THE BIOLOGICAL SIGNIFICANCE OF CONTAMINANTS IN SEDIMENT FROM HAMILTON HARBOR, LAKE-ONTARIO

Sediment from regions within Hamilton Harbour is highly contaminated with metals and polyaromatic hydrocarbons (PAHs); nevertheless, macroinvertebrates are present in situ and not all contaminated sites were toxic to laboratory organisms. Most sediment did elicit sublethal and/or lethal responses in bioassay species. Results of analyses of tissue residues in bioassay organisms, and the amelioration of toxicity by chemical treatments, implicate trace metals as contributing to sediment toxicity. Sediment oxygen demand, however, apparently contributed to the restricted benthic community in situ and some of the toxicity observed in vitro. In addition, for some stations there was evidence that PAHs were responsible for the detected deleterious effects. The study concluded that the suitability for colonization by benthic invertebrates of sediment in some areas of Hamilton Harbour is apparently limited both by contaminants and by high sediment oxygen demand. Remedial options aimed at eliminating oxygen depletion of the bottom waters of the harbor should result in improvements in the benthic invertebrate community directly, by providing a suitable oxygen regime for organisms less tolerant of temporal anoxia, and indirectly, by decreasing metal bioavailability, possibly through the coprecipitation of trace metals with iron hydroxides. The use of chemical treatments in sediment bioassays provides a technique for evaluating the source of sediment-associated toxicity.