Genotoxic substances in the St. Lawrence system II: Extracts of fish and macroinvertebrates from the St. Lawrence and Saguenay rivers, Canada

Abstract

AbstractAquatic biota frequently accumulate organic contaminants and maintain steady state tissue concentrations that are as much as 105 times higher than those in the surrounding water. Although many researchers have studied the accumulation of genotoxic polycyclic aromatic hydrocarbons (PAHs) by aquatic biota, few researchers have used bioassays to investigate the accumulation of genotoxins. In several previous studies we used the SOS Chromotest to investigate the genotoxicity of industrial effluent extracts, sediment extracts, and bivalve tissue extracts. In this study we use the SOS Chromotest to investigate the accumulation of organic genotoxins by macroinvertebrates and fish in the St. Lawrence and Saguenay rivers (Quebec, Canada). Tissue concentrations of genotoxins (expressed as μg benzo[a]pyrene genotoxic equivalents) reveal bioconcentration factors in the 102 to 103 range. Concentrations are partially determined by lipid content (r2 = 0.22). Lipid‐normalized values indicate that genotoxin concentrations in invertebrate tissues are significantly higher than those in fish. Fish values indicate that tissue concentrations are biodiminished, with fish at higher trophic levels having lower tissue burdens of genotoxins. The biodiminution pattern observed corresponds exceptionally well with trophic position assignments made by other authors. More contaminated sites yielded less contaminated specimens. This may be due to the induction of phase I and phase II detoxification enzymes that is likely to occur at high levels of exposure. Although the results do not support PAHs as the putative genotoxins, the results do indicate that the accumulated genotoxins have similar properties. Tissue to sediment ratios of genotoxins are similar to those observed for genotoxic PAHs, and far lower than those of more persistent organochlorines. Although we did not investigate genotoxic effects, we might expect the most dramatic effects in fish that consume contaminated macroinvertebrates.