Sediment Resuspension and Dissolved Oxygen Levels Associated with Ship Traffic: Implications for Habitat Remediation

Abstract Many of the Great Lakes Areas of Concern include harbours and navigable channels that experience disturbance of bed sediment due to the passage of large ships. Sediment resuspension due to ship passage may impact efforts to restore habitat and remediate contaminated bed sediment through in situ treatment. To examine the impacts of ship passage, water column profiles of temperature, pH, turbidity and dissolved oxygen, as well as suspended sediment samples, were taken at varying distances behind ships entering an industrial slip area of the Hamilton Harbour Area of Concern during the summer of 1995. Weekly water column profiles and suspended sediment samples also were collected at three sites in the slip area and a harbour control site to characterize ambient water quality. Ship passage significantly increased turbidity above ambient levels due to sediment resuspension, although the increase was less in the deeper areas of the slip. Levels of turbidity and suspended sediment concentration associated with ship passage exceeded that recommended for a moderate level of fish habitat protection. In association with the increased turbidity, levels of dissolved oxygen declined and often were less than 5 and 6.5 mg L-1, the Canadian Water Quality Guideline for later life stage warm and cold water fisheries, respectively. Based on the sample data and in situ flume experiments, the estimated depth of bed erosion due to a ship passage ranged from 1 to 8 mm. The impacts of sediment disturbance due to a ship passage should be considered when selecting and designing appropriate sites and technologies for remediation.