Global decline of amphibians has been a hot issue in recent years. A new paper by UGA scientists in Environmental Toxicology and Chemistry suggests that atmospheric deposition of mercury in aquatic habitats has the potential to have significant impacts on amphibians in the larval stage of development. Mercury may cause increased incidence of death and malformations and affect the regulation of growth, development and timing of metamorphosis.
Previous laboratory studies looked at unrealistically high concentrations of mercury in water, but Jason Unrine and colleagues at UGA’s Savannah River Ecology Laboratory studied environmentally realistic exposures in the diet. The study took place under controlled conditions to simulate contamination of the diet by atmospheric deposition of mercury.
Recent debate surrounding mercury contamination has focused on potential effects on the unborn fetus in pregnant women who consume contaminated fish, but much less attention has been focused on effects in wildlife.
“Diet is probably the most significant route of mercury exposure for larval amphibians,” says Unrine.
In this first study to demonstrate effects of environmentally realistic dietary mercury in amphibian larvae, the purpose was to determine if dietary mercury concentrations relevant to aquatic habitats contaminated by atmospheric deposition have the potential to cause adverse effects. The scientists thought they would see some sublethal effects, such as a decrease in growth rate and smaller size at the time of metamorphosis, not significantly increased rates of death. Their subject was the southern leopard frog.
The experiment’s results included increased rates of mortality, malformation, growth and development and premature metamorphosis as a result of increased dietary mercury exposure. These results suggest mercury concentrations in the diet of amphibians in habitats contaminated by atmospheric deposition may be sufficient to disrupt normal growth and development. This could decrease the number of normally developed individuals surviving to reproductive age and could lead to declines in populations.