Pollution from antidepressant production is altering fish behavior and reproductive traits, scientists say

Pollution from the production of antidepressant medication is altering fish behavior and reproductive traits, highlighting the importance of understanding how such chemicals can affect aquatic ecosystems, according to a new study.

Biologists from Monash University in Australia and Italy's University of Tuscia investigated how long-term exposure to pharmaceutical pollutants, which they said are "widespread in aquatic ecosystems globally," affect the behavior, life history and reproductive traits of freshwater fish, specifically guppies, researchers said in a paper published Monday in the Journal of Animal Ecology.

Antidepressants, which have been formulated to have a "very specific effect" on humans to mitigate anxiety symptoms, have been observed to have the same behavior-altering effect on guppies exposed to pollutants that leak into waterways during the production of the medication, Giovanni Polverino, assistant professor at the University of Tuscia and one of the study's authors, told ABC News.

The researchers exposed progeny of wild-caught guppies to varying levels of fluoxetine, the antidepressant commonly sold under the brand name Prozac, over five years and across multiple generations, according to the paper, which describes fluoxetine as "a widespread pharmaceutical pollutant."

During that time, researchers studied and noted the activity and risk-taking behavior of the male guppies, as well as life-history traits – such as body condition and coloration – and reproductive traits, including "sperm vitality, number and velocity."

They found that exposure to fluoxetine had a dose-specific negative effect on the life-history and sperm traits of guppies, eroding natural variation in both activity and risk-taking behavior among individuals in the study group.

Polverino said their findings suggest that fluoxetine in the ecosystem may have similar effects on other species.

"I wouldn't say that it shocked us, but it scared us," he said, "because this is just, like, five years of exposure for our guppies is 15 generations. But now you imagine that fluoxetine has been found and monitored in many like wild habitats for decades. So the effects clearly are permanent and they build up, and this has a big impact on wildlife, fishes and others."

"Other colleagues have done works on different kind of fishes, marine animals, even salmon," Polverino added. "And so you can see that the effects are pretty much, you know, spread across the animal realm, and they're important."

Even at low concentrations, exposure to fluoxetine altered the male guppies' body condition and increased the size of their gonopodium, which is the anterior fin used as a male reproductive organ, the latter resulting in fish that "swam on average less and hid more than others." Fluoxetine exposure in some cases and at different levels also reduced sperm velocity, which is an essential factor for reproductive success, the researchers said.

"It is kind of scary," Polverino told ABC News. "These are the concentrations most common around the world," he added, further noting that the concentrations are "enough to really ... create big issues."

The impact of fluoxetine "goes beyond simple, average responses and influences specific traits and their correlations," the researchers wrote – meaning that the trade-offs between "behavior, life-history and reproductive traits" that the fish normally make can be disrupted by exposure to the pollutant.

Exposure to fluoxetine is essentially causing a trade-off between competing functions, Polverino explained, noting that living beings typically have an "energy budget." If the guppy is spending a lot of energy on activity, it probably has less energy to compete with other males for mating, he added.

"In an absence of the pollution, fish typically invest their energy in a specific way," he said. "But in presence of the pollution, animals are medicated to behave in a different way."

The researchers also discovered that plasticity – that is, the fishes' capacity to adjust their behavior – collapsed as a result of the presence of the pollutant, Polverino said. So while the guppies survived the exposure to the pollutant, they are less likely to adapt to other changes to the environment, such as climate change, other pollutants, or alien species.

"Our results reveal that chronic exposure to global pollutants can affect phenotypic traits at both population and individual levels, and even alter individual-level correlations among such traits in a dose-specific manner," the study declared, referring to both the appearance and behavior of the fish observed in the study.

"These findings have broader implications for understanding the adaptive capacity of wildlife facing environmental challenges," the study concluded, and "highlights the need for a comprehensive and holistic approach to assessing the ecological and evolutionary consequences of pharmaceutical pollutants in aquatic ecosystems."

"Our world is changing pretty fast, and animals will be less and less capable to adjust because of the effect of this pollutant," Polverino said.