Direct and indirect effects of microplastics on bivalves, with a focus on edible species: A mini-review

Bivalves play important roles in the ecosystem. However, bivalve populations have suffered a global decline in recent decades. This decline has caused public concern, because bivalves provide ecosystem services and are important sources of protein and ornaments (such as pearls) that support the fishing industry in coastal zones worldwide. Microplastics are an emerging global threat for bivalves and have been commonly detected in commercial edible bivalves, including mussels, oysters and clams. To comprehensively understand impacts of microplastics on bivalves, the potential exposure pathways by which microplastics affect bivalves are reviewed. The existing scientific evidence indicates that microplastics not only directly affect the physiology of bivalves, but also indirectly affect them by changing the structure of their sedimentary habitats, impairing their food resources and delivering persistent organic pollutants. In addition, the consumption of contaminated bivalves is a main pathway of exposure to microplastics by humans, which raises potential human health concerns. An evaluation of the hazards associated with the consumption of bivalves that contain microplastics and associated toxic chemicals is urgently needed. More studies related to the effects of microplastic fibers on bivalves should be conducted, because microplastic fibers comprise the largest proportion of microplastics in the environment and bivalves.