Radiocesium concentrations and DNA strand breakage in two species of amphibians from the Chornobyl exclusion zone

University of Georgia, Savannah River Ecology Laboratory, P.O. Drawer E, Aiken, SC 29802, U.S.A.

Abstract

Relatively few studies have considered impacts of the 1986 nuclear accident at Chornobyl on lower vertebrate populations. Amphibians are recognized as sensitive indicators of environmental degradation and pollution, and some amphibian population declines may be associated with contaminant-induced stress. Amphibians also utilize both aquatic and terrestrial habitats, which facilitates comparison of radionuclide accumulation and effects in different environments. We sampled sympatric frog species from a highly contaminated area within the Chornobyl exclusion zone and from a nearby, less contaminated area in August - September 1999. Radiocesium was measured in whole frogs and in muscle samples. Whole body mean radiocesium for Rana esculenta from Gluboke Lake, a highly contaminated area, was 22.3 Bq/g wet mass; R. terrestris from the same area contained 53.4 Bq/g wet mass. Radiocesium levels in frogs from Emerald Camp, a less contaminated area, were about an order of magnitude lower. In both locations, whole body radiocesium concentrations were higher in R. terrestris than in R. esculenta, probably reflecting dietary differences between species. Mean muscle radiocesium concentrations were generally lower than whole body concentrations, and muscle and whole body concentrations were highly correlated within individuals. We used pulsed field-gel electrophoresis to examine the size distribution of DNA fragments in muscle tissue from a subsample of R. terrestris from both locations. Increased proportions of smaller DNA fragments, suggesting DNA strand breakage, occurred in R. terrestris from the more contaminated location. Results support the concept that amphibians are useful in assessing radionuclide accumulation and effects in contaminated areas. However, differences among species must be considered in evaluating contaminant concentrations and potential effects.