Histological and toxicological responses of the mummichog, Fundulus Heteroclitus (L.) to combinations of levels of cadmium and dissolved oxygen in a freshwater

Impact of dissolved oxygen concentration (D.O.) on toxicity of cadmium to mummichogs in a freshwater medium and histological changes associated with exposure were determined. Levels of mortality were related to duration of exposure, cadmium concentration, and levels of dissolved oxygen. Median tolerance concentrations, at 96h, ranged upward from 1.3 to about 3.0 mg Cd 1^?1 at 2.3 and 8.5 mg DO 1^?1, respectively. Statistical analyses of mortality data showed factors examined were interdependent and that Cd × DO and Cd × time interactions were significant (P < 0.01). No histopathology was evident at 3 mg Cd 1^?1, although histopathology was evident in gills from fish exposed to 28 mg Cd 1^?1 for 6 1/2 h.

Responses of mummichogs to cadmium in freshwater are compared with results of a previous study involving exposure of the species to cadmium in seawater and with responses of freshwater fishes subjected to various heavy metals. Differences and similarities in patterns of response are discussed in terms of water balance.