Dark oxygen production

Dark Oxygen Production (DOP) was a hypothesis published by Sweetman et al. (2024) to explain anomalous data from experiments in the Clarion-Clipperton Zone, Pacific ocean. These experiments recorded rising oxygen for the first few hours, when previous experiments of the same type had only ever recorded reducing oxygen due to consumption by benthic organisms.

In order to explain this phenomenon, Sweetman et al. claimed that manganese nodules, which were present in many of the experiments, must be responsible for the oxygen production. It was thus given the name "dark oxygen production", borrowing the term "dark oxygen" that had previously been used for oxygen production by bacteria without sunlight. Sweetman et al. claimed that in this case the oxygen was being produced by electrolysis, using measured voltages from the surface of the nodules as evidence. The article, published in nature geoscience, was widely reported in mainstream media and social media, and contributed to the ongoing debate around deep sea mining. However, it has since emerged that there are many problems with the theory, and may even be an example of scientific misconduct since contrary results and pertinent information were omitted from the article. The omitted data showed that manganese nodules could not have been responsible for the phenomenon. A collaborative rebuttal published by leading scientists and industry experts instead claims that the rising oxygen levels are just experimental artefact, and not due to any natural phenomenon. Sweetman et al. have publicly stepped back from the two main conclusions in the article; that manganese nodules produce oxygen, and that they do this by electrolysis. Retraction of the paper has been called for by independent scientists.