Difference between revisions of "Salt marshes"

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This article describes the habitat of the salt marshes. It is one of the sub-categories within the section dealing with biodiversity of [[marine habitats and ecosystems]]. It gives an overview about the characteristics, distribution, evolution, zonation, succession, biota, threats, functioning and adaptations of the organisms that live in salt marshes.
 
  
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This article describes the habitat of salt marshes. It gives an introduction to the characteristics, distribution, evolution, [[zonation]], succession, biota, threats, functioning and adaptations of the organisms that live in salt marshes.
  
==Introduction==
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In 2008 the European Union commissioned a series of Habitat Management Models for several of the more important communities. Included is a model for habitat 1330 "Atlantic salt meadows" (Glauco-Puccinellietalia maritimae).
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Visit the European Union web site at [http://ec.europa.eu/environment/nature/natura2000/management/habitats/models_en.htm] to download a copy of the Habitat Management Model for the above community.
  
Salt marshes are defined as natural or semi-natural terrestrial '''halophytic''' ecosystems. It is an [[intertidal]] zone between land and the salty or brackish water. They replace [[mangroves]] in temperate and arctic regions. The dominant flora is composed of [[Halophytic plants|halophytic plant]] such as '''grasses''', '''shrubs''' and '''herbs'''. The flora is rather species poor. The sediment consists of [[mud]] and sand. The marshes are associated with [[mud]] flats. These [[Tidal flats from space|mud flats]] are dominated by [[algae]]. The salt marsh meadows are continuously covered and uncovered by seawater. The drainage of this seawater is controlled by a meandering network of '''tidal channels'''. Through these channels sediments, [[detritus]], dissolved [[nutrients]], [[plankton]] and small fishes are flushed in and out the salt marshes.
 
  
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==Introduction==
  
[[image:Saefringhe NIOO-CEME.jpg|center|thumb|300px|caption|Land of Saeftinghe - Belgium <ref>http://www.marbef.org</ref>]]
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Salt marshes are defined as natural or semi-natural terrestrial halophytic ecosystems that occur in the [[intertidal]] zone between the land and the sea and that are covered by salty or brackish water for at least part of the time. They can be considered, in some way, as the analogue of [[mangrove]]s in temperate and arctic regions. The dominant flora is composed of [[Halophytic plants|halophytic plant]]s such as grasses, shrubs and herbs. The flora is locally rather species poor, but the global species diversity is high, with over 500 salt marsh plant species known<ref name=S14>Silliman, B.R. 2014. Salt marshes. Current Biology 24(9) R348</ref>. Salt marshes are normally associated with [[mud]] flats but also occur on sand flats. These [[Tidal flats from space|mud flats]] are sometimes dominated by [[algae]] and covered with algal mats. They are periodically flooded by the tide, the height of which can vary from several centimetres in enclosed seas (such as the Baltic Sea) to several metres in open seas along the ocean margins. A network of meandering tidal creeks ensures the drainage of seawater. Through these channels, sediments, [[detritus]], dissolved [[nutrient]]s, [[plankton]] and small fishes are flushed in and out the salt marshes.
  
  
 
==Distribution==
 
==Distribution==
  
Salt marshes are widely distributed in [[Estuaries and tidal rivers|estuarine]] systems around the world. They have a range from the Arctic region over Europe, Africa, America, Asia to the coast of Australia.
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[[image:Distribution salt marshes.gif|left|thumb|500px|caption|Distribution of salt marshes (green), wetlands (orange and yellow) and mangroves (pink).]]
The most extensive development of these salt marshes occurs where rainfall is abundant, sediments are fine-grained and the climate is moderate.
 
 
 
 
 
[[image:Distribution salt marshes.gif|center|thumb|500px|caption|Distribution of salt marshes (green), wetlands (orange and yellow) and mangroves (pink) <ref>http://cache.eb.com/eb/image?id=6576&rendTypeId=4</ref>]]
 
  
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Salt marshes are ubiquitous in estuarine systems in temperate zones all over the world. They also occur in [[deltas]] and [[ria]]s but seldom on open coasts, because the development is inhibited by wave action. Although sediment is a prerequisite for their growth in height and width, salt marsh communities can occur in areas with limited or no sediment supply. Examples include seawater-drenched cliffs and slopes on exposed coasts, at the head of sea lochs and rocky beaches (Doody 2008<ref>Doody, J.P. 2008. Saltmarsh Conservation, Management and Restoration''. Coastal Systems and Continental Margins, Volume 12, Springer, 217 pp. </ref>). Salt marshes can be found from the Arctic region, over Europe, Africa, America, Asia to the coast of Australia. The most extensive development of salt marshes occurs in estuaries with a moderate climate, large tidal range, abundant fine-grained sediments and sheltered locations where particles can settle out of the water column.
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==Evolution==
 
==Evolution==
  
Salt marshes evolve over time from young marshes to old marshes. The '''young marshes''' consist for the largest part of low marsh cordgrass ''Spartina alterniflora''. [[Nutrients]] are transported by [[Tide|tidal]] flooding through the [[Tide|tidal]] channels. This makes it possible for the grasses to grow thickly and abundantly what weakens the effect of waves and tidal [[currents]] so the depositional rate of [[mud]] increases. [[Erosion]] is reduced by the roots and rhizomes of the plants. At the time that the marsh surface builds up above the high water level, the high marsh plants invade, outcompete and replace the low marsh plants. When the quantity of the low and high marshes is equal, the ecosystem is in a mature stage of development. The continued deposition of [[mud]] converts most of the low marshes into high marshes. These are called the '''old marshes'''. Little water flows through the tidal channels and the marshes are elevated. At this time, streams and rivers deposit sand and [[mud]] on these high marshes and convert it into a dry land that is disconnected from ocean influences. <ref>Pinet P.R. 1998.Invitation to Oceanography. Jones and Barlett Publishers. p. 508</ref>
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Salt marshes evolve over time from young marshes to old marshes. The natural young marshes in eastern USA are vegetated for the largest part with low marsh cordgrass ''Spartina alterniflora''. [[Nutrient]]s are transported by [[Tide|tidal]] currents through the [[Tide|tidal]] channels. This allows the grasses to grow thickly and profuse, so weakening the effect of waves and tidal [[currents]] and increasing the deposition rate of [[mud]]. [[Erosion]] is reduced by the roots and rhizomes of the plants. At the time that the marsh surface builds up above the high water level, high marsh species invade, outcompete and replace the low marsh plants. The most stress-tolerant plant species occupy the lower reaches of the marshes while competitive dominants occupy the upper elevations that are less stressful<ref name=S14/>. When the extent of the low and high marshes is about equal, the ecosystem is in a mature stage of development. The ongoing deposition of [[mud]] converts most of the low marshes into high marshes. Little water flows through the tidal channels of these elevated 'old marshes'. Deposition of sand and [[mud]] on these high marshes convert them into dry land that is disconnected from ocean influences<ref name=P98>Pinet P.R. 1998. Invitation to Oceanography. Jones and Barlett Publishers. p. 508</ref>. Lateral channel migration and wave attack at the base of marsh cliffs are the main mechanisms for erosion of mature salt marshes and their subsequent rejuvenation cycle<ref>Levoy, F., Anthony, E.J., Dronkers, J., Monfort, O. and Montreuil, A-L. 2019. Short-term to Decadal-scale Sand Flat Morphodynamics and Sediment Balance of a Megatidal Bay: Insight from Multiple LiDAR Datasets. Journal of Coastal Research SI 88: 61–76</ref><ref>Mariotti, G. and Fagherazzi, S. 2013. Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise, Proc. Natl. Acad. Sci. 110(14): 5353–5356</ref>, see also [[Dynamics, threats and management of salt marshes]] and [[French case studies: Upper tidal flat evolution in the bay of Mont-Saint-Michel (NW France)]].
  
  
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The requirements for development of salt marshes are:
 
The requirements for development of salt marshes are:
  
* They need '''fine-grained sediments'''.  
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* They need fine-grained sediments.  
* There may be '''no strong waves or tidal currents'''.  
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* There may be no strong waves or tidal currents.  
* They need salty conditions to grow. They are '''halotolerant''' and have adaptations to these conditions.  
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* They need salty conditions to grow. They are halotolerant and have adaptations to these conditions.  
* They need a temperate or cool '''temperature'''. Freezing temperatures can occur, but are not damaging the plants.
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* They need a temperate or cool temperature. Incidental freezing temperatures are not damaging the plants.
* They need a '''wide tidal range'''. This is important because it limits the [[erosion]], makes deposition of sediments possible and causes a well-marked zonation.
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* They need a wide tidal range. This is important because it limits the [[erosion]], makes deposition of sediments possible and causes a well-marked [[zonation]].
  
  
 
==Zonation==
 
==Zonation==
  
Based on the topography and characteristic plant assemblages, salt marshes are classified as low and high marshes. Below the '''low marshes''' are the [[Tide|tidal]] creeks. These creeks are channels that are flushed with salty or brackish water. The low marshes are the lower limit of the marshes and extend from the mean low water [[tide]] to the high water [[tide]]. It is dominated by the smooth cordgrass ''Spartina alterniflora''. This grass spreads rapidly.  
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The '''high marshes''' extend from the high water tide to the highest spring [[tide]]. It is only flooded during extremely high tides and during storms. It resembles more to terrestrial than to a true marine environment. The plant community is more diverse than the low marshes. It consists of ''Spartina patens'', the saltwort grass ''Salicornia'' species and the spike grass ''Distichlis spicata''. Distribution, density and activity of invertebrates are mainly controlled by protection, food and frequency of tidal flooding. <ref>Pinet P.R. 1998.Invitation to Oceanography. Jones and Barlett Publishers. p. 508</ref>
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[[image:ZonationSaltMarshes.jpg|left|thumb|400px|Zonation of salt marshes. Image credit: USGS]]
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Based on the topography and characteristic plant assemblages, salt marshes are classified as low, medium and high marshes. This classification is related to the number of tidal submergences per year (Adam 1990<ref name=A90>Adam, P., 1990. ''Saltmarsh Ecology''. Cambridge University Press, Cambridge</ref>). The 'low marshes' extend from the mean low water neap tide to the mean high water spring tide. The low marshes are drained by [[Tide|tidal]] creeks that convey flood and ebb flow; ebb flow generally dominates because flood water also enters the marsh directly from the main channels. The 'high marshes' extend from the mean high water level to the highest springtide level. Flooded only by the highest tides and during storms, they are more like a terrestrial than a true marine environment. The plant community is more diverse than on the low marshes. Typical high marsh species are cordgrass ''Spartina patens'', spike grass ''Distichlis spicata'' and species such as saltwort ''Salsola'' and seablite ''Suaeda''. Distribution, density and activity of invertebrates mainly depend on protection, food and frequency of tidal flooding. <ref name=P98/>  
  
  
[[image:Zonation salt marshes.jpg|center|thumb|400px|caption|Zonation of salt marshes <ref>http://geology.usgs.gov/connections/fws/landscapes/blackwater_model.htm</ref>]]
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{| border="0" align="center"
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[[File:SpartinaPatens.jpg|thumb|left|150px|''Spartina patens''  Credit T. Forney  www.pest.ceris.purdue.edu]]
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[[File:SalsolaKaliES.jpg|thumb|left|150px|''Salsola kali''  Credit Ed Stikvoort www.freenatureimages.eu]]
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[[File:SuaedaMaritima.jpg|thumb|left|150px|''Suaeda maritima''  Credit Ed Stikvoort www.freenatureimages.eu]]
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|}
  
  
 
==Succession==
 
==Succession==
  
Succession is the serial development of different vegetation types at one place in time.  
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Succession is the successive development in time of different vegetation types at one place. It is a complex process; the factors determining zonation and succession in salt marshes are discussed more in detail in Adam (1990<ref name=A90/>, pages 49-57), Gray (1992<ref>Gray, A.J. 1992. Saltmarsh plant ecology. In: ''Saltmarshes: morphodynamics, conservation and engineering significance'', J.R.L., Allen, & K., Pye, eds., 63-79. Cambridge University Press, Cambridge.</ref>) and Packham & Willis (1997, pages 107-114 <ref>Packham, J.R. & Willis, A.J., 1997. ''Ecology of dunes, saltmarsh and shingle''. Chapman & Hall, London.</ref>).
The succession starts with unicellular algae such as diatoms sticking the sand together by production of mucus. This causes a brownish biofilm on the substrate.  
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[[File:Biofilm.jpg|thumb|left|175px|Biofilm of unicellular algae <ref name="multiple"> Credit Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>]]
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[[File:Filamentous algae.JPG|thumb|left|175px|Fixation of the sediment by blue-green and green algae <ref name="multiple"/>]]
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The mudflat colonization starts with unicellular algae such as diatoms sticking the sand together by production of mucus. This causes a brownish biofilm on the substrate.  
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After this stage, filamentous [[algae]] contribute to the further fixation of sediments. These [[algae]] are mostly blue-green algae, Cyanophyta and Chlorophyta. Small gastropods can feed and develop in huge quantities on it. Locally, the filamentous alga ''Vaucheria'' can form banquettes or elevations. Brown algae can be associated with this stage.
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A next stage is the germination of species such as the glasswort ''Salicornia''. The seeds germinate after partial desalination of the soil by rain. Sedimentation between and around the glassworts contributes to elevating and stabilizing the substrate. Other species such as ''Spartina maritima'' and ''Spartina anglica'' compete for the same place. ''S. maritima'' is an indigenous species of continental Europe and ''S. anglica'' is imported from the British Islands. The hybridisation and invasion of "Spartina" spp is a worldwide phenomenon<ref>Strong, D.R. and Ayres, D.R. 2013. Ecological and Evolutionary Misadventures of Spartina. Annu. Rev. Ecol. Evol. Syst. 44: 23.1–23.22</ref>.
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{| border="0" align="center"
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[[File:SalicornaEuropaea.jpg|thumb|left|150px|''Salicorna europaea''  Credit Bart Vastenhouw,  www.freenatureimages.eu]]
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[[File:SpartinaMaritima.jpg|thumb|left|200px|''Spartina maritima''  Credit Ed Stikvoort  www.freenatureimages.eu]]
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[[File:SpartinaAnglica.jpg|thumb|left|150px|''Spartina anglica''  Credit Ed Stikvoort  www.freenatureimages.eu]]
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|}
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In Europe, other plants also occur. These are the herbs common saltmarsh-grass (''Puccinellia maritima''), sea plantain (''Plantago maritima''), sea arrow-grass (''Triglochin maritinum''), sea aster (''Aster tripolium''), danish scurvy-grass (''Cochlearia danica''), common sea-lavender (''Limonium vulgare''), sea purslane (''Halimione portulacoides''), the red alga ''Bostrychia scorpioides'' and ''Catenella caespitosa''. <ref>Eric Coppejans – Course Biodiversity of aquatic food webs: from algae to marine mammals UGent</ref>. ''Juncus maritimus'' is another species that can occur in salt marshes.
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Initial plant colonizers play an important role in the recovery of salt marsh vegetation from disturbance events. They provide shading of the substrate of bare areas and reduce salt accumulation in the soils and thereby facilitate colonization by many other plant species<ref name=S14/>.
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{| border="0" align="center"
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[[File:PuccinelliaMaritima.jpg|thumb|left|150px|''Puccinellia maritima''  Credit Peter Meininger  www.freenatureimages.eu]]
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[[File:PlantagoMaritima.jpg|thumb|left|150px|''Plantago maritima''  Credit Jeroen Willemsen www.freenatureimages.eu]]
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[[File:TriglochinMaritima.jpg|thumb|left|150px|''Triglochin maritima'' Credit Hans Boll www.freenatureimages.eu]]
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[[File:AsterTripolium.jpg|thumb|left|150px|''Aster tripolium''  Credit Jan van der Straaten www.freenatureimages.eu]]
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[[File:CochleariaDanica.jpg|thumb|left|150px|''Cochlearia danica''  Credit Ed Stikvoort www.freenatureimages.eu]]
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[[File:LimoniumVulgare.jpg|thumb|left|150px|''Limonium vulgare''  Credit Rutger Barendse  www.freenatureimages.eu]]
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[[File:HalimionePortulacoides.jpg|thumb|left|150px|''Halimione portulacoides''  Credit Jan van der Straaten  www.freenatureimages.eu]]
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[[File:BostrychiaScorpiodes.jpg|thumb|left|150px|''Bostrychia scorpiodes''  Credit Andre Rio.  www.Marevita.org]]
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After this stage, filamentous [[algae]] optimize the fixation of sediments. These [[algae]] are mostly blue-green algae, Cyanophyta and Chlorophyta. Small gastropods can feed and develop in huge quantities on it. Locally, the filamentous alga ''Vaucheria'' can form banquettes or elevations. Brown algae are loosely associated with this stage.
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==Adaptations==
  
A next stage is the germination of species such as ''Salicornia''. The seeds germinate after some desalination of the soil by rain. Between and around the glassworts takes extra sediment accumulation place. This results in elevating the substrate and makes it more stable. Other species such as ''Spartina maritime'' and ''Spartina townsendii'' compete for the same place. ''S. maritima'' is an indigenous species of continental Europe and ''S. townsendii'' is imported from the British Islands. ''Juncus maritimus'' is another species that can occur in salt marshes.  
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Plants and animals living in low salt marshes must have adaptations to deal with the harsh physical stressors found in this intertidal habitat, including high salt concentrations, intense heat, and low oxygen in waterlogged soils. Some typical adaptations are discussed below.
  
In Europe, other plants can occur. These herbs are Common Saltmarsh-grass (''Puccinellia maritime''), Sea Plantain (''Plantago maritime''), Sea Arrow-grass (''Triglochin maritinum''), Sea Aster (''Aster tripolium''), English Scurvy-grass (''Cochlearia anglica''), Common Sea-lavender (''Limonium vulgare''), Sea Purslane (''Halimione portulacoides''), the red alga ''Bostrychia scorpioides'' and ''Catenella caespitosa''. <ref>Eric Coppejans – Course Biodiversity of aquatic food webs: from algae to marine mammals UGent</ref>
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The saline environment causes waterstress. Plants have to take up water against the [[Osmosis|osmotic pressure]]. To overcome the negative osmotic pressure, they generate a negative hydrostatic pressure (by transpiration processes). They have thin, fleshy leaves and are sensitive to extra stress such as pollution. Anatomically, the plants are adapted through strong lignification, a well-developed epidermis and succulent leaves and stems. Evaporation can be limited by thin leaves with scale-like hairs. Physiologically, plants are adapted by accumulating salt in their tissues. In this way, normal [[osmosis]] is possible. Other plants have salt gland cells on the lower surface of the leaves and excrete the salt from its tissue.  
  
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Salt marsh plants have to deal with an anoxic environment. The tissue of the plants requires oxygen for [[respiration]]. Gas diffusion between sediment particles only occurs in soils that are not waterlogged. Even when the surface water is saturated with oxygen, its concentration in the soil is too low because of the slow oxygen diffusion. Many salt marsh plants deal with low soil oxygen levels by shunting oxygen down to their roots through straw-like vascular tissue called aerenchyma. Roots are superficial systems because of the anoxic sediments. They consist of perennial thick roots with a corky layer and without root hairs. To fix the substrate, short-lived, thin and highly branched roots with numerous root hairs are developed to absorb nutrients.
  
<gallery>
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Nitrogen limitation can also play a role in the development of salt marsh vegetation, even though nitrogen levels can be very high. The reason is that concentrations of sulfide and sodium ions are often high too and interfere with nitrogen uptake by plants<ref name=S14/>.
Image:Biofilm.jpg|Biofilm of unicellular algae <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>
 
Image:Filamentous algae.JPG|Fixation of the sediment by blue-green and green algae <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref> 
 
Image:Salicornia.JPG|''Salicornia perennis'' <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>
 
Image:Spartina.JPG|''Spartina townsendii '' <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>
 
Image:Trigochlin.JPG|''Triglochin maritinum '' <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>
 
Image:Aster.JPG|''Aster tripolium '' <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>
 
Image:Limonium vulgare.JPG|''Limonium vulgare '' <ref name="multiple">Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134</ref>
 
</gallery>
 
  
  
==Functioning and adaptations==
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==Functions==
  
Salt marshes have several functions and adaptations to a life in an intertidal ecosystem. They need to conquer some problems to be resistant to the environment. Therefore, it is important to have some adaptations to survive.
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Salt marshes have a whole range of functions. They play an important role as sediment trap; in this way they help stabilizing the coastline. Salt marshes improve the water quality by filtering water and retaining excess nutrients, toxic chemicals and disease-causing organisms. They remove nitrates and phosphates from rivers and streams which receive waste water effluents. Another function is water supply regulation by recharge and discharge of groundwater. Salt marshes are an important [[habitat]], offering nursery grounds and shelter for larvae and other small organisms and providing food and nesting areas for wading birds and other organisms.  
The first problem is that the plants are freshwater plants. This causes '''waterstress'''. For this reason, they have to take up water against the osmotic pressure. To overcome the negative osmotic pressure, they generate a negative hydrostatic pressure (by transpiration processes). They have thin, fleshy leaves and are sensitive to extra stress such as pollution. Anatomically, the plants are adapted through strong '''lignification''', a well-developed '''epidermis''' and '''succulent leaves and stems'''. Evaporation can be limited by thin leaves with scale-like '''hairs'''.
 
Physiologically, plants are adapted by accumulating salt in their tissues. In this way, normal [[osmosis]] is possible. Other plants have '''salt gland''' cells on the lower surface of the leaves and excrete the salt from its tissue.
 
A second problem is the '''anoxic environment'''. The underground in which they root is saturated with water. The tissue of the plants requires oxygen for respiration. Gas diffusion between gas particles can only supply this need in soils that are not waterlogged. Even when the water is saturated with oxygen, its concentration is too low and the diffusion in water is very slow. This is solved by '''aerenchyma''', a tissue that can provide air to the submerged parts of the plants. Roots are superficial systems because of the anoxic sediments. These systems are composed of perennial thick roots with a corky layer and without root hairs. To fixate the substrate, shortliving thin and strongly branched roots with numerous root hairs are developed so they can take up nutrients.
 
Salt marshes have a whole range of functions. It plays an important role as a '''sediment trap'''. In this way, it regulates the water quality and helps '''stabilizing''' the coastlines. Salt marshes function as '''filtering systems''' and retain sediments, excess nutrients, toxic chemicals and disease-causing organisms. They remove nitrates and phosphates from rivers and streams which receive waste water effluents. Another function is the recharge and discharge of groundwater attributing to the '''water supply'''.  
 
Salt marshes function also as important [[habitat]], '''nursery''' grounds for larvae and small organisms, '''shelter''', providing '''food''' and a '''nesting''' ground for wading birds and other organisms. <ref>http://wwwutmsi.zo.utexas.edu/staff/dunton/EcoDynamics/MEDLec10.pdf</ref>
 
  
  
 
==Fauna==
 
==Fauna==
  
Small mammals, small fishes, birds, insects, spiders, and marine invertebrates are found in salt marshes. Marine '''invertebrates''' include amphipods, isopods, anemones, shrimps, crabs, , turtles, mollusks and gastropods. '''Fishes''' such as sticklebacks, silversides, eels and flounders are found in the waters of the salt marshes. The salt marshes are important breeding, feeding and overwintering grounds for '''waterfowl'''. These waterfowls consist of ducks, herons, Sharptailed Sparrows, Eurasian Oystercatchers, Reed Bunting,…
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Salt marshes are home to many small mammals, small fishes, birds, insects, spiders and marine invertebrates. Marine invertebrates include crustaceans such as [https://en.wikipedia.org/wiki/Amphipoda amphipods] and [https://en.wikipedia.org/wiki/Isopoda isopods], [https://en.wikipedia.org/wiki/Sea_anemone sea anemones], shrimps, crabs, turtles, mollusks and snails. Fishes such as sticklebacks, silversides, eels and flounders are found in the waters of the salt marshes. The [[benthic]] community consists of mollusks, polychaeta and oligochaeta. Salt marshes are important breeding, feeding and overwintering grounds for waterfowl. These waterfowl consist of ducks, herons, sharptailed sparrows, Eurasian oystercatchers, reed bunting, etc. In Saudi Arabia, salt marshes are grazing places for wild dromedaries.  
The '''benthic''' community consists of mollusks, polychaeta and oligochaeta.
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The coastal freshwater marshes are species poor. The organisms that you can find here are water boatmen, flies, mosquitos and snails. Further there are mollusks, ducks, geese, muskrats, raccoons, minks and other small mammals. For some species, a seasonal appearance can be seen.
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Although the local diversity of plants and animals found in salt marshes is comparatively low, the abundance of organisms that do occur in marshes is very high. The abundance per square meter of one species of fiddler crab or snail can reach 100–400 individuals, at times over 1000, and over larger spatial scales the density of one species of non-insect invertebrate (mussels, crabs and snails) can often reach 50,000,000 per square kilometer<ref name=S14/>.
In Saudi Arabia, salt marshes are grazing places for wild dromedaries. <ref>http://museum.gov.ns.ca/mnh/nature/nhns/h2/h2-5.htm</ref>
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Freshwater tidal marshes have a high biodiversity but do not harbor many endemic species<ref> Barendregt, A., Whigham, D.F., Meire, P., Baldwin, A.H., Van Damme, S. 2006. Wetlands in the Tidal Freshwater Zone. In: Bobbink R., Beltman B., Verhoeven J.T.A., Whigham D.F. (eds) Wetlands: Functioning, Biodiversity Conservation, and Restoration. Ecological Studies (Analysis and Synthesis), vol 191. Springer, Berlin, Heidelberg.</ref>. Organisms typical of freshwater tidal marshes are boatmen, flies, mosquitoes and snails. There are also mollusks, ducks, geese, muskrats, raccoons, mink and other small mammals. Some species are seasonal visitors.
  
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Image:Haematopus ostralegus M. Decleer.jpg|Eurasian oystercatcher <ref>http://www.marbef.com - Decleer M.</ref>
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Image:water boatman E.S.Ross.jpg|Water boatman <ref>Ross E.S.</ref>
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Image:Mink.jpg|European mink <ref>http://en.wikipedia.org/wiki/Mink</ref>
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</gallery>
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[[File:Haematopus ostralegus M. Decleer.jpg|thumb|left|300px|Eurasian oystercatcher. Photo credit M. Decleer]]
 +
| valign="top"|
 +
[[File:water boatman E.S.Ross.jpg|thumb|left|200px|Water boatman. Photo credit E.S. Ross]]
 +
| valign="top"|
 +
[[File:Mink.jpg|thumb|left|200px|European mink <ref>http://en.wikipedia.org/wiki/Mink</ref>]]
 +
|}
  
  
 
==Threats==
 
==Threats==
  
The total number and area of salt marshes is declining since a long time. The main reason for severe damage is land '''reclamation'''. This is completely eliminating the highly specialized ecosystems. Areas where the level is high enough and the area big enough can become embanked. Areas outside the reclaimed zones can produce new marshes. This is because of the continuously sedimentation that allows growth of new plants. <ref>Council of Europe – Dijkema K.S. et al. 1984. Salt marshes in Europe. Nature and environment series No.30 p. 178</ref>
+
The total number and area of salt marshes has been declining for many years. The main cause is embanking, which removes the habitat from tidal inundation. This normally occurs in areas where the soil level is high enough and the area large enough for embankment to take place. The salt marsh is destroyed when converted to other uses, notably conversion to intensive agriculture.
  
'''Other threats''' are:
+
In south east England and in France a special type of enclosed saltmarshes exist that are protected as a semi-natural habitat. Once enclosed, the saltmarsh still has salt water inlets with creeks and other features retained with little interference. Dispersed grazing or cropping for hay are often the only uses and with traditional management it develops into a wildlife habitat of some significance. The term [[Coastal grazing marsh]] (in France: prairie subhalophile) is used to describe this habitat.
  
* Over-grazing
+
Reclamation for harbour development and other infrastructures completely destroys the habitat and with it any opportunities for restoration.  Areas outside the reclaimed zones still can produce new marshes if there is sufficient supply of new sediment and conditions suitable for growth of new plants. <ref>Council of Europe – Dijkema K.S. et al. 1984. Salt marshes in Europe. Nature and environment series No.30 p. 178</ref> However, climate change and the associated sea level rise are diminishing the opportunities for salt marsh development and the "[[coastal squeeze]]" process takes place in many areas, especially around the southern North Sea <ref>Doody, J.P. (2004) 'Coastal squeeze' - an historical perspective. ''Journal of Coastal Conservation'', 10/1-2, 129-138.</ref>.
* Embankment
+
 
* Excessive agricultural use
+
Other threats include:
 +
 
 +
* Over-grazing (especially farm animals, but also grazing by wild geese, crabs and snails)
 +
* Eutrophication by agricultural effluents
 
* Urbanization
 
* Urbanization
 
* Recreation
 
* Recreation
 
* [[Coast erosion|Coastal erosion]]
 
* [[Coast erosion|Coastal erosion]]
* Pollution and industrial waste water  
+
* Industrial pollution and waste water  
* Dominance of ''Spartina anglica'' and ''Erytrigia'' (in eutrophic salt marshes)
+
* Altered hydrologic regimes
 +
* Species invasions (especially invasion of ''Spartina anglica'' and ''Erytrigia'' in eutrophic salt marshes)
 +
* Climate change (sela level rise and increased temperatures and frequency of intense drought).
 +
 
 +
 
 +
==Case-study: Land van Saeftinghe<ref>https://www.saeftinghe.eu/nl/</ref>==
 +
 
 +
The [[Tide|tidal]] area ‘Drowned land of Saeftinghe’ (Verdronken land van Saeftinghe) is located near the border between the Netherlands and Belgium, a few kilometers downstream Antwerp in the estuary of the Western Scheldt. It is an official nature reserve since 1976. Because of this legal protection, permits are compulsary for every intervention and strict entrance restrictions are applied.
 +
The land is situated at the transition zone of the Western Scheldt where the river Scheldt meets the saline North Sea water. Before the storm surge of 1570, the land was a fertile polder. The area has a surface of 3,484 hectares. Almost 70 % of the area is overgrown by salt marsh vegetation. The remaining 30 % consists of [[Tidal flats from space|mud flats]], sandbanks and a network of channels. Each [[tide]], the brackish water overflows a large part of the area. The unique vegetation is fully adapted to this. The area is an ideal breeding, rest and wintering place for huge quantities of birds. Since 1996 it is a special protected area for birds (1979 Directive 79/409/EEC on the conservation of wild birds) of international importance.
 +
 
 +
 
 +
{| border="0"
 +
|-
 +
| valign="top"|
 +
[[File:Saefringhe NIOO-CEME.jpg|thumb|left|400px|Land of Saeftinghe - Belgium <ref>http://www.marbef.org</ref>]]
 +
| valign="top"|
 +
[[File:gebiedbes-afb-1.gif|thumb|left|400px|Western Scheldt estuary, with the Land of Saeftinghe in green.]]
 +
|}
  
  
==Case-study: Land van Saeftinghe==
+
In the past, a few dikes were created to promote the silting up. The northern dike connects a few hillocks (artificial elevations of earth) with the dike. These dikes are still recognizable and are used as wandering path. The hillocks were used by shepherds when the [[tide]] became too high. 
 +
The flora consists of approximately 50 wild plant species. [[Algae]] are not abundant in Saeftinghe because there is too little light that penetrates in the water. Organic matter and a lot of silt make the water turbid. Higher plants are more important in this area. One of the most common plants is pickle weed (''Salicornia''), together with other salt marsh plants such as English scurvy-grass (''Cochlearia anglica'') and common sea-lavender (''Limonium vulgare'').
  
The [[Tide|tidal]] area ‘Drowned land of Saeftinghe’ (Verdronken land van Saeftinghe) is located at the eastern boundary between the Netherlands and Belgium, a few kilometers downstream Antwerp in the estuary of the Scheldt. It is an official nature reserve since 1976. Because of this legal protection, permits are obligatory for every intervention and strict entrance restrictions are applied.
 
The land is a crosspoint where the river the Scheldt meets the salty water of the North Sea in the [[Estuaries and tidal rivers|estuary]] known as the Western Scheldt. In the past, the land was a very fertile polder. The area has a surface of 3484 hectares. Almost 70 % of the area is overgrown by specific plants of the salt marsh.  The residual 30 % consists of [[Tidal flats from space|mud flats]], sandbanks and a network of channels. Each [[tide]], the brackish water overflows a large part of the area. The plants there are totally adapted to this and are very unique. For huge quantities of birds, this area is an ideal breeding, rest and wintering place. This makes the area of international importance. Since 1996 it is a special protected area for birds (1979 Directive 79/409/EEC on the conservation of wild birds).
 
  
 +
==Related articles==
 +
:[[Dynamics, threats and management of salt marshes]]
 +
:[[Spatial and temporal variability of salt marshes]]
 +
:[[Biogeomorphology of coastal systems]]
 +
:[[Natural shore protecting barriers]]
  
[[image:gebiedbes-afb-1.gif|center|thumb|350px|caption|Area description of the Western Scheldt, with the Land of Saeftinghe in green <ref>http://www.hetzeeuwselandschap.nl/saeftinghe/algemeen/index.php</ref>]]
 
  
 +
==Salt marsh restoration guide==
  
In the past, a few dikes were created to promote the silting up. The northern dike connects a few stands with the dike. These dikes are still recognizable and are used as wandering path. The stands were used as hills where shepherds retreated when the [[tide]] became too high. 
+
For information of the management and restoration of saltmarshes in the UK see [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/290974/scho0307bmkh-e-e.pdf DEFRA Saltmarsh management manual]
The flora exists of approximately 50 wild plant species. [[Algae]] are not abundant in Saeftinghe because there is too little light that penetrates in the water. Organic matter and a lot of silt make the water turbid. Higher plants are more important in this area. One of the most common plants is pickle weed (''Salicornia''). But other salt marsh plants such as English Scurvy-grass (''Cochlearia anglica'') and Common Sea-lavender (''Limonium vulgare''). <ref>http://www.hetzeeuwselandschap.nl/saeftinghe/index.php</ref>
 
  
  
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|AuthorFullName=TÖPKE, Katrien
 
|AuthorFullName=TÖPKE, Katrien
 
|AuthorName=Ktopke}}
 
|AuthorName=Ktopke}}
  
[[Category:Marine habitats and ecosystems]]
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[[Category:Coastal and marine habitats]]
[[Category:Typology of coastal and marine areas]]
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[[Category:Coastal and marine ecosystems]]
[[Category:Location of coastal and marine areas]]
 
[[Category:Theme 7]]
 

Revision as of 21:46, 14 March 2021

This article describes the habitat of salt marshes. It gives an introduction to the characteristics, distribution, evolution, zonation, succession, biota, threats, functioning and adaptations of the organisms that live in salt marshes.

In 2008 the European Union commissioned a series of Habitat Management Models for several of the more important communities. Included is a model for habitat 1330 "Atlantic salt meadows" (Glauco-Puccinellietalia maritimae).

Visit the European Union web site at [1] to download a copy of the Habitat Management Model for the above community.


Introduction

Salt marshes are defined as natural or semi-natural terrestrial halophytic ecosystems that occur in the intertidal zone between the land and the sea and that are covered by salty or brackish water for at least part of the time. They can be considered, in some way, as the analogue of mangroves in temperate and arctic regions. The dominant flora is composed of halophytic plants such as grasses, shrubs and herbs. The flora is locally rather species poor, but the global species diversity is high, with over 500 salt marsh plant species known[1]. Salt marshes are normally associated with mud flats but also occur on sand flats. These mud flats are sometimes dominated by algae and covered with algal mats. They are periodically flooded by the tide, the height of which can vary from several centimetres in enclosed seas (such as the Baltic Sea) to several metres in open seas along the ocean margins. A network of meandering tidal creeks ensures the drainage of seawater. Through these channels, sediments, detritus, dissolved nutrients, plankton and small fishes are flushed in and out the salt marshes.


Distribution

Distribution of salt marshes (green), wetlands (orange and yellow) and mangroves (pink).

Salt marshes are ubiquitous in estuarine systems in temperate zones all over the world. They also occur in deltas and rias but seldom on open coasts, because the development is inhibited by wave action. Although sediment is a prerequisite for their growth in height and width, salt marsh communities can occur in areas with limited or no sediment supply. Examples include seawater-drenched cliffs and slopes on exposed coasts, at the head of sea lochs and rocky beaches (Doody 2008[2]). Salt marshes can be found from the Arctic region, over Europe, Africa, America, Asia to the coast of Australia. The most extensive development of salt marshes occurs in estuaries with a moderate climate, large tidal range, abundant fine-grained sediments and sheltered locations where particles can settle out of the water column.

Evolution

Salt marshes evolve over time from young marshes to old marshes. The natural young marshes in eastern USA are vegetated for the largest part with low marsh cordgrass Spartina alterniflora. Nutrients are transported by tidal currents through the tidal channels. This allows the grasses to grow thickly and profuse, so weakening the effect of waves and tidal currents and increasing the deposition rate of mud. Erosion is reduced by the roots and rhizomes of the plants. At the time that the marsh surface builds up above the high water level, high marsh species invade, outcompete and replace the low marsh plants. The most stress-tolerant plant species occupy the lower reaches of the marshes while competitive dominants occupy the upper elevations that are less stressful[1]. When the extent of the low and high marshes is about equal, the ecosystem is in a mature stage of development. The ongoing deposition of mud converts most of the low marshes into high marshes. Little water flows through the tidal channels of these elevated 'old marshes'. Deposition of sand and mud on these high marshes convert them into dry land that is disconnected from ocean influences[3]. Lateral channel migration and wave attack at the base of marsh cliffs are the main mechanisms for erosion of mature salt marshes and their subsequent rejuvenation cycle[4][5], see also Dynamics, threats and management of salt marshes and French case studies: Upper tidal flat evolution in the bay of Mont-Saint-Michel (NW France).


Requirements for development

The requirements for development of salt marshes are:

  • They need fine-grained sediments.
  • There may be no strong waves or tidal currents.
  • They need salty conditions to grow. They are halotolerant and have adaptations to these conditions.
  • They need a temperate or cool temperature. Incidental freezing temperatures are not damaging the plants.
  • They need a wide tidal range. This is important because it limits the erosion, makes deposition of sediments possible and causes a well-marked zonation.


Zonation

Zonation of salt marshes. Image credit: USGS

Based on the topography and characteristic plant assemblages, salt marshes are classified as low, medium and high marshes. This classification is related to the number of tidal submergences per year (Adam 1990[6]). The 'low marshes' extend from the mean low water neap tide to the mean high water spring tide. The low marshes are drained by tidal creeks that convey flood and ebb flow; ebb flow generally dominates because flood water also enters the marsh directly from the main channels. The 'high marshes' extend from the mean high water level to the highest springtide level. Flooded only by the highest tides and during storms, they are more like a terrestrial than a true marine environment. The plant community is more diverse than on the low marshes. Typical high marsh species are cordgrass Spartina patens, spike grass Distichlis spicata and species such as saltwort Salsola and seablite Suaeda. Distribution, density and activity of invertebrates mainly depend on protection, food and frequency of tidal flooding. [3]


Spartina patens Credit T. Forney www.pest.ceris.purdue.edu
Salsola kali Credit Ed Stikvoort www.freenatureimages.eu
Suaeda maritima Credit Ed Stikvoort www.freenatureimages.eu


Succession

Succession is the successive development in time of different vegetation types at one place. It is a complex process; the factors determining zonation and succession in salt marshes are discussed more in detail in Adam (1990[6], pages 49-57), Gray (1992[7]) and Packham & Willis (1997, pages 107-114 [8]).

Biofilm of unicellular algae [9]
Fixation of the sediment by blue-green and green algae [9]

The mudflat colonization starts with unicellular algae such as diatoms sticking the sand together by production of mucus. This causes a brownish biofilm on the substrate.

After this stage, filamentous algae contribute to the further fixation of sediments. These algae are mostly blue-green algae, Cyanophyta and Chlorophyta. Small gastropods can feed and develop in huge quantities on it. Locally, the filamentous alga Vaucheria can form banquettes or elevations. Brown algae can be associated with this stage.

A next stage is the germination of species such as the glasswort Salicornia. The seeds germinate after partial desalination of the soil by rain. Sedimentation between and around the glassworts contributes to elevating and stabilizing the substrate. Other species such as Spartina maritima and Spartina anglica compete for the same place. S. maritima is an indigenous species of continental Europe and S. anglica is imported from the British Islands. The hybridisation and invasion of "Spartina" spp is a worldwide phenomenon[10].


Salicorna europaea Credit Bart Vastenhouw, www.freenatureimages.eu
Spartina maritima Credit Ed Stikvoort www.freenatureimages.eu
Spartina anglica Credit Ed Stikvoort www.freenatureimages.eu


In Europe, other plants also occur. These are the herbs common saltmarsh-grass (Puccinellia maritima), sea plantain (Plantago maritima), sea arrow-grass (Triglochin maritinum), sea aster (Aster tripolium), danish scurvy-grass (Cochlearia danica), common sea-lavender (Limonium vulgare), sea purslane (Halimione portulacoides), the red alga Bostrychia scorpioides and Catenella caespitosa. [11]. Juncus maritimus is another species that can occur in salt marshes.

Initial plant colonizers play an important role in the recovery of salt marsh vegetation from disturbance events. They provide shading of the substrate of bare areas and reduce salt accumulation in the soils and thereby facilitate colonization by many other plant species[1].


Puccinellia maritima Credit Peter Meininger www.freenatureimages.eu
Plantago maritima Credit Jeroen Willemsen www.freenatureimages.eu
Triglochin maritima Credit Hans Boll www.freenatureimages.eu
Aster tripolium Credit Jan van der Straaten www.freenatureimages.eu
Cochlearia danica Credit Ed Stikvoort www.freenatureimages.eu
Limonium vulgare Credit Rutger Barendse www.freenatureimages.eu
Halimione portulacoides Credit Jan van der Straaten www.freenatureimages.eu
Bostrychia scorpiodes Credit Andre Rio. www.Marevita.org


Adaptations

Plants and animals living in low salt marshes must have adaptations to deal with the harsh physical stressors found in this intertidal habitat, including high salt concentrations, intense heat, and low oxygen in waterlogged soils. Some typical adaptations are discussed below.

The saline environment causes waterstress. Plants have to take up water against the osmotic pressure. To overcome the negative osmotic pressure, they generate a negative hydrostatic pressure (by transpiration processes). They have thin, fleshy leaves and are sensitive to extra stress such as pollution. Anatomically, the plants are adapted through strong lignification, a well-developed epidermis and succulent leaves and stems. Evaporation can be limited by thin leaves with scale-like hairs. Physiologically, plants are adapted by accumulating salt in their tissues. In this way, normal osmosis is possible. Other plants have salt gland cells on the lower surface of the leaves and excrete the salt from its tissue.

Salt marsh plants have to deal with an anoxic environment. The tissue of the plants requires oxygen for respiration. Gas diffusion between sediment particles only occurs in soils that are not waterlogged. Even when the surface water is saturated with oxygen, its concentration in the soil is too low because of the slow oxygen diffusion. Many salt marsh plants deal with low soil oxygen levels by shunting oxygen down to their roots through straw-like vascular tissue called aerenchyma. Roots are superficial systems because of the anoxic sediments. They consist of perennial thick roots with a corky layer and without root hairs. To fix the substrate, short-lived, thin and highly branched roots with numerous root hairs are developed to absorb nutrients.

Nitrogen limitation can also play a role in the development of salt marsh vegetation, even though nitrogen levels can be very high. The reason is that concentrations of sulfide and sodium ions are often high too and interfere with nitrogen uptake by plants[1].


Functions

Salt marshes have a whole range of functions. They play an important role as sediment trap; in this way they help stabilizing the coastline. Salt marshes improve the water quality by filtering water and retaining excess nutrients, toxic chemicals and disease-causing organisms. They remove nitrates and phosphates from rivers and streams which receive waste water effluents. Another function is water supply regulation by recharge and discharge of groundwater. Salt marshes are an important habitat, offering nursery grounds and shelter for larvae and other small organisms and providing food and nesting areas for wading birds and other organisms.


Fauna

Salt marshes are home to many small mammals, small fishes, birds, insects, spiders and marine invertebrates. Marine invertebrates include crustaceans such as amphipods and isopods, sea anemones, shrimps, crabs, turtles, mollusks and snails. Fishes such as sticklebacks, silversides, eels and flounders are found in the waters of the salt marshes. The benthic community consists of mollusks, polychaeta and oligochaeta. Salt marshes are important breeding, feeding and overwintering grounds for waterfowl. These waterfowl consist of ducks, herons, sharptailed sparrows, Eurasian oystercatchers, reed bunting, etc. In Saudi Arabia, salt marshes are grazing places for wild dromedaries.

Although the local diversity of plants and animals found in salt marshes is comparatively low, the abundance of organisms that do occur in marshes is very high. The abundance per square meter of one species of fiddler crab or snail can reach 100–400 individuals, at times over 1000, and over larger spatial scales the density of one species of non-insect invertebrate (mussels, crabs and snails) can often reach 50,000,000 per square kilometer[1].


Freshwater tidal marshes have a high biodiversity but do not harbor many endemic species[12]. Organisms typical of freshwater tidal marshes are boatmen, flies, mosquitoes and snails. There are also mollusks, ducks, geese, muskrats, raccoons, mink and other small mammals. Some species are seasonal visitors.


Eurasian oystercatcher. Photo credit M. Decleer
Water boatman. Photo credit E.S. Ross
European mink [13]


Threats

The total number and area of salt marshes has been declining for many years. The main cause is embanking, which removes the habitat from tidal inundation. This normally occurs in areas where the soil level is high enough and the area large enough for embankment to take place. The salt marsh is destroyed when converted to other uses, notably conversion to intensive agriculture.

In south east England and in France a special type of enclosed saltmarshes exist that are protected as a semi-natural habitat. Once enclosed, the saltmarsh still has salt water inlets with creeks and other features retained with little interference. Dispersed grazing or cropping for hay are often the only uses and with traditional management it develops into a wildlife habitat of some significance. The term Coastal grazing marsh (in France: prairie subhalophile) is used to describe this habitat.

Reclamation for harbour development and other infrastructures completely destroys the habitat and with it any opportunities for restoration. Areas outside the reclaimed zones still can produce new marshes if there is sufficient supply of new sediment and conditions suitable for growth of new plants. [14] However, climate change and the associated sea level rise are diminishing the opportunities for salt marsh development and the "coastal squeeze" process takes place in many areas, especially around the southern North Sea [15].

Other threats include:

  • Over-grazing (especially farm animals, but also grazing by wild geese, crabs and snails)
  • Eutrophication by agricultural effluents
  • Urbanization
  • Recreation
  • Coastal erosion
  • Industrial pollution and waste water
  • Altered hydrologic regimes
  • Species invasions (especially invasion of Spartina anglica and Erytrigia in eutrophic salt marshes)
  • Climate change (sela level rise and increased temperatures and frequency of intense drought).


Case-study: Land van Saeftinghe[16]

The tidal area ‘Drowned land of Saeftinghe’ (Verdronken land van Saeftinghe) is located near the border between the Netherlands and Belgium, a few kilometers downstream Antwerp in the estuary of the Western Scheldt. It is an official nature reserve since 1976. Because of this legal protection, permits are compulsary for every intervention and strict entrance restrictions are applied. The land is situated at the transition zone of the Western Scheldt where the river Scheldt meets the saline North Sea water. Before the storm surge of 1570, the land was a fertile polder. The area has a surface of 3,484 hectares. Almost 70 % of the area is overgrown by salt marsh vegetation. The remaining 30 % consists of mud flats, sandbanks and a network of channels. Each tide, the brackish water overflows a large part of the area. The unique vegetation is fully adapted to this. The area is an ideal breeding, rest and wintering place for huge quantities of birds. Since 1996 it is a special protected area for birds (1979 Directive 79/409/EEC on the conservation of wild birds) of international importance.


Land of Saeftinghe - Belgium [17]
Western Scheldt estuary, with the Land of Saeftinghe in green.


In the past, a few dikes were created to promote the silting up. The northern dike connects a few hillocks (artificial elevations of earth) with the dike. These dikes are still recognizable and are used as wandering path. The hillocks were used by shepherds when the tide became too high. The flora consists of approximately 50 wild plant species. Algae are not abundant in Saeftinghe because there is too little light that penetrates in the water. Organic matter and a lot of silt make the water turbid. Higher plants are more important in this area. One of the most common plants is pickle weed (Salicornia), together with other salt marsh plants such as English scurvy-grass (Cochlearia anglica) and common sea-lavender (Limonium vulgare).


Related articles

Dynamics, threats and management of salt marshes
Spatial and temporal variability of salt marshes
Biogeomorphology of coastal systems
Natural shore protecting barriers


Salt marsh restoration guide

For information of the management and restoration of saltmarshes in the UK see DEFRA Saltmarsh management manual


References

  1. 1.0 1.1 1.2 1.3 1.4 Silliman, B.R. 2014. Salt marshes. Current Biology 24(9) R348
  2. Doody, J.P. 2008. Saltmarsh Conservation, Management and Restoration. Coastal Systems and Continental Margins, Volume 12, Springer, 217 pp.
  3. 3.0 3.1 Pinet P.R. 1998. Invitation to Oceanography. Jones and Barlett Publishers. p. 508
  4. Levoy, F., Anthony, E.J., Dronkers, J., Monfort, O. and Montreuil, A-L. 2019. Short-term to Decadal-scale Sand Flat Morphodynamics and Sediment Balance of a Megatidal Bay: Insight from Multiple LiDAR Datasets. Journal of Coastal Research SI 88: 61–76
  5. Mariotti, G. and Fagherazzi, S. 2013. Critical width of tidal flats triggers marsh collapse in the absence of sea-level rise, Proc. Natl. Acad. Sci. 110(14): 5353–5356
  6. 6.0 6.1 Adam, P., 1990. Saltmarsh Ecology. Cambridge University Press, Cambridge
  7. Gray, A.J. 1992. Saltmarsh plant ecology. In: Saltmarshes: morphodynamics, conservation and engineering significance, J.R.L., Allen, & K., Pye, eds., 63-79. Cambridge University Press, Cambridge.
  8. Packham, J.R. & Willis, A.J., 1997. Ecology of dunes, saltmarsh and shingle. Chapman & Hall, London.
  9. 9.0 9.1 Credit Eric Coppejans - http://www.vliz.be/imis/imis.php?module=person&persid=134
  10. Strong, D.R. and Ayres, D.R. 2013. Ecological and Evolutionary Misadventures of Spartina. Annu. Rev. Ecol. Evol. Syst. 44: 23.1–23.22
  11. Eric Coppejans – Course Biodiversity of aquatic food webs: from algae to marine mammals UGent
  12. Barendregt, A., Whigham, D.F., Meire, P., Baldwin, A.H., Van Damme, S. 2006. Wetlands in the Tidal Freshwater Zone. In: Bobbink R., Beltman B., Verhoeven J.T.A., Whigham D.F. (eds) Wetlands: Functioning, Biodiversity Conservation, and Restoration. Ecological Studies (Analysis and Synthesis), vol 191. Springer, Berlin, Heidelberg.
  13. http://en.wikipedia.org/wiki/Mink
  14. Council of Europe – Dijkema K.S. et al. 1984. Salt marshes in Europe. Nature and environment series No.30 p. 178
  15. Doody, J.P. (2004) 'Coastal squeeze' - an historical perspective. Journal of Coastal Conservation, 10/1-2, 129-138.
  16. https://www.saeftinghe.eu/nl/
  17. http://www.marbef.org


The main author of this article is TÖPKE, Katrien
Please note that others may also have edited the contents of this article.

Citation: TÖPKE, Katrien (2021): Salt marshes. Available from http://www.coastalwiki.org/wiki/Salt_marshes [accessed on 28-03-2024]