Quantifying microplastics in water and sediment along river-marsh transects in the Choptank River Estuarine, Coastal and Shelf Science

Microplastics (MPs, <5 mm) are pervasive contaminants in aquatic environments. This study quantified MP abundance, distribution, size, and morphology in water and sediment along river-marsh transects of the Choptank River, a major tributary of the Chesapeake Bay. We compare differences in microplastic concentrations due to locations of transects, positions across the river, and seasonality. We also examine patterns in particle sizes due to the potential importance of this characteristic for microplastic transport and fate. In the water column, abundance of microplastics was higher in the marshes flanking the river than the deeper channel at all transects and in all seasons. In the sediment, abundance is higher at subtidal than intertidal sites. Size distributions are comparable between the water and sediment, but show distinct patterns based on particle morphology. Our results agree with expectations based on what is understood about the trapping capacity of salt marsh vegetation and sedimentary depositional tendencies at subtidal sites, improving knowledge of microplastic transport and fate in an estuarine tributary by quantifying abundance and characterizing morphology based on size and shape. Grant no. NA21NOS9990112-T1-01