Microplastics are ingested by estuarine species, yet the trophic transfer of microplastics from common single-celled prey to larval predator has never been investigated in estuarine systems. Furthermore, the influence of microplastic-associated contaminants on trophic transfer in estuarine systems is unknown. This study provides the first evidence for the trophic transfer of microplastics in a model food chain relevant to North American estuaries, as well as the potential impacts of a sorbed legacy pollutant on microplastic trophic transfer. Our study is also the first to use a unicellular microzooplankton as prey in a microplastic trophic transfer study. Microzooplankton are key microbial consumers and play an important role in estuarine food webs. We also demonstrate the negative impacts of microplastic ingestion on growth in larval fish. AbstractMicroplastics are of increasing concern as they are readily ingested by aquatic organisms. This study investigated microplastic trophic transfer using larval inland silversides (Menidia beryllina) (5 d posthatch) and unicellular tintinnid (Favella spp.) as a model food chain relevant to North American estuaries. Low-density polyethylene microspheres (10-20 μm) were used to compare direct ingestion of microplastics by larval fish and trophic transfer via tintinnid prey. Dichlorodiphenyltrichloroethane (DDT)-treated microspheres were used to determine sorbed pollutant effects on microplastic ingestion. Larval fish exposed directly to microspheres