Response of Microbial Communities and Biogeochemical Cycle Functions to Sediment Physicochemical Properties and Microplastic Pollution Under Damming and Water Diversion Projects

Abstract

Understanding the interactions among flow-sediment, microorganisms, and biogeochemical cycles is crucial for comprehending the ecological response mechanisms of dams and water diversion. This study focused on the spatial patterns of carbon, nitrogen, phosphorus, and sulfur (CNPS) cycle genes in the Danjiangkou Reservoir (consisted of the Han and Dan reservoirs), in combination with the sediment physicochemical properties and microplastic pollution. The results showed microbial communities were sensitive to changes in sedimentary mud content. The communities exhibited greater β diversity due to finer sediment particles in the Han Reservoir, whereas in the Dan Reservoir, despite having higher sediment nutrient content and MPs pollution, did not display this pattern. The quantitative microbial element cycling results confirmed the extensive and abundant of chemolithotrophic microbes and strong N cycle activity resulting from long-term water storage and diversion operation. And the denitrification intensity of Han Reservoir was higher. Near the pre-dam area, biological nitrogen fixation, phosphorus removal and sulfur reduction were increased obvious. Dam construction refines sediment, fostering the growth of different biogeochemical cycling bacteria and increasing the abundance of CNPS cycling genes. Additionally, the presence of MPs showed a positive correlation with S cycling genes and a negative correlation with C and N cycling genes.

Keywords: Microbial Communities, Dam, Biogeochemical Cycling genes, Microplastics, Sediment Particle Grading