74 Charles R. Blem and Leann B. Blem 



(National Academy of Sciences 1974), although the degree of toxicity 

 has been determined for only a few species. Likewise, lead levels of 

 some ponds were in the range of concentrations known to be detrimental 

 (0.75-20 /xg/ liter; USEPA 1980a). On the other hand, zinc levels of only 

 79 ppm were obtained and levels of 180-540 jug/ liter are considered to 

 be detrimental to aquatic organisms (USEPA 1980b). The relationship 

 between silicon levels and successful use of breeding ponds is puzzling. 

 Silicon concentrations in successful ponds were significantly higher than 

 in those that failed (Table 1). We do not know of any relationship 

 between silicon and viability of aquatic life. 



Some elements have complex effects on success of hatching of 

 amphibian eggs, e.g. a few elements appear to be harmful at both high 

 and low concentrations. For example, at a pH of 4.25, hatching and 

 survival of embryos of the Jefferson salamander, Ambystoma jeffer- 

 sonianum (Green), are greatest at magnesium concentrations of about 

 20 mg/ liter, but the hatching rate declines at both lower and higher 

 concentrations (Freda and Dunson 1985a). The effects of most other 

 elements increase with decreased pH, but the degree of synergism with 

 other elements is unknown. It appears that failed ponds in Virginia have 

 distinctive cation compostions (Fig. 1). Stepwise discriminant function 

 analyses suggest that aluminum, copper, silicon, and zinc all may play a 

 role in mortality of spotted salamander larvae. Failed and successful 

 ponds did not differ in pH. Rather, it appears that at the present levels 

 of acidity, ponds become fatal because of their elemental composition. 



The few surveys of the chemistry of temporary ponds used for 

 breeding by amphibians have considered either restricted suites of 

 chemical elements or have included relatively few ponds (e.g. Dale et al. 

 1985, Freda and Dunson 1986, Albers and Prouty 1987). Conclusions 

 about the importance of specific chemicals in temporary ponds have 

 been mixed. For example, Freda and Dunson (1986) concluded that 

 mortality may be influenced by significant interactions of pond pH and 

 other chemical variables, whereas Albers and Prouty (1987) found that 

 pond longevity, water temperature, and oxygen content were more 

 significant in spotted salamander reproduction than chemical alterations 

 brought about by acid precipitation. Those findings are not incom- 

 patible, given the range of study areas, times, and substances considered. 



ACKNOWLEDGMENTS.- We are indebted to the Nongame 

 Wildlife and Endangered Species Program, Virginia Department of 

 Game and Inland Fisheries, for financial support of the research that 

 led to this publication. Karen Blem helped with some technical aspects 

 of the research, Charles Lunsford provided important information 

 about water parameters, and Kathy Beal made many helpful suggestions 

 about statistical methods. 



