There are many different types of wetlands. Wetlands are areas where there is a gradual transition from land to water. Wetlands include swamps, tidal flats, lagoons and marshes. Along the Southeastern coast, the most familiar type of wetland is the coastal saltwater marshes. In the marshes along the coast, salt water comes in and flushes the area twice a day and brings in nutrients and organisms from the ocean. This area is called an estuary. An estuary is a semi-enclosed body of water where the salt water of the ocean meets fresh water of a river.
At the center of this ecosystem is cord grass. The cord grass extends its roots into the deep soft mud and provides a solid foundation for organisms to make a home. One of the most common plants found in the salt marshes is the cord grass Spartina alterniflora.
This plant thrives in estuarine environments because it has special adaptations that allow it to withstand the salt water from the tide. Plants that are capable of living in environments that have high salt content are referred to as halophytic plants. The spartina releases the salt through transpiration leaving it visible on the blades of grass. When the Spartina decays, it decays to form detritus which provides nutrients for the mussels, oysters, clams, grass shrimp and snails. Other organisms such as raccoons, fish, blue crab, egrets and horseshoe crabs feed on the detritivores.
Also found in the coastal marshes are the mud flats. The erosion from the freshwater rivers and the flowing tide carries a wide variety of sediment towards the coast. When silts and clays settle, they are deposited in areas of low flow. The sediment is so fine that they silt and clay pack together leaving no room for oxygen. The bacteria and fungi that live in the mud must carry out anaerobic respiration using sulfate and releasing hydrogen sulfide. This leads to the characteristic “rotten egg” smell of the mud flats.
Some coastal marshes also have sand flats. Sand is also deposited by the moving water and collects on the inside bends of fast current areas.
Additionally, oyster reefs are found near the coastal marsh. Oyster larvae survive as plankton until they attach to a hard substrate. The most common substrate for oyster larvae is adult oyster shells! Therefore, huge oyster reefs are formed in the intertidal habitats of the coastal marshes as oysters continue to settle and grow on their own kind.
Despite the extreme changes in temperature, salinity and water quality caused by the ebb and flow of the tides, the coastal marshes are extremely productive and ecologically important. Coastal marshes provide nutrients to organisms, protect the coastal environment from erosion and nutrient loading and serve as nursery grounds for a host of juvenile organisms. Out of all the coastal ecosystems, the coastal salt marsh is the most dynamic and rigorous. Salt marshes stretch over millions of acres along the southeastern coast of the United States. However, despite their importance, humans have overused the marshes for livestock grazing, hay harvestation, and economic development.