Marine litter on the Turkish Black Sea shoreline: Abundance, composition, and sources.

Marine litter (ML) is a growing environmental concern worldwide, particularly in semi-enclosed basins such as the Black Sea, where limited water exchange and high anthropogenic pressure exacerbate pollution risks. This study presents the first large-scale, standardized assessment of marine litter along the Turkish Black Sea coastline, based on surveys conducted at 37 stations spanning diverse coastal settings. A total of 29,610 litter items were recorded, with an average density of 0.80 ± 0.07 items/m2, and plastics accounted for 88.2 % of all collected items. The most frequently encountered items were single-use plastics, including cigarette butts, food wrappers, and bottle caps. According to the Clean Coast Index (CCI), the majority of beaches ranged from "moderate" to "very dirty," with the highest pollution levels observed in the eastern part of the coastline. The Plastic Abundance Index (PAI) further classified beaches as having "moderate" to "very high" plastic pollution. Additionally, the Hazardous Item Index (HII) revealed considerable spatial variation, with some sites showing high concentrations of potentially dangerous litter such as syringes, broken glass, and sharp metal objects. While some spatial variability was noted among stations, statistical analyses indicated no significant differences in overall litter density or composition across the six defined basins. These findings highlight the pervasive and hazardous nature of plastic pollution in the region and emphasize the need for basin-wide monitoring programs, harmonized methodologies, and integrated waste management strategies.