Now two new studies cast serious doubt on that assumption, and the lead author of one says the belief could have had negative impacts on efforts to save amphibians.

"All of the concentration on UV might have misdirected our conservation and research priorities," said Wendy Palen, a University of Washington zoology doctoral student.

UV-B, which causes a number of damaging photochemical changes within cells, makes up less than 1 percent of the ultraviolet radiation reaching the Earth's surface. Previous laboratory and field experiments have shown that it causes deformities and increased mortality in amphibian embryos. That finding led some scientists to contend the Earth's thinning ozone layer, which protects the planet from some harmful radiation, might have contributed to declining amphibian populations.

However, Palen said, the previous experiments, both in the laboratory and in the field, dealt with individuals or small groups in carefully prepared settings. A critical limitation of those studies has been in understanding whether results of small-scale experiments are representative of the range of environments amphibians experience in nature.

The new study examined UV-B levels in natural amphibian breeding habitats in Washington and Oregon and found that the amount of dissolved organic matter in the water actually protects most amphibian embryos from harmful levels of UV-B radiation.

The study is published in the November issue of the journal Ecology. Besides Palen, authors are Daniel Schindler, a UW associate zoology professor and Palen's doctoral adviser; Michael Adams, Christopher Pearl and R. Bruce Bury of the U.S. Geological Survey; and Stephen Diamond of the U.S. Environmental Protection Agency. The USGS, th
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Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
5-Dec-2002