http://amphibiaweb.org/declines/ChemCon.htmlHEAVY METALS AND ACIDIFICATION
The intense agricultural and industrial production from mines has increased the prevalence of heavy metals in surface waters. Heavy metals, such as, aluminum (Al), lead (Pb), zinc (Zn), cadmium (Cd), mercury (Hg), silver (Ag), copper (cu), arsenic (As), manganese (Mn), molybdenum (Mo) and antimony (SB) may adversely affect amphibian populations (Blaustein et al. 2003). For example, Rowe et al. (1996, 1998) found that coal ash increased the incidence of oral deformities, increased metabolic rate and lowered larval survival of the American bullfrog, Rana catesbeiana, larvae. In the Southern toad, Bufo terrestris, coal ash increased corticosterone and testosterone levels and lowered larval survival (Rowe et al. 2001).
Acidification can also have adverse effects on amphibian growth and development ultimately contributing to population declines. Extremely low pH can arrest embryo development (Freda et al. 1990). At low but slightly higher pH levels, embryo development proceeds but the enzymes that induce hatching are inhibited, thus, trapping the fully developed embryo inside the egg capsule (Clark and Lazerte 1987).
Acidification and heavy metal contamination often work synergistically because the solubility of heavy metals in water increases as pH drops. As a result, heavy metals leach more quickly from contaminated soils in contact with acidic water (Blaustein et al. 2003). Furthermore, studies have found that inorganic monomeric aluminum acts synergistically with pH to cause embryo mortality (Clark and Hall 1985, Clark and Lazerte 1985, Freda and McDonald 1990).