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Intertidal Zone: About

Intertidal Zone

What is the Intertidal Zone?

The intertidal zone is an extreme ecosystem because it constantly experiences drastic changes. It is located on marine coastlines, including rocky shores and sandy beaches. The intertidal zone experiences two different states: one at low tide when it is exposed to the air and the other at high tide when it is submerged in seawater. The zone is completely submerged by the tide once or twice every day. This ecosystem is rife with research opportunities for marine researchers like National Geographic grantee Swapnale Gole, who studies the behavior of sea anemones, crustaceans, and fish in the intertidal zones of the Andaman Islands in India.

Organisms that live in the intertidal zone tend to form their own communities across the zone’s elevation gradient. Some species live further up the shore and closer to the high tide line, while others live further down the shore, closer the low tide line. Anything living in the intertidal zone must be able to survive changes in moisture, temperature, and salinity and withstand strong waves. Intertidal zones of rocky shorelines host sea stars, snails, seaweed, algae, and crabs. Barnacles, mussels, and kelps can survive in this environment by anchoring themselves to the rocks. Barnacles and mussels can also hold seawater in their closed shells to keep from drying out during low tide. Intertidal zones richer in sediments are filled with different species of clams, sand dollars, and worms.

At rocky shorelines, tide pools can form in holes, cracks, or crevices where seawater collects as the tide goes out. Organisms that cannot normally survive low tide conditions, like sea stars, shrimp, or fish, can take refuge in these pools. Sandy shores provide sediments in which organisms bury themselves to stay cool and moist during low tide. Where a species lives within the intertidal zone depends on its tolerance of underwater and above-water conditions. The presence of predators and species that compete for the same space and food also impact where an organism will be found. Continue reading from National Geographic

Zone Subdivisions

On the shore between high and low tide lies the intertidal zone, where land and sea meet. The intertidal zone is underwater during high tide and exposed to air during low tide. The animals and plants that live in this zone must cope with being submerged in water and exposed to the air during different times of day. Many species of worms, snails, clams, oysters, mussels and seastars make the intertidal zone their home. Rocky shores and sandy beaches fall within the intertidal zone. The motion of high tide and low tide creates four zones within the intertidal zone where different animals and plants live.

Spray Zone

The spray zone is the upper part of the beach that occasionally gets splashed, but never gets covered by the ocean. This zone is more a part of the land than the ocean. Plants and animals in the spray zone have adapted to living exposed to the air, sun, rain and even frost.

High Intertidal Zone

The high intertidal zone is flooded during the peaks of the once or twice daily high tides, and out of the water for long stretches of time in between. Here plants and animals are used to living above the water surface.

Mid Intertidal Zone

The middle intertidal zone is generally submerged, except for a period during the turn of low tide. More plants and animals live here because they are not exposed to drying conditions for too long.

Low Intertidal Zone

The lower intertidal zone is exposed to air for only a short period of time at low tide. Life here is adapted to conditions underwater. Continue reading from National Park Service

Importance to the Ecosystem

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.

The intertidal zone is also an important indicator for climate change on marine organisms. Continue reading from Sciencing

Learn More About Marine Ecosystems: From the Collection

Link to The Ocean of Life by Callum Roberts in the catalog
Link to Vanishing sands : losing beaches to mining by Orrin H. Pilkey in the catalog
Link to The Atlas of Disappearing Places: Our Coasts and Oceans in the Climate Crisis by Christina Conklin in the catalog
Link to Deep blue home : an intimate ecology of our wild ocean by Julia Whitty in the catalog
Link to Life Between the Tides by Adam Nicolson in the catalog
Link to Waters of the world : the story of the scientists who unraveled the mysteries of our oceans, atmosphere, and ice sheets and made the planet whole by Sarah Dry in the catalog
Link to The sea trilogy : Under the sea-wind ; The sea around us ; The edge of the sea by Rachel Carson in the catalog
Link to Ocean : the definitive visual guide by the American Museum of Natural History in the catalog
Link to Ocean anatomy : the curious parts & pieces of the world under the sea by Julia Rothman in the catalog
Link to by Anjanette Tadena on Freading
America's marine sanctuaries: a photographic exploration by US National Marine Sanctuary Foundation in the catalog
Link to The brilliant abyss : exploring the majestic hidden life of the deep ocean and the looming threat that imperils it by Helen Scales in the catalog
Link to Below the Edge of Darkness by Edith Widder PhD in the catalog

Link to Marine Ecosystems Resource Guide Series Homepage