Metal contamination in the coastal zone of Go<spacing diaeresis>kova Gulf including special environmental protection area (Western Turkiye): Sediment quality indices and environmental implications

This study presents a comprehensive assessment of sediment quality and ecological risk in the Gokova Gulf (Aegean Sea), a designated Special Environmental Protection Area (SEPA). Surface sediments from 73 stations were analyzed for grain size, organic carbon, calcium carbonate and 26 elemental concentrations. Enrichment factor (EF), geoaccumulation index (Igeo), pollution indices, and sediment quality guidelines (SQGs) were applied to evaluate contamination levels. Chromium (Cr), nickel (Ni), and arsenic (As) exceeded background values in many stations, with Cr and Ni surpassing probable effect levels (PEL) in 63 % and 95 % of samples, respectively. Spatial analysis revealed contamination hotspots in the southern and eastern sectors, linked to maritime traffic, wastewater discharge, and lithogenic inputs from peridotite-rich zones. Multivariate analyses (PCA, HCA) confirmed mixed geogenic and anthropogenic origins. The toxic risk index (TRI) highlighted considerable ecological threats, particularly from Ni and Cr, necessitating urgent mitigation strategies. These findings offer a robust scientific basis for sediment monitoring and coastal zone management in vulnerable semienclosed marine ecosystems.