There are large quantities of manganese nollen on the sea floor of the deep sea. These spherical structures contain valuable mineral ores, which could be used, among other things, for smartphones and electric car batteries. But the environmental consequences of a mining may be serious. A study now shows that a potential deep -sea mining not only changes the mining areas itself, but also further away areas in which the whirled -up sediment layers deposit again. So far, what this means for the sensitive ecosystems of the deep sea can hardly be estimated.
Raw materials such as manganese, nickel, cobalt and rare earths are required for the production of smartphones, electric cars and Co. So far, these have often come from mines in Africa, where they are broken down under precarious environmental and working conditions. On the other hand, another huge occurrence is not yet developed: at the sea floor of the deep sea, in about 3500 to 6500 meters below the surface of the sea, there are so -called manganese nodules. They are a few millimeters to decimeters tall and have put together from various metals for millions of years that had previously been dissolved in sea water or were released during the decomposition of organic materials.
Coveted raw materials
“Due to their large occurrence and their considerable content of copper, nickel, cobalt and a number of rare removal, the tubers have been of commercial interest since the 1960s,” explains a team around Iason-Zois Gazis from the Geomar Helmholtz Center for Ocean Research in Kiel. The international marine flooring agency Isa is currently working on a rules that should determine whether and under what conditions the manganese nodes can be broken down. So far, however, it is largely unclear how a possible deep -sea mountain building would affect the sensitive ecosystems of the deep sea. Earlier studies have already indicated that corresponding interventions cause damage that still affect biodiversity and functionality of the ecosystem after decades.
One of the dangers that have so far been understood is the spread of sediment clouds, which are whirled up when the manganese nods are removed. In order to better understand how the sediment at the sea floor would behave in a possible deep-sea mountain building, Gazis and his team have scientifically accompanied a test mission of a tuber collector prototype. In April 2021, the Belgian company Global Sea Mineral Resources (GSR) tested a deep -sea vehicle for breaking down manganese noles. At a depth of 4,500 meters, the remote-controlled device reduced manganese bars on an area of 34,000 square meters during its 41-hour test operation.
Whirled sediment
With various sensors on the sea floor and diving robots, the research team recorded how the whirled sediment clouds spread and deposited again. “While most of the whirled sediments sink to the ground within a few hundred meters, we were able to demonstrate fine particles from a distance of up to 4.5 kilometers,” reports Gazis. Along steep sections of the sea floor, the sediment cloud moved up to 500 meters downwards. Their further spread was determined by the natural ocean current.
In the immediate vicinity of the dismantling area, the sediment concentrations were up to 10,000 times higher than natural, but fell back to normal values within 14 hours. The majority of the whirled particles concentrated within five meters above the sea floor and declined relatively quickly. In an area of several hundred meters around the mining area, a layer of newly deposited sediment was up to three centimeters thick. In the mining area itself, at least the top five centimeters of the sea floor were removed.
Tolerance thresholds unclear
Especially in the top layers of the sediment, the deep sea houses an enormous biodiversity, which according to previous knowledge is very sensitive to the smallest disorders. “The most difficult challenge is to determine quantitative tolerance threshold values in order to protect the broad spectrum of living things that live in the potentially living areas affected by the mining on the sea floor,” explains the research team. How much sediment can be whirled up? How thick can the newly deposited layers be in order to cause as little damage as possible? So far, these questions have not yet been clearly answered.
In the event that deep -sea mountain construction will be allowed in the future, Gazis and his team recommend equipping the corresponding deep -sea devices with advanced surveillance technology in order to capture the consequences in real time and to be able to react quickly if necessary. In addition, based on the current results, it could make sense to restrict the dismantling at the level, since thicker sediment layers with large height differences with large height differences that have more potentially serious effects.
Source: Iason-Zois Gazis (Geomar Helmholtz Center for Ocean Research, Kiel), Nature Communications, DOI: 10.1038/S41467-025-56311-0