These communities are narrow and are usually dominated by annual herbs. Fen communities in the coastal Great Lakes wetlands are relatively uncommon. Fens are characterized by surface layers of poorly to moderately decomposed peat, often with well-decomposed peat near the base. They are often diverse communities dominated by sedges. Generalized diagram of Great Lakes Coastal marsh communities, showing the influence of fluctuating water levels.
Many coastal wetlands contain swamp communities along the landward margin.
Swamps are wetlands dominated by trees or shrubs that occur in a variety of flooding regimes, with standing water present during most or just a small part of the year. Most woody vegetation cannot tolerate the extensive flooding regimes of the Great Lakes. Therefore swamps in coastal areas are generally found along the upland margin of coastal wetlands or in basins isolated from the lakes. Many of these swamp communities are influenced by the Great Lakes only during periods of high water levels. Peatlands or bog communities are sometimes present in coastal wetlands, and may be found along Lake Superior and in northern portions of Lakes Michigan and Huron and small pockets within wetlands such as Point Pelee on Lake Erie.