Biological zones are defined on the basis of degree of exposure during the tide cycle. Each zone has a distinctive group of sessile animals or plants. They feed on green algal coatings on rocks. They live in cracks in rocks, borings in rock, and under loose cobbles or rocks where they are sheltered from wave action and light. Attached in large masses to hard surfaces.
Snails eat mussels and barnacles.
Limpets look like Chinese hats and browse on algal coatings. Different species of kelp can live throughout the rocky shore ecosystem. Kelp, giant algae, grow rapidly to the ocean surface from hold fasts. Floats keep them upright in the water and they sway back and forth with the waves. Large leaves allow the kelp to receive sunlight over a large surface area.