2017年夏季巢湖水华期间浮游植物与蓝藻毒素的时空变化特征

Spatiotemporal Dynamics of Phytoplankton and Cyanotoxins in Chaohu Lake During Summer Cyanobacterial Blooms of 2017

蓝藻水华暴发过程中水华物种的演替及其与蓝藻毒素的关系,对于湖泊的风险评估具有重大意义。于2017年水华暴发较为严重的夏季(6—8月)对巢湖水体的理化参数、浮游植物和蓝藻毒素进行了调查和分析。结果表明:夏季巢湖基本上处于富营养-超富营养的状态。24个样本共鉴定出浮游植物7门72属117种,以绿藻门、蓝藻门和硅藻门为主。浮游植物的群落组成和细胞密度存在明显的时空差异性,其中6月浮游植物平均细胞密度为1.35×10~8 cells/L,优势种属主要为微囊藻(Microcystis spp.,优势度为0.397)、水华长孢藻(Dolichospermum flos-aquae,优势度为0.195)和水华束丝藻(Aphanizomenon flos-aquae,优势度为0.181);7月浮游植物平均细胞密度为1.31×10~8 cells/L,优势种属主要为微囊藻(优势度为0.741)和黏伪鱼腥藻(Pseudanabaena mucicola,优势度为0.072);8月浮游植物平均细胞密度为1.01×10~8 cells/L,优势种属主要为微囊藻(优势度为0.646)。11种蓝藻毒素在夏季巢湖水体中均有不同程度的检出,其中以微囊藻毒素MC-LR、MC-RR和MC-YR为主,最高检出浓度分别为0.115、0.107、0.018μg/L。此外,分析了拟柱孢藻毒素浓度与水华束丝藻细胞密度的关系,显示两者之间存在非常显著的正相关性(P<0.01),表明水华束丝藻可能是其最主要的产毒蓝藻。11种蓝藻毒素的浓度均未超过饮用水安全标准的规定,但其潜在的安全风险依然需要密切注意。

The succession of phytoplankton during cyanobacterial blooms and its relationship with Cyanotoxins is of great significance for the risk assessment of lakes.In order to understand the scale and risk of cyanobacteria blooms in Chaohu Lake, the major physiochemical parameters,phytoplankton and cyanotoxins were studied from June to August 2017.The results showed that the water body was basically classified into the eutrophic-hypereutrophic state based on the modified trophic state index (TSIM).There were 7 phyla,72 genera and 117 species identified in 24 samples,with chlorophyta,cyanobacteria and bacillariophyta being the major phyta.There were obvious spatio-temporal differences in phytoplankton community composition and cell density.In June,the average phytoplankton density was 1.35×10^8 cells/L,the dominant species were Microcystis spp. (Y =0.397),Dolichospermum flos-aquae (Y=0.195)and Aphanizomenon flos-aquae (Y =0.181 ).In July,the average phytoplankton density was 1.31×10^8 cells/L,the dominant species were Microcystis spp.(Y=0.741)and Pseudanabaena mucicola (Y =0.072).In August,the average phytoplankton density was 1.01×10^8 cells/L and the dominant species was Microcystis spp.(Y =0.646).There were 11 different kinds of cyanotoxins detected in the water body during summer,including Microcystins (MCs),Nodularin (NOD)and Cylindrospermopsin (CYN).MC-LR,MC-RR and MC-YR'were the major cyanotoxins,and the highest concentrations were 0.115,0.107 and 0.018μg/L,respectively.In addition,the significant positive correlation between the concentration of CYN and the cell density of A.flos-aquae (P <0.01 ),showed that A.flosaquae was the major toxigenic cyanobacteria.Although the concentrations of cyanotoxins did not exceed the Guide-lines in drinking water,the potential risks should not be ignored.