Seaweed of the Tidal Regions

Tide Zones / Seaweed / Porifera / Coelenterates / Molluscs / Arthropods / Echinoderms

In the intertidal region, there is much competition between the plants and animals. The different types of algae, green, red, and brown, have developed important adaptations allowing them to survive in the near-shore, shallow marine environments. The algae like the rocky shores because the solid rocks give them something to attach to. This is important, because algae must be in a place where they can make their own food through photosynthesis. Also, by holding on to the rocks, algae can withstand the punishment that over 8000 waves dish out over the period of one day! This is a big problem for most algae as you can imagine. Another threat to algae is the numerous herbivores (plant eaters) that graze on nice, juicy green leaves. At the right is an amphipod feeding on sea lettuce. This herbivore turns green from digesting chlorophyll when eating the sea lettuce!

Follow the following link and you will learn how algae hold on to the rocks in the rocky shore. Getting a Grip!

The most common green algae is sea lettuce. The delicate sea lettuce loses its moisture during low tide and becomes crispy yet remains alive. When the tide rises again, it absorbs water. At the left you can see the yellow arrow pointing to the sea lettuce. We will see a great deal of sea lettuce when we go to the tide pools. The other green plant that you see in the picture is sea grass. To see what you may be walking on when we visit the tide pools, click on the following link. Green Algae.

The red algae known as the sea sac is found in large patches in the mid tide zone. It got its name from the hollow core that holds water to keep it from drying out at low tide. When you look at the sea sac, you will notice, that it does not need to be red in color, yet it is still considered a red algae. That's because red algae has a red pigmentation (coloring) in its chlorophyll. This pigmentation helps red algae survive at greater depths and still photosynthesize.

Coralline red algae, defends itself from grazing herbivores by secreting a lime-like substance that makes it a tough, crusty plant. This crustiness also helps protect it from the crashing waves. You can see a specimen of this crusty plant at the left. Coralline red algae is called a "reef builder." Can you see why?

The pepper dulce, another red algae, has numerous branches and leaves to help it in the process of photosynthesis. It has also evolved another defense mechanism. It has a biting, peppery taste and may give out noxious chemicals that make it unappetizing.

There are few open spaces in the intertidal area for the algae to attach. Some of the algae attach to other plants or animals. The smithora (a red algae) attaches to the surf grass, almost completely covering it. Biologists believe that a symbiosis occurs where the smithora protects the surf grass from grazing herbivores and the surf grass gives the smithora a place to live.

There are many types of brown algae. They have to fight the same types of problems as green and red algae: damage from waves; drying out; grazing by herbivores; and competition for available attachment space. Rockweed is a common brown algae. It survives drying out because of its thick cell walls that contain moisture and sugar. Lessoniopsis is a kelp found in the most exposed, wave-battered areas. It has a thick, woody holdfast that enables it to survive in this environment. The drawing at the right is a lessoniopsis.

The bull kelp is one of the "giant kelps." It looks like a long whip with an air bladder at the top. The bull kelp lives for only one year but has been known to grow ten centimeters a day (very cool pictures of kelp). We will only see bull kelp that has become detatched and washed up on the beach. You'll know it when you see it. Another very common brown alga you'll see is the feathered boa.

You have, no doubt, heard that we eat algae when we enjoy ice cream. But did you know that there are many other economic uses of algae? Follow that last link and you'll be amazed.

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