Great Lakes coastal wetlands may often be characterized as highly dynamic systems. Seasonal and annual physical disturbances to these wetlands, often driven by water level fluctuations, contribute to the invasion and subsequent growth of opportunistic macrophytes or macrophytes adapted to a highly disturbed environment. In the Old Woman Creek National Estuarine Research Reserve, a drowned river mouth wetland in the western basin of Lake Erie, significant changes in plant community composition have occurred since the 1980s. Ceratophyllum demersum has become the dominant submersed macrophyte, displacing native species of Potamogeton. Myriophyllum spicatum has recently invaded but has failed to rapidly expand throughout the system, as is typical of inland aquatic systems. The once diverse shallow marsh and wet meadow flora, has been displaced by dense monotypic stands of Phragmites australis. The emergent macrophyte Nelumbo lutea has expanded its coverage of the open water from less than 5 percent in the 1970s and early 1980s to approximately 40 percent of the open water in the 1990s. Whereas the highly disturbed nearshore environment appears to have facilitated the growth of Phragmites and Nelumbo, it may be responsible for the inability of Myriophyllum to successfully establish in the wetland.

Key words: coastal wetlands, Great Lakes, macrophytes, Myriophyllum spicatum, Nelumbo lutea, Phragmites australis