Structure Characteristics of Microbial Communities in Different Functional Regions of Qingshui River.

Microbial communities play a crucial role in the processes of material cycling, energy conversion, and information transfer in river water. Analyzing the distribution characteristics of microbial community structure is crucial for preserving the long-term stability of river water ecosystems. In order to investigate the structure characteristics of the microbial communities and the relationships between microbial communities and hydrochemical compositions in agricultural region and urban region of Qingshui River, a total of 20 river water samples, including 13 samples from the agricultural region and 7 samples from the urban region, were collected from the River. The hydrogeochemical methods, high-throughput sequencing technology, and bioinformatics analysis were used to determine the relationships between microbial communities and hydrochemical compositions in the different functional regions of the River. The results showed that river water is generally weakly alkaline water (8.35≤pH≤9.44). The chemical type of river water is mainly HCO3-Ca•Mg water (80%), followed by Cl-Ca•Mg water (20%). Hydrochemical compositions in agricultural region were mainly controlled by the carbonate dissolution and agricultural fertilization inputs, while these in the unban region were primarily affected by the upstream hydrochemical characteristics and unban discharges. The hardening of river bottoms and its banks resulted in lower level of microbial diversity in the urban region than that in the agricultural region, and further caused the differences in microbial community structure. Limnohabitans, Rhodobacter and Flavobacterium were identified as the main genus in the agricultural region, and Cyanobium_PCC-6307, Limnohabitans and norank_f_norank_o_Chloroplast were the primary genus in the urban region. The order of the influence of hydrochemical factors on microbial community structure was NO₃^- (P=0.001)>SO₄^2- (P=0.003)>DO(P=0.071)>pH(P=0.222), and among these NO₃^- emitted from agricultural fertilization has the most significant impact on the microbial community structure in the River. NO₃^- concentrition in river water was increased by the microbial nitrification process in the agricultural region, whereas it was decreased by microbial denitrification process between the agricultural region and the urban region. [ABSTRACT FROM AUTHOR]