A study analyzing these modules reveals that these rocky lumps are capable of producing “dark oxygen” 4,000 meters below sea level where light cannot reach. This unexpected source of “dark oxygen,” as it’s called, redefines the role these nodules play in the CZZ. But we now know that there is oxygen produced in the deep sea, where there is no light. The production of oxygen at the seafloor by polymetallic nodules is a new ecosystem function that needs to be considered when assessing the impact of deep-sea mining. The ISA is still negotiating with key players on deep-sea mining regulations.