Cation Concentrations and Acidity in Breeding Ponds 



of the Spotted Salamander, Ambystoma maculatum 



(Shaw) (Amphibia: Ambystomatidae), in Virginia 



Charles R. Blem and Leann B. Blem 



Department of Biology, Virginia Commonwealth University, 



Richmond, Virginia 23284-2012 



ABSTRACT. — For 8 years beginning in 1983, we monitored breeding 

 activity by spotted salamanders, Ambystoma maculatum, in temporary 

 ponds in eastern Virginia. In the spring of 1988, 1989, and 1990, a 

 majority of the ponds examined (67.4%; N = 218) never contained egg 

 masses or spermatophores. During the 8 years the number of egg 

 masses declined severely in many ponds that were used as breeding 

 sites. Ponds with breeding salamanders had significantly higher pH 

 values than those that lacked breeding activity for all years, but were 

 similar in pH to those with failed reproduction. Analysis of the 20 

 major cations indicated that successful ponds with large numbers of 

 spotted salamander egg masses had lower aluminum, copper, and lead 

 levels than ponds with declining populations of salamanders. Silicon 

 levels were significantly higher in successful ponds. Stepwise dis- 

 criminant function analyses indicate that high aluminum, copper, 

 silicon, and zinc concentrations in breeding ponds are associated 

 significantly with the decline in reproductive activity of spotted 

 salamanders. The combination of elements in ponds maintaining stable 

 or increasing populations of breeding spotted salamanders was 

 distinctive; 91.8% were classified correctly as successful or failed ponds 

 by canonical correlation analyses. Proximity of roads was not 

 correlated with the concentration of any cation. 



In general, it appears that low pH may produce mortality in 

 amphibian eggs, larvae, and perhaps adults both by acid toxicity and by 

 causing an increase in the concentration of free ions of toxic elements 

 such as aluminum in the water column (Freda and Dunson 1985a). 

 Acidity interferes with the ability of larvae to regulate internal concen- 

 trations of sodium, chloride, and perhaps other ions (Freda and Dunson 

 1985b). Additionally, low pH levels affect composition of the perivitelline 

 fluid and the color and texture of the egg mass (Robb and Toews 1987). 

 At extremely low pH (e.g. < 4.0) the egg capsule (perivitelline space) 

 may shrink dramatically, killing the embryos (Pough 1976, Freda and 

 Dunson 1985a, Blem and Blem 1989). In the spotted salamander, 

 Ambystoma maculatum (Shaw), 50% or more of embryos die at pH 5.0 

 to 6.0 (Tome and Pough 1982) and all die at pH 4.0 or less (Pough and 

 Wilson 1977, Cook 1983). However, in some ponds with relatively low 



Brimleyana 17:67-76, December 1991 67 



