Largest study to date shows pharmaceutical pollution alters migration in Atlantic salmon

The researchers Daniel Cerveny and Marcus Michelangeli from SLU in Umeå are collecting juvenile salmon in the Dal River. The juvenile salmon formed the foundation of the study published in Science.

ImageMichael Bertram

Pharmaceuticals are present in most surface waters globally

Pharmaceuticals in aquatic ecosystems – a growing issue 

“The presence of pharmaceuticals in our surface waters has been studied for two decades now,” says Jerker Fick, Associate professor at the Department of Chemistry who contributed to the study published in Science. “Pharmaceuticals are present in most surface waters globally, often in low concentrations. However, there are hotspots, for instance near production facilities and in densely populated, water-scarce areas. On top of that, we also know that the usages of pharmaceuticals are increasing globally,” he says. 
 
Psychoactive pollutants, such as antidepressants and pain medications, are of particular concern, due to their ability to influence brain function and alter the behaviour of wildlife species.

“Almost all of the existing research into the effects of pharmaceutical pollution on wildlife has investigated the effect under simplified conditions in the laboratory that do not capture real-world complexity,” says Michael Bertram, Assistant Professor SLU, senior author of the study. Animal behaviour is very sensitive to environmental conditions, and behavioural effects of drug exposure seen in the laboratory may not be reflective of behavioural responses in the wild. 

Jerker Fick, researcher at the Deparmtent of Chemistry, contributed to the study with his expertise of measuring pharmaceutical pollutants using mass spectrometry.

ImageRebecca Forsberg 

Moving out of the laboratory 

The research team conducted the largest field-based study to date that investigates the effects of exposure to pharmaceutical pollutants. They used newly developed slow-release pharmaceutical implants and animal-tracking transmitters to investigate how exposure to clobazam – a drug often prescribed for sleep disorders – and the opioid painkiller tramadol affected the behaviour and migration of juvenile Atlantic salmon, Salmo salar. The study took place in the Dal River, Sweden, and looked at the salmon's migration to the Baltic Sea.
  
“We found that the salmon exposed to clobazam passed hydropower dams faster than the unexposed fish. It also meant that more of the medicated salmon eventually reached the Baltic Sea," says Jack Brand, researcher at SLU and first author of the publication, in a press release from SLU.
 
“Our results demonstrate the capacity for pharmaceutical pollution to influence key behaviours of animals in the wild, with potentially wide-ranging consequences”, he says in a press release from SLU.  

The dam in Älvkarleby, Uppland. The dam is one of the obstacles that juvenile salmon must navigate in the Dal River on their migration toward the Baltic Sea, and one of the two dams included in the study published in Science

ImageRebecca Forsberg

A way towards less-polluted wildlife 

Atlantic salmon are an ecologically, economically, and culturally important species that recently was classified as endangered by the International Union for Conservation of Nature (IUCN) in parts of Europe. While overexploitation (e.g., from fishing), habitat loss, and fragmentation are the primary drivers of this worrying trend, the results of this experiment suggest that pharmaceutical pollution may alter behaviours during events that are key for the survival in migratory fish.  
 
Nonetheless, pharmaceuticals play a key role in modern human and animal health and will remain important for disease management and prevention into the future.  

“However, most pharmaceuticals exhibit poor biodegradability, and wastewater treatment processes often fail to completely remove these substances,” says Professor Tomas Brodin, previously researcher at Umeå University, now at SLU and co-author of the study.

Jerker Fick, researcher at the Department of Chemistry, here with Tomas Brodin, researcher at SLU, co-author of the study, and previously a research at the Department of Ecology and Enviornmental Science, EMG. 

ImageMattias Pettersson

A multi-pronged approach will be required to mitigate the threat of pharmaceutical contaminants

Whilst several advanced wastewater treatment methods have been successful in reducing pharmaceutical contamination, they remain unavailable in many parts of the world due to economic and infrastructure reasons. 

“While addressing pharmaceutical pollution is not simple, it is clear that a multi-pronged approach will be required to mitigate the threat of pharmaceutical contaminants to wildlife health into the future,” says Michael Bertram. 

Jerker Fick concludes that these findings would have been much harder to obtain without the collaborative efforts of the large study: “It is very fulfilling to be able to collaborate with experts in different research fields and together investigate the effects of these pollutants.”