Higher temperatures may reduce effects of antidepressant pollution on wildlife.

Studies in recent years have established that pharmaceuticals that end up in the environment after human use can affect wildlife. Both Melbourne and Sydney are known to have high concentrations of drugs in their rivers. 

But a new study led by Monash University biologists has found that higher temperatures may reduce effects of antidepressant pollution on wildlife.

Researchers have studied the effects of fluoxetine, the active ingredient of the commonly prescribed antidepressant Prozac, and whether these effects change when temperature is increased.

Lead study author Lucinda Aulsebrook says fluoxetine is being increasingly found in low concentrations in waterways and lakes, due to being discharged from sewage treatment systems.

“Scientists have discovered many effects of the drug on wildlife but have often overlooked how these effects may depend on other factors in the environment,” Ms Aulsebrook says.

“In natural ecosystems, animals are not just experiencing pharmaceutical pollution, but many different stressors – both natural and man-made.

“Climate change is resulting in increasing temperatures worldwide, so we need to consider how this may be affecting wildlife in conjunction with pollutants such as fluoxetine.”

Ms Aulsebrook and her colleagues investigated how tiny aquatic crustaceans called water fleas (Daphnia magna) were affected by both fluoxetine and temperature increases.

The research found that exposure to environmentally realistic concentrations of fluoxetine – just 30 nanograms per litre – resulted in changes in body size and offspring production in the water fleas at 20°C. When the temperature was increased to 25°C, however, these effects were no longer present.

“This really demonstrates how important it is to consider all the different factors present in the environment,” Ms Aulsebrook said.

“An increase of just 5°C was sufficient to dramatically reduce the impact of fluoxetine.

“Our research highlights the fact that the documented effects of any chemical pollutant may be context dependent, and many different variables can influence the results.”