Fusion of microplastics into the mussel byssus.

Microplastics have been found to adhere to the surface of specific tissues or organs other than being ingested by the organisms. To further test the hypothesis that microplastics might get into specific body parts of organisms, mussel byssus was chosen as a target subject in the present study. In the field investigation, microplastics were found in mussel byssus, and the abundance of microplastics was 0.85-1.02 items/individual mussel and 3.69-9.16 items/g byssus, but the location of microplastics in byssus was not easily determined. Therefore, we simulated environmental conditions in the laboratory for mussels to form fresh byssus in the presence of microplastics. Three types of man-made microplastics (Polystyrene beads, Polyamide fragments, and Polyester fibers) were found in newly formed byssus of mussels after exposure to these test materials. We observed that microplastics not only adhered to the surface but also fused into the byssus of mussels. Since byssus is important for the well-being of mussels, the incorporation of microplastics into the byssus might impair the function of byssus. To the authors' best knowledge, this is the first study to show that microplastics can contact and fuse with the byssus of mussels during their formation, suggesting possible alternations for mussels to grip and interact with microplastics in the aquatic environments.