Species-specific bioindicators of microplastic pollution in a shallow lake: Hydrological period drives benthic macroinvertebrate exposure in Baiyangdian Lake, China

The search for effective bioindicators is crucial for monitoring the pervasive contamination of microplastics (MPs) in freshwater ecosystems, particularly in shallow lakes that act as sinks and sources. We sampled three dominant benthic species with distinct feeding guilds and their ambient media (water, interface, sediment) across two hydrological periods and four functional zones. MPs were extracted via density separation after oxidative digestion, and identified using stereomicroscopy and FTIR. Our results revealed a pronounced species-specificity in MPs bioaccumulation, driven by feeding ecology rather than merely ambient MP levels. The hydrological period (wet vs. dry) was a stronger driver than spatial heterogeneity, enhancing MPs uptake in the gastropod Cipangopaludina chinensis and the shrimp Macrobrachium nipponense, but not in the crayfish Procambarus clarkii. Critically, correlations between MP abundance in environmental media and biota were consistently weak, underscoring the paramount importance of biological filtering processes. We propose a tripartite mechanism of "spatiotemporal driver-biological selection-interface interaction" and recommend Macrobrachium nipponense and Procambarus clarkii as sensitive bioindicators for MPs in sediments and the water column, respectively.