An Assessment of the Spatial and Temporal Variability of Biological Responses to Municipal Wastewater Effluent in Rainbow Darter (Etheostoma caeruleum) Collected along an Urban Gradient

Abstract

Municipal wastewater effluent (MWWE) and its constituents, such as chemicals of emerging concern, pose a potential threat to the sustainability of fish populations by disrupting key endocrine functions in aquatic organisms. While studies have demonstrated changes in biological markers of exposure of aquatic organisms to groups of chemicals of emerging concern, the variability of these markers over time has not been sufficiently described in wild fish species. The aim of this study was to assess the spatial and temporal variability of biological markers in response to MWWE exposure and to test the consistency of these responses between seasons and among years. Rainbow darter (Etheostoma caeruleum) were collected in spring and fall seasons over a 5-year period in the Grand River, Ontario, Canada. In addition to surface water chemistry (nutrients and selected pharmaceuticals), measures were taken across levels of biological organization in rainbow darter. The measurements of hormone production, gonad development, and intersex severity were temporally consistent and suggested impaired reproduction in male fish collected downstream of MWWE outfalls. In contrast, ovarian development and hormone production in females appeared to be influenced more by urbanization than MWWE. Measures of gene expression and somatic indices were highly variable between sites and years, respectively, and were inconclusive in terms of the impacts of MWWE overall. Robust biomonitoring programs must consider these factors in both the design and interpretation of results, especially when spatial and temporal sampling of biological endpoints is limited. Assessing the effects of contaminants and other stressors on fish in watersheds would be greatly enhanced by an approach that considers natural variability in the endpoints being measured.

Site fidelity and movement of a small‐bodied fish species, the rainbow darter (Etheostoma caeruleum): Implications for environmental effects assessment

“…These included two tagging events in 2014 (August and November) and two periods in 2015 (May and August). May 2015 was selected as one of the recapture events as it is known that in southern Ontario, the rainbow darter spawn (asynchronously) between April and June (Fuzzen et al, ). The recapture efforts in August and November 2014 only involved fishing in the three core riffles.…”

“…The rainbow darter ( Etheostoma caeruleum ), a small‐bodied species (up to 80 mm), has recently been used as a sentinel species in several biomonitoring studies to assess the effects of municipal wastewater in the Grand River watershed in southern Ontario (Fuzzen et al , ; Hicks, Fuzzen, et al, ; Hicks, Loomer, et al, ). This benthic species is short lived, reaching a maximum age of 5 years (Beckman, ), are sexually mature at age 1+ and spawn in the spring (Winn, ).…”

“…Recent work in the Grand River watershed revealed reproductive impacts including high rates of intersex (ova–testis) in the male rainbow darter at sites below two wastewater treatment plants (WWTPs; Kitchener and Waterloo). The impacts were attributed to contaminants such as endocrine‐disrupting compounds present in the WWTP effluent (Fuzzen et al , ). The same phenomenon (though at lower rates) were also consistently observed in an urban upstream site in close proximity (1–2 km) to the Kitchener WWTP outfall.…”

Assessing recovery of in vitro steroid production in male rainbow darter (Etheostoma caeruleum) in response to municipal wastewater treatment plant infrastructure changes

“…A variety of biological effects in the native rainbow darter ( Etheostoma caeruleum ) have been associated with exposure to these effluents, including a high prevalence of intersex (Bahamonde et al ; Fuzzen et al ; Tanna et al ; Tetreault et al ). Molecular alterations in rainbow darter, such as changes in vitellogenin mRNA abundance and specific gene expression in intersex rainbow darter, have also been observed (Fuzzen et al ; Bahamonde et al ; Bahamonde et al ). Results suggest that there is reduced fecundity associated with exposure to effluents discharged from these 2 MWWTPs (Fuzzen et al ) and decreased androgen steroid production in males (Fuzzen et al ).…”

“…Molecular alterations in rainbow darter, such as changes in vitellogenin mRNA abundance and specific gene expression in intersex rainbow darter, have also been observed (Fuzzen et al ; Bahamonde et al ; Bahamonde et al ). Results suggest that there is reduced fecundity associated with exposure to effluents discharged from these 2 MWWTPs (Fuzzen et al ) and decreased androgen steroid production in males (Fuzzen et al ).…”