The Deep Sea

LINKS:
World Ocean Day smackdown: https://worldoceanday.org/smackdown/
Black hagfish: “The Slimy Creature of Your Nightmares”: https://video.link/w/0Gbvd
Gulper eel: https://video.link/w/yGbvd
Tripod fish: https://video.link/w/yHdvd
The deep-sea snailfish: https://www.nationalgeographic.com/science/article/deepest-sea-fish-identified-snailfish-pseudoliparis-swirei-spd
Deep sea bioluminescence: https://video.link/w/XNdvd

 

EPISODE TRANSCRIPT
Welcome to a place with three-legged fish … snow… and animals that glow in the dark. This is your Squiz Kids Shortcut to the Deep Sea—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, World Oceans Day is on June 8—and for the first time this year, it includes a “World Ocean Day Smackdown”… like a sports tournament bracket between different ocean creatures. I’ll pop a link in your episode notes so you can vote for your favourite—the winner will be announced on June 8. I’m Team Dolphin all the way—although they definitely do NOT live in the deep sea.

Team otter for me! Today, we’ll take you through HOW deep the deep sea really is; WHAT lives there; and WHY bioluminescence is so important.

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

HOW
When I think of the ocean, my first thought is of the beach… and when I go swimming in the ocean, I’m in what’s called the sunlight zone – or, more scientifically, the epipelagic zone. That goes from the water’s surface to 200m down.

200m is 2 NRL fields, from tryline to tryline… imagine diving that deep!

Yep, the sunlight zone already goes pretty deep! It contains dolphins, schools of fish, sharks, and lots of plankton, which makes its own food from the sun.

And what would you see if you went down further than that?

The next zone is called the Twilight Zone… or the mesopelagic zone. It covers the area that is between 200m and 1000m below the surface. This area receives only faint, filtered sunlight, which means that no organisms using photosynthesis – making their own food from the sun – can survive. The animals that do live there often have large eyes, so they can see better in the near-darkness.

So is that the deep sea?

We still haven’t reached the deep sea! We’ve only gone down through about ¼ of the ocean… the remaining three quarters are cold, permanently dark, and sometimes called the midnight zone. The deep sea is more than 1000m deep.

1000m! I’m trying to imagine diving the length of 10 NRL fields

That would be VERY dangerous. Actually, deadly. And not just because you couldn’t hold your breath for that long! The pressure of that much water over you would cause your body to stop working properly.

So special equipment is needed to explore the deepest parts of the ocean. WHAT have they found?

WHAT
The first thing they found was that the deep sea has three different levels, each with its own kinds of creatures. The first, which is from 1000 to 3000m deep, is called the bathypelagic zone. The water is about 4 degrees celsius, and many of the creatures that live there eat snow!

Whaaat?

Okay, technically it’s called marine snow. It’s little flakes of dead and decomposing animals, poo, silt and other organic items washed into the sea from land. Those flakes do look quite a bit like snow falling through the water.

What eats marine snow?

Animals that don’t need a lot of food, and that process food slowly. They usually have squishy bodies and slimy skin… I’ll put a link in your episode notes to two videos. The first is the black hagfish, which has a skull, but no spine… and holes along the side of its body—some for breathing, and some for sliming. When it eats, its mouth makes it look like a creature from a Star Wars cantina. And then there’s the amazing gulper eel, which has a ginormous expandable gullet that balloons out when it’s feeling threatened.

Amazing. What do we find when we go even deeper?

Between 4,000 and 6,000 metres deep, we’re in the abyssopelagic zone. The pressure here is 600 times greater than at sea level, so most of the creatures we saw in the sunlight and twilight zones couldn’t survive here. The incredible tripod fish is one of the ocean’s deepest-living fish species.

Tripod? I only know that word from a camera tripod… those three legs that hold a camera stable at a particular height.

And that’s pretty much what a tripod fish does. It’s about 30cm long, but it has three long, bony fins that can extend out for a metre! Researchers think that they fill with water when the tripod fish wants to “stand” on the deep ocean floor.

And why do they want to stand?

The food they eat is carried by a current… but there’s very little current right at the bottom of the ocean floor. The tripod fins hold its body at a level where the current brings their food to them—they just open their mouths and eat.

Convenient!

The final level is the deepest of the deep… from 6000 metres below sea level, all the way down to the deepest part of the ocean, the Mariana Trench, at 10,994 meters. That’s 10 KILOMETRES from the top of the ocean!

Wow…

Not much is known about what lives down here, but in 2018, scientists officially declared a new species of fish, the deepest ever found. It’s a type of snailfish – and get this, Bryce – it’s about 30 centimetres long, but it can handle water pressure that is the equivalent of 1,600 elephants standing on its head.

That’s incredible!

Bryce, there are so many more incredible things about the deep sea. Like… super salty lakes at the bottom of the ocean… hydrothermal vents, where scalding water spews out of cracks in the earth’s crust… deep-sea reefs… animals that produce their own light in the pitch black water.

I wish this podcast could go for an hour, so we could talk about all those things… but I am especially intrigued by bioluminescent animals – bioluminescent meaning that they produce their own light. WHY is that so important in the deep sea?

WHY
It’s a pretty cool ability, isn’t it, being able to make yourself glow in the dark? Video footage from the deep sea actually looks a bit like a starry sky, there are so many animals lighting themselves up. Many have evolved to have this ability to help them catch food. My favourite is probably the deep sea anglerfish, because it has a glowing lure that bobs back and forth on the top of its head to attract prey. Once they come to take a bite, it opens its enormous jaws and … CHOMP.

I’m guessing that another reason to glow in the dark is to attract a boyfriend or girlfriend… the same way land animals do flashy things, like a peacock spreading its colourful feathers.

100%. But some also do it to scare other creatures off – a sudden burst of light might scare or distract a predator enough that you can avoid becoming its dinner.
I’ll put a link in your episode notes to a video from none other than Sir David Attenborough, that shows some examples of the different bioluminescent creatures in the deep sea… some of them have never been caught, studied, and identified!

The Deep Sea… it’s a mysterious place.

The S’Quiz
This is the part of the podcast where you get to test how well you’ve been listening…
1. Many deep sea creatures eat flakes of food called what?
2. What’s the name of the fish that has three long fins that help it stand?
3. What’s one reason that bioluminescence is important to deep sea creatures?