You Aiju, Zheng Qiaoxi, Yao Pengcheng
Zhejiang Key Laboratory of River-Lake Water Network Health Restoration, Hangzhou, Zhejiang, China.
Zhejiang Institute of Hydraulics and Estuary (Zhejiang Institute of Marine Planning and Design), Hangzhou, Zhejiang, China.
Front Microbiol. 2025 Jul 1;16:1578657. doi: 10.3389/fmicb.2025.1578657. eCollection 2025.
The Yubei plain river network (YPRN) is confined and has poor hydrodynamics, resulting in the accumulation of pollutants. Therefore, it is of great significance to explore the mechanisms by which different anthropogenic contamination sources-namely domestic, aquaculture, industrial, and agricultural-affect nitrogen content, as well as the composition of nitrifying, denitrifying, and other bacterial communities.
This study determined δN and δO by bacterial denitrification, and quantitatively evaluate the contribution of pollution source through MixSIAR. And the changes of the bacterial community were analyzed through 16S rRNA gene sequencing.
The concentration of total nitrogen (TN) revealed a distinct spatial pattern, with the industrial area demonstrating the highest levels, followed closely by the aquaculture area and the domestic and agricultural areas. The stable isotope analysis delineated three dominant pollution source areas within the study region: i) an industrial pollution dominant area, accounting for 55% of the pollutant load; ii) a domestic pollution dominant area (39%); and iii) an aquaculture pollution dominant area (43%). The industry pollution samples demonstrated the highest TN concentrations and the lowest /TN ratio. Strong nitrification activity under high dissolved oxygen (DO) in the study area was investigated using stable isotope analysis. Proteobacteria, Bacteroidetes, and Desulfobacteria were the dominant bacterial phyla in the study area. Notably, species with nitrate-reducing capabilities were significantly more abundant in the industrially pollution area compared to the other pollution areas.
The diversity of nitrogen types characteristic of the domestic pollution area mediated bacterial selection pressures, favoring nitrogen cycling and amplifying functional gene abundance. This bacterial activity enhanced nitrogen cycle efficiency, ultimately reducing nitrogen concentrations. Bacterial analyses revealed marked divergence in both community composition and function across different pollution types. Particularly, ecological network analysis showed greater complexity and more network links in the aquaculture pollution area. Overall, the results revealed the impacts of different pollution sources on the ecological processes shaping river microbial communities and determined variations in bacterial diversity and nitrogen-cycling gene abundances.
渝北平原河网（YPRN）受限制且水动力较差，导致污染物积累。因此，探究不同人为污染源（即生活、水产养殖、工业和农业污染源）影响氮含量以及硝化、反硝化和其他细菌群落组成的机制具有重要意义。
本研究通过细菌反硝化作用测定δN和δO，并通过MixSIAR定量评估污染源的贡献。通过16S rRNA基因测序分析细菌群落的变化。
总氮（TN）浓度呈现出明显的空间格局，工业区的TN浓度最高，其次是水产养殖区以及生活和农业区。稳定同位素分析确定了研究区域内三个主要污染源区：i）工业污染主导区，占污染物负荷的55%；ii）生活污染主导区（39%）；iii）水产养殖污染主导区（43%）。工业污染样本的TN浓度最高，而 /TN比值最低。利用稳定同位素分析研究了研究区域内高溶解氧（DO）条件下的强硝化活性。变形菌门、拟杆菌门和脱硫杆菌门是研究区域内的主要细菌门类。值得注意 的是，与其他污染区域相比，具有硝酸盐还原能力的物种在工业污染区域明显更为丰富。
生活污染区域特有的氮类型多样性介导了细菌选择压力，有利于氮循环并增加功能基因丰度。这种细菌活性提高了氮循环效率，最终降低了氮浓度。细菌分析表明，不同污染类型在群落组成和功能方面存在显著差异。特别是，生态网络分析显示水产养殖污染区域的复杂性更高，网络连接更多。总体而言，结果揭示了不同污染源对塑造河流微生物群落的生态过程的影响，并确定了细菌多样性和氮循环基因丰度的变化。
