Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, PR China; College of Environment, Hohai University, Nanjing 210098, PR China.
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, PR China; College of Environment, Hohai University, Nanjing 210098, PR China.
Sci Total Environ. 2023 Dec 15;904:166710. doi: 10.1016/j.scitotenv.2023.166710. Epub 2023 Aug 29.
Wetlands are the largest natural methane source, but how submerged macrophytes affect methane emission remains controversial. In this study, the impacts of submerged macrophytes on methane fluxes, water purification, and epiphytic microbial community dynamics were investigated in simulated wetlands (with and without Hydrilla verticillata) treated with norfloxacin (NOR) for 24 days. Mean methane fluxes were significantly lower in treatments with Hydrilla verticillata (56.84-90.94 mg/m/h) than bulks (65.96-113.21 mg/m/h) (p < 0.05) during the experiment regardless of NOR. The relative conductivity (REC) values, HO, and malondialdehyde (MDA) contents increased in plant leaves, while water nutrients removal rates decreased with increasing NOR concentration at the same sampling time. The partial least squares path model analysis revealed that plant physiological indices and water nutrients positively affected methane fluxes (0.72 and 0.49, p < 0.001). According to illumina sequencing results of 16S rRNA and pmoA genes, α-proteobacteria (type II) and γ-proteobacteria (type I) were the dominant methanotroph classes in all epiphytic biofilms. The ratio of type I/type II methanotrophs and pmoA gene abundance in epiphytic biofilm was considerably lower in treatment with 16 mg/L NOR than without it (p < 0.05). pmoA gene abundance was negatively correlated with methane fluxes (p < 0.05). Additionally, the assembly of epiphytic bacterial community was mainly governed by deterministic processes, while stochastic dispersal limitation was the primary assembly process in the epiphytic methanotrophic community under NOR stress. The deterministic process gained more importance with time both in bacterial and methanotrophic community assembly. Network analysis revealed that relationships among bacteria in epiphytic biofilms weakened with time but associations among methanotrophic members were enhanced under NOR stress over time. It could be concluded that submerged macrophytes-epiphytic biofilms symbiotic system exhibited potential prospects to reduce methane emissions from wetlands under reasonable management.
湿地是最大的自然甲烷源，但水生植物如何影响甲烷排放仍存在争议。本研究通过模拟湿地（有和没有水蕴草），在诺氟沙星（NOR）处理 24 天后，研究了水生植物对甲烷通量、水净化和附生微生物群落动态的影响。无论是否存在 NOR，水蕴草处理组（56.84-90.94mg/m/h）的甲烷通量均显著低于空白对照组（65.96-113.21mg/m/h）（p<0.05）。在同一采样时间内，随着 NOR 浓度的增加，植物叶片的相对电导率（REC）值、HO 和丙二醛（MDA）含量增加，而水养分去除率降低。偏最小二乘路径模型分析表明，植物生理指标和水养分对甲烷通量有积极影响（0.72 和 0.49，p<0.001）。根据 16S rRNA 和 pmoA 基因的 illumina 测序结果，α-变形菌（II 型）和γ-变形菌（I 型）是所有附生生物膜中优势的甲烷氧化菌类群。与无 NOR 相比，在 16mg/L NOR 处理组中，附生生物膜中 I 型/II 型甲烷氧化菌的比例和 pmoA 基因丰度显著降低（p<0.05）。pmoA 基因丰度与甲烷通量呈负相关（p<0.05）。此外，附生细菌群落的组装主要受确定性过程控制，而在 NOR 胁迫下，附生甲烷氧化菌群落的组装过程主要受随机扩散限制。无论是在细菌还是甲烷氧化菌群落的组装过程中，随着时间的推移，确定性过程的重要性都在增加。网络分析表明，随着时间的推移，附生生物膜中细菌之间的关系减弱，但在 NOR 胁迫下，随着时间的推移，甲烷氧化菌成员之间的关联增强。由此可以得出结论，在合理管理下，水生植物-附生生物膜共生系统具有减少湿地甲烷排放的潜力。
