The uptake of microfibers by freshwater Asian clams (Corbicula fluminea) varies based upon physicochemical properties

Microplastic is an umbrella term that covers particles with various physical and chemical properties. However, microplastics with a consistent shape, polymer type and size are generally used in exposure studies (e.g., spherical polyethylene or polystyrene beads 1–100 μm in size). In the present study, we exposed freshwater Asian clams (Corbicula fluminea) to microfibers with different physicochemical properties at concentrations of 100 and 1000 fibers/L. The first experiment in this study exposed clams to microfibers made from six different polymers, demonstrating that Asian clams uptake more polyester (PET) (4.1 items/g) relevant to other polymers. The next experiment exposed clams to PET fibers of different size classes, demonstrating that uptake in the size range 100–250 μm (1.7 items/g) was greater than other size classes. These results suggest that physicochemical properties such as polymer and size play important roles in the uptake of microfibers by organisms. Thus, we strongly suggest that the properties of microplastics used in future laboratory exposure experiments be considered, with the aim of being “environmentally relevant” i.e., similar to what is found in nature.