Beau Barker Jorgensen, an expert in marine biogeochemistry who was not involved in the research but reviewed the study, said in an interview that it was a “very unusual finding.”
The findings could have implications for the deep-sea mining industry, whose players are seeking to be allowed to explore the ocean’s depths and extract minerals such as those that make up polymetallic assemblies. Such minerals are seen as crucial for the transition to green energy. Environmental activists and many scientists believe deep-sea mining is dangerous because it can destabilize ecosystems in unpredictable ways and can affect the ocean’s ability to help limit climate change. The study received funding from companies active in seabed exploration.
When Andrew Sweetman, the study’s lead author, first recorded unusual oxygen readings coming from the bottom of the Pacific Ocean in 2013, he thought his research equipment was malfunctioning.
“I basically told my students, just put the sensors back in the box. We’re going to send them back to the manufacturer and test them because they’re just giving us crap,” Sweetman, head of the Seabed Ecology and Biogeochemistry Research Group at the Scottish Marine Science Association, told CNN. “And every time the manufacturer came back, ‘They work. They are calibrated.
In 2021 and 2022, Sweetman and his team returned to the Clarion-Clipperton Zone, an area beneath the central Pacific Ocean known for high abundances of polymetallic nodules. Confident that their sensors were working, they lowered a device more than 13,000 feet below the surface that placed small boxes in the sediment. The boxes remained in place for 47 hours, conducting experiments and measuring the levels of oxygen consumed by the microorganisms living there.
Instead of oxygen levels decreasing, they are increasing – suggesting that more oxygen is being produced than is being consumed.
The researchers hypothesized that the electrochemical activity of the various metals that make up the polymetallic assemblies are responsible for the oxygen production measured by the sensors — like a battery in which electrons flow from one electrode to another, creating an electric current, Tobias Hahn, one of the study’s co-authors, said in an interview.
This hypothesis will add a layer to our understanding of how organisms originated under the sea, said Hahn, who focused specifically on the sensors used in the study’s experiments. “We thought life began on Earth when photosynthesis began because oxygen was brought to Earth through photosynthesis. “It’s possible that this process of electrochemically splitting water into oxygen and hydrogen is actually supplying oxygen to the ocean,” he said.
“This could be a game-changer in the story of how life began,” he added.
A press release for the study said its findings challenge “long-standing assumptions that only photosynthetic organisms, such as plants and algae, generate oxygen on Earth.”
But if this discovery is confirmed, “we have to rethink how we mine” materials such as cobalt, nickel, copper, lithium and manganese underwater, “so that we don’t deplete the source of oxygen for deep-sea life,” said Franz Geiger, professor of chemistry. at Northwestern University and one of the study’s co-authors, in the release.
Undersea mining in the 1980s serves as a cautionary tale, Geiger said. When marine biologists visited such sites decades later, they “found that even the bacteria had not recovered.” But in areas that have not been mined, “sea life thrives.”
“Why such ‘dead zones’ persist for decades is still unknown,” he said. But the fact that they do suggests that seafloor mining in areas with many polymetallic nodules could be particularly harmful, because those areas tend to have more faunal diversity than “the most diverse rainforests,” he said.
Although the study pointed to an interesting new path to sustaining life deep under the ocean, many questions remain, Hahn said. “We just don’t know” how much “dark oxygen” can be created through this process, how it affects the polymetallic nodes, or what amounts of nodes are needed to enable oxygen production, he said.
While the study’s methodology is solid, “what’s missing is an understanding of what’s going on, what kind of process this is,” Barker Jorgensen said.
