A primary example of mutualism in estuaries is the relationship between fiddler crabs and Spartina alterniflora, a type of smooth cordgrass. Spartina is an essential component in the estuarine ecological system.
Many types of relationships exist in marine environments, such as mutualism, parasitism and commensalism. Mutualism pertains to the interaction between two varying species, wherein both organisms benefit from the close association.
Estuaries are semi-enclosed coastal bodies where freshwater from rivers and streams converge with seawater. Spartina grass, characterized by its sturdy, dense stalks, is specially adapted to living in these saline conditions. The cordgrass forms a mutually beneficial relationship with fiddler crabs, which commonly dig burrows for their habitats. Through its tight root network, the cordgrass stabilizes the soil so that the burrows do not collapse. In return, the fiddler crabs provide the cordgrass with oxygen by aerating the soil.