At the foot of Temescal Canyon, within earshot of the roaring traffic on the Pacific Coast Highway, a littoral ecosystem emerges with the twice daily tides. In the intertidal zone, on a boulder-strewn jetty constructed perpendicular to the shore to slow the beach erosion, limpets are busy growing alongside two species of barnacles and mussels. A recent visit during low tide was quite rewarding.
Based on this Cal State Fullerton guide, I think this is a shield limpet, a species of sea snail. As this limpet was on an ocean-facing boulder at Will Rogers State Beach, it has faced powerful waves during this winter’s high tides and storms. Its range in the Eastern Pacific Ocean runs from the Aleutian Islands to Baja, Mexico. Limpets’ herbivorous diets consist of seaweed and algae. In turn they are eaten by seastars and black oyster catchers. Limpets move around minimally on their home scar, and only when underwater or splashed by the waves. To keep from drying out between high tides, they store a measure of seawater under their shells.
Hitching a ride on top of the mussels in the picture below are buckshot barnacles. Per Genevieve Anderson at Santa Barbara City College, “All barnacles are filter feeders – extending feathery legs into the water at high tide to comb plankton from the water. These ‘furry’ legs then kick the plankton down into the volcano-shaped shell to the mouth area of the barnacle.” Some of the barnacles in this photograph have open, volcano-like tops; they’re dead. Those with intact tops are smaller, younger and a little harder to see.
Gooseneck barnacles, featured in this last photo, are often seen near mussels. As filter feeders, they grow in communities or “hummocks” and can reach 20 years of age. The shells in this photograph look pitted and dull, perhaps a factor of the recent storms on the Southern California coast. Opportunistic about their real estate options, gooseneck barnacles are also found on hulls of ships, and marine infrastructure (think piers and pilings).
These mussels are growing vigorously, covering much of the oceanside of the intertidal boulders. The decline in or lack of seastars (their primary predator) is a likely factor in their large numbers. They have byssal threads which resemble the golden tassels inside a corn cob. At the end the threads are feet which anchor each mussel to its home with a glue-like liquid.
Not bad for an afternoon walk at the beach!
Mashabu 