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河流是淡水生态系统的重要组成部分,河道生态系统中的浮游微生物是河道生物多样性的重要组成部分,且与河流中溶解氧、pH、硝态氮、总磷和重金属等众多环境因子息息相关[1-3],做好河流微生物多样性研究是河流健康评价、水系连通与生态修复、供水安全保障等工作的重要基础。
近 30 年来,各国形成了侧重点不同、各具特色的评价方法,如,美国环境保护局(US EPA)提出的快速生物监测协议(Rapid Bio-assessment Protocols,RBP)[4]、欧盟的《水框架法令》(WFD) [5]等都已在河流水生态系统健康管理中得到应用。2020年世界自然基金会联合我国8家科研院所共同发布《长江生命力报告2020》,提出长江生命力指数。这些评价方法均将水生态作为重要维度。
微生物作为有机化合物的主要分解和矿化者[6-7],在食物链和食物网中所处的营养级比大型水生动植物更低[8],水体微生物网络的复杂性一定程度上能反应水体中大型生物的网络复杂性与社区对扰动的抵抗力和恢复力[9]。微生物群落结构、丰度等也可以作为有机物分解、反硝化功能的指标[10]。
近一个世纪以来,地表水微生物安全主要是通过检测粪便污染的细菌指标来确定[11] ,但除致病菌外,在地表水微生物监测中污染指示微生物更能反应水体受污染的现状[12]。有研究者[13]提出可以创建可靠、标准化的参考数据库,作为指示健康微生物群落的基线指标。通过相关性计算可以分析环境因子与物种分布间的相关关系[14]。已有研究发现微生物多样性指数与总磷和磷酸盐含量呈极显著负相关关系[15]。SOUFFREAU et al[16]也发现总磷和氨氮对湖泊的微生物群落组成有显著影响。
微生物多样性研究的传统方法是微生物分离纯化培养,存在如培养周期长、分类学鉴定不准确等弊端[17]。分子生物学技术可以高效、准确地从遗传物质水平上研究环境中微生物的群落结构[18]。高通量测序技术是近年来微生物群落分析的常用技术[19-21],具备测序快速、通量高等优势,且可对多样品的多个可变区同时测序[22]。通过高通量测序技术研究三江干流水体微生物群落结构及其多样性,可以为构建三江流域生态系统管理方案提供科学依据。
宁波市的余姚江、奉化江和甬江合称“三江”。三江口由于其独特的自然地理条件,成为宁波市的重要标志[23-24]。三江河道的治理方案主要为水利工程建设[20],需要对河道水生态进行长期综合监测以提供数据支撑,极有必要对其中微生物群落结构与多样性展开全面研究。当前对于宁波三江流域微生物群落结构与多样性的研究较为缺乏,本文开展的研究说明通过高通量测序的方法开展河流的生态指标监测具有可行性。
基于高通量测序的宁波三江干流微生物多样性分析
Analysis of microbial diversity of main stream of Yuyao-Fenghua-Yongjiang rivers watershed in Ningbo based on high throughput sequencing
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摘要: 为了解宁波三江干流水域微生物多样性,文章通过 16S rDNA、18S rDNA 基因扩增和高通量测序分析了自上游向下游方向的16 个采样点水域微生物群落结构组成及多样性差异。结果显示,不同采样点原核、真核微生物 Chao1和Observed species指数值较大,覆盖率均高于0.97。奉化江样品的真核微生物物种丰富度和多样性相对更高。门水平上,优势菌门包括变形菌门(Proteobacteria)、放线菌门(Actinobacteria)等,真核生物绿藻门(Chlorophyta)的平均丰度最高。Beta多样性分析显示,不同流域微生物群落组成表现出明显的区分性,余姚江、奉化江和甬江3组样品的微生物种群结构以及优势门有显著差异。结果表明,三江干流水域整体微生物丰富度与多样性较高,但是少数采样水域厚壁菌门(Firmicutes)的高丰度说明存在工业或生活污水排放导致的水体污染。Abstract: To have a full understanding of the microbial diversity in the main stream of Yuyao River, Fenghua River and Yongjiang River in Ningbo, the microbial community structure composition and diversity of 16 sampling points from upstream to downstream were analyzed by 16S rDNA, 18S rDNA gene amplification and high-throughput sequencing. The results showed that the Chao1 and Observed species index values of prokaryotic and eukaryotic microorganisms at different sampling points were large, and the coverage rate for both prokaryotic and eukaryotic microorganisms were higher than 0.97. The species richness and diversity of eukaryotic microorganisms in Fenghua River samples were relatively higher. As for the phylum level, the dominant bacteria included Proteobacteria, Actinobacteria, etc. For eukaryotic, the average abundance of Chlorophyta was the highest. Beta diversity analysis showed that the microbial community composition in different watersheds would show an obvious differentiation, and there were differences in the microbial population structure and dominant gate among Yuyao River, Fenghua River and Yongjiang River. The conclusion was the overall microbial richness and diversity in the main stream of the three rivers were high. However, the high abundance of Firmicutes in a few sampling watersheds indicated that there was water pollution caused by the industrial or domestic sewage discharge.
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表 1 三江干流航测断面及取样点位置分布
编号 位置描述 河流 C1 永思桥 YYJ C2 支流交汇处 YYJ C3 河流分叉前 YYJ C4 河流分叉汇聚后 YYJ C5 支流交汇处和弯曲处 YYJ C6 河流弯曲处,临近河姆渡遗址 YYJ C7 河流弯曲处 YYJ C8 澄浪堰 FHJ C9 支流后,甬江起点 YJ C10 支流交汇处,临近泛迪码头 YJ C11 支流交汇处 YJ C12 河流弯曲处,临近镇电新村 YJ C13 入海口 YJ PC1 国控断面补测点1 YYJ PC2 国控断面补测点2 YYJ PC3 水文站补测点 FHJ 注:余姚江(YYJ),奉化江(FHJ),甬江(YJ)。 -
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