Removing excess nitrogen is crucial for the ecological restoration of eutrophic lakes. The process of nitrate reduction mediated by microorganisms in lakes is an important mechanism for denitrification. The lake ecosystem is facing complex and severe risks of invasive alien submerged plants and microplastic pollution. Invasive submerged plants differ from local submerged plants in terms of root exudation of organic matter and nitrogen assimilation efficiency, which can alter the nitrate dissimilatory reduction process in sediment. Microplastics can directly alter the physical and chemical properties of sediments, and indirectly affect the rate of nitrate dissimilatory reduction and the interrelationships of various processes by affecting the growth of submerged plants. However, it is not clear whether the diversity of invasive submerged plants affects the process of nitrate dissimilation and reduction in sediment under the background of microplastic pollution.

The aquatic plants and aquatic ecosystem health discipline group of the Chinese Academy of Sciences Wuhan Botanical Garden carried out a cross experiment on the addition of polystyrene microplastics (PS-MPs) and the invasion of submerged plant diversity, and analyzed the impact of the above factors on the physicochemical properties of sediment, microbial community structure and the potential rate of nitrate dissimilation reduction processes. The results indicate that the denitrification process is more sensitive to the diversity of invasive submerged plants than nitrate dissimilatory reduction to ammonium and anaerobic ammonia oxidation. However, The addition of PS MPs interferes with the impact of invasive submerged plant diversity on the process of nitrate dissimilatory reduction. The addition of PS MPs changed the physical and chemical environment of sediments, such as lowering the pH value of sediments and increasing the concentrations of nitrate nitrogen and ammonia nitrogen. PS MPs cause changes in sediment microbial communities: as the concentration of PS MPs increases, the unique genera of microbial communities increase, The increase in alpha diversity leads to a more stable microbial community structure. The changes in the physical and chemical properties of sediment by PS MPs create a more favorable environment for denitrification, further expanding the competitive advantage of denitrification in the process of nitrate reduction to ammonium. In addition, The addition of PS MPs inhibited the anaerobic ammonia oxidation process. Overall, the response of nitrate dissimilatory reduction to the diversity of invasive submerged plants exhibits process specificity. However, The addition of PS MPs leads to non synergistic effects, weakening the impact of invasive submerged plant diversity on nitrate dissimilatory reduction patterns.

The above achievements have expanded our understanding of the impact of submerged plant invasion and microplastic accumulation on sediment functional microbial communities and nitrogen cycling systems in lake ecosystems. Related research results include Does invasive submarging macroscopic diversity affect differentiation nitrate reduction processes in divisions with varying microplastics? The title was published in the Journal of Hazardous Materials. The research work is supported by the National Natural Science Foundation of China.



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Analysis of the impact of microplastics and invasive plant diversity on nitrate dissimilatory reduction in Wuhan Botanical Garden