Deep-sea mining and oxygen levels on the Pacific Ocean floor: Evidence of a gradual development of complex marine life around a billion years ago

A few years ago a team of biologists went back to areas that were mined decades ago and found no living creatures. “And then a few hundred meters over to the left and right, where the nodules were intact, plenty of life.”

The researchers think they’ve seen dark oxygen on the Pacific Ocean floor, a possibility that could challenge commonly held beliefs about the production of oxygen.

Sweetman said that the nodules might be able to split the ocean into hydrogen and oxygen using their electric charge.

Nicholas Owens, the director of the Scottish Association for Marine Science, said that there was a gradual development of complex life thereafter because of the Oxygen produced around three billion years ago. “The potential that there was an alternative source requires us to have a radical rethink.”

Researchers conducted tests on the seafloor and also collected samples to test aboveground, and they came up with the same result: that oxygen levels increased near the polymetallic nodules.

The polymetallic nodules contain a number of metals that can be used to make the batteries used in electric vehicles and consumer electronics.

Franz Geiger, a Northwestern University chemistry professor who worked on the study, said in a separate news release that there may be enough polymetallic nodules in an area of the Pacific Ocean called the Clarion-Clipperton Zone to meet global energy demands for decades after.

“We need to be really careful if it turns out that deep-sea mining will become an opportunity that’s being pursued … that’s done on a level and at a frequency that is not detrimental to life down there,” Geiger told NPR.

Companies conducted exploratory missions for deep-sea mining in the 1970s and ’80s, he said, and recent research suggests that those missions may have had repercussions on marine life in the area for decades.

“I think we therefore need to revisit questions like: where could aerobic life have begun?” said Andrew Sweetman, a professor with the Scottish Association for Marine Science in Oban, Scotland, in a news release.

In 2021, the same finding was repeated but using a different measurement approach. The scientists were assessing changes in oxygen levels inside a benthic chamber, an instrument that collects sediment and seawater to create enclosed samples of the seabed environment. The instrument gave them the ability to analyze how oxygen is being consumed bybacteria in a sample environment. Oxygen in the benthic chamber should have dropped over the course of time but it went up despite the dark conditions.

How the nodules produce oxygen, however, is not entirely clear: It’s not known what generates the electric current, whether the reaction is continuous, and crucially, whether the oxygen production is significant enough to sustain an ecosystem.

Then there’s an even bigger question: What if the electrolysis induced by the polymetallic nodules was the spark that started life on Earth? According to Sweetman, this is an exciting hypothesis that should be explored further. It is possible that this could become a source of alien life on other worlds.

There are many unanswered questions and some are casting doubt on the findings. The biggest criticisms have come from within the seabed-mining world: Patrick Downes of the Metals Company, a seabed-mining company that works in deep water—the same waters Sweetman studied and that partly funded Sweetman’s research—says the results are the result of oxygen contamination from outside sources, and that his company will soon produce a paper refuting the thesis put forward by Sweetman’s group.