Episode 5: The Secret Life of Deep Sea Symbiosis

How deep sea worms eat without a mouth is just one of the astonishing discoveries in this episode with microbial symbiosis expert Dr. Shana Goffredi. We dive into the strange and beautiful world of methane seeps and hydrothermal vents, where animals form life-saving partnerships with chemosynthesizing bacteria. From feather duster worms powered by natural gas to mixotrophic anemones thriving in volcanic vents, learn how cooperation fuels entire deep sea ecosystems — and helps prevent methane from reaching our atmosphere. These microscopic alliances are transforming how we understand evolution, resilience, and oceanic carbon cycling.

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Episode Guest: Dr. Shana Goffredi

Learn more about Dr. Goffredi at Occidental College

Visit the Symbioxys Lab’s website

Follow the lab on Instagram

Find more of Dr. Goffredi’s work on Google Scholar

Read the discussed article on Feather Dusters

Read the discussed article on Deep Sea Anenome

Here’s a third on ‘Marine Vampires

Find more of Dr. Goffredi’s science outreach on Science Friday

Episode Transcript  and more information on the Pine Forest Media website

Follow Pine Forest Media on Instagram @pineforestmedia

Hosted, produced, and edited by Clark Marchese 

Cover art by Jomiro Eming

Theme music by Nela Ruiz

Listen to South Pole on Spotify or Apple Podcasts

Listen to Plastic Podcast on Spotify or Apple Podcasts

Listen to Something in the Water on Spotify or Apple Podcasts

Transcript:

Clark Marchese (00:11.982)

Hello there. Thank you so much for joining us here on Oceanography, the podcast that dives deep into the science of our oceans, the latest in marine research and the scientists working hard to better understand and protect our blue planet. Today, we are going to be working together to learn all about deep sea symbiosis.

Clark Marchese (00:54.816)

Alright, Symbiosis. Let's crack out a dictionary, shall we? This word can be defined as an interaction between two different organisms living in close physical association typically to the advantage of both, like you and me. We have several examples of this in nature. You can think of bees and flowers, right? Bees will pollinate flowers, allowing them to reproduce, while also collecting nectar for themselves. More information about this process can be found in the Bee Movie. We can also think of ourselves and our microbiome. Beneficial bacteria in our gut helps us digest food and produce vitamins while we provide them with a home and with nutrients. Bringing it all back to the ocean, we can think of Finding Nemo. Dory helps Marlin find his son and Marlin helps Dory find her family. no, not actually. I mean, that is what happens in the movie. Sorry if I just spoiled Finding Nemo for you, but the real example is between the clownfish and the anemone-menemene-mese. Clownfish live in the stinging tentacles of sea anemones which protects them from predators while the anemone benefits from the clownfish's excrement and also defense against certain fish. Today we are going to learn about the fascinating symbiotic relationships at the bottom of the ocean, specifically within methane seep ecosystems and nearby chemical emitting volcanoes between deep sea critters and chemosynthesizing bacteria. There are quite a lot of words in there, we will come to understand them all in a moment with the help of our guest joining us today, who is named Dr. Shauna Goffredi. Dr. Goffredi is a leading expert in microbial symbiosis and the current chair of the biology department at Occidental College. Dr. Goffredi's research uncovers the intricate cooperative relationship between bacteria and invertebrates, partnerships that have shaped biodiversity in astonishing ways, from the evolution of new animal organs to the development of entire ecosystems fueled by microbial metabolism. Her work, supported by the National Science Foundation and published in journals like Frontiers in Microbiology and Environmental Microbiology, reveals how these microscopic alliances extend the influence of deep sea methane seeps and hydrothermal vents, creating pockets of life where we least expect them. In today's episode, we will learn about anemones, mixotrophy, featherdusters, how methane sometimes is food, how some things can eat without a mouth,

Clark Marchese (03:12.364)

and the importance of cooperation in the ocean environment. Just before we get started, if you enjoy oceanography and you want to support science communication, I would invite you to consider joining us on Patreon. For as little as $3 a month, you can help us keep this show going and others like it, and a portion of the proceeds we collect from Patreon will go to support other science communication and research projects that our contributors will get to help us choose. The link is in the episode description, and while you're there, a one top five star rating will also really help us reach more people and If you want to write something nice, we'd also love to hear what you think about the show so far. Another thing you can do to support our science communication is simply to share it. Seriously, send it to someone you know, send it to someone you don't know. Send it to your crush and then come back and tell me if it worked. Okay, I think it's about time we just start the episode. Let's get into it. Marine Simbiosis coming to you now.

Clark Marchese (04:15.2)

Okay, red flashing light is on. Well, Dr. Gaffready, why don't you start by introducing yourself and maybe tell us a little bit about why you decided to build a career in ocean science?

Dr Shana Goffredi

Yeah, that's a great question. So I grew up in Colorado, so nowhere near an ocean, but I was sure that I was interested in biology. So I would play around in the backyard with insects and bugs and every now and then my family would take us on a vacation to the ocean. And I was really fascinated by it. But I actually went to college thinking I was going to be in medical school. I was going to be a doctor. And I had really formative.

Dr Shana Goffredi (04:59.03)

I had very formative professors that were also marine scientists, I realized that I loved it and that I could make a career of it. 

Clark Marchese

Shout out to teachers honestly. I definitely also had my share of formative teachers that I wouldn't be doing what I'm doing today without and I would venture to guess that a lot of your students would probably describe you that way as well. Because you are also in fact a teacher at Occidental College and the director of a research lab there. Can you tell us a little bit about the work that you're doing at that lab?

Dr Shana Goffredi

Yes. So Occidental College is primarily an undergraduate serving institution. And so we don't have masters or PhDs or post-docs. And so all of the research that we do at OXIE is with undergraduates. And I actually quite love it. I was a career scientist for a long time, and then I found myself at Occidental and they opened a position for a microbiologist and I applied. And I've been conducting research and teaching there ever since. And it's a really great philosophy. was something that really resonated with me because I also went to a small liberal arts college in San Diego when I first started my career. And it is based on these close relationships between faculty and students where you're actually doing real science and having hypotheses about natural phenomena and then exploring them together. And so we weave this into their education, but it also benefits our research programs.

Clark Marchese

Okay, amazing. I'm really glad to hear that there's so many opportunities at the University for undergraduates to do that kind of hands-on research. And it's called the Symbioxis Lab? S-I-M-B-I-O-X-I-S? Is it sort of symbiosis and occidental mixed together? Can you tell us a little bit about that?

Dr Shana Goffredi (06:43.296)

Yeah, yeah, we, we, do pronounce it symbiosis, but perhaps pronouncing the X in the old fashioned way. Yeah. So just oxy is in the title somehow.

Clark Marchese

Okay, got it. Symbiosis, which is our main topic for today. Let's start by defining it, and then maybe you can tell us what sorts of research questions the Symbiosis Lab is asking about it.

Dr Shana Goffredi

Yeah, so when I started out, started studying animal physiology and I was studying these very interesting animals on the seafloor, two miles deep, that actually do something quite interesting, which is to team up with bacteria for their nutrition. rather than relying on sunlight. They are relying on bacteria. And so I realized that there were such a thing as symbiosis. And I would define that as non-transient, of more permanent interaction between two different organisms that in this case benefits both partners. And so the original definition of symbiosis and something that I do still believe in and most of us do is that the range of interactions between different species, as you put it, could span the range of beneficial to neutral to detrimental. So the original coining of the term in the 1800s was very broad like that. But my particular research program and a lot of people who do study symbiosis think of it as mutually beneficial for both partners. So that is probably the largest field of symbiosis is to study those mutually beneficial interactions. But we do accept that there are other kinds of interactions between these two organisms.

Clark Marchese (08:21.006)

Okay good, everyone's on the same page. Now, what about the focus of your lab?

Dr Shana Goffredi

So my research focus has been marine invertebrates, so animals without backbones, so marine invertebrates, snails, clams, worms, you name it, sea spiders, and their beneficial relationships with bacteria. And the relationships give these animals a superpower, like those that I first started studying when I was in graduate school, which is that they have internal sources of nutrition, so they no longer need to feed themselves. So when they find themselves in an area with very low food availability, they just rely on these internal bacteria or sometimes external in the case of the Yeti crab. So there are lots of different strategies for teaming up with bacterial partners. And I think one of the two most profound things actually about symbiosis is that one, not all interactions with bacteria are harmful. Of course, we should be afraid of certain microbes, but there are so few of them that cause harm and actually so many more of them that are hugely important for our health and wellbeing of our human bodies, but also of the planet. So I think it's important to realize that. And also, I think the other profound thing is that cooperation can actually get you further than competition. And so from a sociology perspective, I also like to think about ways in which two organisms will make compromises and sort of negotiate with each other in order to get further and be successful in habitats that are really under under-exploited or really hard to actually make a living or thrive in these habitats. And yet they are because they've joined forces. So I really love to think about symbiosis from those perspectives.

Clark Marchese (09:56.204)

Wow, okay, a lot to unpack. First, I love the notion that cooperation gets you further than competition. There is room for everyone at the top. But I think maybe the most fascinating thing I've heard so far was, did you say that you found that there's a bacteria inside of critters that make it so they no longer need a food source?

Dr Shana Goffredi

Correct. Not only do they not need a food source, but these animals no longer have a mouth or a digestive system or any way to feed themselves.

Clark Marchese

Okay, where are we gonna begin here? So the bacteria provide the food for the organism? Yes. Okay, how?

Dr Shana Goffredi

Okay, let's unpack that. So let's just think about something that people are familiar with, coral reefs. These animals are living in areas of the ocean that are actually really low in food availability. So even though those animals can still feed themselves, there's very little to eat in the tropical oceans. And so instead they team up with photosynthetic microbes, algae, microalgae, that live inside of their tissues and photosynthesize like a plant. And in exchange for living inside of this habitat, which is essentially an animal, animal tissues, they will provide sugars. So photosynthesis results in the production of carbohydrates like sugars. And those sugars are delivered to the animal either a couple of different ways. They can be sort of transported, transferred from the symbiont to the host, or the host can actually just digest their symbionts whole.

Dr Shana Goffredi (11:23.04)

And by doing that, they actually cull the population a little bit so they don't get overgrown. So this is a way to keep check on the internal symbiont populations. The same thing is happening on the seafloor. These animals, some don't feed at all anymore. And instead of relying on sunlight as an energy source to make those sugars, their symbionts, their bacteria, rely on chemical sources of energy that are coming from underwater volcanoes in the bottom of the ocean. And they use that energy to fuel the production of organic carbon from gaseous CO2. And in that way, because this organic carbon is made, they have an internal source of nutrients the same way that the coral reefs do. So either the nutrients are transferred through the membranes of the bacteria to the animal, or again, the animals can just digest them intracellularly.

Clark Marchese

Okay, this is making sense. And in a similar way, in the deep sea, we're sort of explaining a process that I think could be called chemosynthesis. Is that correct?

Dr Shana Goffredi

Correct. Yes.

Clark Marchese

Okay, so if I got this right, in a tropical coral reef, certain organisms get their food, their energy, their sugars from photosynthesizing organisms, which is maybe a concept that people will have heard of. I'm having flashbacks of 10th grade biology, and this is sort of a fascinating process to understand the mechanics of, but in this case, the original energy source is the sun, and this happens on land too, right? Broccoli takes energy from the sun, and we take our energy from broccolis, but what you're telling me is that in the deep sea, where there is little

Clark Marchese (12:55.916)

or even no sunlight, we see the same kind of relationship, but instead of photosynthesizers taking energy from the sun, a chemosynthesizing bacteria takes energy from a deep sea chemical emission, and that energy gets transferred to the deep sea equivalent of tropical coral reefs.

Dr Shana Goffredi

So the chemical compound is very high energy. Think about like methane, natural gas that you can burn, hydrogen that you can use to power cars, hydrogen sulfide. These are all extremely high energy molecules. And if you can harness the energy from those like microbes can, bacteria can, then you can use that energy. It's just as powerful as the sun as an energy source. But of course that's not available two miles deep in the ocean. So they use something else. And if you can essentially oxidize it, that compound, and harness that energy, you can fuel lots of processes, including the production of organic carbon. And that is called plenosynthesis, yes.

Clark Marchese

Okay, okay. And then maybe can you give us a little bit of context about where these chemicals come from?

Dr Shana Goffredi

Sure. So the main source of these chemicals is the underwater volcanic activity. So where the earth's crust is the plates that are covering the earth are splitting apart. Those are areas where a lot of high temperature fluids are emerging into the ocean and they're carrying with them a lot of those chemical compounds. So there's metals, there's high hydrogen sulfide, and there's hydrogen itself.

Dr Shana Goffredi (14:28.098)

So those are along the mid-ocean spreading centers. There's a lot of underwater volcanism and these animals are all positioning themselves in those areas because there are free-living bacteria that are also chemosynthetic that are taking advantage of those chemicals. And then in some cases there is a relationship that forms. And of course this is formed over millions of years, but they are now intertwined as a symbiotic organism.

Clark Marchese

Okay, so option one, underwater volcanoes.

Dr Shana Goffredi

The other way that these compounds can exist is because of natural microbial activity in deep sea sediments. So there are some other habitats that are called methane seeps. And so this is where a lot of material is buried, organic material is buried in the subsurface. And again, there's also some geology happening there where there's like, say, one plate is subducting under the other at like continental margins. So off of California, for example, this is a very tectonically active area. And this exposes these areas of microbial activity and allows for the methane and the hydrogen sulfide gas to actually seep out of the seafloor. So because of the tectonics, they kind of are made available, these chemicals. So normally they would be buried, but because of the geological activity, they are expressed on the seafloor. And so animals also kind of crowd around those locations in order to access these high-energy chemicals.

Clark Marchese (15:54.99)

Option two, methane seeps. Fascinating. Now, you said that these chemical sources are sources of food or energy, and then I heard you say that there are a lot of animals that crowd around them. So, do we see that this is causing the development of a biodiversity hotspot perhaps, or even entire ecosystems of their own?

Dr Shana Goffredi

for sure. So there are absolutely unique ecosystems at hydrothermal vents, which are these underwater volcanic locations, and at methane seeps. They are extremely diverse and those animals are found nowhere else on earth. And so they are unique to these areas and they travel of course, and they have certain geographical ranges. So they can't travel, say, from the Pacific to the Atlantic. We find actually really different communities in the Pacific Ocean from the Atlantic Ocean. Those are conjoined by the Indian Ocean. And so there are some areas of overlap. But it's very, very fascinating to actually work with ecologists in these areas because there are new species discovered all the time on the seafloor. And a lot of them are surprising us in the ways in which they are teaming up with bacteria let alone just surviving in those really unbelievable conditions, because you have to also consider that it is, there's a very high pressure. So these animals are really exquisitely adapted to the deep sea. And they also have to contend with high temperatures near these vents or toxic chemical compounds or toxic metals. And so they are really well adapted to living in these locations. And as they're thriving based on these relationships with bacteria.

Clark Marchese

Okay, I think that everything we've covered so far is a really great foundation for us to have as context as we start to discuss some of your specific and recent research. I want to learn a little bit more about some papers that you've published about feather dusters, which are sort of a type of marine worm. What can you tell me about feather dusters as it applies to everything we've talked about so far?

Dr Shana Goffredi (17:52.632)

So this study that you're speaking about, this all occurred off of the West Coast of Costa Rica. And so we were not the first to have gone to these locations. So these are these methane seeps that I spoke about and there are two or three really prominent methane seep areas off of Costa Rica that had been explored in the past. And we were traveling there to actually understand the sphere of influence of methane on the planet. So we're very interested in how and where animals can take advantage of methane gas, because it is coming from the sea floor and no animals can take advantage of methane on their own, but they can use bacteria as intermediates or partners in trying to harness that carbon from methane. And so we were there looking at the influence of methane and we discovered these feather duster tube worms that were definitely, they looked unusual to us. And so we always take experts with us, of course, and Greg Rouse, who's a good friend of mine and a professor at Scripps Institute of Oceanography. We were looking at these tube worms and we were thinking that they didn't, these feather dusters, that they didn't really look the same as regular feather dusters. the reason is because they had these sort of clumpy tentacles on their head rather than these sort of filamentous tentacles. And so it looked like maybe there was like something on their tentacles. And sure enough, when we got them on board and we did microscopy, we realized that their crown tentacles of their head were actually covered in bacteria. And we realized that these bacteria were actually all methane oxidizing bacteria and that these worms were actually internalizing these bacteria as the source of nutrition. And so these were methane powered feather duster tube worms. And that was a completely novel discovery. And people in the past have seen these very interesting, these two worms in some ways will make these calcium carbonate tubes that can show up in the fossil record. And it had always been this longstanding mystery from people who study paleo seeps that they see these big beds of these.

Dr Shana Goffredi (19:56.13)

feather duster tubeworm tubes, but there was no living example of a feather duster that actually was chemosynthetic or took advantage of chemicals from a methane seep. And so this was always a, you know, a big mystery. And we finally found an example of a feather duster tubeworm taking advantage of a high energy chemical compound from the seafloor. And it turns out to, we can tell from the tubes, the fossil tubes, that they're actually in the same genus. And so it makes us believe that all of those old fossil deposits, some are now pushed up onto land. All of those fossil deposits of these feather duster tube worms were probably evidence of ancient seeps on the ancient oceans. And so it was a pretty fun study because feather dusters are well known to people. You can see them scuba diving. You know, they're in the aquarium trade. You see them all the time, but these were very different feather duster tube worms living in the bottom of the ocean, two miles deep. off of Costa Rica and they were essentially using natural gas as a source of nutrition rather than feeding themselves like a typical feather duster tumor might.

Clark Marchese

So then in the case of feather dusters, what exactly is the pathway where the energy from the bacteria enters the feather dusters?

Dr Shana Goffredi

Yeah, so they have to be consumed. think of a bacterium is using methane and incorporating that into their little bacterial cell. And then the worm actually consumes them, but they don't consume them with a mouth. They actually pull them through their skin, essentially. just sort of, yeah, it's kind of science fiction, actually. These are like alien life forms right here on our planet.

Clark Marchese (21:29.518)

except it's not because it's literally science nonfiction. That is incredible. But this is making me wonder how on earth are we able to find that out? Like how do you go about finding a feather duster two miles below the surface of the ocean and discover that it's eating without its mouth?

Dr Shana Goffredi

Yeah, that's a good question. So usually it is accidental, but I would say serendipitous. So of course you have to be looking and you have to be open to the possibility of finding something novel. And usually we are employing either robotic submersibles or human occupied submersibles to take us to the bottom of the ocean. And we are targeting specific locations on the sea floor where we know that these high energy compounds will be and where maybe previous studies have dragged a camera sled so we can, we've seen that there's evidence of ecosystems there, but nobody's really looked very careful. 

Clark Marchese

It's interesting for me and maybe some listeners to grasp that that is like somebody's Tuesday afternoon. But another thing I want to ask you, and forgive me, I'm sort of bouncing all over the place with my curiosities. One thing you said is that scientists are always interested in methane and where we're finding it in the ocean, how it relates to organisms and the ecosystems, et cetera. I just recorded another episode about the biological carbon pump. And so listeners are going to learn really soon about sort of how important carbon is as a molecule in the ocean.

But methane and carbon are both really abundant in the ocean and also increasingly in the atmosphere. And I can't wait to share it, but in that interview I learned all about sort of the link between the carbon pump and the ocean and climate change. If listeners are curious about that, which you really should be, you'll have to just wait a couple of weeks. But are any of these discoveries that you've mentioned giving us any information about how methane functions in larger ocean or earth systems?

Dr Shana Goffredi (23:15.264)

I'd say that it is probably a missing link in the carbon cycling in the deep sea because we don't think of these animals. We've also discovered a sponge that uses methane and sea spiders that use methane. So this was the whole point of the National Science Foundation proposal was to look at the sphere of influence of methane. And this is with collaborators from UCLA, Caltech, Scripps, and Occidental. We are very interested in understanding where methane goes in the ocean and which kinds of ecosystems it can support. And I do think that not only does it help us understand the flux of carbon through ecosystems and animals, because these animals are cultivating big bio-masses of these microbes that would otherwise maybe not achieve those densities in their tissues, on their bodies, and especially the sponges as well, and the sea spiders. So all of them combined, they are supporting a big population of these methane oxidizers. And that actually does us a service. This is an ecosystem service provided by these animals and their bacteria because the methane then doesn't reach our atmosphere. It actually gets consumed in the deep sea. And this has been well known by other scientists that study free living bacteria and archaea, the other kind of microbe that lives down there. So we already knew that they were acting like a filter for methane, but we didn't know. We don't really have a good idea of the role of animals in this process. I will also say that this expanded our notion of a methane seep. So we want to be aware and understand our planet a lot better. We actually know very little about. our planet in terms of what's on the seafloor. And it is really important for us to have a good understanding of these ecosystems. And we had never really considered feather duster tube worms to be part of these methane seeps. We always just consider them to be sort of dispersed fauna down there on the seafloor that are, you you see them every now and then, but we saw huge populations of them thriving. And so it gives us a better understanding of the ecosystems on the seafloor.

Clark Marchese (25:17.006)

Okay, that is very important and not to give it away, but when we talk about carbon, we'll learn just how much it influences climate and there isn't as much methane as there is carbon in the atmosphere, but methane is a lot stronger in terms of its impact on rising temperatures. Older estimates put methane at about 25 times more potent than carbon as a greenhouse gas, but some recent estimates place it as high as 86 times in the short term. So this type of research really matters. But speaking about how much we don't know about the ocean and how much of a role this may play in larger systems. I'm curious if we have any understanding of how common this effect is. I've heard you mention that we're seeing it in multiple different species, but I guess how broad of a phenomenon is this or do we suspect it might be?

Dr Shana Goffredi

Yeah, I actually think it's much more broad than we realize. And the reason is that it can be what we would consider to be facultative for these animals. So that's a term that means that these animals in some ways can still take care of themselves. So I gave you the extreme example of an animal that no longer has a mouth or digestive system. But for most of these animals, this is just a nutritional boost. And so when you have an animal that can feed itself, but then also live in these unique habitats and take advantage of symbionts in a way that is, you know, take it or leave it. They probably would prefer to have their symbionts, you know, especially when there's a high energy chemical around. These are much harder to discover because you just have to look a lot harder. When you see an animal that is obviously different, doesn't have a mouth, doesn't have a gut, is sitting in billowing volcanic fluids on the seafloor, you automatically know that that that animal is going to be quite different and you probably can be assured that that animal has a symbiont of some kind.

Clark Marchese (27:06.444)

Right. So the feather dusters are just one example, and it may and does look different in different relationships, which harkens back to what you said earlier about how scientists need to keep an eye open to discovering unexpected things. There's another example I found in your research that I think is similar, but also a bit different. And this is the case of anemones. According to your study in 2021, I'll link it in the show notes, the chemo synthesizing bacteria are found inside the tissues of anemone. Is this different? than what we saw with the feather dusters?

Dr Shana Goffredi

It's different actually. yes, so these anemones, this was an example of getting to the sea floor, thinking that you're studying something different, and then you are hit in the face with this really crazy phenomenon, which is these anemones that were sitting in this high temperature fluid, sort of billowing out of these underwater volcanoes, side by side with these giant two berms that we already knew were relying on a high energy hydrogen sulfide gas. And so these anemones were behaving really weird, even though they didn't look any different from typical anemones on the seafloor, they were behaving strange. And so we of course sampled one. And as you noted, we actually discovered that there were bacterial symbionts inside of cells, inside of their tissues. And that is called an endosymbiotic arrangement. So inside of their tissues. And the most intimate an animal can get was a bacterial symbiont is to let them not only inside of their tissues, but inside of their cell membranes. And that's actually, that's the case of the anemone. But what was so fascinating about this anemone is that it was the first ever animal in its phylum to actually be discovered that was relying on chemosynthesis. And of course there are others, and now we actually know that there are others, but it was the first of its kind and it was always expected. There was seven other animal phyla.

Dr Shana Goffredi (29:00.088)

then this is the largest grouping of animals that you can get besides the kingdom, Anemelia. There were seven other known phyla or groupings of animals that associated with sulfide-oxidizing bacteria, but the group that anemones belonged to was not one of them. And so we always knew that they probably existed, but it was super exciting to actually find an animal that, a species of anemone that did this. And the other thing that's interesting about them is that they keep their symbionts in a different tissue than all other known cor- like those in coral reefs that have photosynthetic symbionts. They keep them in a totally different tissue than these deep sea anemones. So we actually were stumped for a while about the location of their bacteria, but we eventually found them in a totally different tissue than we expected. And so it just goes to show you that you can't have any sort of preconceived ideas about these animals and their symbionts, because they surprise us all of the time.

Clark Marchese

Okay, I've got a couple of questions here. I think I know the answer to this one, but my brain was just thinking if chemosynthesis is happening inside the cell of the anemone itself, maybe we could be tempted to say the anemone was chemosynthesizing, but that's probably not true because the bacteria that's carrying out the process is in fact a separate species. So that's making me wonder if bacteria is the only sort of species group we know that carries out chemosynthesis. Obviously, bacteria is like a really large category, but could you imagine an anemone or something similar, eventually becoming a chemo synthesizer on its own.

Dr Shana Goffredi

I cannot imagine that. is a metabolism unique to microbes. I will say with regard to photosynthesis, but most of those photosynthesizers are other eukaryotes, like things with a nucleus and an organelle, and those are like algae and protozoans. Some animals can steal the chloroplasts from their symbionts and become solar powered on their own. So your question is true for photosynthesizers?

Dr Shana Goffredi (30:58.36)

but not for, not for chemo synthesizers. And the reason is really hydrogen sulfide gas in particular is extremely toxic to animals. And so I can't imagine an animal intentionally interacting with hydrogen sulfide unless they were absolutely certain of having a microbe nearby that could oxidize that, that harmful sulfide.

Clark Marchese

Are we as interested in hydrogen sulfide as we would be in methane as far as its sort of larger position in the ecosystem?

Dr Shana Goffredi

Yeah. I mean, I think we're interested in it from the perspective of sulfur cycling in the ocean for sure. I mean, it's a big player. It's the most reduced form of sulfide in the ocean, but it does play a big role in giant fish kills and things like that. When you have like an algal bloom and then all of that algae starts to decompose, there is a huge production of hydrogen sulfide that can kill animals. So when you get big areas of anoxia, can sometimes be because of hydrogen sulfide gas production. So that's just a, you know, the rotten egg smell that you smell when things are decomposing. That's the same idea. So this is how it gets produced. These seeps is the decomposition by bacteria and the sediments, but then it's a high energy compound that people, animals and bacteria can use. So I think it's, it's less important from a human perspective, I'd say, if that's what you're going for, but it's certainly important to understand from a sulfur cycling.

I'd say the other important compound that we've learned about probably in the last 10 years that is also involved in symbiosis in the deep sea is hydrogen. So we know that some of these animals, their bacterial symbionts can harness the energy in hydrogen. So think about hydrogen powered cars, think about the Hindenburg, think about how flammable and energetic hydrogen is that is also coming from the sea floor. And again, that can be oxidized or used by

Dr Shana Goffredi (32:52.93)

the animals there. So I think we're interested in it, but methane is probably the most consequential because if methane ended up in our atmosphere, we would, if all of that methane that they're currently consuming ended up in our atmosphere, we would have even bigger problems than we already have.

Clark Marchese

Okay, we're swimming through a lot of concepts really quickly on this episode, but I also read that these anemones you found are one of the only anemones using both chemosynthesis and predation, which I learned there's a word for that, and it means we can call them mixotrophic. So can you tell us what mixotrophy is and why this finding is significant?

Dr Shana Goffredi

Yeah. So that gets back to my point about these facultative arrangements. So when the animal has a mixotrophic nutritional strategy, we mean that they can feed themselves by relying on predation or filter feeding. So they are consuming organic material in the typical animal way, which is like how you and I eat. And the other strategy they use is to farm or consume bacteria in not from their mouths, but in other interesting, weird ways that they culture, essentially. And so that's the mixotrophy. And we call that facultative because they can live without their symbionts, but they do better with them. And I think that that is a really smart strategy for animals. Because what we saw, we actually saw this with regard to the anemones that we spoke about in the Gulf of California. The plumbing changes a lot with these underwater volcanoes. if the water, if there's like an occlusion or a clog in the plumbing near these animals, which can't move on their own, so they're stuck in one place. If that plumbing changes and they're no longer able to get this high energy compound from those fluids, because the fluid redirected and went a different direction, then what we noticed is that the tube worms, for example, that are

Dr Shana Goffredi (34:50.078)

obligately, they absolutely must have their symbionts. They are tied to that hydrogen sulfide no matter what. No ability to feed themselves. They all died. So they perished. And we knew this because we went back two years later and this had happened. There had been a big change in the ecosystem. So the two worms had died, but the anemones, which had this mixotrophic lifestyle, had persisted because they had the ability to feed themselves in the event that their bacteria could not pull their weight and use the hydrogen sulfide, because it was missing from the environment, and they were able to survive. They didn't look nearly as lush and big, but they had survived. And so it gave them an advantage for sure. And that was a little experiment that Mother Nature did for us, which was extremely fascinating.

Clark Marchese

Okay, that is really fascinating, and it's a level of resilience that may come in useful as environments continue to change at increasing speeds. Could you say that symbiosis or quote, working together may make species more resilient to things like climate change or perhaps more vulnerable if they come to depend too heavily on one another?

Dr Shana Goffredi

I'd actually say that in this case, they'd be more flexible. Although I say that, but let's just talk about coral reefs. So of course they have photosynthetic symbionts and know, coral bleaching is a disruption of the symbiosis. So the reason why they have lost their color and they've bleached is that they have expelled their symbionts because they're stressed. So either their symbiont was stressed. And they weren't performing photosynthesis. So they got booted out of the tissues or the coral was stressed. And they said, I can't take care of both of us. You're out of here. But of course then that caused the demise of both players. So coral bleaching is one of those examples of not being very resilient to climate change, however, and changing environments. But there are some corals that are actually what we would call promiscuous and a little more flexible with their symbiotic partners. And so.

Dr Shana Goffredi (36:44.216)

there have been studies from folks in Australia and others that they know that certain corals can actually swap symbionts. So they will expel a certain species of symbiont and they will take up like say a more thermally adapted species. so those that are actually less specific, I think that they will be the ones that are more flexible and can endure changing environmental conditions.

Clark Marchese

Well, on that spirit, what are some of the burning questions you have as a researcher or that you can identify within your field that relate to what we've talked about today that you would really like to have answered?

Dr Shana Goffredi

Well, I consider myself an explorer more than anything, and I just really love to get out there and explore the ocean. There are so many fascinating examples of animals defying our conventional wisdom about them. And so I just, I really love this planet and this ocean and it's, it's so unique when you really think about it. And so I think ocean discovery, I wish there was more opportunities to just go and look. So many funding agencies want you to say exactly what you'll find and exactly the plan. And I think there's a lot to be said for just going and looking. And of course, with a team of experts and in a way that you can take advantage of discoveries, but I guess exploring our world and seeing it with different eyes. So a scientist can have confirmation bias just as much as another person. And I think we have to be really open to the possibility that some things are are working on this planet in ways that we had not anticipated.

Clark Marchese (38:22.284)

Well, we have covered a lot of ground today. And as we come to the end of our time together, I want to ask you, is there anything we didn't talk about that you think is important to touch on? This is sort of an open mic moment before we go.

Dr Shana Goffredi

huh. Well, I'd say that I'm, I'm extremely lucky to have the job that I do. I love going to work every single day. It's amazing being a professor and getting to interact with young people. So they, they have so many great ideas and they are full of energy. And so it's really this beautiful balance of being able to do the thing I'm passionate about. in the ocean and researching novel life forms on the planet, but also educating and being involved in research. So I really love that. I would also say that I'm, I'm extremely happy that people are realizing how important their own symbionts are in the human body. So we've come a long way from thinking that, you know, we are autonomous individuals and that we understand now the development of our nervous system and our immune system. And of course our digestion is all because we have beneficial bacteria in and on our bodies. And that's just, man, in the time of my career, that transformation has happened and it's a pretty exciting time. So I just think there's just this revolution in the understanding of non-scientists about how important and beneficial bacteria can be. So I think that also propels me every day.

Clark Marchese

All right, well, this is the part where I say thank you so much for taking the time to come on the show today. Thank you for teaching us about deep sea worms and chemosynthesis and symbiosis and endosymbiosis and mixotrophy and everything else we learned about today. And also for your really important research in this space.

Dr Shana Goffredi (40:00.334)

Thanks so much, Thark.

Clark Marchese (40:09.282)

You have been listening to Oceanography. Just a reminder to anyone who's interested in helping us reach more people, share scientific research like this, and continue making our shows, you can find a link to join us on Patreon in the episode description. That or a one tap five star rating and a written review wherever you're listening to this are the easiest and most effective ways to help us out. You can do that in the episode description where you will also find more information about the podcast and this week's guest. This is a Pine Forest Media production. We are a podcast network with multiple shows that unpack different environmental issues, focusing on the intersection of science and society. You can find more information about us on our website at pineforestpods.com or follow us on social media at pineforestmedia. Cover art for this show was done by Jomiro Emming and the music you're listening to was done by Nila Ruiz. The show is hosted and edited by me, Clark Marchese. I want to thank you all so much for listening and making it to the end of the episode. And I will love to see you right back here next week.