Underwater plants are a valuable part of the Great Lakes ecosystem, providing food and shelter for aquatic animals. Aquatic plants also help stabilize sediments, thereby reducing shoreline erosion. Annual fall die-offs of underwater plants provide food and shelter for overwintering small aquatic animals such as insects, snails, and freshwater shrimp.
In some areas, underwater plants may be the dominant primary producer in the food chain supporting animal populations. Fish, for example, are usually more abundant where underwater plants are found. Plants and associated animals are a source of food for fish and waterfowl in the Great Lakes (Table 1). Despite the importance of underwater plants in the Great Lakes, very little is known about them, partly because of the difficulty of observing the plants in their natural habitat.
The purpose of this field guide is to aid in the identification of common underwater plants in the Great Lakes. These plants are found mostly in shallow, nearshore waters along sheltered bays, peninsulas, and the four connecting rivers of the Great Lakes, including the St. Lawrence River (Figure 1). Connecting rivers are especially favorable for aquatic plants because they are shallow, have a consistent flow of water, and are protected from heavy wave action typical of other Great Lakes shorelines.