Bioaccumulation, biomagnification and ecological risk evaluation of microplastics in Sanggou Bay, China

Microplastics (MPs), ubiquitous emerging pollutants in marine environments, pose potential ecological risks through trophic transfer. However, the influence of MP trait on their trophic transfer dynamics remains poorly characterized. This study investigated the bioaccumulation patterns, trophic transfer and ecological risks of MPs in Sanggou Bay. MPs were found in all examined organisms, with concentrations ranging from 0.095 ± 0.017 items/g in Hemicentrotus pulcherrimus to 0.506 ± 0.059 items/g in Charybdis japonica. The compositional profile (size, polymer type, shape, color) of MPs within organisms was similar to that of the surrounding water and sediment, indicating ambient exposure as the predominant source. Sediment-derived MPs contributed dominantly to bioaccumulation compared to those from the aqueous phase. Furthermore, a trophic magnification factor of 1.42 (r = 0.417, p < 0.01) revealed biomagnification across the food web, with enhanced transfer for specific MP traits: smaller sizes, fiber and film shapes, transparent particles, and polystyrene composition. The Pollution Load Index assessment revealed a low risk posed by MPs in surface water and sediments of Sanggou Bay. These findings provide novel insights into the bioaccumulation and biomagnification potential of MPs and demonstrate that MP physicochemical characteristics govern their trophic magnification.