Environmental impact of shipwrecks used as artificial reefs: a case study from Karaburun, İzmir, the Aegean Sea.

Artificial wrecks (AWs), which are intentionally submerged structures to promote marine biodiversity and support recreational diving, have gained increasing prominence on a global scale. Nevertheless, concerns regarding their environmental safety persist, especially in regions where regulatory oversight is limited. This study examines the ecological and human health risks posed by two artificial wrecks ("Alaybey" and "9 Eylül") deployed in the Karaburun Peninsula, Northeast Mediterranean, Türkiye, compared to a no-wreck site (Aslan Kayası). Despite rigorous pre-sinking protocols to remove fuels and oils, critical pollutants-such as antifouling paint residues containing Cu, Zn, Pb, and PCBs-persist due to incomplete cleaning. Over two years, seasonal sampling of sediments, mussels (Mytilus galloprovincialis), and fish (Diplodus vulgaris) revealed alarming trends. Sediments near AWs showed enrichment of Pb (EF: 37.2-92.1) and Cd (EF: 9.3-16.0) from significant to extremely high enrichment. The Potential Ecological Risk Index (PERI) reached > 1,000 at the "9 Eylül" wreck, classifying it as "extremely high risk." Mussels on AWs bioaccumulated Cd and Pb above EU safety thresholds, while fish on AWs exhibited Pb levels of 236-340 fold over limits. Notably, Hg contamination in fish samples obtained from the no-wreck site (1.2 mg kg-1) was traced to historic mining activities, underscoring region-wide pollution. These findings challenge the assumption that "cleaned" AWs are environmentally benign and highlight systemic gaps in pollutant mitigation, particularly for toxic coatings. The study advocates for stringent pre-deployment protocols, including paint stripping and PCB screening, to align AWs projects with global sustainability goals.