Mytilus edulis in the Rocky Intertidal at Nahant, MA
My Experiment


The blue mussel, Mytilus edulis, is an abundant species in the rocky intertidal in the Gulf of Maine. They are also commonly found on the other side of the Atlantic Basin, on the shores of England. They belong to the Phylum Mollusca (have hard outer shells) and the Bivalve class (have a shell divided into two parts, like a clam or an oyster).  The shape of their shell is almost like a rounded triangle and can be purple or blue to a dark, nearly black color. Mussels are considered sessile organisms. They are found in mussel beds, a close association between a number of organisms of the same species. The close association helps protect individuals against wave stress (Denny et al. 1985) and desiccation and heat stress (Bertness and Leonard 1997) as well as enhancing the success of fertilization (Denny et al. 1985), which occurs externally in Mytilus. Their larvae are planktonic for as long as three months, after which they secrete a shell and settle as plantigrade larvae, about .5-2.0 mm in size (Bertness 1999). They initially settle on filamentous algae, or a rough surface near, but not with adult mussels. Once they have grown to a larger size they go through a secondary settlement into adult mussel beds (Bayne 1964). Mussels attach to the surface of the rock by byssal threads. Mussels are filter feeders, actively pumping water over ciliated gills, taking in nutrients and pumping out excess water. Because mussels can actively pump water they are not dependent on water flow, but they do need to be submerged in water to feed. Mussel beds also modify the habitat for other organisms by slowing water flow, trapping sediments, accelerating sedimentation and preventing erosion. Their shells can become a good hard-substrate surface for encrusting algae and the area between their shells is also a good spot for other small organisms (Bertness 1999).

The place at Nahant were the study was done is the home of Northeastern University’s Marine Science Center. It is a relatively small rocky outcropping into the Gulf of Maine, located just north of Boston. The species found here are typical to the rocky intertidal of the Gulf of Maine, a diverse ecosystem with an abundance of interactions and patterns to be studied.

© 2002 Laura Brentner, for educational purposes only

A Mussel Bed


A mussel showing off its byssal threads


Nahant, MA Rocky Intertidal

Juvenile Resettlement
More info about byssal threads!
Zonation of Mussels in the intertidal
Batillaria Page