This thesis describes the effects of oil sands process waters (OSPW) on the benthic macroinvertebrate component of wetland ecosystems through assessment of biological responses at various levels of organization. Comparison of the macroinvertebrate communities among OSPW-affected wetlands and environmentally-similar reference wetlands indicated an insignificant trend of reduced taxonomic richness and abundance. Also, the general benthic macroinvertebrate community and specifically the chironomid community showed differences in community composition between OSPW and reference wetlands, in terms of the presence and relative abundances of dominant taxa.

The incidence of chironomid mouthpart deformities, a biomarker of teratogenicity, was low at three pairs of reference and OSPW wetlands. Similarly, there was no evidence to show that OSPW induces mouthpart deformities. However, growth and survival were significantly reduced in both lab and field-derived C. tentans larvae exposed to higher concentrations of OSPW.