Difference between revisions of "Salt marshes"

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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 tidal flooding through the [[Tides|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 '''young marshes''' consist for the largest part of low marsh cordgrass ''Spartina alterniflora''. [[Nutrients]] are transported by 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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* They need '''fine-grained sediments'''.  
 
* They need '''fine-grained sediments'''.  
 
* There may be '''no strong waves or tidal currents'''.  
 
* There may be '''no strong waves or tidal currents'''.  
* They need salty conditions to grow. They are '''halotolerant''' and have
+
* They need salty conditions to grow. They are '''halotolerant''' and have adaptations to these conditions.  
adaptations to these conditions.  
 
 
* They need a temperate or cool '''temperature'''. Freezing temperatures can occur, but are not damaging the plants.
 
* They need a temperate or cool '''temperature'''. Freezing temperatures can occur, but 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.
 
* 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.

Revision as of 11:25, 15 July 2008

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.


Introduction

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 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 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.


Land of Saeftinghe - Belgium [1]


Distribution

Salt marshes are widely distributed in estuarine systems around the world. They have a range from the Arctic region over Europe, Africa, America, Asia to the coast of Australia. The most extensive development of these salt marshes occurs where rainfall is abundant, sediments are fine-grained and the climate is moderate.


Distribution of salt marshes (green), wetlands (orange and yellow) and mangroves (pink) [2]


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 tidal flooding through the 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. [3]


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. Freezing temperatures can occur, but 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.




References

  1. http://www.marbef.org
  2. http://cache.eb.com/eb/image?id=6576&rendTypeId=4
  3. Pinet P.R. 1998.Invitation to Oceanography. Jones and Barlett Publishers. p. 508


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 (2008): Salt marshes. Available from http://www.coastalwiki.org/wiki/Salt_marshes [accessed on 22-02-2020]