Reproductive status of fathead minnows (Pimephales promelas) exposed to a combined municipal and agro-industrial effluent

Abstract

Municipal and industrial wastewaters are complex chemical cocktails, including personal-care products, pharmaceuticals, and pesticides, many of which are endocrine disrupting chemicals. Frank Lake is a multi-basin wetland in southern Alberta, Canada, restored to stable water levels in 1990 with the addition of a combined effluent from the town of High River and the Cargill beef processing facility. At high water levels, water from Frank Lake drains into the Little Bow River that ultimately drains into the Twin Valley Reservoir. The biological effects that input of largely uncharacterized chemicals might be causing in the wetland, river, and multi-use reservoir are unknown. The study objective was to assess the reproductive physiology of fathead minnows exposed to the combined effluent from High River and Cargill. Standard 96-hr and 21-day assays were performed to assess reproductive toxicity, with the 96-hr assays being completed three times over the 2024 summer season to quantify temporal variation in effluent toxicity. Fecundity was not affected with exposure. Males exposed to high effluent concentration had an increase in tubercle score, as well as a decrease in condition factor and fertilization success. Male minnows exposed to effluent also had decreased plasma concentration of 11-ketotestosterone and decreased transcript abundance of hsd11b. Temporal variation in endocrine disrupting potential of the combined effluent was observed with varying effects on health indices and gene expression in fish exposed to effluent collected at different points of the 2024 summer. This research expands the understanding of industrial and municipal effluent impact on aquatic ecosystems, including health of exposed biota, and could inform future management decisions regarding Frank Lake.