Any firm stable surface in the intertidal zone has the potential to support the organisms that commonly occur in rocky intertidal communities, and at low tide, intertidal habitats can range from dry rock to filled tide pools. Rock surfaces can vary from very hard to relatively soft rock such as from granite to sandstone and can range from smooth platforms to irregular fields of stone cobbles and boulders. Topography, inclination, color, and texture of the rock affect rate of drying and surface temperature, which can limit the distribution and abundance ofspecies.
Man-made surfaces such as rock jetties and wooden pier pilings and biogenic surfaces such as mangrove roots can also support communities that are indistinguishable from the communities found on nearby rocky shores.
Tide pools can be very different than the surrounding shore because of thermal variability, changes in salinity from evaporation and runoff, and changes in pH, nutrients, and oxygen levels caused by algae. Pools often support residents such as sea urchins, snails, and fish that would otherwise be restricted to subtidal areas.
The amount of wave surge affects the types of organisms found on the shore and their distribution. Wave surge and breaking waves tend to expand the extent of the intertidal zone and distribution of species by continually wetting the shore and allowing species to extend farther up the shore. Wave surge can also cause mobile animals to seek refuge and can limit the distribution of slow moving species, and the force of breaking waves can damage and sweep away organisms. Sand and debris such as logs swept up by the waves can scour organisms off the surface. In areas of low wave surge, sedimentation of sand and silt may bury organisms or clog gills and other filterfeeding structures.
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