Submitted by Michael Frankfort @mfrank_76

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Evidence of dark oxygen production at the abyssal seafloor

Nature Geoscience (2024)

The article discusses experiments conducted on the abyssal seafloor of the Pacific Ocean, specifically in the Clarion-Clipperton Zone (CCZ), to investigate oxygen consumption by deep-seafloor organisms. The researchers utilized in situ benthic chamber experiments to measure sediment community oxygen consumption (SCOC) but discovered unexpected oxygen production instead. This phenomenon, termed “dark oxygen production” (DOP), resulted in oxygen levels increasing to more than three times the background concentration over 47 hours in some experiments.

To ensure the results weren’t due to experimental artifacts, the researchers ruled out various potential errors, such as air bubble diffusion, contamination, and external oxygen intrusion. They also conducted ex situ experiments, which further confirmed the occurrence of DOP, even when biological activity was inhibited. The consistent link between DOP and the presence of polymetallic nodules on the seafloor led the researchers to hypothesize that the oxygen increase might be due to seawater electrolysis driven by the nodules’ high electrical potentials.

The study explored the possibility that these nodules, which contain metal oxides like manganese and nickel, might act as catalysts for electrochemical reactions, resulting in oxygen production. The researchers measured electrical potentials on the nodule surfaces and found variations up to 0.95 V, supporting the idea that these “geo-batteries” could be contributing to the observed DOP. However, the study emphasizes that more research is needed to fully understand the mechanisms behind DOP, its spatial distribution, and its potential impact on deep-sea ecosystems, particularly in the context of future deep-sea mining activities.