Bipartite trophic levels cannot resist the interference of microplastics: A case study of submerged macrophytes and snail

Some studies frequently focus on the toxic effects of compound pollution formed by microplastics and other pollutants on individual organisms, but it is still unclear how multi-trophic level organisms in compound communities resist the stress of microplastics. Thus, this research used a dose-response experiment (0, 0.1, 0.2, 0.5, 1 mg L) to illustrate the influences that microplastics might have on two symbiotic freshwater organisms Vallisneria natans and Sinotaia quadrata. The results showed the reduction of V. natans biomass in 0.5 and 1 mg L groups (28-38 %), and disturbances on the photosynthetic system, reduced the chlorophyll content (15-85 %) and maximum quantum yields (10-31 %). In the case of S. quadrata, which subsisted by scraping leaf biofilms, there was a disruption in the functioning of the antioxidant system. Concurrently, the activities of digestive and neurotransmitter enzymes were affected, potentially leading to detrimental impacts on the organism's essential physiological processes. The introduction of microplastics significantly enhanced the relative abundance of specific microbial taxa, such as Proteobacteria within the biofilm of V. natans leaves and chloroflexi in the rhizosphere, thereby altering the microbial community assembly process. This means the potential ecological functions with microbes as the carrier was influenced. These results indicated that microplastic in aquatic environments can impact the metabolism, autotrophic, and heterotrophic behavior of double-end trophic organisms through symbiotic activities. Therefore, our study reveals how polystyrene microplastics affect the growth of submerged aquatic plants and snails, and from the perspective of community integrity and health, the introduction of these pollutants into freshwater environments may cause disruptive effects.