The Issues of Micro‐Nanoplastics in the Oyster and Mussel Aquaculture Sector

ABSTRACT Over 90% of plastic debris in marine environments consists of microplastics smaller than 5 mm. This is a growing global concern, especially given the emerging but largely unquantified presence of nanoplastics. This review synthesizes current knowledge on micro‐ and nanoplastic contamination in coastal areas and its effects on bivalve species, particularly oysters and mussels, whether in aquaculture or the wild. Drawing on 316 references, notably case studies of (micro)plastic waste contamination of surface waters, sediments, and animals in coastal areas, and experimental data on ingestion, fate, and impacts of micro‐nanoplastics on organisms. Microplastic levels range from a few particles per cubic meter of seawater (> 300 μm) to several hundred per kilogram of sediment. Between 60% and 93% of oysters and mussels are contaminated, with concentrations ranging from 0.2 to 2.9 particles per gram of tissue; over 80% of these particles are smaller than 50 μm. After ingestion, most microplastics are excreted, but smaller nanoplastics (< 100 nm) can cross biological membranes and reach internal organs. Even transient exposure in the digestive tract can impair energy uptake, immune function, and reproduction. Plastic additives can also cause endocrine‐like disruptions. Reducing plastic pollution in coastal environments requires coordinated action. Effective actions should include integrated and enforceable strategies, including international regulations on plastic additives, improved waste management, and the promotion of safer alternative materials.