The Salt Marsh

A marsh is really a flooded meadow, dominated by grasses and other herbaceous (non-woody) plants. In a salt marsh, the flooding waters are salty, carried in twice each day by the action of the tides.

Throughout the temperate world, salt marshes stretch along the shores and inlets of estuaries like the Chesapeake Bay, as well as the lagoons that form behind barrier islands.
Marsh Zones
Plants of the salt marsh grow in zones, in response to the amount of time each day that the ground is flooded. Salt-marsh cordgrass indicates the lowest plant zone. This part of the marsh, between the marks of low and high tide, is under salt water twice daily.
A Place of Stress  
The salt marsh is a rigorous environment. Relatively few kinds of plants and animals can live here, much less thrive.

Dwellers in the salt marsh must cope not only with daily and seasonal changes in light, air temperature, and humidity, but also with fluctuations in level, temperature, salt content, and oxygen content of the water. 
Food Factory
Acre for acre, the salt marsh is one of the most productive ecosystems on earth, surpassing even intensively cultivated agricultural lands.

The exceptional fertility of the marsh results from a continual bath of nutrients deposited both by salty tides and freshwater streams that drain the inland.
Blue Crab
Scientific Name: Callinectes sapidus
Callinectes sapidus means “beautiful swimmer, savory,” an apt description of this delicious, multicolored crab that is found throughout the Chesapeake Bay and its tributaries. Millions of pounds of crab are harvested in the bay each year for consumption either as hard crabs or “softshells.” The latter are collected just after the crab has shed (molted) its hard shell during the growth process but before the new shell hardens. 
Size: 9 in. (23 cm) 
Blue Crab Growth
Blue Crab Juvenile
Blue Crab
Scud (Spine-backed scud)
Scientific Name: Gammarus mucronathus
Scuds, small and shrimp-like, are somewhat compressed or flattened side-to-side, moving by sliding along their sides and pushing with jointed legs. Mats of algae and other vegetation form their typical habitat. The larger males often carry the small females.
Size: ½ in. (1.2 cm)
Marsh Periwinkle
Marsh Periwinkle
Scientific Name: Littorina irrorata
Marsh periwinkles cluster on grass stems. When the tide rises, the snails climb up the stalks, apparently to escape predatory blue crabs. Periwinkles feed on algae, bacteria, and decaying vegetation.
Size: 1.25 in. (3.2 cm)
Salt Marsh Cord Grass
Saltmarsh Cordgrass
Scientific Name: Spartina alterniflora
Saltmarsh cordgrass is typical of the low marsh. It grows luxuriantly despite regular flooding by salt water and a smothering substrate of oxygen-poor mud. Cord grass deals with the heavy salt load by secreting the excess through little glands on its leaves and preventing its roots from suffocating in the mud by supplying them with oxygen absorbed from the air through special leaf pores.
Size: to 8’ (2.5 m)