The Study On The Community Structure And The Variation Of Population Quantity In Dianchi Lake

The community structure, the monthly variation of population quantity and the relationship with enviromental factors of zooplankton in Dianchi Lake were studied in this paper. From April 2009 to March 2010, 78 species of zooplankton was identified, among which there were 21 Protozoan species in 19 genera, 34 Rotifer species in 18 genera, 9 Cladocera species in 14 genera and 8 Copepoda species in 9 genera.23 normal species of zooplankton were found, which included 5 Protozoan species, 12 Rotifer species, 3 Cladocera species and 3 Copepoda species. Protozoan included Difflugia globulosa, Actinophrys sol, Vorticella microstoma, Strobilidium velox and Tintinnopsis wangi; Rotifer included Rotaria neptunia, Brachionus angularis, Brachionus calyciflorus, Brachionus forficula, Keratella cochlearis, Keratella valga, Monostyla closterocerca, Asplanchna priodonta, Diuralla stylata, Trichocerca capucina, Polyarthra trigla and Filinia maior; Cladocera included Daphnia cucullata, Bosmina longirostris and Chydorus sphaericus; Copepoda included Eucyclops serrulatus, Mesocyclops leuckarti and Thermocyclops taihokuensis.Keratella was the primary dominant genus in Dianchi Lake. And the dominant genus of zooplankton was Bosmina in June, Monostyla and Branchionus in July, Polyarthra and Chydorus in December, Daphnia in Junuary.The average quantity of zooplankton was 1.79×103ind./L during the study time. The highest quantity of zooplankton was 3.65×103ind./L in July, 2009, and the lowest quantity of zooplankton was 543ind./L in February, 2010. Abundance was the highest in summer, successively in autumn and winter, the least in spring. The locations near the lakeshore have more zooplankton than the locations in center. Seasonal fluctuation of abundance and biomass was closed in 12 locations.The highest temperature of water was 23.0℃in August 2009, and the lowest temperature of water was 12.0℃in January 2010. The maximum transparency of lake water was 44.25cm in August 2009, and the minimum transparency of lake water was 25.33cm in April 2009. From October 2009 to March 2010 have more total nitrogen and total phosphorus content of water than from April 2009 to September 2009. The highest Chlorophyll a content in May 2009, and the lowest in February 2010.The quantity of zooplankton had a relationship with the water temperature, and with the rise of the temperature, the quantity of zooplankton increased. The correlation between abundance and total nitrogen, and total phosphorus, and Chlorophyll a were unobvious in Dianchi Lake.