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Intertidal Adaptations
The intertidal environment is influenced by a variety of abiotic (physical and chemical) factors.
The area may be protected from wave action or highly exposed to the force of crashing waves.
Organisms living here must have adaptations that prevent them from being washed away or smashed
against the rocks. The type of substratum may be sandy, muddy, or rocky. Different organisms will
inhabit each of these environments. Another important variable found in the intertidal is exposure.
As the tide recedes, part of the habitat will be exposed to air. The highest part of the intertidal will be
exposed for the longest period of time.
Rocky intertidal areas, such as the one we will be visiting, have pools of water that are left
behind as the tide goes out. These tidepools act as refuges for marine animals. The longer these
tidepools are isolated from the ocean, the more their temperature and salinity may fluctuate. On a
hot sunny day, the water may get quite warm. As water evaporates, it will get saltier, too. On a rainy
day, the fresh rainwater may dilute the tidepool, reducing salinity.
Types of Shore Habitats:
Protected Outer Coast – The semi-sheltered coast and open bays where the force of the surf is
somewhat dissipated before it can crush the most delicate forms. Such shores, which provide rich
collections, are generally concave, and characteristically are protected by a headland or a close-lying
island. Todos Santos Bay, Laguna, Santa Barbara, much of Monterey Bay, also Half Moon Bay, and
Point Arena are good examples. The substrate may be rocky or sandy.
Open Coast – Entirely unprotected, surf-swept shores, while by no means as rich in animals as
the partially protected shores of Division I, support a distinctive and characteristic assemblage of
animals that either require surf or have learned to tolerate it. This type of shore is generally convex,
varying from bold headlands to gently outsweeping stretches, and there will be fairly deep water
close offshore. Obviously there are no muddy shores in this division; so again we have only rocky or
sandy substrates.
Bay and Estuary – Animals of the sloughs, enclosed bays, sounds, and estuaries, where the
rise and fall of the tides is not complicated by surf, enjoy the ultimate in wave protection and
commonly differ in species from the animals inhabiting the open coast and the protected outer coast.
The shores embraced in this division are sharply concave; that is, they have great protected area with
a relatively small and often indirect opening to the sea. San Quintin Bay in Lower California is an
example, and moving northward we find other such areas in San Diego, Newport, Morro, San
Francisco, Tomales, and Coos bays, and in Elkhorn Slough along the Monterey Bay. This time we
have a greater variety of types of shore, including rocky shores, sand flats found in quiet waterways
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