Freshwater marshes differ from meadows in that most of the year the water table is above ground; in other words there is usually standing water. Shallow marshes are susceptible to drying out in late summer, and both are often dried out during severe drought. Drought is an important part of the life cycle of these plants, especially emergents like the bulrushes whose seeds will not successfully germinate underwater.
Shallow Marshes have water depth less than six inches. Shallow marshes have many of the species found in sedge meadows, and also the deep marsh.
Time lapse video of a deepwater marsh. Willows, Stiff Arrowhead and a number of other aquatic plants blow in the breeze.
Lake Littoral Zone
Shallow Open Water Wetlands occur in areas from 3 to 6 feet in depth, and the littoral zone of a lake is defined as the area of the lake in which enough light can penetrate to the bottom to support plants. This depth can be less than a few feet in highly turbid waters, to dozens of feet in very clear water. This zone is where much of the productivity of lakes occurs. The types of plants that occur here are often the same that appear in deep, or even shallow marsh. These habitats can be very similar; both rarely dry out completely, but some of the lake or marsh bed may become exposed during droughts, which counterintuitively has a rejuvenating effect on many aquatic and wetland plants.