TidepoolsOn rocky shores where boulders are relatively stable, cavities fill with seawater, forming tidepools. These pools, which range from cup-sized depressions to reservoirs the size of small ponds, can form at any level of the intertidal zone; at the lowest level, life is more abundant and diverse, a microcosm of life below the tide level. For non-divers, tidepools offer a look at the marine world in miniature.
A Tidepool - As the large drawing on the right shows, a tidepool can encompass multiple levels of zonation, and thus can be packed with fascinating creatures who make their livings in diverse ways. Some are filter feeders: Mussels and clams take in and expel water, holding onto the nutrients. Others are herbivores. The giant keyhole limpet, which feeds on algae, uses its tonguelike radula to scrape the rocks, almost like a child licking peanut butter from the roof of his mouth.
Still others prey on other animals, using various strategies to hunt them down. Starfish, such as the blood star, creep slowly around the tidepool. An ochre sea star lies prone across a bed of mussels. Using its feet to open them, the sea star inserts its stomach into the shells and consumes the flesh.
The sculpin, which is the most commonly found fish in the tidepool, dashes here and there around the pool, ambushing prey such as small crabs. Its mottled coloration camouflages it from its unsuspecting victims.
Occasionally, lucky tidepoolers encounter an octopus, whose menacing appearance belies its shy nature. Slinking about the pool, this quick,change artist deftly alters its color from red to white and back again as its chases its prey. Putting one or more of its eight arms to use, the octopus may pry open a clam or crab, or it may avoid a fight entirely by injecting a paralyzing venom into the animal's,shell. Octopuses are so good at finding hiding places that they are difficult to spot.
Many of the animals that live in the intertidal zone are often confused with flora, especially those sessile animals that have been christened in honor of plants, such as the anemone. The tiny bryozoan, often called a moss animal," has a distinctly plantlike appearance and is often described as "leafy." Some species form delicate white encrustations on moist rocks. Unlike plants, the bryozoan cannot manufacture its own food. It uses feathery extensions to sift phytoplankton from the water.
Plant life can be abundant in the lower zones of the intertidal. Hundreds of species of marine algae, or seaweed, grow in California, including edible sea lettuce, which is most prevalent in the fall and spring when the annual pattern of upwelling provides high levels of nutrients. One of the most conspicuous types of red alga is Gigartina, which is referred to as the Turkish towel because of its plush surface.
Along the meandering coastline of the islands within the sanctuary, steep rocky cliffs are broken by occasional pockets of sandy beach area. Sanctuary boundaries begin at mean high tide and overlap the jurisdictional boundaries of the National Park system, which extend to one mile off-shore. Added to this layer of protection are California Department of Fish and Game regulations that prohibit collecting organisms from the high tide line to 1,000 feet from shore. Certain species, such as abalone, clams and mussels, may be collected with a valid fishing license, which is required in all coastal waters. A visit to the beach should not be viewed as a chance to expand your shell collection. Look, touch, but don't remove. And if you overturn a rock, remember to replace it to its original position so that the animals that call it home can continue to do so.