A revolutionary discovery

Biochemist Andrew Sweetman from the Scottish Association for Marine Sciences (SAMS) and his colleagues made a surprising discovery while measuring oxygen levels on the ocean floor to assess the impact of deep-sea mining. They found discrepancies between expected and actual readings.

But in the darkness of the ocean floor, oxygen formation processes do not occur everywhere. This particular case was discovered at a depth of almost 4,000 meters. For comparison, we can say that the Titanic was 3,810 meters deep. Scientists were surprised to see that oxygen concentrations increased instead of decreasing as expected.

When we first got the data, we thought the sensors were faulty because all the deep-sea studies so far showed that oxygen was being consumed, not produced. We went home and recalibrated the sensors, but for 10 years these strange oxygen readings kept coming up.
– explains Sweetman.

Later, scientists turned to the backup method, but this also yielded a similar result. “We realized that we had encountered something revolutionary and unpredictable,” the scientist adds. To investigate this mystery, the researchers collected some nodules (mineral formations that are often spherical or nearly spherical) to see if they could be the source of oxygen production.

The placers of these concretions cover huge areas at the bottom of the oceans and seas. These are natural deposits of rare earth metals such as cobalt, manganese, and nickel mixed in a polymetallic mixture.We use these metals in the batteries of our technologies, but it turns out that the natural combination of these rocks in polymetallic concretes produces voltages up to 0.95 Volts. When grouped like batteries, they can easily reach the 1.5 Volts needed. separation of oxygen from water in an electrolysis reaction.

It looks like we’ve discovered a natural “geobarium.” These geopiles provide the basis for a possible explanation of dark oxygen production in the ocean.
– says Northwestern University chemist Franz Geiger.

Additional evidence

Although much remains to be discovered, such as the extent of oxygen production by polymetallic nodules, the discovery offers a possible explanation for the continued persistence of “dead zones” in the ocean decades after bottom mining has ceased. In 2016 and 2017, marine biologists visited areas where resource extraction had taken place in the 1980s. Even the bacteria didn’t recover; there was no oxygen for themInstead, marine life evolved in similar deep areas.

It is still unknown why such dead zones have persisted for decades, but it can now be assumed that the cause is human extraction of oxygen-producing polymetallic nodules that help sustain life on the seabed.

Scientists also say that ocean-floor fauna diversity is higher in nodule-rich areas than in more diverse rainforests, raising questions about the feasibility of a strategy for developing the seabed and extracting resources. We could literally turn the ocean into a giant dead zonewhere nothing can survive. The formation of new nodules probably requires very long periods of time for the metals to sink to the bottom, clump together, and form nodules large enough to generate sufficient voltage for electrolysis.

The emergence of life

In addition to these huge implications for deep-sea mining, “dark oxygen” also raises a host of new questions about the origins of oxygen-breathing life on Earth.

Ancient cyanobacteria were long believed to be the first bacteria to provide the oxygen needed for the evolution of complex life billions of years ago. But we now know that oxygen was literally produced at the seabed. It’s too early to say whether these processes began before cyanobacteria emerged, and whether “dark oxygen” played any role. But it’s an important clue for further research. “We now know that oxygen was produced deep in the sea, where there was no light,” Sweetman concludes. “So we need to go back to the question of where aerobic life might have started.”