Effects of pH and aluminium on embryonic and early larval stages of Swedish brown frogs Rana arvalis, R. temporaria and R. dalmatina

Abstract

The effects of pH and aluminium on embryonic and early larval stages of Swedish brown frogs Rana arvalis, R. temporaria and R. dalmatina were tested in laboratory bioassays. In all three species egg mortality and time needed for embryonic development to hatching increased when pH declined, but no significant effects were found on embryonic development when aluminium level was elevated. In R. arvalis and R. temporaria larval mortality was affected by both pH and aluminium. In both species the frequency of occurrence of larval deformities increased in acid water, and there was a synergistic effect of pH and aluminium. In R. arvalis swimming behaviour was disturbed by high levels of aluminium at pH 5. In all three species the frequency of stressed larvae increased when pH was depressed and aluminium concentration elevated, and there was a synergistic effect when both were combined. The three species differed significantly in egg mortality, time needed for embryonic development, larval mortality, larval deformities and larval stress al low pH and high aluminium levels. R. arvalis showed the highest acid tolerance and R. dalmatina was the most sensitive to low pH.