Our Window into the Marine World: Tidepools

Along the Path: A Young Person’s Guide to Exploring Nature

By Susan Rothrock Deo

Tidepools are one of my favorite marine habitats. From the comfort of land, without donning scuba equipment, we can start to explore the marine world. Tidepools are small depressions where sea water remains after the tide goes out. They are found on rocky shores in the intertidal zone (between low and high tides). Tides are caused by the moon’s gravitational pull: high tides on the near side and low tides on the opposite side of the earth. Learn more at https://scijinks.gov/tides/.

We have some great local tidepools. The best time to visit is at or near low tide. (Check online. Times change daily.)

Life in the intertidal zone offers advantages and disadvantages. Strong waves bring an abundance of nutrients, but organisms must hang on tight or shelter somehow. The sun warms the shallow water, a respite from the cold ocean, but it can dry out marine organisms, threatening their lives. Rapidly changing temperatures can also be challenging.

Always wet your hands before touching any tidepool creatures. A gentle, light touch (one or two fingers) is best. If you turn over any rocks, return them gently and re-cover any organisms you uncovered so they are protected from predators and sun.

A few interesting facts about some local organisms (see the link below for a chart with pictures):

·   Phylum Echinodermata. Individuals, like sea stars and sea urchins, can be divided into almost identical pie shaped pieces. Recently, a wasting disease has killed sea stars along the west coast. They are beginning to come back, so you might see some smaller ones. Sea urchin populations on the other hand, especially the red ones, are surging because sea stars are their major predators.

·   Phylum Cnidaria includes sea jellies and sea anemones. Sea anemones, which look like flowers, attach themselves to the substrate and use their tentacles to catch food swimming by. They stun it with their nematocysts (stinging cells) and move it to their (central) mouth to digest.

·   Phylum Molluska includes snails, limpets and clams, all with enclosing shells. Octopuses and sea hares, which have no shells, are the most intriguing to me. At the right time of year, you might find a baby octopus. Adults hide under rocks, their tentacles venturing out to explore. Sea hares look like large, shell-less snails. They eat algae and release a purple/pink colored “ink” into the water when threatened, similar to what octopuses do.

·   Phylum Arthropoda includes lobsters and crabs. My favorite are the hermit crabs. Because they cannot make their own shells, they must search for a larger “home” (often a discarded snail shell) whenever they outgrow one. If a snail shell is moving quickly around a tidepool—on legs—it’s a hermit crab!

·   Phylum Vertebrata (animals with backbones). Small fish live in the tidepools too.

·   Phylum Rhodophyta, Red algae. (Green and brown algae are in different Phyla.) Coralline algae has stiff red branches that look like coral. They can be found clinging to rocks or as broken white pieces (no longer alive) scattered around.

Check the tide charts, grab your water shoes and your species chart, and explore this amazing habitat!

Chart showing common Southern California tidepool species (from USC), including ones discussed above.

Some Local Tide Pools to Explore:

White Point Park, San Pedro

Cabrillo Beach Tide Pools, San Pedro

Pelican Cove, Rancho Palos Verdes

Abalone Cove Shoreline Park Tide Pools, Rancho Palos Verdes

Sacred Cove Beach (part of Abalone Cove Shoreline Park), Rancho Palos Verdes

Remember, the last two are state ecological preserves and taking of protected animals and marine life is prohibited. Here are rules for all tidepools:

%d bloggers like this: