A study conducted in Sweden, published in the journal Science, revealed that the presence of clobazam, a common anxiolytic drug, in rivers has generated significant changes in the migratory behavior of wild Atlantic salmon.
This finding highlights the impact of pharmaceutical contamination on aquatic ecosystems.
Researchers found that salmon exposed to clobazam were less risk-averse and were more likely to complete their migration to the sea. They were able to overcome artificial barriers, such as hydroelectric dams, at a faster rate than non-exposed salmon.
Jack Brand, lead author of the study and a member of the Swedish University of Agricultural Sciences, warned that, although this may seem positive, the alteration of natural behaviors could have unexpected ecological consequences.
Pharmaceutical Pollution in the World’s Rivers
Various studies have detected medications in bodies of water on all continents, including in Antarctica. Nearly a thousand active pharmaceutical ingredients affecting biodiversity and ecosystem balance have been identified.
Medications enter the water through:
- Treated or untreated wastewater.
- Waste from animal husbandry and veterinary clinics.
An experiment in Canada in 2006 showed that synthetic estrogens from contraceptive pills caused the feminization of male fish, affecting reproduction and leading to the collapse of certain populations.
Alterations in Salmon Dynamics
In the study, researchers tracked 279 salmon in the Dal River, using telemetry devices and a clobazam implant. They found that salmon exposed to the drug migrated faster, which could be related to a modification of their social behavior.
Laboratory experiments also revealed that schools of fish were less cohesive in the presence of predators, which increases risks for the fish.
Ecological Consequences and Future Research
The researchers monitored the salmon for 10 days, but it is still unknown if the effect of clobazam persists in the Baltic Sea or affects their reproduction when they return to the river.
Josefin Sundin, an ecologist at the Institute of Freshwater Research in Drottningholm, Sweden, emphasized that while many drugs have shown effects on animal behavior, more research is needed to understand their long-term impact.
Pharmaceutical Pollution in the Food Chain
Recent studies indicate that drugs can travel through the entire food chain, affecting not only fish but also land animals that consume contaminated insects or fish.
This discovery underscores the urgency of addressing pharmaceutical contamination, ensuring better management of medical and agricultural waste to protect aquatic ecosystems.
