Plastic pollution on the Mediterranean coastline: Generating fit-for-purpose data to support decision-making via a participatory-science initiative.

Plastic pollution is a global problem and reliable, coherent and comparable data are essential for targeted mitigation strategies. Throughout the years Mediterranean NGOs have significantly contributed to providing data and information on the temporal and spatial distribution of marine litter found stranded on beaches; thus participatory-science campaigns are an essential tool to fill in the marine litter knowledge gaps. The present study reports the findings of beach litter surveys carried out by 7 NGOs in 23 sites along the coastline of the Mediterranean. The average litter density per site varied from 53 items/100 m to 6,660 items/100 m, with a median of 451 items/100 m. The majority of litter items were made of artificial/anthropogenic polymer materials accounting for 90% of all litter collected. Litter from shoreline sources accounted for 38%. Single-use plastics (SUPs) accounted for 38% of all items recorded ranging from 18.6% to 66.9% for the different beaches. 30% of the investigated beaches had more than 50% of SUPs of the total items recorded, thus providing baseline information and supporting evidence for the Single-Use Plastics Directive.