Analysis of Macrobenthos Community Structure in the Adjacent Sea Area of Changjiang River Eastuary

Fifty species of macrobenthos have been identified in the adjacent sea area of Changjiang River Eastuary in May 2004. The dominant organism is polychaeta species and abundance whereas it is benthic fishes and Echiura in terms of the biomass。The average biomass of the macrobenthos in the Changjiang estuary is 17.57g/m2 , and the average abundance is 150ind./ m2. The high abundance and biomass of macrobenthos distribute near the sublittoral area of 25 grade isohaline.By the Bray-Curtis similarity cluster analysis and the multi-dimensional scaling technique, 4 communities of macrobenthos can be distinguished in the Changjiang Estuary as follows: Community Ⅰ Eocylichna cylindrella-Amphiura vadicola -Protankyra bidentata-Notomastus latericeus; Community Ⅱ Eocylichna cylindrella-Gammaridae; Community Ⅲ Notomastus latericeus-Paraprionospio pinnata-Sternaspis sculata-Magelona cincta -Ophiactis affinis; Community Ⅳ Lumbrineris latreilli-Glycera chirori-Nemertinea. The macrobenthos community is correlative with the salinity of the bottom and the organics content in the sediment by using the multi-dimensional scaling ( MDS ) technique. The salinity fluctuates with season with acute changes in the short-term due to the flux and ebb tide , which is one of the main reasons that causes the indigence of the communities Ⅱ and Ⅳ, another reason is the rapid and shirt-term suspended silt particles at the estuary.