Fish & Water - Sounds Wild
The Intertidal

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Intertidal

The tide is high and a scuba diver investigates a vertical rock wall about 20 feet high, covered with barnacles, mussels and marine life. Kelp reaches from the seafloor below to the surface. Just six hours later, the following low tide exposes this entire wall, and beach combers on the formerly submerged, rocky beach view the same array of marine life - now exposed to the elements.

Tides in parts of Alaska can be 20 feet or more between extreme high and low tides. Life in the intertidal means enduring wind, ice, pounding surf, hungry predators and extreme changes in temperature, moisture and salinity. The upper intertidal is more dry than wet, and creatures here, like barnacles, must endure long periods out of the water. Cemented to the rocks with one of natures' strongest glues, barnacles close up tight to wait out the low tide.

In the middle intertidal section, blue mussels anchor themselves to the rocks with strong, byssal threads. The middle intertidal can accommodate more life because it is submerged more.

The lower intertidal is almost always wet, and teems with life, home to sea stars, snails, chitons, urchins and anemones. Kelp is anchored to the seafloor with a root-like structure called a holdfast, and stretches from the lower intertidal to the upper intertidal, forming a breakwater shelter for intertidal animals and a blanket of moisture at low tide.