Abstract: An investigation on the population dynamics, annual production, and trophic basis of dominant chironomids in the macrozoobenthos community in a second order river (Tanqigou Stream) of Qingjiang River Basin was conducted from April 2006 to March 2007. The results showed that all of the three dominant chironomids Thienemanimyia lentiginosa, Eukiefferiella potthasti and Paratanytarsus parthenogeneticus developed two generations per year. The population density of P. parthenogeneticus and T. lentiginosa reached the peaks in June, September and next January, while that of E. potthasti attained the peaks in May and next January. The annual production (in wet mass) and its ratio to biomass of the three chironomids estimated by instar frequency method were 17.44 g·m^-2 and 3.4 for T. lentiginosa, 1.66 g·m^-2 and 2.3 for E. potthasti, and 3.3 g·m^-2 and 6.4 for P. parthenogeneticus, respectively. The temporal overlap of the production among the three chironomids was relatively large in spring. The proportions of various food types and their contribution to the production were estimated by foregut content analysis, showing that amorphous detritus was the most important food type, accounting for 73.27%–86.89% of the foregut content of E. potthasti and P. parthenogeneticus, while animal material contributed 51.64% to the production of T. lentiginosa.

Key words: Black soil, Water-stable aggregate, Nutrient status