城市河流沉积物微生物量分布和群落结构特征

沉积物微生物是河流生态系统物质循环及水体净化的驱动力.为了探讨城市河流不同河段沉积物微生物量分布和群落结构特征及其影响因素,采用PLFAs分析方法和高通量测序技术获得沉积物微生物量和群落结构指标,并利用冗余分析(RDA)和相关性分析等方法探究影响河流沉积物微生物量和群落结构的主要环境因素.结果表明:除上游样点C7外,沉积物细菌优势菌门均为变形菌门,次优势菌门为绿弯菌门,优势菌纲为β-变形菌纲,次优势菌纲为γ-变形菌纲;同一河段内沉积物微生物组成和细菌群落结构相似,而不同河段间沉积物微生物组成和细菌群落结构差异明显;下游沉积物细菌多样性和丰富度(香农指数均值10.20,Chao1指数均值3011.5)显著高于中游(香农指数均值9.50,Chao1指数均值2808.2)和上游(香农指数均值9.38,Chao1指数均值2681.2);沉积物微生物PLFAs总量和各菌群PLFAs含量均表现为中游沉积物中含量较高(PLFAs总量均值412.1 nmol·g~(-1)),而下游(PLFAs总量均值218.6 nmol·g~(-1))和上游(PLFAs总量均值215.1 nmol·g~(-1))沉积物中含量相对较低.分析和讨论结果表明,速效钾、pH、C/P、TC、C/N和铵态氮是影响不同河段沉积物细菌群落结构特征的主要环境因子,TC、TN、C/P和pH是影响沉积物细菌多样性的主要环境因子,而速效钾、C/P、TN、TC和pH是影响不同河段沉积物微生物量分布的主要环境因子.十五里河不同河段的沉积物微生物通过微生物量和群落结构特征反映不同河段环境状况,并发挥着水体净化和河流生态系统健康维持的功能.

Characteristics of distribution patterns of microbial biomass and community structures in the sediments from urban river

Sediment microorganisms play an important role in the geochemical cycles and transformation of pollutants and water cleaning in river ecosystems. Microbial biomass and community structures, measured by PLFAs analysis and 16S rRNA gene-based Illumina MiSeq sequencing, were investigated at different reaches in the Shiwuli River, Caohu Lake. Redundancy analysis (RDA) and correlation analysis between microbial indexes and environmental factors were conducted to explore the main driving factors affecting microbial biomass and community structures. The results showed that, except sampling site C7, the most dominant sediment bacteria along the river at phylum level were Proteobacteria and followed by Anaerolineae in all other sampling sites, while at class level Betaproteobacteria were the most dominant and followed by Gammaproteobacteria. The microbial composition and bacterial community structures in the sediments from the lower, middle and upper reaches showed significant difference, while the microbial composition and bacterial community structures in the same river reaches were similar. The diversities and richness of bacterial communities in the sediments from the lower river reaches were significantly higher than those in the middle and upper reaches (the average Shannon indices and the average Chao1 indices were 10.20 and 3011.5, 9.50 and 2808.2, 9.38 and 2681.2, respectively). The total microbial PLFAs and different group microbial PLFAs content was higher in the sediments from the middle reaches than that from the lower and upper reaches (the average total PLFAs content was 412.1, 218.6 and 215.1 nmol·g^-1, respectively). The results together showed that environmental factors including available potassium, pH, C/P, TC, C/N and ammonia-N were the main driving factors affecting bacterial community structures, among which TC, TN, C/P and pH mainly affected the bacterial diversities, while available potassium, C/P, TN, TC, TN, and pH mainly influenced the microbial biomass distribution patterns along the river. In summary, the sediment microorganism characteristics including microbial biomass and microbial community structure at different reaches along the Shiwuli River are suitable indicators reflecting the environmental conditions, and sediment microorganisms play an important role in the river water purification and ecosystem health and sustainability.