Experimental Studies of the Effects of Acidity and Associated Water Chemistry on Amphibians

Abstract

Laboratory bioassays with 5 species of Nova Scotian amphibians (Ambystoma maculatum, Hyla crucifer, Rana sylvatica, R. palustris, and Bufo americana) and Xenopus laevis revealed pH 4.0 to 5.0 as the critical range within which developing embryos showed reduced hatching success, and below which hatching did not occur. Bioassays revealed differences in acid tolerance among various species of Nova Scotia amphibians. For some species, aluminum in combination with pH< 5, had a deleterious effect. Calcium ameliorated pH toxicity, but in some cases mortality was increased at very high Ca concentrations (?50 ppm). Larvae of Rana clamitans and adult Notophthalmus viridescens survived exposure to pH as low as 3.3, but this tolerance was reduced at low temperatures.