‘Dark Oxygen’: What It Is and Why It’s Surprising to Discover at the Bottom of the Ocean

A new study has revealed that “dark oxygen” is being produced deep in the ocean, a substance that is generated by pieces of metal on the sea floor.

About half of the oxygen we breathe comes from the ocean. But before this discovery, it was thought that this gas was a product of photosynthesis in marine plants, which requires sunlight.

In this case, at a depth of five kilometers, where sunlight cannot penetrate, The oxygen appears to be produced by natural mineral “nodules” that split seawater (H2O) into hydrogen and oxygen..

Several mining companies have plans to harvest these nodules. But marine scientists fear that doing so could disrupt the newly discovered process and harm any marine life that depends on it.

“I first saw this in 2013,” explains lead researcher Professor Andrew Sweetman, from the Scottish Marine Science Association. “A huge amount of oxygen was being produced on the seafloor in complete darkness.”

“I just ignored it, because I learned that oxygen is obtained through photosynthesis.“

“Over time, I realised that I had been ignoring this huge discovery for many years,” Sweetman told BBC News.

He and his colleagues conducted their research in a deep-sea area between Hawaii and Mexico, part of a vast expanse of seafloor covered in mineral nodules.

Nodules form when minerals dissolved in seawater accumulate on shell fragments or other debris. It’s a process that takes millions of years.

Since these nodules contain minerals such as lithium, cobalt and copper (all of which are essential for making batteries), many mining companies are developing technology to collect them and bring them to the surface.

The dark oxygen produced by the nodules could also support life on the seafloor, says Professor Sweatman. His discovery, published in the journal Nature Geoscience, Raises fresh concerns over risks of deep-sea mining plans.

Scientists have discovered that mineral nodules can produce oxygen. Specifically because they work like batteries.

“If you put a battery in seawater, bubbles start to form,” Professor Sweetman explained.

“This is because the electric current actually separates the seawater into oxygen and hydrogen (which are the bubbles). “We think this is what happens with these nodules in their natural state.”

“It’s like a flashlight battery,” he added. “You put a battery in it and it doesn’t turn on. You put two in and you have enough voltage to turn it on. So when the nodules on the seafloor are in contact with each other, they work in perfect harmony, like multiple batteries.

The researchers tested this theory in the lab, collecting and studying potato-sized metal nodules. They measured the voltage across the surface of each metal block—essentially the strength of an electric current. They found that it was roughly the same as the voltage of a typical AA battery.

This means, they say, that the nodules on the sea floor It can generate electrical currents large enough to split or electrolyze seawater molecules..

Researchers believe that the same process — producing oxygen with electrical power that requires no light or biological interventions — could occur on other planets and moons, creating oxygen-rich environments where life could thrive.

The Clarion-Clipperton Zone, where the discovery was made, is already being explored by several seabed mining companies that are developing technology to collect the nodules and bring them to a surface vessel.

The US National Oceanographic and Atmospheric Administration (NOAA) warned of this. Deep sea mining could ‘destroy life and habitats on the seabed’.

Similarly, more than 800 scientists from 44 countries have signed an agreement. Petition Highlighting the environmental risks of this practice and calling for it to stop.

It is common to discover new species in the depths of the ocean. It is often said that we know more about the moon than we do about the sea floor.

The new discovery suggests that the nodules themselves could provide the oxygen needed to support life in this region of the planet.

Professor Murray Roberts, a marine biologist at the University of Edinburgh, was one of the scientists who signed the petition.

“There is already overwhelming evidence that deep-sea nodule mining will destroy ecosystems we barely understand.“He told BBC News,” he said.

“Since these fields cover such large areas of our planet, it would be crazy to proceed with deep-sea mining knowing that they could be a major source of oxygen production.”

“I don’t see this study putting an end to mining,” Professor Sweetman added.

“(But) we need to investigate it in more detail and we need to use the information and data we collect in the future if we are going to go into the deep ocean.” Mining in the most environmentally friendly way possible.“

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