Abstract: Seasonal sampling of macrozoobenthos was performed in Dianshan Lake from 2009 to 2010 to explore the relationships of these organisms to carbon, nitrogen and phosphorus in the sediment and then assess water quality in Lake ecosystem. The benthic environmental quality was assessed based on the biotic and diversity indices of macrozoobenthos and the indices of sediment nutrients. A total of 17 macrozoobenthic species from 5 classes and 3 phyla, were identified. Heteromastus filiformis, Nephtys oligobranchia, Corbicula fluminea were the dominant species, with H. filiformis and N. oligobranchia making up 81.2% of the community density, N. oligobranchia and C. fluminea accounting for 75.0% of the biomass. The total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in the sediment was 7.91, 1.02, and 0.79 mg/g,respectively. There were no significant correlations between these biological and environmental parameters. The multivariable analyses indicated no spatial differences in the species numerical composition of macrozoobenthos; Significant spatial difference was only detected in TN with a non-parametric Friedman test (multiple paired samples analysis), among standing crop (density and biomass), diversity index (Shannon-Wiener diversity index ［H’］, Simpson diversity index ［D］, Margelef index ［ｄ］, Pielou evenness index ［Ｊ］) ,and sediment TOC, TN and TP . The correlation analysis showed that the standing crops were positively correlated with sediment TN, diversity indices were negatively correlated with sediment TP. The biological and sediment parameters indicated that Dianshan Lake was moderately to heavily polluted or mesotrophic to eutrophic. Dianshan Lake was characterized by low density of the whole community and oligochaetes and dominance of polychaetes and C. fluminea, which may be attributed to the sediment composition of the lake bed (silt and clay with low TOC concentrations) and its connection to the East China Sea by two short rivers.
Key words：Dianshan Lake; macroinvertebrates; sediment nutrients; community structure; water quality assessment