九龙江口及厦门近岸水体颗粒物附着微生物生态研究

On the western coast of the Taiwan Strait, Jiulong River is the second largest river that discharges into the sea, exerting important impacts on the seawater environment and ecosystem of the Xiamen coast. The ecological environment of the Jiulong River estuary is influenced by both anthropogenic and natural processes, which are highly dynamic and complex. Consequently, the species composition, sources and biogeochemical functions of the particle-associated microorganisms are also highly diverse and complex in this environment. The particle-associated microbial communities not only influence the vertical flux of particulate organic carbon (POC) in seawater (i.e., the biological pump effect for carbon sequestration), but also influence the horizontal flux of POC from the land to the sea at the estuary. Furthermore, the particle-associated microbial communities also influence the horizontal POC flux between the East China Sea and the South China Sea, two of the largest marginal seas in the western Pacific Ocean. Research on these is scientifically important and highly challenging. This project is going to take the Jiulong River Estuary, Xiamen Bay and its adjacent coastal water as the research area, using molecular ecology and biogeochemical techniques, to study the temporospatial variation and controlling environmental factors of the species composition, community structure and abundance of particle-associated bacteria and archaea along the estuarine gradient. We will also investigate the species composition, sources, abundance, metabolic activities, temporospatial distribution and controlling environmental factors of particle-associated ammonia-oxidizing bacteria and ammonia-oxidizing archaea, which are targeted as the exemplar functional groups of microorganisms in our project. The results of our research will provide valuable scientific foundation for environment protection of the estuarine and bay areas.

九龙江是台湾海峡西岸第二大入海河流，对厦门近岸海水环境及生态系统产生重要影响。九龙江口生态环境受人为和自然因素双重影响，复杂多变，使得该环境中的颗粒物附着微生物的种类和来源及生物地球化学功能亦复杂多样。颗粒物附着微生物不但影响颗粒有机碳在水体中的垂直传输通量（即生物泵作用），而且在河口还影响颗粒有机碳的陆-海水平传输通量，并在台湾海峡影响颗粒有机碳在西太平洋两大边缘海（东海和南海）间的水平传输通量，其研究科学意义重大并极具挑战。本项目将以九龙江口、厦门湾及邻近近海为研究海域，利用分子生态学和生物地球化学等相关技术，解析水体颗粒物附着细菌和古菌在河口环境梯度下的种类组成、群落结构和丰度的时空变化规律及环境控制因子，并以氨氧化细菌和氨氧化古菌为例，研究颗粒物附着微生物特定功能群的种类组成、来源、丰度、代谢活性、时空分布及环境控制因子等生态特征，为河口和海湾的生态环境保护提供科学依据。

九龙江是台湾海峡西岸第二大入海河流，对厦门近岸海水环境及生态系统产生重要影响。本项目以九龙江河口、厦门近岸及邻近近海为研究海域，研究了水体颗粒物附着细菌和古菌总群落及活性群落在河口环境梯度下的种类组成、群落结构和关键类群相对丰度的时空变化及环境控制因子。对比九龙江河口与台湾海峡发现，台湾海峡水体微生物多样性显著高于九龙江河口微生物多样性，并且，颗粒物附着与自由生活生态位分化在台湾海峡水体更为显著，揭示了河口与近海可能具有不同的水体颗粒物组成及生物可利用性。潜在活性群落研究发现，河口颗粒物微环境有利于厌氧微生物生长，产甲烷古菌主要分布在九龙江河口水体颗粒物上，而自由生活氨氧化古菌（AOA）和颗粒物附着AOA都是河口优势类群，表明不同于寡营养大洋环境，高颗粒物含量及动态多变河口环境，有利于AOA颗粒物附着与自由生活两种不同生态型分化。β-变形菌纲氨氧化细菌（β-AOB）研究表明，九龙江河口最优势β-AOB是Nitrosomonas属细菌，其相对丰度在大多数站位和采样月份显著高于Nitrosospira属β-AOB，尤其在颗粒物上及在河口上游淡水为主站位，Nitrosomonas属β-AOB具有最高相对丰度。种系发生系统进化分析表明，九龙江河口一些AOA和Nitrosomonas属β-AOB可能源于土壤或淡水环境，说明九龙江通过河口向海洋输送颗粒物同时，输送了颗粒物附着陆源微生物。应用微生物群落网络构建，对九龙江河口颗粒物附着微生物群落与自由生活微生物群落间潜在互作进行了解析，发现正相关网络中，Rhodobacteraceae、Flavobacteriaceae、Alteromonadaceae、Pseudoalteromonadaceae等颗粒物附着细菌与SAR11、SAR86、Actinomarinaceae等自由生活细菌间可能存在顺序性的颗粒有机物降解、溶解有机物共享等代谢合作。