The shock discovery that metallic nodules could be producing oxygen in the deep sea made headlines last year – now the team behind it is launching a new project to confirm and explain the findings
By Madeleine Cuff
23 January 2025
Manganese nodules on the sea floor may be a source of oxygen
Science History Images/Alamy
Marine scientists who made headlines last year with their discovery that deep sea nodules could be producing “dark oxygen” are embarking on a three-year research project to explain their findings.
Amid swirling controversy over their research, project lead Andrew Sweetman at the Scottish Association for Marine Science says he hopes the new scheme will “show once and for all” that metallic lumps of rock are sources of deep sea oxygen and start to explain how the process is working. “We know that it’s going on, and what we need to now do is show it again, and then really start getting at the mechanism,” he says.
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Sweetman had spent more than a decade studying life on the sea floor before his shock discovery made headlines in July last year, and confounded the research community. Previously, it was thought that oxygen production relied on the presence of plants, algae or cyanobacteria to perform photosynthesis, powered by sunlight.
But Sweetman’s team found rising oxygen levels on nodule-rich areas of sea floor, thousands of metres below the ocean surface where no light can penetrate and no plants grow. The researchers suggested that the nodules could be acting as “geobatteries”, generating an electric current that splits water molecules into hydrogen and “dark” oxygen, produced naturally without photosynthesis.
Sweetman found himself at the centre of a media storm. Life changed overnight, he says – he even gets stopped on the street by people wanting a photograph with him. “It’s been very surreal,” he says.