Aerobic methane production in oxygenated water column of lake ecosystems

我们进行了野外和室内研究，以确定湖泊生态系统中好氧甲烷的产生途径。野外研究表明，许多湖泊在分层期溶解CH4浓度往往在地表以下达到最大值。特别是，大的、少营养的湖泊倾向于形成大的CH4最大值。此外，CH4最大值的季节性发生与浮游微生物（聚球菌）的丰度密切相关，表明微生物即使在氧气存在的情况下也会产生CH4。此外，微观环境实验表明，在缺磷湖水中添加甲基膦酸（MPn）可产生好氧CH4，表明甲基膦酸（MPn）表达了一种碳磷裂解酶，用于磷的利用并从MPn中产生CH4。本研究揭示了好氧微生物及其膦酸盐代谢与CH4生成之间的因果关系，阐明了在许多贫营养湖泊中观察到的新的甲烷生成途径。

We conducted the field and laboratory studies to identify the aerobic methane production pathways in lake ecosystems. The field studies revealed that dissolved CH4 concentrations often exhibit a subsurface maximum during the stratified period in many lakes. In particular, large, oligotrophic lakes tended to form large CH4 maximum. Moreover, seasonal occurrence of the CH4 maximum was closely related to the abundance of planktonic microbes (Synechococcus), suggesting CH4 production by microbes even in the presence of O2. Furthermore, the microcosm experiments showed the aerobic CH4 production when methylphosphonic acid (MPn) was added to the P-deficient lake water, suggesting the expression of a carbon-phosphorus lyase for P utilization and producing CH4 from MPn. The present study revealed the causal relationships between aerobic microorganisms, their phosphonate metabolism, and CH4 production, which clarify the novel methane production pathway observed in many oligotrophic lakes.