Microlitter occurrence, distribution, and summertime transport trajectories in the coastal waters of the north-eastern Tyrrhenian Sea (Italy)

Coastal areas are extremely exposed to litter pollution. In this work, we assessed the abundance and distribution of microlitter in the water column and surface waters, as well as its summertime transport trajectories in the northern Latium coastal area (Tyrrhenian Sea, Italy). Microlitter items were classified according to their different shapes (fragments, films, and filaments), sizes, colours, and types by visual sorting and by optical microscopy; their composition was addressed via spectroscopic (Raman and FTIR) microanalysis. Microplastics (MPs) were abundant in all water samples; polypropylene, polyethylene, and poly-methyl methacrylate were identified. The results show a higher concentration of microlitter items in the water column (average concentration of 5.9 ± 1.38 items/m³) compared to surface waters (average concentration of 0.16 ± 0.03 items/m³). These abundances are similar to those found in the Mediterranean Sea and Oceanic waters. The sampling sites closer to the coast showed a higher abundance of particles, especially filaments, in the water column compared to the offshore areas. This feature can be explained based on the presence of land-based pollution sources, bathing areas, and the resuspension of microlitter items from the bottom. Analysis of the surficial trajectories pointed to a general northward transport direction of microlitter and the presence of possible enrichment spots along the coast.