Phytoplankton constitutes the base of the trophic webs in the marine environment, so it is important to know the possible effects of pollutants on the algal populations. In the present paper the effect of cadmium on the population growth of the diatom Chaetoceros gracilis was assessed. The microalgae were cultured in the a modified “f/2” Guillard medium, and were exposed to different concentrations of cadmium between 50 and 100000 µg.–1, which produced an inhibitory effect from 20% to 99% on the population growth of Chaetoceros gracilis. Based on the dose (cadmium)-response (inhibition) relationship, a mean effective concentration (EC50%) equal to 591 µg.L–1 of cadmium was obtained.

In the present paper, the mean effective concentrations (EC50%) of cadmium (Cd+2) and chromium (Cr+6) using postlarvae of the silverside fish Odontesthes (Austromenidia) regia regia were determined. The postlarvae were exposed to different concentrations of the metals, between 0,142 and 1,208 mg.L–1 of cadmium and between 0,53 and 33,74 mg.L–1 of chromium. The mean effective concentrations (EC50%) obtained were 0,648 mg.L–1 of cadmium (at 96 h) and 2,68 mg.L–1 of chromium (at 96 h). Comparatively, cadmium is more toxic than chromium, and silverside is more tolerant than other organisms.

Phytoplankton constitutes the base of the trophic webs in the marine environment, so it is important to know the possible effects of pollutants on the algal populations. In the present paper the effect of cadmium on the population growth of the diatom Chaetoceros gracilis was assessed. The microalgae were cultured in the a modified “f/2” Guillard medium, and were exposed to different concentrations of cadmium between 50 and 100000 µg.–1, which produced an inhibitory effect from 20% to 99% on the population growth of Chaetoceros gracilis. Based on the dose (cadmium)-response (inhibition) relationship, a mean effective concentration (EC50%) equal to 591 µg.L–1 of cadmium was obtained.

In the present paper, the mean effective concentrations (EC50%) of cadmium (Cd+2) and chromium (Cr+6) using postlarvae of the silverside fish Odontesthes (Austromenidia) regia regia were determined. The postlarvae were exposed to different concentrations of the metals, between 0,142 and 1,208 mg.L–1 of cadmium and between 0,53 and 33,74 mg.L–1 of chromium. The mean effective concentrations (EC50%) obtained were 0,648 mg.L–1 of cadmium (at 96 h) and 2,68 mg.L–1 of chromium (at 96 h). Comparatively, cadmium is more toxic than chromium, and silverside is more tolerant than other organisms.