Intertidal Habitats

1. Intertidal Zones

2. There are different kinds of
intertidal habitats including
rocky shores, mangrove swamps
and sandy beaches.
Sandy beaches and mangrove
swamps require very different
adaptations from rocky shores.
There are different kinds of
intertidal habitats including
rocky shores, mangrove swamps
and sandy beaches.
Sandy beaches and mangrove
swamps require very different
adaptations from rocky shores.

3. There is a large community of organisms inhabiting most sandy
beaches, however the number of species represented is limited.
The shifting sands and rapidly changing conditions makes it
difficult to live in this habitat. Only a few species have been
successful. Those that have successfully adapted to this habitat,
enjoy lower levels of competition and can grow to larger
populations.
There is a large community of organisms inhabiting most sandy
beaches, however the number of species represented is limited.
The shifting sands and rapidly changing conditions makes it
difficult to live in this habitat. Only a few species have been
successful. Those that have successfully adapted to this habitat,
enjoy lower levels of competition and can grow to larger
populations.

4. Sandy beaches offer little substrate or solid surface to attach
to. Organisms often bury themselves in the mud to survive.

5. Rocky shores, like those at Port Noarlunga, offer little protection
from strong waves. Organisms must adhere to the substrate.
Complex tide pools are possible and seaweeds offer protection
from drying out.
Rocky shores, like those at Port Noarlunga, offer little protection
from strong waves. Organisms must adhere to the substrate.
Complex tide pools are possible and seaweeds offer protection
from drying out.

6. The intertidal zone, also known as the littoral zone or as the
foreshore and seashore , is that area between high tide and low
tide. It can be divided the following subzones – spray zone, upper
intertidal zone, mid intertidal zone and the lower intertidal zone. It
is an area that is constantly changing as the water moves in and out
with the tides. Thus organisms inhabiting this area have a variety of
adaptations that allow them to survive.

8. The spray zone, or supra-littoral zone is the highest zone of true
marine life. It is usually only kept damp through wave splash.
Organisms surviving this environment include barnacles, limpets
and periwinkles (pictured).

9. Organisms exposed to the air here must be able to prevent
desiccation (or drying out).
Many have a protective covering such as a shell.
Organisms exposed to the air here must be able to prevent
desiccation (or drying out).
Many have a protective covering such as a shell.

10. The upper intertidal zone is only
covered by water at high tide. Any
algal growth is green, and the zone
is characterised by barnacles,
limpets, chitons, crabs, mussels, sea
stars and periwinkles.

11. The upper intertidal zone is an area of
high activity. As the tide flows in and out,
the area is buffeted. There is a diverse
mixture of organisms living in this zone.
The upper intertidal zone is an area of
high activity. As the tide flows in and out,
the area is buffeted. There is a diverse
mixture of organisms living in this zone.

12. Animals in more exposed locations tend to have thicker shells (e.g. turban
snails – pictured) than those in sheltered locations (e.g. pipis). Likewise,
many intertidal organisms, such as barnacles, limpets and chitons have
low profiles, close to the rocks.

13. The middle intertidal zone is regularly covered by water. Seaweed is
more prominent. Organisms in this zone include anemones
(pictured), barnacles, crabs, mussels, sea stars, gastropods and
sponges.

14. The middle intertidal zone is the most dynamic zone. It is covered and
uncovered twice per day as the tide comes in and out. Life in this zone
must tolerate both exposure to air and complete submersion.
he middle intertidal zone is the most dynamic zone. It is covered and
ncovered twice per day as the tide comes in and out. Life in this zone
must tolerate both exposure to air and complete submersion.

15. The lower intertidal
zone is usually
submerged, only being
exposed at very low
tides. The zone is
characterised by
brown algae (funnel
weed pictured – top),
encrusting sponges,
abalone, sea stars,
crabs, sea cucumbers,
gastropods and sea
urchins (pictured).
Small fish may also
inhabit the area.

16. The lower intertidal zone is the most diverse zone.
There is an abundance of different species here, including fish
and sessile feeders such as corals.
There is very little exposure to air and heat, so many
organisms can live here which cannot live in other zones.
The lower intertidal zone is the most diverse zone.
There is an abundance of different species here, including fish
and sessile feeders such as corals.
There is very little exposure to air and heat, so many
organisms can live here which cannot live in other zones.

17. The sub-tidal zone is just under the intertidal zone. This area is
very rarely exposed.
Many predatory species live here. They prey on animals in the low
tide zone. Animals here are not adapted to exposure to air, for
example fish, octopus and jellyfish.
The sub-tidal zone is just under the intertidal zone. This area is
very rarely exposed.
Many predatory species live here. They prey on animals in the low
tide zone. Animals here are not adapted to exposure to air, for
example fish, octopus and jellyfish.

18. © Department of Fisheries, Michael Burgess
Intertidal zones can be high energy environments, as waves pound
the area with force. Algae (seaweed) possess a root-like structure
called a holdfast that they use to anchor themselves to the
substrate.

19. Barnacles (pictured) attach themselves to the substrate with a
strong ‘glue’ and mussels with their byssal threads. Mobile
animals such as limpets and chitons use their muscular foot to
cling on to the reef during heavy wave action.

20. Salinity in the intertidal zone can be quite variable depending on
the amount of rainfall, and the rate of evaporation of the water.
Organisms inhabiting this area, particularly rock pools, can usually
withstand changes in salinity, and also temperature. Some animals
in rock pools will take shelter from direct sunlight under algae.

21. Animals inhabiting the intertidal zone may be restricted as to when
they can feed. Many sessile animals are filter feeders (feed on
planktonic material in the water) and thus are unable to feed when
the tide is out. Those animals that are not filter feeders may also
be restricted as they seek shelter from the elements and predators
at low tide.

22. In addition to the environmental challenges that organisms
inhabiting the intertidal zone face, one of their greatest threats is
humans. We cause damage to this environment as we step on
organisms and their habitats, and remove organisms altogether.
© Department of Fisheries, Alicia Edwards