The Ecological Research On Crustacean Zooplankton Of Three Gorges Reservoir After Impoundment

The ecosystem of the Three Gorges Reservoir in Yangtze River was changed into an artificial lake (reservoir) ecosystem after impoundment in June 2003. We surveyed the seasonal variation and spatial distribution of copepods from April 2004 to January 2005 in order to provide basic data for clarifying the successional patterns of the ecosystem. From Jiangjin to Maoping, eight copepod species and nine Cladocerans species were collected. Among the copepods, Mesocyclops pehpeiensis, M. leuckarti and Sinocalanus dorrii had a relatively wide distribution. The predominant species of Cladocerans were Daphnia cucullata and Bosmina coregoni. Species composition and distribution of Crustacean zooplankton showed significant seasonal and special variation, in another word, the density and biomass in the river item were higher than the reservoir item, and the upper waters higher than in the down waters of the reservoir item; at the same time, the density and biomass were higher in spring than in summer, and much lower in autumn and in winter.28 Copepods species and 28 Cladocerans species were collected in the 13 rivers of the main bay of Three Gorges Reservior during the whole year from April 2006 to January 2007 when we did the seasonal research. Sinocalanus dorrii and M. leuckarti were dominant in copepods, and Bosminopsis deitersi and Bosmina coregoni were dominant in Cladocerans. The density and biomass of the Crustacean zooplankton showed minus correlation with the water flux of the bay. The seasonal variation showed different character between copepods and Cladocerans, which had the following phenomena: the density of Cladocerans was highest in autumn, while in summer it was highest for copepods. The diversity index of Cladocerans and copepods was rather low in the bay of the reservoir, which was involved with the faultiness ecosystem for the short period after Three Gorges Reservoir was built up. Water quality standard of the the main bay of Three Gorges Reservior reached II, III water quality standards.