A Global Review of the Relationship Between Microplastic Ingestion and Trophic Level in Marine Fishes

Microplastics (MPs) are now ubiquitous in the marine environment, yet how they move through marine food webs remains unresolved. The accumulation, and even magnification, of MPs in marine food webs has been proposed, yet no study to date has provided a conclusive link between MP ingestion and trophic level. We review patterns in MP ingestion by fishes reported in the literature to determine how the number and rate of MP ingestion varies according to trophic level, body size, and region. Our findings indicate that the number of ingested MPs does not increase with trophic level, and that geographic region is the strongest predictor of MP ingestion. However, there are clear differences in methodologies used to find and identify MPs according to region, with studies using more rigorous procedures (e.g. tissue digestion prior to particle identification), that allow for the characterization of smaller particles, reporting higher concentrations of MPs. The current literature suggests that lower trophic level fish in more highly contaminated parts of the world may experience higher levels of MP ingestion, but future studies will require standardized methodologies to allow for adequate comparisons. The implications for marine food web ecology will vary depending on the ecotoxicology of current and future microplastic levels in the environment.