Tidal salt marsh at Ella Nore - geograph

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

marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...

found along rivers,

coast A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

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 environm ...

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 ...

of the adjacent estuary,

sea A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

.
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. The state of tidal marshes can be dependent on both natural and anthropogenic processes. In recent periods, human practices, small and large scale, have caused changes in ecosystems that have had a significant impact on the preservation of tidal marsh ecosystems. Some smaller scale changes include headward (i.e. upstream) erosion and coastal development. Large system changes include

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

and

sea level rise The sea level has been rising from the end of the last ice age, which was around 20,000 years ago. Between 1901 and 2018, the average sea level rose by , with an increase of per year since the 1970s. This was faster than the sea level had e ...

(from

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

). These changes are all putting pressure on tidal marshes.

Types

Tidal marshes can be found in two main places: coasts and estuaries. Coastal tidal marshes lie along coasts and estuarine tidal marshes lie inland within the tidal zone. 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. Estuarine tidal marshes are found in estuaries, areas where freshwater streams flow into brackish areas. They can be categorized based on salinity level, elevation, and sea level. Tidal marshes are commonly zoned into lower marshes (also called intertidal marshes) and upper/ high marshes, based on their elevation above sea level. A middle marsh zone also exists for freshwater tidal marshes. Location determines the controlling processes, age, disturbance regime, and future persistence of tidal marshes. Tidal marshes are differentiated into freshwater, brackish, and salt according to the salinity of their water.

Freshwater

Freshwater tidal marshes live more inland than saltwater marshes, but their proximity to the coast still allows for daily fluctuations from tides. The inland location allows for a majority of the water content to be from freshwater stream discharge, meaning the salt content is low. Tidal freshwater marshes are further divided into deltaic and fringing types. Extensive research has been conducted on deltaic tidal freshwater marshes in the

Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula, including parts of the Ea ...

, which were formed as a result of historic deforestation and intensive agriculture. Freshwater tidal marshes are highly productive and are home to a variety of organisms. There is a variety of vegetation that can reside in freshwater marshes. There is also a vast amount of insects which attract birds, such as wrens and warrens. Aquatic birds, such as ducks and herons, also live in these marshes. Freshwater tidal marshes also serve as spawning grounds for anadromous fish, such as shad and herring. These fish spend most of their lives in saltwater areas, but return to freshwater during reproduction. Tidal freshwater marshes are also highly productive, generate a large amount of good quality biomass. They also serve as good waste treatment areas, based on denitrification potential.

Saltwater

Saltwater tidal marshes live on coastlines in areas that are not completely exposed to the open ocean. The volume of water is dependent on the tides. Plant variation throughout marshes can be due to differences in tide exposure and frequency. Some different types include bottomland hardwood swamps, mangrove swamps, and palustrine wetlands. Saltwater tidal marshes are correlated with higher decomposition rates and lower denitrification rates.

Island and barrier island

Tidal Marshes also form between a main shoreline and

barrier island Barrier islands are a Coast#Landforms, coastal landform, a type of dune, dune system and sand island, where an area of sand has been formed by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of an ...

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) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

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

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

. Their areas are spawning grounds and home to "feeder fish" that lie low on the

food chain A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...

, 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 Connecticut ( ) is a U.S. state, state in the New England region of the Northeastern United States. It borders Rhode Island to the east, Massachusetts to the north, New York (state), New York to the west, and Long Island Sound to the south. ...

, U.S. Other ecosystem services include their role as significant

carbon sink A carbon sink is a natural or artificial carbon sequestration process that "removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere". These sinks form an important part of the natural carbon cycle. An overar ...

s 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, ...

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 is one of the leading threats to tidal marshes caused by

global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

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. It plays a crucial role in Climate change mitigation, limiting climate change by reducing the amount of Carbon dioxide in Earth's atmosphere, carbon dioxide in the atmosphe ...

), hydrologic responses, and wildlife community responses.

Gallery

File:Marsh tides high.png, alt=An illustration of a salt marsh at mean high tide., At high tide. File:Marsh tides mean.png, alt=An illustration of a salt marsh at mean tide., At mean tide. File:Marsh tides low.png, alt=An illustration of a salt marsh at mean low tide., At low tide. File:Marsh tides spring.png, alt=An illustration of a salt marsh at spring high tide., At spring high tide.

References

External links

Tidal freshwater marsh
{{Wetlands Coastal geography Marshes