Molecular and Behavioral Impacts of Treated Wastewater Effluent on Fish

Abstract

Currently, most studies that focus on the sublethal impacts of contaminants of emerging concern (CECs) such as pharmaceuticals utilize a single-compound approach, whereas these compounds always occur as complex mixtures in the environment. Wastewater treatment plants (WWTPs) are a major contributor to the formation of these mixtures as current treatment technologies inadequately remove many chemical pollutants. There is a paucity of knowledge on the neurological impacts due to exposure to complex CEC mixtures resulting from the discharge of treated WWTP effluent into aquatic environments. This knowledge gap leaves incomplete assessments of the hazards and risks from exposure to treated effluent as even sublethal neurotoxicity can lead to negative ecological consequences. The present study utilized an in-situ effluent-dominated stream exposure as well as laboratory-controlled exposures to assess potential neurological impacts of CEC mixtures in fish using molecular, computational, and behavioral approaches. Candidate gene biomarkers for effluent exposure were identified in fathead minnows (Pimephales promelas) that were also shown to relate to adverse neurological states. Behavioral endpoints related to locomotion and anxiety were measured in larval zebrafish (Danio rerio) to help determine the utility of this test for studying sublethal neurological impacts in response to chemical mixture exposures.