Unit One CINMS

Intertidal

Lesson Objectives: Students will be able to do the following: • Describe the rocky • Differentiate between the four intertidal zones • Explain one way that physical processes affect organism distribution

Key concepts: intertidal zones, nutrient , desiccation, holdfasts, water vascular systems, larval

Physical Description of the Rocky Intertidal Zone

Intertidal zones are runoff from rain and streams. This transitional coastal relatively dry area is sparsely regions. The cycling populated. Few organisms can of the withstand the extreme fluctuations in influences these moisture, temperature, and salinity regions. These found in this zone. littoral areas are located between the high and low The high intertidal zone is completely marks. They can be found along covered with water only during high rocky shores or sandy . We tide. Parts of this region are exposed will be taking a closer look at the to the air for long periods as the tides rocky intertidal region. It is recede. The inhabitants of this area characterized by sturdy boulders, are sturdy individuals. They rocks, crevices, and ledges that are can remain wet even if home to a variety of organisms. they are exposed to the sun and wind. The The rocky intertidal region can be organisms in this area divided into four vertical zones. have also developed attachment These zones are based on height devices to help them resist the force and tidal influence. These four zones of the waves. These devices include include from the highest to the muscular feet, suction cups, byssal lowest: the splash zone, the high threads, or holdfasts. intertidal zone, the mid-intertidal zone, and the low intertidal zone. The mid-intertidal zone is the area The splash or spray zone is the between the average high tide and highest and low tide mark. This region is covered driest area. by water during most high tides, but This it is exposed to the air during most supralittoral low tides. This environment contains zone is above the highest high tide a more diverse group of organisms, mark. It is moistened by saltwater than either the splash zone or high spray from waves and freshwater intertidal zone. This area is also

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highly populated. Organisms that live , and grazers enjoy the rich here must overcome space and of available. problems. To overcome some of these problems, organisms These four zones can be have developed specialized niches different from place to within the . Some place. Some of them organisms grow more quickly than may contain highly others, so they can find the required specific microhabitats space. Others grow in layers on top such as tidepools. Tidepools are of each other to take up less room. created as the tides recede leaving rocky depressions filled with water. The low intertidal zone is the area These areas are interesting and fun between the average low tide level to explore, because they are home and the lowest low tide level. This to some unusual creatures. The area stays moist during organisms within the tidepools have most low tides making it had to adapt to extreme changes in an ideal home for many salinity. They are able to survive kinds of organisms. The falling salinity levels as rain freshens low intertidal zone also the water. They can also withstand has lots of food as nutrients are rising salinity levels as the sun and circulated in nearshore waters. Many wind evaporate the water leaving the are found within this salt concentrated.

Typical Animals of the Littoral Zones

Hardy organisms can being tossed about by incoming be found within the high waves. Once anchored in place, they intertidal zone. They begin to build a home of calcium can withstand the carbonate plates. Four plates make pounding waves and a door that can be opened and extremes in temperature, salinity, closed. This door protects them from and water availability. One such predators or keeps them from organism is the . This drying out. Once their home is interesting creature is a crustacean complete, they use their feathery or relative of the shrimp. Like other legs to filter food from the water. crustaceans, it has a tough, These legs, called cirri, have protective covering made of chitin. sensory organs that can locate During their juvenile, or larval plankton in the water. As the stages, swim freely about barnacle grows, it must shed its in the searching for a chitin shell and enlarge its home. place to live. Once they find a place When it is time to reproduce, the to settle, they produce a glue. This hermaphroditic barnacles extend glue oozes from their head. They sperm filled tubes to neighboring use this glue to attach themselves to barnacles. Fertilization takes place the substrate. This keeps them from and the cycle begins again.

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The low intertidal zone is home to organisms that have developed special to live within this region. Two organisms that we will take a closer look at are the and the ochre star. Sea anemones have a cylindrical body and a central mouth surrounded by tentacles. These tentacles contain stinging cells called nematocysts that are used to stun prey such as small . The anemone then swallows and digests the prey. The waste Organisms in the mid-intertidal zone products are released back into the must also adapt to wave action and water through its mouth. Sea try to prevent drying out. An animal anemones can reproduce in two typically found in this zone is the ways. In sexual reproduction, . are bivalve fertilized eggs are released in the mollusks. This means that they have water column. In asexual two shells or valves that are hinged reproduction, anemones create on one side. They also have a clones. muscular foot for locomotion. During These reproduction sperm and eggs are clones released into the water. The eggs can form are then fertilized. Mussel larvae large develop and float in the water until colonies they find a place to settle. Once where settled, they secrete fibrous threads intruders from a gland in their foot. These are not byssal threads are used to help the welcome. Threatened anemones mussel adhere to the rocks. Mussels may shrivel up, or they may fight live close together. They eat by using a specialized tentacle filtering small particles of organic containing many nematocysts for matter from the seawater. They stinging their enemies. To prevent close their shells tightly to keep in drying out, anemones can turn their moisture while the tide is out or to tentacles inward and shrink or move protect themselves from predators to a moist location using a special such as the sea star. foot called a pedal.

The ochre sea star (Pisaster ochraceus) is an echinoderm or spiny skinned animal. Its reproductive cycle begins with the releasing of eggs and sperm into the water. The fertilized eggs continue to

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divide. Eventually they ready to eat, it grips its prey with its become larvae. These tube feet and wraps its arms around larvae develop the shell. Using waterpower, it pries through two stages. open the shell. It then expels its The first free-swimming stomach into the opening. Digestive larval stage eats small juices dissolve the soft tissues of the plankton. The second larval stage bivalve. Sea stars also have develops arms and a suction cup interesting ways of protecting base. It attaches itself to a rock with themselves. The tough integument a tube foot and grows into a juvenile or outer covering of some sea stars sea star. As these animals grow, keeps them from drying out. Some they become very hungry. They must sea stars can stay out of water for 50 move about to hunt for food. They hours. They can also regenerate lost use their water vascular system to arms, so they can continue their operate their tube feet. In this predatory life style. system, water enters and exists the sea star through an opening on its back. This opening is called the madroporite. As water flows through the sea star, it can create suction that helps the tube feet to stick to surfaces. The sea star also uses its water vascular system to help it open bivalve shells. When the sea star is

PISCO: Intertidal Research

Scientists are Scientists at four universities have interested in come together to form a studying the collaborative research program. This rocky intertidal program is known as the Partnership zone, because it for Interdisciplinary Studies on is a highly Coastal Oceans (PISCO). PISCO is structured biodiverse region. In the conducting an extensive study of the past, research was limited to small intertidal region that will bring sample areas. Scientists would study together physical and biological either physical factors or biological information. These data will be factors. This information was collected from over 1200 miles of the valuable, but it didn’t help scientists nearshore Pacific coast reaching understand the overall picture. They from Oregon to California. Using this wanted to learn more about what broad approach, PISCO researchers was happening in these areas and will collect information about larval how this affected surrounding organisms. They are especially environments. interested in larval recruitment.

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Larvae or immature forms of many recruitment platforms. They are intertidal organisms recruit or settle trying to see how many organisms of to hard surfaces where they stay different kinds attach themselves to anchored for life. These larvae these platforms. Information from dispersed in water and moved about these studies can be used to by currents have only a short time to understand some of the complicated find a suitable home. Scientists life processes that take place in the studying these immature forms are intertidal zone. This research should placing artificial substrates in the help scientists gather information study areas. They are using clay tiles that will improve conservation efforts and kitchen scrubbers (tuffies) as in our ocean systems.

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