Growth and physiological responses of Myriophyllum sp. “Roraima” growing in co-cultivation with Microcystis aeruginosa under the influence of microplastics

The distribution of microplastics as a potential environmental risk in aquatic systems had gained increasing attention in recent years. While numerous studies had focused on the impacts of microplastics on aquatic plants, the impacts on plant species cannot been considered in isolation. This study investigated the effects of relatively low concentrations of microplastics (0 mg/L, 0.05 mg/L, 0.25 mg/L, 1.25 mg/L, and 6 mg/L) on Myriophyllum sp. "Roraima" in co-cultivation with Microcystis aeruginosa (M. aeruginosa). Microscopic observations confirmed the adsorption of microplastic particles to the roots of Myriophyllum sp. "Roraima". The presence of cyanobacteria could mask and moderate the effects of microplastics, creating an integrated impact on plants. This integrated impact potentially made it challenging to isolate and attribute specific effects solely to microplastics. Additionally, the co-cultivation with M. aeruginosa had its own effect on the plants. Results revealed that the plant shoot elongation was not significantly altered under the treatment conditions; however, the photosynthetic pigments demonstrated different patterns between the emergent and submerged sections. The activities of antioxidant enzymes, Catalase (CAT) and Peroxidase (POD), were activated once microplastics were introduced, and Ascorbate peroxidase (APX) was significantly increased in high microplastics concentrations. The responses of Myriophyllum sp. "Roraima" to microplastics exposure differentiated from those observed in the absence of M. aeruginosa.