New oxygen source in the deep sea surprises experts
In the examination of the seabed in the Pacific Ocean, researchers are hardly believing their eyes: They discover a previously unknown oxygen source at a depth of 4000 meters. This spectacular find could turn previous assumptions about deep-sea conditions completely upside down.
The main text of the study is only two pages long - but it contradicts a long-standing assumption. It could also shed new light on deep-sea mining, which is gradually approaching feasibility: On the floor of the Pacific Ocean, an international research team with German participation has discovered an previously unknown oxygen source in approximately 4000 meters depth.
"That's a sensational observation," says deep-sea researcher Felix Janßen from the Alfred-Wegener-Institut (AWI), who was not involved in the study published in the journal "Nature Geoscience". "That would turn everything on its head that we have assumed until now."
In the study, the research team led by Andrew Sweetman from the Scottish Association for Marine Science (SAMS) investigated the potential impacts of deep-sea mining and conducted measurements in the so-called Clarion-Clipperton Zone (CCZ). This area, which stretches over several thousand kilometers along the 10th degree of northern latitude, contains valuable resources - among them nickel, cobalt, lithium, and copper. Such valuable resources are used for the production of batteries and cell phones, for example. Particularly well-known are manganese nodules, which grow in large quantities and lie on the muddy seabed like potatoes.
Astonishment over unusual oxygen values
There, the research team found in small chambers that had been lowered to the seabed, unusual oxygen values. The concentrations were usually around 180 micromoles (μmol) per liter of water, but they rose to up to 800 micromoles in the measurement chambers.
This initially caused great astonishment. "When we received these data, we initially thought the sensors were faulty," explains Sweetman. "Every study in the deep sea had shown that oxygen is consumed there, not produced. We recalibrated the sensors, but the strange oxygen values persisted over ten years."
When other methods confirmed the surprising results, the team brought in chemist Franz Geiger from Northwestern University in the US state of Illinois. The native Berliner had reported in the journal "PNAS" in 2019 that rust in combination with seawater can generate electricity. A similar process, so the assumption, could be involved in oxygen production.
"Geobatteries" in the deep sea
It was known that a voltage of 1.5 volts is sufficient for the so-called seawater electrolysis - that is, the splitting of water into hydrogen and oxygen. In Geiger's laboratory, the team now examined manganese nodules collected from the seabed. In combination with seawater, they measured individual nodules to have a voltage of up to 0.95 volts. And several nodules together could generate more voltage than required for electrolysis. "It seems we have discovered a natural 'geobattery'", says Geiger.
Author Sebastian Fuchs from the Federal Institute for Geosciences and Natural Resources (BGR) in Hannover states, "The measurements are very sensitive", regarding co-author statements. Various methods were used, and oxygen production was detected both on the seabed and in the lab. However, questions remain: For instance, the settling and lifting of instruments on the seabed could have influenced the results - in addition, the oxygen amount remained constant after an initial significant increase. "We don't yet know the exact extent or duration of the oxygen production", Fuchs states, emphasizing the need for further research.
AWI expert Janssen also emphasizes, "We should not jump to conclusions about the measured amount. First, it needs to be shown if and where this new process plays a role." It could also be about local phenomena.
Controversial Deep-Sea Mining
Nevertheless, the question arises, what does this knowledge mean for deep-sea mining? As the complex and highly controversial commercial extraction of mineral resources from the deep sea gradually takes shape, several countries are becoming increasingly active. In January, the Norwegian parliament gave the green light for exploration and mining of minerals on the seabed in an arctic area on the Norwegian continental shelf. And the Pacific island state of Nauru had already announced plans to mine manganese nodules with the Canadian company The Metals Company (TMC) on the seabed.
BGR expert Fuchs assumes that deep-sea mining is not imminent but that countries like China and the Pacific island state of Nauru are very active: "Deep-sea mining is coming. We live in a resource-hungry society."
Environmentalists Fear Unforeseen Consequences
Critics and environmentalists have been warning for a long time that commercial mining of resources carries unforeseeable risks for the ecosystems there, which have been largely undisturbed for eons. Manganese nodules, for example, require several million years for only a few millimeters of growth. Their surface provides a firm substrate for organisms like mats of mussels in the sludge of the seabed, allowing them to settle. Deep-sea corals or worms that build calcareous tubes also grow on the nodules. Between them, sea cucumbers, deep-sea crabs, and up to 45 centimeters long giant isopods (Bathynomus) live.
A research team estimated in a 2023 publication in the journal "Current Biology" that there are 5580 species in the Clarion-Clipperton Zone - 90% of which are still undescribed.
The German "Disturbance and Recolonization" (Discol) project in the Peru Basin in the Pacific Ocean showed how sensitive this system reacts. Researchers plowed a square kilometer area experimentally in about 4100 meters depth in 1989 - as is common in the harvesting of nodules. Even 26 years later, the traces of the plow were still visible on the seabed. Analyses showed that the bacterial activity there had not yet recovered.
The International Seabed Authority (ISA; International Seabed Authority) in Kingston, Jamaica, plans to develop binding regulations for this mining by 2025, together with government representatives, researchers, and non-governmental organizations. "It's all about every word," Fuchs says.
The warnings from environmental groups could gain a new dimension with the current study: "Several large mining companies intend to extract valuable elements from the seabed at a depth of 3000 to 6000 meters," says chemist Geiger. "We need to think about how to mine these materials without decimating the oxygen source for deep-sea life."
For AWI researcher Janssen, the greatest concern remains how deep-sea mining will affect the ecosystems and biodiversity in the affected areas. "One can see that mining will fundamentally change the living conditions of deep-sea communities."
The expert does not believe that the newly discovered mechanism - however revolutionary it may be - will fundamentally change the oxygen budget in the deep sea. "But this is an example of how much we still don't know about this ecosystem. Therefore, we should be cautious."
The discovery of this oxygen source in the Pacific Ocean could significantly impact environmental protection and Species Protection efforts in deep-sea mining areas. This unexpected oxygen production mechanism, potentially linked to 'geobatteries' in manganese nodules, highlights the importance of Marine research and Education in understanding the deep sea. (Environmental protection, Species Protection, Marine research, Education)
In light of the newly discovered oxygen source, there's a need for reevaluating deep-sea mining strategies. Researchers must consider the impact of mining operations on this natural 'geobattery' and its role in supporting deep-sea biodiversity. (Environmental protection, Species Protection, Deep-sea mining, Marine research)
