Abstract: Based on the macrozoobenthos and environmental materials from 35 stations in Dongtou Islands and adjacent sea area investigated in April 2015, the characteristics of macrozoobenthic community structure and its relationship with environmental factors were analyzed. Results show that a total of 122 species are identified, including 57 species of Polytraeta, 34 species of Crustacea, 19 species of Mollusca, 5 species of Echinodermata and 7 others species. The number of species is about 1~22 at each station, with lower values of species number concentrated in Oujiang River Estuary. The average biomass of macrozoobenthos is 3.35 g/m², and the average inhabited density is 321 ind/m². Polytraeta has an advantage on the species compositions, while Mollusca has the more advantages on the biomass and abundance. The average of Shannon-Wiener index(H′) is 1.29, the average of Margalef's species richness index (d) is 2.45, and the average of Pielou's evenness index (J′) of species is 0.66. By species similarity cluster analysis and multidimensional scaling ordination analysis, three communities of macrozoobenthos can be divided in Dongtou Islands and adjacent sea area, those are: Heteromastus filiforms-Yoldia similis-Raphidopus ciliatus-Sternaspis scutata (Community Ⅰ), Yoldia similis-Heteromastus filiforms-Aglaophamus dibranchis-Sternaspis scutata (Community Ⅱ), and others (Community Ⅲ ). Canonical correspondence analysis show that the sea water temperature, water salinity, activated phosphate, activated silicate, dissolved inorganic nitrogen, chemical oxygen demand and the total organic carbon in surface sediment are the main environmental factors affecting the macrozoobenthic community. The ABC curves indicate that the macrozoobenthic communities in Dongtou Islands and adjacent sea area have suffered contamination or have disturbed to a certain degree. Compared with historical data, the average biomass and abundance of macrozoobenthos have not obviously changed. The dominant organism of the species compositions are Polytraeta and Crustacea, instead of Polytraeta and Mollusca, and the number of Turritella bacillum in the area has obviously declined.

Key words: macrozoobenthos, community structure, species diversity, environmental factor, Dongtou Islands and adjacent sea area