Intertidal Zone

The intertidal or littoral zone is the area of the beach between the high water mark of high tide and the water mark of low tide. It is neither land nor sea, but periodically partakes of both. The cycles of the intertidal ecosystem generate a matrix of life. This zone is inhabited by many organisms, all of which are highly adapted to a challenging habitat. Sometimes their home is hot and dry, baked by the sun. Sometimes it is deluged with fresh rain water. Sometimes it is under sea water, washed by waves and surf. Intertidal organisms experience a wide range of salinity, depending upon their location, whether closer to the low tide mark or the high tide mark. Intertidal organisms exhibit a wide range of adaptation which enables them to survive periods of dessication.

The intertidal zone hosts a rich biological diversity. Some of the organisms which live in this zone include barnacles, chitons, small gastropods, isopods, limpets, mussels, starfish, snails, whelks, anemones, abalone, brown seaweed, crabs, green algae, hidroids, nudibranch, sculpin, sea cucumber, sea lettuce, sea palms, sea stars, sea urchins, shrimp, snails, sponges, surf grass, tubeworms, and some herbivores. The famous Pismo Clam was an intertidal inhabitant. This once plentiful denizen of the intertidal zone has become so scarce that Pismo Clams are no longer found on Pismo Beach.

The Oceano Dunes State Vehicle Recreation Area is accessed by vehicles exclusively by driving along the intertidal zone of the Pismo-Oceano Beach. The regular assault by as many as 50,000 gasoline burning vehicles per weekend over a period of decades on the intertidal ecosystem of this area has had devastating effects. In other areas these valuable zones are designated Marine Protected Areas and are preserved intact for scientific study.