With all the illegal drugs being flushed down toilets across the world, their effects are increasingly being passed on to non-humans, resulting in major disruptions to food chains and ecosystems in rivers and other aquatic environments. It all goes to show that everything really is interconnected, and that our actions always have repercussions across the natural world.
Discussing their work in the journal Environmental Science and Technology, researchers analyzed drug residue in six different streams in Baltimore, finding a wide array of different substances, including several illegal narcotics. Among the banned drugs detected were the likes of MDMA, methamphetamine (also known as crystal meth), and amphetamines.
To determine how this impacts local ecosystems, the team then created artificial streams in a laboratory, to which they added amphetamine. Used as a stimulant, amphetamine – sometimes called speed – is metabolized by the body after ingestion, although around 30 to 40 percent of the original compound is excreted in urine, often finding its way into the sewage system before ending up in lakes and rivers.
The study authors discovered that, compared to those lacking in amphetamine, streams that were treated with the drug produced up to 85 percent less biofilm, which is an organic slime found on the surface of rivers that provides the bottom rung of the food chain. They also found that seston – the collection of living and dead organisms floating in the water – increased by 24 percent, although the fact that seston respiration decreased by 30 percent suggests that much of this extra material was in fact dead.
Amphetamine also disrupted the composition of bacterial and algal populations, causing a massive boom in certain bacteria such as Cloacibacterium while others like Luteimonas dropped significantly. Interestingly, the presence of amphetamine in the water led to a huge rise in the number of certain insects, including flies and midges. As such, the study authors suspect that illegal drugs in streams are likely to make their way into dry-land food chains as well, as many of these aquatic insects are preyed on by animals that live on or near the riverbank.