Abstract |
Previous studies have shown toxic effects of polychlorinated biphenyls (PCBs) on aquatic life only in the micro g/L range, well above normal ambient concentrations. Daphnia pulicaria was isolated from Lake Erie and exposed to 50 ng/L to 10 micro g/L of 2,2'-dichlorobiphenyl (DCB) in lifetable and physiological studies. Reproduction, mortality, growth, and respiration were measured for periods up to the entire lifespan of the animal with and without the use of an organic surfactant. Significant mortality and inhibition of reproduction were found at levels as low as 50-100 ng/L in lifetable studies, and no safe level could be determined. A unique, yet repeatable, dose-response curve occurred in lifetables with maximum inhibition at low to intermediate concentrations. Inhibition at the highest level tested, 10 micro g/L, occurred only after continuous exposure for three generations. Increasing concentrations of CBD stimulated growth, while respiration experiments yielded variable results. (Copyright (c) 1988 Springer-Verlag New York, Inc.) |