TitleCombined effects of UV-B, nitrate, and low pH reduce the survival and activity level of larval cascades frogs (Rana cascadae)
Publication TypeJournal Article
Year of Publication2000
AuthorsHatch, AC, Blaustein, AR
JournalArchives of Environmental Contamination and Toxicology
Type of ArticleJournal Article

We investigated interactions between low pH, high nitrate level, and ultraviolet-B (UV-B) Light on the survival and activity level of larval Cascades frogs (Rana cascadae). We used a fully factorial experimental design, with pH levels of 5 and 7; initial "pulse" nitrate exposure levels of 0, 5, and 20 mg/L; and W-B present or absent. After a 3-week laboratory exposure, we measured survival and activity level of the larvae. The experiment was repeated two times, in two separate years. Similar effects on survival and activity level were observed in both experiments. R. cascadae survival was not significantly reduced in treatments with individual factors atone (i.e., UV-B control, pH 5 control, or high nitrate level without pH or UV-B). However, in experiments from both year;, survival and activity levels of larval R. cascadae were significantly reduced in the treatment with low pH, high nitrate, and W-B together. In both years, analysis of variance (ANOVA) indicated that pH and nitrate had the greatest effect on survival and that UV-B and nitrate had the greatest effect on activity level. additional effects were observed in the 1998 experiment on both survival and activity level. In 1998, UV radiation and the interaction term between pH and nitrate (pH x nitrate) had a significant effect on survival. Also in the 1998 experiment, activity level was significantly reduced in treatments at neutral pH with UV, at initial nitrate doses of 5 and 20 mg/L and at neutral pH without UV at an initial nitrate dose of 20 mg/L. We suggest that the adverse effects were due to the multiple stressors acting together.

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