鹤地水库浮游植物群落的结构与动态

鹤地水库位于雷州半岛北部(21°42'～22°22'N,109°54'～110°25'E),是一座中营养化的大型水库.为了研究其浮游植物群落的结构与变化特点,在水库设置5个采样点,并于2003年2、7、9、12月对其采样.鹤地水库浮游植物生物量变化为O.156～2.548 mg L~(-1),主要由蓝藻和硅藻组成.5个采样点的浮游植物生物量具有明显的季节变化,且变化趋势相同,即丰水期的生物量高于枯水期,主要是由于丰水期水温较高以及入库河水带入的营养盐.5个采样点的浮游植物生物量从主要入库河流至大坝区呈下降趋势,与磷浓度的降低直接相关.浮游植物优势种主要以热带代表性种类为主,且有明显的季节变化,枯水期主要为硅藻的根管藻(Rhizosolenia sp.)、小环藻(Cyclotella sp.)、颗粒直链藻(Melosira granulata)以及模糊直链藻(Melosira ambigua)等.丰水期为蓝藻的拟柱孢藻(Cylindrospermopsis raciborskii)、湖泊假鱼腥藻(Pseudanabaena limnetica)等,浮游植物优势种类的变化主要受磷浓度的影响.浮游植物前8个优势种的生物量占浮游植物群落生物量的850%～92%,显著低于温带地区浮游植物群落结构稳定的湖泊.

Structure and Dynamics of Phytoplankton Community in Hedi Reservoir, South China

Hedi Reservoir, located in the north of Leizhou Peninsula, is a large and mesotrophic reservoir. To understand the structure and variation of phytoplankton community in the reservoir, phytoplankton was sampled at five sites in February, July, September and December of 2003. Total phytoplankton biomass ranged from 0.156~2.548 mg L-1, mainly contributed by cyanobacteria and diatom. The structures of phytoplankton community at five sites varied markedly and seasonally from spring to winter, and the dynamic pattern of phytoplankton community was quite similar among the five sampling sites. The phytoplankton biomass in flood season was higher than that in dry season. The phytoplankton benefited from high temperature in flood season and nutrient input with inflow. Phytoplankton biomass showed a spatial gradient from riverine zone to lacustrine zone, corresponding to a decrease in phosphorus concentration. Phytoplankton species was dominated by thermophilous species in tropics, and the dominant species in dry season were markedly different from those in flood season. The dominant phytoplankton species in dry season were Rhizosolenia sp., Cyclotella sp., Melosira granulate and Melosira ambigua, while Cylindrospermopsis raciborskii, and Pseudanabaena limnetica in flood season. Phosphorus was the main factor regulating the variation of the dominant phytoplankton species in flood season. The biomass of first eight dominant species contributed 85%~92% of total biomass, significantly less than that in the temperate lakes with steady structure of phytoplankton community.