13 September 2006

Prozac In Wastewater Threatens Mussels

by Kate Melville

Wastewater carrying traces of the antidepressant Prozac is disrupting the reproductive cycle of mollusks, threatening them with extinction, according a study presented at the national meeting of the American Chemical Society.

The researchers explained that Prozac (fluoxetine) caused females to prematurely release their larvae, a case of bad timing that essentially dooms them. "The results from this study were quite alarming," said Rebecca Heltsley, from Hollings Marine Laboratory in Charleston, S.C. "When larvae are released too early, they are not viable, which only contributes to the problems faced by struggling populations of native freshwater mussels."

Mussels have the dubious distinction of being the most threatened animal group in North America.

About 70 percent of the nearly 300 species of freshwater mussels native to the continent are extinct, endangered or declining, according to Heltsley. In some cases, native mussels have been crowded out by invasive species, while others have been devastated by increased sediment loads in rivers, habitat alteration or killed off by pollutants.

"The presence of Prozac and similar drugs in U.S. rivers and streams has likely compounded the problem," Heltsley said. "It's a big concern because freshwater mussels are such an imperiled group."

To gauge the effect of the drug, the researchers placed female freshwater mussels carrying larvae into tanks containing laboratory water with varying concentrations of fluoxetine, the active ingredient in Prozac. The Prozac concentrations, which ranged from 0.3 to 3,000 micrograms per liter, mimicked those previously found in surface waters of lakes and streams. They also exposed a similar set of mussels directly to serotonin. Within 48 hours, the mussels in both groups had released their larvae prematurely.

Freshwater mussels play a key role in the ecology of rivers and streams, filtering large volumes of water for food each day, thereby helping filter contaminants and excessive nutrients from water and serving as an early warning of water quality problems. They also are an important source of food for muskrats, otters, fish and other animals. Worryingly, research conducted by other institutions had previously established that Prozac found in fish and frogs was shown to be slowing the development of these animals.

"Protecting freshwater mussels and other aquatic life that are susceptible to the unintended consequences of exposure to pharmaceuticals in our rivers and streams will take a concentrated effort," Heltsley said. "These efforts could include the development of more efficient wastewater treatment facilities that can filter out these products before they reach our waterways."

Source: American Chemical Society