Instant Genius - Deep sea habitats - Everything you ever wanted to know about... the deep sea with Dr Jon Copley

Episode Date: November 11, 2020

Our guest this week is Dr Jon Copley. Jon is a marine biologist, specialising in the deep sea. He went on the first mini sub dive to the world’s deepest hydrothermal vents, 5km down on the ocean floor, and also took part in the firs minisub dives to 1km deep in the Antarctic. Jon is also a science communicator and writer, who worked as a science advisor on the iconic BBC series Blue Planet II. He is also an associate professor of ocean exploration and public engagement at the University of Southampton. In 2019, he also published fantastic book called Ask an Ocean Explorer which tells you all about the ocean in 25 questions. Over three quick-fire episodes, Jon tells BBC Science Focus managing editor Alice Limpscombe-Southwell about the bizarre life found on the ocean floor, the habitats where they thrive, and what it's like to explore the deep sea in a submarine. Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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with the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at sciencefocus.com or look out for us in your app store. Welcome back to the everything you wanted to know about podcast from the team behind Science Focus magazine. Today, we're back talking about some of the most popular questions about the deep sea with marine biologists,

Dr John Copley. In this episode, we're taking a dive into some of the incredible habitats that exist in the deep sea, including the intriguing world beneath Antarctica, the awe-inspiring trenches and mountains that ripple the ocean floor, and the hydrothermal vents that support whole ecosystems, and we also look at the scavengers that quickly colonise a whale carcass. So, so we talk about the deep sea. So is there a particular depth that's actually considered to be the deep sea, or is it below a certain point or does it vary depending on where you are on the globe?

We generally define the deep sea as beyond 200 metres deep. And there are a couple of reasons for that. Around the land, we have the shallow, what we call continental shelves, which stick out for a little way, you know, maybe a couple hundred kilometres from land. And then the seabed slopes away down into greater depths. And that depth at which what we call the shelf break, where it starts to get deeper and we get into the ocean basins, the start of that is at about 200 meters deep generally. So, you know, that's one reason. The other reason is in clear open ocean water, 200 meters deep, is about the limit where sunlight is still bright enough for algae to thrive through photosynthesis. So it's the top of that upper brightly sunlit layer where the photosynthesis is happening. So 200 meters is

rule of thumb, you know, defines everything beyond that we think of as deep sea environments. But of course, you can have deep sea-like conditions. It does vary around Antarctica, because of all the weight of the ice on the continent itself, pushes the continent down. The continental shelf around Antarctica is much deeper. It's sort of 500 meters deep instead of 200. So you've got deep sea, essentially right up to very close into the coast there. And in fact, where in the past, the ice sheet has been more extensive and glaciers have scoured out deep valleys. You've actually got deep valleys down to more than a thousand meters deep, almost a stones throw from the land today. So it's a very exciting place to get into the deep ocean there.

If you can get down there to work. Similarly, in terms of the light and the photosynthesis, it depends how clear the water is. You know, again, the places where I've done, where at 80 metres deep, we're into the midnight zone. You know, it's pretty much picked black because there's a lot of, it might be sediment from nearby rivers or, you know, it could actually be blooming algae, filtering out the light and it gets dark much sooner. So it does actually vary. But as a rule of thumb, we tend to say, right, 200 metres, that's where the deep sea starts. Did you talk about Antarctica there briefly? So what sort of animals are you seeing, like,

in the deep sea around Antarctica? Because you sort of hit, I mean, Antarctica is not the that accessible for us anyway. And then you think, oh, God, the deep sea around Antarctica. That's like really inaccessible for us. The deep sea around Antarctica is, in a way, an amazing contrast to what's on the land. Because apart from the colonies of animals that make a living from the sea, which are very rich, like the penguin rookeries and so on, yeah, of course, life on land in the Antarctic is pretty challenging. You know, there are some lichens and there are some small things that crawl around in lichens in Antarctic valleys and what have you. now the ocean around Antarctica though is is lush with life because for six months of the year when

you've got lots of sunlight you know around around the clock then the algae can really go for it and bloom and then of course that's lots of food for other things which is how you're able to support penguin colonies and things like that down there but it also means that you know the deep sea around Antarctica is very rich because you've got a lot of food being produced in summer by algae at the surface. And that is ultimately, a lot of it is sinking to the ocean floor and it's food for things that are down there. So yes, I've been lucky to dive down there in submersibles. And yeah, the ocean floor at a thousand meters deep is is as rich as any I've seen at a thousand meters deep elsewhere in the world. So there are lots of, there are lots

of invertebrates. There aren't so many fish that can cope with the cold conditions because it's, you know, At 1,000 metres deep around the Antarctic Peninsula, it's minus 1.5 degrees C. And that can be a real problem. So there are fish that can cope with that. They have anti-freeze proteins in their blood and so on. But there are fewer fish species that really thrive down there. But that means you get a lot of invertebrates, of course. A lot of invertebrates dominating his top predators down there.

So there's really lush invertebrate life all over the ocean floor there. And it's fed largely by krill poo. because you've got these algae blooming at the surface, you've got swarms of krill feeding on all that bounty, and krill do a really interesting thing when they've had a big meal. They kind of have a nap afterwards, a bit like us. So what they do when they've gorged themselves

is they go into a kind of state of torpor. They have a nap and they sink. They sink to the bottom of their swarm. And then when they've done a bit of diet, and they wake up again, and it's time to go and feed again. That is when they evacuate their gut. So they have a nap, they sink to the bottom of the cruel swarm, when they kind of wake up, that's when they poop. And that means that they are pooing quite deep. So they're generating their poo, you know, not where they were feeding, but actually quite a bit deeper. So that has taken

that organic matter down a bit further into the deep without a chance for many other things to feed on it. And then it sinks as poo and things do feed on it on the way, but a lot more reaches the seabed below as a result of this little quirk that krill happens. One of the reasons they're so important for the food chain, not just food for penguins and other animals, but they're actually so important in getting food into the deep ocean. And I've noticed diving in minisubs down there, we are actually diving through krill poo. There are these little, like, they look like little bits of little squirts of silly string. And I was thinking, what is this stuff that I'm seeing floating around us or we're diving through it?

and it's like these little squirts of string-like stuff. And what puzzled me briefly was it's longer than krill, but the nozzle is very small. So actually you did actually watch krill pooing, squirting out these strings like krill poo, and that then sinks into the deep ocean. But it's food. It takes food down there.

So, yeah, it's incredibly rich living carpet on the ocean floor there. Very exciting to explore. And on that point, I suppose, people think of the sea floor as just being this sort of vast, flat space, but it's just not like that at all. So can you tell me something about the variety of these deep sea habitats? It's not just this flat, empty space. That's probably the most important thing for us to realise about the deep sea is it's not one environment. We perhaps zump it all together as that, because it's dark, it's alien to us, and so on. And for a long time, I think people did think, oh yeah, it's just this flat plane of gray mud.

In fact, Rajad Kipling described it as that in one of his poems. He wrote a poem about Deep Sea Cables back in 1893, and he talks about the vast gray-level planes of ooze. And some of the deep sea is like that. What we call the abyssal planes are fine, you know, grayish mud. But it is not all like that at all. it is just as rich and varied a terrain as the world above the waves. So, yes, there are mountains dotted around the deep ocean, the deep ocean basins. Many of them form as underwater volcanoes.

There are other ways you can make undersea mountains as well, but mostly formed as underwater volcanoes. And, you know, when eventually one of these undersea mountains grows as a volcano big enough to break the surface, we get islands. So, I mean, that's what the Hawaiian island chain is. And around Hawaii, as well as the islands poking out of the sea, there are a lot more undersea mountains as part of that chain that didn't make it to the surface. So, yeah, we've got mountains that are as spectacular as any that we find on land. We have got other amazing features. We've got this undersea volcanic rift running all around the oceans, down the middle of the oceans, a bit like the seam on a tennis ball, the mid-ocean ridge, where the plates of the ocean crusts are being pulled apart and rifting apart as they're. ride on convection cells in the mantle. And so, yeah, that's a rocky, rugged environment. And it's

got a central rift valley running along it with really steep sides. You know, if we were trying to cross this on foot, we would really struggle. You know, we would need ropes and pinions and it'd be very rocky, fresh, glassy, sharp lavas that we'd be trying to climb down and walk across. It would be quite a hike to cross that terrain if it were on land and we were trying to do it on foot. We've got ocean trenches as well. So this is where one of the plates of the ocean crust is hitting another plate with a continent on it and being pushed bending back down into the interior of the earth. And that then means we get a trench where that's happening. The trenches aren't a sort of, you know, sheer cliff sided as we often perhaps imagine. But we often perhaps imagine, but we're

and sometimes see in the Hollywood movies and so on, often the slope into them is much more gradual. They're really big features. You know, if you were standing on the edge of, say, the Puerto Rico trench and trying to look across it if we took all the water away, the other side of it would be beyond the horizon. You know, it's actually wider than you'd be able to see. And the average slope down into it, for most of it, it's probably, you know, around about 10% gradient or whatever. There are places where it is sheer, but, you know, it varies. Yeah, there's bits of rugged, amongst all of those then. We've got bits of rugged rocky terrain, as well as these planes of soft ooze. And then within any of those, lots of different habitats for life. So we've got these hot spots where there are chemical energy sources for food chains. We've got the hot springs mainly dotted along that mid-ocean ridge in that rift valley and so on. We've got other places, though, where you can get the same kinds of

chemicals coming out of the seabed supporting colonies of deep sea animals through through bacteria. So we get what we call cold seeps and they come in lots of different forms, dotted along the continental slopes, the edges of the continents and so on. We also get, you know, when something like a whale dies and sinks into the deep ocean, yeah, we see on the TV documentaries, here come the scavengers, the six gill sharks, ripping off chunks of flesh and the, you know, the hagfish and all these sorts of animals. yeah, but when the flesh is gone and we've got the skeleton, then we get a whole suite of species

colonizing that and still making use of what organic matter is left behind in different ways and in turn supporting other forms of life themselves. So we get a whole other kind of food chain and that can last for decades of what was a dead whale that sank to the ocean floor and long after the scavengers have been and gone. So we get all these fantastic varied habitats in the deep ocean. Yeah, because I think obviously on land, if something dies, it'll break down quite soon. But obviously in the deep ocean, like if a large whale or a large animal falls to the bottom, it takes a lot longer, doesn't it?

Because obviously, there's less oxygen down there, maybe. It's colder. It depends where you are. And what really matters when it comes to how quickly things break down and get used up in the deep ocean is size, ultimately, and the nature of what things are made of. So readily available food like flesh on a dead body, oh my goodness, the scavengers move in very quickly in the deep ocean because they're always hungry for that next meal, you know, because they don't know when it's coming, they don't know where it's going to be. So they're able to detect it. They move in incredibly quickly.

You know, we can put down experiments doing this. We can put things down on the deep ocean with cameras or bring them up very quickly and see what's colonized them. And within a matter of hours, scavengers have turned up. and not just the fish, but also wonderful things like giant isopods in some parts of the deep ocean. Now, these are relatives of the woodlice that we get in our back gardens, but, you know, we're talking up to 30 centimetres long. Now, they're incredible deep sea scavengers, and they arrive very quickly at carcasses, and they have sort of mandibles that will strip off the flesh very efficiently. But then what's left is there's still organic matter and potentially food, but it's still organic matter and potentially food,

harder to make a living from it. So take something like a whale bone, that whale bone has got fats inside it in its core, in the case of whales. Now, those fats are a food source, but how do you get at it? Okay, you've actually, you know, it's locked away in the bone there. Well, bacteria get in through the bits of the bone and they colonize that, that core of, fat-rich core of the whalebone. And they break down the fats, and that's how they make a living. And in doing that, they produce certain chemical compounds, hydrogen sulfide, which then seeps out of the whale bone. That hydrogen sulfide is an energy source for other bacteria, which then make a living from that. And then animals can live in partnership with those bacteria.

So we get things like muscles living on the outsides of whale bones. The muscles are fed by bacteria in their gills or on their gills. Those bacteria are fueled by the hydrogen sulfide seeping out of that whale bone. That hydrogen sulfide has come from bacteria breaking down the fats inside the whale bones. Now, that process is a little bit more complicated, and it takes time to kind of set up. But it's about making use of everything until all of that organic matter has been exploited by life as a potential food source. We see it with bones, and the bone itself, you know, actually the solid bit of the bone, and it doesn't matter if it's a whale bone. This could be

a fish bone. It could be a human bone. There's organic matter inside that makes it. of the bone if you can get at it. So another of my favorite deep sea animals are the bone eating zombie worms. And these are worms. There are more than 25 species we know of now, but the first species of this type of worm wasn't described until 2003. So we haven't known about them for that long. At least 25 species out there. And they digest bone. And they actually secrete acid to dissolve away the inorganic bit of the bone so that they can make a living from the organic bit that's kind of locked up in it in its matrix. So they're able to exploit a resource that's very hard for anyone else to make a living from. And the same is true of wood. We get a lot of wood naturally ending up in the deep seas.

So not just wooden shipwrecks, but forested coastlines where naturally we're getting trees, eventually falling over, washed into rivers, washed out to sea. There's quite a lot of wood naturally exported into the oceans and it sinks into the deep ocean. And that kind of, that cellulose, that lignin, those forms of organic matter quite hard to make a living from. You know, we don't chew on wood as a food source. We can't digest it. So again, there are types of animals in the deep ocean that specialize in making a living out of the wood that gets washed into the deep ocean. They are able to digest it. And again, they colonize it really rapidly. So could there be any deep sea habitats we still haven't found? You've spoken about all those there are just fascinating,

but are there any found or are we pretty sure we know all the habitats? There could well be surprises in terms of habitats out there because now we talk about things like what we call a whale fall or a woodfall as a habitat as a special kind of food chain and some animals that specialize in that particular resource that forms that habitat. And these are really really, really small-scale things. So, you know, undoubtedly there will be different types of habitat, different types of ways of making a living from things in the deep ocean that form a little island like habitat. Yeah, I'm sure there will be some out there. There are, in terms of the chemically powered food chains that we get in some habitats in the deep sea, so the hydrothermal vents,

the hot springs we've known about for quite a while now. And then there are these things called cold seeps, which is a very broad term for just any other geological process. that pushes the right kind of chemical compounds out of the seabed for microbes to make a living from and then support animal colonies. And we're finding lots of different types of cold seep. There are mud volcano canos. There are things called asphalt seeps. It depends on the underlying geology. There are the brine pool cold seeps. And again, I think we're going to find different, you know, new forms of cold seep and so on that we hadn't imagined before from the geological processes that are out there. So yeah, there are undoubtedly going to be plenty of surprises for us.

Is it true because we often hear that we know more about the surface of Mars or the moon than the ocean floor? So do you think that's still the case? We have to be very, very careful with the words we use when we make those comparisons that we know more about Mars or the moon. We have more detailed maps of the surfaces of Mars and the moon and indeed Venus than we do of the ocean. floor because those planetary bodies are not covered with seawater. And seawater blocks radar signals, which is a problem. So, you know, if we want to get a really nice map of the bumps and dips of the surface of the moon, we can put a spacecraft in orbit around it with a radar system that will map it in great detail and show us features, you know, that are just a couple of meters across.

But we can't do that for the ocean floor, because we got plenty of satellites in orbit. with these kinds of radar instruments that map the land in great detail, that those signals don't go through seawater. So we can't do it in the same way. Now, so you might then say, well, we know more about the surfaces of whatever. We have more detailed maps as far as it goes. But, you know, in terms of understanding what's going on down there, the processes that shape the ocean floor, what lives down there, you know,

the biology, the chemistry, the geology, we know far, far. are more about the deep ocean than those other places in the solar system. So the total amount of rock that has ever been analyzed from the moon to understand its planetary geology is less than 500 kilograms. And Mars, it's much less than that. The only samples of Mars that we've had been able to analyze are rare Martian meteorites, bits of Mars that have broken off and tumbled to Earth and been recognized as having come from Mars, or what's actually been analyzed on Mars itself by rovers. Okay, so tiny volumes of rock, if you like, have been analysed to understand the geology of Mars in the same way. Whereas, you know, thousands upon thousands times more samples from the deep ocean to understand its geological processes, to understand its biology, its geochemistry.

We know far more about the deep ocean. We just don't have as detailed maps of the terrain yet. So just touch you again on hydrothermal vents, which you briefly mentioned a minute ago. we didn't really discover them until the latter half of the 20th century. So what makes these hydrothermal vents so special? Hydro thermal vents are what I've spent most of my career investigating in the Deep Ocean. And I found out about them while I was an undergraduate student, kind of by accident. They weren't actually in my zoology degree course because they were such a new discovery at the time. And it was only seeing a weird picture on the front of a book, the library one day, which was actually of these strange red plumed worm-like animal. I thought, hang on, I'm doing a degree in sociology, and I can't even tell what kind of animal that is. So I've fetched down this book. And it was actually a collection of very recent research papers about life

at hydrothermal vents. And I started reading it. And I thought, wow, this is amazing. You know, I want to find out more about this. And what captivated me was the fact that they they broke the rules that I was taught at school. You know, this idea that. life has to begin with sunlight as a source of energy. And here we have some microbes at deep sea vents that are able to use other energy sources to thrive. And in some cases, the microbes can do this without oxygen as well. You know, that's what opens our minds to the possibility of life elsewhere in the solar system, wherever we've got liquid water and volcanic energy source or some sort of volcanic activity like we get driving these hydrothermal vents on Earth.

So that captivated me and became my mission, if you like, to try to find more about them and explore them. And it was a great time to do that because it was a field that was only just starting to take off. So they life around, and what are they? They're hot springs on the ocean floor. So the best analogy are the geysers of Yellowstone and Iceland. In fact, Iceland is a really good analogy for hydrothermal vents, because Iceland is actually a place where the mid-ocean ridge, where we find a lot of the hydrothermal vents,

where it actually pokes out of the ocean to Fortman Island. So in Iceland, if you ever get the chance to go there, there is a rift valley running across it, which is just like the rift valley of the mid-ocean ridge. And you'll see, if you stand and you look down the rift valley of Iceland, you can see plumes of steam dotted along it from clusters of hot springs. and there'll be plumes of steam from one cluster, and then it'll be several kilometres,

as you look down the valley, to where you can see the next plumes of steam from the next cluster. That's just, that's basically what's carrying on beneath the waves. Beneath the waves, it's not steam, it's mineral-rich hot fluid, but it still shoots up, rises up like a steam plume, and then spreads out into the ocean. So that's what they're like. And first encountered in the late 1970,

Now, geophysicists had sort of theorized that these things should exist on the ocean floor, and people had been hunting for them for quite a while. And eventually, February 1977, there was a dive by the famous deep diving mini submarine called Alvin, with two scientists and a pilot inside, which had homed in on where there were signals that there was a hot spring on the ocean floor. And they came across it, and what surprised them wasn't the hot spring, itself, because that was kind of predicted by geophysics, but it was this incredible colony of animals thriving around it. Now, none of the scientists involved in that dive on that whole expedition were biologists, because it was kind of a geophysics investigation to find these things.

And they said, hang on, isn't the deep sea supposed to be, you know, pretty sparse in terms of its life? Because food, you know, food raining down from above is your food source. The deeper you go, the less food there is available, because it gets eaten on the way. And yet here, there was so much life. How could this possibly be the case? And then the biologist got involved, investigated it, found this process, you know, that it was this process of chemosynthesis, this other kind of food chain starting with chemical energy and microbes that's supporting all these animals living around the hot springs, the deep sea vents. So, you know, and then it really took off because then that opens up so many questions. How do they thrive like that? What interests me about

deep sea vents is they are island-like colonies of deep sea animals. So they are dotted along that mid-ocean ridge. You get a set of hot springs, life around it of these particular species, and then it's some distance to the next island-like colony. So just as naturalists way back in the 19th century explored islands above the waves, looking at what lives where and figuring out those patterns to understand about evolution and dispersal and so on, we can use deep-sea. vents as the same kind of model system. They're an island-like network on the ocean floor, through which we can understand how species disperse and evolve in the deep ocean. So that's what excites me about them. And it's really exciting, isn't it?

Because around those hydrothermal vents, it's really quite warm, isn't it? Obviously, the deep ocean is maybe at like one or two degrees. But then around there, it's like hugely warm, isn't it warm enough to survive? Hydro thermal vents, when it comes to temperature, are a place of extreme gradients. So we do see incredibly high temperatures where the hot fluid, the hot mineral-rich fluid, is actually jetting out of the ocean floor. So when it does this, it's carrying lots of dissolved minerals.

Once it plows into cold, well-oxygenated seawater, they precipitate out and form particles. That gives that hot fluid its smoky appearance with these mineral particles. It also builds up these mineral spires. where it's gushing out of the seabed. We build these what we call chimneys. Now, when we go to these and we measure the temperature of the fluid coming out of them before it mixes with the cold, deep ocean water. So we take a temperature probe, we take our under deep diving vehicle with its

manipulator arm, and we put that temperature probe right in the throat of that vent chimney, where the fluid is still actually clear. There's no smoky particles yet. It hasn't mixed. We get it in that what we call primary fluid. And yeah, we can measure. temperatures. I mean, the hottest temperature I've ever measured on an expedition was 401 degrees C. Now, it doesn't boil into steam. That was at 5,000 meters deep in the Cayman Trough, Cayman Trench of the Caribbean. That hot fluid doesn't turn into steam because of the pressure of the water, not that depth, okay. So it's incredibly hot there, but if you move that temperature probe, just a couple of centimeters away from the center of that flow where before that hot fluid, is mixed with anything, the temperature will drop by 120 degrees.

Okay. And if you put the temperature probe on the outside of the chimney, okay, just on the outside, outside of that flow, you're already down to 50, 60 degrees. If you look at where the animals are living, well, most of them are not living in water that's hotter than 25 degrees C. There are one or two that live right on the edge of these vent chimneys near the hot flow that can probably survive, routinely survive 50 degrees C plus 55 degrees C, which is amazing for an animal, you know, because normally the collagen that kind of holds bodies together starts to melt

at about 45 degrees C. So they've got adaptations to some, but there's only actually very few species that are living at really challenging high temperatures for the animals. Most of the animals living 25 degrees C or indeed, you know, cooler. Now, if it's 2 degrees, C is your background normal deep sea temperature, but you've found you're close to a deep C where it's 5 degrees C, well, that's just, that's just like a nice warm bath. That's not a challenge. That's actually, you know, that's actually a boon. You know, your metabolism could run a bit faster.

So, in fact, we do know that these environments can be nurseries, hatcheries for some deep sea species. There are deep sea skates that lay their egg cases near hydrothermal vents where the water's a bit warmer and they probably develop faster because of that. So it's an interesting gradient from extremes. Now, there are one or two microbes that can survive the really amazing high temperatures. The record currently for thermotolerance is 122 degrees C by a microbe from deep sea vents. Now, that's phenomenal. For DNA to survive intact at those temperatures and so on, that, that's incredible. But it's actually not a challenging environment in terms of temperature for the animals.

25 degrees sea and cooler. Well, that's not hotter than shallow tropical waters when marine life thrives. So just the final question. Why is it so important for us to study deep sea habitats? There are, I think, two fundamental reasons for us studying deep sea habitats. The first is one of pure exploration and discovery. understanding how life thrives down there, opens our minds the possibilities of how our world works, how the universe works, what else is possible elsewhere in the cosmos, and those kind of really big fundamental questions. So yes, by exploring environments that are different from the ones we're familiar with, we can gain those new insights into how things work, how nature works. these days though and when I started my career 25 years ago that was very much the motivation it was it was kind of what we call blue skies fundamental research these you know these big curiosity driven questions that has changed over the past 25 years now a big driver for the work that we do is unfortunately understanding the human impacts that we are already having on these deep sea habitats you know we think of them as being alien and

remote, but you know, the deepest place in the oceans is just short of 11 kilometers deep. That really isn't that far. You could walk that distance horizontally on land in a couple of hours. And, you know, if I were walking 11 kilometers from a major motorway on land and the wind's blowing in the right direction, I could probably hear it. So no surprise that we get noise pollution down there. I'd probably find things like Chris Packett's that had blown away from it as well. So again, you know, our rubbish ends up down there. We're having an impact on it. It is not as remote as we might think.

We think of it as this alien world. But yeah, unfortunately, it is very much connected to us. So again, for us to make informed choices about, you know, how we live, and I don't just mean us as individuals. I mean us as societies making these choices in the way that we go about things. You know, we have to understand the full implications of what we are doing. So that's very much a driver now is understanding human impacts as well as the curiosity-driven exploration. That's it for today.

In the next episode, John and I are going to be talking about exploration of the deep ocean, and he will give me a first-person account of how it feels to descend in a submersible to the bottom of the sea. He also reveals some of the surprising things that he has seen and tells us about some of the biggest threats that the deep ocean now faces. So if you've enjoyed this episode, and we'll be tuning into the next one, then please do subscribe, and if you can spare a minute, leave a review and let us know what subjects you want us to tackle next. And if you want more primers on the big ideas in science from the BBC Science Focus team, then head over to our website, ScienceFocus.com or find us on Twitter, Facebook and Instagram.

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