Type 4 Wetlands: Deep Marshes

wetland types
Written By Azalea Hallin-Graber

Known as “prairie potholes” in southern Minnesota, deep marshes are water-filled basins that provide food and resting areas for migratory birds and many other wildlife species.

Understanding Deep Marshes

Deep marshes act as a filter for excess nutrients. With standing water throughout the growing season, the marsh plants slow down water that can deposit nutrient-enriched sediment. Deep marshes can fill shallow lake basins, potholes, limestone sinks and depressions, and border open water. These wetlands provide water quality protection, floodwater detention, wildlife, and fisheries habitat, as well as recreational activities such as hunting, fishing, and canoeing. 

Characteristics Specific to Type 4 Wetlands

Soil Profile: The soil of deep marshes is typically covered in anywhere from 6 inches to 3 feet of water during spring and summer. If organic soil is present it can have a hydrogen sulfate odor. Typical mineral soils are bluish, greenish, or grayish. 

Vegetation: Vegetation in deep marshes contains herbaceous emergent, floating, and submerged aquatics. This includes grasses, sedges, rushes, water lilies, cattails, reeds, bulrushes, spike rushes, and wild rice. In more open areas pondweed, naiads, coontail, watermilfoils, waterweeds, duckweeds, and spatterdocks grow.

Fauna: Deep marshes provide food, resting areas, and nurseries for migratory birds and other wildlife. Muskrats and mink inhabit marshes alongside winter upland wildlife such as the ring-necked pheasant and eastern cottontail.

Functions & Benefits

Flood Mitigation & Erosion Control

Water Quality & Infiltration: A vital function of marshes is the improvement of water quality through trapping sediments and assimilating nutrients.

Habitat & Species Diversity: Deep and shallow marshes support a diverse range of wildlife species. Most common are water birds, who use marshes for breeding and feeding. These include swans, ducks, geese, rails, herons, egrets, terns, and songbirds. Bald eagles and northern harrier raptors search marshes for prey. Marshes provide spawning habitats for fish such as northern pike and muskellunge. Muskrats eat emergent vegetation, which creates open water areas. 

Economic & Recreational Value: Marshes act as a natural water quality improvement.

Mitigation Partners, Inc. Founders Dax Dickson & Tory Christensen

Azalea Hallin-Graber
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Type 3 Wetlands: Shallow Marshes
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Type 5 Wetlands: Inland Open Freshwater