Intertidal



	Dad explains to me that life in the interdial zone isn't easy. In fact, this is a pretty tough neighborhood! Low tide may expose marine plants and animals to air, sometimes for hours at a time. On a hot summer day, exposed intertidal creatures may be affected by the sun. FREEZING In winter, the opposite can happen if temperatures fall below freezing on the coast, just when intertidal residents are uncovered by low water. POUNDING WATER When storm-driven waves hit the shore with sledgehammer blows, residents of the open coast must hang on for dear life. CHANGES IN SALINITY Marine animals trapped in tide pools can suffer a reduction in salinity, or salt content, when fresh water intrudes into the intertidal zone during heavy rains. Salinity can also increase to dangerous levels when water in tide pools evaporates under the hot sun.
	PREDATION Exposure at low tide makes marine animals vulnerable to predators such as seabirds and land mammals. If the intertidal zone is such a hazardous place, why do we see so much life when we visit rocky shores?

UPWELLING [ABOVE] Northerly winds blowing along the Pacific coast push surface water away from the shore. It's replaced by deep water rich in nutrients that rises to the sunlit surface where photosynthesis can take place. This fosters a rich growth of plankton, the base of the marine food web and a source of food for near-shore marine life.	ROCKY HABITATS The Pacific coast has miles of rocky shores, where cracks and crannies, surge channels and tide pools create a moist environment and provide plants and many species of marine animals with a stable grip on their chosen home. SUMMER FOG Often, intertidal dwellers are shielded from the summer sun by a thick blanket of Pacific coastal fog that keeps them from overheating and drying out.
	ADAPTATION [Below] Most important, plants and animals, through natural selection, have developed adaptations that allow them to live in this difficult neighborhood. These special adaptations are quite varied. They may consist of shells that close like trap doors when the tide goes out. Or clinging feet with suction cups, or muscles that grip the rocks. Some animals can fold themselves up or disappear down a long tube, to await the return of high tide. Others literally tie themselves to the rocks with secreted fibers, to resist the force of moving water. Rubber necks and flexible stalks allow some intertidal residents to bend with the waves. Many have a tough skin, or impregnable armor to keep them moist and cool while exposed to air.

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