The ubiquity and high bioavailability of microplastics have an unknown risk on the marine environment.
Biomonitoring should be used to investigate biotic impacts of microplastic exposure. While many studies
have used mussels as indicators for marine microplastic pollution, a robust and clear justification for
their selection as indicator species is still lacking. Here, we review published literature from field investigations
and laboratory experiments on microplastics in mussels and critically discuss the suitability
and challenges of mussels as bioindicator for microplastic pollution. Mussels are suitable bioindicator for
microplastic pollution because of their wide distribution, vital ecological niches, susceptibility to
microplastic uptake and close connection with marine predators and human health. Field investigations
highlight a wide occurrence of microplastics in mussels from all over the world, yet their abundance
varies enormously. Problematically, these studies are not comparable due to the lack of a standardized
approach, as well as temporal and spatial variability. Interestingly, microplastic abundance in fieldcollected
mussels is closely related to human activity, and there is evidence for a positive and quantitative
correlation between microplastics in mussels and surrounding waters. Laboratory studies collectively
demonstrate that mussels may be good model organisms in revealing microplastic uptake,
accumulation and toxicity. Consequently, we propose the use of mussels as target species to monitor
microplastics and call for a uniform, efficient and economical approach that is suitable for a future largescale
monitoring program.