Flood-driven microplastics pollution and its ecotoxicological footprint in shallow marine habitats

Microplastics (MPs) contamination of aquatic organisms is on the rise globally. The effect of extreme hydrologic events on the movement MPs and ecological hazards is poorly understood. Riverine transportation routes connect the plastic inputs on land to the shallow marine ecosystems, which contribute to the high biodiversity and the essential ecosystem processes. This review provides global evidence on flood-driven microplastic inputs into shallow coastal waters, with particular emphasis on river-dominated coastal regions and flood-prone environments. Evidence suggests that severe precipitation and flooding events rapidly mobilise the plastically built-up stores in the soils, sediments, and urban landscapes, resulting in concentrated but brief microplastic pulses that increase background levels of contamination in coastal waters over time. In order to sufficiently assess and control MPs pollution in coastal ecosystems with high risks of floods, the present review shows that extreme-event dynamics should be included in the monitoring procedures and ecological risk assessment.