Effect of sewage effluent on dragonflies (Odonata) of Bulimba Creek, Brisbane

Abstract

The adult dragonfly fauna and the larval fauna and abundance decrease markedly immediately downstream of the outfall from the Mimosa Sewage Treatment Plant into Bulimba Creek. The adult fauna is substantially restored farther downstream, but the larval fauna and abundance are not. Of the 36 species of Odonata observed at Bulimba Creek, the 10 abundant, essentially stream-dwelling species were most affected by the sewage effluent. Adults of only one of these stream species were found at the most contaminated site, and then only in very low numbers; those of two others were not observed downstream of the outfall. The diversities of both adult and larval dragonfly faunas give a qualitative indication of water quality. Parallels between the distribution or abundance of Odonata and the concentrations of contaminants indicate that chlorine may be the most important toxicant immediately downstream of the sewage outfall in Bulimba Creek.