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A marsh along the edge of a small river Wye Marsh panorama1.jpg
A marsh along the edge of a small river
Marsh in shallow water on a lakeshore USGS image cropped.jpg
Marsh in shallow water on a lakeshore
Green Cay Wetlands, Palm Beach County, Florida Green Cay Wetlands and Nature Center pic. bb8822.jpg
Green Cay Wetlands, Palm Beach County, Florida

A marsh is a wetland that is dominated by herbaceous rather than woody plant species. [1] Marshes can often be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial ecosystems. They are often dominated by grasses, rushes or reeds. [2] If woody plants are present they tend to be low-growing shrubs. This form of vegetation is what differentiates marshes from other types of wetland such as swamps, which are dominated by trees, and mires, which are wetlands that have accumulated deposits of acidic peat. [3]

Wetland A land area that is permanently or seasonally saturated with water

A wetland is a distinct ecosystem that is inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, and support of plants and animals. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, and the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for rapidly assessing these functions, wetland ecological health, and general wetland condition have been developed in many regions and have contributed to wetland conservation partly by raising public awareness of the functions and the ecosystem services some wetlands provide.

Mire wetland terrain without forest cover, dominated by living, peat-forming plants

A mire is a wetland type, dominated by living, peat-forming plants. Mires arise because of incomplete decomposition of organic matter, due to waterlogging and subsequent anoxia. Like coral reefs, mires are unusual landforms in that they derive mostly from biological rather than physical processes, and can take on characteristic shapes and surface patterning.

Peat accumulation of partially decayed vegetation

Peat, also known as turf, is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem is the most efficient carbon sink on the planet, because peatland plants capture CO2 naturally released from the peat, maintaining an equilibrium. In natural peatlands, the "annual rate of biomass production is greater than the rate of decomposition", but it takes "thousands of years for peatlands to develop the deposits of 1.5 to 2.3 m [4.9 to 7.5 ft], which is the average depth of the boreal [northern] peatlands". Sphagnum moss, also called peat moss, is one of the most common components in peat, although many other plants can contribute. The biological features of Sphagnum mosses act to create a habitat aiding peat formation, a phenomenon termed 'habitat manipulation'. Soils consisting primarily of peat are known as histosols. Peat forms in wetland conditions, where flooding or stagnant water obstructs the flow of oxygen from the atmosphere, slowing the rate of decomposition.


Basic information

White water lilies are a typical marsh plant in European areas of deeper water. Water Lily - - 483063.jpg
White water lilies are a typical marsh plant in European areas of deeper water.
Many kinds of birds nest in marshes; this one is a yellow-headed blackbird. Xanthocephalus xanthocephalus -100 Mile House, British Columbia, Canada -male-8.jpg
Many kinds of birds nest in marshes; this one is a yellow-headed blackbird.

Marshes provide a habitat for many species of plants, animals, and insects that have adapted to living in flooded conditions. [1] The plants must be able to survive in wet mud with low oxygen levels. Many of these plants therefore have aerenchyma, channels within the stem that allow air to move from the leaves into the rooting zone. [1] Marsh plants also tend to have rhizomes for underground storage and reproduction. Familiar examples include cattails, sedges, papyrus and sawgrass. Aquatic animals, from fish to salamanders, are generally able to live with a low amount of oxygen in the water. Some can obtain oxygen from the air instead, while others can live indefinitely in conditions of low oxygen. [3] Marshes provide habitats for many kinds of invertebrates, fish, amphibians, waterfowl and aquatic mammals. [4] Marshes have extremely high levels of biological production, some of the highest in the world, and therefore are important in supporting fisheries. [1] Marshes also improve water quality by acting as a sink to filter pollutants and sediment from the water that flows through them. Marshes (and other wetlands) are able to absorb water during periods of heavy rainfall and slowly release it into waterways and therefore reduce the magnitude of flooding. [5] The pH in marshes tends to be neutral to alkaline, as opposed to bogs, where peat accumulates under more acid conditions.

Aerenchyma spongy tissue that forms spaces or air channels in plants

Aerenchyma is a spongy tissue that forms spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. The channels of air-filled cavities provide a low-resistance internal pathway for the exchange of gases such as oxygen and ethylene between the plant above the water and the submerged tissues. Aerenchyma is also widespread in aquatic and wetland plants which must grow in hypoxic soils.

<i>Typha</i> genus of plants

Typha is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrush, or wild corndog, in American English as reed, cattail, or punks, in Australia as cumbungi or bulrush, in Canada as bulrush or cattail, and in New Zealand as raupō. Other taxa of plants may be known as bulrush, including some sedges in Scirpus and related genera.

<i>Cyperus papyrus</i> aquatic flowering plant species

Cyperus papyrus is a species of aquatic flowering plant belonging to the sedge family Cyperaceae. It is a tender herbaceous perennial, native to Africa, and forms tall stands of reed-like swamp vegetation in shallow water.

Types of marshes

A salt marsh in Scotland Culbin Salt Marsh - - 185128.jpg
A salt marsh in Scotland

Marshes differ depending mainly on their location and salinity. Both of these factors greatly influence the range and scope of animal and plant life that can survive and reproduce in these environments. The three main types of marsh are salt marshes, freshwater tidal marshes, and freshwater marshes. [3] These three can be found worldwide and each contains a different set of organisms.

Salinity The proportion of salt dissolved in a body of water

Salinity is the saltiness or amount of salt dissolved in a body of water, called saline water. This is usually measured in . Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water.

Tidal marsh Marsh subject to tidal change in water

A tidal marsh is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes experience many overlapping persistent cycles, including diurnal and semi-diurnal tides, day-night temperature fluctuations, spring-neap tides, seasonal vegetation growth and decay, upland runoff, decadal climate variations, and centennial to millennial trends in sea level and climate. They are also impacted by transient disturbances such as hurricanes, floods, storms, and upland fires.

Freshwater marsh type of marsh

A freshwater marsh is a marsh that contains fresh water. Freshwater marshes are usually found near the mouths of rivers and are present in areas with low drainage. It is the counterpart to the salt marsh, an upper coastal intertidal zone of bio-habitat which is regularly flushed with sea water.

Salt marshes

Saltwater marshes are found around the world in mid to high latitudes, wherever there are sections of protected coastline. They are located close enough to the shoreline that the motion of the tides affects them, and, sporadically, they are covered with water. They flourish where the rate of sediment buildup is greater than the rate at which the land level is sinking. [3] Salt marshes are dominated by specially adapted rooted vegetation, primarily salt-tolerant grasses. [6]

Latitude The angle between zenith at a point and the plane of the equator

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the precise location of features on the surface of the Earth. On its own, the term latitude should be taken to be the geodetic latitude as defined below. Briefly, geodetic latitude at a point is the angle formed by the vector perpendicular to the ellipsoidal surface from that point, and the equatorial plane. Also defined are six auxiliary latitudes which are used in special applications.

Tide The periodic change of sea levels caused by the gravitational and inertial effects of the Moon, the Sun and the rotation of the Earth

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.

Salt marshes are most commonly found in lagoons, estuaries, and on the sheltered side of shingle or sandspit. The currents there carry the fine particles around to the quiet side of the spit and sediment begins to build up. These locations allow the marshes to absorb the excess nutrients from the water running through them before they reach the oceans and estuaries. [3] These marshes are slowly declining. Coastal development and urban sprawl has caused significant loss of these essential habitats. [7]

Lagoon A shallow body of water separated from a larger body of water by barrier islands or reefs

A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world.

Urban sprawl expansion of auto-oriented, low-density development in suburbs

Urban sprawl or suburban sprawl mainly refers to the unrestricted growth in many urban areas of housing, commercial development, and roads over large expanses of land, with little concern for urban planning. In addition to describing a particular form of urbanization, the term also relates to the social and environmental consequences associated with this development. In Continental Europe the term "peri-urbanisation" is often used to denote similar dynamics and phenomena, although the term urban sprawl is currently being used by the European Environment Agency. There is widespread disagreement about what constitutes sprawl and how to quantify it. For example, some commentators measure sprawl only with the average number of residential units per acre in a given area. But others associate it with decentralization, discontinuity, segregation of uses, and so forth.

Freshwater tidal marshes

Although considered a freshwater marsh, this form of marsh is affected by the ocean tides. However, without the stresses of salinity at work in its saltwater counterpart, the diversity of the plants and animals that live in and use freshwater tidal marshes is much higher than in salt marshes. The most serious threats to this form of marsh are the increasing size and pollution of the cities surrounding them. [3]

Freshwater marshes

A wet meadow adjacent to Big Bear Lake, San Bernardino Mountains, California MeadowInBigBear.JPG
A wet meadow adjacent to Big Bear Lake, San Bernardino Mountains, California

Ranging greatly in both size and geographic location, freshwater marshes make up the most common form of wetland in North America. They are also the most diverse of the three types of marsh. Some examples of freshwater marsh types in North America are:

Wet meadows

Wet meadows occur in areas such as shallow lake basins, low-lying depressions, and the land between shallow marshes and upland areas. They also occur on the edges of large lakes and rivers. Wet meadows often have very high plant diversity and high densities of buried seeds. [6] [8] They are regularly flooded but are often dry in the summer.

Vernal pools

Vernal pools are a type of marsh found only seasonally in shallow depressions in the land. They can be covered in shallow water, but in the summer and fall, they can be completely dry. In western North America, vernal pools tend to form in open grasslands, [9] whereas in the east they often occur in forested landscapes. [10] Further south, vernal pools form in pine savannas and flatwoods. Many amphibian species depend upon vernal pools for spring breeding; these ponds provide habitat free from fish which eat the eggs and young of amphibians. [6] An example is the endangered gopher frog (Rana sevosa). [11] Similar temporary ponds occur in other world ecosystems, where they may have local names. However, the term vernal pool can be applied to all such temporary pool ecosystems. [6]

Playa lakes

Playa lakes are a form of shallow freshwater marsh that occurs in the southern high plains of the United States. [12] Like vernal pools, they are only present at certain times of the year and generally have a circular shape. [13] As the playa dries during the summer, conspicuous plant zonation develops along the shoreline. [14]

Prairie potholes

Aerial view of prairie potholes Prairie Pothole Wetlands.jpg
Aerial view of prairie potholes

Prairie potholes are found in the northern parts of North America as the Prairie Pothole Region. These landscapes were once covered by glaciers, and as a result shallow depressions were formed in great numbers. These depressions fill with water in the spring. They provide important breeding habitats for many species of waterfowl. Some pools only occur seasonally while others retain enough water to be present all year. [15]

Riverine wetlands

Many kinds of marsh occur along the fringes of large rivers. The different types are produced by factors such as water level, nutrients, ice scour, and waves. [16]

Embanked marshlands

Large tracts of tidal marsh have been embanked and artificially drained. They are usually known by the Dutch name of polders. In Northern Germany and Denmark they are called Marschland or marsk, in France marais maritime. In Holland they are also designated as marine clay districts. In East-Anglia the embanked marshes are known as Fens.


Some areas of the world have already lost 90% of their wetlands, including marshes. They have been drained to create agricultural land or filled to accommodate urban sprawl. Restoration is the process of returning marshes to the landscape to replace those lost in the past. [1] Restoration can be done on a large scale, such as by allowing rivers to flood naturally in the spring, or on a small scale by returning wetlands to urban landscapes.

See also

Related Research Articles

Swamp A forested wetland

A swamp is a wetland that is forested. Many swamps occur along large rivers where they are critically dependent upon natural water level fluctuations. Other swamps occur on the shores of large lakes. Some swamps have hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodic inundation or soil saturation. The two main types of swamp are "true" or swamp forests and "transitional" or shrub swamps. In the boreal regions of Canada, the word swamp is colloquially used for what is more correctly termed a bog, fen, or muskeg. The water of a swamp may be fresh water, brackish water or seawater. Some of the world's largest swamps are found along major rivers such as the Amazon, the Mississippi, and the Congo.

Aquatic plant plant that has adapted to living in an aquatic environment

Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or macrophytes. A macrophyte is an aquatic plant that grows in or near water and is either emergent, submergent, or floating, and includes helophytes. In lakes and rivers macrophytes provide cover for fish and substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife.

Salt marsh A coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides

A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.

Littoral zone Part of a sea, lake or river that is close to the shore

The littoral zone or nearshore is the part of a sea, lake or river which is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to mean the same as the intertidal zone. However, the meaning of "littoral zone" can extend well beyond the intertidal zone.

Body of water Any significant accumulation of water, generally on a planets surface

A body of water or waterbody is any significant accumulation of water, generally on a planet's surface. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as ponds, wetlands, or more rarely, puddles. A body of water does not have to be still or contained; rivers, streams, canals, and other geographical features where water moves from one place to another are also considered bodies of water.

A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention.

Vernal pool Seasonal pools of water that provide habitat for distinctive plants and animals

Vernal pools, also called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland usually devoid of fish, and thus allow the safe development of natal amphibian and insect species unable to withstand competition or predation by fish. Certain tropical fish lineages have however adapted to this habitat specifically.

Aquatic ecosystem An ecosystem in a body of water

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

A lake ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions.

Wet meadow type of wetland

A wet meadow is a type of wetland with soils that are saturated for part or all of the growing season. Debate exists whether a wet meadow is a type of marsh or a completely separate type of wetland. Wet prairies and wet savannas are hydrologically similar. Wet meadows may occur because of restricted drainage or the receipt of large amounts of water from rain or melted snow. They may also occur in riparian zones and around the shores of large lakes.

<i>Lobelia dortmanna</i> species of plant

Lobelia dortmanna is an aquatic stoloniferous herbaceous perennial aquatic plant with basal rosettes, and flower stalks growing to 70–200 cm tall. The flowers are 1–2 cm long, with a five-lobed white to pale pink or pale blue corolla, produced one to ten on an erect raceme held above the water surface. The fruit is a capsule 5–10 mm long and 3–5 mm wide, containing numerous small seeds.

<i>Pontederia cordata</i> species of plant

Pontederia cordata, common name pickerelweed (USA) or pickerel weed (UK), is a monocotyledonous aquatic plant native to the American continent. It grows in a variety of wetlands, including pond and lake margins across an extremely large range from eastern Canada south to Argentina. A few examples include northern rivers, the Everglades and Louisiana.

<i>Sparganium eurycarpum</i> species of plant

Sparganium eurycarpum is a species of bur-reed known by the common names broadfruit bur-reed and giant bur-reed. It is native to wetlands in Eurasia and North America. It is a clonal perennial, spreading by below-ground rhizomes. The common name, bur-reed, arises from the distinctive round clusters of fruits that take the form of a mace. It can be distinguished from all other species of bur-reed by the presence of two stigmas.

Pond A relatively small body of standing water

A pond is an area filled with water, either natural or artificial, that is usually smaller than a lake. It may arise naturally in floodplains as part of a river system, or be a somewhat isolated depression. It may contain shallow water with marsh and aquatic plants and animals.

Reedy Lake lake in Victoria, Australia

Reedy Lake, historically also known as Lake Reedy, is a shallow 5.5-square-kilometre (2.1 sq mi) intermittent freshwater lake or swamp on the lower reaches of the Barwon River, on the Bellarine Peninsula southeast of Geelong in the Australian state of Victoria.

Salt pannes and pools Water retaining depressions located within salt and brackish marshes

Salt pannes and pools are water retaining depressions located within salt and brackish marshes. Pools tend to retain water during the summer months between high tides, whereas pannes generally do not. Salt pannes generally start when a mat of organic debris is deposited upon existing vegetation, killing it. This creates a slight depression in the surrounding vegetation which retains water for varying periods of time. Upon successive cycles of inundation and evaporation the panne develops an increased salinity greater than that of the larger body of water. This increased salinity dictates the type of flora and fauna able to grow within the panne. Salt pools are also secondary formations, though the exact mechanism(s) of formation are not well understood; some have predicted they will increase in size and abundance in the future due to rising sea levels.

Slough (hydrology) term in hydrology

A slough is a wetland, usually a swamp or shallow lake, often a backwater to a larger body of water. Water tends to be stagnant or may flow slowly on a seasonal basis.

<i>Panicum hemitomon</i> species of plant

Panicum hemitomon is a species of grass known by the common name maidencane. It is native to North America, where it occurs along the southeastern coastline from New Jersey to Texas. It is also present in South America.


  1. 1 2 3 4 5 Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p
  2. World Encyclopedia. "Marshes". Archived from the original on 23 May 2013. Retrieved 4 February 2012.
  3. 1 2 3 4 5 6 Rafferty, J.P. (2011). Lakes and Wetlands. New York, N.Y.: Britannica Educational service publishing's.
  4. Campbell & Reece (2008). Biology Eighth Edition. San Francisco, CA: Pearson Education Inc. p. 1162.
  5. Draper & Reed (2005). Our Environment. Nelson Education ltd. p. 96.
  6. 1 2 3 4 Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p.
  7. B.R. Silliman, E.D. Grosholz, and M.D. Bertness (eds.) 2009. Human Impacts on Salt Marshes. A Global Perspective. University of California Press, Berkeley, California.
  8. Keddy, P.A. and A. A. Reznicek. 1986. Great Lakes vegetation dynamics: the role of fluctuating water levels and buried seeds. Journal of Great Lakes Research 12: 25-36.
  9. Bauder, E. T. 1989. Drought stress and competition effects on the local distribution of Pogogyne abramsii. Ecology 70: 1083–9.
  10. Calhoun, A.J.K. and P.G. deMaynadier. 2008. Science and the Conservation of Vernal Pools in Northeastern North America. CRC Press, Boca Raton, Florida.
  11. Richter, S. C. and Seigel, R. A. 2002. Annual variation in the population ecology of the endangered gopher frog, Rana sevosa Goin and Netting. Copeia, 2002, 962–72.
  12. Smith, L. M. 2003. Playas of the Great Plains. Austin, TX: University of Texas Press.
  13. United States Environmental Protection Agency. "Playa Lakes". Archived from the original on 4 February 2012. Retrieved 5 February 2012.
  14. Bolen, E. G., Smith, L. M., and Schramm, H. L., Jr. 1989. Playa lakes: prairie wetlands of the southern High Plains. BioScience 39: 615–23.
  15. van der Valk, A. G. 1989. Northern Prairie Wetlands. Ames, IA: Iowa State University Press.
  16. Day, R., P.A. Keddy, J. McNeill and T. Carleton. 1988. Fertility and disturbance gradients: a summary model for riverine marsh vegetation. Ecology 69: 1044-1054