Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, PR China; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, PR China.
Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, PR China.
Mar Environ Res. 2023 Sep;190:106119. doi: 10.1016/j.marenvres.2023.106119. Epub 2023 Jul 27.
Denitrification is the dominant process of nitrogen removal and nitrous oxide (NO) emissions in estuarine ecosystems. However, little is known regarding the microbial mechanism of the production and reduction of NO in estuaries. We investigated in situ dissolved NO as well as potential NO production rate (NPR), reduction rate (NRR), and emission rate (NER), and key functional genes related to NO transformation of denitrification in the Pearl River Estuary. Higher NO emission potential was found in the upstream and midstream regions with higher NPR and lower NRR values. In contrast, higher NRR values were detected in downstream. Notably, nirS and nirK type NO producers dominated the upstream zone, whereas abundant NO reducers, especially nosZ II type NO reducers, were observed in downstream. Most importantly, the gene abundance ratio (R) was significantly correlated with the NO emission potential (R). Niche differentiation between NO producers and NO reducers from upstream to downstream affected NO emission potential. This study highlights the NO emission potential in estuarine sediments is determined by an imbalance between NO production and the reduction of multi-bacterial communities.
反硝化作用是河口生态系统中氮去除和氧化亚氮（NO）排放的主要过程。然而，对于河口NO 的产生和还原的微生物机制知之甚少。我们调查了珠江河口原位溶解态 NO 以及潜在的 NO 产生速率（NPR）、还原速率（NRR）和排放速率（NER），以及与反硝化作用 NO 转化相关的关键功能基因。在上游和中游地区，较高的 NPR 和较低的 NRR 值导致了更高的 NO 排放潜力。相比之下，下游地区的 NRR 值更高。值得注意的是，nirS 和 nirK 型 NO 产生菌在上游区域占主导地位，而下游则存在丰富的 NO 还原菌，尤其是 nosZ II 型 NO 还原菌。最重要的是，基因丰度比（R）与 NO 排放潜力（R）呈显著相关。NO 产生菌和还原菌从上游到下游的生态位分化影响了 NO 排放潜力。本研究强调了河口沉积物中的 NO 排放潜力是由多细菌群落中 NO 产生和还原之间的不平衡决定的。
