Spatial assessment of chemical contamination and marine litter for cetacean exposure risk in the Pelagos Sanctuary (North-Western Mediterranean Sea)

The Pelagos Sanctuary (north-western Mediterranean Sea) is a key cetacean conservation area, yet pollution stress there remains underestimated because data are fragmented across matrices and species. The present study developed a geographic information system (GIS)-based framework integrating anthropogenic contamination, including marine litter, and cetacean distributions, to identify areas and species with elevated exposure potential. A geodatabase comprising 23,474 quality-controlled records was compiled and assigned to a 10 × 10 km grid covering 1066 cells. Records covered 221 chemical analytes, 84 in water, 102 in sediment and 137 in biota, including trace metals, organochlorines, polychlorinated biphenyls, polycyclic aromatic hydrocarbons (PAHs), brominated flame retardants, per - and polyfluoroalkyl substances, phthalates and pharmaceuticals, and three categories of marine litter. Contamination status was assessed using an extended chemical status assessment tool (CHASE+) across water, sediment, biota and marine litter, and combined with modelled densities of seven resident cetacean species to compute chemical (REIc), marine-litter (REIml) and total (REIt) Risk Exposure Indices. Data covered 453 cells (42.5% of the Sanctuary), mostly coastal; organochlorines (27.1% of cells) and PAHs (22.4%) were the most widespread classes. Regulatory thresholds existed for 65%, 34% and 32% of compounds in water, sediment and biota respectively, versus 100% for litter, limiting assessment of emerging contaminants. Chemical status was predominantly non-problematic, whereas 85.4% of assessed cells showed bad or very bad litter status. Stenella coeruleoalba showed the highest cumulative exposure (REIt = 4.00), followed by Tursiops truncatus (1.72). This reproducible framework identifies priority areas, species and monitoring gaps, supporting targeted conservation and management.