Abstract: Community structure and spatial distribution patterns of macrozoobenthos in Dongqian Lake,Ningbo,were investigated quarterly from April 2009 to January 2010.In total,3 phylum,4 classes,28 genera,and 30 species were identified,including 5 oligochaetes,18 insects and 7 mollusks.The average annual abundance and biomass of the community were 1233 m-2 and 8.0 g/m2(wet weight),respectively.In addition,the annual secondary production was 35.3 g/(m2·a)(wet weight),as calculated by the reported P/B ratios.The dominant species in the lake were three chironomids(Propsilocerus akamusi,Tanytarsus sp.and Clinotanypus sp.) and one oligochaete(Limnodrilus hoffmeisteri).However,the dominant species changed with seasons,with P.akamusi the sole dominant species in winter.Dongqian Lake can be divided into four macrobenthic zones using Multidimensional Scaling(MDS).The GIS database and the Ordinary Kriging technique were employed to construct the spatial distribution patterns of the macrozoobenthic parameters,and to simulate the distribution of the Hilsenhoff biotic index(BI).These patterns showed that the lake was highly spatially heterogenerous,and usually 1-2 zones with high abundance occured across the lake.Chironomids mainly occurred in Guzi Lake and the center of Dongqian Lake;mollusks,however,were concentrated in the northern part of the lake and the southwestern-central part.The results of the bioassessment indicated that the water of the entire lake was moderately polluted(BI = 7.58) with temporal and spatial fluctuations.In spring and summer(April,July and September),the water was light polluted(BI = 6.66-7.33).In contrast,the pollution level in autumn and winter(December and January of the next year) was moderately polluted(BI=8.32-8.39).The water qualities in the central and eastern parts of the north lake were the best,followed by those in the Guzi and Wuli Lakes.The water in the southeastern part of the south lake showed the worst polluted.