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Fragmentation of expanded polystyrene to microplastics by wharf roach Ligia spp.

Marine Pollution Bulletin 2025 4 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Seokhyun Lee, Yukinari Tsuruda, Masato Honda, Koki Mukai, Tomohiro Hirasawa, Daniel Christian Wijaya, Yuki Takai, Yohei Simasaki, Yuji Oshima

Summary

Researchers discovered that wharf roaches, common coastal crustaceans found throughout the Pacific region, actively graze on expanded polystyrene and fragment it into microplastics as small as 2 micrometers. In field surveys along Japanese coastlines, these animals were found to ingest polystyrene more frequently than other types of plastic. The study reveals a previously unrecognized biological pathway by which large plastic debris gets broken down into microplastics in coastal environments.

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.

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