• View of the Golden Gate Bridge, taken from the Marin Headlands, looking towards San Francisco at sunrise.

    Golden Gate

    National Recreation Area California

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  • Tunnel Closure

    The Barry/Baker tunnel on Bunker Road will be closed for maintenance during the weeks of 6/2 and 6/9. The tunnel will be open on the weekends. Please use Conzelman Road instead. More »

  • Muir Beach Overlook closure

    The Muir Beach Overlook will be closed for Accessibility improvements and trail upgrades from June 2 through July 21. Alternate viewpoints are available along Highway 1 between there and Stinson Beach.

Intertidal and Subtidal Zones

Nature and Science

Sea stars hanging on at Fort Point

NPS photo

Halfway between the land and the sea, on flatter rocky shelves where waves break, is the intertidal zone. Intertidal zones of the California coast mainly encompass patchy tidepools. But in an urban park such as ours, life can also be found on the edges of rocky coves or rubble piled along piers. Although not well explored, there are also over 100 sea caves located in the park!

Rocky intertidal areas are primarily inhabited by marine algae and invertebrates (animals without backbones such as crustaceans, worms, mollusks, and sponges). The inhabitants of the intertidal zone are exposed to crashing waves and predation by ocean creatures during low tide. They filter feed for organic particles in the water, graze on algae, or prey on each other. Most of them have hard exoskeletons or shells to withstand the pounding surf, and are able to cement themsleves to the rocks. During high tide they are left exposed to the air and land predators. They must tough out this dry period, hiding under rocks and in small pools of water, closing their shells with small amounts of water inside, and waiting until the next tide begins to start the whole process over again.

Rocky intertidal areas, just like salt marshes, have distinct zonation. In the high splash zone which is only covered by very high tides look for limpets, barnacles, snails, shore crabs, and rock weed. In the middle zone which experiences two high and low tides daily look for mussels, anemones, ocher stars, and sea lettuce. In the lowest zones that are exposed only during a very low tide, look for sea urchins, bat stars, and even octopus!

Did You Know?

Photo of Western gull vocalizing.

Western gulls express themselves with at least twelve different vocalizations which may indicate agitation, identification, alarm and willingness to feed chicks or mate.