Evaluation of the environmental consequences of polymetallic nodule mining based on the results of the TUSCH Research Association

Abstract

Abstract Realising a need for increased general knowledge of the deep sea for environmental impact assessments related to the permanent storage of waste products and mining of metal resources, the German Bundesministerium fur Bildung und Forschung has funded targeted research in the deep sea for more than 10 years. The research was carried out in an area in the Southeast Pacific Ocean close to and within a German mining claim, to match the interests of German deep-sea polymetallic nodule mining enterprises and the developing mining code of the Preparatory Commission for the International Seabed Authority and the International Tribunal for the Law of the Sea. The “TUSCH (abbreviation for ‘Tiefsee-Umweltschutz’—deep-sea environmental protection) Research Association”, with members from various university and governmental institutions, was part of the ATESEPP (Effects of Technical Interventions into the Ecosystem of the Deep Sea in the Southeast Pacific Ocean) Project between 1996 and 1998. Geotechnical, sedimentological, geochemical, hydrographic, numerical modelling and ecological studies relevant to environmental impact assessment studies of polymetallic nodule mining were undertaken. Since general oceanographic knowledge of the deep sea is rather limited, these various projects also have increased our general understanding of this region. This paper describes the potential impacts of mining processes on the seafloor and the near-bottom water layer as well as on bathyal and abyssal pelagic zones that will receive processed water, sediment and abraded nodule fines (tailings) discharged after nodule transport to the mining vessel at the ocean surface. The TUSCH Research Association defined various recommendations to keep the unavoidable impacts to a minimum, such as • limited penetration of the mining system into the sediment, • confining intensive resedimentation to the area behind the miner, • minimising transport of sediment to the ocean surface, and • discharging all tailings at great depths, ideally close to the seafloor. The recommendations are not new, but the present studies have improved them from precautionary to scientifically based statements.