Both are marine intertidal areas with soft substrate, colonized predominantly by grasses. They occur only where there is regular flooding and nearby sources of fine sediment. Salt marshes form on stable or emerging coastlines when sediment accumulates in sheltered intertidal areas in estuaries, behind spits, bars or islands, and in protected bays. In Nova Scotia, where coastlines are submerging at a slow rate, marshes form when the rate of sedimentation exceeds the rate of submergence. The key plant of the salt marsh is cord grass, Spartina.
Marshes are often nurseries for juveniles of commercially important fish species.
They are important feeding and breeding habitats for waterfowl. Marshes were used by early settlers as a rich source of hay. Colonists dyked much of the Bay of Fundy salt marsh, converting it to permanent cropland. Cord Grass, Bay of Fundy, Spartina spp.