Spatiotemporal Dynamics, Seasonal Aggregation, and Policy Interventions of Marine Microplastics

The spatiotemporal dynamics of marine microplastics remain obscure and pose significant challenges for global marine protection. To address this knowledge gap, we compiled a global data set of marine surface microplastic observations (0-5 m, 1998-2023) and employed data-driven models coupled with statistical methods to quantify the spatiotemporal dynamics and driving mechanisms of marine microplastics. The total quantity of marine surface microplastics (primarily 0.33-5 mm) is approximately 3.29 × 1014 items, which represents an update to previous estimates. Microplastic concentrations significantly increased in 72.59% of global marine areas, with an annual growth rate of 4.53%. Ocean dynamics under thermohaline regulation facilitates microplastic transport and seasonal accumulation, a process that may be intensified by climate warming. Total microplastic loads in the Northern Hemisphere are 18.31% (95% confidence interval: 13.75%-27.57%) greater during summer than in winter, highlighting seasonal exposure variations for marine ecosystems. Notably, targeted policy interventions resulted in an 82.54% reduction in potential loading in the Baltic Sea. The unique spatiotemporal dynamics of marine microplastics revealed in this study provide key insights for microplastic risk assessment and control.