Research published in Nature Geoscience reports that extracting rare metals from the deep sea could generate a form of oxygen referred to as “dark oxygen”. The study describes how polymetallic nodules, which develop over millions of years on the ocean floor, can react with salt water during mining operations. The work also raises the possibility that changes in oxygen conditions could affect deep-sea ecosystems.
How “dark oxygen” forms during nodule disturbance
The study defines “dark oxygen” as oxygen produced without sunlight, drawing a comparison to how conventional batteries release energy. It reports that polymetallic nodules containing metals such as cobalt, lithium, and copper can behave like batteries when disturbed. According to the findings, this process can lead to additional oxygen production.
Potential effects on abyssal plains and deep-sea life
The research indicates that “dark oxygen” production could influence deep-sea ecosystems by altering oxygen levels in abyssal plains. These plains are described as the habitat where the nodules are found, with the seafloor covered in sediment. The area supports multiple marine organisms that depend on existing oxygen conditions.
While the study notes that it is difficult to quantify total oxygen output from the nodules, it states that mining could affect their ability to support deep-sea life. It also cites that oceans produce about half of Earth’s oxygen through photosynthesis by marine organisms. The report says disrupting processes tied to oxygen production could have broader consequences.
Seafloor experiments in the Clarion–Clipperton Zone
To examine the phenomenon, researchers deployed chambers on the seafloor at depths of about 2.6 miles in the Clarion–Clipperton Zone. They observed an increase in oxygen concentration during the experiments. The results were interpreted as consistent with the idea that the nodules’ electrical properties may be involved.
The observations led to a hypothesis described as a “geo-battery,” in which nodules generate voltage comparable to that of AA batteries. This framing connects changes in electrical behavior to measured increases in oxygen concentration under experimental conditions. The study presents these findings as evidence supporting further investigation into mechanisms relevant to mining activities.
More than 800 scientists call for a pause pending further research
The report also highlights a petition signed by over 800 marine scientists requesting a halt on deep-sea mining until additional research is completed. The signatories argue that deep-sea ecosystems are already under stress from climate change, pollution, and bottom trawling. They cite these existing pressures as reasons for caution around new industrial activity.
The findings are presented alongside the need for careful evaluation of environmental impacts before large-scale deep-sea mining proceeds. The study frames its conclusions around potential changes linked to mining operations and their possible implications for seabed ecosystems.