Using 3D Hydrodynamic Modeling to Inform Ecosystem Management in a Large, Heavily Industrialized Harbour

Deep-water hypoxia during summer is one of the major environmental problems for the Remedial Action Plan for the Hamilton Harbour Area of Concern in Ontario, with challenging consequences for current and long-term ecosystem... [ view full abstract ]

Deep-water hypoxia during summer is one of the major environmental problems for the Remedial Action Plan for the Hamilton Harbour Area of Concern in Ontario, with challenging consequences for current and long-term ecosystem restoration and management objectives. Internal seiches due to surface wind forcing result in upwelling of cold, low dissolved oxygen (DO) hypolimnetic waters, modifying the amount and location of viable habitat for fishes on timescales of days. These upwelling events lead to swash zones that ring the harbour, within which water quality characteristics such as temperature and dissolved oxygen can vary rapidly and for relatively prolonged periods (order of hours to days). Fish telemetry data from 2016 reveals a strong response from walleye, adjusting their vertical position in response to thermocline oscillations to remain within their preferred thermal habitat. We will develop a 3D hydrodynamic model of Hamilton Harbour, validated with field data, able to provide insight into the development, frequency, spatial, and temporal extent of upwelling events. Reliable predictions of habitat usage and ecosystem trends, especially in a changing climate, require an understand how fish utilize their aquatic habitat. Model results, in combination with fish location data, will provide information on habitat usage in the swash zone and help inform ongoing habitat restoration projects in Hamilton Harbour. Hydrodynamic modeling can be an important tool to advise ecosystem management and coastal planning in systems with significant hypoxic zones that develop similar swash zones, such as Green Bay, Michigan, Lak Erie, and the Gulf of Mexico.