Spatial and Temporal Deposition Rate of Beach Litter in Cadiz Bay (Southwest Spain)

This study explores the spatial and temporal distribution of beach litter accumulation rates at seven sites in Cadiz Bay, Southwest Spain, during October 2022 (i.e., autumn) and March 2023 (i.e., spring). Beach litter was collected during low tide conditions at the strandline during two series of 10 consecutive daily surveys. The main aim of this paper is to comprehensively analyze the influence of seasonality and hydrodynamic and wind patterns on litter abundance and composition. In October, 4199 items (22.58 kg) were recorded, increasing to 4634 items (22.68 kg) in March. Overall, the average litter abundance remained relatively consistent but notable variations were observed at different beach locations. Plastic litter was the most abundant in the total litter amount with 71.13% and 88.39% in October and March, respectively. Litter categories increased from 90 to 107 from October to March and the top 10 litter categories included cigarette butts (1746 in autumn and 514 in spring), plastic fragments (985 and 339) and plastic packaging (297 and 211). Statistical analyses showed no significant seasonal impact on litter quantities but confirmed seasonal variations in litter types. For instance, cigarette butts were more abundant in October, i.e., in autumn, as they are linked to the intensive use of beaches during the summer period (June–September), while wet wipes were prevalent in March, i.e., in spring, because they are associated with an increase in wastewater and river discharges recorded during the late autumn and winter months (November–February). No clear correlations were found between litter quantity and wave height, but specific patterns emerged at exposed and sheltered beaches. The findings provide valuable insights for optimizing coastal clean-up efforts with customized strategies. Further investigations are needed to fully understand the relationships between litter and environmental factors.