What to See
Get ready to be amazed when you visit the tidepools.
But first, let’s learn about the tidal zones.
Tidepool life in Southern California
The intertidal ecosystem is at the edge of land and sea, shifting with the movement of the tides. There are four distinct zones with different characteristics in the intertidal area, as well as a subtidal zone that is slightly lower in the ocean. Intertidal zones also vary in levels of predation, interspecies competition, temperature stress, desiccation (drying out), and salinity.
Each zone is populated by various species depending on their tolerance of exposure to water, air, or physical stressors like heat shifts. For example, mussels are limited to the mid and low intertidal zones due to their vulnerability to drying out in air.
As the tide withdraws, it can also leave tidepools behind in pockets of rock formations. These serve as a refuge for any animals that are not adapted to remaining out of the water, such as sea stars, nudibranchs, or small fish.
Spray/Splash Zone
The spray zone is the highest area, just above the water level at high tide. It receives mild water exposure from waves splashing and sea mist. Organisms here require adaptations to resist high temperatures in the summer and cold in the winter. Under spring tide (“King Tide”) or storm conditions, this zone may temporarily be underwater.
Common Species Found in Zone:
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.
High Zone
The high zone remains in the open air for most of the day but is covered by water at high tide. It is populated by aquatic life that can withstand more exposure to the elements, including crabs, chitons, and limpets. In Southern California, this zone is often indicated by the presence of larger acorn barnacles (Balanus glandula).
Common Species Found in Zone:
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 Zone
The mid zone alternates between being submerged and being above water multiple times in a day. Organisms in the mid zone must be firmly rooted in place or flexible to not be battered by the energy of the waves. This zone is also characterized by swaths of rockweed and mussels, which help form shelter for other creatures.
Common Species Found in Zone:
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.
Ocre 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.
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 Zone
The low zone is typically covered by water, except for brief exposure to the air during low tide. Temperature fluctuations are mediated by the water, such that conditions underwater remain more consistent. Red and brown algae can be found in the low zone, as well as a greater number of aquatic animals like shrimp, snails, nudibranchs, anemones, and sea hares. The higher water level in the low zone means these animals are in less danger of desiccation or temperature shock.
Common Species Found in Zone:
Chiton
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 sp.
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.
CA 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.
Anemones
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.
Subtidal Zone
The subtidal zone lies just below the intertidal ecosystem. It is continuously underwater unlike the intertidal zones but remains shallow in depth. Due to a constant layer of insulating water, the temperature and light exposure levels of this zone are mediated and remain more consistent. Larger aquatic animals like fish and octopuses are more common in the subtidal zone.
Common Species Found in Zone:
Opaleye
Juvenile Opaleye are often found swimming in tidepools. They are usually a gray/green color, most often seen with little white spots on their backs, but their namesake comes from their blue (opal colored) eyes! Although the eyes might be difficult to be seen when they are so small, by the time they are full grown it is definitely a distinguishing feature. Baby to Juvenile Opaleye live in tidepools for protection, usually eating seaweed, but occasionally getting hungry enough to eat an
invertebrate. As they mature, usually about 6 inches, they head out of the tidepools to live in the Kelp Forest where they can grow to be 26” (over 2 feet) long! They also have been known to occasionally gulp air if oxygen is becoming too low in the tidepool water.
Garibaldi
Garibaldi damselfish is a species of bright orange fish in the damselfish family. It occurs in the subtropical northeastern part of the Pacific Ocean. The Garibaldi is the official marine state fish of California as of 1955, and has since been protected in California coastal waters from recreation and commercial fishing
Abalone
Abalone shells are distinctive for their flattened, ear-like shape, nacreous interior, and row of holes used for respiration. The flesh of abalone is widely considered to be a delicacy, and is consumed raw or cooked by a variety of cuisines. Abalone are globally distributed, with approximately 70 known species alive today. Though some species are small, the largest abalone can attain a length of 300 millimetres (12 in).