Methanogen communities and predominant methanogenic pathways in three saline-alkaline lakes on the Tibetan Plateau

Abstract:

[Objective] To analyze the dominant methanogenic communities and methanogenic pathways in the different saline-alkaline lakes at the Qinghai-Tibet Plateau. [Methods] Using the sediments from three saline-alkaline lakes, Gongzhu Co, Kunzhong Co and Zigetang Co, that have different salinities and plantation types, as objects, we analyzed archaeal 16S rRNA diversity via high-throughput sequencing, and quantified the dominant methanogenic groups using quantitative PCR. The dominant methanogenic groups were then confirmed by comparing methane producing rates of the sediments from all known methanogenic substrates (methanol, trimethylamine, acetate and H₂/CO₂). Upon inhibition of methane production by a methanogenesis-specific inhibitor (2-bromoethanesulfonate), accumulated methanogenic precursors were determined so as to infer methanogenic pathways in the lake sediments. [Results] Methanosarcinaceae (11%), Methanosaetaceae (7.9%) and Methanomicrobiales (7.4%) were determined to be dominant in Kunzhong Co; Methanosaetaceae was accounted for 15% and 15.3% in Gongzhu Co and Zigetang Co, respectively, including the genera of Methanobacterium and Methanolobus. The highest methane production rates were determined from acetate and methanol in Gongzhu Co and Kunzhong Co respectively, but there was no difference in methane production rate from different methanogenic substrates in Zigetang Co. Methanol and acetate were respectively accumulated in methanogensis inhibited Kunzhong Co and Gongzhu Co, but no substance was obviously accumulated in Zigetang Co. [Conclusion] Methylotrophic methanogens and their implemented methanogenic pathway could be dominant in Kunzhong Co; and acetoclastic methanogens were prevalent in Gongzhu Co. However, not much methane production and substrate accumulation were determined in Zigetang Co. Based on the analysis, the dominant methanogenic pathways and methanogenic communities were predicted to be associated more with vegetation type but less with salinities of the saline-alkaline lakes on the Tibetan Plateau.