三峡库区夏季万州段底泥甲烷功能菌群落对甲烷排放的影响

Effects of functional methane community in sediments of Wanzhou section of the Three Gorges Reservoir on methane emissions in summer

三峡水库是世界上最大的人工水库,其潜在甲烷释放近年来备受关注。目前将甲烷排放量与甲烷功能菌的生长与作用机制相结合开展研究的报道较少。为探究三峡库区夏季万州段甲烷功能菌群落对甲烷排放的影响,分别于2019年7月和9月采集了三峡库区万州段底泥,利用16S rRNA基因高通量测序技术,对该区域的万州干流和高阳、黄石支流在属水平上的甲烷功能菌群落组成结构以及甲烷功能菌群落与甲烷排放通量间的关系进行了研究。结果表明:监测期间内高阳、黄石、万州平均甲烷通量为(0.874±0.011)、(0.884±0.234)、(0.507±0.262)μmol·(m^(2)·h)^(-1),支流大于干流,总体表现为甲烷排放“源”。在产甲烷菌群落中,部分未分类产甲烷古菌unclassified_p_Euryarchaeota、environmental_samples_f_Methanosarcinaceae以及未命名古菌对产甲烷影响较大,该类细菌可促进甲烷产生。在甲烷氧化菌群落中,Methylobacter、Methylosarcina以及未分类氧化菌对甲烷氧化有较大影响,当该类细菌占比增加时会加速甲烷氧化,从而减少水-气界面中的甲烷排放。除甲烷功能菌群以外,推测温度与河流回水顶托作用也是导致干、支流甲烷排放出现差异的重要因素。以上研究结果可对揭示水库甲烷排放与甲烷功能菌生长和作用机制的关系提供参考。

The Three Gorges Reservoir is the largest artificial reservoir in the world,and its potential methane release has attracted much attention in recent years.At present,there are few reports on combining methane emission with the growth and action mechanism of methane functional bacteria.In order to explore the impact of functional methane bacterial communities in the Wanzhou section of the Three Gorges reservoir area on methane emissions in summer,sediments from the Wanzhou section of the Three Gorges reservoir area were collected during July and September 2019.16S rRNA gene high-throughput sequencing technologies were used to study the composition and structure of the methane functional bacteria community at the genus level in Wanzhou mainstream,Gaoyang and Huangshi tributaries in the region,as well as the relationship between the methane functional bacteria community and methane emission fluxes.The results showed that during the monitoring period,the average methane fluxes in Gaoyang,Huangshi,and Wanzhou were(0.874±0.011),(0.884±0.234),(0.507±0.262)μmol·(m^(2)·h)^(-1),and the tributaries were higher than the main streams,and they were generally methane emission sources.In the methanogen community,some unclassified methanogenic archaea unclassified_p_Euryarchaeota,environmental_samples_f_Methanosarcinaceae and unnamed archaea had a greater impact on methanogenesis than other bacteria,and they could promote methane production.In the methanotrophic community,Methylobacter,Methylosarcina and unclassified oxidizing bacteria had a greater influence on methane oxidation than other bacteria.When their proportion increased,methane oxidation could be accelerated,thereby reducing methane emissions at the water-air interface.In addition to the functional methane flora,it was speculated that temperature and river backwater support were also important factors that could cause the difference in methane emissions between dry and branch streams.The research results lay the foundation for the growth and action mechanism of methane functional bacteria that reveal the temporal and spatial changes of methane emissions from reservoirs.