Acidity and associated water chemistry of amphibian habitats in Nova Scotia

Abstract

One hundred and fifty-nine field sites consisting of ditches, bogs, marshes, ponds, and lakes in south and central Nova Scotia were surveyed for the presence of the adults, eggs, or larvae of 11 amphibian species. Water samples were analyzed for pH, alkalinity, color, conductivity, Na, K, Mg, Ca, SO₄, and Cl. Discriminant function analysis revealed that none of these variables predicted a species' presence. Two three-species groups were found to be significantly associated among themselves, but mutually exclusive of each other. The two groups were (i) Ambystoma maculatum, Hyla crucifer, and Rana sylvatica and (ii) Rana clamitans, Rana catesbeiana, and Rana palustris. Rana sylvatica and A. maculatum were observed breeding successfully in an acidic bog (mean pH 4.1). Rana clamitans adults and larvae were located in the field at pHs as low as 3.5 and 3.9, respectively. Field transplant studies, using eggs of A. maculatum and R. sylvatica (at pH 5.7 and 4.1) and Bufo americanus (at pH 6.3 and 4.1), revealed that R. sylvatica was least sensitive to acidity. There is considerable variation in acid tolerance among the various species of Nova Scotia amphibians. Nevertheless, successful breeding by some species is occurring at very low pHs.