Episode 3: Dr. Amanda Kahn

The Accidental Geographer’s Vincent del Casino speaks with Dr. Amanda Kahn, Professor of Marine Science at SJSU’s Moss Landing Marine Labs, who is one of the world’s leading experts on sponges, about the role sponges play in global climate change. 

Episode Transcript

Vincent del Casino: Welcome to this episode of The Accidental Geographer. I am the accidental geographer, Vincent del Casino. With me today is Amanda Kahn, Professor Marine Science at San Jose State University's Moss Landing Marine Labs. Today, we move from the terrestrial landscapes of human experience to the explorations of the deep sea. Dr. Amanda Kahn is one of the world's leading experts on sponges, one of the most ubiquitous animals in our waterways today. In this conversation, we learn not only about the complex life of sponges, but about the sophisticated methodologies it takes to study them. While speculative, this conversation also conveys the important sense that sponges have a role to play in our ongoing struggle against global climate change. So let's get right into it.


Vincent del Casino: All right, so Amanda, welcome. Thanks so much for taking the time to have a conversation with me about your work. I'm really excited to delve in and learn about the things you're working on.

Amanda Kahn: Fantastic. Yeah, thanks for inviting me to come and talk to you today. Any opportunity to talk about sponge biology and deep sea biology is a great day in my books.

Vincent del Casino: I'm always genuinely curious how people end up interested in what they're interested in. At the first level, you cut -- you clearly have this passion for marine science and ecology. You know, how did that get cultivated in you and why, why that trajectory for you?

Amanda Kahn: Right. Yeah, so you're right, I did not initially have an interest in sponges. That's not really a good gateway animal into the sciences, I think. So yeah, I was a volunteer at a wildlife refuge, The Don Edward San Francisco Bay National Wildlife Refuge. I grew up in the Bay Area, and that was my local refuge, and I went there as a camper. And then I went as a camp counselor. And I got to meet all the counselors there and learned about environmental education and got interested in ecology through those means. And then when I went to college it was just biology was my declared major, I didn't really have another thought or other one that I ranked differently. And then in -- when I was doing my undergraduate degree, which I did at Cal State East Bay, I thought that I would like to study marine science because I thought that marine mammals were really cool and interesting. And I'd heard about Moss Landing Marine Labs and how it was affiliated with Cal State East Bay. And so I tried to look into taking classes there and got connected to MLML by Dick Tullis, who was a retired professor there at Cal State East Bay, and he was part of the governing board. So yeah, he got me down there and helped me find out how to take classes. And after I took my first marine science class, I was hooked. So that's how marine ecology then happened after ecology was my grounds. Sponges came later.

Vincent del Casino: What's interesting about this is, we all find our way into these topics for all kinds of reasons that are often not, you know, there's no way I would have thought even when I started college, that geography was going to be my thing, and that's where I'd end up and so forth. So it's always interesting to figure out how people, you know, learn to focus. And so you went on to Alberta, right. So you went to -- so to do a doctorate, and is that where the sponge thing happened? Or did the sponge thing start to evolve with the work at Moss Landing?

Amanda Kahn: Yeah, it actually happened there a little before Alberta. So when I applied to Moss Landing Marine Labs as a graduate student to work with John Geller, who's an invertebrate zoologist. So by that time I had decided, you know, inverts in general were cool. You can ask questions with invertebrates, like does it have eyes, does it actually have a head. And you never asked those questions about a vertebrate, so already that world was opened up to me. And then I took a field course doing subtitle ecology, so diving, basically science underwater. And we spent our time identifying sponges and sea squirts and bryozoans. And I thought they were fine, and that was how I got a little bit of expertise. And then I also left out right before starting at Moss Landing, I got an internship at the Monterey Bay Aquarium Research Institute. And when my intern mentor asked me what I knew about I said, well I know a little bit about sponges and tunicates and bryozoans. And he said, great, you're going to study sponges. So that's how it happened. And after I started reading about them, by the end of the internship, I was like wow there's so much we don't know about them and they're so strange. So my masters at Moss Landing was actually a little bit -- well it was about sponges, and my interest was a little bit about sponges. And by the end of that I had read a bunch of papers about deep sea sponges. And the person whose name showed up on many of the papers that I had kind of bookmarked as my favorites was Sally Lee's at the University of Alberta. And when I emailed her, I said like I've read a bunch of your papers, I think your work is still cool, here's what I want to do. And she said, I need to point out, do you know where Alberta is, we're not near the ocean.

Vincent del Casino: Well that's my theory, that was my next question.

Amanda Kahn: Yeah, so it was really the person. And I talked to her and wanted to work with her. And so we worked it out, like to do deep sea work you actually, you know, you need a ship, and you get ship time. So your field time is really constrained. So we would load up my PhD advisor's SUV, filled to the brim with totes and bags and boxes of gear, and then we would drive 14 hours to the coast and load them up onto a ship. Sometimes we would live on a sailboat for a couple of days, trying to like have a home base there to build the gear and get it ready. And then the other thing is they had a field station affiliated with the University of Alberta. So I spent one to three months out of the year living out at Banfield Marine Sciences Center. Which is kind of similar to MLML in that several campuses can have students go there and spend time there. So that worked out really well for a landlocked marine scientist in Alberta to be able to go and do my fieldwork out there.

Vincent del Casino: Awesome. So what's the category of sponges, kind of definitionally? What is a sponge, exactly, in relation to other invertebrates zoologically?

Amanda Kahn: So well that's a really good question. And honestly, it's kind of funny that it's still sometimes up for debate. But sponges are animals. You can see just barely. Sometimes taxonomically they would be called the Parazoa, which means that almost animals. But they are true animals. And they're one of the earliest branches of animals that branched off from the last common ancestor of all animals. So that's why they look so different. And also because they follow this very divergent path to become filter feeders. Yeah, so they evolved about 600 million years ago during the Cambrian explosion.

Vincent del Casino: And you've become interested in the deep sea area within that. Because obviously sponges exist at all, I think, from what I understand at least from reading a bit, you could find sponges at a variety of sea levels, right. But you've become interested in the deep sea. Why deep sea interest? Like what's there that really attracted you to that question?

Amanda Kahn: Yeah, a lot of my questions ended up coming up because of sponges being these really strong filter feeders. We use this nontoxic fluorescent dye that we inject near the outside of the sponge. And with that you can see this plume of dye coming out of the sponge, and you realize just how much water they're pumping and processing. And with that we started looking at how much sponges process and eat and affect the water. And they eat a ton. And they do things with that, right. They take carbon out, they pee out ammonia, you know, they're changing the water chemistry. And somewhere like the deep sea, there's not a lot of food to go around.

So a lot of the animals that you look at in the deep sea are these bizarre, reduced forms, or these animals with these strange alien adaptations, like fish with lures on their heads, angler fishes, or the barreleye spook fish with the eyes that can kind of rotate in their heads and bioluminescence galore. So all these things come about because there's not a lot of food to go around and animals need to find ways to creatively either save energy or find food, or both. And then you find these places in the deep sea where there are sponges covering the rocks. And I wondered like, how can sponges get away with that? What are, like what are they tapping into? What are they eating down there? And then also, could they be, you know, could their presence be actually serving some function for the animals around it? So that's why the deep sea's cool to me. Other places that are food poor are also interesting in the same ways. So you are right, sponges show up everywhere, including freshwater. So you can even find them up in lakes around Lake Tahoe and there as well, it's kind of a food poor habitat in lakes, or food limited. And sponges can have a pretty strong role there too.

Vincent del Casino: Is it -- I was looking at one of your recent presentations and you talk about them as foundational species. So what does that mean exactly in the context of this ecosystem with the deep sea?

Amanda Kahn: Right. So a foundation species is an animal or plant, a species that forms 3D habitat. Basically forms the foundation of a whole community and ecosystem. So you could think also maybe of tree, as a foundation species. Without trees, you wouldn't have the forest that would then support the sorts of understory growth and the squirrels and the birds that would live among the trees. And in the same way in the deep sea, and in shallow water, sponges can serve that role of growing up and then creating a habitat just by their presence that attracts a certain community of animals.

Vincent del Casino: That is just so interesting. Because to your point, they remain incredibly understudied. In fact, as I was reading your work, your research is clearly generating a lot more questions than answers. I mean there's so many like, well we don't know yet, we're hypothesizing this, we've got to do the next study. And it's not just to set yourself up for the next NSF grant. It's because there really -- there's a dearth of literature in this space. What -- why do you think that is for this foundational species, that there's this absence of work?

Amanda Kahn: Oh, oh, that's a good question. I think there are a couple things that could be involved. One is that they're hard to understand. They're so different from us that, you know, they don't have organ systems that we can recognize. So we can't do some feeding study like we would do with a fish, where we might look at the gut contents of fish that have died, or we could look at poop and collect poop. I actually spent three years of my PhD trying to collect sponge poop, which I finally got. But like they're so different that you can't quite recognize and work with them easily. So I think there's a big roadblock in just being able to understand what you're looking at that's an impediment for people to move into studying them in lots of different in depth ways.

And the other thing, a little bit is in the way that we teach about sponges. So I remember the first class that I learned about sponges, we were told that they were well barely animals, and really just these stepping stones and aggregations of cells towards some higher level of complexity. So they suddenly didn't seem interesting. It seemed like oh there's not much to know about them, other than they were some step towards some more interesting animal. And now, I don't think that at all. Like I think that what's fun about them is how different they are. We still end up finding these similarities, or these things that clearly show that they are important ecologically. Evolutionarily that they're definitely animals and have a lot of the same sorts of needs and signaling systems, and types of animal-like traits that we all have. And so they're just, they're tricky.

There was a really great paper published a few years ago that I thought the title was really good. It was called The Hidden Biology of Sponges and Ctenophores. And I think the term hidden biology is just really neat, because it's this idea that we -- we're trying to study animals, but we're looking at them always from a lens of a human, or of a bilaterian animal, which is one with bilateral symmetry. And so we always have this lens that prevents us from really getting to understand the animal and think about how it might work in its own way.

Vincent del Casino: And I imagine, and again from reading your work, that this presents methodological challenges of what -- how are you going to attack these sorts of questions. But I want -- and I want to get to that in a minute. But before, I don't want to lose sight of -- so in your -- one of your papers, The Behaviors of Sessile Benthic Animals in the Abyssal Northern Pacific Ocean. You talk about like the stationary nature of them as well as maybe producing a lack of interest. And the challenge, because they don't have this mobility to them, which to me is really interesting. It's like and yet there are some of them that do move around. And it seems to not affect them and things like -- so there's all this work -- stuff going on. But can I ask what a sessile benthic animal is, before I go any further, or for the audience? Let them know -- do the work?

Amanda Kahn: Oh no, I use jargon.

Vincent del Casino: No, it's all good.

Amanda Kahn: Sorry.

Vincent del Casino: It's all good. They -- I just want to make sure people know what you're talking about.

Amanda Kahn: Yeah, so sessile means attached to the sea floor. So it's something that's stuck in one place like a sponge or a coral or a tree, I suppose. We tend not to use that in terrestrial terms. But that makes sense. And then benthic means living on the seafloor versus drifting through the water column.

Vincent del Casino: Got it.

Amanda Kahn: So sessile benthic things don't move around, they're stuck in one spot, and they're stuck with whatever conditions they grow up in.

Vincent del Casino: So in that paper, you talk about that we don't yet have any clear data to make all the conclusions we want, and on why these sponges spend so, long periods of time also in contracted states. Because you're talking about their role and like they eat a lot and so forth. And yet, most -- their movement is limited, right. And sometimes particularly in these deep sea spaces.

Amanda Kahn: Yeah, well and we didn't even know that they were moving. This again is one of our problems of how we look at animals. We look at them moving at the pace of life that we move at. And I don't want to get too philosophical here. But I guess just picture a squirrel and try to think about a squirrel's life and how fast paced it looks to us and probably to a squirrel, that's normal. Well likewise with a sponge, we had a really fortunate view with this time lapse camera that got sent to the sea floor and just happened to be looking at a sponge on the sea floor. And that camera took a photo every hour on the hour for five months. So we had five months of hourly photos that included this sponge in it. And as we were reviewing the data back on deck, we noticed that the sponge was changing size over time. And it took it four days to contract down to the full small size. And then it would sit that way for a while. And then it would expand up again to its full size, then it would contract. And I mean this was something that was happening on the scale of weeks. And we just never would have thought to notice it. So therefore before we had that view, sponges just kind of looked like lumps on the seafloor. And now suddenly we think, oh these animals are contracting and expanding, which means they're active, and they're changing and responding to something in the water around them. And that is a next step is to try to figure out what correlates with when those sponges are expanding and contracting, and try to figure out why they're doing it.

Vincent del Casino: I actually think the philosophical question is critical here. Because it's the anthropocentric nature of the work that presumes to embed, you know, look at the animal from a human perspective. And this animal doesn't care that we're there or not. And it's doing its thing on its timescale. And it's perfectly happy to do it that way. And it's done that for 600 million years. Right.

Amanda Kahn: Totally. And can I just pull up, give me a second. I want to pull up this quote. It's my favorite quote about sponges and very eloquently says what you just said.

Vincent del Casino: This is why what's so interesting is about the insert to the in place work that needs to be done in the deep sea. Because otherwise when you remove these, right, I know you do some research based in labs, right. You pull those animals in and you do some things. But you probably wouldn't capture this kind of work in a lab space, right? It would be very difficult.

Amanda Kahn: Well no, although some sponges are faster than others in their responses.

Vincent del Casino: Oh OK.

Amanda Kahn: So I was doing lab work on this sponge, Geodia barretti, which is a deep sea sponge in the North Atlantic. And we were at a field station, or I was there by myself at that point, field station in Norway. And I was there by myself late at night trying to do these measurements of sponge pumping and respiration. And they're so sensitive. I would put the sponge into the respiration chamber and then I would have to let it sit for hours until it kind of like perked up and started pumping again. And I guess was feeling happier about its state. And finally, at 10:00 p.m. at night it was pumping. And I said, you know what, I'm just going to start my experiment now, we're going to work through the night because the sponge is happy. Let's do this. And I turned on some music to just kind of keep myself going. And I watched as the sensor that I had inserted near the sponge show the sponge just stop pumping. And I realized, sponges don't like Green Day, which is a problem because they're great. But like whoa, it's pretty shocking. And so yeah, we can have big effects on them from all the handling that we do in the lab. And we don't even know what they're affected by. Because sponges don't have nervous systems and they definitely don't have ears. So I don't know how it knew about Green Day. But I mean I'm sure the pressure waves in the water or something were enough to trigger it to stop pumping.

Vincent del Casino: Well it's just an interesting question of, you know, their own sensitivity and so forth through the changing environment which is why they might be good indicators for a lot of other things, I think as well. Did you find your quote?

Amanda Kahn: I did

Vincent del Casino: All right, go for it.

Amanda Kahn: This is by Biter, in 1923. And he was talking about the deep sea sponges that I tend to study. And he says, food is brought to them, waste is taken away. For them in their eternal abyss with its time like stream, there is no hurry, there is no return. Such an organism becomes a mere living screen between the used half of the universe and the unused half. A moment of active metabolism between the unknown future and the exhausted past. Don't you wish we could still write that way in papers?

Vincent del Casino: Yeah, I know, well that's, yeah. Well I think we can, it's just a matter of we have to challenge each other a bit I think in our scientific writing. I think that's -- it is really interesting because they sit here and I was reading. I mean I started thinking of carbon sequestration issues. I started thinking of global climate change. I know that's not yet where your work is. You're trying to get it like the fundamental nature of their kind of lived experience. But clearly, they're playing into this much more complex ecosystem. And actually seems to me, at least from the reading, a very critical role in the deep sea space as you're studying in terms of the life of the other things around them.

Amanda Kahn: Definitely. Yeah, actually, that's been one of the I think the most exciting discoveries that have happened along the way of doing this, is realizing how important sponges are in creating a bridge between the microbial carbon loop, which is this, you know, this sort of closed, otherwise closed loop of carbon cycling between bacteria, and protists and microscopic critters. And animal food webs, because most animals can't eat bacteria but sponges can. So suddenly you have these food oases or food transformers in a sponge. So sponge eats the bacteria, turns it into either sponge tissue or sponge excretion. And that becomes something that's edible for other animals. And in a place where food is limited, sponge poop is probably a pretty good resource to tap into to try to get, make a living.

Vincent del Casino: Now I totally know why you're trying to collect sponge poop.

Amanda Kahn: See. It's not so much, so weird, but I promise it made for some interesting seminar titles.

Vincent del Casino: Yeah, I suspect that's right. But let me ask this just methodologically, again, what have you been able to do in relation to those excretions? What are you able to understand about that food cycle?

Amanda Kahn: Oh. Yeah well, I did finally catch sponge poop from the deep sea sponges. And here's the neat thing about it. The sponges were able to catch particles as small as 100 nanometers, which is definitely on the small range of bacteria. Still bigger than viruses, but tiny, tiny and much smaller than other animals could catch. And so from that, sponges were capturing and concentrating bacteria from the water that they were pumping through their filtration system. Eating that. And then the fecal pellets that I collected, were these aggregates of, you know, bits of the undigested food all packaged up in a fecal pellet, that was 100 to 1,000 times larger. And by the time you get 100 to 1,000 times larger, it's something that's big enough that it would sink into the sediments where things like sea cucumbers and other deposit feeders could snuffle around and find and eat that sediment and eat that poop. So that's it. Is have seeing that they really are taking that food and packaging it in a way that's important to other animals.

And the other thing is just how much water they process and how big of an impact they can have. So you said you can see rolls of them in proteose sequestration. And I think you're right. We were trying to do some calculations of that based on the pumping rates that we saw for some of the deep sea sponges up in northern British Columbia. And we averaged that the average sponge of the average size up there pumps about 9,000 liters of water through its body each day.

Vincent del Casino: Wow.

Amanda Kahn: And from that water it removes with about 95% efficiency all of the bacteria that were in that water. So it's changing the water. It's also putting out a lot of ammonia, which is a fertilizer for plants, if you're in shallow water and in deep water well it's just there. To be upwelled later. But yeah, it's basically really changing the water chemistry, and they can really have an effect a long distance and a large volume beyond their actual size.

Vincent del Casino: It is so interesting, because this is kind of a sidetrack. But, you know, as soon as I learned about, I probably asked you this question when I first met you, have you ever been to Tarpon Springs, Florida. You know, right, have you ever been there?

Amanda Kahn: No. And we almost went. I was so excited. But I was in a group and my travel plans got vetoed. But would you like to tell people the wonders of Tarpon Springs?

Vincent del Casino: Tarpon Springs is the spawn capital of the world, as they like to define themselves. And some of my colleagues earlier like Greek migrants, in particular, came in to this community and started, you know, bringing sponge in. Because it's a quite popular product, right, I mean in all sorts of things. But obviously, without any understanding of the long term ecological change that that could produce. But it just almost makes me wonder long term should we be thinking about sponge, you know, reintroduction of sponges. Or has anybody started doing any of that work, as we think about the broader chemical impacts and so forth? But the Tarpon Springs thing is, you know, you can get some really good Greek food and buy more sponges than you could ever, ever, ever have in your entire life. Except maybe for you.

Amanda Kahn: That sounds like a dream. I'm going to have to go back to Florida and check that out, with travel buddies who are willing. But yeah. Gosh, yes, I think there have been a lot of efforts to try to farm sponges and to try to rear sponges. The most successful have been the farming operations like at Tarpon Springs where they're growing bath sponges. Which I should say, just as a fun fact, only about five species of sponges can make bath sponges. And that's because most sponges have hard skeletons inside of them, made of either calcium carbonate, which is the same as like a coral or a snail's shell. Or most of them have a, are made of glass. So it's not as nice to rub something that's essentially got fiberglass rods inside of it. But those five species are good. Beyond those --

Vincent del Casino: Duly noted, I will avoid glass sponges when I bathing.

Amanda Kahn: There you go. Yeah, I sometimes get a little too excited when I'm doing fieldwork. And the ROV will come up with sponge samples in it. And I'll go out to go see the sponge, and I'm like, wow, let me just pick this, look at this sponge. And then my hands are covered in the glass, fiberglass, like rash. Oh it's rough. But yeah, so Tarpon Springs and the types of sponge farming like that, where the sponges are essentially seeded and then stay out in the wild. Those work fairly well. Every operation that's tried to bring sponges in and farm them or rear them through aquaculture has struggled. I think because going back to that thing of we don't really understand enough about how sponges work and what they care about. So now that we know that sponges have behaviors, we can see things, like if I direct the water a certain way over a sponge, it inflates up. And if I move the water just a little bit, it will shrink back down and be unhappy. So we might be able to get at that. But people are interested in rearing them, not so much for restoration, but because about 70% of the current drugs that have been derived from marine organisms have come from sponges. So there's a huge medical importance to sponges as resources.

Vincent del Casino: Wow.

Amanda Kahn: Yeah, it's a lot. And there are a lot that we don't know. Actually one that I have been studying in the deep ocean I learned after the fact is showing some active compounds that are active against human pancreatic cancer. So maybe a sponge treatment will come for pancreatic cancer, which would be amazing.

Vincent del Casino: Absolutely.

Amanda Kahn: Yeah. So drug discovery. And then also, those glass skeletal pieces are actually pretty cool, because they are thin glass rods that can conduct light through them, which sounds a lot like a fiber optic cable. But sponges produce their fiber optic cables with just seawater, whereas we need to do it with a lot of chemicals and processing and high temperatures. So there are some efforts of essentially copying or learning how sponges make their spicules so we can make easier and actually also stronger fiber optic cables.

Vincent del Casino: I am actually blown away right now, on the level of which this -- it is really interesting, but it suggests how valuable this space is, and how important it is to keep Green Day away from sponges.

Amanda Kahn: Totally, they should just hang out with me, it's fine. I can teach them.

Vincent del Casino: So one other question on the work, and then I want to talk about a couple of the other things you've been doing. But in the 2012 paper in deep sea research, you talk about temporal changes in deep sea sponges, and I'm quoting you and your colleagues now, populations are correlated to change in surface climate and food supply. So that the kind of cyclical nature of the way water moves through the ocean, right. So you're picking up, sponges can help us read the sensitivities at the surface, is that, you know, sort of what you -- what you're getting out there? And/or how that impacts the food cycles for them?

Amanda Kahn: A little. I was thinking, that's actually really interesting. I was thinking of it the other direction of --

Vincent del Casino: Oh, OK.

Amanda Kahn: Can sponges, are sponges affected by things happening at the surface. So that study was done stay at Station M, which is a long term deep sea study site on the abyssal plane, which is 4,000 meters or over two miles deep. So by -- like it seems strange to think that something that lives two miles away from the surface could be affected by climate that's happening at the surface. Yet what we found in that paper is if there was a plankton bloom, or if there were major storms, or a change in El Nino strength, we would see a resulting change in the sponge populations of about, I think 12 to 14 months later. And when I say that I actually, let's see, that's actually 18 months later because first it takes six months for any changes that happen at the surface to be reflected at depth.

And then it was another year before we saw those changes in sponges. So yeah, that was, by the way, my first study in sponges. And that was when I was an intern learning about them. And what was neat about that is, we didn't actually expect to see sponges change pop -- their population size at all. Because, you know, when you think about something like a sea cucumber, or a sea star, they can move, they can leave if the area becomes inhospitable. And they probably are shorter lived than a sponge. Which actually, we think can live a very long time, several hundreds, if not a thousand years. So we didn't think that we would see these changes on a seasonal or even annual timescale. And yet, we did. So it was actually a pretty big surprise. And also fun fact, because I'm sorry I just love this stuff. Those sponges that we studied in that paper, they're plate sponges. And they are the ones that we learned move around on the sea floor in that 2020 paper that we just published in Deep Sea Research.

Vincent del Casino: Well I was going to ask the mobility question, right. So --

Amanda Kahn: Yeah.

Vincent del Casino: In the cameras and so forth in the time lapsed photography, you found that they have detached, move around. Do they reattach then, maybe somewhere else? Or do they just kind of move around, or we don't know?

Amanda Kahn: Unknown. I kind of consider this some of them, there was one that was kind of tube shaped that had a stock that connected basically like an anchor into the sediments. And if that stock got uprooted, they never rooted again, they would just roll around and roll away. But the plate sponges are the ones that we talked about in that other study. And the plate sponges they never were that strongly anchored. They look -- they're called plate sponges, because they look like a dinner plate. And on the underside they have spines that stick out. Maybe they look more like a comb, than -- or a hairbrush. So those bristles stick down into the sediment and form temporary anchors. So I could foresee that the sponge could get blown around and then might settle down and then might sink a little bit and anchor for a while and then get blown away again.

Vincent del Casino: Yeah interesting. So I want to shift gears just a little, because I know you're now involved in a project in the Davidson Seamount. So where is that? It's an underwater, extinct volcano, right. Tell me a little bit about this project. Who's involved, and that kind of thing? Because I -- and is this where we found the brooding octopuses?

Amanda Kahn: It is. Yes. Yeah.

Vincent del Casino: I never know how to say that in the plural.

Amanda Kahn: Brooding octopuses, hey you did it. You even did the correct plural form.

Vincent del Casino: Oh good.

Amanda Kahn: Yeah.

Vincent del Casino: I messed it up the second time then, but we can just cut that out.

Amanda Kahn: No, we're good. There are several ways. Just apparently not octopi, which surprises me. I'm actually not a stickler for those things. But yeah --

Vincent del Casino: Thank you.

Amanda Kahn: So Davidson Seamount, you're right, is an extinct underwater volcano off the coast of Big Sur. It extends from essentially Gorda up to Ragged Point, or so. So it covers a large span of Big Sur. And it's this huge underwater volcano. And at the top of it are extremely dense and -- colonies or I guess communities of sponges and corals. So you've got these beautiful pink bubblegum corals that can be hundreds of years old, and they're taller than me. I'm not that big, but still like two meters tall, right. And then you've got these sponges that are massive and they just cover the rocks on the top of the seamount. So the Monterey Bay National Marine Sanctuary was going out on the Nautilus, which is a ship that's operated by the Ocean Exploration Trust, to do some exploration of Davidson Seamount. And they wanted to check out what species were there to do more surveys and to check out what was off of the peak of Davidson. So we were specifically exploring this flanking region down at the southeastern corner of Davidson Seamount. And we wanted to see what was kind of growing along that range. They asked me to come along because I study sponges and they knew that sponges are a big part of what's seen at the top of the seamount. And I was super excited to see all the sponges that were there. So we started up, we went out on this cruise in 2018 and had about 30 hours of ROV dive, where we were going along this flanking ridge along the bottom of Davidson Seamount. And it was a lot of mud. There were some sponges, which I thought was super cool, but I think everyone else was getting a little bored. And we collected a few sponges. And then it was a shift change. And we -- it was my shift change. So I was just getting off of a watch. And I say a shift change because this ship runs 24 hours a day. So we would have shifts of four hours on and then eight hours off and then four hours on. So I was like 4:00 to 8:00 a.m. and p.m. shift. So when I finished the ROV set down. Everyone started changing their shift, and I went, oh look there's an octopus. There was one octopus. And we were like, oh that's cool, we're so glad we get to see an octopus. It's always a treat. It's really great.

And then we did our shift change. I went downstairs and kept watching the ROV dive from downstairs on the ship. And when the ROV lifted up, they lifted up over a rock, and they saw just hundreds and then thousands of octopuses all nestled in the rocks there at this spot that didn't look, you know, particularly interesting on a map. But that apparently was a huge brooding ground for octopuses. So thus began an exploration into octopuses, which I, as an invertebrate zoologist, I know about. But they definitely, you know, well they've got brains which sponges don't, and they've got muscles with sponges don't. And so, you know, I learned a lot. And we recognized that all of the sponges, or I'm sorry, look at me I always talk sponge. All the octopuses we were seeing were female. And they were all sitting in this interesting posture where their heads were down toward the rock and their tentacles were extended around their heads. So their mouths were pointed up. And all of the suckers of their tentacles were pointed out. And it just, it looked weird. They kind of looked like basketballs, little purple basketballs. And we set down and we tried to look in close, and we recognized that underneath each octopus was a bunch of 30 to 40 eggs. Some of the eggs --

Vincent del Casino: Wow.

Amanda Kahn: Looked fresh, and some had little eyeballs inside, so you could see a developing octopus inside. But yeah, it's where all the octo moms show up and are --

Vincent del Casino: And no one had ever seen this before?

Amanda Kahn: No, we had no idea that it was there. There was --

Vincent del Casino: Wow.

Amanda Kahn: We found out there was one much, much smaller octopus brooding ground that was found near a hydrothermal vent in Costa Rica, or near Costa Rica. So there's precedent that some octopuses can aggregate in warmer water and find places to incubate their eggs.

Vincent del Casino: Wow.

Amanda Kahn: But in Costa Rica, none of the eggs were viable. So it was actually hypothesized that it was sort of an unfortunate thing that the octopuses had all laid their eggs here. And then because it's near a hydrothermal vent, the water got too warm and all the eggs died.

Vincent del Casino: Right.

Amanda Kahn: But we started wondering why here. And so we've gone back now in 2019 and 2020, my postdoc advisor at the Monterey Bay Aquarium Research Institute, also got involved and we've gone out on cruises as well to study the octopuses. His name's Jim Barry. And so we've gone out now with instruments. I do a lot of respiration work with my sponge work. So we took my respirometers out there and temperature sensors. And we're finding that the water that is right among the octopuses is quite a bit warmer than the water elsewhere. So deep sea is very cold. It's about 1.2 degrees Celsius, which is what, 34, 35 degrees Fahrenheit.

Vincent del Casino: Right.

Amanda Kahn: And just among the octopuses, and among the eggs, it could get up to 10 degrees Celsius, which is like 55.

Vincent del Casino: Wow.

Amanda Kahn: I think.

Vincent del Casino: Yeah, yeah.

Amanda Kahn: Yeah. So pretty big dramatic difference. So there is, even though it's an extinct volcano, there is some warmth or heat that seems to be seeping through in some way from the rocks.

Vincent del Casino: How deep have you ever been?

Amanda Kahn: I have only dove to 150 feet. All of this has been with remotely operated vehicles. So I get to stay comfortably on the surface. But I think your question is how deep have the ROV's gone? So I've been --

Vincent del Casino: No I was generally curious how deep you have gone.

Amanda Kahn: Oh OK.

Vincent del Casino: I was generally curious if you've ever gotten that submarine opportunity or anything. But it is also good, because now you've defined what an ROV is, because I was going to have to ask that question.

Amanda Kahn: That is --

Vincent del Casino: So now we've got that there as well.

Amanda Kahn: That is true. That's a good point. Yeah or yes. So I have not gone that deep. Fun story, maybe fun story. I almost got to go in a submarine to look at the sponge reefs. But I got a flat tire and I got stranded in Banfield. So instead, I had a lovely Thanksgiving dinner in Banfield and someone else got to go in the submarine. That was unfortune. So I haven't gone yet. But I mean, now I've had this taste of almost going, so it's going to happen one day. But yeah, it's a -- it's also actually remotely operated vehicles are nice. You can get up and go have a snack. You can stretch your legs. You can work for, you know, 30 hours around the clock, because you can go to bed and get back up. So I think there are lots of advantages to it.

Vincent del Casino: So the one last question I kind of want to just ask about is, is kind of authorship and the collaborative work of science. Because all your papers have all these people on them and so forth. And it, and very common in the sciences to have. But why this sort of science demand that level of collaboration? You know, and what does that bring to the table for you? You know, as an individual scientist within the larger collective?

Amanda Kahn: Yeah, ooh. I think it brings so much. I'd love to hear how it works in other fields, because I really value the conversations that happen as we're collecting the data. You know, when we're out at sea, we are constantly talking about what we think is happening. And people -- different people are making different observations from their different areas of expertise. So like when I go out on cruises with Ambari, there are often a lot of engineers and people who have a lot of technical skills. And they will see my sponge, animals that I'm studying as pump systems. And they'll say, well have you thought about how a pump works? And how would this relate to how pumps work? And I go, oh we should talk about how pumps work. And, you know, it's interesting to have those conversations. And I think those cross discipline conversations are what make those new connections. Like, you know, why would we ever think to look at carbon and nitrogen cycling unless we were thinking about some ocean chemistry? So yeah, I think that's part of it.

And the other thing is just, ship expeditions and big field expeditions take a lot of people to pull off. You need a lot of moving parts. And I think it's probably a lot like spaceflight, where you don't want to mess up because you don't get many chances to do it. So you want your cruises to be very much correctly done and worth it. So everyone chips in and works together to help everyone get done what they need to get done. And therefore everybody's involved. And I've been, I think really fortunate. I think that the community that I work in, in marine science, or at least the people I've worked with in it, have always been more on the side of collaborative than competitive in any way. So it's always been looked at as a boon to work together, if possible.

Vincent del Casino: Well I imagine that's what you get with all these other San Jose faculty right? At Moss Landing you have the School of Marine Science. And, but there's quite a diversity because you have ocean chemists and yourself as an invertebrate zoologist and other sorts of folks. All the San Jose faculty, right, working together collaboratively along with all those other scientists who are showing up and research specialists and so forth. So that part must be really interesting for you to be located there, right?

Amanda Kahn: Definitely. That was one of the biggest draws I think, is to think that I'd be in a location where I could easily walk down the hall and ask a geologist a question that, you know -- and it wouldn't just, you know, it will be a geological oceanographer, someone who kind of knows the system that we're working in. And it's been really fun over -- I've only been here a year and a bit so far, but it's been so fun in this past year to talk about projects that we're wanting to start up. And they're also cross disciplinary. So it's been really fun in that way. And now I'm branching out with someone in the college of -- well Department of Computer Science as well. So jumping in with working with more folks at San Jose State on the main campus as well.

Vincent del Casino: Yeah.

Amanda Kahn: So yeah, it's just great.

Vincent del Casino: Well, Amanda, I want to thank you so much. I mean I really enjoyed this conversation. I knew I would, because when I first met you, I love the passion, enthusiasm. But also this just seems to me as like really critical and interesting and important work that speaks to so many other issues that we need to think about and tackle. So thanks again for really taking the time for coming and spending some opportunity to chat with me about sponges and much more.

Amanda Kahn: And more. Thank you for inviting me. This has been really fun. And I'm going to put you on the spot in the future to talk about some geography too.

Vincent del Casino: All right, fair enough.

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