Abstract
Nitrous oxide (N2O) is a more potent greenhouse gas with an atmospheric lifetime of 121 years, contributing significantly to climate change and stratospheric ozone depletion. Lakes are hotspots for N2O release due to the imbalance between N2O sources and sinks. N2O-reducing bacteria are the only biological means to mitigate N2O emission, yet their roles in lakes are not well studied. This study investigated the potential for N2O reduction, keystones of typical and atypical N2O-reducing bacterial communities, and their correlations with environmental factors in the sediments of Lake Taihu through microcosm experiments, high-throughput sequencing of the nosZ gene, and statistical modeling. The results showed that potential N2O reduction rates in sediments ranged from 13.71 to 76.95 μg N2O g−1 d−1, with lower rates in December compared to March and July. Correlation analysis indicated that the nosZ II/nosZ I ratio and the trophic lake index (TLI) were the primary factors influencing N2O reduction rates and N2O-reducing bacterial community structures. The genera Pseudogulbenkiania and Ardenticatena were identified as the most abundant typical and atypical N2O-reducing bacteria, respectively, and were also recognized as the keystone taxa. Quantitative real-time PCR (qPCR) results revealed that nosZ II was more abundant than nosZ I in the sediments. Partial least squares path modeling (PLS-PM) further demonstrated that atypical N2O-reducing bacteria had significant positive effects on N2O reduction process in the sediments (p < 0.05). Overall, this study highlights the crucial ecological roles of atypical N2O-reducing bacteria in the sediments of the eutrophic lake of Taihu, underscoring their potential in mitigating N2O emissions.
Published Version
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