生物标志物及其碳同位素在冷泉区生物地球化学研究中的应用

APPLICATION OF BIOMARKERS AND CARBON ISOTOPES TO COLD SEEP BIOGEOCHEMICAL PROCESSES

  • 摘要: 甲烷通量在很大程度上控制着海底冷泉区生物地球化学过程及生态系统。缺氧甲烷氧化(AOM)作用是消耗CH4的一种重要途径,主要是由甲烷氧化古菌和硫酸盐还原菌共同调节的,其反应机制及碳循环可以利用生物标志物及其碳同位素比值来表征。这两种微生物所产生的特定生物标志物都具有相对负的δ13C值,且硫酸盐还原菌生物标志物的δ13C值要比古菌的略偏正,说明在AOM过程中,甲烷碳从古菌到细菌的传递。甲烷通量决定海底冷泉区微生物群落结构,通量高时以ANME-2古菌群落为主,而OH-AR和BIPH两个生物标志物指标可以指示古菌群落结构变化。所以,利用生物标志物及其δ13C值不仅能够证明AOM作用的存在和反应机制,还可以对冷泉区(尤其是古冷泉区)环境及微生物群落结构进行分析和重建。

     

    Abstract: Methane flux generally controls cold seep biogeochemical processes and ecosystem. Anaerobic oxidation of methane (AOM) is the major sink of CH4, which is mediated by methane-oxidizing archaea and sulfate-reducing bacteria, and the mechanisms of AOM can be traced using biomarkers and their carbon isotope ratios. Biomarkers for these microbes are depleted in 13C, and the δ13C values of sulfate-reducing bacteria biomarkers are enriched compared to those of archaeal biomarkers, indicating CH4 carbon has flowed from archaea to bacteria during AOM. Methane flux also determines the microbial community structure of cold seeps, with the ANME-2 cluster dominating when CH4 flux is high. Cold seep microbial community structure changes can be traced by the two biomarker indices, OH-AR and BIPH, with higher values for both when ANME-2 cluster dominates. Thus, biomarkers and their δ13C values can not only provide evidence suppoting the occurrence of AOM, but they can also be used to study environments and microbial consortium structure for both modern and ancient cold seeps.

     

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