Tidal salt marsh at Ella Nore - geograph

A tidal marsh (also known as a type of "tidal wetland") is a

marsh A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found ...

found along rivers,

coast The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

s and

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environme ...

which floods and drains by the

tidal movement Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables can ...

of the adjacent estuary,

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...

.
U.S. Environmental Protection Agency: Tidal marshes Tidal marshes experience many overlapping persistent cycles, including Diurnal cycle, 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. Tidal marshes are formed in areas that are sheltered from waves (such as beside edges of bays), in upper slops of intertidal, and where water is fresh or saline. They are also impacted by transient disturbances such as hurricanes, floods, storms, and upland fires.

Types

Tidal marshes are differentiated into freshwater, brackish and

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

according to the salinity of their water. Coastal marshes lie along coasts and estuarine marshes lie inland within the tidal zone. Location determines the controlling processes, age, disturbance regime, and future persistence of tidal marshes. Tidal freshwater marshes are further divided into deltaic and fringing types. Extensive research has been conducted on deltaic tidal freshwater marshes in

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The Bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula (including the parts: the Eastern Shore of Maryland / ...

, which were formed as a result of historic

deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...

and

intensive agriculture Intensive agriculture, also known as intensive farming (as opposed to extensive farming), conventional, or industrial agriculture, is a type of agriculture, both of crop plants and of animals, with higher levels of input and output per unit of ag ...

. Tidal marshes can be further categorized by salinity level, elevation, and sea level."Responding to Changes in Sea Level", by Marine Board, Marine Board, National Research Council (U.S.
p. 65
/ref> Tidal marshes are commonly zoned into lower marshes (also called intertidal marshes) and upper or high marshes, based on their elevation above sea level. A middle marsh zone also exists for tidal freshwater marshes. Tidal marshes may be further classified into back-barrier marshes, estuarine brackish marshes and tidal freshwater marshes, depending on the influence of sea level.

Coastal

Coastal tidal marshes are found within coastal watersheds and encompass a variety of types including fresh and salt marshes, bottomland hardwood swamps, mangrove swamps, and palustrine wetlands.

Island and barrier island

Tidal Marshes also form between a main shoreline and

barrier island Barrier islands are coastal landforms and a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from a ...

s. These elongated shifting landforms evolve parallel and in close proximity to the shoreline of a tidal marsh. Many become fully submerged at high tide, and become directly attached to the mainland when at low tide. Barrier island formation includes mechanisms such as offshore bar theory, spit accretion theory, and climate change.

Ecosystem services

Tidal marsh

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

s provide numerous services, including supplying habitats to support a diverse range of

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...

. Their areas are spawning grounds and home to "feeder fish" that lie low on the food chain, and serve as crucial rest-stops for migratory birds. Additionally, they provide suitable habitat to various tidal salt marsh specialist bird species, such as the seaside sparrow (''Ammospiza maritima'') and the willet (''Tringa semipalmata'') found in tidal marshes in Connecticut, U.S. Other ecosystem services include their role as significant carbon sinks and shoreline stabilizers. Tidal marshes provide flood protection to upland areas by storing ground water, and lessen the impact of

storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the ...

s on nearby shorelines. Tidal marshes located along coastlines also act as intricate filtration systems for watersheds. These areas absorb and trap pollutants from water run-off that travels from higher elevations to open water.

Anthropogenic threats

Historically, the global loss of tidal marshes can be attributed to the implementation of tidal restrictions and other draining activities. Tidal restrictions methods include diking, tide gates, and impoundments, which were implemented on coastal lands internationally in favour of creating agricultural land, as exemplified with large-scale diking that has occurred in Atlantic Canada and the U.S. (e.g. in The Bay of Fundy). Historical changes (due to anthropogenic activity) to tidal marshes have a lasting impact on them today. Tidal marshes have experienced the

Gold Rush A gold rush or gold fever is a discovery of gold—sometimes accompanied by other precious metals and rare-earth minerals—that brings an onrush of miners seeking their fortune. Major gold rushes took place in the 19th century in Australia, New ...

which filled some marshes with sediment due to erosion. Logging has also damaged tidal marshes due to their decomposition and filling of marshes. Tidal marshes sensitivity to anthropogenic activity have created long lasting affects. Currently,

rising sea levels Rising may refer to: * Rising, a stage in baking - see Proofing (baking technique) *Elevation * Short for Uprising, a rebellion Film and TV * "Rising" (''Stargate Atlantis''), the series premiere of the science fiction television program ''Starg ...

is one of the leading threats to tidal marshes caused by

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

and climate change. Pollution due to urbanization also continues to endanger tidal marsh ecosystems.

Restoration

Restoration of tidal marshes through the removal of tidal restrictions to re-establish degraded ecosystem services have been underway internationally for decades. Deliberate and natural restoration practices have occurred in the U.S., United Kingdom, Europe, and Canada. Research shows that tidal marsh restoration can be evaluated through various factors, such as vegetation, biogeochemical responses (e.g. salinity, sediment deposition, pH, and

carbon sequestration Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in lan ...

), hydrologic responses, and wildlife community responses.

References

External links

Tidal freshwater marsh
{{Wetlands Coastal geography Marshes