[Analysis of the Spatial Changes in Bacterial Communities in Urban Reclaimed Water Channel Sediments: A Case Study of the North Canal River].

Sediment bacteria have attracted much attention because of their important roles in energy flow and pollutant cycle transformation. The changes in the spatial distribution pattern of bacteria are the basis for research on the biodiversity generation and maintenance mechanisms. However, there are few studies on the spatial variation in benthic microorganisms and its biogeographic models. The highly artificial North Canal River across the Beijing-Tianjin-Hebei area was chosen as the research area in this study. The spatial variation in the different classification levels of the Kingdom, Phylum, Class, Order, Family, Genus, Species, and operational taxonomic units and their diversity formation mechanisms were analyzed. The results showed that the samples at different classification levels had a more homogeneous distribution pattern. There were clearer distribution boundaries at the low classification levels than at the high classification levels. The significance of the bacterial community variation increased as the classification level of the bacterial community decreased. Furthermore, the difference between groups increased and the similarities within groups decreased as the classification level of the bacterial community decreased. The typical rhizosphere microorganisms represented by Frankiales and Rhodobacterales showed significant enrichment in the upstream samples, followed by the midstream samples and a significant decrease in the downstream samples. Microorganisms related to the carbon, nitrogen, and sulfur cycles represented by Anaerolineales and Desulfobacterales showed significant enrichment in the midstream, followed by the downstream and a significant reduction in the upstream. The genus was significantly enriched in the upstream followed by the midstream, and was significantly reduced in the downstream. The pathogenic bacteria represented by and showed a significant enrichment pattern in the midstream. The contents of Ca, SO, and total organic carbon (TOC) in the downstream samples were significantly higher than those in the upstream and midstream samples. The discharge of untreated wastewater downstream increased the salt and TOC contents in the sediment. The ecological restoration project in the sediment of the riparian zone decreased the salt and TOC contents in the upstream and midstream samples. Environmental selection was the main driving factor of the pattern of spatial variation in the bacterial communities in the sediments of the North Canal River.