Aerobic methane production in oxygenated water column of lake ecosystems

我们进行了野外和实验室研究，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，在许多湖泊中，溶解甲烷浓度在层化期间往往表现出次表层最大值。特别是，大的、营养稀少的湖泊倾向于形成大的甲烷最大值。此外，甲烷最大值的季节性出现与浮游微生物(聚球藻)的丰度密切相关，这表明即使在氧气存在的情况下，微生物也会产生甲烷。此外，微观世界实验表明，在缺磷的湖水中加入甲基膦酸(MPN)可以产生好氧甲烷，这表明存在一种碳磷裂解酶用于磷的利用，并由MPN产生CH4。本研究揭示了好氧微生物及其磷酸盐代谢和CH4产生之间的因果关系，阐明了在许多贫营养湖泊中观察到的新的甲烷产生途径。

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.