极端旱情期大型水库浮游植物群落演替特征——以新丰江水库为例

The characteristics of phytoplankton community structure and its relationship with environmental factors during extreme drought of a large-scale reservoir——Take Xinfengjiang Reservoir for example

2021年新丰江水库流域经历60年来最严重的极端旱情.为了解旱情对水库的浮游植物群落演替特征影响,2020年1月至2021年12月对新丰江水库的浮游植物群落结构和水体理化指标进行了2年调查.结果表明,旱情前(2020年)和旱情期(2021年)新丰江水库水质均达到《地表水环境质量标准》(GB3838—2002)Ⅰ类标准,2021年TLI(Σ)范围介于14~28之间,保持贫营养状态,但年度TLI(Σ)上升了19.1%.2020年和2021年分别共鉴定出浮游植物8门90属201种和8门86属191种,均以绿藻门、蓝藻门、硅藻门、裸藻门和甲藻门为主.浮游植物群落结构旱情前为蓝藻-绿藻型,旱情期为绿藻-硅藻型,2020年和2021年浮游植物丰度均值分别为1.38×10^(6)和0.41×10^(6) cells/L,受外源营养盐大幅减少的影响,旱情期藻类丰度低于旱情前,极端旱情期因降水量大幅减弱,引起水库营养盐输入量降低,从而限制了营养盐需求高的藻类增殖活动,导致藻类时间变化和组成差异.相关分析和冗余分析(RDA)结果表明,旱情前水库浮游植物的主要环境影响因子为NH3-N、WT、DO、TP和SD,旱情期主要影响因子转变为EC、WT、pH值、TN、COD_(Mn)、NH_(3)-N和SD,其中WT、SD和NH_(3)-N在旱情前和旱情期均为水库浮游植物的主要环境影响因子,说明极端旱情期由于水文和营养盐输入量变化,引起藻类主要关联因子随之变化.

In 2021,the Xinfengjiang reservoir basin experienced the extreme drought in 60 years.To understand the characteristics of the phytoplankton community structure and its relationship with environmental factors,an investigation was carried out monthly from 2020.1 to 2021.12 in Xinfengjiang Reservoir,a large-scale oligotrophic reservoir in southern China.The results showed that the water quality indexes of Xinfengjiang Reservoir basically met the‘Surface Water Environmental Quality Standard’(GB3838-2002)Ⅰduring both periods of normal and extreme drought.The values of TLI ranged from 14 to 28 in 2021,increasing about 19.1%compared to 2020,which indicated that the reservoir wasin poor nutrition state.A total of 201 phytoplankton species were identified belonging to 8 phyla and 90 genera in 2020,as well as 191 phytoplankton species were identified in 2021 belonging to 8 phyla and 86 genera.Among these species,Chlorophyta,Cyanophyta,Bacillariophyta,Euglenophyta and Pyrroptata were main compositions of the total phytoplankton species.The structure of phytoplankton community was Chlorella-Cyanophyta form in 2020,as well as Chlorella-Diatom form in 2021.The average abundance of phytoplankton were 1.38×10^(6) cells/L and 0.41×10^(6) cells/L in 2020 and 2021,respectively.As for the composition of phytoplankton abundance,the former drought was significantly different from the period of drought,which attributed that decreasing nutrient input restricted algal proliferation activities.Correlation and canonical correspondence analysis showed that water temperature,ammonia nitrogen,dissolved oxygen,total phosphorus,transparency were the key factors controlling phytoplankton community structure change in former drought,and those of water,temperature,ammonia nitrogen、conductivity、pH value、total nitrogen、Permanganate index、transparency for phytoplankton community structure during drought period in Xinfengjiang Reservoir.