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深海冷泉活动及化能合成生态系统的长期原位监测与实验
张雄
Subtype博士
Thesis Advisor张鑫
2024-05-17
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Degree Name理学博士
Degree Discipline海洋地质
Keyword冷泉 化能合成生态系统 天然气水合物 深海原位观测系统 原位实验
Abstract

冷泉广泛分布在全球主动和被动大陆边缘的海底,从深层到浅层沉积物甚至海水释放出富含甲烷和硫化氢等还原性气体的地质流体。在大多数情况下,碳氢化合物的主要成分是甲烷,甲烷在适当的压力和温度条件下积聚成天然气水合物,天然气水合物被认为是未来的潜在清洁能源。冷泉喷口周围聚集着甲烷氧化古细菌和硫酸盐还原菌,它们参与了一种被称为甲烷的厌氧氧化(Anaerobic Oxidation of Methane, AOM)的生命循环过程,这一过程为与冷泉有关的大量生态群落提供了能量。本文通过自主研发的深海原位观测系统(Long-term Ocean Observation Platform, LOOP),系统地研究了南海台西南盆地Site F冷泉系统的长时序列生境参数、冷泉渗漏活动的驱动机制以及这些活动对冷泉生态系统的影响。本研究在Site F进行了超过两年的连续监测,收集并深度挖掘了大量有关冷泉渗漏活动、环境参数变化以及其与底栖生物群落动态响应的原位数据。

研究表明,冷泉渗漏活动受到潮汐变化和海底压力变化的显著影响,这揭示了Site F冷泉渗漏活动的主要影响因素。此外,本研究利用自主研发的深海原位观测系统在冷泉喷口处开展了原位实验,提出了天然气水合物在冷泉生态系统中充当电容器的新模型。这一模型指出,天然气水合物缓冲了来自下方的甲烷瞬时喷发,并确保甲烷以稳定的方式扩散至上层孔隙水中,从而支持了长期稳定的化能合成生态系统。这一发现不仅为理解化能合成生态系统的稳定机制提供了新思路,也为未来在冷泉区域及其与全球化能合成群落之间相互作用的评估中,考虑天然气水合物作为电容器的角色提供了科学依据。

此外,本研究还通过深海原位观测系统在冷泉区域的长期部署,探讨了深海长期原位监测技术在极端海洋环境中的应用潜力,并为深海探测平台设计提供了重要的技术支撑。监测平台获取的原位监测数据丰富了冷泉区域的生物地球化学数据集,也为进一步理解深海冷泉生态系统的复杂相互作用机制奠定了基础。

本研究利用自主研发的深海原位观测系统在深海冷泉领域的初步尝试,丰富了我们对地球深海极端环境下生命存在和演化规律的认识,同时也为深海资源的探索利用、全球碳循环的研究以及地球生命起源的探索提供了新的技术手段。未来研究将继续在冷泉生态系统这一天然试验场开展原位实验和长期原位监测,以期获得更多关于冷泉生态系统与冷泉流体的生物地球化学过程的新证据。

关键词:冷泉,化能合成生态系统,天然气水合物,深海原位观测系统,原位实验

Other Abstract

Cold seeps are widely distributed on the seabed along both active and passive continental margins globally, releasing geological fluids rich in reductive gases such as methane and hydrogen sulfide from deep-seated sediments to shallow sediments and even seawater. In most cases, the primary component of hydrocarbons is methane, which accumulates into natural gas hydrates under appropriate pressure and temperature conditions. Natural gas hydrates are considered a potential clean energy source for the future. Around cold seep vents, methane-oxidizing archaea and sulfate-reducing bacteria congregate, participating in a life cycle process known as the anaerobic oxidation of methane (AOM). This process provides energy for extensive ecological communities associated with cold seeps. This study systematically investigated the long-term habitat parameters, driving mechanisms of seep activities, and their impact on the cold seep ecosystem at Site F in the Taixinan Basin of the South China Sea using a self-developed Long-term Ocean Observation Platform (LOOP). Continuous monitoring was conducted for over two years at Site F, collecting and deeply analyzing a large amount of in-situ data on cold seep activities, environmental parameter changes, and the dynamic response of benthic communities.

The study revealed that cold seep activities are significantly influenced by tidal variations and seabed pressure changes, identifying these as major factors affecting seep activities at Site F. Additionally, in-situ experiments were conducted at cold seep vents using the self-developed LOOP, proposing a new model where natural gas hydrates act as "capacitors" in the cold seep ecosystem. This model suggests that natural gas hydrates buffer instantaneous methane eruptions from below and ensure the stable diffusion of methane into the upper pore water, thereby supporting a long-term stable chemosynthetic ecosystem. This discovery provides new insights into the stability mechanisms of chemosynthetic ecosystems and offers a scientific basis for considering the role of natural gas hydrates as capacitors in future assessments of cold seep areas and their interactions with global chemosynthetic communities.

Furthermore, the long-term deployment of the LOOP in the cold seep area explored the potential of long-term in-situ monitoring technology in extreme marine environments, providing significant technical support for the design of deep-sea exploration platforms. The in-situ monitoring data obtained enriched the biogeochemical dataset of the cold seep area and laid a foundation for further understanding the complex interaction mechanisms of deep-sea cold seep ecosystems.

This study's preliminary attempt to utilize a self-developed LOOP in the field of deep-sea cold seeps has enhanced our understanding of life existence and evolution in extreme deep-sea environments. It also provides new technical means for the exploration and utilization of deep-sea resources, the study of the global carbon cycle, and the exploration of the origin of life on Earth. Future research will continue to conduct in-situ experiments and long-term in-situ monitoring in the natural laboratory of cold seep ecosystems, aiming to obtain more new evidence on the biogeochemical processes of cold seep ecosystems and fluids.

KEYWORDSCold seep, Chemosynthetic ecosystems, Natural gas hydrate, Long-term Ocean Observation Platform, In situ experiments

MOST Discipline Catalogue理学::海洋科学
Language中文
Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/185284
Collection海洋地质与环境重点实验室
Recommended Citation
GB/T 7714
张雄. 深海冷泉活动及化能合成生态系统的长期原位监测与实验[D]. 中国科学院海洋研究所. 中国科学院大学,2024.
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