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  On-line Guide to Chek Jawa
introduction
 
Life on the Edge
Why is the intertidal zone special? | More about tides | Tides on Chek Jawa

The coastal area that is covered by water at high tide and exposed at low tide is called the intertidal zone. This zone is rich in lifeforms because the twice-daily change in water levels supports two 'shifts' of activity in the same area. For example, some animals are active at low tide while aquatic creatures take over at high tide. The tides thus strongly affect the rhythm of life on the intertidal zone.
  

Incoming tides bring in fresh supplies of oxygen, nutrients and plankton to shallow areas. Seeds of coastal and mangrove plants also float in to colonise new spots. At high tide, filter-feeders gorge while fish can forage in the shallows.  


Outgoing tides flush out waste and deliver nutrients to habitats further away from the shore. Floating out with the tide are animals, their eggs and free-swimming larvae, seaweeds, and seeds of seagrass and mangroves. At low tide, some creatures feed on the intertidal flats, safe from aquatic predators (but they still have to look out for land predators!). Aquatic animals take shelter in shallow pools left behind at low tide.

Life by the Moon: The cycle of spring and neap tides profoundly influences life on the intertidal zone. For example, eggs and larvae are usually released at spring tide so that they can be carried far out to sea with the extra high tide. 		 
See also ...
More about the tides
Sequence photos of how much of Chek Jawa is exposed at various tide levels

Links
Life on the Edge on the Fitzgerald Marine Reserve website: brief description of the intertidal zone.
Shorelines on the MBG Net website: easy introduction to shores, estuaries, mudflats, mangroves and the plants and animals that live in these habitats, with animated diagrams and links to related sites.
Rocky intertidal zone on the Marine Biology page of the Glendale Community College website: introduction to concepts of intertidal zones, tides, zonation, ettiquette for visitors and fact sheets on the plants and animals of the habitats. Photos, links and references too.
Exploring the Intertidal: An Online Intertidal Field Guide on the OceanLink website: quick intro to all the elements of an intertidal zone including the plants and animals there.
Between the Tides and a Hard Place by Gavin W. Maneveldt on the Botany@UWC site of the University of the Western Cape website: seaweeds, other plants and lichens of the intertidal zone. An article first published in Veld&Flora.
Tidal levels on Life on Australian Seashores by Keith Davey on the Marine Education Society of Australia website: a fabulous goldmine of a site which covers various kinds of intertidal habitats and their inhabitants. Fact sheet on the different ways to describe tidal zones.
 

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