Ecological characteristics of wetlands receiving an industrial effluent

The primary objectives of this study were to evaluate the ecological charac teristics of wetland ecosystems that had developed in response to oil sands effluent relative to reference wetland ecosystems and, from such an evalua tion, to assess whether these wetlands were viable systems capable of integ rating into the northern Canadian landscape. A secondary objective was to e valuate the use of several ecologically relevant endpoints as indicators of an ecosystem response to a known anthropogenic stress, in this case, wetla nds receiving oil sands effluent. To achieve this, a suite of endpoints wer e compared between effluent-impacted wetlands and nonimpacted reference wet lands. Endpoints for comparison included: (1) benthic macroinvertebrate com munity structure, (2) chironomid density and biomass, (3) the incidence of chironomid mentum deformities, (4) the mutagenetic potential of sediment-dw elling chironomids, (5) growth and photosynthetic rare for the aquatic plan t Typha latifolia (cattail), and (6) fish acute lethality and stress respon se as measured by changes in blood chemistry (percentage hematocrit [%hct], percentage leucocrit [%lct], and differential white blood cell count). Wet lands receiving oil sands effluent supported a low-diversity benthic commun ity, dominated primarily by the Chironomidae and cattail. There was no evid ence of mentum deformities or mutagenicity in chironomids sampled from the oil-impacted wetlands. Cattails grown in oil sands effluent and sediment de monstrated increased photosynthetic rates; however, these increased rates d id not translate into increased plant growth. In contrast to the benthic co mmunity and the cattail, indigenous fish were unable to survive in wetlands containing oil sands effluent. Fish displayed altered blood chemistry (ele vated %hct, depressed %lct) and ultimately death when held beyond 14 d in t he oil-impacted wetlands. Of the various ecological endpoints measured, the macroinvertebrate community and changes in fish blood chemistry were the m ost sensitive indicators of an anthropogenic stress, demonstrating distinct differences in response between impacted and reference wetlands. To ensure that these wetlands can safely integrate into the northern Canadian landsc ape, future studies need to focus on their impacts at higher trophic levels indigenous to the wetland.