Pharmaceutical pollution changes the behavior of Atlantic salmon

In a large-scale study considered to be the most extensive of its kind so far, researchers from around the world investigated how pharmaceutical pollution influences the behavior and migratory patterns of Atlantic salmon.

The project was led by the Swedish University of Agricultural Sciences and focused on commonly detected concentrations of clobazam – a medication used to treat sleep disorders – found in waterways.

In the wild, these levels of clobazam were shown to increase the river-to-sea migration success of juvenile salmon and shorten the time it took them to pass through obstacles like hydropower dams.

Pharmaceutical pollution in salmon habitats

The findings involved collaboration between many institutions, including Griffith University’s Australian Rivers Institute. Marcus Michelangeli from Griffith, who played a key role in the study, described it as highlighting a global and growing problem of pharmaceutical pollution in natural habitats.

“Pharmaceutical pollutants are an emerging global issue, with over 900 different substances having now been detected in waterways around the world,” Michelangeli said.

“Of particular concern are psychoactive substances like antidepressants and pain medications, which can significantly interfere with wildlife brain function and behavior.”

Unique real-world approach

One unique aspect of this research is its real-world perspective. According to Michelangeli, most previous studies examining the effects of pharmaceutical pollutants on wildlife have been conducted under controlled laboratory conditions, which don’t fully capture the complexities of natural environments.

“This study is unique because it investigates the effects of these contaminants on wildlife directly in the field, allowing us to better understand how exposure impacts wildlife behavior and migration in a natural context.”

Clobazam was not the only drug tested. The team also looked at tramadol, an opioid painkiller frequently detected in water samples.

The researchers used slow-release pharmaceutical implants in combination with tracking transmitters to monitor how both substances affected juvenile Atlantic salmon (Salmo salar) in Sweden’s River Dal as the fish made their journey toward the Baltic Sea.

In addition, the team conducted a laboratory experiment that revealed clobazam altered the salmon’s shoaling behavior, reinforcing the idea that shifts in social or risk-taking tendencies might be tied to drug-induced changes in the fish’s neural functioning.

Consequences of pharmaceutical pollution

“While the increased migration success in salmon exposed to clobazam might seem like a beneficial effect, it is important to realize that any change to the natural behavior and ecology of a species is expected to have broader negative consequences both for that species and the surrounding wildlife community,” Michelangeli said.

He also noted how complicated these consequences might be when multiple pollutants and species are involved.

“When you consider realistic exposure scenarios where entire ecosystems are exposed – encompassing multiple species and a diversity of contaminants – the potential consequences become even more complex.”

So far, the decline in Atlantic salmon numbers has largely been blamed on factors like overfishing and habitat loss. However, the study implies that pharmaceutical pollution could be subtly reshaping critical life events like the salmon’s migration.

Calls for better wastewater treatment

Addressing this issue may be daunting, since many medications do not degrade quickly in the environment and often slip through conventional wastewater treatment systems.

“Advanced wastewater treatment methods are becoming more effective at reducing pharmaceutical contamination, and there is promising potential in green chemistry approaches,” Michelangeli said.

“By designing drugs that break down more rapidly or become less harmful after use, we can significantly mitigate the environmental impact of pharmaceutical pollution in the future.” Indeed, this study underlines how such pollution can produce biological effects that reverberate throughout ecosystems.

Though improved wastewater practices and drug design might help, Michelangeli argued that the task ahead is to figure out how a multitude of chemicals, each at low concentrations, might collectively influence everything from fish migration to predator-prey dynamics.

“Pharmaceutical pollutants are an emerging global issue, with over 900 different substances having now been detected in waterways around the world,” Michelangeli said, emphasizing that efforts to reduce contamination could make a crucial difference for both animals and humans who share these water sources.

The future of Atlantic salmon

Ultimately, the story of clobazam and Atlantic salmon reminds us how connected we are to the world around us. Many people rely on medications for their well-being, yet each pill or patch might release chemical remnants into rivers and lakes far beyond our sight.

As the global usage of medications continues to rise, researchers hope to refine tools and strategies that can minimize these ecological footprints.

They believe that thoughtful design of medicines and advanced treatment systems could go a long way toward safeguarding species. This includes the Atlantic salmon and the wider tapestry of aquatic life that sustains our planet.

The study is published in the journal Science.

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