Tian Linqi, Yan Zaisheng, Wang Changhui, Xu Shengqi, Jiang Helong
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Sci Total Environ. 2021 Jun 10;772:145594. doi: 10.1016/j.scitotenv.2021.145594. Epub 2021 Feb 4.
Biological nitrogen fixation (BNF) in sediments is an important source of bioavailable nitrogen in aquatic systems. However, the effect of habitat change caused by eutrophication on nitrogen fixation within sediments is still unclear. In this study, nitrogen fixation rates and diazotroph diversities in sediments with heterogeneous ecological status in one eutrophic lake were investigated by using an isotope tracer method and sequencing of nitrogen-fixing (nif) genes. The results showed that both nitrogenase activity (NA) and nifH abundance in sediments of blooms area were higher than those in vegetation-dominated habitats. Correlation analysis showed that NA was correlated closely to nifH abundance, dissolved sulfide, and iron. The diazotrophic assemblage contained mainly Proteobacterial sequences belonging to Cluster I and III, and the variations of diazotrophic community could be explained by total nitrogen content, total phosphorus content, organic matters, sulfides, ammonium and iron content. Moreover, the co-occurrence network analysis showed the Alphaproteobacteria shaped the major interactions in diazotrophic community, and sediment properties had stronger effect on diazotrophic community in cyanobacteria-dominated habitat. This study revealed that habitat heterogeneity in eutrophic lakes shaped different succession of BNF in sediments and cyanobacterial blooms significantly improved the nitrogen-fixing activity in sediments, which broadened our understanding of nitrogen cycle and nutrient management in eutrophic freshwater lakes.
沉积物中的生物固氮是水生系统中生物可利用氮的重要来源。然而，富营养化导致的栖息地变化对沉积物中固氮作用的影响仍不清楚。在本研究中，利用同位素示踪法和固氮（nif）基因测序，研究了一个富营养化湖泊中具有不同生态状态的沉积物中的固氮率和固氮微生物多样性。结果表明，水华区域沉积物中的固氮酶活性（NA）和nifH丰度均高于以植被为主的栖息地。相关性分析表明，NA与nifH丰度、溶解态硫化物和铁密切相关。固氮微生物组合主要包含属于第一和第三类群的变形菌序列，固氮微生物群落的变化可以用总氮含量、总磷含量、有机物、硫化物、铵和铁含量来解释。此外，共现网络分析表明，α-变形菌在固氮微生物群落中形成了主要的相互作用，沉积物性质对以蓝藻为主的栖息地中的固氮微生物群落影响更强。本研究表明，富营养化湖泊中的栖息地异质性塑造了沉积物中生物固氮的不同演替，蓝藻水华显著提高了沉积物中的固氮活性，这拓宽了我们对富营养化淡水湖泊氮循环和养分管理的理解。
