2002—2017年千岛湖浮游植物群落结构变化及其影响因素

Long-term variation of phytoplankton community and driving factors in Qiandaohu Reservoir,southeast China

为认识大型水库中浮游植物群落结构的演替特征及其驱动机制,以钱塘江流域新安江水库(下称"千岛湖")为例,基于2002-2017年16年的水库浮游植物数据,结合同期千岛湖水质与水文气象资料,分析了千岛湖浮游植物结构及优势属的长期变化特征,探讨了影响浮游植物群落结构变化的主要因素.结果表明:2002-2017年千岛湖共鉴定出浮游植物7门93属,主要由硅藻门、绿藻门、蓝藻门及隐藻门种类组成.16年间,浮游植物年均丰度和群落结构经历了4个阶段:2008年前丰度持续低值且蓝藻不是主要类群,2009-2012年丰度较高且蓝藻成为主要类群,及2013-2015丰度降低且蓝藻占比降低,2016-2017年丰度增加且蓝藻再次成为主要类群.浮游植物门类变化的同时伴随着优势属的变化:浮游植物年优势属从2002-2008年的小环藻属(Cyclotella)、隐藻属(Cryptomonas)和蓝隐藻属(Chroomonas)转变为2009-2012年的颤藻属(Oscillatoria)、小球藻属(Chlorella)、小环藻属和蓝隐藻属,2013-2017年又转变为鱼腥藻属(Anabaena)、束丝藻属(Aphanizomenon)、小环藻属、针杆藻属(Synedra)、直链藻属(Melosira)、栅藻属(Scenedesmus)和蓝隐藻属.冗余分析表明,气温、风速、水位、入库流量等气象水文因子和总氮浓度、电导率、氮磷比、透明度等水质因子与浮游植物群落结构变化关系密切.研究结果表明,在千岛湖这种大型贫-中营养水库,浮游植物群落结构不仅受来水营养盐负荷的影响,还在很大程度上受水文、气象条件的影响,给水库藻类水华等生态风险的预测以及水库水质管理带来了挑战.

To understand the succession characteristics and driving mechanism of phytoplankton community structure in large reservoirs,the Xin'anjiang Reservoir (Qiandaohu Reservoir) in Qiantang River Basin was chosen as the case study.From 2002 to 2017,the surveyed phytoplankton data,physicochemical variables and hydro-meteorological conditions were investigated to understand long-term variations of phytoplankton community and dominant genus,therefore to discover the main factors driving changes of phytoplankton community structure.The results showed that from 2002 to 2017,7 phyla including 93 genera of phytoplankton were existed in Qiandaohu Reservoir,which were mainly composed of Bacillariophyta,Chlorophyta,Cyanophyta and Cryptophyta.In the past 16 years,annual abundance and community structure of phytoplankton experienced four stages: before 2008,the abundance of phytoplankton cell maintained at a low level and cyanobacteria was not the main group.During 2009 and 2012,the cell abundance of phytoplankton was at a high level with cyanobacteria becoming the main group.The cell abundance of phytoplankton and proportion of Cyanophyta decreased during 2013 and 2015.Phytoplankton cell abundance increased during 2016 and 2017 with cyanobacteria becoming the main group again.When the phytoplankton changed,the dominant genus also changed.The phytoplankton dominant genus were Cyclotella,Cryptomonas and Chroomonas from 2002 to 2008,then changed to Oscillatoria,Chlorella,Cyclotella and Chroomonas during 2009 and 2012,and turned Anabaena,Aphanizomenon,Cyclotella,Synedra,Melosira,Scenedesmus and Chroomonas during 2013 and 2017 at last.RDA analysis showed that hydro-meteorological factors such as temperature,wind speed,water level and inflow,and water quality factors such as total nitrogen,conductivity,nitrogen-phosphorus ratio and transparency were significantly related to phytoplankton community structure.The results show that in oligotrophic and mesotrophic reservoirs such as Qiandaohu Reservoir,the phytoplankton community structure was not only affected by the nutrients,but also strongly affected by hydro-meteorological conditions.This complex relationship poses a giant challenge to the ecological risks prediction of reservoir algal blooms and water quality management.