一座南亚热带小型贫营养水库浮游植物群落结构及季节变化

库容大小是影响水体水动力学过程的一个重要变量,它能在很大程度决定生态系统的结构,特别是浮游植物的群落结构.为了解小型贫营养水库浮游植物的群落特点,于2006年4、8、12月对位珠海市的贫营养小型水库-吉大水库的浮游植物群落结构进行采样和计数分析.3次采样共检出浮游植物32种,浮游植物细胞丰度的变化范围在69～342 cells·mL^-1,生物量的变化范围在1.34～3.69 mg·L^-1,夏季浮游植物的丰度和生物量明显高于冬季.甲藻是最主要的优势种类,且相对优势度较为稳定.夏季,隐藻门的隐藻(Cryptomonas sp.)和绿藻门的鼓藻(Cosmarium spp.)大量出现,甲藻的相对优势度有所降低.冬季,隐藻数量急剧下降,但硅藻门的颗粒直链藻(Aulacoseira granulata)大量出现,与甲藻共同成为水体中的优势种.由降雨引起的营养盐浓度增加是浮游植物变化的主要影响因子,而透明度全年维持较高的水平为浮游植物的生长形成了有利条件,此外,较为稳定的水体和甲藻利用营养盐的能力使得甲藻成为浮游植物中的最主要的优势种.

Dynamics and structure of the phytoplankton community of a small oligotrophic reservoir in southern China

Due to the difference in water volume,seasonal dynamics and structure of the phytoplankton community in small reservoirs are distinct from those in large reservoirs.To understand the composition and dynamics of the phytoplankton community in small reservoirs,we investigated a typical small oligotrophic reservoir located in southern China,Gida Reservoirs,in April,August and December,2006.The concentrations of TN,TP were low in this reservoir.32 taxa of phytoplankton were,in total,identified from 3 samplings.The abundance of phytoplankton ranged from 69 to 342cells·mL^-1,and the biomass of phytoplankton ranged from 1.34 mg·L^-1 to 3.69 mg·L^-1.Cells abundance and biomass of phytoplankton in the summer were higher than in winter and spring.Peridinium sp.was the first dominant group of biomass and abundance in the phytoplankton community.In the summer,the abundance of Cryptomonas sp.and Cosmarium spp.increased and became the dominant species.In the winter,phytoplankton abundance and biomass decreased significantly.Cryptomonas sp.was out of the samples,and Aulacoseira granulate,following Peridinium sp.,became one of the dominant species.As a small reservoir with a small catchments,the thermal structure is stable for a whole year,and rainfall functions the main source of nutrients.The thermal stability favors Peridinium to be the dominant species,and precipitation is the principle driving force for the seasonal dynamics of the phytoplankton community.