Community Characteristics of nosZ-Type Denitrifiers and Their Influencing Factors in Reservoir Sediments of the Northeastern Qinghai-Tibet Plateau
Reservoirs are significant sources of nitrous oxide (N2O), a potent greenhouse gas. The nosZ-type denitrifying bacteria, which reduce N2O to inert N2, play a critical role in mitigating emissions. This study investigated the community structure, diversity, and abundance of nosZ-type denitrifiers in surface sediments (0-15 cm) from 18 reservoirs in the northeastern Qinghai-Tibet Plateau, including 10 in the Yellow River mainstem and 8 in the Huangshui River basin. Sampling occurred during dry (May 2023) and wet (August 2023) seasons. High-throughput sequencing of the nosZ gene and quantitative PCR were employed. Results showed that Proteobacteria dominated (78.91%). Paracoccus and Halomonas were biomarkers in the Yellow River mainstem. Diversity was significantly higher in the Huangshui basin (P<0.05), with no temporal difference. Gene abundance was higher in the Huangshui basin (165.24×10^5 copies/g) than in the Yellow River mainstem (34.43×10^5 copies/g), and higher in wet season (128.55×10^5 copies/g) than dry season (61.27×10^5 copies/g) (P<0.05). Redundancy analysis and hierarchical partitioning identified sediment temperature, pH, total phosphorus, and water total nitrogen as key drivers, explaining 17.14%, 16.89%, 13.83%, and 11.23% of community variation, respectively. These findings reveal significant spatiotemporal heterogeneity and provide a scientific basis for N2O mitigation in plateau reservoirs.