Scientists discover 'dark oxygen' produced without light in the depths of the ocean

“This is a very unusual finding,” said Bo Parker Jorgensen, a marine biogeochemist who was not involved in the research but reviewed the study, in an interview.

The findings could have implications for the deep-sea mining industry, whose players have sought to be allowed to explore the ocean depths and extract minerals such as those that make up polymetallic nodules. It is seen as crucial to the transition to green energy. Environmental activists and many Scientists Believes Deep sea mining is dangerous. Because it could destabilize ecosystems in unexpected ways and could affect the ocean’s ability to help contain climate change. The study received funding from companies involved in seabed mining exploration.

When Andrew Sweatman, 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 had malfunctioned.

“I basically told my students, ‘Just put the sensors in the box. We’ll take them back to the manufacturer and test them because they’re giving us nothing but crap,’” said Sweetman, head of the Seafloor Ecology and Biogeochemistry Research Group at the Scottish Society of Marine Science. He told CNN,“And every time the factory comes back, it says, ‘They work, they’re calibrated.’”

In 2021 and 2022, Sweetman and his team returned to the Clarion-Clipperton Zone, an area beneath the central Pacific Ocean known for its large amounts of polymetallic nodules. Confident that their sensors were working, they lowered a device more than 13,000 feet below the surface to place small boxes in the sediment. The boxes remained in place for 47 hours, running experiments and measuring the levels of oxygen consumed by the microorganisms living there.

Instead of oxygen levels falling, they rose – indicating that more oxygen was being produced than was being consumed.

The researchers hypothesized that the electrochemical activity of the different minerals that make up the polymetallic nodules The neurons in the brain were responsible for producing the oxygen that was measured by the sensors — like a battery in which electrons flow from one electrode to another, creating an electrical current, Tobias Hahn, a study co-author, said in an interview.

“This hypothesis would add a layer to our understanding of how life exists under the sea,” said Han, who focused particularly on the sensors used in the study’s experiments. “We used to think that life began on Earth when photosynthesis began, bringing oxygen to Earth through photosynthesis. It’s possible that this process of electrochemically splitting water into oxygen and hydrogen is what supplied oxygen to the ocean.”

“This may be a change in the story of how life began,” he added.

a Press release on the study The study said its findings challenge “old assumptions that only photosynthetic organisms, such as plants and algae, generate oxygen on Earth.”

But if the discovery is confirmed, “we need to rethink how we extract” materials such as cobalt, nickel, copper, lithium and manganese underwater, “so that we don’t deplete the oxygen source for life in the deep sea,” Franz Jaeger, a professor of chemistry at Northwestern University and a co-author of the study, said in the statement.

Undersea mining in the 1980s is a cautionary tale, says Jaeger. When marine biologists visited such sites decades later, “they found that the bacteria hadn’t even recovered.” But in areas that hadn’t been mined, “marine life thrived.”

“Why these ‘dead zones’ persist for decades is still unknown,” he said. But the fact that they exist suggests that mining seabed minerals in areas with lots of polymetallic nodules could be particularly harmful, because these areas tend to have greater animal diversity than “more diverse tropical rainforests,” he said.

While the study points to an interesting new pathway for supporting life in the deep ocean, many questions remain, Han said. “We don’t know how much ‘dark oxygen’ can be created through this process, how it affects polymetallic nodules or what amounts of nodules are needed to enable oxygen production,” he said.

Although the study's methodology is strong, “what's missing is an understanding of what's going on, and what kind of process it is,” Parker Jorgensen said.