(Table 1) Methane concentrations, MOX rates and MOB abundance in arctic aquatic ecosystems of the Lena Delta, Northeast Siberia

Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a floodplain area. Though, in all aquatic systems we detected both, Type I and II MOB, in lake systems we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity.

北极永久冻土（permafrost）环境中储存着巨量有机碳，微生物活动可将该部分碳潜在矿化为甲烷——一种强效温室气体。本研究针对作为重要甲烷排放源的北极湖泊系统，评估了其甲烷收支、细菌甲烷氧化（methane oxidation, MOX）过程及潜在的环境调控因子。研究对位于西伯利亚勒拿三角洲萨莫伊洛夫岛的5个湖泊系统及邻近河流点位开展分析：采用放射性示踪剂估算甲烷氧化速率，借助分子生物学方法解析甲烷氧化细菌（methane-oxidizing bacteria, MOB）的丰度与群落组成。与河流系统相比，湖泊系统的甲烷浓度、MOB群落的丰度与组成，以及相应的甲烷氧化速率均存在高度变异。湖泊出水口及泛滥平原区域的复合湖泊群中，甲烷浓度与甲烷氧化速率均为最高。尽管所有水生系统中均检出I型与II型MOB，但湖泊系统的MOB多样性更高，包含典型土壤环境中的甲烷氧化细菌类群。永久冻土融化（permafrost thawing）驱动土壤MOB随环境过程输入至水生系统，或为调控MOB群落组成及潜在甲烷氧化能力的另一关键因素。