Abstract: An investigation was conducted on the community structure of macrozoobenthos in the main stream of Songhua River in spring (April and May), summer (July and August), and autumn (from September to November), and the water quality of the main stream was assessed with biotic indices. A total of 116 species of macrobenthos were collected, belonging to 36 families and 16 orders, among which, aquatic insects had the largest number, with 74 species (63.8% of the total) belonging to 21 families and 6 orders. The annual average density and biomass of the macrobenthos were 66.80 ind·m^-2 and 24.30 g·m^-2, respectively. The average density was the highest (90.52 ind·m^-2) in spring, followed by in autumn (61.26 ind·m^-2), and in summer (48.63 ind·m^-2), while the average biomass was the highest (35.35 g·m^-2) in autumn, followed by in summer (23.12 g·m^-2), and in spring (14.41 g·m^-2). The Shannon index, Pielou index, and Simpson index were the highest in spring, and were nearly the same in summer and autumn. Few species inhabited in the same types of microhabitats in all river sections. The species similarity in all sections was lower, with the largest similarity being only 60%. The species quantity of each functional feeding group was near, with 26 shredders, 32 collectors, 28 scrapers, and 30 predators. The water quality assessed with biotic index (BI) and family biotic index (FBI) was basically coincident with each other, and was accordant with chemical monitoring. The water quality above the Harbin Section of Songhua River was fair, and that below the Harbin Section was contaminated or seriously contaminated. It was presumed that the macrobenthos species composition and community structure had been affected due to the building of ship-electricity hinge in Dadingzi Mountain.

Key words: Songhua River main stream, macrobenthos, community structure, biomonitoring, water quality