Amphibians in metal-contaminated habitats

Mining for heavy metals usually has a strong impact on the environment, including the formation of spoil heaps, mine tailings and mine drainage, all of which are heavily contaminated. Heavy metals are generally regarded as toxic for most organisms, including amphibians, although the effects of heavy metals may be extremely complex and sometimes even positive. This study presents a survey of observations of amphibians in habitats severely contaminated by mining for heavy metals in Central and Eastern Europe. Rocky spoil heaps and sandy mine tailings were generally found to be devoid of amphibians. In moist habitats, especially streams, puddles and ponds fed by drainage water, however, six species of amphibians were observed, i.e., Bombina variegata, Rana ridibunda, R. temporaria, Bufo viridis, Salamandra salamandra and S. atra. All six species were found in habitats superficially similar to their typically preferred habitats, e. g., Bombina variegata in small puddles, Salamandra salamandra larvae in a swiftly running stream. Moderately increased concentrations of copper, arsenic, antimony and other elements and an acidic pH of soil and water did not keep amphibians away. Highly contaminated or extremely acidic water bodies are usually devoid of amphibians even though they may be present in the surroundings, suggesting that amphibians may be capable of recognising and avoiding extreme degrees of contamination. With the uptake of the pollutants being highly probable, some amphibians appear to possess a limited tolerance against heavy metals.