Abstract: The implementation of South-to-North Water Transfer Project will bring about some impacts on the ecological environment of aquatic organisms at Yangtze River estuary. Planktonic crustaceans are the one of important components of aquatic organisms. In this study, the planktonic crustaceans in the north and south branches at Yangtze River Estuary were surveyed in autumn 2005 and spring 2006, with the region from Xuliujing to lighthouse 50 on the estuary, a total length of 181.8 km, and a broad expansion from west to east about 5.7 km to about 90 km with a fan-shape. Three cross-sections and 14 survey points were established. A total of 54 planktonic crustacean species, which belonged to 37 genera under 23 families, were recorded. There were 15 species of cladocerans belonging to 8 genera under 6 families, and 39 species of copepods belonging to 29 genera under 17 families. More planktonic crustacean species were observed in autumn than in spring, and more copepod species were found in north branch than in south branch. Planktonic crustaceans had an average density of 9.10 ind·L^-1, and their total biomass, mainly composed of copepods, was 0.1179 mg·L^-1. The standing crop at cross-section III in the north branch was far higher than that at other sections. Bosmina longirostris and Bosmina coregoni were the dominant species of cladocerans, and Sinocalanus sinensis, S. dorrii, Schmackeria forbesi and Mesocyclops pehpeiensis were the dominant species of copepods. The overall level and spatiotemporal distribution of planktonic crustaceans in the north and south branches of Yangtze River estuary and the impacts of the Water Transfer Project on the planktonic crustaceans were also analyzed.

Key words: Plutella xylostella, Secondary plant substance, Life table, Interference index of population control