Exploring ‘Dark Oxygen’: Scientists Research Its Impact in Deep Sea Mining Zones

Scientists are set to deploy instruments to the ocean floor to explore the intriguing process of metal nodules producing oxygen in the Pacific Ocean. This unexpected phenomenon has ignited significant debate regarding the ethics of deep-sea mining.

In a surprising revelation from 2024, researchers identified that a potato-sized formation in the depths of the Pacific and Indian Oceans—including the distinguished Clarion-Clipperton Zone—functions as a vital oxygen source. This discovery challenges the conventional belief that large-scale oxygen production derives solely from sunlight and photosynthesis.

Dubbed “dark oxygen,” this phenomenon sustains life within the abyss, including microorganisms, sea cucumbers, and predatory sea anemones thriving thousands of meters beneath the surface. This finding casts doubt on proposals from deep-sea mining companies aiming to extract cobalt, nickel, and manganese by removing nodules from the ocean floor. A controversial deep-sea mining company was involved in this discovery, prompting a call for further scientific investigation.

Now, the team responsible for discovering dark oxygen is returning to the Clarion-Clipperton Zone, the prime location for potential deep-sea mining, to verify its existence and comprehend the mechanisms behind its production.

“Where does the oxygen come from for these diverse animal communities to thrive?” asked Andrew Sweetman from the Scottish Marine Science Society. “This could be an essential process, and we’re focused on uncovering it.”

The researchers propose that a metallic layer in the nodule generates an electrical current which splits seawater into hydrogen and oxygen. They’ve recorded up to 0.95 volts of electricity on the surface of the nodules—just below the standard 1.23 volts necessary for electrolysis. However, the team suggests that individual nodules or clusters could produce higher voltages.

Plans are underway to deploy a lander, essentially a metal frame housing various instruments, to a depth of 10,000 meters to measure oxygen flow and pH changes, as the electrolysis process releases protons, increasing water acidity.

Given the potential role of microorganisms in this process, the lander will also collect sediment cores and nodules for laboratory analysis. Each nodule is home to approximately 100 million microorganisms, which researchers aim to identify through DNA sequencing and fluorescence microscopy.

“The immense diversity of microorganisms is constantly evolving; we are continually discovering new species,” remarked Jeff Marlow from Boston University. “Are they active? Are they influencing their environment in crucial ways?”

Furthermore, since electrolysis is generally not observed under the intense pressures found on the ocean floor, the team intends to utilize a high-pressure reactor to replicate deep-sea conditions and conduct electrolysis experiments there.

“The pressure of 400 atmospheres is comparable to that at which the Titan submarine tragically imploded,” noted Franz Geiger from Northwestern University. “We seek to understand the efficiency of water splitting under such high pressure.”

The ultimate aim is to carry out electrochemical reactions in the presence of microorganisms and bacteria under an electron microscope without harming the microorganisms.

The United Nations’ International Seabed Authority has yet to decide on the legality of deep-sea mining in international waters, with U.S. President Donald Trump advocating for its implementation. The Canadian company, The Metals Company, has applied for authorization from the U.S. government to commence deep-sea mining operations.

A recent paper authored by Metals Company scientists contends that Sweetman and his colleagues have not produced sufficient energy to facilitate seawater electrolysis in 2024, suggesting the observed oxygen was likely transported from the ocean’s surface by the deployed landers.

Sweetman countered this claim, stating that the lander would displace any air bubbles on its descent, and asserted that oxygen measurement would not have occurred if deployed in other regions, such as the Arctic ocean floor, which is 4,000 meters deep. Out of 65 experiments conducted at the Clarion-Clipperton Zone, he noted that 10% exhibited oxygen consumption while the remainder indicated oxygen production.

Sweetman and his colleagues also discovered that the oxidation phase of the electrolysis process can occur at lower voltages than those recorded on the nodule’s surface. A rebuttal presenting this data has been submitted to Natural Earth Science and is currently under review.

“From a commercial perspective, there are definitely interests attempting to suppress research in this field,” stated Sweetman in response to the Metals Company’s opposition to his findings.

“It is imperative to address all comments, regardless of their origin,” added Marlowe. “That is our current predicament in this process.”