Scientists this week unveiled what they say is evidence that rocks rich with electric vehicle battery metals — not plants undergoing photosynthesis — are producing large amounts of oxygen at the bottom of the Pacific Ocean, far beyond the reach of sunlight.
The blockbuster discovery, published in the monthly peer-reviewed scientific journal Nature Geoscience, indicates that potato-sized nodules scattered along a swath of the ocean floor called the Clarion–Clipperton Zone between Hawaii and Mexico are using a newly uncovered but poorly understood process to generate what researchers have dubbed “dark oxygen.”
“It shows us that there is a source of oxygen that hadn’t been identified before, it happens without light,” said Franz Geiger, a professor of chemistry at Northwestern University who co-authored the study.
The research, led by Andrew Sweetman, a marine ecologist, scuba diver and professor at the Scottish Association for Marine Science in the United Kingdom, raises questions about the scientific community’s understanding of life in unexplored reaches of the ocean. It may also throw up another obstacle for companies angling to harvest nodules from the ocean floor to extract highly valuable minerals like cobalt, manganese, nickel and copper needed to make EV batteries, cellphones and solar panels.
The Metals Co., a Vancouver-based deep-sea mining exploration company that partially funded the research and is at the forefront of efforts to harvest the nodules in the Clarion-Clipperton Zone, attempted to poke holes in the study. In a statement on its website, the company blasted the research as “flawed,” asserted that authors were unable to get the research published in other journals and said it’s preparing a rebuttal to ensure “accurate” information is available to the public.
According to the report, the company, which is sponsored by the government of Nauru, funded Sweetman and his colleagues’ work through a subsidiary, Nauru Ocean Resources, which holds exploration rights to swaths of the Clarion–Clipperton Zone.
“We were surprised to see such a flawed paper by Sweetman et al. published,” the company wrote. “The methodology and findings raise serious concerns about the validity of their data and conclusions.”
When asked about the company’s criticism of his paper, Sweetman in a statement said he and his colleagues stand fully behind their findings, which were published by a “highly respected academic journal following a stringent and lengthy peer review process.” Sweetman noted that he had for years dismissed data showing the production of “dark oxygen” because he had been taught that sunlight and photosynthesis were necessary for the process, but the data was consistent and undeniable.
Since releasing the study, Sweetman said he’s been approached by other researchers with similar datasets that also show evidence of “dark oxygen production,” which they likewise discarded, assuming their equipment was faulty.
“We were the worst critics of this paper for a long time. For eight years I discarded the data showing oxygen production, thinking my sensors were faulty,” he said. “Once we [realized] something may be going on, we tried to disprove it, but in the end we simply couldn’t.”
Added Sweetman: “We would welcome future peer-reviewed studies that further investigate this phenomenon.”
“Nature Geoscience does not have a preferred narrative,” a spokesperson for the journal told E&E News in an email. “Our editors make decisions on what to publish based solely on whether research submitted to the journal meets our criteria for publication: original scientific research in the Earth Sciences (where conclusions are sufficiently supported by the available evidence) that has been carefully evaluated through a fair and rigorous peer review process. … The statement from The Metals Company does not provide enough information for us to evaluate the validity of their claims.”
‘Dark oxygen’ and murky waters
The coming energy transition has focused the world’s attention on the growing need for raw materials, as well as the environmental trade-offs that come with hardrock mines needed to pump out minerals like lithium, cobalt and nickel.
A growing number of private companies and countries argue that deep-sea mining is a solution, one that avoids the pitfalls of surface mining, including clear-cutting forest and vegetation, blasting, and digging.
Gerard Barron, CEO of Metals, has publicly argued that deep-sea mining will not harm the world’s oceans and the nodules amount to a “battery in a rock,” offering up minerals needed to solve climate change. Barron told Reuters earlier this week that he expects to apply for a mining license later this year and, should the United Nations’ International Seabed Authority sign off, begin production offshore in early 2026.
Metals’ chief financial officer, Craig Shesky, told investors in 2021 that the company anticipates making $31 billion from its two lease areas in the Clarion–Clipperton Zone. The company has also applied for a Defense Department grant to build a plant in Texas to process the nodules it harvests from the ocean floor — a project that could become eligible for tax incentives under the Inflation Reduction Act.
But the company has faced its own share of criticism.
Earlier this week, a group of nonprofit organizations filed a formal complaint with the U.S. Securities and Exchange Commission against Metals for “misleading investors, government officials, and the public through material misrepresentations and omissions.”
When asked about the complaint, Barron in an statement said it’s become “standard practice” for activists to “turn the noise up to 11 at the ISA and this year is no different.” Barron noted that the ISA and its 169 members are making good progress on the mining code. “Meanwhile, it’s a good thing that anyone is free to file a complaint with the SEC, which in 2022 received more than 40,000 tips, complaints, and referrals and commenced 501 new enforcement actions,” he added.
For now, the practice of deep-sea mining is in the exploratory phase.
All eyes are on the ISA as it meets in Jamaica this month to hammer out a “regulatory roadmap” by next year that would govern how companies move forward. A spokesperson for the ISA, when asked about the “dark oxygen” research, said the agency is committed to supporting scientific research in the deep-sea marine environment, and any relevant scientific discoveries will be considered. News of the discovery came one week into the latest round of negotiations.
During the opening session, Chile, Germany, Costa Rica and Spain reiterated their precautionary pause positions against commercial mining until the deep sea can be better understood.
Emma Wilson, a policy officer for the advocacy group Deep Sea Conservation Coalition who is in Jamaica attending the session, said Argentina, Nauru and China all pushed for an accelerated adoption of the mining code, which acts as a trigger for companies to move forward.
At least one of the authors of the report published by Nature Geoscience — Jeffrey Marlow, an assistant professor of biology at Boston University — recently signed a petition calling on the ISA to impose a moratorium on deep-sea mining until scientists understand more about the possible effects of pollution and potential changes to the ocean’s ability to sequester carbon. Marlow did not immediately respond to a request for comment.
The latest research from Sweetman and his colleagues highlights just how much remains unknown about the oceans.
Over the past decade, Sweetman encountered and dismissed data that appeared to show oxygen levels in seabeds were elevated beyond background concentrations, even where light and plants that undergo photosynthesis were absent.
Researchers even ruled out the existence of oxygen-producing microbes and still found elevated oxygen levels. They now hypothesize that the very nodules companies want to mine may be generating an electric current that leads to oxygen formation from ocean water, a process they aim to better understand in future experiments.
Geiger said the research raises a host of new questions about how the nodules work — alone and in large, interconnected networks on the bottom of the ocean — as well as the possible existence of new oxygen sources, from the Earth’s surface to icy moons with massive oceans.
“As a chemist, I’m personally really excited about the fact that there might be a blueprint down there for making catalysts that allow you to do much better electrochemistry for the energy transition up here at the Earth’s surface,” he said.
It could also provide critical insight into the effects of mining the deep seas for valuable EV battery metals, if the world goes in that direction, he added.
“Whether or not the world decides to go in this direction, this work, and hopefully subsequent work, will inform when, how and where to do this,” said Geiger.
