Photograph by Brandon Cole

Covered and uncovered by tides each day, violet coralline algae, sea stars in orange and lavender, spiny purple sea urchins, and green sea anemones have adapted to lives of constant change.

Photograph by David Liittschwager

Tidal Zone Treasures The rocks and pools of the intertidal zone are home to an array of creatures fancifully named for their shapes and colors.
From top First row: red abalone, Cockerell’s dorid, ringed nudibranch, variegate amphissa, grainyhand hermit crab, ochre sea star, cabezon Second row: red octopus, opalescent nudibranch, mermaid’s cup, smooth iridescent seaweed, San Diego lamellaria, purple sea urchin, hammerhead doto, leather star Third row: red rock crab, calico sculpin, colorful dendronotus, stubby frond nudibranch, rough limpet, calico sculpin Fourth row: red sponge nudibranch, chink snail, woody chiton, nereid worm, syllid polychaete, peanut worm, brown turban snail, red sea fern Fifth row: shield limpet, sea clown nudibranch, red sea fan, monkeyface prickleback, bat star, green rope, red rock crab, flat porcelain crab Sixth row: splendid iridescent seaweed, Farlow’s soft seaweed, blood star, six-armed star, Pacific sea comb, glycerid worm, sea palm, red gunnel, tinted wentletrap, surf grass, red sea cucumber

Photograph by David Liittschwager

Algae share space with the creatures.

Photograph by David Liittschwager

A red abalone

Photograph by David Liittschwager

Some creatures are easy to spot, but it takes a sharp eye to notice some small sea spider species, less than half an inch long (see following two photos).

Photograph by David Liittschwager

A species of sea spider

Photograph by David Liittschwager

A species of sea spider

Photograph by David Liittschwager

The tide’s ebb and flow transforms a seascape. The Pacific Coast at Fitzgerald Marine Reserve, south of San Francisco, is covered at high tide.

Photograph by David Liittschwager

At low tide on the coast, rocks and pools emerge, teeming with life (see previous image of tidal zone treasures).

Photograph by David Liittschwager

Bright green sea grass and shiny kelp hold fast to rocks as waves crash over them along northern California’s Bodega Head.

Photograph by David Liittschwager

Residents of California’s intertidal zone range in size from one-quarter inch to one and a half inches.
A shrimp

Photograph by David Liittschwager

A sea anemone with two young

Photograph by David Liittschwager

A feather duster worm (its bundle of tentacles breathes and catches food)

Photograph by David Liittschwager

A crustacean with seven pairs of legs

Photograph by David Liittschwager

A sea star displaying tube feet, used for locomotion

Photograph by David Liittschwager

A type of mollusk called a lined chiton

Photograph by David Liittschwager

A nudibranch, or sea slug

Photograph by David Liittschwager

A cluster of fish eggs

Photograph by David Liittschwager

The crustacean shown here has evolved a shape and color to blend in with the blades of sea grass where it lives.

Photograph by David Liittschwager

Gooseneck barnacles (top) occupy rock faces in the middle intertidal zone, while sea anemones (bottom) thrive on the low shore. Predatory sea stars move actively in between.

Photograph by David Liittschwager

The deepest parts of tidal pools nurse strange creatures like this California stickyhydroid (Eudendrium californicum), only a few inches long. Although it resembles a plant, those pink “blossoms” are jellyfish-like animals that breed and collect food for the colonial organism. A small crustacean (Caprella kennerlyi) has attached itself near the hydroid’s tip.

Photograph by David Liittschwager

A decorator crab disguises itself by hooking on bits of algae.

Photograph by David Liittschwager

The penpoint gunnel comes in colors from reddish to green to brown, depending on its surroundings. If the camouflage works, intertidal zone predators won't notice these potential meals.

Photograph by David Liittschwager

A seaside bench at California’s Fitzgerald Marine Reserve offers a relaxing vantage point for watching the rise and retreat of Pacific Ocean tides.

Photograph by David Liittschwager

Marine biologist Sarah Ann Thompson searches for invertebrates living amid the carpet of kelp on the rocks at California’s Bodega Head. Her thick overalls and sturdy knee pads offer protection from the sharp shells of mussels and barnacles.

Photograph by David Liittschwager

Giant green sea anemones and purple sea urchins remain mostly submerged when the tide goes out at northern California’s Van Damme State Park, but organisms higher in the intertidal zone—like this sea star (Pisaster ochraceus), whose soft body stiffens protectively when out of the water—will be more exposed.