Forcasting the response of coastal wetlands to declining water levels and environmental disturbances in the Great Lakes

Wei, A.
Ph.D. Thesis for the Department of Biology, McMaster University


The overall purpose of this study was to examine the impact of increasing human-induced and natural stresses on the distribution of aquatic vegetation and fish along the Great Lakes shoreline. The first part of the dissertation proposes a predictive model to examine the effect of long-term water level fluctuations on the emergent plants in Lake Ontario coastal wetlands while taking into account other factors such as urbanization and invasive species. Starting with Cootes Paradise Marsh, a highly urbanized freshwater marsh at the west end of Lake Ontario, a new approach based on a digital elevation model is proposed and compared with the traditional water-level model. The results indicate that the new approach is better than the traditional water level model. To verify the effectiveness of the new approach, ten coastal wetlands from eastern Lake Ontario are tested. The results confirm that the new approach provides an effective way to determine the effect of the hydrological disturbance on emergent plants even when the target wetlands have the same water level. The second part of the dissertation addresses response of fish and explores the use of high resolution satellite imagery to quantify the supply of fish habitat and wave disturbance in coastal wetlands. The results show that (1) the Great Lakes fish community utilizes wetlands disproportio nately to their availability and the distribution of wetland-associated taxa is influenced by wetland type; (2) the high resolution IKONOS imagery can be used effectively to monitor the change in aquatic vegetation and thus track alterations in fish habitat in Great Lakes coastal marshes; and (3) aquatic vegetation in coastal wetlands is affected by exposure disturbance that can be attributed to the lake and any disturbance originating from inside the wetland and therefore, the effect of exposure and geomorphology should be partitioned out when examining the effects of anthropogenic disturbance on submersed aquatic vegetation.

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