Tidal Levels - General Description
Researchers over the years have tried to compare the various tidal levels on ocean shores to create a system that can be used on any shore around the World. Some researchers have used the varying lunar-month tidal levels, while others have used indicator species to define the various levels.
Some naming systems are very complex and use descriptions such as infralittoral, high midlittoral, high-water spring and high-water neap tides if the system is based upon the tides.
Littoral means tidal.
During a lunar month you will get a very high and a very low tide called the Spring Tide (this has nothing to do with the season Spring). A fortnight later there is a lower high tide and a corresponding higher low tide, called the Neap Tide.
Other researchers have based their system on the bands of fixed-location or sessile animals. They use categories such as the Upper Barnacle Zone, Lower Barnacle Zone, Cunjevoi Zone, etc.
This Seashore Life Web Site uses a generalised system based upon assumed tidal levels for any Australian shore.
This is the level just above the highest tide level reached in any month. It may be wetted by spray and mist. On some wave-smashed rugged shores the Splash Fringe Level may extend a few hundred metres up a shore or up a cliff face. On very calm shores, this zone will not exist.
The upper part of the High-Tide Level is covered by the tide for only a few hours each day. Some creatures found here may only covered by water for a few hours each month. The dominant stationary animals are the high-shore barnacles. Below these are the semi-mobile molluscs, such as the limpets, siphon shells, chitons, top shells, conniwinks and the black nerite.
Along many south-eastern Australian shores, there is a characteristic band of hard, white, limy Galeolaria tube worms, which may form dense colonies. Many intertidal animals are adapted to living in the microhabitat provided by the thick tube-worm colonies. This level is covered and uncovered for about an equal time each tide cycle.
This region, which often occupied by the sea-squirt Cunjevoi is uncovered for only a few hours each tidal cycle and is the favoured habitat of a large range of intertidal species.
Most species in this Web Site are found at this level, and include anemones, sea stars, sea urchins, chitons, tritons, whelks, limpets, barnacles and crabs. Some algal (seaweeds) species occur in moist gutters, crevices and in rock pools.
Here, low tide oscillates around this level during the lunar month. At low tide this level is wetted and exposed during each wave. Most creatures and algae are fully marine and are not really adapted to spending some time exposed. Some carnivores move into the intertidal region to eat easily captured attached prey, such as barnacles, cunjevoi and slow-moving limpets. Most algal species live here.
Species found here are not adapted to spending any of their life cycle in the intertidal zone, except by accident. Some come in at high tide as predators of intertidal species. Many carnivorous fish and decapod crabs fit this category. A large range of algae are found here.
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