Geukensia demissa - Atlantic ribbed mussel, Ribbed mussel
Habitat These mussels can be found most commonly in inter-tidal zones and at the lowest shore levels in salt marshes. They are usually attached to a hard substrate or can be embedded in sediment by their byssal threads. They can also aggregate at the base of grass stems (Spartina alterniflora) in low marshes. These mussels can tolerate a wide range of water temperatures (ranging up to 45 degrees C) and salinities (from 6 to 70 ppt). It is their great adaptability that makes them perfect for salt marshes that experience different tide levels.
Range The ribbed mussel can be found all along the Atlantic coast. They range from the southern Gulf of St. Lawrence, Canada to northeastern Florida and along the Gulf of Mexico from Florida to Yucatan. They have also been introduced to parts of California.
Description The ribbed mussel is a relatively large mussel and can grow up to 10 cm in length. The surface is grooved and has a glossy, brown-black color with some yellow tint. The inner surface is usually a white color. Some distinguishing features of the ribbed mussel are it's oblong shape, parallel dorsal and ventral margins and very close exterior ridges.
Ecological Notes Ribbed mussels are filter feeders and open their shells to pump water through their body to filter out microscopic plankton and detritus while submerged under water. However, during low tide, they close up to retain moisture, but may open it for evaporative cooling purposes. These mussels are commonly preyed upon by crabs (such as Callinectus sapidus), but can also be the prey for some shore birds. These mussels also have a mutualistic relationship with Spartina alterniflora. Mussels attach to the base of the grass where they defecate and provide nutrients to the grasses.
Personal Information Live Geukensia demissa were found in the channels behind the Coastal Studies Institute in North Carolina as well as on the shores at Cape Hatteras.
Bertness, M. D., Grosholz, E. 1985. Population dynamics of the ribbed mussel, Geukensia demissa: The costs and benefits of an aggregated distribution. Oecologia. 67(2):192-204.
In this article it was found that juvenile ribbed mussels settle gregariously with or without adults present. The aggregated distribution of settlers and the postsettlement movement of smaller mussels to favorable micro-habitats resulted in size and age class segregation within the population. It was concluded that this probably reduces intraspecific competition for food, while maintaining the survivor-ship advantages of an aggregated distribution.
Bertness, M.D. 1984. Ribbed Mussels and Spartina alterniflora Production in a New England Salt Marsh. Ecology. 64(6):1794-1807.
This article further describes the mutualistic relationship between Spartina alterniflora and Geukensia demissa. It was seen that the ribbed mussels increase the soil nitrogen concentration which in turn aids in the growth of the grass. The grass then in turn benefits the growth and reproductive success of the mussel.
Contributed by Ophelia Whitmore - 2014