Salt marshes are transitional areas between land and water. They are found along the intertidal shore of estuaries and sounds principally along temperate and boreal coasts, although occasionally they occur in the tropics on areas not occupied by mangroves. Salty (saline) water and the influence of tides are defining factors of this type of wetland. The salinity of saltwater marshes is not a fixed value, but rather changes with distance from the ocean, water depth, freshwater input (i.e. precipitation, runoff, ground water) and season, ranging from near ocean strength to near fresh in upriver marshes. They are usually vegetated by salt-tolerant grasses, rushes, sedges and other soft-stemmed plants, and their distribution varies mainly depending on flooding and salinity conditions.
Salt marshes like mangroves, their counterparts in the tropics, serve many important functions. They buffer stormy seas, slow shoreline erosion, and are able to “filter” excess nutrients and sediments before they reach the estuaries and the sea. They also provide food, habitat, spawning and nursery grounds for many different species of aquatic organisms. Fish, crabs, shrimps, and mollusks, for example, live in salt marshes where stems, leaves, and roots provide food and shelter from predators. The young of many species, such as the blue crab, white shrimp and spot tail and striped bass utilize the salt marsh as a nursery, where the abundant food and protection provided by marsh plants increases their survival to adulthood.
