 Tide Pools
"It is advisable to look from the tide pool to the stars and then back to the tide pool again."
—John Steinbeck
The Log from the Sea of Cortez (1951)
The gravitational pull of the moon and the sun causes tides on the earth. The moon, which is closer but smaller than the sun, is responsible for a little more than half of the earth's tidal energy. During a tidal cycle (about 25 hours), various places on the earth's surface experience one or two high and two low tides.
Tide pools form in rocky beach outcroppings and provide a home for hardy organisms. Inhabitants must be able to cope with a constantly changing environment—fluctuations in water temperature, salinity, and oxygen content—and other difficulties. During low tide, barnacles are exposed to the sun and predators. Waves crashing on rocks threaten to dislodge mussels and draw them out to sea.
 Although organisms here must struggle to survive—
avoid getting washed away into the ocean, drying up in the sun, getting eaten—they depend on the tide pool's constant changes for food.
Tide pool zones, from shallow to deep:
spray/splash zone—Lichens and barnacles live in this region, which is flooded only by the highest tides and storm waves. Some lichens grow less than 1 millimeter per year, so they require stability and are vulnerable to pollution.
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high tide zone—Organisms here must survive rough waves and long exposure to air. Algae protect small creatures from the sun. Mollusks such as limpets and mussels attach themselves to the rocks. Hermit crabs, which make homes for themselves in abandoned shells, also live here.
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mid-tide zone—Often covered and uncovered twice a day by the tides, animals in this region have adapted to surviving in and out of sea water. When the tide goes out, anemones close up and mussels close their shells to keep in moisture. They open when the tide returns with food. Some sea stars can be exposed to air for up to 50 hours.
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low tide zone—Because the low-tide zone is usually covered by water, organisms here are not as sturdy and cannot tolerate much exposure to the air or sun. This stable environment has the greatest diversity of life of all the zones. Seaweeds provide shelter for many animals, including crabs, shrimp, and small fish. Sea slugs and urchins are more fragile than organisms in other zones. |
Sea slugs, anemones, limpets, sea stars, urchins, crabs—all of their colors and textures provide hours of viewing pleasure. If you plan to visit a tide pool, bring a camera or a drawing pad.
Tide pools can be found in many national parks, including:
Acadia National Park, Maine
Cabrillo National Monument, California
Cape Cod National Seashore, Massachusetts
Channel Islands, California
Olympic National Park, Washington
Redwood National Park, California
San Juan Island National Historical Park, Washington
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Be Careful |
| For the animals' safety:
 Look with your eyes, not your hands.
Do not pry animals such as starfish and mussels off of rocks. You could injure or kill them. Do not touch birds or mammals.
Seal pups can be found resting on rocks and beaches while their mothers eat offshore. Seabirds use rocks to lay their eggs on and to raise their young. You might want to get a close look, but mothers can get very protective and aggressive.<
Watch where you step—tidepool organisms are fragile. Even barnacles, which look sturdy, are damaged by being walked on.
Some animals use seaweed or rocks as protection from predators or the sun. If you move anything, gently replace it exactly as you found it.
For your safety:
 Rocks and algae can be slippery—walk carefully and wear shoes or boots with good traction.
Do not visit tidepools alone.
You might get wet, so wear appropriate clothing.
Tides can be very dangerous. Start your visit at least one hour before low tide and keep an eye on the tide. | |
