There
are so many beautiful coral
reef
animals in the waters around Australia.
Coral reef is, along with tropical rainforests, one of the
species-richest ecosystems on the Earth.
It's a colourful ecosystem and
there are some incredible creatures
amongst coral reef animals.
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Why
are Coral
Reefs Important?
All ecosystems are important, but the more species-rich an ecosystem
is, the more species would go extinct if it collapsed. Coral reef
ecosystem is one of the most complex and species-rich ecosystems on
Earth.
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Coral Reef Ecosystem is Species-rich but Poor on Nutrients
Coral reef is an ecosystem so species-rich that it has been compared to
tropical
rainforests. An interesting thing about both rainforests and
the coral reef biome is that neither is rich in nutrients. Rainforest
soils are very nutrient-poor, and so is the water around corals. So how
can they manage to be so species-rich? In the rainforests, the answer
is the quick production (of debris and other food on the different
levels in the food chain) while in coral reef the secret is zooxanthellae
– corals’ vital bacteria which, being a plant, uses sunlight and CO2
to
produce a lot of energy via photosynthesis.
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Where Are Coral Reefs Found - Coral Reef Habitat
And there is no shortage of sunlight - coral reef only grows in the
areas of maximum sunlight. This also means corals grow in relatively
shallow waters, where the light can reach them; and they need clean,
clear water for the sunlight to reach them. This is why corals tend to
grow a bit out to the ocean and not immediately on the shoreline where
rivers carry muddy water to the ocean.
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Where
Are Coral
Reefs Located
Corals also require certain water temperatures. This is why coral reef
ecosystems are mainly found in
the latitudes between 20 and 30 degrees; and which is why they are a
very
vulnerable ecosystem to global
warming.
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Global
Warming
and Coral Reefs
When the water gets too hot, zooxanthellae
will die (which causes so-called coral reef bleaching)
and the whole coral reef biome will collapse because no energy is
provided through photosynthesis, and no food is provided by
zooxanthellae to the first level in the coral reef food chain. Coral
reef bleaching is one of the biggest threats to coral reefs, and
preventing global warming is the best way of protecting coral reefs.
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Plants in Coral Reefs
There are other typical coral reef plants though in the coral reef
ecosystem. Seaweeds (algae) and seagrasses
(a favourite food of dugongs)
provide food to the lower levels in the food chain, along with some
tiny
single-celled animals that belong to the Phylum Sarcomastigophora.
Other simpler animals in the coral reef are sponges
(Phylum Demospongiae). Sponges have a very simple
but
effective body structure and they are very efficient filter feeders.
The 10,000ish known species of sponges have changed very little since
Devonian
period when they were the
dominant animals in shallow waters.
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Colorful Jellyfish and other Coral Reef Animals
And then there is the group of stinging animals which you want to keep
away from while in the water. They are all related to each other and
they all have the same stinging cells, called nematocrysts. First,
there is the jellyfish.
Many species of jellyfish
all over the world sting, but no other jellyfish stings like the
infamous Box Jellyfish
(Chironex fleckeri), infamously the most poisonous
animal in
the world. Then there are hydrozoans -
colonial, plant-like animals of Phylum Cnidaria which amongst others
include bluebottles and fire corals. And finally, there are the sea
anemones, famous as homes for the Clown Fish (Amphiprion
sp.), which has somehow adapted to tolerate the sea anemones’
stinging
cells and
can therefore have the habitat all for themselves.
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Coral Reef Animals: Hard Corals
And then of course, there are the corals themselves. There are two
types of corals: hard corals and soft corals. Hard Corals, also called scleractinians,
are mostly colonial animals that most often rely on zooxanthellae for
their energy, and are therefore found in clear
and shallow waters to enable the photosynthesis of zooxanthellae. There
are a few exceptions which kill small animals
with their stinging cells for feed and are therefore not tied to clear
waters.
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Coral Reef Animals: Soft Corals
Soft Corals are the most spectacular ones, they can be much more
colourful than hard corals, and they are as most beautiful deeper down,
probably at 30 metres depth. Soft corals don’t have the limestone
exoskeleton, instead they have fleshy tissue and an internal skeleton.
Soft corals also include sea pens, sea fans and sea whips, some of
which can be stingy.
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Coral Reef Animals: Coral Reef Crabs
Class Crustacea
is an interesting group of animals that inhabit the coral reef as well
as other marine ecosystems. They all have a rigid, external skeleton,
and they belong to the Phylum Arthropoda which also
includes insects, spiders, scorpions, centipedes and millipedes. The
majority of Crustaceans have 10 legs and are therefore called decapods.
These include shrimps, lobsters and crabs. The non-decapods include
barnacles, copepods, ostracods, mysids, isopods and amphipods.
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Coral Reef Animals: Other Coral Reef Creatures
Clams and sea shells belong to the Phylum Mollusca
and they can be some of the coral reef’s most beautiful and colourful
creatures. Bivalves include the massive
giant clams,
and while the
gastropod molluscs are smaller, they can also come in impressive shapes
and colours. Some of the common gastropods
are limpets, nerites, periwinkles,
creepers, strombs, moon shells, cowries, dog whelks, volutes,
augers, mitre shells, helmet shells, trumpet shells, turban shells,
murex shells, olive
shells and cone shells. Cone shells are poisonous so don’t touch them.
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Coral Reef Animals: Blue Ringed Octopus
Cephalopods,
nudibranchs
and sea slugs also belong the molluscs and they can also be amazingly
colourful. Nudibranchs of the coral reef
can grow fairly large and come in very bright colours. Cephalopods
include cuttlefish, squids, octopus and nautilus – the animals known to
eject ink when threatened. The Blue-ringed Octopus
(Hapalochlaena sp.) is highly venomous and well able
to kill humans.
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Coral Reef Animals: Sea Stars
And then there are the stars. Sea stars
are the most famous group of stars, with some colourful and spectacular
species, all perfectly symmetrical. Sea Stars have an interesting
feeding habit – they climb to the top of their prey, pull out the
stomach and start digesting. The group also contains the infamous
crown-of-thorns
starfish which eats corals. Crown-of-thorns have poisonous
spines so you don’t want to pick them up (as opposed to most other sea
stars that are harmless). Close relatives of sea stars, Brittle
Stars include Basket Stars and Serpent Stars. Feather
stars, also called crinoids, are
colourful
feathery stars that are filter feeders.
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Coral Reef Animals: Other Coral Reef Creatures Sea Urchins are beautiful creatures
although you don’t want to step on one. The body of a sea urchin is
mostly hollow inside,
and its long and sharp spines are poisonous – it won’t kill you but it
hurts. Sea Cucumbers, properly called
Holothurians,
are big worm-shaped
animals that eat sand from which they digest organic material and then
poo the rest out. Other creatures of a coral reef ecosystem include
Ascidians (Order Chordata),
the moss-like Bryozoans,
and the very variable group of marine worms, which consists of
segmented worms (Phylum Annelida) and flatworms
(Phylum Platyhelminthes)
– some species of the latter look like colourful nudibranchs.
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Coral Reef Animals: Coral Reef Fish
One of the largest groups of animals in the coral reef ecosystem is the
coral reef fish, which are often colourful to mix into the colourful
coral reef environment. First, there are the sharks,
rays and eels. Other large
fish include the impressive groupers and basslets – some of the reef’s
largest fish.
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Coral Reef Animals: Smaller Coral Reef Fish
Other, smaller fish include the territorial Damselfish (Pomacentridae)
which for large schools around corals; the colourful Wrasses (Labridae)
that live in all reef environments and eat small invertebrates; and the
spectacular Butterflyfish
(Chaetodontidae) – probably the most known of all
reef fishes, which live in permanent life bonds and are often seen in
pairs. Close relatives to the Butterflyfish are the large and beautiful
Anglerfish (Pomacanthidae).
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Coral Reef Animals: Other Coral Reef Fish
Cardinalfish
(Apogonidae) belong to the largest group of
nocturnal coral reef fishes in the Indo-Pacific. The algal-feeding
Parrotfish (Scaridae)
are related to wrasses and they spawn in a similar way. Surgeonfish (Acanthuridae)
which are often seen in large schools have got their name from the
sharp scalpel-like structure on the tail base. Small fish that are not
so easily seen are small Blennies (Blenniidae)
and Gobies (Gobiidae)
that are both bottom-dwellers.
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Coral Reef Animals: Dangerous Coral Reef Creatures
There are also a few dangerous creatures in the coral reef, including
the
already-mentioned sharks,
jellyfish,
cone shells, blue-ringed
octopus and sea snakes. There are about 50 species of the sea snakes in
the Indo-Pacific coral reefs and many of them are deadly poisonous.
Ashmore Reef in Queensland
is known to be the
world’s sea snake capital – 12 species have been encountered. Other
dangerous creatures to be aware of are Lion fish,
Fire fish and Stonefish – the latter sits on the
ocean bottom, looking like a stone, but if you happen to step on it, it
will inject some deadly toxins into your foot, so it is safest to wear
special rubber boots which you can buy in any diving shops.
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Other Coral Reef Animals
Other animals that are found in and around coral reefs include turtles,
whales
and dolphins. Many islands
of the Great
Barrier Reef are inhabited by
large amounts of sea birds such as mutton birds and noddies which form
large flocks that can get very noisy.
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Visit the Coral Reef in Australia
The best way to explore the coral reef is to go diving and snorkelling,
but if you don’t want to get wet, there are always many tour operators
that can take you to the reef on glass-bottomed boats where you can
discover the reef.
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Where Else to See the Coral Reef in Australia
Many Australian aquariums have coral reef, but one great place is the
Reef Headquarters
in Townsville
in north
Queensland.
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