A comparative study of microplastic contamination and ecological risk in beach and bottom sediments along the southern Black Sea coast

Official URL: https://dx.doi.org/10.1016/j.rsma.2026.104766

Microplastics (MPs) are now recognized as widespread pollutants in marine ecosystems, with semi-enclosed seas such as the Black Sea particularly vulnerable due to restricted water exchange and extensive land-based inputs. This study presents the first comparative assessment of MP contamination and ecological risk between beach and bottom sediments along the entire Black Sea coast of Türkiye, which comprises the basin’s longest national shoreline. A survey was conducted at 64 sites (38 beaches and 26 bottom-sediment sites). Mean concentrations were broadly comparable across matrices, averaging 140.39 ± 10.38 MP/kg in beach sediments and 106.19 ± 8.74 MP/kg in bottom sediments, though site-specific hotspots exceeded 200 MP/kg for both matrices. Fibers were the dominant morphology in both matrices, with a significantly higher proportion on beaches (74.1 %) than in bottom sediments (53.5 %), while fragments and films were relatively more abundant in bottom sediments. Blue and black particles were common in both environments. Polymer analysis revealed a strong dominance of polyethylene terephthalate (PET) in beach sediments (59.1 %). In contrast, seabed sediments displayed greater heterogeneity, with substantial polymer types of polyethylene (PE), polypropylene (PP), polyamide (PA), and polyacrylonitrile (PAN). Multivariate analyses confirmed statistically significant compositional differences between matrices, with PET identified as the primary driver of dissimilarity. The Polymer Hazard Index (PHI) indicated severe ecological risks, with over 70 % of sites in both matrices classified in the highest hazard category (Class V), underscoring the persistence of hazardous polymers and their potential bioavailability.