Dark Oxygen’ and Polymetallic Nodules: A 4,000-Meter Deep-Sea Discovery

Polymetallic nodules in the Clarion-Clipperton Zone (CCZ) produce dark oxygen 4,000 meters below sea level. This discovery may redefine our understanding of how life began on Earth. The study shows that deep-sea ecosystems are complex and not fully understood. The results of the study are important for setting rules about deep-sea mining.

Summary

• Polymetallic nodules are found in the Clarion-Clipperton Zone (CCZ).
• These nodules contain metals vital for green energy technologies.
• A recent study reveals these nodules can produce oxygen in the deep sea.
• This process, called dark oxygen production, occurs without sunlight.
• The discovery could reshape theories about the origins of life on Earth.
• The findings intensify the debate over deep-sea mining.
• The International Seabed Authority (ISA) is considering a moratorium on mining.
• The study emphasizes the need for further research on deep-sea ecosystems.
• Environmental concerns include ocean acidification, deoxygenation, and pollution.
• Policy decisions on deep-sea mining will have long-term impacts on ocean conservation.

Main Article

Nestled between Hawaii and the western coast of Mexico lies the Pacific Ocean’s Clarion-Clipperton Zone (CCZ), a 4.5 million-square-kilometer area of abyssal plain bordered by the Clarion and Clipperton Fracture Zones. This stretch of sea is home to a vibrant ecosystem filled with marine life, but it is best known for its immense collection of potato-sized rocks called polymetallic nodules. These nodules, which number in the trillions, are rich in nickel, manganese, copper, zinc, and cobalt—metals essential for batteries that power a green energy future. However, a groundbreaking study has revealed that these nodules are not just valuable for their metals; they also produce “dark oxygen” 4,000 meters below the sea surface, where sunlight cannot reach.

The Discovery of Dark Oxygen

The Role of Polymetallic Nodules

Polymetallic nodules have long been considered a potential goldmine for the materials needed to transition to green energy. Mining companies often refer to them as a “battery in a rock” because of their high metal content. But the new study published in Nature Geoscience has shown that these nodules play an even more critical role in the ocean’s ecosystem by producing oxygen in the deep sea, a process previously thought impossible.

“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. 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?”

said Andrew Sweetman, a deep-sea ecologist with the Scottish Association for Marine Science and lead author of the study.

The Journey Toward the Discovery

The journey toward this discovery began more than a decade ago when Sweetman started analyzing how oxygen levels decreased with increasing ocean depth. In 2013, sensors unexpectedly returned data showing increased oxygen levels in the CCZ. Initially dismissed as a sensor error, subsequent studies confirmed that the abyssal plain somehow produced oxygen. Sweetman hypothesized that the minerals in the nodules acted as a “geobattery,” separating hydrogen and oxygen via seawater electrolysis.

A 2023 study revealed that various bacteria and archaea can create “dark oxygen.” Sweetman’s team recreated CCZ conditions in a lab and killed off microorganisms with mercury chloride. Surprisingly, oxygen levels continued to rise. They found a voltage of about 0.95 volts on the nodule surfaces, enough to split seawater and produce oxygen.

Implications for Deep-Sea Mining

Environmental Concerns

The discovery of dark oxygen production adds fuel to the debate over deep-sea mining. Mining companies, such as the Metals Company, see these nodules as essential for addressing energy needs. However, 25 countries advocate for a moratorium or precautionary pause on mining to understand its environmental impacts better. This is crucial as the world’s oceans already face numerous challenges, including acidification, deoxygenation, and pollution.

“This is an excellent example of what it means to have the deep ocean as a frontier, a relatively unexplored part of our planet. There are still new processes to discover that challenge what we know about life in our ocean. The production of oxygen at the seafloor by polymetallic nodules is a new ecosystem function that needs to be considered when assessing the impact of deep-sea mining. These findings underscore the importance of furthering independent deep-sea scientific research across the global ocean in order to inform deep-ocean policy,” said Lisa Levin from the Scripps Institution of Oceanography.

The International Seabed Authority (ISA)

The ISA is currently negotiating deep-sea mining regulations. They met for two weeks in April to discuss new elements. The council will follow a “roadmap for further work” until the end of July 2024. As negotiations continue, researchers discovered dark oxygen production. This discovery shows the need for more research. Careful consideration of the potential impacts of deep-sea mining is essential.

Potential for Life Beyond Earth

Enceladus and Europa

The discovery of dark oxygen production not only redefines our understanding of life on Earth but also has implications for the search for life on other planets and moons. The presence of oxygen produced without sunlight suggests that life could exist in similar environments elsewhere in the Solar System. Moons such as Enceladus and Europa, which have subsurface oceans, could potentially harbor life forms that rely on dark oxygen production.

Rewriting the Script on Life’s Origins

This discovery challenges the traditional view that life on Earth began with photosynthetic organisms. If oxygen can be produced in the deep sea without sunlight, it opens up new possibilities for how and where life could have originated. This could lead to a reevaluation of the conditions necessary for life and where we might find it beyond Earth.

Conclusion

The discovery of dark oxygen production by polymetallic nodules in the Clarion-Clipperton Zone is a groundbreaking revelation that could reshape our understanding of life on Earth and beyond. This finding highlights the complexities and unknowns of deep-sea ecosystems and underscores the importance of further research and cautious policy decisions. As the International Seabed Authority continues to negotiate mining regulations, it is crucial to consider the potential environmental impacts and ensure that we protect the ocean’s delicate balance. The future of our planet’s oceans and the potential for life beyond Earth depend on the decisions we make today.

Tables

Metal	Polymetallic Nodule Content (%)
Nickel	1.2
Manganese	27.3
Copper	0.9
Zinc	0.7
Cobalt	0.2

Environmental Issue	Impact on Ocean Ecosystems
Acidification	Damages coral reefs and marine life
Deoxygenation	Reduces habitat for marine species
Pollution	Harms marine animals and habitats
Deep-Sea Mining	Potential disruption of ecosystems

References

1. Sweetman, A. et al. Dark Oxygen Production by Polymetallic Nodules in the Deep Sea. Nature Geoscience.
2. Deep Sea Conservation Coalition. The Importance of Protecting Deep-Sea Ecosystems. Deep Sea Conservation Coalition.
3. Scientific American. New Discoveries in Deep-Sea Oxygen Production. Scientific American.
4. Scripps Institution of Oceanography. (2023). The Impact of Deep-Sea Mining on Marine Ecosystems. Scripps Institution of Oceanography.

Hashtags

#DeepSeaDiscovery, #PolymetallicNodules, #DarkOxygen, #ClarionClippertonZone, #MarineEcosystems, #GreenEnergy, #DeepSeaMining, #OceanConservation, #EnvironmentalResearch, #LifeBeyondEarth