Searching for seashells at low tide in the intertidal zone along the rocky and sandy coast of Brittany, France
Click on image for full size
Courtesy of Annette Pharamond
Life in the Intertidal Zone
The intertidal zone is the area along a coastline that is underwater at high tide and above the water at low tide. Life in the intertidal zone needs to be able to survive extreme conditions - both above the water and below. When the tide is low, living things are out of the water and they can be exposed to heat and bright sunlight. When the tide is high living things can be pounded by waves.
Conditions are more like living on land for creatures in the upper part of the intertidal, which is only covered with water at extreme high tide. Conditions are more like living in the ocean for creatures in the lower part of the intertidal which is only exposed to air at extreme low tide. Some plants, animals, and algae are better adapted to living in the upper intertidal, while others are better adapted to living in the lower intertidal.
On rocky coastlines, there are often many types of algae and small snails that eat the algae. Animals that attach to the rocks such as barnacles and mussels can be common. Sea urchins and sponges live in areas that are usually covered with water. There are sometimes small pools of water between rocks that remain even after the tide goes out. These are called tide pools and they are often filled with many different animals, plants, and algae.
Coastal marshes, or wetlands, form in areas that are protected from waves. They usually have soft mud, quiet water, and grasses. During low tide, the mud is often exposed above the water. Molluscs like clams, mussels, and oysters can be found in and on the mud. Crabs, fish, and shrimp are also common in marsh areas. Many types of microscopic plants live in the mud too.
On sandy beaches, the intertidal zone is often home to animals that live in burrows within the sand such as clams and worms. Crabs scurry across the sand and usually have burrows too. Large waves often crash along sandy beaches, so living in a burrow offers some protection.
Last modified June 1, 2010 by Lisa Gardiner.
Shop Windows to the Universe Science Store!
The Summer 2010 issue of The Earth Scientist
, available in our online store
, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.
You might also be interested in:
Extreme environments are places where "normal" life finds it hard to survive. That doesn't mean that there isn't any life in extreme environments. Certain creatures can live and grow in extreme environments....more
Kingdom Plantae contains almost 300,000 different species of plants. It is not the largest kingdom, but it is a very important one! In the process known as "photosynthesis", plants use the energy of the...more
An aquifer is the name for a layer of rock which is capable of holding a large amount of water. Some layers are better at holding water than others, for example a layer of sandstone can hold a good deal...more
Carbonate is a name for rocks and minerals which contain a molecule made of both carbon and oxygen known as CO32-. (CO32- is also known as the molecule carbonate). Limestone is an example of a calcium...more
The deep ocean waters are under pressure and are much colder than layers of the ocean which are closer to the surface. Dissolved carbon dioxide seems to be absent from the deep ocean water and as a result...more
One process which transfers water from the ground back to the atmosphere is evaporation. Evaporation is when water passes from a liquid phase to a gas phase. Rates of evaporation of water depend on things...more
The water at the ocean surface is moved primarily by winds that blow in certain patterns because of the Earth’s spin and the Coriolis Effect. Winds are able to move the top 400 meters of the ocean creating...more