Revealing the Mysteries of the Abyss: Dark Oxygen Findings in the Clarion Clipperton Zone

A global team captured attention in 2024 after they uncovered that the metallic nodules currently pursued by deep-sea mining companies were generating ‘dark oxygen’ in the depths of the Clarion Clipperton Zone (CCZ) in the Pacific. These nodules are rich in metals such as nickel, cobalt, and lithium, essential for green technologies, including rechargeable batteries.

The source of ‘dark oxygen’ in the depths of the ocean remains largely unidentified. The nodules themselves could be responsible for oxygen production, with researchers previously proposing that the charged surface of the nodules might create optimal conditions for water electrolysis.

The Nippon Foundation – a Japanese entity interested in global oceans – has recently awarded a $5.2 million (£3.7 million) grant for a three-year initiative to gain deeper insights into this occurrence. This will involve deploying three specially designed landers in the CCZ, reaching up to 6km below sea level later this year.

Mason Wakley engaged with Andrew Sweetman, a biogeochemist at the Scottish Association for Marine Science, who is steering the project.

What are the objectives of this new initiative?

The primary objective is to determine if we can again document the existence of dark oxygen utilizing an entirely new suite of deep-sea equipment.

The secondary objective is to identify the underlying cause of this occurrence. Does it stem from a microbial process? Or is it associated with the chemistry of the sea floor, the nodules, or the manganese oxide particles within the sediments?

The third objective is to conduct additional simulation experiments to observe the effects of sediment burial on the process. Sediments may be resuspended during deep-sea mining activities, potentially revealing electrochemically active regions on the deposits. We suspect these areas could play a role in the oxygen-producing process.

What insights will the experiments provide?

Ideally, they will inform us about the source of the oxygen and the primary mechanisms at play at the seabed. From there, we can enhance our understanding of the process within an environmental framework. For instance, if we find that oxygen and hydrogen production are interconnected, it likely indicates that the process holds ecological significance, as specific microbes may harness hydrogen for cellular synthesis.

What experiments are you planning?

Throughout the voyages, we will measure factors such as oxygen and hydrogen generation, fluctuations in pH, and different elements of the carbonate system. Additionally, we plan to introduce various chemical tracers to the seabed and nodules, including isotopically labeled water, to determine if it can be detected in the dissolved oxygen signals. We will also investigate which microbes are active and whether they are assimilating any chemical tracers, as this should indicate their involvement in oxygen production.

Why is it crucial to comprehend dark oxygen?

Understanding this phenomenon is vital for enhancing our knowledge about the environment we live in. Furthermore, there’s the aspect of deep-sea mining – we lack clarity on whether this process carries ecological importance or what might be driving it. A better understanding of the process is necessary to ascertain if deep-sea mining could cause any detrimental effects. If so, we must strategize to mitigate those impacts.

Such concerns are reasonable – I harbored doubts about the data for eight or nine years. There is a tremendous volume of information that we’ve shared with various