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Distribution patterns of microplastics in seawater and sediment, and their bioaccumulation by Manila clam (Ruditapes philippinarum) in the coastal regions of Qingdao, China

Marine Pollution Bulletin 2026
Yilei Yu, Ashraf Mehreen, Wenxian Jiang, Li Zhang, Xiaoshou Liu

Summary

Scientists found tiny plastic bits (microplastics) in seawater, sea-floor mud, and clams along the coast of Qingdao, China — with pollution levels rising in summer and near busy urban and tourist areas. The clams absorbed these plastic particles quickly but took much longer to clear them out, meaning the shellfish you eat could act as a storage site for microplastics before they end up on your plate. While this study doesn't prove health harm to humans, it's a reminder that the seafood we eat may carry more plastic than we'd like — something researchers say deserves more careful study.

Study Type Environmental

Microplastic pollution has become a growing concern in urban coastal ecosystems, where seawater, sediment, and benthic organisms may jointly reflect environmental contamination and biological exposure. This study investigated microplastics in seawater, sediment, and the clam Ruditapes philippinarum along the Qingdao coast, China. All samples contained microplastics, with mean abundances of 635.67 ± 247.94 items m in seawater, 262.74 ± 147.80 items kg DW in sediment, and 20.28 ± 15.72 items ind. in clams. Microplastic abundances showed clear spatial and seasonal variation, with relatively high levels in highly urbanized and recreational areas during summer and autumn. Fibres were the dominant shape across seawater, sediment, and clam samples, while polyethylene (PE), polypropylene (PP), and polyamide (PA) were the major polymers. Multivariate analyses indicated partial compositional overlap among seawater, sediment, and clam samples, supporting possible compartmental connectivity. Exposure experiments showed that R. philippinarum could ingest, retain, and depurate ingested microplastics, with rapid early accumulation and slower clearance under controlled high-exposure concentrations. Overall, this study provides regional evidence of microplastic contamination and bioaccumulation potential in an intensively used coastal ecosystem, highlights shellfish as important biological receptors of coastal microplastics, and supports cautious interpretation of ecological risks and transfer-related processes.

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