We explore the depths of the world’s deepest lake with professor marianne moore.
Listen to the full interview on The Deep-Sea Podcast
Professor
Marianne Moore
Professor emerita of biological sciences at Wellesley College
Biodiversity of Lake Baikal
I'm joined by Professor Marianne Moore whose research focuses on the biodiversity and environmental changes in Lake Baikal, Russia, where she has worked for more than 15 years. Specifically, Marianne is an expert on the ecology of the freshwater zooplankton and of human impacts on the lake.
Thanks so much for coming to have a chat with us. I'm super excited about this one!
Oh, I am too! Lake Baikal is my favourite lake, and it's a treat to be able to talk about it and share my excitement with others.
I'll let you start off with putting the lake into context. Why has Lake Baikal captured both of our imaginations?
Okay. Well, let me begin by talking about where it's located. So it's located in southeastern Siberia. So it's 200 miles north of Mongolia. And it's not way up within the Arctic Circle. It's considered a subarctic lake in Southern Siberia. Now, before I explain some of its unique features, for example, its depth, its volume… I'd like your listeners to imagine a lake shaped like a gigantic crescent moon. It's very long, narrow and towered by mountains, and it fills a gargantuan crack in the earth's crust. The deepest point in that crack is over 1,600 metres deep. So the lake is more than a mile deep. And it's getting deeper and wider each year by about 6 mm per year in depth and wider by about 2 mm because the lake is located where 2 tectonic plates are pulling apart. And because of its great depth, this is the largest lake by volume, you know, to fill it requires emptying all of the North American Great Lakes combined, which adds up to 20% of the earth's liquid freshwater. Now this is, by some estimates, the most biotically rich lake in the world. Tremendous speciation has occurred here, and it is sometimes referred to as the ‘Cold Galapagos’. So those are some of the features that make this lake very attractive to aquatic scientists.
The more I learn about it, the more it just grabs me. How did you discover it - How did it grab you? It's obviously really gotten its claws into you.
Well, all fresh water scientists know about this lake. Because it's so unusual, you know? Being the deepest, the largest by volume; the most biotically rich by some estimates. And it's a very ancient lake; one of the 2 oldest lakes in the world. So again, it's like the Holy Grail or El Dorado for freshwater scientists. You know, every freshwater scientist wants to see it at some time in their life, but very few of us in the West have had that opportunity. In part because it's located in a remote part of Siberia, and it's difficult to travel in Russia if you don't know the language.
Lake Baikal. Image courtesy of Marianne Moore
What can you tell us about the history of research in the lake? is it true that there's been one family of Siberian scientists who have done multi-generational studies?
Yeah, absolutely. The lake was first studied back in the 1800’s. I mean, there's been a number of freshwater scientists, Russian freshwater scientists who have worked there. There's a very long history of work on the lake. Now, I basically stumbled upon this family. Three generations of the Kozhov family have studied Lake Baikal, beginning in 1945. So Professor Mikhail Kozhov, he began initiating a data collection program in the Pelagic waters of Lake Baikal; a very intensive sampling program that involved going out every 7 to 10 days, even through the ice in the winter, and collecting samples at 8 different deaths, down to about 250 metres. And so they (his staff and students) were quantifying water temperature, water transparency, and then phytoplankton, biomass, phytoplankton species composition. And when Mikhail Kozhov died, his daughter, Olga Kozhova took over this program, continuing it. And when she died in 2000, her daughter Lyubov Izmest'eva, who is my colleague, continued, and sustained the program until about 2011. That's when she retired, and the program is still continuing. So there's more than 80 years worth of high resolution plankton data that has been collected. The Russians are superb taxonomists, and they have identified the phytoplankton into species, and they have even aged the zooplankton.
Amazing. It's quite active as a research site with biology. But there's also a neutrino telescope there as well, because of the super clear water.
That's absolutely right. There is a group of physicists who are very active on this lake, and they study subatomic particles like the neutrinos. They hold an international conference at the biological station where I have worked every summer, and physicists from all over the world come there to present talks and learn more about subatomic particle research. But they're also scientists from many other countries. Hydrodynamic scientists, hydrologists, biologists, oceanographers who come to Lake Baikal.
And there's a lot of interest in the sediment as well, isn't there? Is there some like 7 kilometres of sediment, and because it's such an old lake, it preserves a huge amount of earth's history.
You're absolutely right. Paleoclimatologists come there to work and some of that work has gone back in time 800,000 years. The lake is more than 25 million years old and that record is down in the sediments.
It's amazing. And there's been some sub work as well?
Yeah, yes, you're absolutely right. The Russians have taken the Mir submersible. I think there's a Mir II now. They have gone down multiple times to the lake floor. In fact, President Putin has even gone down to the lake floor in Mir, I think that happened in 2009. And he declared that the lake was clean.
Can you lay out the biological conditions?
The Baikal Seal. Image courtesy of Nina Zhavoronkova
I'll talk about the ice first. The ice cover can last 5 to 6 months. (Five months in the southern end of the lake, about 6 months up in the north end, because this lake is so long - it's over 600 kilometres in length - there's a seasonal delay between the north and the south end). And the ice is absolutely essential for the lake's pelagic food web. There’s the Baikal seal, which is the only true freshwater seal in the world, and the phytoplankton. Both of those groups of organisms require ice for reproduction and population growth. For example, the Baikal seal gives birth in ice caves or ice burrows that are scratched out on the surface of the ice, and this is where the pups live for the first 1-2 months of their life before they enter the water. And those caves are very important because they protect the pups from terrestrial predators like crows, humans, and bears. Another interesting aspect to the ice, is that it influences the fertility of the female adult seal. The adult seals moult on the ice every year, and moulting is energetically expensive. The seals do not feed when they're moulting. Now, if the ice goes off exceptionally early, which it does in some years, moulting is then delayed and that causes female fertility to decline, by as much as 60%. So you can see how important that ice is to the seal. And then the phytoplankton, there's a very important group of phytoplankton called diatoms. These are endemic, found nowhere else in the world, these particular species and their maximum population growth occurs under the ice, because they prefer dim light. The ice reduces the light to an optimum level for maximum photosynthesis and population growth.
And that brings up a point that I think surprises a lot of people. There isn't that much snow that falls in this part of Siberia. I mean, there certainly is snow in the winter. But the most important point here, is that there's very strong winds in winter, and what little snow falls is blown off the ice. So the ice in parts of the lake can be exceptionally clear. But the ice, even though it looks like glass, it's attenuating or reducing the solar radiation in spring to an optimal level for the phytoplankton to grow. And some of those phytoplankton will even attach to the underside of the ice, such as what we see in the Arctic.
So if we're getting through the ice and we're down into the water now, there's some unique features isn’t there?
Yes, there are! Now, it should be no surprise to anyone that the temperature here is cold. It's a very cold lake. Surface temperatures average 5.C annually. Once you're below 20 metres, which is the bottom of the thermocline, temperatures are pretty much constant. They're about 3.C all the way down to the bottom of the lake. So quite similar to the deep sea: cold, constant temperatures. And the oxygen concentrations in Baikal are very high throughout the entire water column, all the way to the lake floor. And I think there's a difference between Lake Baikal and the oceans. There's no oxygen minimum zone in Lake Baikal. And let me emphasise another point. This is the only deep lake in the world with oxygenated deep waters. And when I say ‘deep lake’ I'm talking about lakes greater than 800 metres. And this is really important because it allowed the evolution of multicellular life in the deep depths of Lake Baikal.
And then, just to make it even more incredible… at the very bottom, we've got geothermal activity as well. We've got vents! We've got seeps!
Photo of the Frolikha Bay vents from inside the submersible Mir. Image courtesy of Selmeg V Bazarsadueva.
Yes, absolutely. Those are just fascinating. And it is because oxygen is present down at that deep depth. You have this geothermal activity which is releasing methane, at methane seeps and vents. And the Baikal hydrothermal vents are similar to those in the ocean, chemically, but their physical environment and the animals in Baikal are very different. And let me say something about chemistry first. In Lake Baikal, just like in the oceans, there's lots of dissolved oxygen, lots of dissolved carbon dioxide and methane at these vents and seeps. And so, you have all the chemicals necessary for these chemoautotrophic bacteria. And they're just incredible, in my opinion, because they can make sugars using chemical energy rather than solar energy. So they, (these bacteria) sustain life; entire food webs where there is no light. And there is no light in Baikal at the vents, which are down at around 400 metres in depth. The seeps are even deeper!
Now let me say a little bit about the physical environment of vents in Lake Baikal. The temperature of the fluid coming out of the vents in Lake Baikal is much cooler than what we see in the ocean. The maximum temperature is about 16 degrees C. But of course, that's considerably warmer than the ambient cold waters, which are 3 degrees C. Now in the oceans, the fluid coming out of the vents can reach a maximum well over 400 degrees C, so ocean vents are much hotter. Now, another difference between the physical environment of the vents in Lake Baikal and the ocean, is that there are no black smokers or chimneys in Lake Baikal. In the ocean, for example, in the Pacific, you see this black fluid emanating from the chimneys at the vents. But the vents in Lake Baikal are located on a soft substrate, and that soft substrate is covered in a mat of this bacteria that can manufacture sugars and sustain food webs and the macrofauna. Let me say just a little bit about the macrofauna. It's very different fauna at vents in Lake Baikal compared to the oceans. At Lake Baikal you see low-growing sponges that are white, grey in colour. Plenaria, or flatworms and small crustaceans, such as arthropods are present. And there is a fish that has been fairly recently described that appears to be associated with these vents. It's an endemic sculpin called Neocottus thermalis, which you know, is a nod to the warm temperatures that this fish is encountering. But the important point here is that the vents at Lake Baikal do not have the colourful large tube worms, or the giant clams that we're familiar with at the Pacific vents.
Now if we quickly turn to the seeps. At the seeps in Lake Baikal there are amphipods, giant plenaria (flatworms), oligochaetes (freshwater segmented worms) and… this is the big surprise… there are aquatic insects down there at 1300 m depth. And these insects are midges, or what we would call flies. The adult life stage emerges from the water, and it looks a bit like a mosquito, but it's non-biting. And it's thought… I mean, no one knows. No one knows how these insects ascend that deep water column to get up to the water surface to emerge, when they're ready to pupate. But it's thought that the bubbles, the bubbles of gases, such as methane, that are associated with the seeps help to carry those insects up to the surface.
where have these animals originally come from? How was the lake originally populated, and how have they now specialised in these weird ways?
Oh, I think that's still a mystery how these species have arrived. I mean, one potential way they could have entered is via rivers, and that's certainly the hypothesis regarding the entry of the Baikal seal. I mean the hypothesis is that the ancestor the Lake Baikal seal was related to (or possibly even a ringed seal up in the Arctic) during the last glaciation, it travelled down the river. The Angara River is the only outlet from Lake Baikal, but it empties into the Yenisey which then empties into the Arctic. But the major rivers in Siberia flow north, and it's kind of counterintuitive to many of us. So anyway, it's thought that the ancestor, the Lake Baikal seal, travelled from the Arctic, through this river system into Lake Baikal where it evolved into the Lake Baikal seal, and remains today. But regarding the other species, I think some of them may have entered the lake from freshwater springs that are found in and around the lake.
so the fish are mind-blowing. we've got the deepwater sculpins, the oilfish and then there's the Baikal sculpins as well, which are technically a different family.
The Baikal oilfish (golomyanka) A- Big Baikal olifish Comephorus baicalensis-pallas. B- Little Baikal oilfish. Image originally sourced from Teterina et al (2010).
No, you're absolutely right. And what you're describing are the two endemics, the two pelagic endemics which dominate the fish biomass in Lake Baikal. These two species are referred to by the Russians as the Golomyanka, that's the Russian common name. And these two species, their biomass across the lake surpasses that of all other fish in the lake. I mean, they're very abundant because they're found from the bottom of the lake up to about 300 metres. They're very strong vertical migrators. And yeah, their physical characteristics make them look like they belong in the bathyal zone of the deep sea. I mean, they look like they came straight out of that depth, you know? A depth below well below 1,000 metres in the oceans.
So my students and I have worked with them a bit and they have no pigmentation - they're white in colour. They look like an albino fish, because they live in perpetual darkness, so why be colourful? They have tiny eyes, again because they live in pitch black. They have very large mouths for consuming anything that comes by, which includes each other. They are cannibalistic. And their body size is small. There are two species: the large and the small golomyanka and the large one, its maximum length is 20 cm. So these fish are small. And they're, as you mentioned, very oily. They don't have a swim bladder, because the swim bladder would certainly be disadvantageous if you're moving up and down that water column every 24 hours, a swim bladder would either implode or explode.
The Russians also call this fish the ‘candle fish’ because Russians in the old days used to dry the fish and burn it like a candle, because of its high oil content. So that gives you a sense for how oily these fish are! And then another feature that harkens to the deep sea fish is that the golomyanka are viviparous. They give birth to live young, as do many of the fish, I believe in the deep sea. And they're just amazing fish to see in the water column, because they have these very large pectoral fins which they hold out, and they sometimes float upside down, with these fins extended outwards. And so another common name that you hear Russians use for them is the angel fish, because these fins look like the wings of an angel.
And then I'll mention one more thing that's always surprised me about this fish. You know it's very abundant in the lake, certainly in terms of biomass. But there's no commercial fishery for it and that is, in part, because this fish is solitary. It does not school, and so that makes it difficult to harvest it. And because it's such a deep dwelling fish, you know that that doubles the difficulty.
I mean these are fishes in the sub-order cottidae, which is the same as the snailfishes that we find in the deep trenches. plus, it's really interesting that we're seeing similar body forms. And there's another parallel as well, because one of the most abundant things we see in the trenches is amphipods, and they are nailing it here as well.
That’s right. They absolutely are in Lake Baikal. I didn't know about the abundance or the presence of amphipods down in the deep trenches. That's very cool.
So amphipods - they’re the group of organisms in Lake Baikal that have speciated the most. There are well over 350 species of amphipods in Lake Baikal. And all of them, except one, are benthic: living on the substrate. But 98% of them are endemic- they're found nowhere else. And to help your listeners, appreciate how amazing this is: there are more than 350 species. Most lakes have about 2-3 species in them. So the amphipods are kind of like the Galapagos finches, you know, they've really adaptively radiated in Lake Baikal.
The baikal sponge. Image originally sourced from Belikov et al (2007).
One of the groups that I really enjoy are the sponges. These sponge forests look like something that's come out of the Caribbean or the Great Barrier Reef, because there's a family of sponges that occur in the nearshore waters from about 4 metres down to 20 metres, and they do form sponge forests because they can stand as high as 50 cm. They're highly branched, and they're a vivid emerald green because of a symbiotic algae that lives in their tissues. They are stunning. But there's a very sad coda to this story. And that is, that a pathogen has swept through the nearshore waters and has killed many of these sponges.
Oh, no! Oh, that's a shame! I saw the images of them, and you know a lot of people don't even associate sponges with fresh water systems, let alone forests of ones half a metre high! They're stunning. You'd think they were a plant if you weren't getting close enough.
Divers come from all over the world to see those particular sponges. But they are very, very hard to find now, and they're very slow growing. I mean, there's estimates that it may take another 100 years for those to come back.
“There is a local legend among Russians that the Russian Mafia prefers to dispose of human bodies in Lake Baikal because there’s nothing left after 48 hours. There’s no flesh left, that’s for sure. ”
There's a good scavenger community here, isn't there? I think you did some experiments. There's a good cleanup crew.
Yes, there is. There's an outstanding clean up crew in Lake Baikal. There is a local legend among Russians that the Russian Mafia prefers to dispose of human bodies in Lake Baikal, because there's nothing left after 48 hours. There's no flesh left, that's for sure. And my students were very intrigued by this, and we tested that hypothesis by placing baited fish traps along a depth gradient. I think the deepest depth was 200 metres. That was a funny experiment, because the captain of our ship insisted that we bring those traps in before 48 h because he was worried there would be nothing left, and so we finally gave in and brought them in slightly less than 48 hours. And he was right! At least a third of the traps were completely empty of all the fish - and there were a lot of fish in those traps! And then, 75% of the fish was gone in all of the other traps. But what was in those traps were amphipods. I mean, there must have been 200 to 300 of them in each trap. And they're really quite small. They look like orzo, you know, about the size of that pasta - maybe a centimetre long. But wow! I was impressed by that, and to give you another example of how effective they are at scavenging: fishers in Lake Baikal still use gill nets, and if that gill net is floating a little bit close to the substrate, those amphipods will will jump up onto that gill net and basically eat all the fish. So they're pretty impressive.
Oh, this feels super super familiar. I can send you some pictures of some deep sea traps that must look exactly like what you're describing, cause that's exactly what we find.
Oh my! I would love to see some pictures of that, or some papers about that.
We've got some gigantism as well - some big scavenger amphipods. The one that really leaps out is the supergiant - that is like 30 cm long.
And it's an amphipod? I mean, I've heard of the isopods… the giant isopods. But wow! An amphipod! The deepwater amphipod in Lake Baikal is an example of an abyssal giant. But it's only the length of a mouse. But that's a real dwarf compared to what you've just described.
Yeah, they're clumsy, uncoordinated beasts. They’re good at what they do, but they're horrific little monsters.
Yes, yes, they are. I'm really amazed at their olfactory capabilities, because I think that's how they're sensing these food falls that fall to the lake floor. They must be recruiting from great distances, you know, for a small amphipod. It would be fun to look at that. I imagine the same thing happens to the Lake Baikal seal when they die. They're probably gobbled up by these little amphipods.
Before I forget, there's one other abyssal giant in Lake Baikal that I've been very impressed with. I've only seen Russian video footage of it, but it's a flatworm and it's 30 to 40 cm long, and it glides across the bottom of the lake floor like a flying carpet. I mean, it really moves, you know. It just kind of undulates across the lake floor. And this was absolutely stunning for me, because freshwater flatworms… the largest are about 5 cm long, and to see something that big was really jaw dropping.
So another aspect that your research touches on is human impact and human influence on the lake. What are the human impacts on the lake? Or is it the global human impacts? Is it our effects on climate?
No great question. I think the opinion of many people right now, many aquatic scientists, is that the greatest threat to Lake Baikal is a local threat. It's unregulated development and lack of sewage treatment along the lake shore. Because untreated sewage is flowing into the nearshore zone, and that's where the greatest number of species are, in that nearshore benthic environment. And this started back in the early 2010’s. Tourism absolutely exploded at Lake Baikal and there are not adequate facilities to cope with this. This explosion of humans visiting the lake. Not even the Russian dacha… (the small vacation cottages that the Russian’s use) they don't even have sewage treatment. All of the dachas are serviced by a cesspool, which is simply a hole in the ground into which human waste goes. And of course that waste makes its way into the nearshore zone. And a whole host of problems have cropped up from that from E. Coli being in the water, which is very dangerous to humans if they drink that water. When my students and I first went to the lake in 2001, we could drink the nearshore water without any treatment. You would never do that today. And then there's toxic cyanobacteria. And the real problem is the explosive growth of a green alga that grows on the substrate. It forms these green clouds of filaments and can smother life underneath it.
So in the short term, over the next 20 years, this problem has really got to be tackled. And in the long term, I think you're right, there's a global problem on the horizon. And that's climate change. Because there are ice dependent species in this lake. The duration of ice cover is shortening, ice thickness is being reduced. And then, of course, there's the warming of the water which we've documented using the Russian 60 year data set. And many of the endemics in this lake are cold-loving species. They have a narrow temperature tolerance range. So there's a lot hammering at Lake Baikal right at the moment, and in my opinion, the number one thing that has to be tackled first is the problems in the near shore zone, because with climate warming, that problem will only become worse.
What is it like to study in this area? What did your visits feel like? Obviously, it's quite remote. There'll be a lot of travel. And then what's a day in the life like studying.
Oh, well. I'll start with the travel. Travel is gruelling. It really, really is. I mean, once you get to Moscow, you've got a 6 hour plane ride to get to Irkutsk. That's the nearest large city, and then there's a bus ride or car ride about 45 min out to the nearest port. And then you take a ship. This is what we've always done. And then we take a ship for about another 45 min north along the lakeshore to the biological station where we've always worked. And so, when we arrive we feel like we have travelled to Mars. We are very, very tired and badly jet lagged.
A day in the life. Yeah, good question. It's just wonderful. It's so wonderful being there. The temperatures in summer are surprisingly warm, you know. It can be well over 30 degrees C. during the summer there. But being out in the water is just fabulous. There are mountains on both sides of the lake on the west side. It's just lovely, you know, having those mountains there, and very narrow valleys with streams coming down to the lakeshore, and each valley has its own personality. I really enjoy hiking there. I hope that gives you some sense of what the lake is like. And the Russians are just incredibly hospitable. We have found them just very warm and curious. Many Siberians have not travelled much beyond Russia. And so they're curious about the world and interested in you and if you can muster or learn any Russian, they will be absolutely delighted.
Lake Baikal’s endemic species. Illustration courtesy of Georgia Wells
Is there one message you'd like to leave people interested with?
Oh, well, there is a fun legend I'd like to mention, because it plays off on your shipwreck episode which I really enjoyed. The legend is: that there is 1,600 tons of gold at the bottom of Lake Baikal, and this is the gold of the last Tsar of Russia. People were trying to get the Tsars' gold out of Russia, and so the gold was on a train that plunged through the ice of Lake Baikal, during the Bolshevik Revolution in the early twentieth century.
And last year, explorers using a submersible found rectangular blocks on the lake floor at the south end of the lake, and those rectangular blocks had a metallic glean to them. But the manipulator arm on the submersible failed. So the blocks could not be retrieved. I'm hoping that an expedition occurs this year to verify that legend.
That's incredible. Oh, that'd be exciting. So that might be something we have an update on in the next year.
That's right.
Oh, that's exciting! Oh, that's a great one to leave on. Thank you so much, Marianne. I knew it was going to be exciting, but that was amazing.
Well, thank you Thom! Please do send me some of your papers and your pictures. I so much enjoy listening to you. I want to see… it's a snailfish, right? I want to see that. And I want to see those amphipods. Those are the gigantic ones in the little ones, and it was just a delight to talk with you.