A freshwater marsh is a non-forested marsh wetland that contains shallow fresh water, and is continuously or frequently flooded. [1] [2] Freshwater marshes primarily consist of sedges, grasses, and emergent plants. [3] [4] Freshwater marshes are usually found near the mouths of rivers, along lakes, or are present in low lying areas with low drainage like abandoned oxbow lakes. [5] [2] Unlike its counterpart the salt marsh, which is regularly flushed with sea water, freshwater marshes receive the majority of their water from surface water. [6]
Freshwater marshes are highly productive and therefore can support a large biodiversity of vegetation. Vegetation is a key component in determining the structure of a freshwater marsh. [7] In a freshwater marsh, there are emergent plants, floating plants, floating leaved and submerged. [8] The primary plant in freshwater marshes are emergent plants. Emergent plants are plants with soft stems and are highly adapted to live in saturated soils. [1] Freshwater marshes have a lengthy growing season and contain high nutrient levels in the water and substrate, which contribute to an overall high net primary production. [9] Some of the most common plants in these areas are cattails, water lilies, arrowheads, and rushes. [10]
Many types of animals use freshwater marshes for habitat at some point in their life cycles. Birds, amphibians, reptiles, fish and macro-invertebrates can be found within freshwater marshes. [11] Birds use freshwater marshes for nesting. Common species of birds found in a freshwater marsh include ducks, geese, swans, songbirds, swallows, coots, and black ducks. Although shallow marshes do not tend to support many fish, they are used as a nursery to raise young. The deeper ones are home to many species, including large fish such as the northern pike and carp.
Soils in freshwater marshes are considered hydric; soils that are saturated during the growing season and have anaerobic, or no oxygen, conditions due to the saturation. [12] The soils in freshwater marshes have high organic matter due to slow decomposition rates and are often black or brown. [8] [13] The anaerobic conditions of the soils are caused by microbial activity that deplete oxygen, which are then reverted to anaerobic processes that accumulate or deplete reduced iron and other minerals creating distinct soil morphology characteristics. [12]
Freshwater marshes are dynamic ecosystems. Aspects of the water like depth, velocity, oxygen concentration, and temperature change frequently. [7] Marshes can be classified based on their hydrology. Marshes can be flooded permanently, intermittently, temporarily, seasonally, and semi-permanently. [7] Groundwater reserves, water moving across the surface and precipitation are the three main sources of water in marshes. [11]
Wetlands have many services and functions that benefit the Earth. Marshes can remove carbon from the atmosphere and store it in their biomass or the ground, called carbon sequestration. [14] Fresh water marshes hold a significant amount of the worlds organic carbon, as much as a third. [15] In addition to carbon, other elements including carbon, nitrogen, phosphorus, sulfur, and iron, are cycled and transformed in freshwater marshes. These elements enter the system through water or from the atmosphere. Once in the wetland, they are transformed from photosynthesis, microbial processes such as nitrogen fixation and denitrification, or redoximorphic processes. [16] Freshwater marshes also assist with particle retention. Freshwater marshes have little to no movement in water, allowing for the sediment and particulates suspended in the water from erosion and overland flow to settle out of the water accumulating in the wetland. [16]
Freshwater marshes can also support and provide services to humans. Many different types of food are produced within a freshwater marsh like fruits, rice, fish, and vegetables such as taro. [14] Freshwater marshes can also provide clothing in the form of pelts and materials for building such as reeds. [14] Freshwater marshes also provide recreational services like fishing, bird-watching, water fowl hunting, and trapping. [14] Another important function of marshes is flood mitigation. Marshes can slow down the rate at which water is traveling and create a buffer zone to stop flooding. [14]
Freshwater marshes can be broken into several types including river marshes, lacustrine (lake), tidal freshwater, and palustrine depressional. [17] Subtypes of these wetland types can be used to further specify the type of freshwater marsh based on vegetation, hydrology or location. [18]
River marshes are typically found within the floodplain or delta of rivers, where the wetland receives water from the river. The majority of these wetlands only receive water seasonally, when the river is highest, but there are river marshes found where the river empties into deserts with no outlet. [2]
Lacustrine marshes are found at the edges of lakes where the lakes transition from deep water to upland or other wetlands. The hydrology of lacustrine marshes are dependent on the hydrology of the surrounding area. [2]
Tidal freshwater marshes occur nearby tidal influences but receive most of their water from groundwater or streams. The wetlands mostly occur nearby brackish marshes where the salt water gradient decreases through those systems, therefore the freshwater tidal marshes are only affected by the tides through water levels but do not receive the salt water. [2]
Palustrine depressional marshes, sometimes also called basin or slope marshes, occur in hydrologically isolated areas such as a depression or on a hill slope. These marshes are not connected to rivers, lakes or oceans, but can be and frequently are fed by groundwater springs or seepages. [2] Within the category of palustrine, there are several subcategories that are based on the location or function of the marsh. These include but are not limited to vernal pools, playas or playa lakes, and prairie potholes. [2]
Wetlands are frequently being destroyed for development, agriculture, and other uses. Wetlands have decreased by as much as 50% since 1900 and in some parts of the world by 90%. [19] [20] Inland wetlands, freshwater marshes making up about 20-25% of all freshwater wetlands globally, [21] have been decreasing approximately 1.2% each year throughout the last century (since 1900). [22] [23]
Wetland restoration, or bringing back the wetland and its functions, [24] is an important step in conservation of freshwater marshes. Restoration can take two forms, re-establishment or rehabilitation. [24] One common way freshwater marshes are restored is restoration of channelized rivers. [23] When rivers are channelized and straightened, the marshes alongside the rivers disappear. Reverting rivers back to their natural state will allow nearby marshes to form again. [23] Another way to restore freshwater marshes is to break down levees, dikes, and berms that impede rivers from flooding.
The Florida Everglades represent the largest contiguous freshwater marsh in the entire world. [25] This immense marsh covers 4,200 square miles (11,000 km2) and is located in the southern tip of Florida. The Everglades is home to animals such as the American Alligator, the Apple Snail and the Everglade Snail Kite. [7] Alligators create depressions in the mud that retain water during the dry season. These wet depressions or alligator holes are important to fish, reptiles, and amphibians during the dry season. [7] The vegetation of the Everglades include grasses, sedges, and other emergent hydrophytes. [26] Continued human development, including drainage for development and polluted agriculture runoff, as well as alterations in the water cycle, threaten the existence of the Everglades.
The Okavango Delta in Botswana is one of Africa's largest freshwater marshes. Before the flowing water reaches the Okavango Delta, it comes from Angola and passes through Namibia. [7] This marsh is so large that it can support commercial and recreational fishing. [7] There are many tree islands within the Okavango marsh due to termites. Termites colonies build mounds in the dry season that later become flooded. The crowns of the mounds stay above water level and can support trees and other vegetation. [7] The tree islands become a hot spot for biodiversity within the marsh. [7] Continuous proposals for rerouting the river that fills the marsh is the main cause of concern for the future of this wetland. [7]
In Eastern Africa, the Rift Valley contains marshlands. Lake Naivasha is surrounded by tropical, freshwater marshes in the extensive 6,500 kilometer rift valley. [27] These marshes are home to cattail, papyrus, and floating mats of other plants. [27] This marsh is also home to ducks, herons, and crayfish. [27] The rifting in the valley is enlarging the lake, creating more wetlands in the surrounding area. [27]
The Mesopotamian Marshlands are located in southern Iraq and Iran. [27] The confluence of the Tigris and Euphrates Rivers create the Mesopotamian Marshlands. [27] The Mesopotamian Marshlands were once the largest wetland ecosystem in the Middle East, covering an area of 15,000 to 20,000 square kilometers. [27] In the 1980s and 1990s, this marshland was drained by upstream dams and water control structures, down to 10% of the original area. [27] The marshland is located on the intercontinental flyway of migratory birds and is used by two-thirds of West Asia's water fowl. [27] The marsh is currently dominated by an invasive grass, Phragmites australis. [27]
A swamp is a forested wetland. Swamps are considered to be transition zones because both land and water play a role in creating this environment. Swamps vary in size and are located all around the world. The water of a swamp may be fresh water, brackish water, or seawater. Freshwater swamps form along large rivers or lakes where they are critically dependent upon rainwater and seasonal flooding to maintain natural water level fluctuations. Saltwater swamps are found along tropical and subtropical coastlines. 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 formally termed a bog, fen, or muskeg. Some of the world's largest swamps are found along major rivers such as the Amazon, the Mississippi, and the Congo.
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently for years or decades or seasonally for a shorter periods. Flooding results in oxygen-free anoxic processes prevailing, especially in the soils. The primary factor that distinguishes wetlands from terrestrial land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique anoxic hydric soils. Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide. Constructed wetlands are designed and built to treat municipal and industrial wastewater as well as to divert stormwater runoff. Constructed wetlands may also play a role in water-sensitive urban design.
A fen is a type of peat-accumulating wetland fed by mineral-rich ground or surface water. It is one of the main types of wetlands along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as mires. The unique water chemistry of fens is a result of the ground or surface water input. Typically, this input results in higher mineral concentrations and a more basic pH than found in bogs. As peat accumulates in a fen, groundwater input can be reduced or cut off, making the fen ombrotrophic rather than minerotrophic. In this way, fens can become more acidic and transition to bogs over time.
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that grows in or near water and is either emergent, submergent, or floating. In lakes and rivers macrophytes provide cover for fish, substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife.
A marsh is — according to ecological definitions — a wetland that is dominated by herbaceous rather than woody plant species. More in general, the word can be used for any low-lying and seasonally waterlogged terrain. In Europe and in agricultural literature low-lying meadows that require draining and embanked polderlands are also referred to as marshes or marshland.
The Sudd is a vast swamp in South Sudan, formed by the White Nile's Baḥr al-Jabal section. The Arabic word sudd is derived from sadd, meaning "barrier" or "obstruction". The term "the sudd" has come to refer to any large solid floating vegetation island or mat. The area which the swamp covers is one of the world's largest wetlands and the largest freshwater wetland in the Nile Basin.
The Okavango River, is a river in southwest Africa. It is known by this name in Botswana, and as Cubango in Angola, and Kavango in Namibia. It is the fourth-longest river system in southern Africa, running southeastward for 1,600 km (1,000 mi). It begins at an elevation of 1,300 metres (4,300 ft) in the sandy highlands of Angola. Farther south, it forms part of the border between Angola and Namibia, and then flows into Botswana. The Okavango does not have an outlet to the sea. Instead, it discharges into the Okavango Delta or Okavango Alluvial Fan, in an endorheic basin in the Kalahari Desert. The Cuito River is a major tributary.
In usage in the Southern United States, a bayou is a body of water typically found in a flat, low-lying area. It may refer to an extremely slow-moving stream, river, marshy lake, wetland, or creek. They typically contain brackish water highly conducive to fish life and plankton. Bayous are commonly found in the Gulf Coast region of the southern United States, especially in the Mississippi River Delta, though they also exist elsewhere.
Freshwater ecosystems are a subset of Earth's aquatic ecosystems. They include lakes, ponds, rivers, streams, springs, bogs, and wetlands. They can be contrasted with marine ecosystems, which have a larger salt content. Freshwater habitats can be classified by different factors, including temperature, light penetration, nutrients, and vegetation. There are three basic types of freshwater ecosystems: Lentic, lotic and wetlands. Freshwater ecosystems contain 41% of the world's known fish species.
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.
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Freshwater ecosystems may be lentic ; lotic ; and wetlands.
Lake Apopka is the fourth largest lake in the U.S. state of Florida. It is located 15 miles (24 km) northwest of Orlando, mostly within the bounds of Orange County, although the western part is in Lake County. Fed by a natural spring, rainfall and stormwater runoff, water from Lake Apopka flows through the Apopka-Beauclair Canal and into Lakes Beauclair and Dora. From Lake Dora, water flows into Lake Eustis, then into Lake Griffin and then northward into the Ocklawaha River, which flows into the St. Johns River. Multiple parks or nature trails are present around the lake including Magnolia Park, Lake Apopka Wildlife Drive, Ferndale Preserve, Oakland Nature Preserve, Dr. Bradford Memorial Park, and Newton Park, named for A. B. Newton.
Palustrine wetlands include any inland wetland that contains ocean-derived salts in concentrations of less than 0.5 parts per thousand, and is non-tidal. The word palustrine comes from the Latin word palus or marsh. Wetlands within this category include inland marshes and swamps as well as bogs, fens, pocosins, tundra and floodplains.
Freshwater biology is the scientific biological study of freshwater ecosystems and is a branch of limnology. This field seeks to understand the relationships between living organisms in their physical environment. These physical environments may include rivers, lakes, streams, ponds, lakes, reservoirs, or wetlands. Knowledge from this discipline is also widely used in industrial processes to make use of biological processes involved with sewage treatment and water purification. Water presence and flow is an essential aspect to species distribution and influences when and where species interact in freshwater environments.
Wetland conservation is aimed at protecting and preserving areas of land including marshes, swamps, bogs, and fens that are covered by water seasonally or permanently due to a variety of threats from both natural and anthropogenic hazards. Some examples of these hazards include habitat loss, pollution, and invasive species. Wetland vary widely in their salinity levels, climate zones, and surrounding geography and play a crucial role in maintaining biodiversity, ecosystem services, and support human communities. Wetlands cover at least six percent of the Earth and have become a focal issue for conservation due to the ecosystem services they provide. More than three billion people, around half the world's population, obtain their basic water needs from inland freshwater wetlands. They provide essential habitats for fish and various wildlife species, playing a vital role in purifying polluted waters and mitigating the damaging effects of floods and storms. Furthermore, they offer a diverse range of recreational activities, including fishing, hunting, photography, and wildlife observation.
Classification of wetlands has been a problematical task, with the commonly accepted definition of what constitutes a wetland being among the major difficulties. A number of national wetland classifications exist. In the 1970s, the Ramsar Convention on Wetlands of International Importance introduced a first attempt to establish an internationally acceptable wetland classification scheme.
William Mitsch is an ecosystem ecologist and ecological engineer who was co-laureate of the 2004 Stockholm Water Prize in August 2004 as a result of a career in wetland ecology and restoration, ecological engineering, and ecological modelling.
An inland salt marsh is a saltwater marsh located away from the coast. It is formed and maintained in areas when evapotranspiration exceeds precipitation and/or when sodium- and chloride-laden groundwater is released from natural brine aquifers. Its vegetation is dominated by halophytic plant communities.
A peatland is a type of wetland whose soils consist of organic matter from decaying plants, forming layers of peat. Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logging and subsequent anoxia. Like coral reefs, peatlands are unusual landforms that derive mostly from biological rather than physical processes, and can take on characteristic shapes and surface patterning.
Coastal erosion in Louisiana is the process of steady depletion of wetlands along the state's coastline in marshes, swamps, and barrier islands, particularly affecting the alluvial basin surrounding the mouth of the Mississippi River. In the last century, coastal Louisiana has lost an estimated 4,833 square kilometers (1,866 sq mi) of land, approximately the size of Delaware's land area. Coastwide rates of wetland change have varied from −83.5 square kilometers (−32.2 sq mi) to −28.01 square kilometers (−10.81 sq mi) annually, with peak loss rates occurring during the 1970s. One consequence of coastal erosion is an increased vulnerability to hurricane storm surges, which affects the New Orleans metropolitan area and other communities in the region. The state has outlined a comprehensive master plan for coastal restoration and has begun to implement various restoration projects such as fresh water diversions, but certain zones will have to be prioritized and targeted for restoration efforts, as it is unlikely that all depleted wetlands can be rehabilitated.
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