HUB AMBIENTAL UPLA, Laboratory of Aquatic Environmental Research, Centro de Estudios Avanzados, Universidad de Playa Ancha, Valparaíso, Chile; Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2085, 2340950 Valparaíso, Chile.
Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2085, 2340950 Valparaíso, Chile.
Environ Int. 2021 Sep;154:106575. doi: 10.1016/j.envint.2021.106575. Epub 2021 Apr 23.
Freshwater ecosystems are responsible for an important part of the methane (CH) emissions which are likely to change with global warming. This study aims to evaluate temperature-induced (from 5 to 20 °C) changes on microbial community structure and methanogenic pathways in five sub-Antarctic lake sediments from Magallanes strait to Cape Horn, Chile. We combined in situ CH flux measurements, CH production rates (MPRs), gene abundance quantification and microbial community structure analysis (metabarcoding of the 16S rRNA gene). Under unamended conditions, a temperature increase of 5 °C doubled MPR while microbial community structure was not affected. Stimulation of methanogenesis by methanogenic precursors as acetate and H/CO, resulted in an increase of MPRs up to 127-fold and 19-fold, respectively, as well as an enrichment of mcrA-carriers strikingly stronger under acetate amendment. At low temperatures, H/CO-derived MPRs were considerably lower (down to 160-fold lower) than the acetate-derived MPRs, but the contribution of hydrogenotrophic methanogenesis increased with temperature. Temperature dependence of MPRs was significantly higher in incubations spiked with H/CO (c. 1.9 eV) compared to incubations spiked with acetate or unamended (c. 0.8 eV). Temperature was not found to shape the total microbial community structure, that rather exhibited a site-specific variability among the studied lakes. However, the methanogenic archaeal community structure was driven by amended methanogenic precursors with a dominance of Methanobacterium in H/CO-based incubations and Methanosarcina in acetate-based incubations. We also suggested the importance of acetogenic H-production outcompeting hydrogenotrohic methanogenesis especially at low temperatures, further supported by homoacetogen proportion in the microcosm communities. The combination of in situ-, and laboratory-based measurements and molecular approaches indicates that the hydrogenotrophic pathway may become more important with increasing temperatures than the acetoclastic pathway. In a continuously warming environment driven by climate change, such issues are crucial and may receive more attention.
淡水生态系统是甲烷（CH）排放的重要组成部分，而甲烷排放可能随着全球变暖而发生变化。本研究旨在评估从麦哲伦海峡到合恩角的智利海峡五个亚南极湖底沉积物中，温度诱导（5 至 20°C）变化对微生物群落结构和产甲烷途径的影响。我们结合了原位 CH 通量测量、CH 产生速率（MPR）、基因丰度定量和微生物群落结构分析（16S rRNA 基因的代谢组学）。在未添加任何物质的情况下，温度升高 5°C 会使 MPR 增加一倍，而微生物群落结构不受影响。添加乙酸和 H/CO 等产甲烷前体刺激产甲烷作用，可使 MPR 分别增加 127 倍和 19 倍，并且在乙酸添加下，mcrA 载体的富集程度显著增强。在低温下，H/CO 衍生的 MPR 要低得多（低至 160 倍），但氢营养型产甲烷作用的贡献随着温度的升高而增加。添加 H/CO 的培养物的 MPR 对温度的依赖性明显高于添加乙酸或未添加的培养物（c. 0.8eV）。温度并未改变总微生物群落结构，而是表现出在所研究的湖泊之间具有特定地点的可变性。然而，产甲烷古菌群落结构受添加的产甲烷前体驱动，在基于 H/CO 的培养物中以甲烷杆菌为主，在基于乙酸的培养物中以甲烷八叠球菌为主。我们还提出了在低温度下，产乙酸的 H 生成比氢营养型产甲烷作用更具优势，进一步得到了微宇宙群落中同型乙酸生成菌比例的支持。原位和基于实验室的测量以及分子方法的结合表明，随着温度的升高，氢营养型途径可能比乙酰营养型途径变得更为重要。在气候变化驱动的持续变暖环境中，此类问题至关重要，可能会受到更多关注。
