近岸沉积物中海洋线虫与微生物的相互作用对氮去除过程的影响

The marine free-living nematodes represent the most ubiquitous, abundant and diverse metazoans. Their grazing and bioturbation activities have impacts on element cycles e.g. nitrogen in marine ecosystem. Among N cycle processes, denitrification and anaerobic ammonium oxidation are the important processes that can remove N from marine environment, which are the keys to mitigate marine inorganic nitrogen pollution. The "micro-food web" consisting of microbes and meiofauna can consume as high as 70% of the available organic matter in coastal ecosystems. However, the effects of the interaction between the food web components on nitrogen cycle have not yet been known. This project is to collect samples from the Shenzhen Bay and establish a micro-ecological culture system in lab, to study marine nematodes and microbes associated with denitrification and anaerobic ammonium oxidation, to understand the interaction between them. Coupling with the in situ multi-channel microelectrode technique to analyze the changes of nitrogen flux in sediments, this project is also to discuss the role of marine nematodes in the nitrogen removal processes, to unveil that marine nematodes activities could not be neglected in marine nitrogen cycle. The potential results can enrich the scientific understanding of the ecological function of marine nematodes and provide a scientific basis for assessing the role of marine nematodes in the marine nitrogen cycle.

海洋自由生活线虫是分布最广泛、数量最丰富、多样性最高的后生动物类群，其摄食和生物扰动活动可影响海洋生态系统中氮等元素循环。在海洋氮循环中，反硝化和厌氧氨氧化是将氮从海洋环境中去除的重要步骤，是缓解全球海洋无机氮污染问题的关键过程。沉积物中由微生物和小型底栖动物组成的“微食物网”对近海生态系统中可用有机物质的消耗率高达70%，然而，它们的内部相互作用机制对氮循环的影响却尚未清楚。本项目拟从深圳湾海域采集样品，在室内建立微生态培养体系，以海洋线虫、反硝化和厌氧氨氧化相关微生物为研究对象，从分子生物学角度分析海洋线虫和微生物间的相互作用关系，结合多通道原位微电极技术分析生态系统中氮通量变化，探讨海洋线虫在海洋反硝化和厌氧氨氧化过程中所扮演的角色，揭示海洋线虫活动在海洋氮循环中不可忽视的重要作用。研究结果可以丰富人们对海洋线虫生态功能的科学认识，为评估海洋线虫在海洋氮循环中的作用提供科学依据。

为研究海洋自由生活线虫与微生物的相互作用对氮素去除过程的影响，本课题以深圳湾底栖生态环境为研究区域，以沉积物中丰度最高的小型底栖动物-海洋线虫，以及细菌、古菌等微生物为研究对象，利用16S rRNA和18S rRNA基因高通量测序方法，对33个近岸沉积物样品中细菌、古菌和真核生物的多样性进行调查；对海洋线虫与细菌、海洋线虫与古菌的共现性进行网络分析，并采用Spearman统计学方法，识别出与海洋线虫共现性呈显著相关性的微生物种类。.在夏季，红树林和潮间带泥滩样品中线虫OTU相对丰度基本随深度增加而递减；冬季的红树林样品中发现相类似变化规律，只有在冬季潮间带泥滩样品中线虫OTU相对丰度在深层是显著高于表层的。相对丰度最高的海洋线虫隶属于单宫目、色矛目、刺嘴目和垫刃目，它们与热源体古菌、深古菌、γ-和δ-变形菌等微生物有显著正/负相关关系。【结论】在香港米埔湿地沉积物中，与相对丰度最高的5种线虫显著相关的几大类微生物均在碳、氮、硫等元素循环方面扮演十分重要的作用，暗示海洋线虫与微生物潜在的相互作用对元素地球化学循环具有重要影响。研究结果有助于深入了解线虫在生态系统中未被揭示的生态功能，有助于更清晰地认识海洋线虫在底栖生态系统中所扮演的角色。