Effects of Low pH and Other Chemical Variables on the Local Distribution of Amphibians

Freda, J.; Dunson, W.

The effect of low environmental pH on amphibians was studied in central Pennsylvania and the New Jersey Pine Barrens. Jefferson salamander (Ambystoma jeffersonianum) and Fowler 's toad (Bufo woodhousei) embryos were intolerant of low pH and were absent from the most acidic ponds. Wood frog (Rana sylvatia) and pine barrens treefrog (Hyla andersoni) embryos were tolerant and found in ponds with the lowest pHs. Laboratory tests demonstrated that A. jeffersonianum could not hatch below pH 4.50, whereas R. sylvatica could hatch even at pH 4.25. Similarly, B. woodhousei could not hatch below pH 4.10, but H. andersoni could hatch at pH 3.70. Embryos of all four species were transplanted into several ponds ranging in pH from 3.90-7.06 to test whether embryonic mortality caused by low pH could be responsible for the absence of the two least tolerant species from acidic ponds. Hatching of embryos of R. sylvatica was not related to pH while mortality of embryos of A. jeffersonianum increased significantly as pond pH declined. H. andersoni also hatched in all experimental New Jersey ponds, but embryos of B. woodhousei suffered significantly higher mortality in ponds of lower pHs. Hatching success was variable at specific pond pHs, indicating significant interaction of pH with other chemical variables. In laboratory trials tadpoles of B. woodhousei and H. andersoni grew significantly slower when exposed to low pH. This sublethal effect on body size has important implications for dynamics of amphibians populations in acidic ponds

Effects of Low pH and Other Chemical Variables on the Local Distribution of Amphibians

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