Experts have been thrown by the discovery of deep sea ‘dark oxygen’.

Researchers exploring the depths of the Pacific Ocean have discovered a phenomenon that challenges the traditional understanding of oxygen production. 

An international team of scientists, while preparing for deep-sea mining operations, found that oxygen was being produced in complete darkness at a depth of 4,000 metres below the ocean's surface. 

This discovery, documented in Nature Geoscience, suggests that deep-sea nodules can generate what is being termed ‘dark oxygen’.

The nodules are small, rock-like formations found on the ocean floor. They are rich in metals such as iron, manganese, cobalt, and rare-earth elements.

Conventional wisdom has long held that oxygen in the ocean is primarily produced by photosynthetic organisms such as plants and algae, which require sunlight to create oxygen. However, the team found that polymetallic nodules on the seabed are capable of producing oxygen through a different mechanism. These nodules act like small batteries, using electrical properties to split seawater into hydrogen and oxygen, independent of sunlight.

Andrew Sweetman, a leading scientist on the project, and his colleagues conducted experiments using chambers placed on the seafloor at approximately 4,200 metres deep.

These experiments, conducted across multiple locations spanning 4,000 kilometres in the Clarion-Clipperton Zone of the central Pacific Ocean, consistently showed a steady increase in oxygen concentration over a two-day period. Laboratory analyses confirmed that the polymetallic nodules were the source of this oxygen.

This finding has significant implications for the understanding of deep-sea ecology and the potential impacts of deep-sea mining. 

Polymetallic nodules are targeted for their economic potential in advanced and low-carbon energy technologies. However, their role in producing oxygen in the deep sea suggests they may be critical to supporting these ecosystems.

Sweetman and his team hypothesise that the nodules' ability to generate oxygen could be a vital support for deep-sea life. 

The electrical properties of these nodules, which enable them to produce oxygen, may play a significant role in sustaining these ecosystems. 

This raises concerns about the environmental impact of mining the materials. 

If these nodules are removed it could disrupt the oxygen supply and the delicate balance of deep-sea ecosystems.

The discovery of ‘dark oxygen’ not only raises questions about the origins of oxygen production but also prompts a reevaluation of how life might have started on Earth. 

It opens new avenues for research into the potential existence of other unknown biological processes in the deep sea and their implications for life on Earth.

Further research is needed to fully understand the broader implications of this discovery and to develop strategies that mitigate the environmental impacts of deep-sea mining.