Root Adsorption of Microplastic Particles Affects the Submerged Freshwater Macrophyte Egeria densa

Microplastics cause extensive contamination of water environments worldwide. As such, microplastics in freshwater systems have received increased attention in recent years. However, the effects of microplastics on freshwater macrophytes remain poorly understood. This study investigates the effects of microplastics on the submerged freshwater macrophyte Egeria densa. A laboratory experiment with controlled light, temperature, and nutrient conditions was conducted to explore the effects of exposure to low-concentration microplastics on the elongation, pigmentation, oxidative stress, antioxidant responses, and chlorophyll fluorescence parameters of E. densa. E. densa, planted soilless in aquaria, were exposed to 0.05, 0.25, 1.25, and 6 mg L−1 of 3-µm polystyrene microspheres for 7 days. Changes in pigmentation, oxidative stress, antioxidants, and chlorophyll fluorescence parameters were observed even after exposure to the lowest concentration of microplastics. None of these responses correlated with increasing microplastic concentration. Elongation and photosynthetic pigments did not change significantly. Microscopic observations confirmed that the microplastic particles were not absorbed into tissues but were adsorbed to the roots. The microplastic concentration of 0.25 mg L−1 was the threshold concentration value for E. densa. Our findings highlight the significant effects of microplastic on freshwater macrophytes. Further research is required to investigate the long-term responses to microplastic exposure.