Wind And Rain Spreading Pesticides Beyond Farmland
July 27, 2013

Pesticides Found In Wild Frogs Brought By Wind And Rain

Brett Smith for - Your Universe Online

For years, conservationists have been warning about the potential seepage of agricultural chemicals into the ecosystem and a new report from researchers at the US Geological Survey has found evidence of pesticides in Pacific chorus frogs living miles away, but down wind, from California farmlands.

The report, which was published in the journal Environmental Toxicology and Chemistry, supports previous research that has found evidence of pesticides being transported by the forces of wind and rain.

"Our results show that current-use pesticides, particularly fungicides, are accumulating in the bodies of Pacific chorus frogs in the Sierra Nevada," said co-author Kelly Smalling a research hydrologist and organic chemist from the USGS. "This is the first time we've detected many of these compounds, including fungicides, in these remote locations."

In the study, the team collected water and sediment samples along with frogs from seven ponds ranging from Lassen Volcanic National Park in northern California to the Giant Sequoia National Monument in the central part of the state. All of the collection sites in the study were downwind of agricultural areas.

"The samples were tested for 98 types of pesticides, traces of which were found in frog tissues from all sites," Smalling said. "We found that even frogs living in the most remote mountain locations were contaminated by agricultural pesticides, transported long distances in dust and by rain."

Two commonly used fungicides, pyraclostrobin and tebuconazole, and the herbicide simazine were the most commonly found chemicals in the study. The authors noted this was the first time these pesticides have ever been detected in tissue samples taken from wild frogs.

The researchers also found Dichlorodiphenyldichloroethylene (DDE), a broken down form of the insecticide DDT that was banned in 1972. The presence of DDE suggests just how long DDT can remain in an ecosystem and potentially have an impact on organisms living there.

By comparing frog, water and sediment samples, the scientists found frog tissues were a fairly reliable indicator of chemical exposure. The study authors theorized this was probably due to the physical-chemical properties of the compounds and various biological factors.

Smalling said documenting the dispersal compounds is an important first step in determining their impact on the larger ecosystem.

"Very few studies have considered the environmental occurrence of pesticides, particularly fungicides which can be transported beyond farmland," she concluded. "Our evidence raises new challenges for resource managers; demonstrating the need to keep track of continual changes in pesticides use and to determine potential routes of exposure in the wild."

The study findings are significant in that California's Central Valley represents one of the most heavily farmed regions in North America, producing eight percent of US agricultural output. California is also known to use more pesticides than any other state.

While Pacific chorus frogs are not considered endangered, they do serve as a crucial indicator for how organisms are taking in agricultural chemicals. Pesticides are known to compromise the immune system of the amphibians - making them more susceptible to infection.