Download Inhabiting the Intertidal - Marine WATERs

Inhabiting the
Intertidal
The intertidal zone, also known as the littoral zone, is that area
between high tide and low tide. It is home to many species of
animals and plant-like organisms (algae). Many of the animals are
invertebrates (animals without backbones). It is a harsh
environment for organisms to live in. Organisms in this zone thus
have a variety of adaptations to allow them to survive.
Barnacles attach themselves to hard substrates with a glue-like
substance on their head. They filter feed plankton from the
water with feathery appendages.
Periwinkles can survive for long periods out
of the water due to their horny, tight-fitting
trap door (operculum) which retains
moisture within their shell.
Chitons have eight separate shell plates that act like armour. They
lack eyes and use a modified mouth part called a radula to scrape
algae off rocks.
Limpets have a coneshaped shell and
muscular foot. They
graze on algae at high
tide and generally
return to the exact
place that they left.
Sea lettuce (Ulva sp.), a type of green algae, is named for its
appearance and the fact that it is edible.
Caulerpa racemosa grows to depths of 4 metres and in areas of good
wave action. It is easily identified by its bubble-like branches (called
ramuli).
© Department of Fisheries, Michael Burgess
Gastropods or marine snails
form the largest class of
molluscs. Most species have a
spirally coiled shell, and are
grazers, although some species
are scavengers while some are
predators, including the
infamous cone shell.
Turban snails can pull their body
inside their shell and completely close
the aperture with a shelly trap door
called an operculum (inset picture).
Abalone have a hard, rough, ear-shaped shell that is smooth and
shiny on the inside to protect the animals soft body from damage.
Abalone do not have a blood-clotting agent and therefore may
bleed to death if damaged or injured when removed from the reef.
Anemones are related to corals and also sea jellies. They have a
central mouth surrounded by one or more rows of tentacles.
Mussels are a
bivalve mollusc,
meaning they have
a shell with two
halves (valves).
They attach to the
substrate by tough,
yet flexible threads
(byssal threads).
Red algae are the most numerous of the three seaweed groups.
They can tolerate lower light levels than other algae, and are thus
most abundant in deeper water. The texture of red algae varies
from fine and delicate to hard and crusty.
Funnel weed is a brown
algae with fan shaped
fronds that give it its name.
It is the only brown alga in
Australia that accumulates
a thin chalky coating on
one surface, known as
calcification.
Sargassum can generally be
identified by the small
bubble-like floats. Sargassum
is a Spanish term for ‘floating
seaweed’
Kelp can form large beds that become home to numerous
invertebrates and is an important food source for sea urchins,
buffalo bream and other animals.
Kelp and other brown algae contain a gelatinous substance called
algin that is widely used as a thickening or stabilising agent in many
of our foods.
Sponges are often mistaken for
plants but are in fact very
simple animals. Their bodies
are full of tiny holes which help
them to eat and breathe by
filtering seawater.
Sea urchins are grazers, feeding on encrusting organisms such as
sponges and algae. Their mouth is in the centre on the underside
and contains a set of jaws and horny teeth, named Aristotle’s
lantern.
© Department of Fisheries, Michael Burgess
© Department of Fisheries, Michael Burgess
Sea stars are a type of echinoderm, consisting of five or more arms
radiating out from a central disc. The mouth and tube feet are
located on the underside of the body. Many echinoderms are able
to regrow lost or damaged parts of their bodies.
Sea cucumbers are echinoderms, related to sea stars and sea
urchins. They move using their tube feet, or by squeezing up and
then stretching out their bodies.
Sea hares are a type of mollusc, closely related to nudibranchs (or
sea slugs). They graze on algae and have a very short life span of
only a year, dying after laying their long, tangled strings of eggs.
Crabs are a type of crustacean. They have a hard exoskeleton that
serves as a suit of armour. In order to grow, crabs periodically
shed their exoskeleton, a process known as moulting.
Small fish, such as blowies – a scavenger species, may also inhabit
the lower intertidal zone at high tide.