Antidepressants from Wastewater Cause Fish to Fear Predators Less

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Antidepressants from Wastewater Cause Fish to Fear Predators Less

Antidepressants are making their way into our lakes and rivers—and they're making freshwater fish less fazed by predators.

Jake Martin, a PhD candidate at Monash University, looked at how the eastern mosquitofish (Gambusia holbrooki) responded to the threat of a predator when they had been exposed to the antidepressant fluoxetine (using levels similar to those already found in some waterways).

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He found that dosed up fish were more active in the presence or absence of a live predator, and entered the striking range of the predator more quickly.

"Exposed fish were less stressed by a simulated predator strike, returning to normal swimming behaviour more quickly. These changes are likely to make them more vulnerable to being eaten," Jake says.

"More broadly, these findings highlight the potential for pharmaceutical drugs to affect whole ecosystems, by changing the dynamics of predator-prey interactions."

Approximately one in every 10 pharmaceutical products currently manufactured has been detected in the environment. Jake says that the very same things that make them useful as medications—such as their ability to act at low dosages and resist being degraded—make them especially harmful as pollutants.

"In 2016, more than 1.7 million scripts for fluoxetine were filled here in Australia alone. Further, fluoxetine has also been repeatedly detected in the Australian environment, including estuaries in Sydney Harbour."

These drugs make their way into freshwater systems when a proportion is passed in their urine. After the toilet is flushed, they're funnelled through the wastewater treatment system, eventually ending up in lakes and rivers.

Despite worldwide recognition of pharmaceutical pollution as an emerging environmental problem, Jake says we know very little about the environmental effects of many drugs present in aquatic ecosystems.

The study was published in  Environmental Pollution .

ABSTRACT

Chemical pollution from pharmaceuticals is increasingly recognised as a major threat to aquatic communities. One compound of great concern is fluoxetine, which is one of the most widely prescribed psychoactive drugs in the world and frequently detected in the environment.

The aim of this study was to investigate the effects of 28-d fluoxetine exposure at two environmentally relevant levels (measured concentrations: 4 ng/L and 16 ng/L) on anti-predator behaviour in wild guppies ( Poecilia reticulata ).

This was achieved by subjecting fluoxetine-exposed and unexposed guppies to a simulated bird strike and recording their subsequent behavioural responses. We found that exposure to fluoxetine affected the anti-predator behaviour of guppies, with exposed fish remaining stationary for longer (i.e. ‘freezing’ behaviour) after the simulated strike and also spending more time under plant cover.

By contrast, control fish were significantly more active and explored the tank more, as indicated by the distance covered per minute over the period fish spent swimming. Furthermore, behavioural shifts were sex-dependent, with evidence of a non-monotonic dose-response among the fluoxetine-exposed fish.

This is one of the first studies to show that exposure to environmentally relevant concentrations of fluoxetine can alter the anti-predator behaviour of adult fish. In addition to the obvious repercussions for survival, impaired anti-predator behaviour can have direct impacts on fitness and influence the overall population dynamics of species.

Article source: Phys.org

Access paper: Monash University

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