Uncovering the relationship between floating marine litter and human activities in watersheds

Rivers serve as the primary pathway for transporting floating marine litter (FML) from land to sea. However, the complex dynamics of transboundary rivers pose a significant obstacle when examining the impact of watershed-based human activities on FML distribution. This study conducts year-long monthly monitoring of FML using trawl and visual surveys in the coastal water of a peninsula dominated by indigenous rivers in south China. Overall, small pieces debris dominates FML in the nearshore waters of the peninsula, with meso-sized (0.5 cm-2.5 cm) FML accounting for 73.93 % of the total. The density of FML is more profoundly influenced by human activities within watersheds rather than its composition. Moreover, the association between human activity and FML density exhibits greater significant compared to variations based on geography and seasonality. This study provides a scientific basis for coastal protection and contributes for understanding of the mechanisms of marine litter transfer from land to sea.