Fish on Drugs: The Mellowing of Minnows and Other Consequences of Antidepressants in the Water
Knopper, Melissa, E Magazine
Back in the 1990s, Theo Colborn, then-senior scientist with the World Wildlife Fund, sounded the first alarms about endocrine disrupters. In the book Our Stolen Future (Plume) Colborn describes her early findings that connected these endocrine disruptors--via chemicals in plastics, pesticides and pharmaceuticals--with male fish laying eggs and bald eagle eggs crumbling into tiny pieces. Soon, scientists developed new research techniques to study these estrogen-like compounds, which are highly active at trace levels. Now, those new research tools are putting the spotlight on an extremely persistent, and perhaps equally disruptive, group of contaminants: antidepressants.
A new body of evidence is building. Study after study shows widely prescribed drugs such as Prozac, Effexor and Celexa disrupt the natural order when they are excreted into the water. Scientists in Mississippi discovered antidepressants are interfering with the way tadpoles develop into frogs. They also interfere with the ability of tiny minnows to escape predators. Experts say these early signs could point to long-term problems for the aquatic food chain as a whole.
Edward Z Furlong, Ph.D., a research chemist for the United States Geological Survey's (USGS) National Water Quality laboratory in Denver, Colorado, says the reasons antidepressants wreak havoc on fish is because they work on the body's serotonin system. Most organisms on Earth have this important neurotransmitter in their bodies, from the tiniest nematode (microorganisms in soil) to the largest mammals and humans. Once antidepressants disperse in the environment (in this case by traveling down streams in wastewater effluent), they can affect a wide range of living creatures.
In fish, Furlong explains, serotonin is associated with aggression, predation and escape instincts. "The fish is in water continuously," he says, "so dissolved antidepressants can cross the gills 24/7."
USGS scientists wanted to learn more about how these compounds--found in both water and sediment--might affect fish behavior. One 2010 study produced a surprising discovery: The antidepressants most common in stream water were not the ones that showed up in fish brains. "There are many reasons why this selective uptake may occur--including differences in fat versus water solubilities of the antidepressants," Furlong says.
So what happens when fish have antidepressants in their brains? Just like people, they mellow out. Some studies showed striped bass that uncharacteristically didn't pursuse smaller fish. Another important finding showed tiny fathead minnows who neglected to swim away when threatened by a simulated predator.
Dana Kolpin, a researcher with the USGS Toxic Substances Hydrology Program, says that minnows usually react to predators with what is a called a C-start mechanism. …