南海深部微生物参与有机质、甲烷转化的作用、过程和机制的研究

The subseafloor sedimentary biomass has been estimated to comprise around one tenth to one third of all biomass, a huge carbon reservoir of between 56 and 303 pg of carbon, equivalent to that of all plant life on Earth. However, the biogeochemical roles of these huge number of microorganisms in the subsurface remains largely unknown. Previous microbial diversity analysis of the South China Sea sediments have revealed that majority of the microbes in the sediments are uncultivated, their physiology and ecological roles are unknown. This project will investigate and reveal the relationships of the quantity, components of microorganisms and organic matters, the geochemical elements and phsical factors in contrasting sedimentary environments as shallow water vs deep water; oligotrophic vs organicotrophic; oil gas area vs normal area. Based on the in-situ investigations, focusing on the organic matter transformation and methane cycling, combining the feeding of isotope labelled compounds and simulation of deep-sea environments in the laboratory, we will try to illuminate the scale, process and mechanisms of microorganisms in the organis matter transformation, methane production and oxidation in the deep SCS. Our study will be a very important componant in our understanding and answering the key scientific questions such as the roles and influences of microorganisms in the deep SCS in the carbon cycling and formation of oil gas energy; the relationship of the ecosystems in the deep SCS and the above.

海洋沉积物中微生物的数量据估算可能占据了全球生物总量的1/10~1/3，储存了约56-303pg的碳，相当于地球上所有植物的碳总量。然而，目前对这些数量巨大的海底微生物的地球化学功能和作用绝大部分尚处于未知的状态。前期南海沉积物微生物种类调查显示绝大部分微生物尚未培养，生理和功能未知。本研究计划系统调查比较南海浅水和深水；相对贫营养和富营养区；油气区与普通海区沉积物柱中的微生物数量和组成与沉积物中有机质种类和数量，地球化学元素，物理因子等的相互关系。在现场调查基础上以有机质的微生物转化；甲烷的合成、分解为核心点，进一步结合同位素标记化合物喂养和实验室海底环境模拟，重点阐述南海深部微生物参与有机物的转化，甲烷生成与分解等代谢反应的规模、过程和机制。我们的研究将是认识和回答南海深部微生物在碳循环，油气藏深海能源的形成中的作用和影响；南海深部与与上层生态系统的关系等重要科学问题的重要组成部分。

海洋沉积物是地球上最大的有机碳库，微生物在沉积物有机质的转化中起到了重要作用，沉积物中赋存的巨量甲烷大部分也是微生物成因，甲烷的生物合成是大分子有机质降解的最后步骤。分子生物学和微生物生态学的发展使我们对沉积物中存在的微生物种类有了基本的了解，然而目前对这些数量巨大的沉积物微生物不同类群参与的地球化学功能和机制绝大部分尚处于未知的状态。本项目研究以南海北部陆坡不同海区沉积物为重点研究对象（瓜伊马斯海盆沉积物为参照），对沉积物开展了地化参数分析和分子生态多样性分析；甲烷合成速率的检测；甲烷代谢微生物类群的确定，结合有机地球化学数据，分析甲烷代谢微生物的分布特征，与环境因子的相关关系；对甲烷代谢微生物开展富集培养和机制研究，对沉积物有机质降解进行机制解析。通过项目的执行鉴定了南海北部陆坡不同海域沉积物中微生物的类型，解析了部分代谢特征和分布规律；富集了2-3 类参与有机质转化、甲烷产生和分解的古菌类群；解析了沉积物中重要的有机质和甲烷转化微生物的作用机制，提出和绘制了微生物介导沉积物中碳循环的模型；发表高水平SCI 论文17 篇，核心中文期刊论文1篇；培养博士、硕士研究生8名。