Microplastic pollution in aquatic environments may facilitate misfeeding by fish

Numerous recent studies have documented ingestion of microplastics (MPs) by many aquatic animals, yet an explanation for misfeeding by fish remains unexplained. Here we tested the hypothesis that biofilm (biofouling) on MP surfaces due to exposure in the aquatic environment facilitates misfeeding in fish. Spherical polystyrene (PS) was cultured for 0–22 weeks in a freshwater environment to grow a biofilm on the MPs. Goldfish were employed in a simple feeding experiment with and without provision of genuine food at ecologically relevant MP concentrations. Absorbance (ABS), which is a proxy for biofilm formation, increased exponentially within three weeks of initiation and reached a plateau after approximately five weeks. Although fish did not swallow the MPs, “capture” occurred when food pellets were in the vicinity and significantly increased in probability with aging. Duration of capture also increased significantly with increasing aging. These results suggest that drifting of MPs in aquatic environments may facilitate fish misidentification of MPs as edible prey. [Display omitted] •Exposure of MPs to the aquatic environment affects fish feeding behaviour.•Biofilm formation on MPs surface rapidly occurs in aquatic environments.•An increase in exposure time increased the probability of “capture” by fish.•Capture time in the oral cavity by fish increased with increasing MP exposure duration.