After its attachment, the barnacle begins to produce the calcareous plates that will encase it. As it grows, so too will its shell. The barnacle's shell is composed of calcium carbonate. The shell is enlarged by adding calcium carbonate along the edges of each plate, increasing the size of the inside cavity. Then, like other crustaceans, the barnacle sheds its exoskeleton, growing in size.
Barnacles adhere to piers, boats, plants, rocks and shells in the intertidal zone.
This is an area that is submerged by tides and then exposed to air as the tides recede. When the barnacle is exposed to the air during low tide, the two flaps which open at the top will shut tightly. This keeps the animal inside moist until the tide rises again. Three species of barnacle are found in Chesapeake Bay and its tributaries. The ivory barnacle Balanus eburneus, found in lower Bay region, also thrives in the intertidal and subtidal zones, but tolerates higher salinities, ranging from 5 to 30 ppt.