Abundance, Composition, and Potential Ecological Risks of Large Micro- and Mesoplastics in a Southern Italian Beach

This study provides a spatially resolved assessment of the abundance, composition, and ecological risk of large microplastics (LMPs, 1–5 mm) and mesoplastics (MSPs, 5–25 mm) in surface sediments at Lido Morelli Beach, southern Italy. Fifteen replicated sediment samples distributed across five shoreline-parallel transects were taken from the upper 5 cm of sediment within 0.25 m ² quadrats, covering approximately 800 m ² of beach surface. Plastic particles were visually sorted, size-classified, and chemically identified using ATR–FTIR spectroscopy. A total of 764 LMPs and 229 MSPs were collected, with maximum concentrations for both size classes occurring along storm berm transects. Polymer composition was dominated by polyethylene and polypropylene, and a strong positive correlation between LMP and MSP abundances ( R ²  = 0.86) indicated co-accumulation. Plastic pollution was assessed using four ecological indices. Pollution Load Index values >1 for both size classes and exceptionally high Pellet Pollution Index values suggest a probable pellet industrial source, while hazard-based indices (Hazard Index) indicated low polymer toxicity. The results provide actionable evidence for environmental regulators, port authorities, industrial pellet producers, and coastal management agencies, supporting targeted pellet-loss prevention, improved port and supply-chain controls, and monitoring strategies aligned with forthcoming EU regulations on the release of plastic pellets.