Where the land and sea meet, a unique ecosystem contends with the rise and fall of the ocean’s tides each day. This area is called the intertidal zone or littoral zone. The organisms within the intertidal zone possess special adaptations to contend with the challenges of this ecosystem.
TL;DR (Too Long; Didn't Read)
The intertidal zone marks the area where the ocean and land meet. This unique ecosystem maintains an important balance for the food chain, supplies erosion protection and serves as an indicator for climate change.
The Intertidal or Littoral Zone Definition
The intertidal or littoral zone definition is the general area where the ocean meets the land. The intertidal zone can exist in either sandy or rocky beaches.
Subcategories describe the different portions of the intertidal zone. These include the spray zone, high intertidal zone, middle intertidal zone and low intertidal zone.
The Spray Zone
In the spray zone, the highest level of the intertidal zone, the beach is splashed by salt spray but never fully submerged by the sea. Since much of the spray zone is land, animals and plants that call it home are adapted to more air and all manner of weather. Organisms found in the spray zone include lichens and periwinkle snails, to name a few.
The High Intertidal Zone
The high intertidal zone becomes inundated during high tides. At low tides, this area is exposed for long enough that resident organisms must be adapted to living outside the water. Mussels and barnacles reside in the high or upper intertidal zone.
The Middle Intertidal Zone
The middle intertidal zone is typically covered with seawater. At low tide, however, the area is exposed. This is an area of greater animal and plant diversity, and organisms are adapted to more water.
The Low Intertidal Zone
The low intertidal zone only experiences exposure to air during the absolute lowest tides, and therefore organisms within it are used to living under the sea. Organisms in this zone include:
- sea urchins
- other fish
The Rocky Shore
When water recedes at low tide, tide pools form, making microenvironments for the creatures in them. Organisms in the rocky shore include:
- sea stars
- sea cucumbers
The Sandy Shore
On a sandy beach, a littoral zone organism adapts to live in sand, often burrowing down into wet sand at low tide to avoid exposure. At high tide they venture forth again.
The sandy shore provides important feeding grounds for shorebirds, as well as a food supply for many animals. Organisms that call the sandy shore home include shrimp, clams, sand dollars and worms.
Advantages and Disadvantages of Living in the Intertidal Zone
Any littoral zone organism must withstand various challenges in such a dynamic environment. There are both advantages and disadvantages for a littoral zone organism in this ecosystem.
Every littoral zone organism possesses the adaptations necessary to survive in its respective region of the intertidal zone. An organism adapted only for land or only for the deep ocean might not thrive in the intertidal zone.
A littoral zone organism can withstand various elements such as pounding surf and drying out at low tide. Special holdfasts, such as those in kelp, prevent the waves from removing them from their substrate. Barnacles use a type of cement to stay attached to rocks. These same features can potentially prevent predation.
The disadvantages of being a littoral zone organism include predation by mobile animals such as birds, mammals and fish. Being exposed to the air for too long can harm some organisms. Animals such as mussels and barnacles are able to keep some seawater in their shells to withstand such exposure.
Changes in water chemistry or oxygen levels threaten the delicate balance a littoral zone organism uses to survive. Climate change and its resultant sea level changes could threaten creatures adapted to one portion of the intertidal zone.
Why Is the Intertidal Zone Important?
The intertidal or littoral zone maintains a balance between the land and the sea. It provides a home to specially adapted marine plants and animals. Those organisms, in turn, serve as food for many other animals.
The intertidal zone also staves off erosion caused by storms. Oyster reefs are one such example of a protective feature. This helps protect the structures built by people.
Threats to the Intertidal Zone
The intertidal zone is also an important indicator for climate change on marine organisms.
Satellite imagery reveals a loss to intertidal communities. The intertidal zone is a delicate ecosystem, threatened by rising sea levels due to climate change. Development by humans threatens the intertidal zone as well.
Changes in temperature due to climate change also threaten the organisms outright. Spikes in temperature can lead to die-offs, creating a catastrophic effect in the food chain.
Most organisms in the intertidal zone are only adapted to a particular temperature range. Researchers are taking a closer look at temperature changes in the intertidal zone ecosystems of the world.
The intertidal zone is also susceptible to pollution and trash. When you explore a beach, rocky shores or tide pools, leave shells for the hermit crabs. Collect any trash you see. Volunteer to help conserve this fascinating ecosystem.
- Capital Regional District: What Is the Intertidal Zone?
- National Centers for Coastal Ocean Science: Climate Change Impacts on Intertidal Zone Populations
- National Park Service Oceans, Coasts & Seashores: Intertidal
- Smithsonian Magazine: A Photographer Documents the Effects of Climate Change on Maine’s Intertidal Zones
About the Author
J. Dianne Dotson is a science writer with a degree in zoology/ecology and evolutionary biology. She spent nine years working in laboratory and clinical research. A lifelong writer, Dianne is also a content manager and science fiction and fantasy novelist. Dianne features science as well as writing topics on her website, jdiannedotson.com.
flamingo feeding image by rrruss from Fotolia.com