Salt marshes are low coastal grasslands that are covered at least once a month by the rising tide, and are found on the edges of estuaries. A salt marsh forms when incoming tides carry and deposit sediment across low-lying land, resulting in wet mudflats. Saltwater grasses then slowly take hold and spread, stabilizing the land through the growth of root systems. As the plants decay and sediment builds up, peat deposits accumulate, forming a rich habitat that supports the growth of hundreds of diverse organisms. A salt marsh is divided into four zones. Low marsh, high marsh, salt pan and the hammock.
The Lower Marsh is often submerged under saltwater, and supports the growth of organisms adapted to high salinity and lots of moisture. Here larger animals live in the safety of the tall grasses called cordgrass. The High Marsh is a drier area, where plants tolerate lower salt concentrations. The high marsh changes with the tides. When the tide is high the water covers most of the land. When the tide is low animals hide in the protection of the grasses and some dig
holes. The salt pans are small depressions that trap and hold water on a high tide. Salt pans or transition zones are where the land is high and moist from high tides. When the hot sun bakes down on the shallow water it evaporates and the minerals in the salt water is left behind and most of it is salt. The highest edges (Hammock), is the only dry land of the marsh and are only reached by extremely high tides, such as during a storm.
Smooth cordgrass (Spartina alterniflora), dominates the regularly flooded lowmarsh. Cordgrass’s successful adaptations enable it to live where few other plants could survive. It has narrow, tough blades and special glands that secrete excess salt, making it ideal to withstand the high heat and daily exposure to salt water. Few animals eat this plant, but many animals and plants live on it or on the marsh surface protected by its roots and stalks. Cordgrass stalks are thick and are very tough and well anchored by a root system. There are two forms of cordgrass. A tall form grows along creek banks and can reach heights of 9 feet.
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