Researchers find evidence of deep sea bed minerals producing oxygen

Researchers have found that metallic minerals on the deep-ocean floor produce oxygen 13,000 feet below the surface -- a claim that challenges the assumptions that only photosynthetic organisms, such as plants and algae, generate Earth's oxygen.

The findings published in the journal Nature Geoscience suggest that oxygen can be produced on the seafloor where no light can enter to support oxygen-breathing sea life living in complete darkness.

Andrew Sweetman, of the Scottish Association for Marine Science (SAMS), while conducting ship-based fieldwork in the Pacific Ocean, made the "dark oxygen" discovery.

Northwestern University's Franz Geiger led the electrochemistry experiments, which explain the findings.

"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," Sweetman, who leads the Seafloor Ecology and Biogeochemistry research group at SAMS, said, according to Science Daily.

"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?"

Natural mineral deposits that form on the ocean floor, called polymetallic nodules, is 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," he added.

Sweetman made the discovery while sampling the seabed of the Clarion-Clipperton Zone, a mountainous submarine ridge along the seafloor that extends nearly 4,500 miles along the northeast quadrant of the Pacific Ocean. When his team detected oxygen, he assumed the equipment must be broken.

Researchers wondered if the deep ocean's polymetallic nodules generated enough electricity to produce oxygen. This chemical reaction is part of a process called seawater electrolysis, which pulls electrons out of water's oxygen atom.

While investigating, Sweetman found just 1.5 volts, the same voltage as a typical AA battery, is enough to split seawater. The team recorded voltages of up to 0.95 volts on the surface of single nodules and when multiple nodules are clustered together, the voltage tended to be much more significant, just like when batteries are connected in a series.

"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."

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