CORVALLIS, Ore. -- Researchers have discovered that a level of nitrogen-based compounds which the EPA says is safe for human drinking water a level often found in agricultural areas as a result of using crop fertilizers - is enough to kill some species of amphibians. A new study at Oregon State University, just published in the journal Environmental Toxicology and Chemistry, has shown that several frog, toad and other amphibian species, especially at their more vulnerable larval stages, can be highly susceptible to fairly low levels of nitrate and nitrite exposure.
When exposed to moderate amounts of nitrates and nitrites, some tadpoles and young frogs reduced their feeding activity, swam less vigorously, experienced disequilibrium, developed physical abnormalities, suffered paralysis and eventually died. In control tanks with normal water, none died.
"I think this is clearly a significant problem," said Andrew Blaustein, a professor of zoology at OSU and expert on global amphibian declines. "Right here in the Pacific Northwest we're having localized extinctions of some amphibians and widespread declines in others. We now have clear evidence that nitrate and nitrite exposure at levels considered safe for humans or fish is enough to kill amphibians."
Blaustein has done pioneering research on the potential impact of UV-B radiation in sunlight as one of the possible causes of amphibian problems. He now says that exposure to nitrogen fertilizers - along with habitat destruction, climate change, pollution, pathogens and introduced predators - is probably another part of the answer to an international mystery that has alarmed ecologists around the world.
But this latest part of the puzzle goes to the heart of crop agricultural practices, he said, which depend heavily on the use of artificial fertilizers rich in nitrogen to produce the world's food supply.