Imagine you are a perch. One day you notice that all the other perch around you are acting different. Previously timid and communal—as the species has been for millennia—they’ve become foolhardy, leaving the safety of the school to search alone for bits of zooplankton to eat, practically daring the birds and bass that prey on them to attack. In short, they’ve gone nuts.
Being a fish, you would not be terribly introspective, and in any event, it would be beyond your abilities to imagine the cause: that another species, one that lives, improbably, on land, suffers from problems called “anxiety” and “depression” because of its enormous brain (among other things). That animal has taken to eating exotic chemicals to change its behavior. It then excretes those chemicals into the water that you breathe so that you, too, are ingesting those chemicals. And they’re changing your behavior.
It’s not news that human beings dump a lot of stuff into lakes and rivers. The evidence is all around us—massive blooms of algae from fertilizer runoff, stunted fish and dead waterfowl from mine tailings, and oil spills. But that is stuff we’re used to thinking about as pollution, and they’re the sort of effects—die-offs and deformity—that we’re used to worrying about. What about the stuff we actually put into our own bodies? What effect does that have when it gets out into the world? And what happens to a species—or, for that matter, an entire ecosystem—when we put it on drugs?
In a paper published Thursday in Science, a team of Swedish researchers tried to provide at least part of an answer. They first tested various Swedish bodies of water for the levels of an anti-anxiety drug called oxazepam—like many drugs, oxazepam doesn’t get filtered out by sewage treatment plants. In a lab, the researchers then placed wild European perch in tanks with comparable drug levels. The researchers found that the drugs were, indeed, having an effect: Even at dosages at the lower end of what they found in the wild, the fish in the oxazepam tanks were less social than those in the control tanks. The drugged fish put more distance between themselves and other fish, and they ate faster than normal. At higher dosages, the researchers also found an increase in what they termed “boldness,” the lack of hesitation with which the fish entered an unfamiliar area.
“We were very surprised,” says Jonatan Klaminder, an environmental scientist at Umea University and one of the co-authors of the paper. “The concentrations out in the environment are very low, but it’s still enough to generate effects that we know are relevant for ecological processes.” He adds that most of the behavioral changes they found were, from the point of view of each fish, actually productive: The fish feed at a faster rate, they become more active. “They actually perform better,” he said. For perch, at least, putting oxazepam in a river is a bit like putting Adderall in the water supply of a college dorm (or cocaine in Charlie Chaplin’s salt).
However, in the lab there weren’t any predators. And as Klaminder and his co-authors point out, oxazepam-dosed perch, swimming around blithely in the wild by themselves, are probably at higher predation risk. Also, the fact that the drug makes them eat so ravenously could throw their environments out of whack. The plankton that perch eat in turn eat algae, and if the perch ate up all the plankton the algae would run rampant, choking off the rest of the life in the area.
As Klaminder underlines, he and his fellow researchers only looked at one fish and one drug. But ecosystems are full of plants and animals that react to chemicals in different ways, and our rivers and lakes are increasingly full of a crazy cocktail of pharmaceuticals—from Prozac to the estrogen from birth control pills—many of which doctors would probably hesitate to prescribe together. Rebecca Klaper, an ecologist at the University of Wisconsin, Milwaukee, is one of the few other researchers to have done work on fish and psychopharmaceuticals—her research is on fathead minnows and fluoxetine, the active ingredient in Prozac. She found that fluoxetine in the water didn’t affect the females, but made the males essentially obsessive-compulsive (a condition, interestingly enough, that Prozac is prescribed for in humans). The males spend an unusual amount of time building their underwater nests. When the amount of fluoxetine was increased, the males started ignoring the females. When the dosage was increased still further, the males killed the females.
According to Klaper, the problem of drugs in our waterways doesn’t have an easy solution—upgrading all of the water treatment plants in the world would be an enormous expense, and we still don’t have the technology to filter many pharmaceutical compounds out of the water. Still, she points out, we can take some encouragement from the fact that many compounds don’t actually have an effect at the sort of concentrations they’re found today in lakes and rivers. “There are medications that probably we don’t need to be as worried about,” she says. “We should focus on finding out which ones are of most concern.” In the meanwhile, as a species we might think about getting our own prescription drug issues under control. The rest of the animal family is getting concerned.