Pacific Coast Tide Pool Animals
The Low Tide World of Anemones, Sea Urchins, Starfish, Seashells
May 31, 2008
Low tide on the Pacific Coast uncovers a magical world of little sea creatures: animals that look like flowers or plump round pincushions; crabs that carry snail shells on their backs, orange starfish; ancient armored chitons; and oddly shaped sea shells, mostly occupied.
The rocky intertidal zone – the portion of beach between high and low tide – is a tough place to live. Alternately covered by the sea and exposed to rain and the drying sun, creatures must also withstand the force of inrushing tides and the coast’s fierce salt winds.
Nevertheless, the array of animals that thrive here is abundant and varied.
Anemones, Starfish and Mussels
Green anemones wave tentacles like flower petals in pools of sea water, holding tight to the rocks where they remain stationary. Nearby, thorny purple sea urchins graze the tidepools.
Starfish, or “sea stars,” are a favorite of children exploring the rocky intertidal zone. They move slowly across the rocks on suction feet, which they also use to pry open mussels for supper. Pacific starfish range from bright orange to purple.
Mussels are tough shellfish that attach themselves to rocks, sometimes in large colonies. Blue mussels, with deep blue or black shells, are common in Pacific waters, as are the slightly larger California mussels. California mussels have bright orange flesh when cracked open.
Colorful Nudibranches, Crabs and Chitons
Some animals move freely through the tidepools. One type carries the common name “sea slug,” although they can be so beautifully colored the name seems an insult. Nudibranch is the formal name for sea slugs, whose soft bodies range from lemon yellow to white and bright red, often with stripes, dots or borders. They come in all shapes from elongated to round, flat or plump. Some have feelers on their backs that sway gracefully as they move through the water.
Tiny crabs scurry along the bottom of tidepools or hide in crevices or under rocks. One crab, the hermit crab, can be seen dragging a snail shell on its back.
Chitons are flattened, oval animals with overlapping plates for armor. They have a prehistoric look. They cling to the rocks where they scrape off algae for food. While most are small, the giant gumboot chiton can grow to almost a foot and hides its plates beneath a thick reddish-brown outer coating.
Limpets, Sponges and Hydroids
Limpets are a common intertidal dweller, easily identified by their cone-shaped shells. There are several species, some preferring the ocean-side edges of the low-tide line, others surviving high on rocks where only the salty sea splash reaches them. Their tiny, “Chinese hat” shells often wash up all along the wet beach sand.
Some animals look more like moss or the branches of tiny plants. Encrusting sponges form cushions of red and purple on the rocks. Hydroids often grow in clusters like bushes with waving tentacles or on stems with branches resembling fans.
Tiny fish seen swimming in tidepools are probably sculpins. There are several species, but most have slender bodies and broad heads. Colors range from brown to red, often mottled.
When exploring tidepools, remember that removing animals from their natural location usually means death for them. Life here depends on an exacting balance of tidal reach and chemistry within each stage of the intertidal zone.
Wet intertidal rocks are slippery. Falls can result in cuts and scrapes from sharp rocks and shells. When exploring, remember to walk carefully to avoid falls and to avoid damaging the delicate marine life.
Part of what makes tidepools slippery is the array of plants that inhabit this area. Some of these plants are discussed in the related article Pacific Tidepool Seaweed & Algae.
Locations for viewing tidepools are outlined in the article North and Central Oregon Coast Tidepool Sites.
Below is a selection of field guide to help in identifying the varied life present. Below is a selection of useful guides.
References:
Tidepool & Reef: Marinelife Guide to the Pacific Northwest Coast, byRick M. Harbo (Hancock House Publishers Ltd.)
Exploring Pacific Coast Tidepools, by Vinson Brown (Naturegraph Publishers)
Between Pacific Tides, by Edward Rickets and Jack Calvin (Stanford University Press). This is a classic of marine biology with more than 600 pages.
Seashore Life of the Northern Pacific Coast: An Illustrated Guide to Northern California, Oregon, Washington, and British Columbia, by Eugene N. Kozloff (University of Washington Press). This is a comprehensive guide to intertidal life.
