An investigation of sediment environmental quality at three small craft harbours in Ontario

Sediment concentrations of metals and PAHs exceeding the Ontario Provincial Sediment Quality Guidelines and the Canadian Sediment Quality Guidelines at Bronte Outer (Oakville, Ont.), Port Credit and Lakefront Promenade (Mississauga, Ont.) small craft harbours were found to be toxic to varying degrees in laboratory toxicity tests with benthic macroinvertebrates. This toxicity plus reduced abundance of benthos at Lakefront Promenade harbour and evidence of altered benthos community structures at all three harbours were related to sediment concentrations of certain contaminants, especially arsenic, mercury and chromium. Despite these trends, the estimated contaminant bioavailability was not sufficient to suggest that contaminants were causing these adverse effects. Estimated exposure concentrations of PAHs for benthivorous fish were estimated to exceed concentrations associated with some adverse effects in other studies, although the actual risk to these receptors at the harbours is uncertain.;This study suggests that further assessment of the ecological impacts associated with the sediment quality in these three harbours and management actions such as contaminant source control should be considered.