The effects of wastewater effluent on a fish and amphibian species

Wastewater effluents have been shown to contain a variety of anthropogenic compounds, many of which have endocrine-disrupting properties. While multiple laboratory studies have shown the effects of such compounds on an individual basis at elevated concentrations, little research has attempted to characterize the effects of exposure to environmentally relevant mixtures of endocrine disruptors. The current study examined the effects of long-term exposure to graded concentrations of wastewater effluent on the fathead minnow, Pimephales promelas, and the northern leopard frog, Rana pipiens. Fathead minnows were exposed from the larval stage through sexual maturity, while northern leopard frogs were exposed as eggs and grown through metamorphosis. An F1 generation of fathead minnows was cultured in control water to test for transgenerational effects of the parental exposure to wastewater effluent. A third experiment examined the effect of triclosan, an antimicrobial compound commonly found in wastewater effluent, on the growth and development of the pickerel frog, Rana palustris. A decrease in the expression of secondary sex characteristics and an increase in the gonadosomatic index of male fathead minnows exposed to wastewater effluent in the parent generation were observed. Accelerated reproductive activity and an increase in the expression of male secondary sex characteristics were observed in the F1 generation whose parent generation was cultured in wastewater treatments. Juvenile male northern leopard frogs exhibited an increased incidence of individuals with testicular oocytes. Leopard frogs cultured in the two highest concentrations of wastewater effluent took significantly longer to reach metamorphosis than both the control and the lowest wastewater concentration treatment. Exposure to triclosan did not significantly affect the growth or development of the pickerel frog. The results of this study suggest that long-term exposure to wastewater effluent can interfere with the sexual development of the fathead minnow and can elicit responses in subsequent generations. Sexual development of male leopard frogs and the metamorphic process in leopard frogs is particularly sensitive to wastewater exposure.