By Underwater Earth
Learn about this awe-inspiring coral reef environment and meet its fascinating marine creatures.
Lady Elliot Island
For this underwater expedition, we’re heading to Australia's Great Barrier Reef, the largest living structure on the planet and a UNESCO World Heritage Site. This vast expanse of natural beauty stretches along Australia's east coast for 2,300 kilometres (1,429 miles).
[Tap and drag to look around the reef]
In fact, it’s so large that it can even be seen from outer space! We're going to dive in at the southernmost point, which is Lady Elliot Island. This island is a significant seabird breeding site.
This incredibly complex natural ecosystem is a mosaic of diverse species with brilliant colours, shapes and textures. In order to protect such a special place, in 1975 the Great Barrier Reef was declared a Marine Park.
The Great Barrier Reef Marine Park contains 3,000 coral reefs, 600 continental islands, 300 coral cays and about 150 inshore mangrove islands. The region’s large maze of colourful reefs and intricate architecture provides a home for a huge number of plants and animals.
The shallow waters just off the shore of Lady Elliot Island are a great place to start exploring. There are always plenty of turtles to see around here!
Clownfish are one of the most recognisable species on the Great Barrier Reef, made famous from “Finding Nemo”. There are over 25 different species of clownfish. They’re also called anemone fish because they have a symbiotic relationship with the anemones they inhabit.
Lady Elliot Island Manta Rays
The Great Barrier Reef is one of the seven wonders of the natural world. One of the reasons it is so spectacular is the astounding marine life that can be found all along the Reef.
Lady Elliot Island is known as the “Home of the Manta Ray” and it’s one of the best places in the world to encounter these graceful ocean giants.
All manta rays have unique markings on their undersides, which can be used to distinguish individuals from one
another, similar to fingerprints on humans. This particular manta ray has been named Venus because of its distinctive “V” belly markings.
Unlike other rays, such as the aptly-named stingrays, mantas don't have stinging barbs on their tails so are completely harmless to humans. They are filter feeders and use their mouths to strain plankton from the water.
Manta rays have one of the highest brain-to-body ratios of all the
fish in the ocean. Their high level of social interactions and curiosity
towards humans illustrates a reasonable level of intelligence.
Even though their individual colouration and markings are unique, the majority of manta rays have white bellies with dark spots. This means it is always extra special to see the rarer mantas with black colouring almost all over.
The Serene Gatekeeper (2012) by Christophe BailhacheUnderwater Earth
Our next stop is another island in the southern region, Heron Island. The Great Barrier Reef is home to six of the world's seven species of turtles and Heron Island is a significant nesting location for two vulnerable species, the green turtle and loggerhead turtle.
Turtles are often called the ancient mariners of the sea because they’ve been swimming the ocean for over 150 million years, first appearing in the age of the dinosaurs!
Green turtles like these are the most abundant of all the Great Barrier Reef’s turtle species. Their name comes not from their shell, which is usually brown or olive, but from the color of their cartilage and fat.
All turtles make incredibly long migrations from their feeding grounds to their breeding grounds. Male turtles never leave the ocean, but female turtles will return to the beach where they were born to lay their eggs in the sand.
Turtle hatchlings have to endure a treacherous journey from their nest on the beach to the water's edge and the predatory dangers of the open ocean. Only about 1 in 1,000 hatchlings make it to adulthood.
Loggerhead turtles are the largest of all hard-shelled turtles (leatherbacks are bigger but have soft shells). You can spot a loggerhead by their massive heads, strong jaws, and a reddish-brown carapace (shell).
In the central region of the Great Barrier Reef lies Myrmidon Reef, surrounded by colorful reef fish. In Greek mythology, the Myrmidons were Achilles' fierce and loyal warriors. Perhaps the enduring and ancient nature of this reef led to its name.
The Great Barrier Reef has a hugely diverse range of fish. Roughly 1,625 species have been discovered so far, reflecting all sorts of shapes, sizes, and colors of the rainbow.
Shoaling or Schooling
Fish group together like this in what’s known as either a "shoal" or a "school." Shoaling is when fish swim close together, but individuals do their own thing. Schooling is when fish swim synchronised in a tight formation.
Safety in Numbers
One reason fish swim in schools is to gain protection from predators. In a group, there are more eyes looking out for threats. Schooling can also confuse and disorient predators into thinking a school is a larger fish.
Schools of fish can often attract visitors, like these bottlenose dolphins, coming to see if they can catch a meal among the coral reef marine life.
On our journey up the Great Barrier Reef, we have to stop at one of the most famous shipwrecks in the world, the SS Yongala. Consistently rated as one of the "top 10" dive sites in the world, this over 100-year-old shipwreck is brimming with life.
In 1911, the luxury passenger vessel SS Yongala disappeared in a tropical cyclone south of Townsville, Australia. Over 100 people were on board, and none of them survived. The wreck site was not discovered until 1958.
Popular Dive Site
Much of the ship's structure is still intact. The wreck is 109 meters long and lies at 30 meters depth, although the upper section is only 16 meters below the surface.
Since sinking, the ship has become encrusted in many different coral species, such as this brain coral here. It’s now a thriving artificial coral reef habitat, and attracts an abundance of marine life. See what animals you can spot!
There’s a strong ocean current running along the shipwreck, which contributes to why there is so much marine life here. Rays, like these bull rays can often be found cruising in the current.
For the next destination on our Great Barrier Reef journey, we’ll head north to meet one of the Reef’s friendliest residents, the potato cod.
The Cod Hole was one of the first ever protected sites on the Great Barrier Reef thanks largely to the efforts of famous underwater photographers Ron and Valerie Taylor, who in the early 1980s witnessed the huge cod population decimated by overfishing.
Friendly Potato Cods
Friendly Potato Cods
This is one of the most famous dive sites on the reef because of the potato cod population here. They happily approach divers and their extremely friendly nature has earned them the nickname "the dog of the sea".
These cod are a bluish-grey color and have potato-shaped markings all over their body, which is why they’re named potato cod. However they are a bit bigger than potatoes, growing up to two metres (seven feet) in length.
Opal Reef, in the northern region, is one of the sights that have made the Great Barrier Reef so famous. It’s easily accessible by tourist boats and the colorful coral reef here is visited by many thousands of people each year.
Corals are the backbone of coral reef ecosystems. Even though they can look like rocks, corals are all living animals, made up of tiny coral polyps. They essentially build the infrastructure that other species call home.
Corals come in all shapes and sizes. Some are as flat as plates, some have fingers that reach up into the water, and some are big and round and can look similar to rocks.
Even though coral reefs cover less than 1% of the earth's surface, they support 25% of all marine species. They also provide food and livelihoods to over 500 million people worldwide.
Christmas Tree Worm
Christmas Tree Worm
Amongst the corals, there are always fascinating creatures to be found. Christmas Tree Worms like this live with their body inside a tube in the coral and protrude their pair of plumes or “crowns”, to catch food and for respiration.
Moray eels are usually found hiding in crevices in the coral reef, lying in wait for unsuspecting prey. They haven’t got very good eyesight but their tube-like extensions on their nose allow them to “taste” the water for chemical cues.
North Broken Passage
North Broken Passage is in the far northern section of the Great Barrier Reef, more removed from human activity. This region’s reefs tend to be incredibly biodiverse and healthy, with plenty of big fish, sharks, and other marine creatures.
But it’s not just biodiversity that makes the Great Barrier Reef such a complex ecosystem. It’s also the interconnectedness of species and habitats. Any disturbance to this underwater world’s delicate balance could create a domino effect throughout the ecosystem.
What makes the Great Barrier Reef such an exceptional wonder is its vast expanse of coral reef. Look how much of this wall in North Broken Passage is covered in different species of colorful coral, providing habitats to numerous reef creatures.
The Great Barrier Reef is home to 600 types of corals, 1,625 species of fish, over 100 species of jellyfish, 3,000 varieties of molluscs, 133 varieties of sharks and rays, and over 30 species of whales and dolphins.
Natural Wonder of the World
When you look at such a complex and productive coral reef ecosystem, and consider the huge scale of this living structure, it’s easy to see why the Great Barrier Reef is one of the natural wonders of the world.
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AXA XL, The University of Queensland, Google, UNESCO, Lady Elliot Island Eco Resort, Panedia, Fourth Element