Download Intertidal Zone Field Guide

Intertidal
zones in the
Great Barrier
Reef
A field guide for
Whitsunday Sea
kayaking journeys
LIVING BETWEEN THE TIDES
IN THIS ISSUE
Introducing the Intertidal Zone
Picture: Whitehaven Beach (Darren Tierney
Photography, 2011) Retrieved from:
http://www.qualia.com.au/aboutqualia/destination/whitsunday-islands
by Bree Tivendale 18068168
The intertidal, or littoral zone, is defined by
the high and low tide. During high tide the
zone is completely covered with sea water,
and at low tide the area is exposed. This
biome is therefore extremely variable and
includes different bioregions. These include
mangroves, mud flats, the reef crest, rocky
shores and sandy shores.
Bree Tivendale 1 80681 68
The intertidal zone can be broken down into
4 sections depending on the amount of time
they spend submerged (Marine Society of
Australasia, 2000). The lower intertidal zone is
found closest to the low tide mark and
spends the most amount of time underwater.
The high intertidal zone is found closest to
the hid tide mark with the mid intertidal zone
found in the middle. Above the high
intertidal zone is the splash or spray zone.
Although this zone is rarely ever submerged,
it is sprayed by the splashes of larger waves
and is therefore still exposed to littorial
action. Different species can be found at
different levels of the intertidal zone based
on these 4 sections and the amount of time
they spend under water (Marine Society of
Australasia (2000).
Diagrams drawn by Breanna Tivendale (2015). Adapted from the Marine Society of Australasia (2000). Original
image retrieved from: http://www.mesa.edu.au/friends/seashores/zonation.html
INTERTIDAL ZONE IN THE GREAT BARRIER REEF
2
Living in the Intertidal Zone
Intertidal Environments: Beach Rock
NOT AS SIMPLE AS GOING WITH THE
FLOW
This bioregion is always changing with
the tides usually coming in and out at
least twice a day with a battering force
(Davey.K.,2000). Not only do organisms
have to deal with being exposed to water
then air multiple times a day, as well as
the sun and highly variable temperatures,
they also have to defend against a variety
of terrestrial and marine predators
(Davey. K. 2000). This has cause these
littoral species to be quite unique, with
specific adaptations to survive this array
of environmental pressures.
Some physiological adaptations include
camouflage through attaching plant
matter to the individual, having a shell
that can hold in water and provide
protection from waves and predators.
There are also behavioral adaptations
such as hiding under rocks or in crevasses
from predators and the sun.
A Study conducted by Jason Sheehan
from Queensland University (2012) found
that the average temperature difference
between above rocks and below rocks
differed by 5.5 degrees Celsius. The
temperature below the rocks remained
within narrow limits to the temperature
of the water during high tide.
The organisms in this document are
organized into their biological classes.
Malacostraca are commonly called crabs,
Maxillopoda are referred to as Barnacles.
All species listed are found in the
Whitsunday’s area.
The rocky shore environment has been
focused on due to its higher level of larger
organisms that are easier to identify.
There are many more species to be found
in this environment, some of the species
identified are still in need of further study
to understand their place in the
ecosystem and to identify different
adaptive behaviors.
Great care should always be taken in this
environment to ensure no harm is done to
the ecosystem or to the individual. Do not
remove any organism or other objects
from their habitat and take extreme
caution if turning over rocks. Avoid
touching any organism and always return
rocks to their place.
Taken by Sandie Degnan (2015). Retrieved from: http://www.gbri.org.au//Habitats//Beachrock
Malacostraca
Menaethius monoceros: Also known as the
Spider Crab or Decorator Crab. Can be found
in the intertidal zone and upto a water depth
of 90m. This crab is know for camuflaging it’s
self by ‘decorating’ it’self in seaweed and
algaea’s. It therefore requires the presence of
algae and other sea plants on rocky shores.
Females typically are the largest in this
species. Students at Queensland university
recorded a female of 1.3cm and a male of
only 0.9cm. It has a distinctivly shaped body
which is covered with plant matter (Chiu Lo.
C. 2014)
Taken by Denis Riek (2013) Retrieved from:
http://www.roboastra.com/Crustacea6/hpde214.html
Eriphia sebana: Also known as the Red-eyed
Rock Crab. Males of this species can grow
anywhere between 39.2mm to 57mm in
length with females getting as big as 36mm.
These crabs can be identified by their stocky
build and their obvious red eyes. However
they are inactive during the day time, coming
out only at night to feed on molluscs and
anything else it can find.
Stimdromia lateralis: Also known as the
Ridged Sponge Crab. This species has an
adverage carpuce length of 29mm and can
be found in a variety of intertidal
environments including sand, mud, corals
and algae beds. They are typicaly orange to
dark red or brown in colour with their
Chelipeds (claws) being of a similar length.
The term ‘sponge crab’ comes from their
behaioural adaption to carry sponges on
their backs. These little crabs can be
distinguished from similar speices by their
last leg, which points the same direction as
all it’s other legs(Chan.C. 2014)
Gastropoda
Terence Tan (2011)
Planaxis sulcatus: Also known as a Furrowed
Clusterwink or a Tropical Periwinkle. They
are known to have shells that grow to around
35mm in length with females growing larger
than males. They can be found in both the
upper and lower littorial zones but are
inactive during low tide. The coils around
their shells are called whorls. The patterned
whorls are often covered by a range of
parasites covering them (Tan.T. 2011).
INTERTIDAL ZONE IN THE GREAT BARRIER REEF
3
Intertidal Environments: Beach Rock
Bornella stellifer: Also known as Starry
Bornella Nudibranch. Unlike most
invertebrate in the Gastropoda family these
organisms donnot have a procetive shell.
They only grow to around 24mm-48mm but
reduce their size by almost a third during low
tide when they undergo desication. They
have red geometric patterns along their
bodies and head with a translucent body.
Godiva sp.: This species of Gastropoda also
lack a shell. They can grow to around 1037mm long and are found in the lower littoral
zone. Cerata are located in patterned clumps
along their backs and can extend to as long
as 12mm when the organism is distressed.
The species lay their eggs in coiled ribbons
and look like yellow apple peels. These are
laid in an anti-clockwise direction.
Turbo militaris: Also known as The Military
Turban can grow upto a large 120mm in
length. Their outerlip is sharp surrounding
their almost round appeture. Their shells
have dark green and bown bands. These
Gastropods can be found mostly in northern
NSW, but also along rockyshores in QLD.
Although they are large, they are
hebivourious feeding mostly on algaes (Chin
Wai.C.2014)
Polyplacophora
Manning.F.2014
(2014)
Morula marginlba: Also known as the
Mulburry Whelk. These are predators of the
intertidal zone feeding on oysters, barnicles,
limpets and other gastropods. The spiral
rows of noudules are said to look like
mulburies, giving this species it’s common
name. They usually grow to around 20mm
but have been seen upto 35mm in length.
Their shells come in different shades of
brown, grey and black. Will not be found
where there is intense wave action
(Manning.F.2014).
Cypraea caputserpentis: The Sperpents
Head Cowrie is found in the intertidal zone
near tropical reefs. It’s shell is oval, shiny,
smooth and brown with white bloches. It’s
underside it light in colour with it’s appeture
looking like teeth. This species does not like
the light and is normally found under rocks.
They can be seen feeding on algae or coral
animals including sponges and small
crustaceons after dark ( Wong.S.Y. 2014)
Athousis.C. (2011)
Acanthopleura gemmata: Also known as a
Chilton. This species is quite unique in
appearance with 8 overlapping plates acting
as a shell. They can grow to roughly 12cm,
but have been seen upto 14cm in length.
They are found attached to rock in littorial
zones grazing on microflora. They returne to
a ‘home scare’ everynight but it is unclear
how they find their way back as they have no
cephalic eyes. It’s believed they may use light
recreptors in their shells to ‘see’. Chilton
were used by Aboriginals as food. If
disturbed the Chilton will roll up in a ball
simlar to an armadillo (Athousis.C. 2011).
INTERTIDAL ZONE IN THE GREAT BARRIER REEF
4
Intertidal Environments: The Reef Crest
Macroalgae
Exposed reef tops are home to an abundance
of life, often including a rich algae layer
(Zell.L.,2012).Macroalgaes, also known as
seaweeds, come in 4 different varieties; Bluegreen Algae, Red Algae, Brown Algae and
Zooxanthellae ( Marine Education Society of
Australia, 2004). Species of algea on the
Great Barrier can range immensly in size
from just millimeters to 3 or 4 meters high.
Each different algae species proforms a
different role in the reef ecosystem which
would not survive without these algae.
Species of algae can be seen growing on
rocks and water surfaces in the intertidal
zone (Marine Education Society of Australia,
2004). A species of Red Algae (picture below)
is one of these algaes.
Reef Crest (Zell.L.,2012)
Intertidal sponge (Zell.L.,2012)
These organisms have to withstand great
forces from waves every day and must have
firm attachment to the surface below them.
They are also exposed to weather and events
such as cyclones with often leave the reef in
servere damage.
Similarly to the invertebrates that live on the
rocky shores, these organisms have had to
adapt to their exposure to the air and sun.
when they become exposed at low tides the
soft part of the coral, called the polyp, are
retracted using the harder skeleton of the
coral as protection (Zell.L.,2012). The coral in
the picture to the left has secreted a purpled
protective mucus. This is an adaptation to
help provent the coral from becoming burnt
and is used by many species (Zell.L.,2012)
Red Algae (Moetary institute for Technology and
Education, 2015)
Algaes provide a major resourcee for a range
of organisms forming the base of the reefs
eosystem. Not only do they fuel the basis of
life on the reef they also are vital for some
orgnaisms as protection including many of
the Malacostraca listed on page 2. As plants,
algae undergo photosyntheseis, removing
CO2 from the water and replacing it with O2.
They also trap nitrogen from the water in
their structure with makes it available for
hebivors who would other wise not be able to
injest this, and other, nutrients (Great Barrier
Reef Marine Park Authority, 2008).
The reef crest is located between the Back
Reef and the Buttress Zone. It’s a raised part
of the reef that protects the lagoon and
shorelines from the force of the
waves(Queensland Museum Network, 2015).
It can become exposed during low tide
making it an intertidal environment. It is
compromised of n intertidal algae pavement
and a coral shingle zone (Queensland
Museum Network, 2015). There are many
different species of coral, sponges, algae and
many other found in this environment.
Exposed coral with protective mucus (Zell.L.,2012)
The Parrot Fish have specially designed heads and beaks to scrape away at corals forming
sights for new corals to settle (Kerry.J. 2013). Below is an image Taken by the Living
Oceans Foundation of a school of Bolbometopon muricatum swimming across the reef crest
below the waves.
Algaes found in the intertidal zone are
usually more ridged and fleshy than other
species. They form distinct lines on the rock
beds acording to the littorial levels they
function in. There are usually a diverse range
of algaes found, but populations are usually
sparse (Great Barrier Reef Marine Park
Authority, 2008
Picture retrieved from: http://www.livingoceansfoundation.org/photo/great-barrier-reef-album/