REEF FACTS: Plants and Animals on the Great Barrier Reef

30 species of whales, dolphins and porpoises live in, or visit Great Barrier Reef waters

Dwarf minke whales visit the Reef every year in June and July. They are baleen whales, which means they feed by straining tiny plankton and krill through comb-like plates on their upper jaws. No-one knows where they come from, or why they gather here.

Humpback whales also pass through every year. They are the fifth largest animal in the world, as big as 600 people. 

Irrawaddy and Indo-pacific humpback dolphins live close to the coast of Queensland all year round. They feed on fish in shallow waters, especially in estuaries or river mouths.

Some of the largest populations of dugongs  in the world live on the Great Barrier Reef

Dugongs grow to about 3m long, can weigh 400 kg and live to 70 years old. Dugongs are more closely related to elephants than they are to other marine mammals such as whales or dolphins.

Dugongs have a single calf when they are between 6-17 years old and then have calves only once every 2.5 – 5 years.

Dugongs eat seagrass, and actually 'farm' tasty types of seagrass by cropping their preferred plants.

Over 200 species of birds (including 40 species of seabirds) live on the Great Barrier Reef

White-breasted sea eagles live on the coast and islands. They find it hard to take off from the water, so they fish by snatching their prey from the water's surface.

The Roseate tern migrates from the islands of the Great Barrier Reef as far as Japan, and is protected by the Japan Australia Migratory Birds Act.

Raine Island is one of Australia's most significant seabird rookeries and has the greatest number of nesting species (17).

Six breeding species of sea turtles live on the Great Barrier Reef

Six of the seven species of sea turtles in the world are found on the Reef: Green, Leatherback, Hawksbill, Loggerhead, Flatback and Olive Ridley.

Sea turtles lay their eggs in sand. The temperature of the sand determines the sex of the young turtles. Cooler sand produces male turtles, while warmer sand produces females.

Sea turtles can lay up to 100 eggs at a time.

They become sexually mature at 30-50 years and can live for up to 100 years.

Hatchlings are carried out to sea on ocean currents, and can travel thousands of miles around the ocean before they are fully grown. When they reach breeding age, they return to the area where they hatched to lay their own eggs.

The Leatherback is the largest sea turtle. The heaviest Leatherback turtle ever measured weighed 916kg.

14 species of sea snakes live on the Great Barrier Reef

The sea snakes we see today have evolved from snakes who lived on land, but the ancestors of all snakes probably evolved in the sea about 135 million years ago.

Sea snakes have to come to the surface to breathe, but can spend up to 2 hours underwater between breaths.

1500 species of fish live on the Great Barrier Reef

Some baby anemone fish can swim at 9.5 body lengths per second just 24 hours after hatching (the Olympic swimmer, Ian Thorpe, can only swim at 2 body lengths per second).

The oldest fish on the Great Barrier Reef would probably be a red bass which can live to more than 50 years old.

The biggest fish on the Great Barrier Reef would be the visiting whale shark which can grow to about 12m long.

Five of the seven species of coral trout occur on the Great Barrier Reef. Coral trout change sex as they grow – they start life as females and become males as they get larger. The average length at sex change is 42 cm. Common coral trout can live for about 16 years.

All fish have ear bones called otoliths. They grow every year and can be read in the same way as tree rings. Scientists can use these bones to find out how old the fish was, and even what its habitat was like.

The seahorse is the slowest horse, and takes about 2.5 days to travel one kilometre.

5,000 species of molluscs live on the Great Barrier Reef

Giant clams can grow to be more than 1 metre long and can be at least 70 years old. They are the largest bivalve mollusc that has ever existed on the planet.

Most giant clams are simultaneous hermaphrodites – the same animal is both sexes at the same time. The largest pearl in the world was found in a giant clam and sold in New York for about $10 million.

Cone shells shoot their prey with a modified tooth. They can be highly poisonous and a few species (which usually eat fish) are harmful to people.

Nudibranchs are a type of sea snail which only have a shell when they are tiny larvae. Adult nudibranchs have a multi-coloured mantle instead of a shell. The bright colours warn predators to stay away.

Molluscs have feathery gills through which they can absorb oxygen from the water.

Octopus, cuttlefish and squid are also types of mollusc.

400 species of coral  live on the Great Barrier Reef

Corals are colonies of made up of tiny animals called polyps. Hard corals have polyps with 6 tentacles, or multiples of 6 tentacles. Soft coral polyps have 8 tentacles.

The oldest coral on the Great Barrier Reef would be a Porites sp. and is probably about 1,000 years old. Old colonies of this species are the size of a small room. These corals grow at about 1 cm in height per year and their skeleton reflects the weather conditions at the time of the growth. Hence large corals which are hundreds of years old can provide information about water temperature and rainfall patterns that pre-date European settlement.

Tiny algae called zooxanthellae live in the flesh of most corals. The algae photosynthesise and transfer energy to the coral. Therefore, coral reefs (which are built mostly by these corals) are generally confined to shallow waters because like other plants, the algae require light to survive.

Coral spawning happens on only a few nights of the year. Corals release their eggs and sperm into the water, where they will either meet and be fertilised, or become food for other Reef animals.

Of some 60 species of seagrass  around the world, there are 30 in Australia and 15 in Queensland waters.

Seagrasses are different to seaweeds and algae because they have true roots and are flowering plants. Seagrasses are the only flowering plants in the sea. They are important food for turtles and dugongs.

Some seagrass meadows are so extensive they can be seen from a space shuttle orbiting earth.

500 species of seaweed or marine algae live on the Great Barrier Reef

Most seaweeds are not poisonous to humans but a few, such as Caulerpa, are poisonous to grazing animals and so, survive on the reef without being eaten.

Seaweeds contain many compounds useful to humans: carrageenans or agar (from red seaweeds) or alginates (from brown seaweeds) are used in ice cream, instant puddings, salad dressings, printers ink, cosmetics, in pharmaceuticals and to coat pills.