Effect of plastic pollution on freshwater flora: A meta-analysis approach to elucidate the factors influencing plant growth and biochemical markers

The deterioration in the water quality of urban water bodies through plastic contamination is emerging as a matter of serious concern. Microplastics (MPs) and nanoplastics (NPs) both affect the growth and productivity of aquatic flora. However, there have been a lot of variations in the reported studies which calls for revisiting the results with an analytical approach. Therefore, this study was designed to systematically evaluate the publications based on PRISMA (2020) guidelines. In this connection, 43 eligible articles were selected for meta-analysis followed by subgroup analysis to determine the impact of size, concentration, plastic polymers, and effect of plant classes on several physiological and biochemical parameters (growth, chlorophyll-a, carotenoids, protein, and antioxidant enzymes). The results indicated that the higher concentrations of plastics negatively affected the growth, and also enhanced the protein content and antioxidative enzyme activity. While, NPs were found to impart an inhibitory effect on pigment contents, along with a significant increase in protein content and antioxidative enzyme activity. Among the plastic polymers, dibutyl phthalate (DBP) showed a comparatively higher effect on growth, whereas the photosynthetic pigments were disrupted to a greater extent in the presence of polyvinyl chloride (PVC) plastics. Moreover, the growth parameters under plastic exposure were affected in the algal members to a greater extent in comparison to the other plant groups. Lastly, several plants like Komvophoron, Elodea, Myriophyllum, Nostoc, Raphidocelis, Scenedesmus, Utricularia, Dunaliella, and Lemna appeared to be more tolerant than others (Tolerance Index ≥ 0.8), showing a significantly minimal effect on growth inhibition.