Salt Marsh Case Study – Keyhaven Marshes
Salt marshes are a coastal ecosystem that is damp area of vegetation associated with shallow saline waters near the coast. The salt marsh I will be looking at is Keyhaven marshes which have formed behind Hurst Castle Spit in the Western Solent in southern Hampshire. Salt marshes form as a result of a combination of physical factors. Salt marshes need protection from the open sea as they need a low energy environment where accretion can occur and erosion is reduced. The Keyhaven marshes are protected by the Hurst Castle Spit, a finger of land extending from the coast and created by easterly long shore drift carrying and depositing shingle. Salt marshes also need an area with little wave action as fine particles can’t fall out of suspension if there aren’t calm conditions. It needs a source of both mud and sediment. Mud is provided to Keyhaven salt marsh by the tree main creeks in the area as well as the sea. A large amount of sediment is needed to allow deposition. The last main condition needed to encourage the development of salt marshes is a stable climate. This allows plants to grow on the salt marsh as plants need a good climate with sunlight and water to hold the salt marsh in place. Salt marsh succession is where the salt marsh increases in height and breadth, and allows plants to grow on it. Coastal accretion causes the salt marsh to increase in height as more material is added to it. The height of the shore increases so that the coast is only emersed several times a year which allow pioneer plants such as glasswort and cord grass are able to colonise the salt marsh. Pioneer species bind together mud and make the marsh more stable. More plants are attracted to the area but there is still a lot of bare ground. As the marsh continues to increase in height it experiences less submergence, causing plants to fight for space. Competition will eventually stop, leaving the strongest species behind. The salt marsh will...
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