We talk with professor alan jamieson and polar expert, shaylyn potter about Antarctic submarine dives, below-freezing trenches, the different types of icebergs and biodiversity in the antarctic.
Listen to the full interview on The Deep-Sea Podcast
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Shaylyn Potter
Polar marine scientist, Sub pilot and Expedition Leader
So I am joined from Antarctica by Professor Alan Jamieson and expedition leader Shaylyn Potter, onboard RV Dagon.
Alan: Hello! Shall I tell you a little story of why this conversation is taking place? So about two or three years ago I decided it would be a really good idea to come to Antarctica on the ship, because, obviously, we’ve got a big scientific program going on.We're doing fracture zones and trenches and abyssal plains and all the rest of it. So we had Antarctica on here.
So for the last two years, we’ve had it all planned out. We were going to go to the South Orkney Trench and we were going to do some great work in a nice cold sub-zero trench in Antarctica. And as per procedures and protocols, we went into quarantine in Chile for five or six days before joining the ship. And this is where I met Shaylyn Potter who is from an expedition company who's come down to help us make sure we don't break the laws in Antarctica. I'll introduce Shaylyn later. But on the first day, she came to me and said “You know that whole area is under ice right now?”.
So 2/3 years in the planning, and the Weddell sea has been breaking up and it's the worst sea ice for 15 years. So in the space of a couple of days, we re-wrote the entire expedition to come over to the South Shetland Trench, which is where we are now. I just did a couple of dives in the sub, and we've done about 24 landers… mapped a whole bunch of stuff and it's cold.
Nice!
Shaylyn: Yeah, I think the first day we met we were just having coffee kind of casually and chitchatting about what your plans might look like for the Expedition. And I said something like ‘Well, what are you going to do or what's your backup plan if the ice doesn't clear?’ And people said: ‘Well what do you mean? The ice is supposed to be clear. It's the summer!’ And I thought, ‘What do you mean, what do I mean?!’
Alan: Yeah.
Shaylyn: And then we got everybody involved looking at the ice charts and thought hmmmm, well we can't go there and so then a new plan involved.
Alan: Yeah but here we are. We're in Antarctica and we've been here for… I don't know two weeks now. We’ve got another week or so to go and then… actually I don't. I'm getting off, but Shaylyn’s got another month to go yet. And then you're coming down here Thom!
Yeah, so any advice on what to pack?
Alan: You need warm clothes. That's what you need. It's all about the clothes, it's all about the fashion.
Thom’s weird orange thing
I did get a weird orange thing, I'm rather proud of it. It's kind of a balaclava, kind of its own hood. It looks awful, so I'm really happy with it. It's bright orange too because orange is more than a colour, orange = safety.
Alan: Anyway, Shaylyn, you should introduce yourself because obviously, we haven't had you on the show before.
Shaylyn: So I'm Shaylyn! And I first started coming down to Antarctica in 2015. I was originally working as a scuba diver, but of course, with scuba, we're only allowed to go to 40 m recreationally. And in Antarctica, you have this really weird kind of phenomenon with the ice. You know the big icebergs all around, and it's scouring all of the shallow areas. So basically within your scuba depths, you're in this ice-scour zone and it's kind of boring to dive in. But I could be looking down the walls and see that there's a lot of life deeper than that. And so I got really invested and interested in what might be deeper than scuba depths. And I started getting into using ROVs on expedition ships and then eventually trained to be a manned submersible pilot. So for the past couple of years, I've been working as a sub-pilot on an expedition ship. And my primary place of interest and work is in Antarctica.
Alan: Nice. So you don't do the Arctic then? You're not a polar person? Just specifically Antarctica?
Shaylyn: Well, I do do the Arctic. But I don't find it as interesting as Antarctica. So I try to focus my time down here. I think there’s just more to see. I think it's more interesting.
Having experienced both in quite a lot of detail, what are the differences? Why do you love the south over the north?
Shaylyn: Antarctica is just so unique. If you think about where it is geographically, Antarctica separated from South America about 30 million years ago. So it's been isolated both geographically, and then later thermally, and then physically with the Antarctic circum-polar current for many many years. And because of that, it's allowed for species to evolve and display high endemism here in Antarctica. So you'll see species here that you won't see anywhere else in the world.
That's true! The North Pole feels more connected. There are more currents going around there. It feels easier to access.
Shaylyn: Yeah, it'll be easier for species to transfer to the Arctic from other regions. But to get to Antarctica would just be so challenging. So like, species dispersal: this doesn't really happen so much between the other oceans and the Southern Ocean.
And then Antarctica in particular, particularly with us in the deep sea end of things, it's a species generator. There were so many things that went there and really radiated. Because they're cold-adapted, they're for some reason also deep-adapted, and then they travel out along the trenches. So that's what I'm most interested in when going down there; is seeing maybe the seat of some of these lineages that we're so familiar with.
Alan: I don't want to crush your dreams and aspirations Thom, but I reckon you're wrong. We've been doing a lander survey from 1000m to 5200m and we've done 24 now (or something like that), so it's about 50 cameras worth of data. And after 2300m, it’s almost nothing but Coryphaenoides armatus. Literally, nothing! Tonight… about two hours ago was the first time we saw a single eelpout! We'd expected it to be this amazing, super diverse fish farm. Below… or at least sort of less than 2300m, there are icefish. Always solitary, and not very friendly. And then the big macrurids. And I swear, that's about it.
There are over 200 snailfish hiding there somewhere. Under some rocks?
Alan: I saw one in the sub yesterday. I saw one snaily that I didn't recognize in the sub. And that was at 2700m. Somewhere else deeper, we saw a snailfish… but right on the horizon on one of the landers. So, technically we've seen two. But two things are interesting. One is there's hardly any fish here, for some reason, I don't really know why. But the interesting thing is, the coryphaenoides numbers are absolutely astronomical. Through the roof at 4000m. And they're all ridiculously infested with parasites. They've got pox, they've got parasites, copepods. They've got leeches hanging off their underbellies. They've got that fungal infection that's prising their eyes out of their heads. They're the ugliest bunch of lepers I think I've ever seen in my life.
Wow!
Alan: Yeah. So there's a story in there, going on somewhere. But on the flip side, when we do a dive, we've done one to 5000m and one to 2500m, they are the most diverse and abundant deep-sea fauna I've ever seen. By a long way. It was just every single thing you can imagine there. Just not really fish.
Shaylyn: But for invertebrate lovers, then Antarctica is a really good place!
Alan: Yeah. Great jellyfish too, plus some squid… and I mean the 5200m site. Remember most of the time when we dive to 5000m, what you see is interesting but you don't see that much. And you see some really quirky little things. And during a dive, you probably take a few hundred photographs and it's good solid data. Here, I took nearly 2000 photographs just on the internal camera, and I still don't think we have even quantified all of it. It was just thousands of brittle stars, sea stars, urchins, anemones of every possible shape and size. It was absolutely incredible. Honestly, it was so cool, and you think it's at 5200m.
Shaylyn: What's been really interesting for me… because most of my work, all the studies that I do… because now I'm about to start my PhD studying continental shelf, sea-floor biodiversity. And so, I'm familiar with the literature of that region. And the submersibles I pilot, we can go to 300m, so it's just barely getting into that deep sea realm. But we're on that continental shelf of the peninsula and we do see a really high abundance and also quite a lot of diversity of pycnogonids. And as Thom mentioned, we think they originated in, and diversified from this region. And we also see quite a lot of octopus. And just the biomass and diversity at those depths is extremely high, particularly for invertebrate animals. So it's been really interesting for me to see deeper from the landers, that we're just not seeing either that biomass or diversity. And I've been really, really surprised: we saw one pycnogonid and zero octopus on the landers. So for me, that's been super fascinating to see that stark difference.
Alan: Yesterday we saw one sea spider at the end, which is the pycnogonids. And a little octopus, we got. I'll show the photograph for the podcast, but we came across a tiny little octopus, we called it Pearly because it was a little white pearly thing with big eyes. Quite a lot of squid. There was a lot of squid up to the 2000m range. And lots of really nice little red jellies, the ones that just hover past. We’ve got loads of cool footage of those. Those are really abundant. Yeah. So anyway, Shaylyn, you told me you did a dive in the Caldera at Deception Island.
Deception Island - Contains modified Copernicus Sentinel data 2023
Shaylyn: Deception Island is one of my favourite dive sites! Both scuba and in deeper submersible depths, in the peninsula. And I think it's just so unique compared to other regions. Like I can see a photo and I can recognise that it's at Deception Island. I don't really know why. It's just, I can recognise the assemblages of species. And there's not a lot of information or literature on it, about why it's so unique there. But I imagine the input of the hot water and maybe sulphur or whatever's coming out, that is kind of shaping that ecosystem. But it's quite different than any other dive. I dive quite a lot around the South Shetland islands, and it doesn't look anything like what it looks like around Deception.
Alan: I think for those listening, who may not know what Deception Island is, it's part of the Shetland Isles which is West of the peninsula. But there’s a Caldera. And it's basically 10k diameter or something, and there's a section which is broken off so it's filled with water. So you can sail a ship into it and there's an old British whaling base on the right-hand side, as you come in. There's a Spanish research station. There's an Argentinian one there. And I remember I went there about 9 years ago and just thought it was absolutely phenomenal. It was full of chinstrap penguins and all this kind of stuff. And it's just very very unique in terms of the visual imagery of it. There’s nothing quite like it. And when we were talking about this trip, I said to Captain Jim: if we do have to run from bad weather, what's our plan? He's like: Oh, there's all these bays and stuff up in King George Island or Livingston or whatever. And I'm like, all right. But if we get a chance, we should go to Deception, it's the coolest place. And right enough, a bit of bad weather came along and we were charging in there. It’s a brilliant natural port. There's nothing really quite like it. It's just cool, really cool.
Is there a difference in the slope elevation in this part of the world? Is it something about the sea ice that pushes it down or it's higher? Our usual deep-sea markers when we do them, are based on the shore. When we do slope depth and things like that, it's slightly different here and so our usual deep sea boundaries don't fit very well in Antarctica.
Alan: Yes. The 200m continental shelf is something that is unique to Western Europe. That's why the 200m mark was more or less decided that this is the start of the deep sea. But the continental shelf running right round the Antarctic is actually 500m on average, not 200m. And most places in the world don't have a continental shelf at all! So the 200m mark is a lot of nonsense, I think.
Alan: The unique thing about it, is what Shaylyn was touching on, it’s these big chunks of ice that decide to leave Antarctica for good. One of the first things they do is they gouge big scars across the continental shelf. They tear up the seafloor before they ultimately calve off and break off from each other and become icebergs to start floating off. Which is quite unique to here.
Image courtesy of Inkfish/UWA-Minderoo Deep-Sea Research Centre
Does that change the habitat types you see? Because most of the inverts you've mentioned are mobile short-lived things. I'm guessing lots of scouring means there isn't big coral reefs and things that take a lot longer to establish?
Shaylyn: Yeah, so the icebergs will definitely scour areas in the shallows. I mean, even down to 200 meters you can have iceberg scour. And so often, if you're looking for places where you're trying to find diversity, you need to find protected areas or more vertical walls that are going to be protected from ice scour. Yeah there are definitely places with more sea ice cover, as the sea ice is going to retreat or we're losing glacial coverage, you're exposing new areas of the sea floor and opening up new areas where things can colonise. But also as the ice is break breaking off, you're going to deal with more iceberg scour. So it definitely changes the types of species you can find. And the early colonisers are going to have to come into those areas first.
And you end up with things specialised to quite a high generation time because, I'm guessing, that if it scoured one place once, the chances are it's going to follow that same path the next piece that breaks off? Or do they tend to be quite random?
Shaylyn: I think it depends on the area. But one of the most interesting things for me working as a sub-pilot, is just seeing things that I guess I wouldn't expect to see on the sea floor. So there's this one area and it's close to the Lemaire Channel, so all the cruise ships go there. It's this beautiful scenery. But there's this place where the shelf comes up to this quiet little shallow shelf, and it's called Iceberg Alley because huge icebergs come in through the deep channel and basically just get stranded there. So we can go on little boats and look at the icebergs. We were going to do a sub-dive there, I thought I don't really want to get in the water because I know the bottom's just scoured because there are massive icebergs stuck on the bottom here, and they come through here all the time. But we went on a dive anyway, and I was really really surprised to see some giant sponges. Some of the volcano sponges and different glass sponges were all over the bottom. So I was really interested to see that. When we're looking at areas that are scoured with ice a lot, you expect to see mobile species like the brittle stars maybe some fish or early colonisers like the tunicates and things that can come in and grow rapidly. But you don't expect to see long-lived glass sponges. And so for me, that was interesting. And thinking: either these are just lucky sponges that have been here potentially for hundreds or thousands of years, and avoided ice scour, or they're growing faster than we think. So it was just really interesting.
Yeah, when something turns up that's wrong or against your expectations… it's usually a good sign. Embarrass ing, but usually a good sign.
Shaylyn: Yeah but I think we just know so little about this ecosystem. There's been a lot of data collected on parts of the continental shelf, especially around the peninsula or around stations. But a lot of the data we have is just presence or absence data. We don't know how it reacts over time, we don't know much about the biology of the animals and the large volcano sponges. Some studies show that they showed no growth within 10 years and we think they can live up to 10 to 15,000 years, so for a long time, scientists thought well these are really slow-growing long-lived species. But then when the large ice shelf collapsed, within just a few years we saw those sponges move in and grow really rapidly. Then we realized well given the right conditions and enough food resources, then they were able to colonize quickly and rapidly grow. So can't really make assumptions or infer a lot about this ecosystem from you know single studies. So it's been really challenging I think for science to make progress down here.
Yeah things are still true. but they might not be true everywhere. even with the same species.
Shaylyn: Exactly.
What else have you been up to?
Alan: I'll get Shaylyn to do this… ice is not just ice. There's lots of different ways in which it can be characterised, isn't that right?
Shaylyn: Yeah! But I think the splits are a little pedantic but… Okay, I might be wrong but it’s something like this: In order for it to be an iceberg officially it has to be taller than 5m.
Alan: That’s not very big!
Shaylyn: It's pretty big… But if it's 1 to 5m, then it's a bergy-bit. And if it's less than 1 meter, then it's a growler.
Wow! And this is above sea level isn't it? So they're considerably bigger below?
Shaylyn: Yes, yeah. So they're floating. So most of the icebergs (depending on their density) will be like 70% or so below.
Alan: There was a big piece of ice we came across, quite early on a couple of weeks ago. And it was 13 miles long, something like that. It was great!
Image courtesy of Inkfish/UWA-Minderoo Deep-Sea Research Centre
And do they stay ‘berg’ no matter how big they get? Or is there like an extra size class?
Shaylyn: I don't know if there's bigger, but the ones we saw (and you might see some as well) with the flat tops, those are tabular icebergs. So those came from an ice shelf and that's why they look like that.
Ah! Do we differentiate their origin whether it's glacial or sea ice?
Shaylyn: Yeah, so it's definitely glacial ice. But you can have a glacier like a glacial face, or a tidewater glacier that will calve off icebergs. And they're quite large, but they're not tabular bergs. I'm not a geologist… you would have to ask somebody else. Devon on board has been able to talk to people about it. I'm just a naturalist and an ice enthusiast.
I'm not sure we should let the rock people have water when it gets hard. I still think it's in our jurisdiction. Just because it's hard like a rock, you can't claim it.
Shaylyn: All right! But it's quite unique to Antarctica, so we have the ice sheet in Antarctica right? So it's snow falling on the ice field, and it's flowing downstream to all these glacial outlets. If it's coming down to the water, touching the sea water and calving into it, that's a tidewater glacier. But in some areas where it's not so steep, the glacier itself instead of crumbling off, can just keep floating out over the sea. And so it's not actually on the seafloor, it's floating. And that's the ice shelf. And a lot of them have been around for many many years thousands of years. And that's one of the concerning things that they're talking about with Antarctica and climate change, is the ice shelf collapse because these ice shelves are acting as buttresses for the ice sheet behind it. Because over time, or for a long time they've been relatively stable. So some of it'll break off and these are the massive icebergs you see on the news that are getting stuck and disrupting things. They give them names they're so big! So right now, I think the popular one is A23A and you can monitor it with satellites and see where it is. And these things are like as big as US states, they're absolutely massive and so when you're looking at it from a ship it just looks like a wall of ice, you can't see around it. So those are from the ice shelf and it's concerning that those are breaking up and we've already lost part of the Larson ice shelf and yeah we're concerned about losing more.
Having so much experience down there, what feels different? What firsthand things have you noticed changing?
Shaylyn: People ask that a lot. I'm not sure I really noticed anything. I mean we noticed some small changes but it's hard to really quantify it. This is a really big ice year. We're seeing the ice change. So in some areas of the continent, we're seeing more sea ice and in some areas, less. One thing we notice just year by year, depending on the sea-ice year, (whether it was a good ice year or a bad ice year) you see the dynamics between krill and salps change. And that's a bit of concern because when you're losing sea ice, the krill need to feed under that sea ice. So when it's a bad ice year, salps tend to out-compete the krill. And that's bad for the entire ecosystem, because all of the marine mammals depend on the krill for food.
This debris-covered iceberg was calved from the terminus of a glacier. Image courtesy of Bruce Molnia US Geological Survey - American Geological Institute.
Alan: The interesting thing about all this stuff is the relationship between glaciers and the deep sea. This is, after all, a deep-sea podcast. But the way in which that works is when the glaciers travel down the mountainside, they pick up stones and rocks and boulders and then they slowly grind them into these big black angular blocks. They look almost like tombstone type of things, you know? And then, when it breaks off and ultimately flows out to sea and the iceberg melts, by the time the iceberg is seriously melting you're probably pretty far offshore. And then these rocks just fall out of it. So it's called ice-rafted debris or IRDs. Some people call them drop stones. But we're seeing them on sub dives, we're seeing them everywhere. And each and every one of them is completely populated by deep-sea animals. Because you're delivering a hard substrate.
And some of them are like big old boulders, like enormous big boulders and you can tell they're IRDs because they're really black, smooth, just angular things. Because they have just been eroded and grinded away down the mountainside, all this time. And then suddenly, they're floating out to sea in a ice cube and then plop! Then they fall to 5,000m. So there are those physical connections between what's going on in the continent, and what's happening at 5,000 m nearby is pretty striking.
Shaylyn: In general, when we're talking about the Antarctic benthos, we describe that the diversity and the biomass vary highly on small spatial scales. And a lot of that reason is because of the dropstones. So in one area, a lot of these bays were glaciated in the past and have retreated. So we can do a sub dive in one bay and it's just kind of flat and sandy - you know soft sediments. And then you could move further out of the bay and find a patch of drop stones and maybe it's only 100 m away, but the biomass and the diversity varies significantly on that small scale. And that's because of the dropstones and that hard substrate that allows for the diversity of those animals to live on. So it absolutely is connected. This glaciated region definitely is connected to everything that's happening in the deep sea.
Alan: Yeah, and the other unique thing about Antarctica is obviously the temperature is very very low. So these trenches are the only places in the world which are super deep sea and Subzero (at a certain depth they become subzero). And the significance of that is…you know we've probably spoke about this a few times on the podcast under various different contexts, but you know high pressure/low temperature have the same perturbing effect on the cell. So if you want to go deep you need to be warm. So places like Red Sea and stuff like that, if you're deep and cold you tend to become shallower. And so, the idea is: there are lots of deep-sea species in Antarctica that were actually much shallower than you find them in other places. Because that sub-zero condition is another perturbing effect, in addition to the high pressure. Some guys worked out in the 80s I think, it is something thing along the lines of: a shift in 2° C is the same as a shift of 1000 m.
So if you look at somewhere like the Mariana Trench, it’s ~2° C. At the same depth, there's over a 2° decrease in temperature here, so you'd expect a lot of deep sea stuff to be shallower. And to be honest, I think it's not as obvious from what we've seen so far, but there are signs of it. So the enormous aggregation of rat tails for example, are happening shallower than we'd normally see them. Out in the Porcupine Abyssal Plain in the North Atlantic, it's normally about 4800m you see a lot of a lot of these things. But here, between 3800m and 4,000m is the real sweet spot for tons of these things. But over the next few weeks, hopefully. we'll work shallower and see how far up some of these quintessentially deep-sea species are going here. It's almost certainly to do with temperature.
It's sometimes called ‘deep sea emergence’. And the cold water corals or the deep water corals that we're talking about in the last episode, the depth variation with these same species was huge. So I was looking at them say around Ireland at 300m but in the Fjords off Norway where it's much colder, you can scuba dive with them! They're at 40m. And we get similar in the Fjords here, we get deep stuff coming up a lot shallower.
Shaylyn: It's the same in Alaska, when I work up there. You can see species that normally we just see in the deep sea off the shelf. And we see them in the Fjords in Alaska, the red tree coral for example. Do you think that's why we're not seeing so many pycnogonids here Alan?
Alan: Uhhh I don't know. I was under the impression they were quite abundant around here, you know? Because last time I was here, we had a time-lapse stills camera and we put it at 2000m and there were two or three of them wandering around. I was taking a picture I believe every minute for about 10 hours, and we saw two or three just walking past the camera. So from that, I thought well there's obviously quite a lot of sea spiders going on. But then we deployed that first set of landers and one of them was a similar depth, and a sea spider did come along, it walked around the arm a little bit, you can see on the latest YouTube video we put out. Just a little plug there. But I haven't seen one since. I caught sight of one in the sub, I don't think we recorded it. But just at the end of the dive, I was looking out and I was like there's a sea spider! I couldn't quite get the image of it, but I was under the impression there was loads and I'm disappointed. I thought this place would be swarming with giant sea spiders and I was going to fight them all.
Shaylyn: I'm disappointed as well, and quite surprised because we do not see them on the peninsula, in scuba depths. I know they are shallower in south Georgia and also in the Ross Sea around McMurdo. But on the peninsula, I've never ever even once in 10 years seen one scuba diving. But in the subs, you know 200-300 meters, we see them regularly. Every day we see multiple different species of pycnogonid, and so I was under the impression that maybe they're just deeper than any scuba depths. So at 200-300m there are sea spiders,I really assumed we'd see more with the landers and your sub-dives. I've just been really surprised by that.
Alan: Yeah maybe we need to go shallower. I mean, at the moment our shallowest one is just over 1,000 m. We do have a potential 800m site on the list of things to do before we go. But everyone's a bit reluctant to go to three digits because it's just not our jam. But I think we're going to have to do it, cuz we've been all over the deep basin and we're just going to have to crawl back up. But it would be worth it if we got some good sea spider stuff. ‘Cuz they're such a cool animal.
Shaylyn: Yeah that's why I think it's valuable information to have, because we don't actually know their depth range. I know it's not shallow and I know yes it can be around 200 meters but where does that line stop? When do they stop being so abundant? You know?
Alan: That last one we saw was the only one we recorded so far, I'm pretty sure that was 1800m or 2,000m. But that's a good chunk away. but yeah we should make that priority for the next week I want to get eyes on I want to intense eye contact with a picnic on it
Alan: Enough fish. I'm done with fish. So done with rattails. I’ll happily never see another rattail for as long as I live.
Ok, thanks so much! It was really lovely to meet you, Shaylyn. Thank you for coming on.
Shaylyn: Yes it was nice to chat! Thanks for having me.
Alan: Right cheers bye.