Many pharmaceuticals remain in the environment for long periods of time because they resist natural degradation and are unable to be removed by conventional treatment techniques.
In a major study published in the journal Science, an international team of scientists from Australia's Griffith University investigated the impact of pharmaceutical pollution on the behavior and migration of Atlantic salmon (Salmo salar).
Scientists found that hypnotics reduce the time required to cross two hydroelectric dams along the migration route, which is important because these artificial obstacles typically hinder successful migration. To track salmon behavior, the researchers used innovative, slowly released drug implants and transmitters attached to fish in the river. A laboratory experiment showed that various types of hypnotics alter the behavior of animals living in groups or schools, affecting social dynamics and risky behavior in the wild.
Drugs can disrupt natural processes, affecting not only the speed of migration but also social interactions between fish, their reproduction, and their feeding habits. These changes can disrupt the synchronization of life cycles, increase the vulnerability of fish populations at certain stages of migration, and even cause food chain disruptions.
“Pharmaceutical contaminants are a growing global problem, with more than 900 different substances currently detected in waterways around the world,” said Dr. Marcus Michelangelo, the project’s lead researcher.
He added that the problem is exacerbated by the presence of psychoactive substances such as antidepressants and painkillers, which can profoundly affect the brain functions and behavior of wild animals. He also noted that most previous studies were conducted in laboratory settings that do not reflect the complexity of the natural environment. He said, "If we look at realistic impact scenarios that affect entire ecosystems, involving multiple species and diverse pollutants, the potential consequences are extremely serious."
Although the decline in Atlantic salmon populations is primarily linked to overfishing, the study shows that water contamination with pharmaceuticals also affects important stages of their migration. Dr. Michelangelo explained that many pharmaceuticals remain in the environment for long periods because they do not decompose easily, and conventional wastewater treatment methods fail to remove them.