千岛湖浮游动物的群落结构

Community Structure of Zooplankton in Lake Qiandaohu

研究了贫 -中营养型的大型、深水湖泊——浙江千岛湖浮游动物的群落结构 ,包括种类组成、种群动态、现存量及群落多样性指数。在 1 a的研究中 ,共发现 1 39种浮游动物 ( 2 7种原生动物、70种轮虫、2 6种枝角类和 1 6种桡足类 )。根据年平均密度 ,各类浮游动物的优势种分别为褶累枝虫 ( Epistylis plicatilie)、螺形龟甲轮虫 ( Keratella cochlearis)、透明( Daphnia hyalina)和一种中剑水蚤 ( Mesocyclopsnotius)。轮虫和枝角类群落多样性指数随着水体透明度的增大呈下降的趋势 ;采样站变异下 ,枝角类群落多样性指数与其种类数和密度呈显著的正相关关系 ;月份变异下 ,桡足类群落多样性指数与其密度呈显著的正相关关系。

Lake Qiandaohu, Zhejiang is a large and deep lake in the middle and lower reaches of the Changjiang River, China. We made a survey on the species composition, density, biomass and diversity index of zooplankton in Lake Qiandaohu. Zooplankton samples were taken at monthly interval from ten stations from January-December 1999. At each station, two kinds of samples were taken, one for identifying species and the other for determining abundance of zooplankton. The frist kind of sample was the mixture of five subsamples collected from the surface to the depth of twice transparency at an equal interval, and 10L of lake water was strained through a plankton net with a mesh size of 64μm. The sample were fixed with Lugol's solution. The wet biomass of Protozoa and Rotifera was estimated by using geometric figures of their approximate shapes, and the wet biomass of Cladocera and Copepoda was estimated by the equations of weight vis-a-vis length. Diversity index was calculated according to Shannon-Wiever's formula. Totally, 139 species of zooplankton ( 27 Protozoa, 70 Rotifera, 26 Cladocera and 16 Copepoda ) were found. In terms of annual average density, the dominant zooplankton were Epistylis plicatilie , Keratella cochlearis, Daphnia hyalina and Mesocyclops notius. Among the four groups of zooplankton, Protozoa had the highest density (125ind./L), Cladocera had the highest biomass (1.433mg/L), and Rotifera had the highest diversity index (2.03). The highest peak of total zooplankton density occurred in May^July (864ind./L), of which Protozoa and Rotifera comprised the majority. Station II had the highest density ( 804ind./L). Monthly changes of zooplankton biomass presented a “sawtooth” shape with a maximum value of 4.167mg/L in May; The higher zooplankton biomass was at Stations II and X (3.112mg/L and 2.999mg/L, respectively). The diversity indices of Copepoda had a positive linear relationship with its density, and Cladocera diversity indices showed a positive linear relationship with its species number and density. With an increase in transparency, the community diversity indices of Rotifera and Cladocera showed a decline. The characteristics of zooplankton in Lake Qiandaohu were rich Rotifera species number and poor Protozoa. The correlation coefficient reached 0.988 between Cladocera and total zooplankton biomass. Most Copepoda species were only occasionally observed. It appears that although there were as many as 139 species of zooplankton in Lake Qiandaohu, the dominants was limited to a few genus or a few species, including a few indicator species in olig-saprobic water body, such as Difflugia spp.,Tintinnopsis spp., Diaphanosoma brachyurum, Leptodora kindti.