Intertidal Zonation Patterns
The rocky intertidal is the portion of a rocky coastline that is periodically covered or exposed by daily tidal changes. This interface is a complex environment where species are well adapted to the changing habitat conditions. Conditions are more terrestrial higher in the intertidal and correspondingly more marine in the lower intertidal area, depending on the amount of exposure the area receives.
This range of environmental conditions influences the species that are able to adapt to changing habitat variables and these environmental conditions are in part responsible for the unique zones within the intertidal that are highly visible by the dominant species that occur in each area or “zone.” These dominant species create stripes that take the color and texture of the dominant or “characteristic” organism of that zone (Niesen 1982).
The splash zone is the area above the high tide water line and mainly depends on sea spray and mist for water coverage. View organisms that live in this zone below, and scroll over an organism to learn more about it.
Striped Shore Crab
Striped Shore Crab
Pachygrapsus crassipes – Like all crustaceans, these crabs have gills, but they can survive out of water for up to 70 hours. They have been known to eat everything in the intertidal, including their own species. They can be found throughout all zones of the intertidal, but are usually resting in shady cracks and crevices.
Littorina spp. – These tiny snails are often mistaken for eggs or rocks. During the low tide, the snails seal the water inside their shells with a trap door called an operculum. Their shells become the first home for juvenile hermit crabs.
High Tide Zone
The high zone is the area of intertidal that is covered by most high tides. View organisms that live in this zone below, and scroll over an organism to learn more about it.
Mytilus californianus – Mussel beds form a very important habitat for other critters and it has been reported that over 1000 species have been found living within these mussel bed habitat created by the California mussel. Mussels have numerous natural predators, but often are disturbed and collected by humans for bait, aquaria or killed through incidental trampling.
Strongylocentrotus sp. – The purple urchin is a more common species and is about the size of a golf ball. These urchins feed primarily on brown algae and often concentrate their efforts on the holdfast of the kelp. There is a commercial dive industry for the red urchin and the gonads are commonly served in Japanese restaurants.
Mid Tide Zone
The mid zone is characterized by the highly recognizable intertidal species the seastar (Pisaster sp). View organisms that live in this zone below, and scroll over an organism to learn more about it.
Black Turban Snail
Zonaria spadicea – The chesnut cowrie is named for its beautiful chesnut-colored, polished shell. They can eat a wide range of foods including anemones, snail eggs, and carrion.
Pisaster ochraceus – The ochre star is the most common sea star in the intertidal. It can eat anything that can’t move out of the way including snails, barnacles, chitons, and mussels. It can pry open mussels using it’s powerful tube feet.
Blue Banded Hermit Crab
Pagarus spp. – Hermit crabs are a unique animal because they use the discarded shells of intertidal snails to protect themselves from exposure. They will change shells as they grow, often keeping an eye out for new empty shells, but have been known to steal shells from other hermits. As a defense, they will draw their legs into their shells and fall to the bottom of their tidepool.
Black Turban Snail
Chlorostoma funebralis – Like other snails, Black Turban Snails use a scraping tongue called a radula to eat algae growing on the rocks. Black Turban Snails are a eaten by crabs and birds, and their shells are a favorite for hermit crabs.
Low Tide Zone
The low tide zone is mixed with organisms that can be found in both the intertidal and sub-tidal habitats and is characterized by the large fleshy brown algae that begin to appear in this zone. View organisms that live in this zone below, and scroll over an organism to learn more about it.
California Spiny Lobster
Mopalia muscosa – Chitons like this mossy chiton, are snail-like mollusks. They have a single muscular foot, and 8 jointed shell plates. It stays in one place during the day leading visitors to assume that they are fossils, but at night they move and graze on algae growing on the rocks.
Aplysia Californica – Sea Hares are named for their broad antennae that look like a hare’s ears. They are herbivores, so they eat red, brown, and green algae. They can release a dark purple ink if disturbed or irritated. They have been observed to lay almost 480 million eggs in one season.
Panulirus interruptus – Unlike Maine lobsters, CA spiny lobsters do not have huge front claws. They shed their exoskeletons periodically as they grow, and their molts can be found along the shore line. They have been observed to live 50 years.
Patiria miniata – Bat stars are named for their webbed arms. They come in a huge variety of colors, and can have mottled patterns too. They eats algae and animals, both dead and alive.
Parastichopus spp. – Sea cucumbers look like sea slugs, but are actually closely related to sea stars and urchins. It has one of the most unique defense mechanisms of all tidepool creatures. When in extreme danger, it will eject its internal organs in an effort to distract its predator. If it survives being eaten, it can regenerate these organs!
Ophiuroidea – These small sea stars spend the day hiding under rocks and in crevices. They can also be found in the holdfasts of giant kelp that has washed up on shore. They eat mostly detritus and pieces of food that they are able to pick up with their tube feet.
Octopus bimaculoides – Living only 1-3 years, the two-spot octopus is arguably the most interesting animal in the intertidal. It can change color instantly using specialized cells called chromatophores. It can drill into their shelled prey using a scraping tongue called a radula. They can crawl around outside of the tidepools, and are adept at swimming using their siphon. Studies show that they have the intelligence of a 3 year old human!
Anthopleura spp. – Anemones are related to jellies and corals, and have small stinging cells in their tentacles. They are adapted to surviving exposure during low tide by using shell fragments as a protective armor. They have a symbiotic algae living within their cells that provide supplemental nutrition and oxygen.
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