Amount, composition, and spatial distribution of floating macro litter along fixed trans-border transects in the Mediterranean basin

Abstract Marine litteris a major source of pollution in the Mediterranean basin, but despite legislative requirements, scant information is available for the ongoing assessment of this threat. Using higher size classes as proxy for litterdistribution, this study gave a synoptic estimation of the amount, composition, and distribution of floating macro- litterin the Mediterranean. The average amount of macro- litterwas in a range of 2–5 items/km 2 , with the highest in the Adriatic basin. Seasonal patterns were present in almost all study areas and were significant in the Ligurian Sea, Sardinian-Balearic basin, and Central Tyrrhenian Sea. Plastic accounted for > 80% of litterin all areas and seasons, with the highest proportion in the Adriatic Sea, Ligurian Sea, and Sicilian-Sardinian Channels; in the Bonifacio Strait, Tyrrhenian Sea, and Sardinian-Balearic basin, littercomposition was instead more diverse. Spatial analysissuggested an almost homogeneous distributionof litterwithout evident regular aggregation zones.