Impact of cadmium on the mummichog Fundulus heteroclitus and the role of calcium in suppressing heavy metal toxicity.

1. Freshwater adapted mummichogs (Fundulus heteroclitus) were exposed to cadmium. In soft water (less than or equal to 5 mg/l CaCO3), the 4-day safe (TL100) and sublethal (TL50) tolerance limits (TLs) for cadmium were 0.14 microgram/l and 12.2 micrograms/l, respectively. 2. Survival declined with increasing cadmium concentration and the length of exposure. The toxicity of cadmium was reduced in water with high calcium concentration (200 mg/l CaCO3). Pre-exposure to calcium also prolonged the survival in cadmium-containing water. 3. The mummichog appears to be extremely well suited for monitoring environmental cadmium poisoning.