The influence of acidic pond water on amphibians: A review

Acidic pond water may influence the reproduction of amphibians by causing direct mortality of embryos and larvae, and/or by disrupting trophic relationships between amphibians and other aquatic organisms. The embryo is the most sensitive stage of development and may abort soon after exposure to very low pH or eventually fail to hatch at a more moderate pH. Larvae are killed by disruption of Na and Cl balance. The toxicity of pond water is governed by complex interactions of pH, temperature, and the concentrations of Al, Ca, and organic acids. The reduction in recruitment associated with acidification of ponds affects both the local distribution and abundance of amphibians. The relative importance of different mechanisms of acidification of amphibian breeding sites is unknown. Amphibian breeding ponds are generally small, low in buffering capacity, and darkly stained by humic substances, making it difficult to discriminate between the contribution of acid from atmospheric input and natural sources (such as sphagnum and organic acids). It is however quite clear that temporary ponds are extremely vulnerable to acidification by rain and that they require continued monitoring in order to detect future changes in biological and/or chemical characteristics.