Relationship between PCB accumulation and reproductive output in conditioned oysters Crassostrea virginica fed a contaminated algal diet

Abstract

Because of their resistance to environmental degradation, polychlorinated biphenyls (PCBs) are among the most widespread environmental contaminants. PCBs have high bioaccumulation potential and may affect a number of biological/physiological processes including disruption of the endocrine system function, lipid metabolism and reproduction. The objective of this study was to test whether conditioning sexually immature oysters with PCB-contaminated algal diets affects their subsequent reproductive success. Sexually immature oysters were conditioned in individual containers and fed daily with 0.7 g algal paste containing 0, 0.35 or 3.5 μg PCBs for up to 76 days. The impact of sediment load on PCB accumulation in oysters was also tested by exposure of a subset of oysters to clay particles. Oysters in different treatments were sampled 56 days after conditioning with PCB-contaminated algal diets to determine uptake and distribution of PCBs in gonad, digestive gland, mantle, gill and muscle, and the presence of gametes. Tissues from oysters exposed to PCBs alone for 56 days were also analyzed for lipid and fatty acid composition. Following 61 and 76 days of PCB exposure, remaining oysters from all treatments were induced to spawn via thermal stimulation. Non-spawned oysters were stripped to determine if sexual products were present. Oysters exposed to PCBs alone and PCBs plus clay particles showed similar trends in PCB accumulation, but concentrations were generally lower in the latter. PCB accumulation in oysters increased with an increase in algal-associated PCB concentrations, varied with organ types and was correlated with lipid content. The highest PCB concentration was in the gonad and the lowest in gill and muscle. PCB-153, -138/158, -118, -90/101 and -149 were the dominant congeners in all tissue compartments, except the muscle where PCB-28/31 was the dominant congener pair. PCB exposure appeared to impair both lipid metabolism and reproductive success. Although PCB exposure produced only slight changes in the lipid class composition in the oysters, decreases in phospholipids were observed in gonad, muscle and mantle of oysters exposed to 3.5 μg PCBs daily for 56 days. After 56 days of conditioning with PCB-sorbed algal paste, no well-developed mature eggs were observed in any of the oysters examined for the presence of sexual products. No significant difference was noted in reproductive success (production of spawned females and males) between sediment-treated and non-treated groups after 76 days of PCB exposure compared to controls, PCB-exposed oysters produced fewer spawned females, but no dose-dependent relationship was observed.