Key Takeaways & Executive Findings
- •• • Proteobacteria dominated nosZ-type denitrifiers at 78.91% relative abundance, indicating a narrow phylum-level diversity that may simplify microbial management strategies for N2O reduction in high-altitude reservoirs. • • nosZ gene abundance was significantly higher in the Huangshui River basin (165.24×10^5 copies/g) than in the Yellow River mainstem (34.43×10^5 copies/g), a 4.8-fold difference that underscores spatial heterogeneity in denitrification potential. • • Wet season nosZ gene abundance (128.55×10^5 copies/g) exceeded dry season (61.27×10^5 copies/g) by 2.1-fold (P<0.05), implying seasonal hydrological control on microbial functional capacity. • • Sediment temperature, pH, total phosphorus, and water total nitrogen collectively explained 59.09% of community variation (individual contributions: 17.14%, 16.89%, 13.83%, 11.23%), providing quantifiable targets for environmental management to optimize N2O reduction.
Abstract
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.
1. Introduction
Reservoirs are increasingly recognized as hotspots for nitrous oxide (N2O) emissions, a greenhouse gas with a global warming potential ~300 times that of CO2. The microbial reduction of N2O to dinitrogen, catalyzed by nosZ-type denitrifiers, represents the only known biological sink for this gas. However, in high-altitude plateau reservoirs, the community composition and environmental controls of these functional microbes remain poorly characterized, limiting our ability to predict and mitigate N2O fluxes. Existing studies in lowland systems have shown that factors such as organic carbon, nitrogen availability, and temperature shape denitrifier communities, but the extreme conditions of the Qinghai-Tibet Plateau—low temperatures, intense UV radiation, and oligotrophic sediments—may drive distinct community dynamics.
This study addresses the critical knowledge gap by systematically surveying 18 reservoirs across two contrasting basins in the northeastern Qinghai-Tibet Plateau. By employing high-throughput sequencing and quantitative PCR, we quantified the abundance and diversity of nosZ-type denitrifiers across spatial and temporal scales. The identification of key environmental drivers, including sediment temperature, pH, and nutrient levels, provides actionable insights for reservoir management aimed at reducing N2O emissions. Our findings not only advance the fundamental understanding of nitrogen cycling in extreme environments but also offer a scientific basis for developing targeted mitigation strategies in plateau aquatic systems.
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XIA Liang, MAO Xufeng, WEI Xiaoyan, YU Hongyan, ZHANG Lele, DU Kai, YANG Yongxiao, WU Yi (2026). Community Characteristics of nosZ-Type Denitrifiers and Their Influencing Factors in Reservoir Sediments of the Northeastern Qinghai-Tibet Plateau. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202605007
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Frequently Asked Questions
What are the dominant phyla and genera of nosZ-type denitrifiers in the studied reservoirs, and how do they differ between basins?
Proteobacteria dominated at 78.91% relative abundance. In the Yellow River mainstem, Paracoccus and Halomonas were identified as biomarkers, while no genus-level biomarkers were detected in the Huangshui River basin. This suggests distinct community structures potentially driven by environmental conditions.
How does nosZ gene abundance vary seasonally and spatially, and what are the implications for N2O emissions?
Gene abundance was significantly 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 the wet season (128.55×10^5 copies/g) than the dry season (61.27×10^5 copies/g) (P<0.05). This indicates greater N2O reduction potential in the Huangshui basin and during wet periods, which may correlate with lower N2O emissions.
Which environmental factors most strongly influence the community structure of nosZ-type denitrifiers?
Redundancy analysis and hierarchical partitioning identified sediment temperature (17.14%), pH (16.89%), total phosphorus (13.83%), and water total nitrogen (11.23%) as the most influential factors, collectively explaining 59.09% of the variation. These factors should be monitored and managed to modulate denitrifier communities.
What is the significance of the observed diversity differences between the two basins?
The Huangshui River basin exhibited significantly higher diversity (P<0.05) than the Yellow River mainstem. Higher diversity may confer functional resilience to environmental changes, potentially stabilizing N2O reduction rates. This suggests that management strategies should consider basin-specific microbial ecology.
How do these findings inform reservoir management for N2O mitigation?
By identifying key environmental drivers and spatial/temporal patterns, managers can prioritize interventions such as controlling nutrient inputs (TP, TN) and monitoring temperature and pH to enhance nosZ-type denitrifier activity. The higher abundance in the Huangshui basin suggests that efforts to reduce N2O emissions may be more effective there, while the Yellow River mainstem may require additional measures to boost denitrifier populations.
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