Aquatic habitats beneath ice masses contain active microbial ecosystems capable of cycling important greenhouse gases, such as methane (CH₄). A large methane reservoir is thought to exist beneath the West Antarctic Ice Sheet, but its quantity, source and ultimate fate are poorly understood. For instance, O₂ supplied by basal melting should result in conditions favourable for aerobic methane oxidation. Here we use measurements of methane concentrations and stable isotope compositions along with genomic analyses to assess the sources and cycling of methane in Subglacial Lake Whillans (SLW) in West Antarctica. We show that sub-ice-sheet methane is produced through the biological reduction of CO₂ using H₂. This methane pool is subsequently consumed by aerobic, bacterial methane oxidation at the SLW sediment–water interface. Bacterial oxidation consumes >99% of the methane and represents a significant methane sink, and source of biomass carbon and metabolic energy to the surficial SLW sediments. We conclude that aerobic methanotrophy may mitigate the release of methane to the atmosphere upon subglacial water drainage to ice sheet margins and during periods of deglaciation.

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微生物氧化作为甲烷在南极冰盖下沉入

冰块下方的水生生境包含活跃的微生物生态系统，能够循环利用重要的温室气体，例如甲烷（CH ₄）。人们认为，在南极西部冰盖下存在着大量的甲烷气藏，但人们对其数量，来源和最终命运知之甚少。例如，通过基础熔融提供的O ₂应该导致有利于好氧甲烷氧化的条件。在这里，我们使用甲烷浓度和稳定同位素组成的测量值以及基因组分析来评估南极西部西冰湖Whillans（SLW）中甲烷的来源和循环。我们表明，通过使用H ₂对CO ₂进行生物还原可产生冰层以下甲烷。甲烷池随后被SLW沉积物-水界面处的好氧细菌甲烷氧化所消耗。细菌氧化消耗> 99％的甲烷，并代表大量的甲烷汇，并且是表层SLW沉积物的生物质碳和代谢能的来源。我们得出结论，好氧的甲烷氧化层可能会减少冰川下水排到冰盖边缘和冰消期期间甲烷向大气中的释放。