Abstract
Ecological impacts of contaminants on population patterns in wild fish are impacted by many contaminants that readily enter aquatic systems. Responses to toxicants by individuals in lab studies generally do not predict population level consequences in natural systems. Trace levels of contaminants are present in all major rivers in southern Alberta, Canada, with concentrations higher down-stream of anthropogenic inputs like agricultural land-use and inputs of municipal wastewater effluents. Longnose dace (Rhinichthys cataractae) were used as a sentinel species to study field-based population-level responses to contaminants. We hypothesized that biomarker activity, triggered by contaminant exposure, should increase downstream of anthropogenic inputs in two southern Alberta rivers, with corresponding relations between biomarker activity and sex ratios, after accounting for age structure. Liver detoxification (ethoxyresorufin-O-deethylase activity = EROD) measured at reference and exposed sites on each river differed significantly in only the Bow River system. Sex ratios varied more downstream of anthropogenic inputs than upstream, but the direction of sex ratio bias was inconsistent and temporally dynamic. Sex ratios correlated with liver detoxification in only the Bow River. Taken together, these results suggest that contaminants alter sex ratios in long-nose dace, but that there is variation in anthropogenic stressors among rivers.
Highlights
The biological impacts of contamination in freshwater systems vary extensively [1] [2] from direct, overt toxic-How to cite this paper: Tunna, H.R., Smits, J.E.G., Rogers, S.M. and Jackson, L.J. (2016) Detoxification Efforts in Longnose Dace (Rhinichthys cataractae) Exposed to Municipal and Agricultural Inputs
Females and males were common at sites on the Bow River upstream of Calgary’s three Wastewater Treatment Plant (WWTP) (Table 2, Total tests for BOW1 and BOW2) and displayed stable sex ratios among years (Table 2)
Variable sex ratios downstream of anthropogenic inputs suggest that contaminants may drive temporally variable sex ratios, yet the mechanism(s) are not clear
Summary
The biological impacts of contamination in freshwater systems vary extensively [1] [2] from direct, overt toxic-How to cite this paper: Tunna, H.R., Smits, J.E.G., Rogers, S.M. and Jackson, L.J. (2016) Detoxification Efforts in Longnose Dace (Rhinichthys cataractae) Exposed to Municipal and Agricultural Inputs. The Cytochrome P4501A (CYP1A) metabolic pathway is a common biomarker used to assess contaminant exposure in aquatic systems [8] [9]. Two biomarkers on the AhR detoxifying pathway include vitellogenin upregulation and hepatic detoxification, both of which provide evidence of the presence of exposure to pollutants that activate the AhR-pathway in many vertebrates, including fish. Elevated EROD activity provides evidence of contaminant exposure [12] and has been used as an early warning biomarker of exposure to contaminants in terrestrial and aquatic systems [13] [14]. EROD provides a measure of general contamination whereas vitellogenin expression is a measure of exposure to estrogen-like endocrine disrupting compounds (EDCs)
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