Fragmentation of expanded polystyrene to microplastics by wharf roach Ligia spp

The East Asian region is an area of high human and fishery activity, where a substantial amount of plastic, especially expanded polystyrene (EPS), is discharged into the environment and reaches sandy and rocky seashores. EPS pollution and its impact on organisms inhabiting sandy and rocky areas may be suspected. In a field study conducted in the West Japan sandy and rocky seashore region, wharf roaches, Ligia spp., which are ubiquitous and cosmopolitan organisms in the Pacific area, were found to ingest EPS more frequently than polypropylene and polyethylene microplastics. Furthermore, the results of our feeding experiment indicate that wharf roaches are capable of not only grazing on EPS, but also fragmenting EPS to microplastics ranging from 2 to 214 μm in diameter when estimated as circles. We conclude that wharf roaches may contribute to the decomposition and fragmentation of EPS microplastics.