Metallic minerals on the deep-ocean floor split water to generate ‘dark oxygen,’ new study finds

Location of the Clarion-
Clipperton Zone [credit: USGS]

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Report: “It appears that we discovered a natural ‘geobattery,’” Geiger said. “These geobatteries are the basis for a possible explanation of the ocean’s dark oxygen production.” But it raises an issue for deep-sea mining of rare earth minerals for batteries etc., potentially in the same zone. When researchers revisited a deep sea area mined in the 1980s they found a ‘dead zone’, contrary to expectations of a marine recovery.
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An international team of researchers, including a Northwestern University chemist, has discovered that metallic minerals on the deep-ocean floor produce oxygen—13,000 feet below the surface, reports Phys.org.

The surprising discovery challenges long-held assumptions that only photosynthetic organisms, such as plants and algae, generate Earth’s oxygen.

But the new finding shows there might be another way. It appears oxygen also can be produced at the seafloor—where no light can penetrate—to support the oxygen-breathing (aerobic) sea life living in complete darkness.

The study, “Evidence of dark oxygen production at the abyssal seafloor,” was published July 22 in the journal Nature Geoscience.

Andrew Sweetman, of the Scottish Association for Marine Science (SAMS), made the “dark oxygen” discovery while conducting ship-based fieldwork in the Pacific Ocean. Northwestern’s Franz Geiger led the electrochemistry experiments, which potentially explain the finding.

“For aerobic life to begin on the planet, there had to be oxygen, and our understanding has been that Earth’s oxygen supply began with photosynthetic organisms,” said Sweetman, who leads the Seafloor Ecology and Biogeochemistry research group at SAMS. “But we now know that there is oxygen produced in the deep sea, where there is no light. I think we, therefore, need to revisit questions like: Where could aerobic life have begun?”

Polymetallic nodules—natural mineral deposits that form on the ocean floor—sit at the heart of the discovery. A mix of various minerals, the nodules measure anywhere between tiny particles and an average potato in size.

“The polymetallic nodules that produce this oxygen contain metals such as cobalt, nickel, copper, lithium and manganese—which are all critical elements used in batteries,” said Geiger, who co-authored the study.

“Several large-scale mining companies now aim to extract these precious elements from the seafloor at depths of 10,000 to 20,000 feet below the surface. We need to rethink how to mine these materials, so that we do not deplete the oxygen source for deep-sea life.”
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A new consideration for miners
The researchers agree that the mining industry should consider this discovery before planning deep-sea mining activities. According to Geiger, the total mass of polymetallic nodules in the Clarion-Clipperton Zone alone is enough to meet the global demand for energy for decades. But Geiger looks to mining efforts in the 1980s as a cautionary tale.

“In 2016 and 2017, marine biologists visited sites that were mined in the 1980s and found not even bacteria had recovered in mined areas,” Geiger said.

Full report here.
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Image: Location of the Clarion-Clipperton Zone [credit: USGS]