Dynamic changes of microcystins and phytoplankton during the cyanobacterial bloom in Lake Erhai in 2013

Abstract

2013年秋季,洱海再次出现大规模水华,周边几十万居民的饮用水安全引起当地政府的极大关注. 为了解水华发生期间洱海水体微囊藻毒素的含量和浮游植物的种类及丰度,分别在2013年9月和10月两次在洱海采集水样,测定其中两种主要微囊藻毒素MC-LR和MC-RR含量,探讨微囊藻毒素含量对洱海周边水源地的安全影响. 同时也对水华期间的浮游植物特别是蓝藻进行研究,从而分析微囊藻毒素与浮游植物种类和丰度的关系. 结果表明,洱海水体中微囊藻毒素含量偏低,暂不会对人类健康产生威胁,但在洱海的水鸟体内仍然检测到微囊藻毒素的富集,显示洱海蓝藻水华对水生生物的潜在危害不容忽视. 浮游植物的研究发现,洱海水华的优势种属为微囊藻(Microcystis)和暗丝藻(Psephonema aenigmaticus).9月份暗丝藻更占优势,10月份则是微囊藻更占优势. 研究结果显示处于富营养化初期的洱海水体中湖湾微囊藻毒素的含量与浮游植物中产毒蓝藻的种类和丰度密切相关.;In the autumn of 2013, a cyanobacterial bloom outbreak happened again in Lake Erhai, which caused huge public outcry and concern of the local government.In order to characterize the variations in microcystins concentrations, phytoplankton composition and density during a cyanobacterial outbreak and to evaluate the impact of microcystins on the safety of water source, a large-scale survey across the lake was conducted in September and October of 2013.Results indicated that microcystins were detected in all samples although the concentrations were low compared with those of Lake Taihu or Lake Chaohu.Both the intracellular and extracellular MCs concentrations were far less than the standards recommended by WHO (<1 μg/L), suggesting Lake Erhai as a water source for Dali City is relatively safe.However, we still found the microcystins accumulation in the body of aquatic birds in the lake.During the study period, 39 genera phytoplankton belonging to 6 phyla were recorded, with microcystins (Cyanophyta) and Psephonema aenigmaticus (Chlorophyta) as the dominant genera(species).In September, the abundance of P.aenigmaticus was more than that of Microcystis, while the situation was opposite in October.The composition and abundance of toxin-producing cyanobacteria have impacts on the concentrations of microcystins in the bay.