Ni Renjie, Wang Yangqing, Lei Yu, Song Liyan
School of Resources and Environmental Engineering, Anhui University, Hefei, 230601, China; Anhui Shengjin Lake Wetland Ecology National Long-term Scientific Research Base, Dongzhi, 247230, China.
Research Center of Environmental Microbiology and Ecology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Science, Chongqing, 400714, China.
Environ Res. 2023 Nov 15;237(Pt 2):117025. doi: 10.1016/j.envres.2023.117025. Epub 2023 Aug 30.
Three Gorges Reservoir (TGR) water fluctuation creates high water level (HWL) and low water level (LWL) condition in TGR aquatic ecosystem. HWL fluies significant nutrients, mainly introducing carbon and nitrogen into the ecosystem. The nitrogen input is a concern for water quality management of TGR since the possible eutrophication caused by nitrogen spike. Sediment denitrification is widely recognized as the dominant nitrogen removal process in freshwater ecosystem. Therefore, the response of TGR sediments microbiome to the input nitrogen flucatution is crucial for both nitrogen balance and the eutrophication status of the ecosystem. Using high throughout sequencing of 16S rRNA gene and the predicted denitrification enzyme, and qualitative PCR of denitrification functional genes, we investigated how TGR sediments denitrification microbiome respond to the input nitrogen flux during two seasonal water fluctuation events. Concomitant to expected input carbon and nitrogen, we observed distinct microbial community structure and denitrification microbiota in HWL and LWL, and also in seasonal sampling events. Sediments pH, total nitrogen and nitrate were the significant impact factors in shaping the microbial community structure. Important denitrification microbiota (e.g., Saprospiraceae, Gemmatimonadaceae, Pseudomonas) are the main taxa of the microbial community and also showed water level and seasonal variation. The relative abundance of denitrification enzyme (nar, nir, nor, nos) and function genes (nirS, nirK, nosZ) were higher in LWL than HWL. Denitrification enzyme were significantly (p < 0.05) correlated with the nitrate concentration. In addition, the relative abundance of denitrification enzyme and function genes increased during the transition from 2014 HWL to 2015 LWL. Results suggested that TGR sediments denitrification is nitrate concentration dependent. The denitrification microbiome is initially inhibited due to high nitrate input, then they developed denitrification ability in response to high nitrate concentration.
三峡水库（TGR）的水位波动在其水生生态系统中形成了高水位（HWL）和低水位（LWL）状态。高水位带来大量养分，主要是向生态系统中输入碳和氮。氮的输入是三峡水库水质管理的一个关注点，因为氮含量激增可能导致富营养化。沉积物反硝化作用被广泛认为是淡水生态系统中主要的氮去除过程。因此，三峡水库沉积物微生物群对输入氮波动的响应对于生态系统的氮平衡和富营养化状态都至关重要。通过对16S rRNA基因进行高通量测序以及预测反硝化酶，并对反硝化功能基因进行定量PCR，我们研究了三峡水库沉积物反硝化微生物群在两个季节性水位波动事件期间对输入氮通量的响应。与预期的碳和氮输入相伴，我们在高水位和低水位以及季节性采样事件中都观察到了不同的微生物群落结构和反硝化微生物群。沉积物的pH值、总氮和硝酸盐是塑造微生物群落结构的重要影响因素。重要的反硝化微生物群（如腐螺旋菌科、芽单胞菌科、假单胞菌属）是微生物群落的主要分类群，并且也表现出水位和季节变化。反硝化酶（nar、nir、nor、nos）和功能基因（nirS、nirK、nosZ）的相对丰度在低水位时高于高水位。反硝化酶与硝酸盐浓度显著（p < 0.０5）相关。此外，从2014年高水位向2015年低水位过渡期间，反硝化酶和功能基因的相对丰度增加。结果表明，三峡水库沉积物反硝化作用依赖于硝酸盐浓度。反硝化微生物群最初因高硝酸盐输入而受到抑制，然后它们会响应高硝酸盐浓度而发展出反硝化能力。
