Ecology: Pharmaceuticals appear in Australian river food webs

Over 60 pharmaceutical compounds have been detected in aquatic invertebrates and riparian (riverbank) spiders from six streams near Melbourne according to a study in Nature Communications. The authors suggest that pharmaceuticals are transferred to spiders when they eat invertebrates. Preliminary estimates suggest that platypus and brown trout - at the top of the stream food webs - could, in principle, be exposed to certain drugs in their diets at up to 50% of levels prescribed for human doses.

Chemicals that humans use every day, such as medicines and personal care products, end up in nearby watersheds because they are not effectively removed by wastewater treatment. However, their biological activity, exposure and ecological effects remain poorly understood.

At six streams near Melbourne, Australia, Erinn Richmond and colleagues tested aquatic insects and terrestrial spiders for concentrations of 98 different pharmaceuticals, including antidepressants, pain killers, antibiotics, and antihistamines. The authors found that both insects and spiders contained detectable concentrations of over 60 chemicals. The concentrations were much higher in the riparian spiders, known predators of the insects, suggesting that the chemicals had ‘biomagnified’, or increased in concentration at higher levels in the food chain.

The authors then used the information on chemical concentrations in insects to estimate the pharmaceutical exposure of other insect predators in the food web: brown trout and platypus. Based on their calculations, the authors estimate that platypus could be ingesting approximately 50% of the recommended daily human dose of anti-depressants.

Further work is needed to explore the direct effects of these novel aquatic contaminants.