长江口浮游植物群落结构的特征

研究了长江口南、北支浮游植物的空间分布特征。共采集到浮游植物157种,隶属8门71属,平均细胞密度3.31×10~5个/L。其中硅藻门为主要优势类群,共25属61种,占浮游植物总种类数的39%。主要优势种为蓝藻门的湖泊鞘丝藻,常见种为蓝藻门的阿氏颤藻、两栖颤藻、小颤藻、绿藻门的小球藻,以及硅藻门的中肋骨条藻。浮游植物细胞密度在3.27×10~4～1.50×10~6个/L,南北支水域以及主河道水域没有差别。各样点的均匀度指数变化比较平稳;多样性指数变化和丰富度指数变化一致,南支水域显著高于北支和主河道水域。统计分析浮游植物与环境因子相关性显示:物种数和总细胞丰富度分别与温度、叶绿素a显著正相关,与盐度显著负相关;多样性指数和均匀度指数分别与温度、叶绿素a显著正相关,与电导率显著负相关;蓝藻细胞密度与温度显著正相关,与溶氧量、盐度显著负相关;硅藻细胞密度与电导率显著正相关,与温度显著负相关。对调查水域浮游植物种类和密度的分布影响较为显著的环境因子为盐度、电导率、溶氧量、温度和叶绿素a。因此,长江口环境因子的不同影响浮游植物群落结构的时空变化。

Ecological features of phytoplankton community in the Yangtze River Estuary

We surveyed the spatial distribution characteristics of the phytoplankton community in the Yangtze River Estuary. A total of 157 species from 71 genera were identified and the average density were 3.31×10⁵ cells/L. Bacillariophyta was the dominant group, which was 61 species of 25 genera and its species number accounted for 39% of all species. Lyngbya limnetica, Oseillatoria agardhii, Oseillatoria amphibia, Oseillatoria tenuis, Chlorella vulgaris and Skeletonema costatum were the dominant species. Phytoplankton density ranged from 3.27×10⁴ to 1.50×10⁶ cells/L and there is no difference between the north branch, south branch and the main river. The homogeneity index between the north branch and the south branch varies little. The cell abundance and diversity index of the south branch are significantly higher than those of the north branch. The correlation analysis between phytoplankton and environmental factors showed that the species of phytoplankton and cell abundance were significantly positively correlated to temperature and chlorophyll a and were significantly negatively correlated to salinity. The diversity index and homogeneity index were significantly positively correlated to temperature and chlorophyll a and were significantly negatively correlated to conductivity. The cell abundance of Cyanophyta was significantly positively correlated to temperature and was significantly negatively correlated to dissolved oxygen and salinity. The cell abundance of bacillariophyta was significantly positively correlated to conductivity and was significantly negatively correlated to temperature. The environmental factors that have a significant impact on the distribution of phytoplankton species and density in the surveyed waters are salinity, conductivity, dissolved oxygen, temperature and chlorophyll a. Therefore, the environmental factors of the Yangtze River Estuary affect the spatial and temporal changes of phytoplankton community structure.