Understanding the Tidal Zones

Great Places to Explore

Great Places to Explore

There are four main tidal zones. The intertidal zone which is where the tides come and go and the water levels change have three main zones and in each zone you will find different life forms.

High Intertidal Zone
This is the area where the high tide covers.  Creatures that live in this area need to be able to withstand long periods of time out of the water and exposed to wind, rain and sun.  To do this many of them have developed hard cases, or shells, that completly cut them off from the elements, allowing them to hold moisture until the tide returns.  It is approximatly 11 hours between the tides, so these creatures have learnt to survive.  What lives here may not be able to live in the lower zones.

In this area you will find barnacles, limpets, sea snails and oysters. Crabs also lurk here, hiding in the cracks  in the rocks so they are sheltered from the sun.

Mid Intertidal Zone
This is the bulk area that is exposed when the tide goes out and it is here that you will often find rocks pools.  The creatures that live in rock pools have to be able to cope with the water evaporating in the rock pools which makes the water more salty than the open ocean.

In this area you will find barnacles, limpets, sea snails, mussels, chitons, crabs, the start of sea weeds, small fish, nudibranches, sea hares and star fish to name a few.

Low Intertidal Zone
Out of the three zones, this one is the one that only is exposed for a short time.  However, there are creatures that can live here as well as in the other two zones.

In this area you will find limpets, sea snails, chitons, crabs, sea weeds, small fish, kina, nudibranches, sea hares, star fish, octopus, worms and brittle stars to name a few.

Shallow Sub Tidal Zone
This is the area past the low intertidal zone and is always covered with water, even during a very low tide. While this area usually goes to about 5m deep, here at this site the maximum depth that has been explored is down to two metres deep.

The following image shows how the tides work.

How Tides Work

Diagram showing the fall and rise of tides exposing rock pools in different tide zones.