Effects of Yangshan Project in Hangzhou Bay on distribution of zooplankton biomass in the adjacent waters

Based on the data from two seasonal oceanographic surveys in adjacent water of the Hangzhou Bay(30o32'-30o50'N,121o53'-122o17'E) in spring(May) and summer(August) of 2001 and 2003-2007,the annual alteration and horizontal distribution of zooplankton biomass,as well as the contribution of dominant species to total abundance were studied.Moreover,the relationship between the zooplankton and the engineering construction was also discussed.The results showed that the average of biomasses in May and August of 2001 and 2003-2007 were 207.41 mg/m3 and 234.16 mg/m3 respectively.The biomass was the highest in May and August of 2007,while lowest in 2003 and 2004 of two seasons.Labidocera euchaeta was the dominant species of the two seasons in the six years.In May Tortanus vermiculus and Calanus sinicus were the major dominant species,while Acartia pacifica and Centropages dorsispinatus were the dominant ones in August.Calanus sinicus was the predominant species in May,while Acartia pacifica was the predominant one in August.These two species greatly contributed to the total abundance.In addition,the trend of zooplankton biomass and the annual succession of the dominant species were closely related with the progress of Yangshan project.The biomass decreased to the lowest point during the construction period and in the area where the major project located the zooplanktonic biomass was particularly low.Moreover,the contribution of the major dominant species to the total abundance was also low comparing with other periods.However,after the completion of the construction,the biomass of investigated water began to rise and the region biomass gradually recovered to the level before the construction of the project.