西北干旱区典型水库浮游植物群落结构特征及驱动因子

为了解西北干旱区水库浮游植物群落结构特征,并进一步探究浮游植物与环境因子之间的相关关系,于2017年对张掖境内不同分布区域的8座典型水库进行为期4个季度的采样调查.结果显示,调查期间共计检出浮游植物8门106属294种,其中硅藻门、绿藻门和蓝藻门占比分别为48.35%、26.64%和14.47%.浮游植物密度在0.3×104～4.38×107cells/L之间,夏、秋季较高,冬季最低,且随着海拔的降低浮游植物密度呈现显著升高的趋势.Shannon-Wiener多样性指数、Simpson指数、Pielou均匀度指数和Margalef指数年均值分别为2.26、0.77、1.20和0.86,综合浮游植物细胞密度和物种组成对水质进行评价可知,K1、K2、K3和K5水库为贫营养,K4、K6、K7和K8水库为中营养—富营养.Spearman相关性分析和典范对应分析发现,总氮、电导率、温度和海拔是水库浮游植物密度大小及优势种分布的主要影响因子,低海拔水库中细小平裂藻(Merismopedia minima)、史密斯微囊藻(Microcystis smithii)和惠氏微囊藻(Microcystis wesenbergii)等水华蓝藻随着水温升高而占据绝对优势,尤其史密斯微囊藻密度在夏季超过水华阈值(107cells/L),值得引起注意.

Phytoplankton community structure and driving factors in typical reservoirs of arid region of northwest China

In order to explore the structural characteristics of phytoplankton community in the main reservoirs in arid climate area, northwest China, and to further study the correlation between phytoplankton and environmental factors, 8 major reservoirs in different distribution areas were surveyed for 4 quarters in 2017. The results reveled that a total 294 species belonging to 8 phyla and 106 genera were identified to be mainly composed of the Bacillariophyta, Chlorophyta and Cyanophyta and in the proportions of 48.35%, 26.64% and 14.47%, respectively. During the survey period, the density of phytoplankton was between 0.3×10⁴-4.38×10⁷ cells/L, which was higher in Summer and Autumn than in Winter and Spring, with the existence of a significant increasing trend with decreasing altitude. The Shannon-Wiener diversity index, Simpson index, Pielou evenness index, and Margalef index were 2.26, 0.77, 1.20, and 0.86, respectively. The comprehensive evaluation combining the density of phytoplankton, indicator species and four diversity indices showed that K1, K2, K3 and K5 reservoirs were oligotrophic, while K4, K6, K7 and K8 reservoirs were meso-trophic to trophic. Spearman correlation analysis of phytoplankton density and environmental factors found that phytoplankton density was extremely significantly correlated with total nitrogen (TN), electrical conductivity (Spc), and altitude, and significantly correlated with temperature, pH, and Sal. Spearman correlation analysis and CCA analysis found that TN, Spc, temperature, and altitude were the main factors influencing phytoplankton density and dominant species distribution in reservoirs. Water-blooming cyanobacteria such as Merismopedia minima, Microcystis smithii and Microcystis wesenbergii had an absolute advantage in low-altitude reservoir as temperature rise. It was worth noting that the density of Microcystis smithii increased with temperature rise and exceeded the bloom threshold (10⁷ cells/L) in Summer.