28 - Tide Pools

WAYSIDE LAYOUT: Cream colored, vertically oriented panel with a dark banner running across the top. The banner reads “Golden Gate National Recreation Area” on the left and the National Park Service logo on the right. The content is in two columns. The first column has text then two images side by side below it. The second column has 3 images, each with text.  

FIRST COLUMN:  

TEXT: Tide Pools: Life in the tidal zone. Alcatraz’s tide pools, formed from both natural rock and rocky rubble thrown off the island during excavation projects, are habitat for more than 50 species of invertebrates and 80 species of algae. The water-filled depressions that remain among the rocks after the tide has receded make survival possible for sea stars, sea urchins, and other marine life that would otherwise dry up and die.  

In turn, intertidal residents – crabs, snails, shellfish, sea anemones, and seaweed, to name just a few – sustain western gulls, black oystercatchers, black turnstones, and many other water birds. These tide pools are an integral part of Alcatraz’s natural ecosystem, and one of the few intertidal habitats in the San Francisco Bay.  

DESCRIPTION #1: Colored photograph of a dark colored bird standing on a light grey rocky surface.  

CAPTION: Pigeon guillemot (Cepphus columba). Pigeon guillemots breed in crevices on cliffs around the island and can be seen delivering fish to young during the summer.  

DESCRIPTION #2: Colored image of a large bird on a rocky surface. The bird has a long, thin, dark colored beak and face, with a yellow head, a white neck and a grey colored body.  

CAPTION: Brown Pelican (Pelecanus occidentalis). Brown pelicans hunt food near the tide pools, as well as the bay’s open water, where they’ll dive from heights as great as 50 feet to catch fish they’ve spotted from the air. Alcatraz takes its name from the vast colony of seabirds – alcatraces, in Spanish – encountered by Don Juan Manual de Ayala, the island’s first European explorer, in 1775.  

SECOND COLUMN: 

DESCRIPTION #1: Colored photograph of the tide water and pools from above. The green water of the bay is at the top and meets the dark, brown and green rocky landscape in the middle of the image. The waves are crashing into the rocks and long tendrils of seaweed can be seen floating in the water.  

CAPTION: While it would be easy to perceive Alcatraz’s tide pools as the island’s outermost ring of life, they are in fact part of a seamless web of life that continues out into the bay and around the planet. They are a transition zone between terrestrial and aquatic habitats.  

DESCRIPTION #2: Colored photograph of a bright red anemone resting in a tide pool. The anemone is a circular shape, with long bright red fingerlike structures emanating from a dark colored center, similar to a sunflower. It is resting on top of light brown colored rocks, just below the surface of the water.  

CAPTION: Anemone in a tide pool. They may look peaceful at any given moment, but tide pools are actually very demanding environments. Only hardy species can withstand the constantly fluctuating conditions between high and low tides, and the brutal pounding of waves against the rocks.  

DESCRIPTION #3: Colored photograph of a sea star. The sea star takes up the entire image and is light in color, almost white. The surface of the sea star has small ridges, which makes it appear rough and rocky looking. It is surrounded by dark reddish algae.  

CAPTION: Sea star on algae covered in rocks. Algae are the most fundamental of all food sources here. These diverse aquatic plants feed copepods – 7500 species of minute shrimp-like crustaceans that form part of the bay’s plankton population. The copepods are eaten by fish and marine invertebrates, which are then eaten by numerous bird species.