阳宗海浮游植物和浮游细菌群落的空间分布特征

Spatial Distribution and Determinants of Phytoplankton and Bacterioplankton Community Structure in Yangzong Lake

浮游植物和浮游细菌在水生态系统的物质循环和能量流动中起重要作用,其分布规律及其驱动机制的识别和比较是评价水生生态系统健康的重要基础。阳宗海2008年经历了大规模的砷污染,且砷浓度目前仍处于超标水平,有必要识别砷污染水体中不同浮游生物群落分布的基本特征及其异同。通过显微镜检和聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)方法,探究阳宗海浮游植物和浮游细菌的组成及其空间分布因子。结果表明,蓝藻门在浮游植物中占绝对优势(全湖平均比例为91%),其次是甲藻门、绿藻门、金藻门、硅藻门、隐藻门和裸藻门。对DGGE条带中的DNA片段进行blast比对显示,阳宗海水体中的浮游细菌(异养细菌)主要包含放线菌纲、β-变形菌纲、α-变形菌纲和拟杆菌。PCA分析显示,浮游植物和浮游细菌群落空间分布存在差异,ANOSIM结果表明,南部和中北部的浮游植物群落存在显著差异(P<0.05,R=0.48)。多变量统计分析结果显示,空间变量和水温分别单独解释了阳宗海浮游植物群落变化的5.69%和16.51%,砷主要通过与水温和空间距离的相互作用对浮游植物的空间分布产生影响,水环境指标和空间距离与浮游细菌的空间分布没有显著关系(P>0.05)。与浮游细菌相比,浮游植物群落相似性存在显著的距离衰减关系(R2=0.61,P<0.001),可能与浮游植物扩散能力小于细菌有关。

Phytoplankton and bacterioplankton play important roles in nutrient cycling and energy flow in aquatic ecosystems.Therefore,identification and comparison of the distribution characteristics of phytoplankton and bacterioplankton communities and the determinants are important for evaluating aquatic ecosystem health.Yangzong Lake is the primary local water resource supporting agriculture and fishing and supplying drinking water,but was highly contaminated by arsenic in 2008.In this study,we investigated the spatial distribution and composition of phytoplankton and bacterioplankton communities in Yangzong Lake using light microscopy and polymerase chain reaction denaturing gradient gel electrophoresis(PCRDGGE).Important environmental factors were then identified by multivariate analysis and used to explain geographical differences in the phytoplankton and bacterioplankton communities.The aim of the study was to examine environmental heterogeneity in lake and its influence on microbial community structure in order to provide a scientific foundation for ecology restoration of contaminated lakes.Samples were collected at eight sites in Yangzong Lake during April 2013.A total of 74 phytoplankton species from 35 genera and 7 phyla were identified,dominated by Chlorophyta(24 species,14 genera)and Bacillariophyta(24 species,14 genera).Cyanophyta dominated phytoplankton biomass(91%),followed in order by Pyrrophyta,Chlorophyta,Chrysophyta,Bacillariophyta,Cryptophyta and Euglenophyta.The bacterioplankton community(heterotrophic bacteria)was mainly composed of Actinobacteria,Beta proteobacteria,Alpha proteobacteria and Bacteroidetes.Principal Component Analysis(PCA)indicated high spatial variability in the phytoplankton and bacterioplankton communities.Analysis of similarity(ANOSIM)showed a significant difference in the phytoplankton community between the south and north portions of the lake basin(P<0.05,R =0.48),but spatial difference in the bacterioplankton community was not significant(P>0.05,R=0.24).Location and water temperature significantly affected phytoplankton distribution,contributing 5.69%and 16.51%of the total variance.The spatial distribution of phytoplankton community was attributed to arsenic distribution interacting with water temperature.No significant relationships were identified between other environmental parameters and bacterioplankton community structure.Compared with the spatial distribution of the bacterioplankton community,the phytoplankton community presented a significant distance-decay relationship(R2=0.61,P<0.001),reflecting the stronger dispersion of smaller-sized bacterioplankton.