Studies on the Impacts of Large-Scale Estuarine Engineering on Species Composition and Biomass of Benthos in the Yangtze River Estuary

A complete survey of benthos in the regions of deep-channel regulation of the Yangtze River Estuary was conducted from May to June 2002. The characteristics of species composition and biomass of benthos were studied and analyzed. The results showed that: ( 1 ) 19 benthos were found this time. In contrast with the results in 1982—1983 and 1998, it decreased by 87.6 % and 20.8 % respectively in species number. The dominant species were Anopla and Nereidae with existing frequencies of 32 % and 24 % respectively. ( 2 ) Average density was 21.8 individual s/m2, decreasing by 65.9 % in contrast with that in 1998. ( 3 ) Average biomass was 5.68 g/ m2, decreasing by 76.5 % in contrast with that in 1982—1983. ( 4 ) The impacts by the No.1 project has influenced the ecosystem structure in the Yangtze River Estuary. The variation of benthic species composition and biomass in the Yangtze River Estuary was related to the change of local small-scale sea water currents caused by the No.1 project of deep-channal regulation. Therefore, dynamic monitoring on the influences of large-scale estuarine engineering on estuarine ecosystem and ecological restoration in the Yangtze River Estuary is emergent.