Microplastics in gastropod molluscs: a review of contamination trends in global studies

Microplastics (MPs) have become a global concern due to their persistence in the environment and their harmful effects on ecosystems, infrastructure, society, and the economy, warranting immediate attention and action. Ecotoxicological impacts of MPs are significant, as they tend to infiltrate food chains, facilitating the trophic transfer of MPs and associated contaminants, and potentially endangering human health. The isolation and characterisation of MPs can be improved, enabling science to elucidate their fate in organisms. Molluscs are among the major groups affected by MP contamination, which can serve as vectors for the biomagnification of pollutants within aquatic food webs. This review demonstrates the global distribution, types, and chemical nature of MP contamination in molluscs. It summarises the different types of MPs reported from various molluscan species and compiles a detailed review table based on existing studies. Current research indicates that gastropods inhabiting diverse aquatic ecosystems, including freshwater, mangrove, marine, coastal, estuarine, brackish water, and semi-enclosed marine environments, are under threat of MP contamination. Studies also show that mangrove ecosystems appear to be the most heavily affected, with gastropods showing a high number of MP particles per individual. Fibres and fragments are the most commonly detected forms of MPs in gastropods, and smaller particles are more frequently ingested due to their size. A trend was observed in both MP contamination level and MP abundance, with larger gastropod species exhibiting higher MP loads than smaller species. The widespread presence of MPs in gastropod molluscs raises serious ecological concerns and highlights potential risks of human exposure through trophic transfer in the food chain. Hence, this review helps clarify contamination levels and highlights the importance of further research and management to control MP pollution.