真光层海水过饱和甲烷的来源及机制探讨

真光层海水中普遍存在甲烷过饱和现象，尤其是天然气水合物区真光层的甲烷明显异常。由于临近海气界面，真光层过饱和甲烷与大气甲烷排放及全球温室效应密切相关。目前，对真光层海水的过饱和甲烷来源仍没有统一的认识。综合前人研究成果梳理了真光层海水过饱和甲烷的来源，归纳了真光层海水过饱和甲烷现象形成的影响因素，进一步探讨了原位微生物可能参与的甲烷代谢机制。真光层过饱和甲烷可能来源于沉积物、临近河流或原位微生物，且受区域、季节、营养盐等多种因素的影响。由于受氧气影响，真光层海水甲烷产生的代谢机制有其特殊性，目前推测微生物可能依旧利用常规的产甲烷途径，它们存在于海水微厌氧环境中，或自身形成抵抗氧气影响的能力；此外，微生物也可能选择对氧不敏感的新的产甲烷途径。因此，针对天然气水合物区真光层甲烷过饱和现象，开展甲烷的来源和代谢机制的研究，以期为天然气水合物试采与开发的环境评价提供理论支撑，并为探究海水甲烷对大气及全球气候的影响提供理论依据。

Discussion on the sources and mechanism of supersaturated methane in euphotic seawater

Methane supersaturation occurs widely in the euphotic zone of oceans,especially in the areas with natural gas hydrate.It is closely related to atmospheric methane emission and global greenhouse effect due to the proximity of the sea-air interface.Up to date,it remains controversy concerning the source of supersaturated methane in euphotic seawater.This paper focuses on synthesizing the previous research results in order to sort out the sources of supersaturated methane,summarizing the influencing factors of supersaturated methane formation,and further exploring the mechanism of methane metabolism that in-situ microbes may participate in.The sources of supersaturated methane in euphotic zone may be transported from sediments,near-rivers or generated by in-situ microbes,and affected by various factors such as region,season,nutrient,and biological activities.Due to the influence of oxygen,the particularity of methanogenic mechanism is showed in euphotic seawater.Currently,it is speculated that conventional methanogenic pathways may be still performed by microorganisms,which exist in the micro-anaerobic environment of seawater,or generate the ability of resistance to oxygen;in addition,microorganisms may also choose new methanogenic pathways that are not sensitive to oxygen.Therefore,for the methane supersaturation phenomenon in euphotic seawater in natural gas hydrate area,the study of the sources and metabolic mechanisms of methane was carried out.It was hoped to provide theoretical support for the environmental assessment of gas hydrate test mining and development,and provide a theoretical basis for exploring the impact of seawater methane on the atmosphere and global climate.