Multimedia Gallery
Marine Life of California's Rocky Shores (Image 20)
A California mussel (Mytilus californianus) clump. Mussels will grow on top of each other and on other species--resulting in interesting mussel clumps that are themselves a habitat harboring over 100 species of marine organisms. M. californianus live in the High Tide Zone starting at about five feet above sea level (see "More about this Series" below, to learn more about the zones).
At high tide, mussels open their shells just a crack to feed, which allows them to circulate 2 to 3 quarts of seawater through their shells each hour--mucus on their gills traps plankton for their food. When there is a lot of plankton, mussels can grow up to three inches each year and will overgrow most other species. However, although they dominate the area between 2.5 and 5 feet above sea level, on the coast of Santa Barbara, Calif., they rarely get a chance to live lower in the intertidal because their main predator--the sea star, consumes them.
Studies by scientists who removed sea stars from rocky intertidal areas show that mussels will prevail all the way to 20 feet below sea level as giant clumps, if left unchecked by their natural predator. Other factors also affect them, like big waves tearing off clumps that get too large or parasites, but it is the sea star that has the most influence. [Image 20 in a series. See Image 21.]
More about this Series
This series of images examines the various marine life that can be found in the different sea levels, or zones, of the rocky shores of the California coast. The images were photographed by Genevieve (Genny) Anderson of the biological sciences department, Santa Barbara City College, as part of her ongoing research on the subject.
Rocky shores provide a stable substrate for plant and animal life or organisms, as opposed to sandy beaches where the substrate (sand) is constantly moving. When the tide goes out then the influences of the air and weather (sun, rain, snow) begin to play important roles--more with the higher zones.
At any tide level on a rocky shore, a pool of water--called tidepools--can be left with the receding tide. These pools provide welcome ocean water for marine life left high and dry with a receding tide. The pools highest in the intertidal may become very hot due to the sun which may not be comfortable for some species. The pools closest to the low tide have the least influence from the air and weather and thus the greatest variety of marine life. These tidepools often mirror what is actually subtidal (below the lowest low tide, as opposed to intertidal which is between the tides). As the water goes down, most of the ocean creatures go out with it, but some can't move and are left on rocks. These creatures must be adapted to withstand not only the dryness of their area, but waves, storms, wind and rain. It is their ability to withstand dryness, and their interactions with each other (eating, being eaten, competing for space, and reproducing) that determine who dominates within the rocky intertidal areas.
In examining the marine life of the exposed rocky surfaces of California's shores, it is easiest to look at these rocky surfaces where they live in "zones." Above five feet, the surface is covered only by the highest high tide and thus dry three-quarters of the day. This is called the "Splash" Zone. Then, between five feet and two and a half feet, the surface is covered alternately by both high tides so it is dry between the high tides--about half a day. This band is called the "High Tide" Zone. Between sea level and two and a half feet the rocks are only left dry at the low, low tide. This area is thus dry only a quarter of each average day and called the "Mid Tide" Zone. Then there is what we call the "Low Tide" Zone, the area below sea level that is exposed for only a few hours every few weeks at special "minus" tides (remember, zero sea level is the average of the low, low tides).
To learn more about Genevieve (Genny) Anderson's research on marine life along California's rocky shores, visit her Web page, "California Tidepools (Rocky Shores)." Anderson, who has been a teacher of marine biology and biological oceanography at Santa Barbara City College for over 30 years, has other interesting lesson plans and lecture material available on her website, Here.
Credit: Genny Anderson, Santa Barbara City College
Images and other media in the National Science Foundation Multimedia Gallery are available for use in print and electronic material by NSF employees, members of the media, university staff, teachers and the general public. All media in the gallery are intended for personal, educational and nonprofit/non-commercial use only.
Images credited to the National Science Foundation, a federal agency, are in the public domain. The images were created by employees of the United States Government as part of their official duties or prepared by contractors as "works for hire" for NSF. You may freely use NSF-credited images and, at your discretion, credit NSF with a "Courtesy: National Science Foundation" notation.
Additional information about general usage can be found in Conditions.
Also Available:
Download the high-resolution JPG version of the image. (283 KB)
Use your mouse to right-click (Mac users may need to Ctrl-click) the link above and choose the option that will save the file or target to your computer.