Ecotoxicological impacts of deep-sea mining - current scientific knowledge and necessary steps towards the definition of regulatory thresholds

The report aims at providing useful scientific information for the discussions at the International Seabed Authority for the development of binding environmental thresholds for deep seabed mining. It was initiated by an international workshop on the potential ecotoxicological impacts arising from future deep-sea mining activities, jointly organized by the Federal Institute for Geosciences and Natural Resources of Germany (BGR) and the JPI Oceans project "MiningImpact" in April 2023.

The report consists of three parts:

I.   A summary of the workshop objectives and results.

II.  An overview of the scientific background on the environmental impacts of deep-sea mining activities, the underlying biological mechanisms of toxic effects in deep-sea organisms, and the sources and routes of toxic exposure in deep-sea mining settings.

III. A review of thresholds in existing national and international regulatory frameworks for the protection of marine environments, and thresholds implemented in the environmental management of offshore activities (e.g. dredging, oil and gas exploration and production, submarine tailing disposal), including a discussion on their applicability to deep-sea mining, and the challenges to develop thresholds for the protection of deep-sea ecosystems.

The report contains two appendices. Appendix 1 includes a bibliography of relevant literature and links to national and international frameworks for the protection of marine environments (e.g. EU WFD, EU MSFD, OSPAR, HELCOM, Australia and New Zealand, United States, Canada, Norway), and for the environmental regulation of offshore activities, including guidance documents for threshold derivation and environmental management. Appendix 2 includes a compilation of existing threshold values for metals and metalloids in water, sediment and biota, and of threshold values operational in the environmental management of offshore activities. The accompanying Excel file provides extended versions of this compilation.