Twelve years ago, a class of Minnesota schoolchildren discovered a pond where over half the frogs had extra or missing legs. Since then, deformed frogs have been found with baffling -- and alarming -- frequency in waters across the country.
The theories are many. Maybe the frogs were sensitive to ultraviolet light streaming through a thinned ozone layer. Maybe pesticides were to blame. Maybe it was fertilizer runoff.
Of the various explanations, fertilizers have taken the lead: several years ago, Stanford University biologists discovered that deformed frogs were infected with parasites called trematodes that interfere with normal limb development. Trematodes spend part of their lives on freshwater snails, which thrive in water with high levels of nitrogen and phosphorous -- and such waters are produced by runoff from fertilizers, both residential and agricultural.
Those findings are supported by a study, published in the Proceedings of the National Academy of Sciences, in which University of Colorado at
Boulder biologists built 36 artificial ponds and added snails. Ponds with high fertilizer runoff saw their snail populations boom.
So what can you do if you want to give kids a chance to catch frogs that don't have legs between their eyes? Use nitrogen- and phosporous-free fertilizers in your own garden, and try to buy organically grown produce.
Runoff Blamed for Jump in Deformed Frogs [Associated Press]
Aquatic eutrophication promotes pathogenic infection in amphibians [PNAS]
Image: Penn State University
