Prozac Contamination in Water Is Changing Fish Behaviors, Study Finds

In a new study, scientists have confirmed that even low concentrations of the antidepressant pharmaceutical fluoxetine, also known by the brand name of Prozac, are affecting fish behaviors in the wild.

Biologists from Monash University in Melbourne, Australia and the University of Tuscia in Viterbo, Italy have completed a five-year investigation on how fluoxetine pollution in waterways impacted wild-caught guppies (Poecilia reticulata).

During the five years of research, up to 15 generations of the guppies were exposed to three different levels of fluoxetine at 0, 31.5 and 316 nanograms per liter (ng/L) while researchers observed and recorded the guppies’ various activities and risk-taking behaviors. The amounts of fluoxetine used in the study were meant to mimic amounts found in waterways in the wild.

Researchers also noted the guppies’ various key traits, including body condition, body coloration, sperm vitality and more to detect how the pollutants may be affecting the animals’ life-history and reproduction.

According to Upama Aich, biologist and research fellow at the Monash University School of Biological Sciences, the low concentrations of fluoxetine changed the body condition and gonopodium size of the guppies and lowered sperm velocity, which could impact reproduction.

Further, Giovanni Polverino, assistant professor at the University of Tuscia, explained that the exposure to the pharmaceutical pollutants “significantly reduced the behavioural plasticity of guppies, leading to a lower capacity of the individuals to adjust their own activity and risk-taking behaviours across contexts.”

The study, which was published in the Journal of Animal Ecology, determined that long-term exposure to this drug, even at lower concentrations, affects fish both as individuals and as larger populations.

“The disruption of behavioural plasticity and the altered correlations between critical traits could undermine fish populations’ ability to adapt to environmental challenges, threatening their long-term survival,” Bob Wong, senior author of the study and professor at the Monash University School of Biological Sciences, said in a statement.

The findings add to a growing body of research that outlines the damage that drug pollution does to aquatic life. In June of this year, scientists warned that both pharmaceuticals and illegal drugs were having major impacts on wildlife, and the contaminants could leach into groundwater and threaten human health. Last month, researchers behind a separate study published in Science of the Total Environment found that sharks in Brazil were testing positive for cocaine.

The researchers behind the study on fluoxetine pollution are calling for enhanced policies and regulations to minimize pharmaceutical pollution and reduce the threats to aquatic life. 

“Considering the potential constraints on phenotypic variation and altered trait associations, our study highlights the need for a comprehensive and holistic approach to assessing the ecological and evolutionary consequences of pharmaceutical pollutants in aquatic ecosystems,” the study concluded.