A systematic monitoring approach to assess floating marine macro litter in Italian waters: Baseline, thresholds, good environmental status, and mitigation priorities under the EU MSFD.

The EU Marine Strategy Framework Directive (MSFD, 2008/56/EC) requires Member States to establish monitoring programs for Descriptor 10-Marine Litter, to track progress towards achieving a marine Good Environmental Status (GES). Italy conducted systematic monitoring of Floating Marine Macro Litter (FMML) in three Marine Reporting Units: Western, Central Mediterranean, and Adriatic (2018-2022, 534 surveys, 2719 km² across all seasons). This study assessed baseline values for FMML amount and composition, giving indication for tracking GES progress. Following the beach litter approach and considering the differences between coastal and offshore environment, two threshold values were identified: 14.4 items/km² (objects >2.5 cm) in coastal environments; 0.6 items/km² (objects>20 cm) in offshore. Based on mean density values (95.8 ± 6.4 items >2.5 cm/km² coastal; 20.7 ± 2 items >20 cm/km² coastal; 2.7 ± 0.18 items >20 cm/km² offshore), all sub-regions were found to be in non-GES status. Priority for mitigation measures and for the replication of the approach are given.