Bioavailability and toxicity of polychlorinated biphenyls to sea urchins

Although the concentration of polychlorinated biphenyls (PCBs) in the environment may be on the decline, PCBs are still suspected of having an impact on the health of the ecosystem. However, the relative contribution of PCBs to health effects in invertebrates is unknown. The sea urchin was used as a model invertebrate to study the bioavailability and toxicity of individual PCB congeners. Three main issues were addressed: (1) whether the current structure-activity relationships defined for vertebrates can be applied to invertebrates, (2) whether maternal transfer of PCBs at environmentally-relevant concentrations would have an impact on sea urchin offspring, and (3) whether the disturbance and aeration of anoxic sediments would affect the bioavailability of a PCB to a sediment-ingesting organism.; This research demonstrated that three PCB congeners (IUPAC 47, 77, and 153) caused differential toxicity to developing sea urchin embryos at comparable body burdens which did not fit the predicted structure-activity relationships (SARs) developed for vertebrate systems. Congener 47, a diortho-substituted tetrachlorobiphenyl (TeCB), was found to be at least four times as toxic as congener 77, a nonortho-substituted (coplanar) TeCB whereas the SARs predicted that congener 77 would be 500 times more toxic than congener 47. PCB congener 153 was the least potent toxicant of the three congeners. An endpoint of reduced rate of mitosis was established in sea urchin embryos for congeners 77 and 153.; At environmentally-relevant concentrations, however, adult sea urchins (Lytechinus pictus) and their offspring were found to be resilient to PCB congener 47. Sea urchins were also shown to be more resilient to the effects of PCBs than what is predicted by the critical body residue.; The disturbance and aeration of an anoxic estuarine sediment spiked with PCB congener 47 resulted in a temporary increase in the bioavailability of this PCB to the sediment-ingesting sea urchin, Lytechinus pictus. The bioavailability appeared to be related to a decrease in the sediment organic carbon partition coefficient (Koc). Since the pore water concentration of the PCB increased upon aeration and disturbance of the sediment, this suggests that there would be an increase in the mobility of the contaminant as well.