Salt marshes form in quiet coastal areas where an incoming tide deposits sediments that are trapped by cordgrass (Spartina alterniflora). Usually these areas have reduced erosion pressures and are characterized by a muddy substrate. The salt marsh terrain is quite irregular. Small, shallow and muddy areas form that periodically fill up with water. These pools are called pannes and are often biologically rich with tiny organisms that attract birds and other animals. Many species such as mummichogs and shrimp may get trapped in these pannes. I once found a young, one inch horseshoe crab in one.
The pannes tend to be quite salty, particularly in the summer when evaporation is more rapid. I’ve observed pockets of exposed mudflats around a panne in which the succulent glasswort (Salicornia europaea) is the first plant to colonize the area. Later this may be replaced by the salt marsh hay (Spartina patens) as succession continues.
There are extensive salt marshes along the east coast of North America, including Massachusetts, although most of them are located in the southeast. The Great Barnstable Marsh consists of about 4,000 acres including the area behind the six mile Sandy Neck barrier beach. A salt marsh is periodically submerged and contains a significant diverse community of plants and animals. The plants provide a major source of nutrition to large numbers of animals, either through direct consumption or after they have died and decomposed. Such decayed organic material is called detritus and may be transported throughout the marsh and even offshore by daily tidal action. This detritus supports an abundant fauna including clams, mussels, blue crabs, shrimp, and several species of fish.
Salt marshes play an important physical role along the coast. They act as buffer zones between the powerful energy of oceanic waves and the land. In some low lying sections of the country, a salt marsh may help prevent salt water intrusion into drinking water supplies.
The public has now come to understand that salt marshes are not wastelands or simply breeding grounds for greenhead flies. Too many acres have been cleared and filled, thus damaging the coastline by accelerating erosion. In spite of coastal wetland regulations, salt marshes are not fully protected. Incremental losses by encroachment of development will continue to threaten these valuable ecosystems as long as population pressures continue to squeeze the last remaining acres of upland.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.