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Natural Bridges State Beach Tidepools Exploration

The intertidal rocks at Natural Bridges State Beach are covered in life: sea stars, seaweeds, urchins, crabs and more.

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Difficulty: Moderate
Length: 0.3 miles
Duration: 1-3 hours
Family Friendly

Overview:  The intertidal rocks at Natural Bridges State Beach are covered in life: sea stars, seaweeds, urchins, and crabs are just some of the ... more »

Tips:  2531 West Cliff Drive

Santa Cruz, CA 95060

(831) 423-4609

Open 8:00 to sunset

Wi-Fi access available with wireless enabled laptop... more »

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Points of Interest

1. Intertidal Landscape

As you walk towards the ocean, there are dozens of tidepools. Let's explore this intertidal landscape.

Intertidal inhabitants are tiny compared to us humans. Standing above the tidepools in our rubber boots, we are giants. We can look at the intertidal community from above, the same way we look at our own terrestrial landscape through the window of... More

2. Petrocelis

This sure looks like tar stuck to the rock. But it is actually seaweed! This is the encrusting phase of the seaweed called Turkish Washcloth (Mastocarpus papillatus). People used to think the encrusting phase and the upright phase were two separate species. The encrusting phase was called Petrocelis.

This is the upright phase of Turkish Washcloth ... More

3. Acorn and Gooseneck Barnacles

Barnacles are crustaceans that live in shells stuck to the rock. They are more closely related to shrimp than to other shell-dwelling animals, like mussels and clams.

As free-swimming larvae, these Acorn Barnacles settle on the rock, glue themselves down, and then build a shell around their shrimp-like bodies. You can see the bottom part of the... More

4. Intertidal ID - Orange

Is it an orange rock? Or a sponge? And what are those white circles? Could they be eggs?

Sea stars (Pisaster ochraceus) have tiny white spines on them called pedicellariae, which prevent other organisms from growing on the sea stars' skin.

The sea star can move slowly, using its little tube feet. The feet use suction to stick to the rock. The sea... More

5. Mussels

These California mussels (Mytilus californianus) are tightly packed in this mussel bed. They stick to the rock using bissel threads – thin, super-strong threads that the mussels produce. Mussels can actually move themselves, very slowly, by putting down new bissel threads and pulling up the old ones.

Space is limited in the intertidal, and there ... More

6. Intertidal ID - tentacles

What do you think this is? A plant? An animal? Octopus legs? Tentacles?

Sea anemones, like this Giant Green Anemone (Anthopleura xanthogrammica), are animals, not plants. They are Cnidarians, related to corals and jellyfish. The green color in the center of the Giant Green Anemone comes from symbiotic algae. Notice that the tentacles of this... More

7. Nudibranch

Nudibranchs are gastropod mollusks - they're related to snails and
slugs. Unlike snails, they have no shell. The word nudibranch means
"naked gills." The gills are those feathery-looking things on the nudibranch's back. These outgrowths of their bodies are called cerata - which means "horn." Nudibranchs breathe through the cerata.

The Sea... More

8. Seaweeds in the Surf

Looking out from the rocks towards the ocean, there is a tangle of seaweeds. The long skinny seaweed seen here is called Feather Boa Kelp (Egregia menziesii).

Here's a close-up of Feather Boa Kelp's "feathers." They are interspersed along the stipe with little balloon-like structures called pneumatocysts, which keep the algae floating at the... More

9. Red Algae

There are three taxonomic groups of seaweed: red, green and brown. It is easy to see that this one is a red.

Do you want tuna with that? This seaweed is called Nori (Porphyra spp.), and is pressed into thin sheets that wrap up sushi. It looks green in color, but taxonomically Nori is in the red group.

The blades of Splendid Iridescent Seaweed ... More

10. Intertidal ID - Snail Trails

What do you think created this pattern? These are snail trails – the olive-green stuff is algae, an the snails have grazed a trail, scraping algae off the rock with their mouthparts.

This Turban snail (Tegula funebralis) lives in the mid-intertidal, and has a black shell. Lower in the intertidal, it gives way to its relative (Tegula brunnea),... More

11. Honeycomb Homes

What is this honeycomb of sand?

The Sandcastle Worms (Phragmatopoma californica) are polychaetes – segmented worms with little bristles on them. You can see the bristles of these lavender-colored worms as they poke out of their sand tubes to feed. Each worm is genetically distinct (they are not colonial organisms). When big waves break apart the... More

12. Intertidal ID - Purple Spikes

What are these little purple feet?

Sea urchins, like this Purple Sea Urchin (Strongylocentrotus purpuratus), are echinoderms, related to Sea Stars. Urchins have spines and tube feet. They use the tube feet to move around, and also to breathe!

The mouth of the sea urchin is in the center. It is surrounded by five plates, which look a bit like teeth. ... More