The Magic of Tidepool Animals

Mar 10

5 min read

Person in a winter coat and boots bends over rocky, algae-covered shoreline. Ocean waves crash in the background under a clear blue sky.

What are tides?

Full moon rising over silhouetted trees on a hill against a dark night sky, creating a serene and mystical atmosphere.

Tides are created when the moon's gravity pulls at the Earth changing the Earth's shape slightly into a football - so that the equator is elongated and the poles are shortened. The water on Earth then bulges at the sides, with the strongest pull being toward the moon.

The sun can also affect tides even though it is much further away than the moon. Two times a month the Earth, Sun and Moon are aligned and create very high and very low tides - called spring tides.

About one week after a spring tide, when the Sun and Moon are at right angles and not aligned the Sun's pull lessens the Moon's and the result is moderate tides - these are called neap tides.

There are also King tides which are the most extreme of the high and low tides. They occur 2-8 times a year and only when the alignment of the Sun, Moon and Earth happen during the moon's closest orbit to Earth. This is the BEST time to go tidepooling - so keep track with your local tidal charts to know when they are coming!

Rocky shoreline at low tide with tide pools and seaweed under a clear blue sky. People are exploring the beach in the distance. — Pillar Point, Moss Landing - King Tide

Intertidal Animals

The rise and fall of the ocean has led to some truly interesting evolutionary adaptations of tidepool animals. Any animal living in the intertidal - which is the area of the coast that is between high and low tides - has to overcome unique circumstances. Twice a day they are exposed to sun, air, predators, and the battering of waves. This means that animals that primarily live underwater had to evolve ways to survive these exposures.

Imagine if twice a day we had to live underwater where things come to try and eat us! We would have had to evolve a way to breathe, a way to hide or defend, and a way to keep warm!

If you are lucky enough to live in an area with tidepooling than you have likely encountered some of the animals there. You may have not even known they were animals at all! Many of them don't have recognizable faces, legs, or even eyes. They have challenged our ideas of what an animal is supposed to be.

The main animals you might find in tidepools are:

Mollusks - snails, abalone, limpets, chitons, mussels, octopuses and nudibranchs
Arthropods - crustaceans! crabs, lobsters, barnacles
Echinoderms - sea stars, urchins, sea cucumbers
Cnidarians - anemones, jellyfish (which you would only find washed up during low tide)
Fish

Evolutionary Adaptations of Intertidal Animals

Mollusks - snails, abalone, limpets, chitons, mussels, octopuses and nudibranchs
Chiton and Mussels

Rocky tide pool with clusters of black mussels and orange starfish. Ocean waves and a cloudy sky create a serene coastal scene. — A bed of mussels, anemones and sea stars

With the exception of nudibranchs (sea slugs) and octopuses the characteristics of Mollusks are a hard shell and a large singular muscular foot that attaches to rocks. The shell protects them from drying out when exposed to air and sun, protects their mushy internal organs from the battering waves and also deters predation.

Instead of mouths many of them have something called a radula, and the less complex ones have simple light sensing spots instead of the eyes we are familiar with.

Black and white illustration of a radula, proboscis, and mouth opening, labeled. Star-shaped patterns cover the radula, suggestive of texture. — Diagram of a radula - Photo Courtesy of NCSU

Nudibranchs have evolved even more specialized ways of surviving by taking toxins from their food and using them to deter predators. They eat jellyfish, anemones and coral and take the stinging cells to use for themselves. Nudibranchs don't have a shell to protect them from drying out, so they often live a bit deeper in the intertidal where it won't be exposed to long durations of air and sun, and you can often find them hiding under sea grass.

A small, vibrant brown and white sea slug with feathery appendages rests gently on a person's palm, set against a soft pink background. — Opalescent Nudibranch

Bright orange sea slug glides over dark, algae-filled water with green strands, creating a vivid contrast in a tranquil tidal pool. — Yellow-Gilled Sea Goddess

Close-up of fingers holding a small, pink sea slug with a dark stem; blurred rocky background. The mood is delicate and serene. — Hopkins Rose Nudibranch

A small reddish-brown octopus rests in a person's hand, with water glistening. The mood is serene, background hints at a rocky shore. — Red Octopus

Arthropods - crabs, lobsters, barnacles

Close-up of a red crab with white spots and barnacles on its shell, nestled among rocks and seaweed in a sunlit tide pool. — Rock Crab

The characteristics of these tidepool animals include a hard exoskeleton to protect from exposure and predation, and segmented bodies for mobility. They can breathe underwater because they have gills that take oxygen from the water, and can survive out of water by getting oxygen from moist air if they keep their gills wet, either by storing moisture or blowing bubbles.

A crab on a weathered, grayish rock by the seashore, with blurred tide pools and ocean in the background, creating a serene mood. — Crab blowing bubbles

Echinoderms - sea stars, urchins, sea cucumbers

Hand holding a vivid red starfish against a blurred background of green seaweed and water, creating a natural and serene atmosphere. — Leather Sea Star

These intertidal animals often have spiny skin, in the case of urchins they are much like long toothpicks! And they have many little tube feet that they use to move (slowly) around the seafloor, attach to rocks, and even hunt and pry open food. Sea stars are actually voracious predators! They lack a brain but have a superpower called regeneration where they can grow back lost arms. The spiny skin helps them from drying out and deters predators from eating them, although urchins make a delicious snack for sea otters!

Purple starfish with white bumps on a rocky shore, surrounded by green seaweed under bright sunlight. — Ochre Sea Star

Red starfish on dark, glossy seaweed with small shells. The setting is coastal, with wet textures and a natural marine vibe. — Bat Star

Fnside of a Purple Sea Urchin - you can see what is called the Aristotle's Lantern which is a basically a jaw found in urchins and sand dollars

Cniderians - anemones and jellies

One of the most common animals to see in tidepools are anemones. They have stinging cells that are venomous that can paralyze their prey. Though they are sedentary they use tentacles to paralyze and catch fish, plankton, shrimp, crabs, etc.

In order to not dry out when exposed to air they can close up and tuck themselves in, or cover themselves in small rocks and debris.

Instead of a regular mouth they have a digestive cavity that breaks down their prey with enzymes.

Most sea anemones you find off the California coast can't hurt humans, but if you touch one and forget to wash your hands then touch your face you might feel stinging on your

lips!

Orange starfish and green sea anemone in a rocky tide pool. Clear water reveals seaweed, rocks, and pinkish algae in a serene setting. — Giant Green Anemone next to a Ochre Sea Star

Colorful tide pool with green sea anemones, brown seaweed, and textured rocks. The scene is vibrant with aquatic life. — Sunburst Anemones closed up and exposed to air

Sea anemone with green tentacles in a rocky tide pool, surrounded by dark red algae and small snails on a speckled, textured surface. — Sunburst Anemone

Blue jellyfish on a sandy beach, surrounded by scattered rocks. Overcast sky and ocean waves in the background. Calm, muted tones. — Washed up By-the-Wind Sailor - you can find loads of them washed up in winter storms

Fish

Tidepool fish are often hard to see, they dart around very quickly and use clever camouflage to blend in. Some of the more common species are fluffy and mossy sculpins, and monkeyface pricklebacks. The tidepools often serve as little fish nurseries for the younger fish to protect them from large predators found in the deeper ocean, and tidepools also provide a lot of food for the young fish.

Sculpins can survive out of water for short periods, and in low-oxygen small tidepools.

In other parts of the world, like Hawaii, there are even tidepool fish that can jump from pool to pool like the pāoʻo (blenny).

Green fish camouflaged against a rocky, orange-brown seafloor. The fish has intricate patterns and is near a small yellow coral. — Fluffy Sculpin - Photo courtesy of Ron's Critter of the Day

Tidepool Safety

Never turn your back on the ocean. The coast is unpredictable, sneaker waves can come out of nowhere!
Don't go alone, and if you do make sure someone knows where you are and when you will be back.
Low and slow - There is a lot to see and the slower you go the more you will notice.
Walk carefully - rocks can be very slick, and tidal areas are often very uneven. Wear waterproof shoes with good tread, or wetsuit/water shoes.
Don't take anything. They may look like rocks or empty shells, but even some of those have small colonies of animals living on them.