Figure 1

Locations of shoreline (yellow circles) and subaqueous sediment grab (orange squares) sampling sites in Narragansett Bay (a). Each shoreline site included 2–3 transects within which the upper beach, mid-beach, intertidal zone, and subaqueous zone were sampled. At each sampling location, 94–100% of all plastic measured were microplastics (< 5 mm). Plastic concentrations (particles/kg dry sediment) range from about 400 to over 13,000 particles/kg dry sediment (b). Macroplastics dominate by mass (g plastic/kg dry sediment) and the ratio of macroplastic to microplastic shows that macroplastic mass is greater in the upper bay and decreases near the lower estuary (c). Satellite image derived from Google Earth v7.3.6.9345 (December 14, 2015; https://earth.google.com/)) and edited using a grid from Global Multi-Resolution Topography Synthesis (GMRT)⁷⁰.