Researchers say the polymetallic nodules that mining companies hope to collect from the deep ocean floor could be a source of oxygen for the animals, plants and bacteria that live there.
This discovery of this “dark oxygen” has the potential to shake up negotiations taking place this month in Jamaica, where a world regulatory body – the International Seabed Authority – is meeting to decide the future of deep-sea mining.
The work was recently published in the journal Nature Geoscience.
“This study is a really good example of how limited our knowledge of the deep ocean is and how much we can benefit from further scientific research,” said Diva Amon, a marine biologist from Trinidad and a postdoctoral researcher. at UC Santa Barbara’s Benioff Ocean Initiative.
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The excitement centers on potato-sized rocks — or polymetallic nodules — found littered across areas of the ocean floor. These nodes contain minerals, such as cobalt and nickel, that batteries and green energy technologies require.
For years, companies such as Canada’s The Metals Co. have been working to convince the international governing authority to greenlight their plans to harvest these metal nodules in the Pacific Ocean’s Clarion Clipper Zone – a stretch of sea that stretches 4,500 miles between Hawaii and Mexico.
The company has argued that metals are essential for building technologies that don’t rely on fossil fuels. They say that the impact that mining will have on the ocean floor is not only minimal, but also does not compare to the destruction of rainforests and human communities that land mining causes.
But environmentalists, oceanographers and others say driving huge harvesting machines across the pristine and little-known ocean floor — on top of and along areas of sediment three and four miles below the surface — could have unforeseen and catastrophic consequences. They are calling on lawmakers to delay or stop the industry from mining one of the last “pristine” ecosystems on the planet.
This new research, which was funded by TMC, suggests that the number of mines in the area may be greater than anyone had imagined.
That’s because a team of international scientists discovered that the precious knots produce oxygen – and may be responsible for enriching this dark and remote ecosystem with one of life’s most important elements.
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Jeffrey Marlow, an assistant professor of biology at Boston University and one of the authors on the paper, said he and his team had received funding from TMC to conduct basic environmental studies, which included sending something to the bottom of the ocean called a benthic chamber.
These structures, which he described as about 10 meters tall — “think of it as an inverted box or something you put on the bottom of the sea,” Marlow said — are watertight and gastight and contain instruments designed to take measurements of the chemistry and composition of the sediment.
The sampling method is fairly standard, he said. Scientists measure the amount of oxygen that is lost, or reduced, over a 48-hour period while the chamber sits in place on the ocean floor. The fall serves as an indicator of the amount of life down there – as animals breathe, they consume oxygen.
But when they sent the chambers for this analysis, they noticed that oxygen levels increased, not decreased.
Marlow said they were sure the machine was faulty. They tried again and observed the same results.
“These benthic chamber experiments have been done around the world for decades,” he said. “So the technology and everything is well established.”
He said they spent days, then weeks troubleshooting.
“We had several redundant ways of measuring it, so we knew none of them were failing. In the end, we were forced to conclude” that oxygen was being produced.
What the researchers think is happening is that the nodes – and the metals in them – are working like a battery, on a chemical level.
“These rocks are made up of minerals that have metals that are … distributed throughout the rock in heterogeneous ways,” he said. “Each of these metals and minerals is able to hold an electrical charge in a slightly different way. So basically, just the natural variation means that there’s charge separation … in the same way that there is in a battery .”
This means there is enough voltage to take the water and “split it into hydrogen and oxygen”.
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But not everyone is convinced or happy with the study’s conclusion.
TMC, which sponsored the research, sent The Times a critique of the paper, saying the research had been rejected by four scientific publications before finding a home in Nature, which the company described as “a journal that has taken a view of strong against deep-sea mineral resources.”
A request for comment went unanswered by the journal’s communications team, but the journal is generally considered one of the most prestigious and selective publications among scientists.
The TMC also said the methodology was flawed, arguing that the team’s findings contradicted other work that had been done in the Clarion Clipper area but used a different method.
“This inability to reproduce the findings with both methods suggests that elevated oxygen levels are actually an artifact in the data,” the company said in a statement. The company noted that it was “currently preparing a peer-reviewed paper in rebuttal.”
Bo Barker Jørgensen, a microbiologist at Denmark’s Aarhus University – who was not involved in the research or on the TMC payroll – said the work raised more questions than answers.
He said he did not “think this discovery is important to our understanding of the ocean in general or to deep-sea mining” and described the research as a “new and very strange process for which the mechanism is not yet known. clearly”.
The study’s authors pushed back against the criticism, stating that they too had been puzzled by their findings – but they would be rigorous in ruling out any other possible scenarios.
“We were the worst critics of this paper for a long time,” said Andrew Sweetman, leader of the Marine Ecology and Biogeochemistry research group at the Assn. Scotland for Marine Science and lead author of the paper. “For eight years I threw away the data showing oxygen production, thinking my sensors were wrong. Once we realized something might be going on, we tried to disprove it, but in the end we just couldn’t.
He said he welcomes more research on the topic and urged other scientists to investigate further.
“After the publication of this paper, I have been contacted by other researchers with similar data sets that also show evidence of dark oxygen production that they dismissed as thinking the equipment was faulty,” he said.
This story originally appeared in the Los Angeles Times.