Many seasonally stratified lakes accumulate substantial amounts of the greenhouse gas methane in the anoxic zone. Methane oxidizing bacteria in the water column act as a converter, oxidizing methane into carbon dioxide and biomass before it reaches the atmosphere. Current observations and estimates of this methane oxidation efficiency are diverging, especially for the lake overturn period. Here, we combine a model of turbulent mixing, gas exchange, and microbial growth with a comprehensive data set for autumn mixing to quantify the relevant physical and microbial processes for a 16 m deep, wind-sheltered Swiss lake. Scenario analysis suggests that the methane converter is efficient and robust under a large range of mixing velocities and only rare events of pronounced surface cooling can trigger substantial outgassing. This case study combines in situ observation and a deterministic physically based model and suggests that the frequency of storms may strongly impact methane emissions for similar temperate lakes.

中文翻译：

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湖泊翻覆过程中微生物甲烷氧化效率和稳健性

许多季节性分层的湖泊在缺氧区积累了大量的温室气体甲烷。水柱中的甲烷氧化细菌充当转换器，在甲烷到达大气之前将其氧化成二氧化碳和生物质。目前对这种甲烷氧化效率的观察和估计存在分歧，尤其是在湖泊倾覆时期。在这里，我们将湍流混合、气体交换和微生物生长模型与秋季混合的综合数据集相结合，以量化 16 m 深、防风的瑞士湖的相关物理和微生物过程。情景分析表明，甲烷转化器在大范围的混合速度下高效且稳健，只有罕见的显着表面冷却事件才能触发大量除气。