Types of Wetlands: Bog, Marsh Morass, Swamp & Fen

Wetlands are valuable assets in a healthy ecosystem. They provide a habitat for fish and animals. They prevent excessive flooding by acting as a temporary reservoir and then releasing that water when the surrounding area drains. Wetlands hold sediment which helps to purify the surface water. According to the EPA, wetlands make up 5 percent of the land surface in the contiguous United States, yet they provide habitat for 31 percent of the different plant species. There are several types of wetlands.

A bog is a wetland created over time. An advancing glacier carved a depression in the soil. The melting glacier filled the depression with water and created a lake. The vegetation growing at the edge of the lake grew and died, leaving a sediment. The streams that fed the lake brought more sediment. The lake became filled with sediment and turned into a swamp with plants growing throughout. The plants died and decayed in the water. Eventually, the oxygen levels became low from the oxidation of the decaying plant material. The combination of low oxygen and no new nutrients encouraged the growth of sphagnum moss that crowded out all other plants and created an area open to full sun. The sphagnum moss maintained the conditions of full sun, high water, low oxygenation in the water, acidic soil, and low levels of nutrients. These characteristics define a bog.

Marshes, sometimes called morasses, are more varied than bogs. Marshes contain grasses, flowers, and shrubs. There are birds that make a permanent home in a march and more birds that use them as a resting and feeding spot during their annual migrations. Marshes are flooded with several feet of water each year.

A swamp is really a slow moving river or stream or a lowland area that is regularly flooded by a nearby river. Swamps contain trees, shrubs, and other vegetation. The Florida everglades are an example of a freshwater swamp. Swamps reduce the risk of downstream flooding, as well as provide animal habitat.

A fen is low land covered by water that is somewhat poor in nutrients and contains sedges, grasses, reeds, and sphagnum moss. Fens are fed by upstream water sources and have more nutrients than bogs. Fens are peatlands, land on which peat has accumulated.

Mire, quagmire, muck are names for wetlands that have wet soil or mud near the surface. Footsteps will leave an impression in the mud for a time. These terms are more description of conditions that a wetland type.

Sources
Camosun Bog, http://www.naturalhistory.bc.ca/CamosunBog/frames_about.htm
Missouri Botanical Garden, http://www.mbgnet.net/fresh/wetlands/index.htm
Wetlands, US EPA, http://www.epa.gov/owow/wetlands/
Wetlands Fact Sheet, http://www.epa.gov/owow/wetlands/pdf/fun_val.pdf
Maine Natural Areas Program, http://www.maine.gov/doc/nrimc/mnap/features/eco_unpattfen.htm