-- Jay DeLong Olympia, WA
Fertilizers Take Toll on Frogs By Bryn Nelson Newsday
In the latest chapter of a global whodunit involving shrinking populations, Oregon researchers have named the nitrogen-based compounds found in fertilizers likely suspects in the rapid decline of at least one frog species in the Northwest.
Although fertilizers join a lineup of many other potential villains, including habitat destruction, climate change, pollution, and introduced predators, the new research suggests that even chemical levels considered safe for humans can devastate entire amphibian populations.
"We have to be aware of our drinking water," said Andrew Blaustein, a professor of zoology at Oregon State University and the study's lead author. "We have to understand that there are things in our drinking water that are considered safe for us but that are killing some amphibians."
For the study published last month in the journal Environmental Toxicology and Chemistry, Blaustein's team took eggs from several amphibian species found in the west and placed the emerging tadpoles in tanks filled with water, most of them containing varying levels of nitrate and nitrite compounds.
After 15 days of exposure, the researchers calculated that a nitrite concentration of 1 milligram per liter, the maximum recommended limit for drinking water, was sufficient to kill about half of the northwestern salamander tadpole and well over half of the Oregon spotted frog tadpoles. Blaustein said that since amphibians can easily absorb the dangerous nitrites through their permeable skin, they represent sensitive indicators of environmental stress.
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