A Multilevel Study of Effects of Low pH on Amphibians of Temporary Ponds

• Published in: Journal of herpetology 1992-12, Vol.26 (4), p.413-422
• Main Authors: Sadinski, Walter J., Dunson, William A.
• Format: Article
• Language: English
• Subjects: Amphibians; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Embryos; Fresh water environment; Freshwater; Frogs; Fundamental and applied biological sciences. Psychology; Hatching; Larvae; Larval development; Metamorphosis; Ponds; Rain; Salamanders; Symposium: Amphibian Declines and Habitat Acidification
• ISSN: 0022-1511; 1937-2418
• DOI: 10.2307/1565117

Most researchers who have studied effects of low pH on amphibians that breed in temporary ponds measured direct lethal effects on single species. We summarize here results of a study conducted over 4 years in central Pennsylvania that illustrate the potential ecological importance of direct and indirect effects of low pH at lethal and sublethal levels. We argue for use of a multilevel approach (field sampling and experimentation in the laboratory, simulated ponds, and natural ponds) to study such effects on embryonic and larval amphibians of temporary ponds. A greater proportion of our study ponds was lower in pH than any reported previously in North America. Ponds were soft and often had high [Altotal]. Median seasonal pHs of 9 ponds were negatively associated with total amounts of rainfall over 4 years, but were not associated with H+ deposition during that same period. The pHs of many ponds declined as total rainfall increased. Embryonic mortality of the salamander Ambystoma jeffersonianum was high in ponds below pH 4.5. Less pH-associated embryonic mortality was observed among the more tolerant salamander, Ambystoma maculatum, and frog, Rana sylvatica. Laboratory-determined LC50 values for hatching of R. sylvatica, A. maculatum, and A. jeffersonianum were 4.10, 4.31, and 4.51, respectively, and predicted embryonic mortalities in ponds with good accuracy. More larval R. sylvatica survived at pH 4.1 in the laboratory when initially contained with A. jeffersonianum than at pH >6. This was due to reduced survival of, and subsequent reduced predation by, A. jeffersonianum at pH 4.1. In the same experiment, survival of A. maculatum was not different between pHs as they were eaten by A. jeffersonianum at pH >6 and suffered pH-induced mortality at pH 4.1. More larval A. jeffersonianum survived at pH 4.1 over 7 days when larval R. sylvatica and A. maculatum were available as prey, than when no prey were available. Larval A. jeffersonianum did not survive to metamorphosis in pH 4.2, and survived in low numbers in pH >6, in simulated ponds. Ambystoma maculatum metamorphosed less often, took longer to metamorphose, and weighed less at metamorphosis in simulated ponds of pH 4.2 versus those of pH >6. Reproduction of the newt Notophthalmus viridescens in simulated ponds was significantly lower, and adults were trapped more often exiting ponds, in pH 4.2 than in pH >6. Presence of adult N. viridescens in simulated ponds resulted in significantly lower survival of R.