A Laboratory Study of the Effects of Aluminum and pH on Amphibian Eggs and Tadpoles

Abstract

Bufo americanus and Rana sylvatica eggs and tadpoles were exposed in laboratory bioassays to a range of pH and aluminum concentrations commonly encountered in ponds and streams of central Ontario [Canada]. Bufo americanus and R. sylvatica hatching success was reduced at pH 4.14. The addition of 10 .mu.g inorganic monomeric aluminum (IMAI)/L at pH < 4.35 further reduced hatching success of B. americanus. Rana sylvatica was slightly less sensitive, with hatching success being reduced by addition of 20 .mu.g IMAI/L at pH 4.14. Increasing aluminum concentrations at pH 4.14 appeared to have no further effect except at the highest level used (200 .mu.g/L). IMAI that was toxic at pH 4.35 or 4.14 had no effect at pH 4.75 or 5.75. Toxicity was not dependent on the aluminum speciation, since similar levels of Al3+ and Al(OH) complexes that were toxic at pH 4.14 were not toxic at pH 4.75; also, Al(F)x complexes were as toxic as Al3+x. Egg mortality due to hydrogen ion stress was correlated with a delay in time of hatch and a reduction in egg size; however, there was no consistent pattern with respect to aluminum stress. Bufo americanus and R. sylvatica tadpoles were not sensitive to up to 200 .mu.g IMAI/L and pH as low 4.14.