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Tidal Zones
Estuaries can also be divided into tidal zones (supratidal, intertidal and subtidal zone) subject to changing water levels, temperature, oxygen content and levels of light.
With the incoming and ebbing tide, life exists in zonal habitats. Zonation describes the different zones or areas of the estuarine environment. Different organisms live in different zones depending on what conditions they are adapted to.
- Supratidal Zone – The supratidal zone is the area above the high tide water line that extends upland. This area is seldom covered by water. Some part of this zone can receive moisture from wave splash. Land-based or terrestrial animals and plants survive here if they can tolerate some seawater or brackish water. Marine animals and plants survive here if they can tolerate exposure to air. Some examples of organisms in the zone include: various trees, and shrubs, mammals such as deer and fox, birds, reptiles and much more.
- Intertidal Zone – The intertidal zone is the area that is exposed to the air at low tide and submerged at high tide. This area can include many different types of habitats, including steep rocky cliffs, sandy beaches or vast mudflats. Organisms in the intertidal zone are adapted to harsh extremes. Water can be high due to tides, rain and run off, and this water can be very salty at one time and very fresh another. These areas can also become very dry when tides are low for extended periods of time. Temperatures can range from very hot with full sun to freezing in colder climates. Some examples of organisms that live in the intertidal zone include: shore birds, marsh grasses, shrimp and fish (when water is present), snails, mussels and oysters, burrowing worms and much more.
- Subtidal Zone – The intertidal zone is the area below the low tide water line. This area is always covered by water. This area can include many different types of habitats, including soft and hard bottom, submerged aquatic vegetation beds and coral reefs. The organisms here can not tolerate very long exposure to the air or sun. Some examples of organisms that live in the subtidal zone include: eel grass, algae, fish, starfish, shrimp, crabs, dolphins and much more.
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Last Updated on: 06-24-2008
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