Drug Pollution Is Passing From Stream Bugs to Predators

In the streams studied, platypus and brown trout also feed on aquatic insects. By pairing concentrations of pharmaceuticals found in stream insects with known dietary needs of platypus and trout, the team was able to estimate their drug exposure. (Image: via pixabay / CC0 1.0)
In the streams studied, platypus and brown trout also feed on aquatic insects. By pairing concentrations of pharmaceuticals found in stream insects with known dietary needs of platypus and trout, the team was able to estimate their drug exposure. (Image: via pixabay / CC0 1.0)

Sixty-nine pharmaceutical compounds have been detected in stream insects, some at concentrations that may threaten animals that feed on them, such as trout and platypus. When these insects emerge as flying adults, they can pass drugs to spiders, birds, bats, and other streamside foragers. These findings by an international team of researchers were published in Nature Communications.

Erinn Richmond collects aquatic invertebrates to test for pharmaceuticals in Brushy Creek in Churnside Park, Victoria, Australia. (Credit: Keralee Browne)

Erinn Richmond collects aquatic invertebrates to test for pharmaceuticals in Brushy Creek in Churnside Park, Victoria, Australia. (Image: Keralee Browne)

Pharmaceutical pollution is present in surface waters globally. Drugs enter the environment because most wastewater treatment facilities are not equipped to remove them from sewage. Septic tanks, aging pipes, and sewer overflows contribute to the problem. Emma Rosi, an aquatic ecologist at Cary Institute of Ecosystem Studies and a coauthor on the paper, explains:

Surveying pharmaceuticals in streams

The team sampled six streams in Melbourne, Australia, for 98 pharmaceutical compounds — the most exhaustive screening to date. Pharmaceuticals measured included common drugs like antibiotics, antidepressants, antihistamines, and NSAIDs.

Starting with filter-feeding insects, pharmaceutical compounds in stream water accumulate in aquatic organisms' tissues. This means that animals that eat aquatic insects, like platypus, get a dose of pharmaceuticals with their meals. (Credit: Denise Illing)

Starting with filter-feeding insects, pharmaceutical compounds in stream water accumulate in aquatic organisms’ tissues. This means that animals that eat aquatic insects, like platypus, get a dose of pharmaceuticals with their meals. (Image: Denise Illing)

Study sites were selected along a gradient of wastewater contamination that included a site downstream of a wastewater treatment plant and a site in a national park. Aquatic insects and riparian spiders were collected. Erinn Richmond, a freshwater ecologist at Monash University in Australia and lead author on the study, explains:

Bugs on drugs

Tissue analyses detected up to 69 different pharmaceutical compounds in aquatic insects and up to 66 compounds in riparian spiders. Drug concentrations were the highest in invertebrates collected downstream of wastewater treatment facilities or in heavily populated areas with potential septic tank leakage.

On average, pharmaceutical concentrations at these sites were 10 to 100 times higher than less contaminated sites. Coauthor Jerker Fick, a chemist at Umeå University in Sweden, analyzed the insect and spider samples.

Richmond noted that:

Top predators are at risk

In the streams studied, platypus and brown trout also feed on aquatic insects. By pairing concentrations of pharmaceuticals found in stream insects with known dietary needs of platypus and trout, the team was able to estimate their drug exposure. Rosi explains:

Next steps

The caddisfly, a globally common aquatic insect, was among those tested in this study. Richmond says:

Rosi concludes:

Provided by: Cary Institute of Ecosystem Studies [Note: Materials may be edited for content and length.]

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