The Associated Press State & Local Wire
January 5, 2000, 

DATELINE: CORVALLIS, Ore.

Fertilizer levels, the Environmental Protection Agency say, that are safe for human drinking water can kill some species of frogs and toads, according to a new study.

Oregon State University researchers found some tadpoles and young frogs raised in water with low levels of nitrates (typical of fertilizer runoff) ate less, developed physical abnormalities, suffered paralysis and eventually died.

In control tanks with normal water, none died.

"We're looking at levels of nitrates so low we didn't think we'd get any effect," said Andrew Blaustein, a zoology professor and expert on global amphibian declines.

In addition, the fertilizer runoff may be encouraging the growth of algae that feeds tiny parasitic flatworms called trematodes, blamed for causing deformities in frogs around the United States.

"So there are two effects. One is a direct effect, the fertilizer can kill them outright," Blaustein said of the frogs. "And two, it increases algal growth that leads to more parasites that cause deformities."

The study indicates that EPA water quality criteria does not guarantee the survival of some protected and endangered amphibians, he said.

"I think this is clearly a significant problem," Blaustein said. "The question I have to ask is, are you comfortable drinking water with levels of fertilizer that kills off frogs?"

Officials at the Environmental Protection Agency regional office in Seattle said they could not comment until they have reviewed the Oregon State study, published last month in the journal Environmental Toxicology and Chemistry.

"It sounds like an interesting study," said Mark MacIntyre, EPA spokesman.

"Obviously we're concerned about nitrates in the water, but until we get the guy to come up here and present the study, there's not much we can say."

Nels Granholm, a biologist at South Dakota State University, said the Oregon frog deaths are cause for concern because they are a sensitive "indicator" species that can signal an environmental shift or pollution problem.

"There are problems with frogs all over the world," Granholm said.

"The problem with studies like Blaustein's is that people don't want to recognize the danger," he said. "The human being somehow has this incredible ability to foul its nest."

The Oregon State researchers studied five species of amphibians, including the Oregon spotted frog, red-legged frog, western toad, Pacific tree frog and northwestern salamander.

In the past 40 years the Oregon spotted frog has largely disappeared from most of its known historical range, a lowland area now heavily farmed.

The spotted frog was the most sensitive - three to four times more vulnerable to nitrates and nitrites than red-legged frogs and Pacific tree frogs. Levels of nitrites considered safe for human drinking water killed over half of the Oregon spotted frog tadpoles after 15 days of exposure.

All five species of amphibians were affected by higher nitrite levels that were still well below those that the EPA considers safe for warm water fish.

Nitrite levels can become higher in specific areas such as shorelines with high contents of organic matter, and also can be concentrated by ranch animal manure.