NO is an important driver of nitrite-dependent anaerobic methane oxidation bacteria and CH fluxes in the reservoir riparian zone.

Nitrite-dependent anaerobic methane oxidation (N-DAMO) is an important biological process that combines microbial nitrogen and carbon cycling and is mainly carried out by nitrite-dependent anaerobic methane-oxidizing bacteria. The discovery of this microbial process has changed the conventional view of methane oxidation and nitrogen loss. In this study, the abundance, diversity, and community structure of N-DAMO bacteria were investigated based on high-throughput sequencing and fluorescence quantitative PCR measurements. We examined environmental factors driving the variations of CH fluxes and N-DAMO bacterial using correlation analysis and redundancy analysis. We found low CH fluxes and abundant N-DAMO bacteria in the riparian zone. After decomposing the effects of single variables and exploring them, NO was the only significant factor that significantly correlated with the abundance and richness of the N-DAMO community and gas fluxes (p < 0.05). Under the influence of three different land use types, the increase in NO (grassland vs. woodland and sparse woods, + 132.81% and + 106.25%) caused structural changes in the composition of the N-DAMO bacterial community, increasing its abundance (- 9.58% and + 21.19%), thus promoting the oxidation of CH and reduced CH emissions (+ 4.78% and + 35.63%) from the riparian zone. Appropriate NO input helps maintain the existing low methane emission fluxes in the riparian zone of the reservoir.