Fish in water contaminated with anti-anxiety drugs turned from fearful swimmers afraid to explore outside the safety of their school into greedy loners, a change scientists say could upset the environment.
In a study published today in the journal Science, Swedish scientists observed the effects of the drugs on usually shy and timid freshwater perch. Affected fish would rush to gobble up food, instead of waiting to eat with their kin, and swim bravely into the darkest corners of the fish tank.
The altered behavior may have broad and unforeseen effects on ecosystems, according to the research group from Umea University in northern Sweden. The researchers exposed wild European perch to similar levels of the anti-anxiety medicine oxazepam, a commonly prescribed benzodiazepine from a class of tranquilizers that includes Xanax and Valium, as those found in a Swedish river.
“Just the fact that the low concentration of drug that we find in the waterway today affects fish should alarm people,” lead author Tomas Brodin, an ecologist at Umea, said in an interview. “There are ecological consequences that could affect ecosystems.”
Brodin and his team looked for benzodiazepines in water from the Fyris river, a waterway that winds through Uppsala, Sweden, and into which treated wastewater empties. They found oxazepam. Then they exposed young perch to two different concentrations of the same drug and watched the effects on the fish’s sociability, boldness and activity.
Videos of the results are startling. Fish not exposed to the drug huddled close to other fish in the tank, which would be expected in a species that swims in schools. After exposure to the anti-anxiety drug, the perch kept their distance.
Perch on oxazepam swam boldly into a new tank, even peeking into flower pots placed in the corners. Un-medicated fish wouldn’t even enter the unfamiliar space.
Fish au naturel stayed almost motionless while food was dropped into its tank, not daring to approach while bits drifted to the bottom. A drugged fish, though, darted at the food, grabbing it before it fell halfway down the tank.
The shy perch’s transformation into Mr. Hyde might be due to stress reduction.
“These fish are never unstressed,” Brodin said. “These small fish are constantly afraid of being eaten.”
All those changes may spell consequences for the ecosystem, the researchers concluded. Braver perch may be more likely to be eaten by predators. And greedy perch might lead to a higher risk of algal blooming by depleting algae-eating zooplankton.
“These drugs are all over the world, so it’s a global issue,” Brodin said. “It more than likely will affect all fish.”
The study is an important extension of research to look at subtle, non-lethal effects of pharmaceutical pollution, said Patrick Phillips, a hydrologist with the U.S. Geological Survey in Troy, New York. Scientists had been curious to see how fish would respond to benzodiazepines because the drugs are commonly found in surface water, Phillips said in a telephone interview.
Pharmaceutical pollution can make its way into the water either from industrial or human waste. In Sweden, oxazepam probably got into the Fyris river after people flushed pills down the toilet or through drug residue in excretions, he said.
“We need to be aware that this can occur,” Phillips said. “It may be that in some settings these kinds of discharges aren’t as big of an issue and in other areas they are.”
In any case, people shouldn’t stop taking their medicines because they’re afraid of their effects on fish, said Joakim Larsson, an associate professor at the University of Gothenburg who has published research on how antibiotics pollution in Indian rivers may lead to drug-resistant bacteria. Rather, the solution is better sewage treatment, Larsson said in a telephone interview.
“It really tells us that we need to look more carefully at the effects of these other pharmaceuticals,” Larsson said. “We can’t just look at whether they kill organisms. They won’t. They aren’t made to kill organisms. But they could have other subtle effects that could be of ecological importance.”
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