Discovery: "Dark oxygen" is produced on the ocean floor without sunlight

Traditionally, we have always believed that photosynthesis by plants and algae fuel our planet’s oxygen supply, even in the deep ocean, providing the essential gas for life on Earth. However, an international team of scientists has made a startling discovery, finding “dark oxygen” in the deep ocean that challenges this long-held premise.

Their critical finding proves that the Earth’s oxygen could also be generated by metallic minerals on the deep-ocean floor, some 13,000 feet below the surface, where no sunlight penetrates. 

This revelation opens up exciting new possibilities. We can now better understand the origins of oxygen on our planet. It also sheds light on its distribution.

Oxygen with photosynthesis — the norm

Have you ever wondered why we call plants the “lungs” of the Earth? It’s simple: they breathe out what we breathe in. This happens through a fantastic process called photosynthesis.

Imagine a world without trees, plants, or algae. It’s not just a barren, lifeless landscape. It’s a world without oxygen.

Thanks to photosynthesis, plants, algae, and some bacteria are like busy little factories, turning sunlight into the very air we breathe. They’re the unsung heroes of life on Earth.

Here’s an interesting twist. The waste product of our respiration, carbon dioxide, is like gold for plants. They transform it back into oxygen and nutrients in what’s known as the Calvin cycle.

The oxygen we enjoy today didn’t always exist. Thanks to a unique group of photosynthesizing bacteria, our planet’s atmosphere underwent a dramatic makeover 2.4 billion years ago, known as the Great Oxygenation Event. This poured oxygen into our atmosphere, paving the path for more complex forms of life to evolve.

Oxygen withOUT photosynthesis — not normal

Discovering that oxygen is produced at the bottom of the deepest parts of Earth’s ocean, without sunlight or photosynthesis, is stunning as it singles out an unlikely source of oxygen — the seafloor, an area completely devoid of light. 

Previously, it was unthinkable that oxygen-breathing (aerobic) marine life could exist in such darkness. Yet, this discovery is astonishing. It could reshape our understanding of aerobic life’s origin on Earth.

Researcher Andrew Sweetman, who spearheads the Seafloor Ecology and Biogeochemistry research team at the Scottish Association for Marine Science (SAMS), was instrumental in this discovery. 

“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 explains.

“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 in ocean

Polymetallic nodules – natural mineral accumulations on the ocean floor, possessing a mix of various minerals, are central to this discovery. 

These nodules, varying in size, contain critical metals like cobalt, nickel, copper, lithium, and manganese — elements used in batteries.

“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,” asserts Franz Geiger, professor of Chemistry at the Northwestern University and lead experimenter in the electrochemistry tests.

“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.”

Unearthing oxygen in deep ocean

Sweetman recounts the tale of his initial incredulity upon detecting oxygen during his seabed sampling in the Pacific Ocean’s Clarion-Clipperton Zone. 

He initially suspected faulty equipment, given that conventional wisdom dictates oxygen consumption rather than production in deep-sea environments.

“When we first got this data, we thought the sensors were faulty because every study ever done in the deep sea has only seen oxygen being consumed rather than produced,” Sweetman said.

“We would come home and recalibrate the sensors, but, over the course of 10 years, these strange oxygen readings kept showing up.”

The scientists decided to take a back-up method that worked differently to the optode sensors they were originally using. When both methods came back with the same result, they realized they were onto something big.

Geobatteries from deep ocean oxygen

To better comprehend the oxygen production, the researchers explored a hypothesis that relates to the concept of Geobatteries. 

Through a chemical process known as seawater electrolysis, they wondered if the deep-ocean’s polymetallic nodules generated enough electricity to produce oxygen. 

The results were conclusive. “It appears that we discovered a natural ‘geobattery.’ These geobatteries are the basis for a possible explanation of the ocean’s dark oxygen production,” stated Geiger.

Deep ocean oxygen and mining implications

This revelation could have significant implications for the mining industry. 

The researchers emphasize the importance of considering the potential impact on the ocean’s dark oxygen production before planning deep-sea mining activities. 

“In 2016 and 2017, marine biologists visited sites that were mined in the 1980s and found not even bacteria had recovered in mined areas. In unmined regions, however, marine life flourished. Why such ‘dead zones’ persist for decades is still unknown,” Geiger concludes.

“However, this puts a major asterisk onto strategies for sea-floor mining as ocean-floor faunal diversity in nodule-rich areas is higher than in the most diverse tropical rainforests.”

In summary, discovering dark oxygen production in the deep-ocean sets a new direction for our understanding of Earth’s oxygen supply. The implications of this discovery, for both science and industry, are profound.

The full study was published in the journal Nature Geoscience.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–