海斗深渊烃类有机碳生物矿化机理

Hadal trench as one important part of the global ocean has a wide range of material and energy exchange between the upper ocean and ocean crust, and it is one of the important marine organic carbon storage on earth. However, up to date the knowledge of its internal carbon transfer and recycling mechanism is limited. This proposal focus on biogeochemical cycle of organic carbon in such high pressure and low temperature extreme environment, and mainly carry out the following three aspects. Firstly, using the means of organic geochemistry to analysis the composition and source of information of the hydrocarbons in sediments. Secondly, through geological Microbiology techniques to detect the spatial variation of microorganisms with hydrocarbon degrading metabolism in the sediments, then we can establish the coupling changes between the organic geochemical parameters and microbial metabolic pathways in the hadal sediments. Thirdly, with simulation experiments, we will further evaluate the mineralization mechanism of hydrocarbon. From the above results, we can not only provide a theoretical basis for hydrocarbon biomineralization in the hadal ocean, but also can further promote the comprehensive understanding of the global carbon cycle and climate change on earth.

地球表面最深区域-海斗深渊作为全球海洋的重要构成单元，其内部碳储是全球碳库的重要组成。然而，目前国内外对深渊底部碳元素所涉及的迁移转化和再循环机制的认知十分匮乏。本课题以深渊底部碳的生物地球化学循环为研究主题，聚焦于烃类有机碳的生物矿化途径及其发生机制，主要从以下三个方面展开工作：1.通过地球化学手段来获取深渊底部沉积物中烃类有机碳的组成、含量、分布形式和单体碳稳定同位素信息，从而追索烃类有机碳矿化的有机地球化学印迹；2.通过微生物学手段分析深渊烃代谢微生物的多样性、丰度、分布规律及其基因组学信息，从而获取烃类有机碳矿化的地质微生物学记录；3.同时，开展室内高压低温模拟实验，进一步评估烃类有机碳的生物矿化速率，并揭示其矿化途径和内在机理。本课题潜在的成果将对认识深渊底部碳循环规律有着重要意义，同时还能为深入探索全球碳循环和全球气候变化等科学问题提供新的启示。

本项目以采自马里亚纳马里亚纳海沟南坡及雅浦海沟北部5058m-10911m水深的沉积物和岩石样品为对象，进行了有机地球化学、孔隙水地球化学和地质微生物分析，研究了深渊有机碳特征与来源，探讨了深渊有机碳的矿化的主要途径。主要研究结果如下：1）马里亚纳海沟南部沉积物中TOC随水深的增加，整体呈增加的趋势；2）有机质来源主要是海洋自生产物，陆源输入的比例非常小；3）相较于开放大洋，深渊沉积物中含丰度较高的细菌br-GDGTs，推测其可能源于水岩反应所孕育的化能自养微生物群落，即海沟沉积物中部分有机碳可能与水岩反应引起的化能生命活动有关；4）深渊沉积物中记录了与热液、古老海相沉积或石油烃污染相似的烷烃特征，推测可能与水岩反应有关；5)结合地质微生物学和深渊区的间隙水离子浓度特征，利用数学模型探讨了深渊有机碳（包括烃类物质）的早期成岩过程中有机碳矿化的主要途径。