The rocky intertidal habitat lies between the high and low tide marks, and it is regularly covered and uncovered by the advance and retreat of the tides. Due to the periodic exposure to air and the predominant presence of wave action, the plants and animals that live in these areas are hardy and adaptable. Rocky intertidal habitats are characterized by their high biodiversity and distinct zonation. Common species found in this habitat include barnacles, mussels, chitons, sea urchins, grazing snails, sea stars, hermit crabs, sea anemones, and several species of macroalgae. Assemblages of different species are spatially distributed in very distinct zones depending on tidal height, wave exposure, and a range of other physico-chemical and biological parameters including temperature, light, nutrients, salinity, predation, competition for space, grazing, settlement and recruitment, species associations, and movement behavior. Differentiated zones in a rocky intertidal environment include the splash zone, which is almost always exposed to air and thus is colonized by only few species; the higher intertidal zone, exposed to air for long periods of time; the mid-intertidal zone, exposed to air for only short periods of time; and the lower intertidal zone, which is exposed only during the lowest tides.
The biomass produced in rocky intertidal habitats supports not only organisms associated with this habitat but also organisms found in adjacent soft-bottom habitats or kelp forests. Direct consumers in the rocky intertidal habitat include chitons, sea urchins, and grazing snails, while deposit and filter-feeding worms, clams, and other invertebrates feed from the detritus derived from the decomposition of macroalgae. These organisms then provide food to fish and birds associated to these habitats. Tidepools in the rocky intertidal habitat serve also as nursery grounds for subtidal fish.
