Manganese nodules in the sea: Serious mining in the deep sea

A treasure lies deep in the sea: manganese nodules. They are millions of years old and contain metals that are important for semiconductors, for example. Research is currently underway to determine how badly degrading the tubers would damage the ecosystem.

There is a box of manganese nodules on the desk of marine biologist Felix Janßen. But he is not rich now, says the scientist from Bremen, a tuber alone is only worth a cent. It just makes the crowd. Because: According to estimates, up to one trillion tons are stored in the oceans worldwide. There is great interest from industry. Germany has also secured a deep-sea license for the exploration of manganese nodule fields in the Pacific: in the “Clarion Clipperton Zone” west of Mexico.

Collector collects manganese nodules under supervision

So far, they have not been used economically. There is still no market-ready technology and dismantling is not permitted. But that could change soon. The International Seabed Authority (ISA) is currently developing guidelines according to which deep-sea mining would be possible – the so-called “Mining Code”.

A European team of scientists is also expected to provide recommendations for such environmental standards. Janßen is one of them. The research group of the “MiningImpact” project took part in a first industrial mining attempt in April and May. In the German and Belgian manganese nodules license area, a prototype of a so-called collector was launched into the water from a ship. The machine collected the black nodules up to a depth of 4500 meters.

Scientists observe process – protests from environmentalists

One ship away, the scientists observed the process. Their task was to find out what the degradation of the tubers means for the environment. Because there is a combination of effects, explains Janßen. The seabed is plowed through and the tubers are removed. In addition, there is a potential for an increase in the ecological footprint left behind – by the fact that the ocean floor, which has been set in motion, drifts and settles again somewhere.

A cloud of sediment under water, which Greenpeace also complains about. The environmentalists were also on site with the “Rainbow Warrior”. For them it is already clear: The mining of the manganese nodules threatens the ecosystem of the deep sea. To draw attention to this, they wrote the word “Risk” – English for “risk” – on the ship of the industrial company.

The consequences of manganese depletion will only be foreseeable in years

Earlier studies had already shown how sensitively the deep-sea fauna reacts to disturbances. “We found that 20 to 25 percent of the species disappear every time we remove the manganese nodules from the system,” explains Tanja Stratmann. For example, the tubers provide a breeding ground for various sponges. Stratmann works as a visiting scientist at the Max Planck Institute for Marine Microbiologists in Bremen and is also part of the “MiningImpact” research project.

The Bremen-based group specializes in bacterial communities that live in the seabed of the deep sea. On the expedition, they measured the oxygen content in the soil with sensors before and after the degradation test and took soil samples. Evaluating the data in the laboratory will take the next few years.

Manganese nodules are not a renewable raw material

Marine biologist Janßen and his colleagues want to be able to precisely assess the ecological consequences of deep-sea mining. One thing is clear to them: mining changes the living space. When the tubers are gone, they stay away. Because the tubers grow back very slowly: “They won’t come back as long as humanity exists, says Janßen.

Even a layperson can see a change after the collector test: video recordings from the sea floor show clear caterpillar tracks – the tubers are collected in a pile next to it. So is environmentally friendly deep-sea mining even possible? One thing is clear: an intervention in the living space leaves traces.