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Marine life of California’s rocky shores
Posted by Bridget in Biology, Life
Genny Anderson, Santa Barbara City College
The various shades of green in this sea anemone come from a combination of the natural colour of the anemone and from green-coloured symbiotic algae that grow in its tissues. Anemones found under rocks or in the shade have little symbiotic algae so are generally very pale. The various striping on their tentacles is genetic and serves to show how each is unique (unlike the clones of aggregating anemones where each clone member is identical).
This image shows just one of the many species that live in the higher zones of the rocky California coast.
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 the influences of the air and weather (sun, rain, snow) begin to play important roles – more so in the case of the higher zones.
At any tide level on a rocky shore, a pool of water – called tide pools – 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, and that might 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 tide pools 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 cannot 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.
Living ‘in the zone’
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 1.5m, 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 1.5m and 750mm, 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 750mm, 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).
A starburst anemone coloured green from symbiotic algae.
Source: National Science Foundation
