Organisms are distributed throughout the intertidal zone based on their ability to cope with the stresses of this environment. Space is usually the most limiting resource in rocky intertidal communities. The distribution of species is governed by the competition for living space and the need to find food and shelter while avoiding predators, or suffering from extremes in heat or cold. For example, competition for space between mussels, barnacles, and rockweed leads to the formation of distinct bands dominated by these species. While the hard substrate does not allow animals to burrow, cracks, crevices, overhangs, and rock bottoms create microhabitats in which to hide from predators, minimize wave shock, and avoid desiccation.

By identifying the dominant organism you can often tell which zone you are in.

• Lichen is the dominant organism in the Spray Zone. Lichens are fungi that have formed symbiotic relationships with algae. They commonly grow on rocks and trees.
• The "black" in Black Zone or Upper Intertidal refers to the blue-green algae that covers the rock faces. WARNING-VERY SLIPPERY WHEN WET.
• The barnacle is the most visible organism of the Mid-Intertidal Zone. Firmly attached to the rocks, these shrimp-like crustaceans survive inside their calcium shell when the tide leaves them exposed.
• Brown algae is the most common seaweed found in the Lower Intertidal Zone. There are two distinct species of brown algae: knotted wrack and rockweed.