Pollution from psychotropic drugs can harm wild fish

Antidepressants like Prozac (fluoxetine) have helped millions of people around the world, but studies show they can harm wildlife and wild fish.

Antidepressants with tongue-twisting names such as fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), citalopram (Celexa), escitalopram (Cipralex) and sertraline (Zoloft) are typically the drugs of choice in the treatment of depression and anxiety disorders and are therefore a godsend for many millions of people around the world.

But these psychoactive drugs, which are mainly metabolized in the liver, are not completely broken down in the human body, producing active metabolites (ref.). The body then excretes the drug itself as well as its metabolites through urine and feces. This raises an important question: what happens to them after they are eliminated?

Worryingly, pharmaceutical waste and metabolites end up in water. Thanks to our improved analytical techniques, we have been able to detect antidepressants virtually everywhere: in wastewater, surface water, groundwater and even drinking water. However, wastewater treatment plants are not specifically designed to completely remove pharmaceutical drugs and their metabolites from water, so the residues enter the environment via sewage or sludge, where they remain in small amounts in rivers, lakes and seas. This spells trouble: recent studies have found that these drugs and their metabolites accumulate in the tissues of aquatic organisms such as fish and, as a result, dramatically alter the fish's behavior, life history and reproductive characteristics.

Despite the fact that pharmaceutical pollutants are becoming a pervasive problem in aquatic environments worldwide, the actual effects of these chemicals on aquatic life, particularly on their behaviour and reproductive success, are still unclear.

A new study aims to address this information deficit. To investigate the effects of Prozac pollution, an international collaboration launched a five-year study in which researchers exposed wild-caught guppies to three environmentally relevant concentrations of fluoxetine (Prozac) over several generations. Male guppies were the focus of this study because they exhibit measurable increased sensitivity to environmental changes.

After five years of fluoxetine exposure, the team examined the fish's behavior, body condition, and reproductive health. Their results were concerning. The researchers measured key life history traits (Figure 1) such as body condition, coloration, and size of the gonopodium (a modified anal fin that serves as a reproductive organ in male live-bearing fish), as well as key sperm traits such as vitality, number, and speed.

The study found that fluoxetine exposure disrupted the natural relationships between all key traits measured. For example, the expected relationship between activity level and body condition and between gonopodium size and sperm vitality was altered. This disruption suggests that fluoxetine exposure disrupts the physiological trade-offs that fish make between survival and reproduction.

“Even at low concentrations, fluoxetine altered the body condition of guppies and increased the size of their gonopodium, while simultaneously reducing sperm velocity – a key factor in reproductive success,” said the study's lead author, behavioral and evolutionary biologist Upama Aich, a postdoctoral fellow at Monash University's School of Biological Sciences, where she studies the effects of pharmaceutical and agricultural pollutants on the animals' behavior and reproduction.

As expected, there were also measurable effects on behavior.

“Fluoxetine exposure also significantly reduced the behavioral plasticity of the guppies, resulting in a reduced ability of individuals to adapt their own activities and risk-taking behavior to different situations,” reported one of the study's co-authors, behavioral ecologist Giovanni Polverino, assistant professor at the University of Tuscia and adjunct research fellow at Monash University and the University of Western Australia. Professor Polverino studies how animals respond to environmental changes and predicts how species might respond to a rapidly changing world.

The most disturbing finding of the study was that fluoxetine and its metabolites harm male guppies even after long-term exposure to small amounts. The fish were exposed to “environmentally relevant” levels of fluoxetine – similar to what they would be exposed to in the wild.

“The disruption of behavioral plasticity and the altered relationships between critical traits could impair the ability of fish populations to adapt to environmental challenges and threaten their long-term survival,” said the study's lead author, behavioral and evolutionary ecologist Bob Wong, professor in the School of Biological Sciences at Monash University and secretary of the International Society for Behavioral Ecology.

This study provides important insights into how chronic exposure to common pharmaceutical pollutants and their metabolites can fundamentally alter key traits needed for survival and reproduction in fish, not just guppies. But it's important to note that other animals are affected too: for example, I published a disturbing study a few years ago on how Prozac affects the behavior of starlings (you can read more about that here).

This study is an important warning and highlights the urgent need for a comprehensive approach to assessing the ecological and evolutionary consequences of pharmaceutical pollution. As our population grows and we become increasingly dependent on medicines, the strain we place on natural systems also increases. As we continue to introduce new pollutants into the environment, understanding and acting on their negative impacts on wildlife is essential to conserving biodiversity and safeguarding the overall health of ecosystems and the services they provide.

These findings have far-reaching implications for understanding the adaptive capacity of wildlife to environmental challenges. Given the profound and interconnected impacts of this contaminant, particularly in the long term, on the behavior, life history, and reproductive traits of freshwater fish and their ecosystems, this study serves as a stark warning and highlights the need for a comprehensive and holistic approach to assessing the ecological and evolutionary consequences of pharmaceutical contaminants in aquatic ecosystems.

Source:

Upama Aich, Giovanni Polverino, Farin Yazdan Parast, Gabriela C. Melo, Hung Tan, James Howells, Reza Nosrati and Bob BM Wong (2024). Long-term effects of widespread pharmaceutical pollution on trade-offs between behavioural, life history and reproductive traits in fishes, Journal of Animal Ecology | doi:10.1111/1365-2656.14152

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