Bladder entrance of microplastic likely induces toxic effects in carnivorous macrophyte Utricularia aurea Lour

The global distribution of microplastic (particle size < 5 mm) is of growing concern, especially in aquatic environments where it may cause adverse effects on resident organisms. To date, however, few studies have focused on the impacts of microplastic on aquatic plants. Here, we conducted a microcosm study to investigate the toxic effects of microplastic on the carnivorous aquatic macrophyte Utricularia aurea Lour. Based on microscopic images and Raman spectrum analysis, we found that most polyvinyl chloride (PVC) particles were smaller than the valve of U. aurea bladders, thus allowing entrance into the plant, but this was not so for polyethylene (PE) particles. Furthermore, PVC (50 mg L^-1) had significantly negative effects on growth and physiological parameters such as macrophyte length, chlorophyll content, and fluorescence, whereas, at the same concentration, PE had no such effects. Further analysis revealed that after bladder removal, the macrophytes did not respond to PVC particle toxicity. Thus, intake of microplastics (i.e., PVC) through bladders is likely responsible for inducing toxic effects to the growth and physiological parameters of U. aurea.