Water-level fluctuations are a natural phenomenon in the Great Lakes due to climatic variability. Great Lakes wetlands depend on the resultant periodic changes between standing water and exposed environments to create diverse plant communities and habitats for a multitude of fish and wildlife species. Operation of the St. Lawrence Seaway resulted in regulation of Lake Ontario water levels, reducing both extreme high and low water levels and altering the timing of seasonal changes.

Shrubs and upland plants then became established in the wet soils above the water line, canopy-dominating larger plants such as cattails and purple loosestrife now crowd out other emergent plants in shallow water, and a few competitive submersed species dominate in slightly deeper water. Natural rejuvenation of wetland habitats has been lost, and access to wetlands by fish and wildlife is sometimes seasonally restricted. The International Joint Commission initiated a large study program in 2000 to develop and evaluate new regulation plans for Lake Ontario.

The goals of this study are to assist in development of a new, less environmentally damaging regulation plan for Lake Ontario by 1) collecting data on wetland plant community responses to past water-level fluctuations and 2) developing models to predict future vegetation response to proposed regulation plans.

Plant communities in 32 U. S. and Canadian wetland of four geomorphic types will be evaluated by sampling along topographic contours that represent different flooding/dewatering histories associated with past lake-level changes. Fish and wildlife habitat requirements will be researched by other U. S. and Canadian scientists. Seasonality of water-level patterns in proposed regulation plans will be evaluated based on fish-access data derived from bathymetric surveys and the area of wetland with suitable water depths for wildlife. All data will be incorporated into a GIS-based topographic/bathymetric model.

Proposed new regulation plans that would benefit wetlands will be based on plant, fish, and wildlife studies and evaluations of the amplitude and frequency of water-level changes derived from long-term lake-level studies. The potential response of wetland vegetation and associated habitat to all new proposed regulation plans will be evaluated based on data that show the past response of plant communities at specific elevations to changes in lake level, which will then be overlaid on topographic/bathymetric models that allow potential distributions of plant communities to be predicted.

Nancy Patterson, Canadian Wildlife Service
Joel Ingram, Canadian Wildlife Service

Email Dr. Douglas A. Wilcox, Branch Chief, Coastal and Wetland Ecology