The discovery of oxygen production by manganese nodules in the deep sea could revolutionize our understanding of the origins of life on Earth and have significant implications for deep-sea mining debates.
Unexpected oxygen in the abyss
In a recent study, researchers have detected oxygen at the bottom of the deep sea, apparently produced by manganese nodules. This discovery, made at depths of around 4,000 meters in the Clarion-Clipperton Zone, challenges long-held beliefs about oxygen production in lightless environments.
Andrew Sweetman, a marine ecologist from the Scottish Association of Marine Science, expressed his initial disbelief: “When we first received this data, we thought the sensors were faulty, because every study ever conducted in the deep sea only showed oxygen consumption, not production.” For eight to nine years, researchers assumed their measurements were incorrect.
The oxygen produced in these depths is termed “dark” oxygen, as it’s generated without sunlight, which is typically necessary for photosynthesis and large-scale oxygen production. Surprisingly, this oxygen seems to be produced not by living organisms but by the manganese nodules themselves, potentially acting as small geobatteries.
Implications for life’s origins
This finding could have profound implications for theories about the origin of life on Earth. The possibility of abiotic oxygen production in the deep sea opens up new avenues for understanding how aerobic life might have evolved.
Sweetman explains, “For aerobic life to emerge on the planet, oxygen had to be present, and our understanding was that Earth’s oxygen supply began with photosynthetic organisms. But now we know that oxygen is also produced in the deep sea where there’s no light. I think we need to reconsider questions like: Where might aerobic life have begun?”
The study’s results were confirmed through laboratory experiments, where researchers poisoned samples with mercury chloride to rule out microorganism involvement in oxygen production.
Deep-sea mining concerns
This discovery comes amid ongoing negotiations in Kingston, Jamaica, regarding deep-sea mining of metal-rich manganese nodules for use in technologies like batteries. The study’s findings add a new dimension to these discussions.
Franz Geiger, a chemist involved in the study, points out the potential long-term impacts of nodule removal: “In 2016 and 2017, marine biologists visited sites where manganese nodules were mined in the 1980s and found that not even bacteria had recovered there. Why such ‘dead zones’ persist for decades is still unknown. However, this is a major setback for seabed mining strategies.”
Interestingly, The Metals Company, which largely funded the study, has expressed reservations about its results. Patrick Downes from the company stated he had “serious reservations” about the findings and suggested the results might be due to oxygen contamination from external sources.
Future research and policy implications
While the study cannot quantify the exact amount of oxygen produced in the deep-sea floor or confirm whether it significantly sustains local ecosystems, it raises important questions for further research.
The findings may influence ongoing debates about deep-sea mining. Many countries, including Germany, are advocating for a precautionary pause or moratorium on deep-sea mining. German Federal Environment Minister Steffi Lemke stated in November 2022, “Deep-sea mining would further stress the oceans and irreversibly destroy ecosystems. Therefore, as a first step, we are advocating for a pause and no hasty decisions at the expense of the marine environment.”
As negotiations continue in Kingston, the potential ecological importance of manganese nodules beyond their mineral value becomes increasingly clear. This discovery underscores the need for comprehensive understanding of deep-sea ecosystems before any mining activities are approved, potentially reshaping the future of deep-sea resource exploitation and our understanding of life’s origins on Earth.
