NosZI microbial community determined the potential of denitrification and nitrous oxide emission in river sediments of Qinghai-Tibetan Plateau.

Denitrification in river sediments is the hotspot of nitrogen removal and nosZ I gene is essential for reducing nitrous oxide (N 2 O) emissions. However, few studies tried to link nosZ I communities with variations of denitrification rates in sediments along the high-elevation rivers. Here, we investigated the spatial variation of potential denitrification rates of sediments along a section (hereafter YJ) of the middle reaches of the Yarlung Zangbo River in the Qinghai-Tibetan Plateau. We also used the real-time quantitative PCR (qPCR) and high-throughput sequencing techniques to evaluate the abundance and composition of nosZ I-containing microbial groups. The influences of physicochemical factors and denitrifier communities on potential denitrification rates were further revealed through structural equation modeling. The obtained results indicated that potential denitrification rates and N 2 O/(N 2 O + N 2) ratio in the sediments along YJ section were greatly different. Moreover, the alpha diversity and composition of nosZ I-containing microbial community in river sediments differed remarkably, mainly driven by the ammonia nitrogen (NH 4 +-N), organic matter (OM) and pH in sediments. The relative abundances of Zoogloeaceae , Oxalobacteraceae , Rhodospirillaceae and Bradyrhizobiaceae significantly differed among five groups (P < 0.05). Structural equation modeling further suggested that nitrogen nutrients directly influenced the potential denitrification rates, while total phosphorus (TP) showed indirect effects on potential denitrification rates through modulating denitrifier abundances and nosZ I community. The abundance and composition of nosZ I community were powerful predictors in regulating denitrification rates and N 2 O/(N 2 O + N 2) ratio. Our findings highlight that the nosZ I-containing microbial groups play a non-negligible role in nitrogen removal and N 2 O mitigation in high-elevation river sediments. • Denitrification rates and nosZ I community spatially varied greatly. • Physicochemical factors and community explained 89.9% of denitrification variation. • Physicochemical properties indirectly control denitrification by altering community. • nosZ I community was a powerful predictor for denitrification and N 2 O emission. [ABSTRACT FROM AUTHOR]