珠江流域浮游植物群落特征及驱动因素

Community Characteristics and Driving Factors in the Pearl River Basin

浮游植物常用于水生态监测及健康评价,珠江流域为典型的亚热带湿润区,水系组成复杂,沿程海拔落差较大,主要为山区性河流,目前尚未有对整个流域浮游植物的分布及环境效应的研究。为探究珠江流域浮游植物的种群结构及其与环境因子的关系,本文于2022年4−7月对珠江流域的西江水系、北江水系、东江水系的浮游植物及水体理化参数进行调查与分析。结果表明:①调查期间珠江流域共检出浮游植物8门79属204种,浮游植物平均密度为6.78×10^(5) cells/L,以硅藻门为主,绿藻门次之。②珠江流域浮游植物优势种主要为卵圆隐藻、啮蚀隐藻、小环藻、菱形藻、科曼小环藻、舟形藻,浮游植物Shannon-Wiener多样性指数表现为北江水系>西江水系>东江水系,平均值为3.81。③主成分分析(PCA)结果表明,氮磷污染主要在珠江-西江上游及东江下游水域,TN浓度、TP浓度、浊度(TUR)、五日生化需氧量(BOD5)、高锰酸盐指数(CODMn)、化学需氧量(COD)是影响珠江流域浮游植物群落结构特征的主要因素。④冗余分析(RDA)结果表明,pH、水温(WT)、DO浓度是影响珠江流域浮游植物种群结构的重要因子。研究显示,珠江流域浮游植物整体组成为硅藻-绿藻型,其中东江水系为绿藻型,西江水系为硅藻-蓝藻型,北江水系为蓝藻-硅藻型。珠江流域整体为中营养型状态,北江水系已基本形成连续型水库群特征,连通性受到严重阻隔,流速缓慢,导致河流富营养化加剧,存在水华现象发生的风险。

Planktonic plants are commonly used for aquatic ecological monitoring and health assessment,the Pearl River Basin is a typical subtropical humid area,features a complex water system with a significant altitude drop.It is mainly mountainous rivers.Currently,there is no research on the distribution of phytoplankton and environmental impacts in the whole basin.In order to explore the population structure of phytoplankton in the Pearl River Basin,its relationship with environmental factors,and to evaluate the water quality,this paper investigates and analyzes the phytoplankton and the physicochemical parameters of water in the Xijiang River,Beijiang River and Dongjiang River in the Pearl River Basin from April to July 2022.The results show that:(1)A total of 204 phytoplankton species belonging to 79 genera and 8 phyla were detected in the Pearl River Basin,with an average density of 6.78×105 cells/L,mainly composed of Bacillariophyta.(2)The dominant species were Cryptomons ovata,Cryptomonas erosa,Cyclotella,Nitzschia,Cyclotella comensis and Navicula.The average Shannon-Wiener diversity index of phytoplankton was 3.81,ranking as Beijiang River based>Xijiang River based>Dongjiang River,which is‘excellent’.(3)Principal component analysis(PCA)showed that the distribution of phytoplankton community in the Pearl River Basin was significantly affected by the physical and chemical factors of the water body,and there was nitrogen and phosphorus pollution in the source area of the Pearl River and some river sections of the Dongjiang River.TP,TN,turbidity,BOD5,CODMn and COD were the main factors affecting phytoplankton community structure in the Pearl River Basin.(4)Redundancy analysis(RDA)indicated that pH,water temperature and dissolved oxygen are important factors affecting the population structure of phytoplankton in the Pearl River Basin.The research shows that the overall composition of phytoplankton in the Pearl River Basin is dominated by Bacillariophyta and Chlorophyta.The Dongjiang River is Chlorophyta type,the Xijiang River is of the Bacillariophyta-Cyanophyta type,and the Beijiang River is Cyanophyta-Bacillariophyta type.The Pearl River Basin is generally mesotrophic,and the main stream and tributaries of the Beijiang River have basically formed a continuous reservoir group,with serious connectivity obstruction and slow flow rate,leading to increased eutrophication of the river and the risk of water bloom.