Abstract: Based on the four seasons investigation data from 1997 to 2000, this paper analyzed the ecological characters and quantitative variations of Cladocera in the East China Sea (23°30′～33°00′N, 118°30′～128°00′E). The results showed that the total abundance of Cladocera was the peak in summer (17.16 ind·(100 m³)^-1), the second highest in autumn (14.68 ind·(100 m³)^-1) and the lowest in spring (0.63 ind·(100 m³)^-1), while no occurrence in winter. Evadne tergestina in spring, summer and autumn and Penilia avirostris in summer were the species dominating the variation of the total abundance. In spring, summer and autumn, the total abundance of Cladocera had a negative linear correlation with the salinity of seawater, but no significant correlation with water temperature. The areas with high abundance of Cladocera were usually located at the side of the dilute waters from continental rivers in the converging area of the dilute waters and other water masses, suggesting that the variation of the total abundance of Cladocera was dependent on the eat and flow of the dilute waters, especially that of the Changjiang dilute waters in the East China Sea. The zooplankton, with lower occurrence frequency and aggregated distribution, was a kind of indicator species for the dilute waters. Its high abundance areas were basically restricted in the waters of the dilute waters, and water with high abundance was a sign of the dilute water.

Key words: NPK levels, Oilseed rape, Boron uptake, Biological properties