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Chapter 1: What is the main topic discussed in this episode?
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What happens when a whale dies? For these majestic giants of the ocean, and for the entire ocean around them, every death is a big deal. So where do they go? And what happens to their bodies? Well, scientists recently discovered the biggest whale graveyard in the world, and it's not too far off the coast of Western Australia. So let's start there. This is Lab Notes from ABC Radio National.
I'm Jonathan Webb, and today I'm speaking with Peter de Krijp, who's the environment reporter in our own Radio National Science Unit. G'day, Peter. G'day, Jonathan. We're going to be talking about whale remains and whale bones and things today, but they're such beautiful big animals. I want to start in the land of the living. What's the closest you've ever been to a whale?
Well, I've been pretty close to a whale shark, which is not technically a whale. Otherwise, it's been very much from the shore or from a boat. And that must give you a sense of just how big some of these amazing marine creatures can be.
Yeah, it's quite frightening. It's like if a plane became sentient and covered in skin and just jumped into the ocean and started flapping about.
Well, you have been covering this story of the biggest whale graveyard that's ever been discovered. Let's start... I guess at the beginning of that story, the death of a whale is given this wonderful name, a whale fall. How does this happen?
Yeah, it's always kind of got this ethereal kind of vibe from that name. But a whale fall happens when a whale dies, either from natural causes or unfortunately from boat strike. You know, about 20,000 to 30,000 whales die or are injured every year from whale strikes. Gosh, wow. But death is not the end. The whale, you know, it's huge. It's got very big bones.
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Chapter 2: What happens when a whale dies?
It's just massive. And it eventually falls down to the bottom of the seafloor where really large scavengers, hagfish, sleeper sharks, if you've heard of the Greenland shark, those sort of creatures that specialise in deep water environments, they come in, they start eating all the soft tissues of the whale over months and months.
So there's sort of waves of different types of life that come over and make the most of this huge deposit on the floor of the ocean.
Yeah, this whole sort of second life, if you would, of a dead whale occurs where it basically starts to nourish the rest of the ocean. And so after you have all these big predators come in and scavenge off the whale carcass, you start to get smaller organisms that colonise the bones of the whale and the surrounding sediment.
There are creatures called bone-eating worms or zombie worms and they'll last for months or years as they kind of start to break down the smaller pieces. And then there's a sulphophilic organism
phase so any bones or tissues that are remaining actually start to decompose and you've got bacteria that sort of breaks down the fats the lipids uh in the bones you know you get sulfur and methane these kind of gases that get released right and then that attracts more bacteria and that sort of forms these bacterial mats which that attract things like muscles and other little sort of invertebrates and this this lasts for decades that sort of stage the
Amazing. Basically, once all the kind of good nutrients have been extracted, you have what is, I guess, kind of like a rock, like a solid structure that's left, and other things like sea sponges, glass anemones, they might sort of take root on it, and that just kind of becomes their home.
I mean, it sounds like there would almost be nothing left after all of those successive waves of different types of creatures and bugs, but obviously there is, because there was something for scientists to find. And no doubt there were different parts of this whale graveyard showing different stages of that process, I guess. But where was it for starters? Where was it and how did they find it?
Yeah, so this is the Diamantina Zone. It's this area about 1,600 kilometres from Perth in the Indian Ocean, middle of the Indian Ocean. And it's just like a series of underwater ridges and trenches and it gets very deep. It gets down to just past about 7,000 metres around one of its deepest points. Wow. So it's quite far down.
So that's seven kilometres under the surface of the ocean.
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Chapter 3: What is a whale fall and how does it occur?
Thanks. That was environment reporter Peter de Kruijff from our very own Radio National Science Unit. We'll put a link to his story about this discovery, as well as the paper itself in Nature, on our website. This episode of Lab Notes was made on Gadigal and Ngunnawal and Ngambri country. It was produced by Amy Briggs, and I'm Jonathan Webb. I'll catch you next week.
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