Manganese nodules on the ocean floor may be a source of oxygen
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Marine scientists who made headlines last year for their discovery that deep-sea nodules may be producing “dark oxygen” are embarking on a three-year research project to explain their discovery.
Amid controversy surrounding their research, project leaders andrew sweetman He, from the Scottish Marine Science Society, said the new project “conclusively shows” that chunks of metallic rock are the source of deep-sea oxygen and begins to explain how the process works. He says he is looking forward to it. “We know it’s happening, and what we have to do now is show it again and start to really understand its mechanisms,” he says. .
Sweetman previously spent more than 10 years studying seafloor life. his shocking discovery It made headlines last July and confused the research community. Previously, it was thought that oxygen production relied on the presence of plants, algae, or cyanobacteria to perform photosynthesis using sunlight.
But Sweetman’s team found that oxygen levels were elevated in nodules on the ocean floor, thousands of meters below the ocean’s surface, where there is no light and no plants can grow. The researchers suggested that the nodule may act as a “geobattery”, generating an electrical current that splits water molecules into hydrogen and “dark” oxygen, which are produced naturally without photosynthesis.
Sweetman found himself at the center of a media storm. His life changed overnight, he says. He was sometimes stopped on the street by people who wanted to take pictures with him. “It was very surreal,” he says.
But this discovery also brought challenges. The research has drawn criticism from some scientists and deep-sea mining companies who plan to mine the nodules for valuable materials needed for the transition to green energy.
Metals Company (TMC), which funded some of the research that led to Sweetman’s 2024 paper, has been one of the companies that has been the most vocal critic of Sweetman’s findings. The scientist announced that paper It claims the findings are “completely unsupported” by the evidence, raising concerns about the study’s methodology.
They argue that faulty equipment or misuse of the lander may have resulted in the anomalous measurements, and that other researchers using similar procedures have been unable to reproduce their findings. They also raise questions about the data used in Sweetman’s study, claiming the study relied on flawed and inadequate data.
“After decades of research using the same method, no reliable scientist has reported evidence of ‘dark oxygen,'” Gerald Barron, CEO and chairman of The Metals Company, said in a statement. ” he said. “Extraordinary claims require extraordinary evidence. We’re still waiting.”
The journal that published Sweetman’s research has also raised concerns. natural earth science. “We have investigated [these concerns] Follow established processes carefully. However, any action, if any, has not been decided at this time,” a spokesperson for the magazine said. new scientist.
Sweetman maintains that his research is accurate and that he intends to respond to TMC’s criticisms in a formal rebuttal of TMC’s paper. But he says the experience at the center of the controversy was “extremely exhausting” and upsetting. “There was a lot of discussion. A lot of mining companies were saying different things, a lot of which wasn’t very good, and it was difficult to get past that,” he says. “It definitely affected me a little bit. Online bullying is never good to be exposed and it continues.”
Mr Sweetman’s new research project, funded by a £2 million grant from Japanese charity the Nippon Foundation, aims to put some of the controversy to rest. Sweetman’s team will use a modern, custom-built lander that can descend to 12,000 meters above sea level, double the depth reached in previous studies, to hunt specifically for dark oxygen production in the Pacific Ocean. It is.
The first of three research expeditions is scheduled to set sail from San Diego, California, in January 2026, with the aim of confirming the latest data on oxygen production by nodules in the deep ocean. The lander will again seal off samples of water and sediment from the ocean floor to measure changes in oxygen levels. The researchers also plan to test for the presence of hydrogen, which would be produced if electrolysis of seawater occurred. Then, isotopically labeled water is injected into the sample to track chemical changes in the elements.
Sweetman is bullish about the prospects for discovering dark oxygen production. “know the Happening. I’ve found this in 6 places now. “I know I’ll find it,” he says.
Two further studies will investigate what microbial or electrochemical mechanisms are involved and will begin investigating the potential contribution of dark oxygen production in deep-sea ecosystems. This was the first study of its kind to directly investigate these processes, and Sweetman’s initial discovery was, by his own admission, “accidental.” “We didn’t set out to show this. We just started measuring ocean floor respiration,” he says of his initial research.
Sweetman said NASA is also interested in studying nodules to investigate whether similar processes may support life on other moons and planets.
Deep-sea mining companies will be monitoring the project closely. They hope to begin operations later this year, but are still waiting for the International Seabed Authority to finalize rules for deep-sea mining. Further evidence of oxygen production in the deep sea would deal a serious blow to their hopes of establishing a mining industry on the ocean floor.
Sweetman argues that companies should refrain from seabed mining until scientists know more about the potential role of dark oxygen production in marine ecosystems. “All we’re asking for is a little more time to go out and try to understand what’s going on,” he says.
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