Radiocadmium exchange with seawater by Fundulus heteroclitus (L.) (Pisces: Cyprinodontidae)

Mummichogs, Fundulus heteroclitus (L.) accumulated Cd 115m (NO₃)₂ from synthetic seawater solutions during a period of 25 days, but the rate of whole body accumulation decreased with increasing concentrations of stable Cd²⁺ in the medium. Viscera were the major repository of Cd 115m during uptake, especially gastrointestinal tract and to a lesser extent liver. Loss in whole body radioactivity over a post-treatment interval of 180 days in cadmium-free seawater was about 90%, with gallbladder and especially liver most influential in the excretion processes; this pattern was unchanged by the level of stable Cd²⁺ present in the medium during uptake. The significance of this and other observations in terms of field monitoring of cadmium utilizing teleosts as indicators is discussed.