Because UV-B has been shown in field and laboratory experiments to cause deformities and increased mortality in amphibian embryos, some scientists have contended that increases in UV-B from thinning of atmospheric ozone have contributed to declines of frog populations worldwide. However, one of the shortcomings of this earlier research has been a lack of knowledge about the actual exposure of amphibians to UV-B in their natural habitats. The research presented in the journal Ecology sheds light on UV-B as a factor in amphibian declines.
According to USGS research ecologist Michael Adams, "This is only the second study to look at how the distribution of amphibians relates to potential UV-B exposure. Most previous studies only addressed physiological effects of UV-B but did not provide evidence that any negative effects translated into population losses."
Research by Adams and his colleagues showed that dissolved organic matter in the water absorbs UV-B in amphibian habitats and protected 85 percent of the amphibian habitats the researchers sampled.
This study sampled 136 potential amphibian-breeding sites in the Olympic Mountains of Washington and the Cascade Mountains of Oregon and measured how well UV-B could penetrate the water. The levels of dissolved organic matter found in this study were high enough to protect the majority of amphibian populations from the levels of UV-B that are known to be harmful to amphibians.
The second study, which began in 1986, discussed the breeding behavior of boreal chorus frogs at a pond in the Front Range of the Rocky Mountains west of Fort Collins, Colo
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Contact: Ruth Jacobs
ruth_jacobs@usgs.gov
541-750-1047
United States Geological Survey
3-Dec-2002