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Now that the tide has reached its lowest level, we begin to
notice something rather peculiar about the steep rocky shore; it appears
to have different colored stripes running horizontally. The highest
band is yellow and orange; below that, it's dark gray, then white, then
black near the bottom. |
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The top floor is the Splash, or Spray Zone. The highest is the driest! Only the splash from waves at high tide moistens these rocks. Not many creatures can live here successfully. Black lichens, a combination of fungi and algae, form a thin coating on otherwise bare rock. Tiny black periwinkles, isopods and a few limpets that find shelter in cracks and crevices are the main life forms in this dry habitat. |
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Just below is the High Tide Zone, slightly more hospitable because it gets submerged during high water. A few small barnacles, some limpets (left) and a handful of algae species can make a living here. But it's still a hard life, thanks to pounding waves and long periods of exposure to air. |
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The next level down in this condominium is the Mid Tide Zone. It has many more residents than the floors above, because it stays wetter longer. Although this zone gets exposed by most low tides, it's covered by most high tides. We notice more seaweed, a variety of shellfish, and even some sea anemones. |
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Finally, right under our feet is the Low Tide Zone, the condominium's ground floor. It's packed with residents; in fact, in some places there's standing room only! That's because this zone stays moist. Even during the lowest tide, there are cracks and crannies, channels and tide pools where water remains. Here, plants and animals can comfortably await the returning tide. |
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But there's another thing about the rocky shore that often
determines where plants and animals choose to live. That's the shore itself.
Right now, we're walking over a sloping granite shelf. But our coasts are also composed of basalt and sandstone, sometimes a combination of all three. Animals like the sea urchin (left), prefer open coasts and are attracted to sandstone because they can carve cozy round holes in which to nestle when things get rough. |
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Shores exposed to the open sea get hammered by storm-driven
waves, especially in winter. The residents need some means of hanging
on. Protected coasts, like those of bays and harbors, are likely homes
for more vulnerable marine creatures. Some coasts are steep, while others, like the one we're visiting today, have broad, wave-cut platforms that step down gradually toward the sea, cradling numerous tide pools where life is abundant. So all these factors: • what a particular piece of shoreline is made of, • whether it's protected or exposed, • how it's shaped, and • which floor it occupies in the intertidal condominium, will determine who can survive there and who cannot. Return to the Tidal Zone |