Saltmarsh
From Wikipedia, the free encyclopedia
A salt marsh is a type of marsh found in the intertidal transition between land and ocean. They are dominated by halophytic herbaceous plants. They are also called tidal marshes or saltings. 'Ing' is a word of Nordic origin, meaning 'meadow' and saltings made quite rich cattle pasture which was also free of liver fluke (Fasciola hepatica and others). Care should be taken not to confuse 'salting' with 'saltern', which is a salt-house. Salterns were not found among salt marshes and are places where brine is evaporated to produced salt.
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[edit] Conditions required
The water is saline, and both the water table level and salinity are dependent on tides. Salt marshes develop on depositional coasts where tidal action is relatively gentle and erosion no more than intermittent and light enough to allow vegetation to take hold. They are common on low-energy coasts such as estuaries, enclosed bays, and the land sides of barrier islands and strips.
The sediment in salt marshes is delivered not constantly, as in other types of marshes, but cyclically, owing to the tides. As would be expected at the coast, the sediment is rich in sand, shells, and organic material from the ocean.
[edit] Vegetation
Plant species diversity is low, since the flora must be tolerant of salt, complete submersion, and anoxic mud substrate. The most common salt marsh plants are glassworts (Salicornia spp.) and the cord grasses (Spartina spp.), which have worldwide distribution. They are often the first plants to take hold in a mudflat and begin its ecological succession into a salt marsh. Their shoots lift the main flow of the tide above the mud surface while their roots spread into the substrate and stabilize the sticky mud and carry oxygen into it so that other plants can establish themselves as well. Plants such as sea lavenders (Limonium spp.), plantains (Plantago spp.), and varied sedges and rushes grow once the mud has been vegetated by the pioneer species.
The flora of a salt marsh is differentiated into levels according to the plants' individual tolerance of salinity and water table levels. Vegetation found at the water must be able to survive high salt concentrations, periodical submersion, and a certain amount of water movement, while plants further inland in the marsh can sometimes experience dry, low-nutrient conditions.
Salt marshes are quite photosynthetically active and are extremely productive habitats. They serve as depositories for a large amount of organic matter, and are full of decomposition, which feeds a broad food chain of organisms from bacteria to mammals.
In wintertime the saltmarsh looks more open than in summer. More space is seen between reeds as snow falls between them. The water partly freezes, which makes it look rather spectacular.
[edit] Marais salants
In warmer climates, salt can be produced by solar energy so that the French equivalent of the salt marsh, the marais salant has come to be envisaged primarily as an industrial plant, though classified as a form of agriculture, known in French as saliculture. For this aspect of the salt marsh, see also Salt evaporation pond.
[edit] Wetland dieback
In the summer and fall of 2002, Dr. Scott Warren at Connecticut College and Ron Rozsa of the Connecticut Department of Environmental Protection, noticed the sudden (within one year) disappearance of emergent vegetation at several south shore Cape Cod wetlands connected to Nantucket Sound. The vegetation loss could not be explained by any typical New England causes of vegetation loss such as ice, wrack or herbivory (e.g., geese or muskrat).[1]
Four years later, the cause is still unknown, but there are 17 suspected dieback marshes on Cape Cod, and a few other possible sites are on the North and South Shore, according to the Wetland Restoration Program of the Massachusetts Office of Coastal Zone Management.
In Louisiana, 300,000 acres (1200 km²) turned brown around the year 2000. In 2002, researchers noticed that about 2,000 acres (8 km²) of salt marsh in Georgia turned to mud, similar to what is happening in New England. But as of mid-2006, the Louisiana and Georgia marshes are growing back -- or at least not getting worse -- while marshes on the Cape don't seem to be recovering naturally. [2]
[edit] External links
- Geography resource for schools
- Salt Marsh Nature Center located in the Marine Park section of Brooklyn, New York, USA
