Under the guidance of Dr Matthias Haeckel, coordinator of the project, a multidisciplinary team will investigate sites where nodule mining was tested five and a half years ago. The goal of the expedition is to assess the impacts on aquatic habitats and the seafloor. The results will directly feed into recommendations for international regulations on deep-sea mining currently being discussed at the International Seabed Authority.
Polymetallic nodules form at a snail’s pace. They grow about one to two millimetres over the course of a million years. If buried by sediment, they dissolve again. In their undisturbed state, they provide a habitat on the abyssal seafloor for animals that depend on a hard surface, which otherwise cannot be found there. “Typically, we find two to three small organisms on each nodule,” Matthias Haeckel explained.
Sea anemones, soft corals, or giant stalked sponges — which in turn provide a habitat for other organisms — are absent where the nodules have been removed. And because everything proceeds extremely slowly in the deep sea, Haeckel is confident: “Likely, we will not see any recovery.”
In spring 2021, the Belgian company Global Sea Mineral Resources (GSR) tested a pre-prototype nodule collector in the Clarion-Clipperton Zone (CCZ), at a depth of more than 4,000 metres. Over 74 hours of operation, the vehicle travelled about 32 kilometres and collected polymetallic nodules across 54,000 square metres of seabed, roughly equivalent to seven football pitches.
Scientists from the JPI Oceans MiningImpact2 project independently monitored the trials and their environmental impacts aboard Island Pride, a research vessel chartered by the German Federal Institute for Geosciences and Natural Resources (BGR). Five and a half years later, the current expedition aboard RV SONNE is returning to the test sites to assess how the affected ecosystems have changed, drawing on the observations collected during that earlier campaign.
In addition to the removal of the biota-rich layer of surface sediments, another effect is the sediment plume that is suspended in the bottom water and resettles again within a distance of several hundred metres around the mining site. Fauna that are attached to the nodules (sessile fauna) cannot escape it and gets buried. Haeckel: “Some organisms can clean themselves, others cannot. Those that filter their food from the water are also very likely to be affected.” Investigating these effects is challenging, just as research in the deep sea in general is by no means easy. “We are still far from having a complete knowledge of the abyssal ecosystem; for example, we do not know what role the individual species play,” said the scientist shortly before his sixth research expedition to polymetallic nodule fields. “We’re only just beginning to understand the deep sea.”
To gain as many insights as possible during the expedition, RV SONNE carries a multitude of marine research gear: the remotely operated vehicle (ROV) KIEL 6000, which alone is the size of a small van and requires five 20-foot containers for cables, winches, the control unit, and accessories. The autonomous underwater vehicle (AUV) ABYSS, with its launch and recovery system, three benthic landers that can be deployed at the seafloor, and sediment sampling devices such as multiple and box corers, carries a total of 16 containers of scientific equipment on board. And the expedition time will be utilised to the fullest: RV SONNE will not enter any port for 54 days, the maximum stay at sea for which the ship is designed.
In total, 39 researchers from 17 institutions and seven European countries are participating in the expedition, a multidisciplinary team drawing from the fields of biology, microbiology, chemistry, oceanography, and geology, each addressing a diverse range of research questions. In addition to investigating how faunal communities on the seafloor have changed five and a half years after the mining test and how long effects from the sediment plume persist, the scientists will also examine whether artificial hard substrates, as a substitute for mined polymetallic nodules, can promote recolonisation of the seabed.
Even if the above questions can be answered, the abyssal ecosystem remains largely understudied. Haeckel explained: “Many species in the CCZ are extremely rare; about ninety per cent of the species that we have sampled so far are still unidentified and have no name. And no one knows how many species are still to be discovered.” Another important topic about which little is known is species connectivity: “Many species are distributed across the entire CCZ between Mexico and Hawaii, in some cases even across the Pacific Ocean, which means gene exchange must be taking place. But we do not know what intermediate spatial steps and temporal scales are involved.” If this connectivity is to be disrupted by mining operations, the consequences for the deep-sea ecosystem will be immense.
“This kind of large-scale damage must be prohibited, because we would only notice it if it is already too late,” says Haeckel, adding, “The benthic ecosystem will not recover on human time scales. While the specific nodule habitat is removed permanently, sedimentary processes will be altered for thousands of years.”
Since 2015, JPI Oceans has funded three consecutive MiningImpact projects which have been assessing the environmental impacts of potential future deep-sea mining activities. MiningImpact3 is funded under the Joint Programming Initiative Healthy and Productive Seas and Oceans (JPI Oceans) by the Belgian Federal Science Policy Office (Belgium), the Department of Work, Economy, Science, Innovation and Social Economy (Government of Flanders, Belgium), the Federal Ministry of Education and Research (Germany), the Ministry of Universities and Research (Italy), the Dutch Research Council (the Netherlands), the Research Council of Norway (Norway), Narodowe Centrum Badań i Rozwoju (Poland), and the Department for Environment, Food and Rural Affairs (United Kingdom).
Disclaimer: all photos used in this article are credited to Tim Kalvelage.