Effect of the ingestion of metazooplankton on the formation of <i>Microcystis</i> blooms in summer in Lake Taihu

Abstract

为了了解后生浮游动物的摄食作用在太湖夏季微囊藻水华形成中的作用,2009年7月15日至8月14日取太湖梅梁湾湖水开展了后生浮游动物对微囊藻水华形成作用的野外模拟实验.实验期间,未过滤掉后生浮游动物的对照组出现了漂浮在水面、肉眼可见的微囊藻水华,而过滤掉后生浮游动物的实验组没有出现微囊藻水华.结果显示,对照组整个实验期间都有后生浮游动物存在,共发现了9种后生浮游动物;而实验组在实验第6 d发现有后生浮游动物出现,整个实验期间共发现了3种后生浮游动物.浮游动物生物多样性分析显示对照组显著高于实验组.实验后期(21~30 d),对照组微囊藻平均密度显著高于实验组.整个实验期间,惠氏微囊藻(Microcystis wesenbergii)和水华微囊藻(Microcystis flos-aquae)密度均显著高于实验组,且惠氏微囊藻密度占对照组微囊藻总密度的60.79%.研究结果表明,太湖夏季后生浮游动物摄食并不能控制太湖蓝藻水华,相反,后生浮游动物特别是大型浮游动物能促进蓝藻水华的形成.同时表明,后生浮游动物群落结构可能是影响微囊藻水华形成的重要因素.;In order to understand the effects of the ingestion of metazooplankton on the formation of Microcystis blooms in summer in Lake Taihu,a field simulation experiment had been carried out by taking water samples from the Meiliang Bay in Lake Taihu from July 15 to August 14,2009.During the period,visible Microcystis blooms floating on the water surface were found in the controls which did not filter out metazooplankton,but Microcystis blooms were not found in the treatments which had filtered out metazooplankton.Nine species of metazooplankton were found in the controls and three species of metazooplankton in the treatments during the whole experiment.Metazooplankton were found in the treatments in the sixth days of the experiment.The zooplankton biodiversity (H) analysis showed that the value of H in the controls was significantly higher than that in the treatments.During the later stage of experiment (21-30 days),the average density of Microcystis spp.in the controls was significantly higher than those in the treatments.During the experiment,the density of Microcystis wesenbergii and Microcystis flos-aquae in the controls were significantly higher than those in the treatments,and Microcystis wesenbergii contributed 60.79% of the total Microcystis abundance in the controls.The results showed that the ingestion of metazooplankton could not control the Microcystis blooms,on the contrary,metazoop-lankton,especially large metazooplankton,promoted the formation of Microcystis blooms.The experiment also suggested that the community structure of metazooplankton was an important factor in affecting the formation of Microcystis blooms.