Macroinvertebrate community structure and chemistry of an organically polluted creek in south-east Queensland.

Abstract

The benthic macroinvertebrate fauna of Gowrie Creek, south-east Queensland, and 24 chemical and physical parameters were monitored for 105 km downstream from a major sewage effluent outfall between June 1981 and October 1984. Species richness declined to 2-3 taxa while the density of organisms increased significantly immediately below the outfall. A progressive increase in the number of taxa present was evident with distance downstream. The major species associations, progressing downstream from the outfall, were: Chironornus/Tubificidae: Chironornus/Sirnuliurn ornatipes; Plotiopsis balonnensis; and P. balonnensis/Cheurnatopsyche (modica?). The elimination of taxa in the vicinity of the outfall was attributed to the effects of depletion of dissolved oxygen and possibly ammonia toxicity and sulfide toxicity. Changes in dominance were related to the changes in food types associated with a transition from a heterotrophic to an autotrophic environment. The study presents additional data on community structure and species associations characteristic of different degrees of organic pollution.