Growth, survival, and community composition of Chironomidae (Diptera) larvae in selected Athabasca oil sands process-affected wetland waters of northeastern Alberta

Oil sands process water (OSPW) is toxic to many aquatic organisms. The goal of this study is to determine if or how midge (Diptera: Chironomidae) productivity and community assemblages may differ between OSPW and reference wetlands and the effects of OSPW wetland water, naphthenic acids (NA), and salts on chironomid growth and survival. Although chironomids differed in size, abundance, and community composition among wetlands, the differences were not attributable to the presence or absence of OSPW. Community composition varied with respect to wetland-specific water chemistry attributes (e.g., dissolved oxygen). Ten-d Chironomus riparius laboratory bioassays indicated that larvae grew to a smaller size when exposed to OSPW wetland water compared to reference wetland water. When C. riparius was reared for 10 d in water mimicking combinations of salts and NA, survival was significantly negatively correlated with salt and NA concentrations, and there was an antagonistic interaction between the two toxicants.