横岗水库浮游植物种类组成与时空分布

Species composition and spatio-temporal distribution of phytoplankton in Henggang Reservoir

于2005年5月和11月调查了横岗水库的水质和浮游植物,对浮游植物群落结构进行了分析。两次采样期间,浮游植物群落数量组成与种类结构发生明显变化。5月份浮游植物平均细胞数量高达275.41×106cells?L-1,平均生物量为31.07mg?L-1;其中优美平裂藻(Oscillatoria.elegans)和银灰平列藻(Oscillatoria.glauca)为绝对优势种,占总细胞数的90%;平裂藻的大量出现导致浮游植物生物量由球体等效半径在10～20μm的种类占主导,但0～5μm区间的小型藻类仍维持较高的生物量。11月份,浮游植物平均细胞数量降低到12.69×106cells?L-1,平均生物量为20.78mg?L-1。蓝藻门有16种,优美平裂藻、银灰平列藻的优势度明显下降;绿藻种类数量增加到48种,在新出现的25个种类中,鼓藻科(Desmidiaceae)、盘星藻属(Pediastrum)和栅藻属(Scenedesmus)有较高的细胞数;优势种类没有变化;大细胞种类的生物量明显增加,特别是等效半径大于20μm的种类。整体上看,浮游植物数量和生物量从河流入水口到大坝处有递减趋势,这种趋势在11月份更为明显,这与采样时期水库水动力过程的梯度相一致。

In May and Nov 2005, the water quality and phytoplankton in a eutrophic reservoir, Henggang Reservoir, were investigated to analyze the species composition and abundance distribution of phytoplankton. In May, the average abundance of phytoplankton was 275.41×106cells·L^-1, and the average biomass of phytoplankton was 31.07mg·L^-1. Merismopedia elgans and Merismopedia glauca were the only two dominant species, contributed over 90% of total phytoplankton abundance. In November, the composition of phytoplankton community had a significant change. The average abundance of phytoplankton decreased to 12.69 ×10^6cells·L^-1, and the average biomass was 20.78 mg·L^-1. In the observed 16 species of Cyanophyta, the abundance of Merismopedia elgans and Merismopedia glauca decreased largely. Desmidiaceae, Pediastrum, Scenedesmus had high abundance, and the species numbers of Chiorophyta increased to 48. The biomass of large sized phytoplankton increased largely, especially the species which equivalent radiuses were over 20μm. In the November, the phytoplankton and nutrients were diluted with the increase in stored water. The seasonal change in precipitation caused by monsoon was the main physical factor affecting phytoplankton community in Henggang reservoir.