Perch gone wild: Can drugs prompt a Great Lakes feeding frenzy?
By Kathiann M. Kowalski
Could mood-altering drugs force Great Lakes fish into a feeding frenzy?
A new study from Sweden’s Umeå University finds that fish eat faster and become bolder when exposed to a common anti-anxiety drug. That poses serious questions for the Great Lakes, where the presence of pharmaceuticals has been documented.
In the study, published last week in Science, researchers dosed European wild perch with oxazepam. Small amounts of the medication pass from patients’ urine into wastewater. Sewage treatment rarely removes pharmaceuticals from wastewater before they enter rivers and streams.
Like other anti-anxiety drugs, oxazepam alters people’s mood and behavior. It also affects fish behavior. The Umeå researchers exposed perch to low and high doses of the drug. Both groups ate significantly faster than a control group. They also became bolder and less sociable.
When asked about the study, U.S. Environmental Protection Agency officials questioned its relevance to the real world. The agency noted that the low-dose level was twice the level found in Swedish wastewater plant discharge. Nonetheless, study co-author Jerker Fick says, “We see a very strong, statistically significant effect at these levels. This is by no means the no-effect concentration.”
It could happen here
Oxazempam targets the brain’s receptors of a chemical messenger that reduces neurons’ activity. The receptors are present in almost all vertebrates.
“So all fish—perch in the Great Lakes and others—have these drug targets,” says Fick.
Oxazepam’s effects could present “grave consequences” for ecosystems, says study co-author Tomas Brodin. If fish eat more zooplankton, they could pave the way for algae blooms. And bolder, less sociable fish could stray from schools, increasing the risk of becoming another species’ supper.
“Start with a top-down effect, and once those things at the bottom of the food chain would change, it would trickle back up,” says Steve Mauro, a biologist at Mercyhurst University near Lake Erie. Predicting precise changes is difficult.
A 2012 report by the Alliance for the Great Lakes, a nonprofit organization dedicated to conserving and restoring the Great Lakes, echoes concerns about a drugged ecosystem. “Concentrations of these chemicals would tend to be higher in the nearshore areas, especially close to where wastewater effluents are being discharged,” says Olga Lyandres, the report’s author. “Nearshore areas are where a lot of spawning habitats are, so there’s a higher chance that the fish may be exposed.”
Drugs could stay in Great Lakes waters for a long time. Discharge points are all around the shore, but mixing in the middle occurs slowly. For Lake Michigan, says Lyandres, “It takes a century for the water to cycle through the lake.”
More drugs, more effects
Scientists in the Great Lakes region already know that another mood-altering drug, fluoxetine, affects fish behavior. Fluoxetine is the generic version of the anti-depressant Prozac.
Fathead minnows normally follow an elaborate nesting and mating ritual. “This whole dance gets disrupted” when the fish are exposed to fluoxetine, says Rebecca Klaper at the University of Wisconsin—Milwaukee’s School of Freshwater Sciences. Lower libido is a possible side effect for humans, too.
Disrupting reproduction could lead to fewer fish. The fathead minnow is often used in toxicology studies because drugs that disturb them likely affect other fish, Klaper says
Fluoxetine can also kill E. coli and other bacteria at the bottom of the food chain, reports Mauro. “Without bacteria, you have less overall phytoplankton, and you have less food sources for those other organisms.”
Fewer bacteria could also confound water quality assessments. “We may think it’s safe water when in fact it has a bunch of chemicals in it,” says Mauro.
Of course, these medicines aren’t the only ones out there. U.S. Geological Survey hydrologist Kathy Lee and other scientists have found “a broad scope” of prescription and over-the-counter drugs in waters of the Great Lakes region. “It’s not surprising, given that people take medications and excrete them,” Lee says.
Those drugs’ effects can vary widely. For example, birth control pills and other hormones could disrupt endocrine systems. In some cases, fish develop both male and female characteristics, notes Klaper.
Antibiotics also cause concern. “They might be screwing up the bacterial communities and might cause increased antibiotic resistance,” Klaper says. Common cholesterol medicines and other drugs add to the brew. “It’s a very low concentration soup—but a soup out there of chemicals,” says Klaper.
Low concentrations of such chemicals may interact with each other in unexpected ways. One of Mauro’s experiments combined fluoxetine with triclosan—the active ingredient in many bacterial products. Together, they were “much more effective at killing microbes” than either one alone.
“We probably don’t want to panic just yet,” says Mauro. “But it’s really good that we are being proactive and taking a look at these things.” Learning more about low-dose drug impacts now can help set priorities for better sewage treatment in the future.