Temporary Closure of Waters Around Alcatraz Island
From 7/3 to 9/22 a 500’ marine buffer zone is in effect, closing the perimeter of Alcatraz Island to all private vessels to protect nesting seabirds during America's Cup racing. Tours to Alcatraz continue as usual during the races. More »
Muir Beach (but not nearby Muir Woods) closed July 8-November 2013, but local businesses are open
Though Muir Beach is closed from July 8-November 2013 due to construction, the PELICAN INN IS OPEN. Restrooms and parking are not available at Muir Beach. Pacific Way is closed except to residents. Check back for updates or call (415)561-3054. More »
CAUTION: Post Storm Damage to Coastal Trail
The Presidio Coastal Trail segment just north of the Pacific Overlook and adjacent to Lincoln Blvd remains CLOSED indefinitely. We have posted signage to alert bicyclists and hikers and with information for safe trail alternatives. More »
Intertidal and Subtidal Zones
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?
Even if California and the West gets more rainfall with global warming, earlier snow melt and hotter summers will likely produce more drought stress, increasing susceptibility to pathogens and invasive species.