What To See

Intertidal Zonation Patterns

The rocky intertidal zone 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 ecosystem 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 habitat 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).

Splash Zone

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

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.

Periwinkle Snail

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.


The high zone is the area of the intertidal habitat 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.

California Mussel

Mytilus californianus – Mussel beds form a very important habitat for more than 300 marine species. These filter feeders have numerous natural predators such as sea stars, shore birds, and sea otters, but often are disturbed and collected by humans for bait and aquaria, or killed by incidental trampling.

Purple Urchin

Strongylocentrotus sp. – The purple urchin feeds primarily on brown algae that gets stuck on its spines in tide pools and often concentrate their efforts on the holdfast of the kelp when in the ocean. Although purple sea urchins are smaller than their less common counterpart the red sea urchin, both are commonly served in Japanese restaurants as uni.

Mid TIDE Zone

The mid zone is characterized by the highly recognizable intertidal species, the ochre sea star (Pisaster ochraceus). View organisms that live in this zone below, and scroll over an organism to learn more about it.

Chestnut Cowrie

Neobernaya spadicea – The chestnut cowrie is named for its beautiful chestnut-colored polished shell. These snails are the only cowrie found in the east Pacific Ocean. Often hiding under rocks and protected crevices, these creatures are carnivorous eating sea anemone, sea sponges, and other dead organisms.  

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.

Ochre Star

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. Identified as a keystone species, ochre sea stars allow for a diverse rocky marine intertidal. Its only known predators are sea otters and gulls.

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.


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.

Sea Cucumber

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!

Sea Hare

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.

Brittle Stars

Ophiuroidea – These small sea stars spend the day hiding under rocks and crevices such as mussel beds. They can also be found in the holdfasts of giant kelp that have washed up on shore. They are scavengers where they will eat decaying matter or plankton. 

California Spiny Lobster

Panulirus interruptus – Unlike Maine lobsters, California spiny lobsters do not have huge front claws. Instead, all their appendages are used for walking. They shed their exoskeletons periodically as they grow, and their molts can be found along the shoreline. These lobsters will hide in crevices during the day and move around at night feeding on sea urchins and mussels. A few predators of the spiny lobster are the California sheepshead, sea bass, and sea otters.

Two-Spot Octopus

Octopus bimaculoides – Living only 1 to 3 years, the two-spot octopus can change color instantly using specialized cells called chromatophores. It can drill into their shelled prey using a scraping tongue called a radula. The two spots below the eyes of the octopus act as eyes to distract predators. Studies show that they have the intelligence of a 3-year-old human!

Bat Star

Patiria miniata – Bat stars are named for their webbed arms. They come in a huge variety of colors and can have mottled patterns. They eat algae and animals, both dead and alive. Other sea stars, mollusks, and crustaceans will feast on these bat stars. 


Anthopleura spp. – Anemones are related to jellies and corals and have small stinging cells in their tentacles known as nematocysts. They adapt to surviving exposure during low tide by collecting shell fragments to remain moist. They have a symbiotic alga living within their cells that provide supplemental nutrition and oxygen.