我们汽车和发电厂排放的二氧化碳去哪了？其中一部分最终进入海洋，科学家想知道这对珊瑚礁有何影响。据加州科学院新闻稿称，由丽贝卡·奥尔布赖特和肯·卡尔代拉领导的研究团队在澳大利亚大堡礁对此进行了测试。他们将二氧化碳通入一箱海水，将其泵送到珊瑚礁上，并让其流经珊瑚礁。该海水的酸度被调整至若排放继续不受控制，预计本世纪末将达到的水平。结果显示，珊瑚礁构建碳酸钙的速度变慢了。
Where does the carbon dioxide from our cars and power plants go? Part of it ends up in the ocean, and scientists wanted to know what that does to a coral reef. According to a California Academy of Sciences press release, a team of researchers led by Rebecca Albright and Ken Caldeira tested this on Australia’s Great Barrier Reef. They bubbled carbon dioxide into a tank of seawater, pumped it onto the reef, and allowed it to flow across. The water was made as acidic as it is projected to become by the end of this century if emissions continue unchecked. The reef built up calcium carbonate more slowly.A test on a real reef communityMany previous studies have mainly concentrated on single species or single organisms.
在真实珊瑚礁群落上的测试此前许多研究主要集中在单一物种或单一生物体上。而这项研究的目标更大。研究团队在独树岛周围的礁坪上开展工作，独树岛是大堡礁南部的一个小珊瑚沙洲。新闻稿称，这是首个海洋酸化实验，研究人员向海水中添加二氧化碳使其酸化，然后让其流经自然珊瑚礁群落。这一点很重要，因为珊瑚礁是由珊瑚、藻类和其他生物组成的复杂群落。通过研究整个群落，研究人员可以了解酸化如何影响生态系统以及依赖它的沿海社区。
This one aimed bigger. The team worked on the reef flats surrounding One Tree Island, a small coral cay in the southern Great Barrier Reef. It was the first ocean acidification experiment where researchers added carbon dioxide to seawater to make it acidic and then let it flow across a natural reef community, the press release said. That matters because reefs are complex communities of corals, algae, and other organisms. By studying the whole community, researchers can understand how acidification impacts the ecosystem and the coastal communities that rely on it.
为期30天的实验如何运作奥尔布赖特等人2018年发表在《自然》杂志上的研究描述了一个简单的流程。实验于2016年进行，每天一次，持续30天。其中20天，团队将二氧化碳通入一箱海水，将其泵送到珊瑚礁上，并让其流过珊瑚礁。另外10天，他们运行相同装置但不添加额外二氧化碳，以提供公平对比。他们还投入了染料以追踪水流去向。
How the 30-day experiment workedThe 2018 study by Albright and colleagues, published in Nature, describes a simple routine. The experiment was conducted once a day for 30 days in 2016. On 20 of those days, the team bubbled carbon dioxide into a tank of seawater, pumped it onto the reef, and allowed it to flow over the reef. For the other 10 days, they ran the same setup with no extra carbon dioxide to provide a fair comparison. They also put in a dye to track where the water went.
随后，他们测量了净群落钙化量，即造礁生物沉积碳酸钙以构建骨骼的数量。研究人员的发现论文指出，在添加二氧化碳的那些天里，净群落钙化量降低了 34%。这大约减少了三分之一。作者还提到，在 20 个实验日的每一天，钙化量都出现了统计学意义上的显著下降。他们表示，据他们所知，这是首次在自然环境中通过控制实验得出的此类群落层面的估算。
They then measured net community calcification, the amount of calcium carbonate reef organisms deposit to build their skeletons. What the researchers foundThe paper says that net community calcification was 34% lower on the days with added carbon dioxide. That’s roughly a third less. The authors also mentioned a statistically significant decrease in calcification on each of the 20 experimental days. They say this is, to their knowledge, the first community-level estimate of this type from a controlled experiment in a natural setting.
这与 Albright 和 Caldeira 2016 年的一项研究结果一致。在那项研究中，研究团队降低了海水的酸度，珊瑚构建骨骼的能力随之增强。那项早期研究发现了证据，表明酸化已在减少珊瑚礁的钙化。酸性水为何难倒珊瑚当我们燃烧煤炭、石油或天然气时，会向空气中释放二氧化碳。其中一部分被海洋吸收，并在那里停留数千年。
This is consistent with a 2016 study by Albright and Caldeira. In that study, the team made seawater less acidic, and the corals' ability to build their skeletons improved. That earlier study found evidence that acidification is already reducing reef calcification. Why acidic water is hard on coralWhen we burn coal, oil, or gas, we release carbon dioxide into the air. Some of it is absorbed by the ocean, where it stays for thousands of years.
在那里，它与海水反应生成碳酸，这对珊瑚礁、贝类和其他海洋生物有害。珊瑚礁尤其脆弱，因为珊瑚利用碳酸钙构建骨骼，这一过程称为钙化，而随着水体变得更酸，这一过程变得更加困难。这就像在砖块更难制造时盖房子。为何这与你有关即使你住在远离海岸的地方，珊瑚礁仍以多种方式影响着人们。《自然》论文指出，珊瑚礁为数百万人提供食物，保护海岸线，并每年创造数十亿美元的旅游收入。
There it reacts with seawater and forms carbonic acid, which is harmful to reefs, shellfish, and other marine life. Reefs are particularly vulnerable because corals build their skeletons from calcium carbonate, a process called calcification, and that process gets harder as the water becomes more acidic. It’s like building a house when the bricks are harder to make. Why this matters to youEven if you live far from the coast, reefs still affect people in many ways. Reefs feed millions of people, protect coastlines, and generate billions of dollars a year in tourism, the Nature paper notes.
Caldeira 还指出，渔业和旅游业是附近社区的收入来源。研究结果并不意味着每个珊瑚礁的反应都相同，因为这项研究只考察了一个礁坪。此外还有气候变暖带来的额外危险。
Caldeira also pointed to fishing and tourism as sources of income for nearby communities. The results don’t mean every reef will respond the same way because this study only looked at one reef flat. There is also the added danger of warming due to climate change.
但奥尔布赖特表示，这些发现有力地证明，除非大幅且迅速削减温室气体排放，否则酸化将在未来严重减缓珊瑚礁的生长。削减排放是我们仍可努力的方向。
But Albright said the findings are strong evidence that acidification will severely slow reef growth in the future unless greenhouse gas emissions are cut steeply and rapidly. Cutting emissions is something we can still work on.