雅砻江下游浮游植物群落结构时空变化特征及环境驱动因子

Spatio-temporal Variation of Phytoplankton Community Structure and Environmental Driving Factors in Lower Reaches of Yalong River

为了解雅砻江下游浮游植物在梯级水电站运行多年后的现状,于2020年春季和秋季分别对雅砻江下游流域的22个断面进行浮游植物和环境因子采样调查,分析浮游植物群落结构时空变化特征并探究其环境驱动因子。共采集鉴定出浮游植物7门10纲20目36科72属123种(包括变种),以硅藻门、绿藻门和蓝藻门为主,其中春季物种数明显多于秋季,共有的物种有55种,干流与支流物种数接近,共有的物种有82种。全年优势种有5种,分别为硅藻门的梅尼小环藻(Cyclotella meneghiniana)、尖针杆藻(Synedra acus)、极小曲壳藻(Achnanthidium minutissima)、隐藻门的尖尾蓝隐藻(Chroomonas acuta)和蓝藻门的尖头藻(Raphidiopsis sp.),春季优势种5种,秋季优势种4种,干流优势种6种,支流优势种4种。调查期间雅砻江下游浮游植物平均丰度为3.17×10^(6)cells/L,秋季平均丰度高于春季,支流高于干流。相关分析显示:总磷(TP)、悬浮物(SS)、高锰酸盐指数(COD_(Mn))、溶解氧(DO)、透明度(SD)、水温(WT)、硝氮(NO_(3)-N)、总氮(TN)、叶绿素a (Chl.a)、电导率(EC)分别与不同浮游植物优势种呈显著的相关性。RDA结果显示:春季影响浮游植物的环境驱动因子是TN、磷酸盐(PO_(4))、WT、SD、DO,干流断面分成两部分,各支流断面明显分开;秋季影响浮游植物的环境驱动因子是WT、SD、SS。

In order to understand the current situation of phytoplankton in the lower reaches of the Yalong River after the operation of cascade hydropower stations,22 sections of the lower reaches of the Yalong River were sampled and investigated for phytoplankton and environmental factors in the spring and autumn of 2020,to analyze the spatial-temporal variation of phytoplankton community structure and explore environmental driving factors.A total of 123 species(including varieties)belonged to 7 phylum,10 classes,20 orders,36 families and 72 genera were identified.They were mainly diatom,chlorophyta and cyanophyta.The number of species in spring was significantly higher than that in autumn,and there were 55 common species.The number of species in main stream was similar to that in tributary,and there were 82 common species.There were five dominant species in the whole year,namely Cyclotella meneghiniana,Synedra acus,Achnanthidium minutissima,Chroomonas acuta and Raphidiopsis sp.There were five dominant species in spring,four in autumn,six in main stream and four in tributary.During the investigation,the average abundance of phytoplankton in the lower reaches of Yalong River was 3.17×10^(6) cells/L.The average abundance in autumn was higher than that in spring.The average abundance in four tributaries was higher than that in main stream.Correlation analysis showed that TP,SS,COD_(Mn),DO,SD,WT,NO_(3)-N,Chl.a,TN and EC were significantly correlated with different dominant phytoplankton species.RDA results showed that the environmental driving factors in spring were TN,PO_(4),WT,SD and DO.The main stream sections were divided into two parts,and the tributary sections were obviously separated.The environmental driving factors in autumn were WT,SD and SS.