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Intertidal Zone - Marine Life, Challenges and Conservation


Ochre Sea Star, Pisaster ochraceus, Califonria mussels and brown algae in intertidal zone at low tide, Oregon, USA
Ed Reschke/Stockbyte/Getty Images


The intertidal zone is the area where land and sea meet. This habitat is covered with water at high tide, and exposed to air at low tide. The land in this zone can be rocky, sandy or covered in mudflats.

The intertidal zone is divided into several zones, starting near dry land with the splash zone, an area that is usually dry, and moving down to the littoral zone, which is usually underwater. Within the intertidal zone, you’ll find tide pools, puddles left in the rocks as water recedes when the tide goes out.

Challenges in the Intertidal Zone:

The intertidal is home to a wide variety of organisms. Organisms in this zone have many adaptations that allow them to survive in this challenging, ever-changing environment.

Moisture: There are usually two high tides and two low tides each day. Depending on the time of day, different areas of the intertidal zone may be wet or dry. Organisms in this habitat must be able to adapt if they are left “high and dry” when the tide goes out. Sea snails such as periwinkles have a “trap door” called an operculum that they can close when they are out of water to keep moisture in.

Waves: In some areas, waves hit the intertidal zone with force, and marine animals and plants must be able to protect themselves. Kelp, a type of algae, has a root-like structure called a “holdfast” that it uses to attach to rocks or mussels, thus keeping it in place.

Salinity: Depending on rainfall, the water in the intertidal may be more or less salty, and tide pool organisms must adapt to increases or decreases in salt throughout the day.

Temperature: As the tide goes out, tide pools and shallow areas in the intertidal will become more vulnerable to temperature changes that could occur from increased sunlight or colder weather. Some tide pool animals hide under plants in the tide pool to find shelter from the sun.

Marine Life in the Intertidal Zone:

The intertidal is home to many species of animals and plants. Many of the animals are invertebrates (animals without a spine), which comprise a wide group of organisms.

Some examples of invertebrates found in tide pools are crabs, urchins, sea stars, sea anemones, barnacles, snails, mussels and limpets. The intertidal is also home to marine vertebrates, some of whom prey on intertidal animals, such as fish, gulls and seals.

Threats to the Intertidal Zone:

Visitors: People are one of the biggest threats to the intertidal zone, as tide pools are popular attractions. The cumulative impact of people exploring tide pools and stepping on organisms and their habitat, and sometimes taking creatures, has resulted in a decrease in organisms in some areas.

Coastal Development: Pollution and runoff from increased development can damage tide pools through the introduction of contaminants.

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