Impact of environmental factors on the diversity of nitrogen-removal bacteria in wetlands in the Sanmenxia Reservoir of the Yellow River

Purpose The wetland in the Yellow River Reservoir area of Sanmenxia is a habitat of mute swans and an important water source conservation area. Excessive nitrogen input can directly or indirectly threaten the ecological health of the wetland. To date, no systematic studies have investigated the effects of vegetation or environmental factors on the microbial communities, especially nitrogen-removal bacteria in the wetland of the Sanmenxia Reservoir on the Yellow River. This study aimed to uncover the correlations between nitrogen-removal bacteria communities, vegetation type, and environmental physicochemical properties in the Yellow River wetlands, laying a foundation for future studies of nitrogen cycling. Methods Sediment profile samples were collected and metagenomic sequencing was used to study the diversity and composition of microbial communities in wetland sediment. Nitrogen isotope tracing was performed to determine the denitrification and anammox rates. Results The dominant microorganisms of the wetland samples were bacteria. Subsequently, the community composition and taxonomic abundances were analyzed at the phylum and genus levels, which showed significant differences between-groups ( P < 0.01). Nitrogen removal occurred mainly through denitrification in YJW (a sampling site, maximum denitrification rate of 1.09 mg N kg −1 day −1 ) and anammox in TEH (another sampling site, maximum anammox rate of 0.14 mg N kg −1 day −1 ). The abundance of typical anammox and denitrifying bacteria at the genus level was generally consistent with reaction rates. The factors related to microbial community diversity on the genera included NH 4 + –N, total organic carbon, total nitrogen, and pH, but NH 4 + –N was the key factor that explained the difference between YJW and TEH in terms of community structure of nitrogen-removal microbes. Three highly significant nitrogen-removal communities and five nitrogen metabolism functional genes were screened by Spearman rank correlation coefficient analysis. Conclusion This study revealed the relationship between sediment microbial community structure, especially denitrification microorganisms, typical denitrification reaction processes, and environmental physicochemical properties in the Sanmenxia Yellow River Reservoir, which provides theoretical support for future studies on soil environmental nitrogen cycling mechanisms in this riverside wetland.