Effects of cadmium exposure on feeding of freshwater planktonic crustaceans.

1. Effects of cadmium exposure (0.010-0.100 ppm) on food consumption and assimilation rates of crustacean zooplankton from 2 lakes were studied in laboratory using radioisotope (14C) technique. 2. The inhibiting effects were significant 48 hr after Cd-exposure, but not after 20 hr exposure. 3. Daphnia spp. were the most affected cladocerans; copepods, especially the cyclopoids, appeared less sensitive. 4. The decrease in assimilation rates was much more marked than in the consumption rates. 5. The 14C-technique offers quick and sensitive means of studying the effects of heavy metal toxicity.