Haarboom pointed out that deep-sea mining can occur at depths where underwater life is not yet understood.
Of particular concern is the deep-sea bottom mud that is stirred up when collecting manganese nodules. Most of the life in the deep sea is unidentified, so when the water becomes murky, it has completely unknown effects.
For his research, Haarboom conducted experiments using various equipment to measure the amount and size of suspended particles in water. She used these instruments to take measurements on the ocean floor in the Clarion-Clipperton Zone, a vast region of the deep Pacific Ocean, before and after dragging a grid of 500 kilograms of steel chain to the ocean floor.
“The first thing that strikes you when you take measurements in the area is that the natural water is unimaginably clear,” the scientist said. “When we dragged the chain back and forth over 500 meters, the majority of the material that was hoisted up settled within just a few hundred meters. However, we also found that a small portion of the stirred up sediment left the test site. We found that we could still see hundreds of meters above the bottom, and far from the test site, the water was much murky.”
A follow-up study, in which Haarboom was not involved, found “dust clouds” up to 5 kilometers away from the test site.
Companies competing for concessions to mine metals from the deep ocean are looking to the results of these initial tests as evidence that deep-sea mining has a low impact on benthic organisms. But that's not justified, said Haarboom's study co-investigator Henko de Stigtel, an oceanographer at the Royal Netherlands Institute of Marine Research.
“Indeed, based on this PhD study and subsequent research, we know that most of the dust sinks quickly. “Considering our dependence on very scarce food, every last little bit can have a big impact,” he said.
Both Haarboom and De Stigter call for further research before making firm statements about the effects of deep-sea mining.
“It is too early to tell at this point how harmful or harmless the final dust particles that will travel this far will be,” De Stigter stressed.
