A PRISMA-ScR-Guided Scoping Review of the Impacts of Metal Mining Waste Discharges on Coastal and Marine Environments

The discharge of metal-rich mining effluents and waste into marine environments represents a significant environmental challenge, with impacts extending from coastal to deep-sea ecosystems. This study presents a scoping review conducted in accordance with PRISMA-ScR guidelines to identify, classify, and synthesise evidence on the effects of large-scale mining waste disposal in coastal and marine settings. Searches of Web of Science, Scopus, and relevant grey literature sources yielded 147 eligible publications from an initial dataset of 563 records. The evidence reviewed enabled the identification of 81 distinct impacts systematically grouped into nine primary categories spanning physical, geotechnical, hydrodynamic, geochemical, biological, ecological, and socio-economic dimensions. Marine tailings deposits behave as dynamic systems that facilitate the transport of contaminants beyond disposal sites through processes such as plume dispersion, sediment resuspension, turbidity currents, and porewater exchange. Geochemical reactions and geotechnical failures can increase environmental vulnerability, a risk further exacerbated by ocean warming, acidification, and changing circulation patterns. Beyond highlighting the need for precautionary, integrated, and adaptive management approaches, this review provides the first comprehensive global inventory of impact categories and assessment factors associated with marine mining waste disposal, establishing a reference framework to guide future research, environmental management, regulatory evaluations, and industry decision-making.