As the search for important metals on land is becoming increasingly difficult, the focus has shifted to the oceans. Deep-sea excavation will be extremely expensive, but deposits around old volcanic vents are often enriched, with excavation companies looking for technologies to make it happen. Unfortunately, it is also disruptive to sea-bed ecosystems and new research suggests the damage is permanent. Researchers tested the effects of deep-sea excavation in the Peru Basin with a patch plow 4,000 meters (2.5 miles) below sea level, returning three times to observe progress, In 1989. The selected area is exactly where mining could one day take place, a patch of marine crusts covered in manganese nodules involving other, more precious metals.
Decades later, Max Planck Institute for Marine Microbiology student Tobias Vonnahme was part of a team that returned to the site to see if it was actually a reality. Vonnahme said in a statement, “Even after 26 years of this turmoil, plow tracks along the seashore were still clearly visible.” “And the bacterial inhabitants were also clearly affected.”
Bacteria from unchanged regions were about two-thirds on the oldest tracks and only half on the more recent ones. Since bacteria are the basis of the deep-sea food chain, their absence spreads through everything. Vonnahme said, “Our calculations show that it takes at least 50 years for germs to fully resume their normal activity.”
Near the surface, currents will remove visible damage and allow the rapid pace of life to restore ecosystems, but these forces remain at a slower pace in a stable energy-poor deep sea. The top layer of silt around the nodules does most of the work of processing the organic matter which settles to the seafloor but it is very fragile to survive the disturbance. The findings are known in Science Advances.
Senior author Professor Antje Boetius of the Alfred Wegener Institute said, “So far, only a handful of studies have dealt with the disruption of deep-sea biogeochemical due to mining.” Instead, the focus has been on the effects on animals.
Boetius believes the study will help improve environmental standards for deep-sea excavation, adding that “environmentally sustainable technologies must avoid the removal of dense and bio-efficient surface layers of the ocean.” Whether this will be possible, however, is still to be seen. Areas affected by any large-scale mining will be hundreds or thousands of times larger than those affected by the trial. On the other hand, these marine spaces are rich in cobalt among other metals that have proven particularly difficult to penetrate into land in an ethical and sustainable manner.