深海海底矿藏中发现“暗氧”
Baffling new results show that rocklike mineral deposits in the deep sea can produce oxygen
令人困惑的新结果表明深海中的岩石矿物沉积物可以产生氧气
本文作者:ALLISON PARSHALL
Gerard Barron, CEO of the Metals Company, holds a polymetallic nodule. The company helped fund new research that found that such nodules can produce oxygen without sunlight. Carolyn Cole/Los Angeles Times via Getty Images
金属公司首席执行官杰拉德·巴伦 (Gerard Barron) 手里拿着一颗多金属结核。该公司资助了一项新研究,发现此类结核无需阳光即可产生氧气。卡罗琳·科尔/洛杉矶时报来自盖蒂图片社
The flat, pitch-black seabed of the Pacific Ocean’s Clarion-Clipperton Zone (CCZ) is littered with what looks like hunks of charcoal. These unassuming mineral deposits, called polymetallic nodules, host a unique deep-sea ecosystem, much of which scientists have yet to catalog. And the deposits are also a key target for companies that are looking to mine the deep sea because they contain metals, such as manganese and cobalt, that are used to make batteries.
太平洋克拉里昂-克利珀顿区 (CCZ) 平坦、漆黑的海底散落着看起来像大块木炭的东西。这些不起眼的矿藏被称为多金属结核,拥有独特的深海生态系统,其中大部分生态系统尚未被科学家编目。这些矿床也是寻求深海开采的公司的主要目标,因为它们含有用于制造电池的锰和钴等金属。
Now researchers have discovered that these valuable nodules do something remarkable: they produce oxygen and do so without sunlight. “This is a totally new and unexpected finding,” says Lisa Levin, an emeritus professor of biological oceanography at the Scripps Institution of Oceanography, who was not involved in the research. The oxygen gas on planet Earth is typically understood to come from living organisms that convert sunlight, carbon dioxide and water into oxygen and sugar. The idea that some of the gas may come from these inanimate minerals and be produced in total darkness “really strongly goes against what we traditionally think of as where oxygen is made and how it's made,” says Jeffrey Marlow, a microbiologist at Boston University and a co-author of the study, which was published on Monday in Nature Geoscience.
现在研究人员发现这些有价值的结核有一些非凡的作用:它们在没有阳光的情况下产生氧气。 “这是一个全新的、意想不到的发现,”斯克里普斯海洋学研究所生物海洋学名誉教授丽莎·莱文(Lisa Levin)说,她没有参与这项研究。地球上的氧气通常被认为来自将阳光、二氧化碳和水转化为氧气和糖的生物体。波士顿大学微生物学家杰弗里·马洛 (Jeffrey Marlow) 表示,认为某些气体可能来自这些无生命矿物并在完全黑暗的情况下产生的想法“与我们传统上认为的氧气产生地点和产生方式相悖”。该研究的合著者于周一发表在《自然地球科学》杂志上。
The story of discovery goes back to 2013, when deep-sea ecologist Andrew Sweetman was facing a frustrating problem. He was part of a research team that had been trying to measure how much oxygen organisms on the CCZ seafloor consumed. The researchers sent landers down more than 13,000 feet to create enclosed chambers on the seabed that would track how oxygen levels in the water fell over time.
这个发现的故事可以追溯到 2013 年,当时深海生态学家安德鲁·斯威特曼 (Andrew Sweetman) 面临着一个令人沮丧的问题。他是一个研究小组的成员,该小组一直试图测量 CCZ 海底生物消耗的氧气量。研究人员将着陆器送入超过 13,000 英尺的深海,在海底创建封闭室,用于追踪水中氧气含量随时间下降的情况。
But oxygen levels did not fall. Instead they rose significantly. Thinking the sensors were broken, Sweetman sent the instruments back to the manufacturer to be recalibrated. “This happened four or five times” over the course of five years, says Sweetman, who studies seafloor ecology and biogeochemistry at the Scottish Association for Marine Science. “I literally told my students, ‘Throw the sensors in the bin. They just do not work.’”
但氧气含量并没有下降。相反,它们显着上升。斯威特曼认为传感器损坏了,于是将仪器送回制造商进行重新校准。在苏格兰海洋科学协会研究海底生态学和生物地球化学的斯威特曼说,在五年的时间里,“这种情况发生了四五次”。 “我确实告诉我的学生,‘把传感器扔进垃圾桶。它们就是不起作用。’”
Then, in 2021, he was able to go back to the CCZ on an environmental survey expedition sponsored by a deep-sea mining firm called the Metals Company. Again, his team used deep-sea landers to make enclosed chambers on the seafloor. The chambers enclosed encased sediment, nodules, living organisms and seawater and monitored oxygen levels. Sweetman and his team used a different technique to measure oxygen this time, but they observed the same strange results: oxygen levels increased dramatically.
然后,在 2021 年,他得以重返 CCZ,参加由一家名为 Metals Company 的深海采矿公司赞助的环境调查考察。他的团队再次使用深海着陆器在海底建造封闭的房间。这些室封闭了沉积物、结核、生物体和海水,并监测氧气水平。斯威特曼和他的团队这次使用了不同的技术来测量氧气,但他们观察到了同样奇怪的结果:氧气水平急剧增加。
“Suddenly I realized that … I’d been ignoring this hugely significant process, and I just kicked myself,” Sweetman says. “My mindset completely changed [to] focus on what is causing this.”
“我突然意识到……我一直忽视了这个非常重要的过程,我只是踢了自己一脚,”斯威特曼说。 “我的心态完全改变了,专注于造成这种情况的原因。”
“My first thought was microbiology, and that’s because I’m a microbiologist,” Marlow says. It wasn’t a far-fetched idea: scientists had recently uncovered some ways that microbes such as bacteria and archaea could generate “dark oxygen” in the absence of sunlight. In lab tests that reproduced conditions on the seafloor in the new study, the researchers poisoned the seawater with mercury chloride to kill off microbes. Yet the oxygen levels still increased.
“我的第一个想法是微生物学,那是因为我是一名微生物学家,”马洛说。这并不是一个牵强的想法:科学家最近发现了细菌和古细菌等微生物在没有阳光的情况下产生“暗氧”的一些方法。在新研究中重现海底条件的实验室测试中,研究人员用氯化汞毒害海水以杀死微生物。然而氧气含量仍然增加。
If this dark oxygen didn’t come from a biological process, then it must have come from a geological one, the researchers reasoned. They tested and ruled out a few possible hypotheses—such as that radioactivity in the nodules was separating oxygen out of the seawater or that some other environmental factor was separating oxygen gas out of the manganese oxide in the nodules.
研究人员推断,如果这种暗氧不是来自生物过程,那么它一定来自地质过程。他们测试并排除了一些可能的假设,例如结核中的放射性正在将氧气从海水中分离出来,或者其他一些环境因素正在将氧气从结核中的氧化锰中分离出来。
Like most of the deep ocean, the seafloor of the CCZ is a “poorly understood ecosystem,” Levin says. “We haven’t even discovered most of the species in the deep sea, let alone studied them.”
莱文说,与大多数深海一样,CCZ 的海底是一个“人们知之甚少的生态系统”。 “我们甚至还没有发现深海中的大部分物种,更不用说研究它们了。”
Deep-sea mining projects proposed across the CCZ would extract nodules from swaths of the seafloor. The International Seabed Authority (ISA), which governs the seafloor in international waters, is currently discussing rules and regulations for mining the nodules and other deep-sea targets. Twenty-seven nations, including 26 member states of the ISA, have called for a moratorium, precautionary pause or ban on deep-sea mining.
拟议的跨越CCZ的深海采矿项目将从大片海底提取结核。管理国际水域海底的国际海底管理局(ISA)目前正在讨论开采结核和其他深海目标的规则和条例。包括 26 个 ISA 成员国在内的 27 个国家呼吁暂停、预防性暂停或禁止深海采矿。
“I don’t think [this research is] a ‘nail in the coffin’ for deep-sea mining—that has never been the intention,” Sweetman says. “It’s just another thing that we now need to take into account when it comes to deciding, ‘Do we go and mine the deep ocean, or don’t we?’ To me, that decision needs to be based on sound scientific advice and input.”
“我不认为[这项研究]是深海采矿的‘棺材钉’——这从来都不是目的,”斯威特曼说。 “这只是我们现在在决定‘我们是否去深海采矿?’时需要考虑的另一件事,对我来说,这个决定需要基于合理的科学建议和输入。”