珠江河口咸潮期间浮游植物的群落特征

根据2007年底至2008年初珠江河口咸潮入侵期间大潮和小潮的两次调查资料, 对浮游植物的种类组成、种数和细胞密度的分布等群落特征进行了分析, 并探讨环境因素对浮游植物群落的影响。共鉴定浮游植物76种, 包括38种硅藻、18种绿藻、14种甲藻、4种蓝藻和2种裸藻。浮游植物种数分布有明显的空间变化, 一般从河口上段至下段种数减少; 大潮时浮游植物的种数低于小潮时, 并且各水层之间浮游植物种数分布不均匀。优势种以淡水硅藻为主, 如颗粒直链藻Melosira granulata、颗粒直链藻最窄变种 Melosira granulata v. angustissima、小环藻 Cyclotella sp.和海链藻Thalassiosira sp.等; 河口上段的站优势种突出, 密度分布不均匀, 均匀度值比较低。大潮和小潮期间浮游植物细胞密度的平均值分别为53.80×104个.L-1和62.21×104个.L-1, 变化范围为(1.48— 290.41)×104个-L-1和(1.52—283.62)×104个.L-1; 二者的平面分布趋势基本相同, 由河口上段至下段呈递减的格局; 硅藻类的细胞密度占明显优势。浮游植物的种类组成、种数和细胞密度的分布受盐度、营养盐等环境因子的影响, 并且具有明显的潮周期性。

Characteristics of phytoplankton community in the Pearl River Estuary during saline water intrusion period

The authors analyzed species composition, distribution of species richness and phytoplankton density based on the data collected from two cruises carried out during saline water intrusion period from the end of 2007 to the beginning of 2008 at both spring and neap tides in the Pearl River Estuary. In addition, influence of environmental factors on phytoplankton community was discussed. Seventy-six species in total were identified, including 38 diatoms, 18 green algae, 14 dinoflagel-lates, 4 cyanobacteria and 2 euglenas. In general, the distribution of species richness decreased from inner section to outer section of the Pearl River Estuary. The species richness of phytoplankton was higher at neap tide than at spring tide, and it distributed unevenly among different water layers. The dominant species were mainly freshwater diatoms, such as Melosira granulate, Melosira granulata v. angustissima, Cyclotella sp. and Thalassiosira sp. The dominant species were very out-standing in the inner section of the Pearl River Estuary with the characteristics of uneven density distribution and low even-ness index value. The mean phytoplankton densities at spring and neap tides were 53.80×104 and 62.21×104ind.L-1, and the ranges of cell density were from 1.48×104 to 290.41×104 and from 1.52×104 to 283.62×104ind.L-1, respectively. Phyto-plankton density decreased from the inner to outer sections of the Pearl River Estuary, and the density of diatom was the highest among different groups during both spring and neap tides. The community of phytoplankton presented clear tidal pe-riodicity. Environmental factors such as salinity and nutrients played an important role in the composition and distribution of phytoplankton during saline water intrusion period in the Pearl River Estuary.