Structure and seasonality variations of zooplankton community in the pelagic zone of tropical Dashahe Reservoir, Guangdong, South China

Abstract

于20122013年对大沙河水库敞水区的浮游动物群落及环境因子进行监测,分析和探讨大沙河水库浮游动物群落结构的变化. 2年共采集到后生浮游动物44种,其中桡足类5种、枝角类9种、轮虫30种. 浮游动物种类组成季节变化较小,存在较多的常见种. 2012、2013年浮游动物总生物量的年际波动范围分别为210.1～2560.5、512.7～3145.6 μg/L,2012、2013年枝角类是浮游动物生物量的优势类群,分别占总生物量的45.5%、51.5%;其次是桡足类,分别占总生物量的31%、40%. 枝角类的丰度和生物量与轮虫的丰度和生物量没有显著相关性,反映了它们之间的竞争强度较弱. 2012与2013年的浮游动物总生物量不存在显著差异,但群落结构差异较大. 2012与2013年对应月份的群落平均距离为0.61(SD=0.18), 反映群落结构在季节变化上存在较大的随机性. 浮游动物总丰度和总生物量存在较为明显的季节性变化:枯水期显著高于丰水期. 群落组成与环境变量之间的RDA分析表明,由季风降水导致的水文变化是影响群落结构变化和产生随机性的关键要素.;To investigate the composition and seasonal dynamic of the zooplankton communities in tropical reservoirs, environmental variables and zooplankton communities in the pelagic zone of Dashahe Reservoir (Guangdong, South China) were monthly investigated from January of 2012 to December of 2013. In total, 44 species of zooplankton were recorded, including 5 in Copepoda, 9 in Cladocera and 30 in Rotifera. The species composition of zooplankton showed a weak seasonal change, due to many common species between seasons. The fluctuation range of the zooplankton total biomass in 2012 and 2013 were 210.1-2560.5 μg/L and 512.7-3145.6 μg/L, respectively. Cladocera dominated the zooplankton in biomass and accounted for 45.5% in 2012 and 51.5% in 2013. Copepoda represented 31% and 40% of the total biomass in 2012 and 2013, respectively. Cladocera was not significantly correlated with Rotifera in abundance and biomass, indicating a low competition relationship. The total biomass of zooplankton in two years had no significant difference, but the community structures were quite different. The averaged community distance (Bray-Curtis) of month pairs between 2012 and 2013 was low (0.61 with a standard deviation of 0.18) indicated a strong randomness in dynamic of community structure. The total abundance and biomass of zooplankton showed a significant seasonality just following hydrological dynamics, and were higher in the dry period. Redundancy analysis of the zooplankton community and environmental variables demonstrated that food abundance did not explain much of the variation of the zooplankton community, but temperature and water transparency caused by hydrological changed are strongly related to the variation and randomness of zooplankton community composition.