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Historically, Lake St. Clair was surrounded by marshes, which extended several miles inland along the St Clair and Clinton Rivers. Most of the marshes have been drained for agriculture and shoreline development but sizable areas still remain, particularly within the St. Clair delta. Marshes can also occur further inland, but the bulk of the marshes within the project area are Great Lakes marsh and are linked hydrologically to the Great Lakes.
Fluctuations in water levels are characteristic of Great Lakes marshes and have a huge influence on them; coastal systems are adapted to periodic inundation and require it to maintain high levels of biodiversity. During periods of high water, emergent vegetation is flooded out and floating leaved and submergent plants expand their range as they are more tolerant of flooding. Further inland, as flooding increases, emergents replace wet meadow and wet meadow expands into shrub/carr as the shrubs are inundated and die. As water levels drop, communities move lakeward and fertile mud flats are exposed and recolonized by emergents from the seedbank.
The St. Clair River delta is one of the most critical areas for waterfowl breeding and staging during the migration in the entire Great Lakes Region. Waterfowl that breed in the St. Clair Delta include mallard, black duck, blue-winged teal and redhead. Far more species of waterfowl use the delta during the migration, as it is located on both the Atlantic Flyway and the Mississippi Flyway, with over 800,000 ducks passing through the area annually. Diving ducks such as canvasback, redhead and scaup feed on the wild celery, waterweed and pondweed of the submergent marsh, before heading southeastward to the Chesapeake Bay, although up to 15,000 overwinter on Belle Isle and the Detroit River. Dabbling ducks such as green-winged teal, northern shoveler and northern pintail feed on the eelgrass, widgeon grass and seeds of sedges, bulrushes, wild rice, pondweeds and smartweeds. The area is a major staging ground for tundra swan and migratory Canada geese, as well.
Lake St. Clair marshes provide valuable habitat for over 65 species of fish, either permanently, or on a temporary basis for spawning, nursery areas, shelter or feeding. Thirty-nine species of amphibians and reptiles use Lake St. Clair's marshes including salamanders, frogs, toads, turtles and snakes. Common mammals include muskrat, mink, raccoon, opossum and red fox.
Rare birds that nest or forage in the marshes around Lake St. Clair include king rail, least bittern, black-crowned night heron, common tern, Forster's tern, bald eagle, northern harrier, marsh wren and Louisiana waterthrush. Rare reptiles include Blanding's turtle and eastern fox snake and rare fish include northern madtom, pugnose shiner and pugnose minnow. Rare plants associated with the marshes include swamp rose mallow and wild rice.
For more information, see: Coastal Habitat Assessment, Section IV (PDF)