The Great Barrier Reef

Comprehension Activities

Visit the Great Barrier Reef: https://www.youtube.com/watch?v=DygyYL4dylU
Responsible Reef Practices: https://www2.gbrmpa.gov.au/access/responsible-reef-practices

It’s one of the seven natural wonders of the world… the only living thing visible from space … and experts are worried it’s in danger. This is your Squiz Kids Shortcut to the Great Barrier Reef—the podcast where we dive into the who, what, when, where, why and how of the big news stories. I’m Amanda Bower.

And I’m Bryce Corbett.

Bryce, every year two million people visit the Great Barrier Reef to experience all that the massive marine national park has to offer. But lately on Squiz Kids, we heard that experts from the United Nations had come to study the health of the reef, and were recommending that it be officially listed as “in danger”.

That’s exactly right. Today, we’ll take you through WHY the Great Barrier Reef is so famous; WHAT exactly is a coral reef; and HOW one of Australia’s top tourist attractions is in trouble.

Listen carefully – there’s a Squiz at the end!

Bryce, the Great Barrier Reef is the world’s largest coral reef, and the national marine park is bigger than the states of Victoria and Tasmania, combined!

It takes up 344,000 square kilometres, and extends from the northern tip of Queensland all the way down to just north of Bundaberg.

That’s 2,300km long… if you wanted to drive that far, and if you were able to speed at 100km/hr without stopping for petrol, a sleep, or a wee, it would take you 23 hours!! So one reason the Great Barrier Reef is famous is that it’s just so BIG. Of course, that’s in the name.. “GREAT”. But that’s not all! This massive reef system contains not just 600-plus types of soft and hard corals, there are also 1625 types of fish…

…3000 varieties of molluscs – that’s a fancy word for shells...
…500 species of worms
…133 varieties of sharks and rays
…more than 100 types of jellyfish
…and more than 30 species of whales and dolphins.

Humpback whales come to the Great Barrier Reef all the way from chilly Antarctica. When they arrive in the warmer waters off the Queensland coast in May, they date, mate, and have their babies before heading back in September.

I’ve heard of lots of humans having their honeymoon in Queensland, but I guess it’s a place that attracts other species, too!

Remember how we talked in our Squiz the World trip to Costa Rica about biodiversity? It’s the number of different plants and animals in a place… and the Great Barrier Reef is precious because of the extraordinary diversity of marine life. It is SO beautiful underwater, incredibly colourful coral, teeming with fish and shells and my personal favourite creature name, nudibranchs. I’ll put some video links into your episode notes so that you can get a sense of what the two million tourists who travel there each year are able to see. Of course, those tourists create about 65,000 jobs for people … as tour boat operators, restaurant and hotel staff… and then of course there are all the jobs created for scientists who study the reef, too.

Now Amanda, you said that the Great Barrier Reef was the only living thing visible from space… which made me realise that I might need some more information on WHAT, exactly, is a coral reef?

Squiz Kids, did you think coral was a mineral, like a rock, because you’ve touched a piece and it’s super hard and scratchy?

… or maybe you thought it was a plant, because they sure do look like trees and shrubs growing on the ocean floor?

Well, actually, corals are alive, so they’re not rocks. And they don’t make their own food, like plants. That means they’re animals! Each single coral animal is only about a centimetre and a half big, and it’s called a polyp. Those branches or blocks of coral we see are really colonies of hundreds or thousands of tiny polyps all living next to each other. The polyps secrete – a word that means produce – an outer skeleton of limestone, and that’s what feels hard to the touch. The skeletons attach onto rocks, as well as the skeletons of dead polyps, to form those incredible coral colonies.

Amanda, I remember learning in primary school science that living things MOVE, but if coral is attached onto rocks, it doesn’t move, does it?

Actually, coral polyps do move. They have tentacles that they stretch out to sting and capture tiny plankton – that’s their food. They can also pull those tentacles back into the hard shell of the coral if they’re threatened!

I also remember that all living things reproduce… so how do mummy and daddy corals make babies?

I am SO glad you asked, Bryce, because this is one of the coolest things about the Great Barrier Reef. Most corals don’t have a mummy and a daddy, because one coral polyp can produce both sperm and eggs. And every year, and only once a year, coral colonies have what’s called a “mass spawning event”. Polyps release tiny egg and sperm bundles into the water, all at the same time, to increase the likelihood that fertilisation will happen. Now this mass spawning looks like a massive snowstorm in the water. It only happens at night, it only happens after a full moon, and it’s only after the water has warmed up to a temperature that stimluates the coral to get going.

I remember talking about this on Squiz Kids Today! The spawning lasts up to a week, because different species of coral release their
eggs and sperm on different days, to prevent hybrids from being produced.

That’s right! And it happens at different times on the reef, depending on the depth of the water, and other factors. Once an egg is fertilised, it develops into coral larva, which I’d love to call a baby, but the proper scientific word is a planula. The planula floats around in the water for a few days before it settles on the ocean floor, starts to grow, and a new colony develops.

What an amazing system! How, then, are these amazing coral reefs in trouble?

Well, Bryce, over the past few years there has been some coral bleaching events on the reef. If you bleach your hair or clothes, they turn white… and that’s what’s happened to the coral – it’s lost those incredible colours and become a dull, lifeless white.

The main reason that happens is when water temperatures get too warm… something that’s happening with climate change.

That’s right. The United Nations sent a team of ecosystem experts from lots of different countries to Australia late last year to look at the reef, and find out how much damage has been done by climate change as well as other environmental factors, such as run-off – which is when the water becomes polluted by human activity in towns on the coast and things like the use of pesticides and fertilizers on farms.

Meanwhile, there are lots of things visitors can do to help protect the reef. If you’re snorkelling or diving, make sure you don’t touch the coral… and be especially careful if you’re wearing flippers, because kicking the coral can do some serious damage

Don’t feed the fish, which can make them sick, and don’t throw food scraps overboard if you’re on a boat.

Check that your sunscreen is “reef safe”, or even better, wear a rashie. There are lots of other ways to be a responsible reef visitor – I’ll pop a link in your episode notes. Because every little thing counts.

The S’Quiz
This is the part of the podcast where you get to test how well you’ve been listening…
1. What’s the name given to one living piece of coral?
2. Which animals come to date, mate, and have babies at the Great Barrier Reef?
3. What happens on the Great Barrier Reef once a year, at night, after a full moon?