Abstract:

With the rapid economic development and overexploitation of resource, the aquatic ecosystem of the Zhenjiang Reach of the Yangtze River is threatened by all kinds of disturbances. In order to fully understand the present status of the macrozoobenthic community, this study was carried out from March to December in 2010. Sediment samples were collected with a 1/16 m2 Peterson grab and cleaned with a 420 μm sieve. Animals were sorted in a white porcelain dish and specimens were preserved in 10% formalin. Altogether 26 species belonging to 7 families and 21 genera were recorded, including 12 species of oligochaetes, 1 species of polychaetes, 4 species of molluscs and 9 species of aquatic insects. The dominant species were Teneridrilus mastix, Branchiura sowerbyi, Nephthys polybranchia and Tanypus sp.. The standing crop of the macrozoobenthos was 74 ind./m2 in density and 0.2 g/m2 in biomass. Among three habitats, higher biodiversity were found in conservation district. Generally, higher density of the macrozoobenthos was observed in spring and summer, while the biomass was found greater in spring and autumn. The composition of the functional feeding groups was mainly determined as collectors. Comparisons of macrozoobenthic community characteristics among the lower reaches of the Yangtze River were carried out. Density was highest in Yangzhong Reach and lowest in Zhenjiang Reach. However, biomass was highest in Jiangyin Reach and lowest in Zhenjiang Reach. Zhenjiang Reach and Yangzhong Reach had more species than Jiangyin Reach