Effects of selected PCB congeners on survival, growth, and reproduction in Daphnia magna

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Abstract
The effects of individual polychlorinated biphenyl (PCB) congeners on survival, growth and reproduction in the freshwater cladoceran, Daphnia magna, were determined. Congeners evaluated in this study (IUPAC numbers 52, 77, 101, 118, 138, 153, 180) represent a variety of microsomal mixed‐function oxidase (MFO) inducers. After 21 d of static renewal exposure, Daphnia survival was high (88–100%) in all congener treatments and unaffected by any PCB. Polychlorinated biphenyl congeners had little to no detectable sublethal effects on reproduction and growth. The number of neonates produced was either unaffected (congeners 52, 77, 118) or enhanced (congeners 101, 138, 153, 180). Effects on total biomass were mixed and the magnitude of significant differences, when observed, was small. Diminished biomass was observed in Daphnia exposed to congener 101 whereas increases occurred in treatments with congeners 52 and 118. Both elevated and diminished biomass was observed in animals exposed to congener 77. Congeners 138, 153 and 180 had no significant effect on Daphnia biomass.Daphnia accumulated substantial amounts of all PCBs even though minimal effects on survival, growth and reproduction were observed. Mean tissue concentrations ranged from approximately 2.0 ng/mg to 130 ng/mg dry weight. These tissue residues are one to several orders of magnitude greater than those observed in aquatic fish and invertebrates collected in and around industrial waterways of the Great Lakes. Possible explanations for the lack of PCB congener toxicity are discussed.

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