广东省水库枝角类组成特征的初步研究

Cladoceran distribution in reservoirs of Guangdong Province, South China

于2000年丰水期和枯水期调查了广东省19座典型大中型水库枝角类,随后对其中3座代表性水库进行了4年的枝角类种类定性调查．在鉴定出的枝角类16属24种中有13个广温种、7个嗜暖种、3个嗜寒种和1个特有种；每个水库的平均种类数5-6种．从个体大小来看,水库枝角类以小个体种类为主,有14种的体长小于1mm,它们分布广且数量多,其中优势种主要为长额象鼻溞、秀体溞、微型裸腹溞、颈沟基合溞和角突网纹溞等．透明溞和透明薄皮溞是主要的大个体种类,出现在4座贫、中营养水库的水样中．水库枝角类的丰度较低,在丰水期,平均丰度小于10ind．/L和10-20ind．/L的水库分别为14座和5座,在枯水期,为12座和5座,而高州水库和河溪水库中的平均丰度达67 ind．/L．主要优势种在不同营养类型水库中分布差别不大．枝角类的丰度受水力滞留时间影响,直流型水库的枝角类种群丰度的分布明显受到水流速度的影响,湖泊区枝角类个体及其食物均随水库放水输出而减少．由于采样点主要位于大坝附近,枝角类以敞水区的种类为主．从种类组成和数量来看,广东省水库枝角类具有明显的热带特点,枝角类的生物量小,以个体较小的种类优势种,大型种类的个体数量极低且身体透明．

Cladocerans in 19 reservoirs of Guangdong Province, South China were investigated in 2000. Among them, 3 typical with different retention time were sampled in the later 4 years. As a result, 24 species in 16 genera were identified, including 13 eurythermal species, 7 thermophilic species, 3 psychrophilic species and 1 endemic species. There are 5 or 6 species on average in an individual reservoir. The majority of the species were composed of small-bodied species that were abundant and dominant over large-bodied species. These small sized species had a body length less than 1 mm. Small-bodied species such as Bosmina longirostris, Bominopsis deitersi, Diaphanosoma brachyurum, Diaphanosom birger, Ceriodaphnia cornuta and Moina micura were the dominant species. They occurred in all reservoirs less regarding of reservoir trophic states. Among large-bodied species, only Daphnia hya- line and Leptodora kindti can be found frequently in several oligotrophic or mesotrophic reservoirs. The average abundance of cladocerans was very low. In flood season, the average abundance was less than 10 ind./L in 14 investigated reservoirs, and ranged from 10 to 20 ind./L in 5 reservoirs. In dry season, the average abundance was less than lO ind./L in 12 reservoirs, between lO ind./L and 20 ind./L in 5 reservoirs, but reach 67 ind./L in 2 reservoirs： Gaozhou Reservior and Hexi Reservoir. Because of the difference in food quality and quantity of zooplankton, the species composition and population abundance of cladocerans in reservoirs at different trophic states are different to some extent, however, the dominant species were almost the same in these reservoirs. The cladoceran＇ s abundances were related to water retention time in the investigated. The abundance of cladocerans and their food concentration were significantly affected by flushing in the flow-through reservoirs. As most sampling sites are located near dams, the species are mainly contributed by the pelagic group and the composition of species has a typical structure of tropical zooplankton. Cladocerans are dominated by small-sized species; the large sized species have a transparent body that is helpful to survive in high predation in tropical/subtropical reservoirs.