a coral reef ecologist at the National Oceanic and Atmospheric Administration in College Park, Maryland, who wasn’t involved in the study. 历史上的灭绝跟“我们今天在大堡礁上看到的情形”相似，马克.埃金说，他是位于马里兰的大学公园国家海洋气候局的珊瑚礁生态学家，并未参与此次研究。 Sea level changes aren’t a huge problem at the moment, but temperatures are: Heat waves have triggered mass bleaching events, periods where heat-stressed corals expel symbiotic algae that live within their tissues. 海平面变化目前还不是大问题，不过温度却是：热浪会引发大规模珊瑚礁白化事件，这时受到热刺激的珊瑚会排出生活在它们体内的共生藻类。 In 2016 alone—the hottest year on record globally—67% of corals died along the northernmost 700 kilometers of the reef. 仅仅在2016年—全球记录上最热的一年—珊瑚礁最北部700公里沿线的67%的珊瑚礁都死去了。 The new research is “yet another reminder” that what we’re doing to the ocean is going to have dramatic consequences, Eakin says. 这次新的研究也在“再次警醒我们”我们对海洋的作为将会有重大的后果，埃金说道。 “Don’t expect reefs to be able to bounce back quickly.” “不要指望珊瑚能够迅速复原。” 感谢关注 跟amber一起看世界 |
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