水化学指标和空间距离对乐安江浮游细菌群落的影响

Effects of hydrochemical parameter and spatial distance on bacterioplankton community in the Le′an River

为了解乐安江水体浮游细菌群落特征,探讨水化学指标和空间距离对浮游细菌群落的影响,本研究分别于枯水期(2016年12月)和丰水期(2017年7月)对乐安江15个采样点表层水样进行采集.检测了水体NO^-_3-N、 NH^+_4-N、 TP、 DOC、 SO■、 Cl^-、 Cu、 Zn等水化学指标,运用高通量测序技术确定水体浮游细菌群落特征,Mantel Test分析了水化学指标、空间距离(采样点干流长度、平均河网长度、累计河网长度和流域子面积)与细菌群落之间的关系.结果表明:①乐安江水体浮游细菌群落丰富度和多样性丰水期均高于枯水期,丰富度随流向逐渐升高,多样性下游最高,中游最低.②枯水期丰度最高的细菌门类是Proteobacteria,其次是Bacteroidetes和Actinobacteria,枯水期Proteobacteria中下游显著高于上游,Bacteroidetes中下游显著低于上游,Actinobacteria上游显著高于中下游.丰水期丰度最高的细菌门类是Actinobacteria,其次是Proteobacteria和Cyanobacteria,丰水期Actinobacteria丰度先降低后升高,中游丰度显著低于下游,其他河段无显著差异,Proteobacteria丰度随流向逐渐降低,Cyanobacteria丰度中游最高,并且显著高于下游地区.③非淡水细菌占所有细菌丰度的比例沿流向逐渐增加,丰水期均值(62.94%)显著高于枯水期(49.33%).④NO^-_3-N是与浮游细菌群落相关性最高的水化学指标,干流长度是与浮游细菌群落相关性最高的空间距离指标.⑤水化学指标和空间距离与乐安江浮游细菌群落都有显著相关性,并且水化学指标对浮游细菌群落的影响要高于空间距离.本研究为鄱阳湖和乐安江流域水生态环境保护提供了科学依据.

To explore the characteristics of the bacterioplankton and effects of hydrochemistry and space distance on the bacterioplankton community, we collected surface water samples from 15 sampling sites in the Le′an River in the dry season(December 2016) and the wet season(July 2017). We tested the concentrations of NO^3--N, NH4^+-N, TP, DOC, SO4^2-, Cl^-, Cu, Zn and other hydrochemical parameters, and determined the characteristics of the bacterioplankton community using high-throughput sequencing technology. We analyzed the relationships between hydrochemical parameter, spatial distance(mainstream length, average river network length, cumulative river network length and basin area of sampling sites) and bacterioplankton community by Mantel Test. The results showed that:①The bacterioplankton community′s richness and diversity in the Le′an River were higher in the wet season than in the dry season. The richness increased along the flow direction, and the diversity was the highest in the lower reaches and the lowest in the middle reaches.②The highest abundance of bacterioplankton phylum in the dry season was Proteobacteria, followed by Bacteroidetes and Actinobacteria. The abundance of Proteobacteria in the middle and lower reaches was significantly higher than in the upper reaches;the abundance of Bacteroidetes in the middle and lower reaches was significantly lower than in the upper reaches;and the abundance of Actinobacteria in the upper reaches was no significantly higher than in the middle and lower reaches. The highest abundance of bacterioplankton community in the wet season was Actinobacteria, followed by Proteobacteria and Cyanobacteria. The abundance of Actinobacteria first decreased and then increased along the flow direction and was significantly lower in the middle reaches than in the lower reaches. The abundance of Proteobacteria gradually decreased along the flow direction. The abundance of Cyanobacteria in the middle reaches was the highest, and was significantly higher than in the lower reaches.③The proportion of the non-freshwater bacteria increased gradually along the flow direction, and the proportion in the wet season(62.94%) was significantly higher than in the dry season(49.33%).④NO3^--N was the best parameter in the hydrochemical parameters explaining the dynamics of bacterioplankton community, and the mainstream length was the best parameter in the spatial distance variables.⑤Both the hydrochemical parameter and the spatial distance significantly affected the distribution of bacterioplankton community in the Le′an River, and the influence of water chemistry was higher than that of the spatial distance. This study provides a scientific basis for the water ecological environment protection in the Le′an River Basin and Poyang Lake.