Coral Reef Animals

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.

Heart-Shaped Reef, Hardy Reef, Near Whitsunday Islands, Great Barrier Reef, Queensland, Australia
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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.

Great Barrier Reef, Australia
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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.

Hardy Reef, Great Barrier Reef, Queensland, Aust
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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.

Aerial View of Great Barrier Reef, Queensland, Australia
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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.

Overhead of Heart Reef, Great Barrier Reef, Australia
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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.

Aerial View of Hardy Reef, Great Barrier Reef and Sea, Queensland, Australia
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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.

Box Jellyfish or Sea Wasp, Poisonous, Australia
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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.

Spinecheek Anemonefish, Bulb-tipped Anemone, Great Barrier Reef, Papau New Guinea
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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.

Diver and Soft Coral, Great Barrier Reef, Queensland, Australia
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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.

Diver Examines Coral Reef, Great Barrier Reef, Australia
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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.

Ghost Crab on Beach in Cairns, Queensland
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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.

Diver and Giant Clam in Coral Reef, Great Barrier Reef, Australia
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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.

Diver with Pair of Pearly Nautilus, Great Barrier Reef, Queensland, Australia
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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.

A Starfish in a Tide Pool on Australias Great Barrier Reef
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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.

Sea Cucumber with Feeding Tentacles Extended, Pseudocolochirus, Australia
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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.

Schooling Lined Sweetlips, Great Barrier Reef, Australia
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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).

Schooling Bigeye Snappers, Great Barrier Reef, Australia
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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.

Anchovies, Great Barrier Reef, Australia
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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.

Grey Reef Shark (Carcharhinus Amblyrhynchos), Great Barrier Reef, Queensland, Australia
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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.

Turtle Underwater, Australia
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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.

Low Isles on Great Barrier Reef, Port Douglas, Australia
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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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