Dilute Concentrations of a Psychiatric Drug Alter Behavior of Fish from Natural Populations

TLDR

Environmental pollution by pharmaceuticals, entering waterways through treated wastewater effluents and remaining biochemically active, poses a growing threat to aquatic ecosystems, yet the ecological effects of these compounds remain largely unknown. Our study demonstrates that dilute concentrations of the anxiolytic benzodiazepine oxazepam (1.8 µg L⁻¹) alter wild European perch behavior—raising activity, decreasing sociality, and increasing feeding rate—highlighting potential ecological and evolutionary impacts.

Abstract

Environmental pollution by pharmaceuticals is increasingly recognized as a major threat to aquatic ecosystems worldwide. A variety of pharmaceuticals enter waterways by way of treated wastewater effluents and remain biochemically active in aquatic systems. Several ecotoxicological studies have been done, but generally, little is known about the ecological effects of pharmaceuticals. Here we show that a benzodiazepine anxiolytic drug (oxazepam) alters behavior and feeding rate of wild European perch (Perca fluviatilis) at concentrations encountered in effluent-influenced surface waters. Individuals exposed to water with dilute drug concentrations (1.8 micrograms liter(-1)) exhibited increased activity, reduced sociality, and higher feeding rate. As such, our results show that anxiolytic drugs in surface waters alter animal behaviors that are known to have ecological and evolutionary consequences.