Blue mussels, or Mytilus edulis, are commonly found in the mid-intertidal zone all the way down to the subtidal areas. They are bivalves, meaning they have two (bi) shells (valves). Like most bivalves they are filter feeders, scavenging the water for tiny particles of food, like phytoplankton. You can find mussels growing in large, dense groups or beds in the mid-intertidal area. Group-living can have its benefits such as: increased chances of fertilization, protection from predation, protection from heat and desiccation stress.  Group-living also allows the species to occupy and hold space, preventing attachment by other species. The downside is that competition for food can be fierce. Mussels have some special adaptations. They can anchor themselves to the substrate, quickly colonize a new area, and there is something about the shape of that shell...let's find out more...