NaturallyScott
At least once a week, I’ll bring you the very best of America’s spectacular world of nature — from birds to mammals, to reptiles and amphibians. From soaring mountains to endless plains, from rugged coastlines to rivers and streams.
Each episode will feature an expert guest — a ranger, a researcher, a birder, or an adventurer — someone who has seen what we want to see and been where we want to go.
NaturallyScott
E68 Dr. Virginia Edgcomb – Hydrothermal Vents, Ocean Microbes & Life in Earth’s Most Extreme Places 🌋🌊
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What if the most important life in the ocean is almost completely invisible?
In this episode of Naturally Scott, Scott Harris sits down with marine microbiologist Dr. Ginny Edgcomb of the Woods Hole Oceanographic Institution for a fascinating journey into the hidden world beneath the waves.
From hydrothermal vents and hypersaline lakes at the bottom of the Mediterranean to deep-sea drilling expeditions in the Indian Ocean, Ginny studies microscopic organisms that thrive where most life simply cannot. Along the way, she explains how these remarkable microbes recycle nutrients, fuel entire ocean ecosystems, and may even help scientists search for life beyond Earth.
The conversation explores:
🔬 Why microbes are the foundation of nearly every marine food web
🌋 Hydrothermal vents and the extraordinary life they support
🧂 Mysterious hypersaline “lakes” hidden on the Mediterranean seafloor
🌍 What Earth’s most extreme environments can teach us about alien life
🚢 Life aboard research vessels—from flying fish and whales to pirate drills
🌊 How climate change is reshaping the world’s oceans
Equal parts adventure, exploration, and science, this episode reveals an unseen world that quietly supports nearly every living thing in the sea.
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Hello, I'm Scott Harris, the host of Naturally Scott. Welcome to the podcast. We've got another in a series of interesting ones today. And um I am really excited about this. This is Ginny Edgecomb. Am I pronouncing the last name correctly? You are. Oh, fantastic. And you are a senior scientist at Woodhole, Woodhole Oceanographic Institution. Is that correct as well?
SPEAKER_02Yes, Woods Hole Oceanographic. And um I just recently transitioned to Emeritus Research Scientist to be accurate. So a big change for me, but I'm still actively involved in research there.
SPEAKER_01Well, fantastic. And I'm looking forward to learning about some of that. Now, this show is going to be different. We've been focusing recently on megafauna. Um I'm writing a book about megafauna and you know the elephants and the bison and whales and bears and all of the things that people are kind of naturally attracted to, right? Um and so this is a whole different direction uh that you're taking us today. And I'm excited about this and about you sharing this with the audience. So you are, if I'm correct, a marine microbiologist?
SPEAKER_02Yes, I am. So I study the things that you can't see except through a microscope.
SPEAKER_01How does one get there? I know I'm I've gonna ask you about three or four stories, and that's what I told us was, but I gotta know how you get there.
SPEAKER_02You mean in terms of my career or yeah, when do you wake up and say this would be more fun than whales? Well, I think everybody has to find their niche. And uh when I was starting grad school, I lived in Delaware, which has abundant salt marshes, and I was interested in birding and in the ecology of salt marshes, and I decided I wanted to study salt marshes, what made them tick. And I found that microorganisms were really the foundation of that whole food web. And it turns out they're the foundation of all marine food webs. So the whales, the the fish, the zooplankton that people can see and read about, you know, they all depend on microorganisms. And so because they are the base of all the cycling of all the nutrients in the ocean, so they're incredibly important. And I felt like this was a niche that I could really dig into uh because there's a lot of open questions.
SPEAKER_01Um, so um so what exactly does a marine microbiologist do? If you you have an interest in salt marshes, for most of us that means we you know walk through them and we look for our favorite birds and all of those different things, but you see a salt marsh differently than most of us.
SPEAKER_02I do. I I love that sulfur smell that people tend to dislike because it's the sign of an active process called sulfate reduction, which is uh carried out by bacteria that produce that hydrogen sulfide smell that people know. And uh they are the ones that uh digest all of that organic material from the Spartina grass that as it turns over, and all those nutrients get released into the soil into the sediments and the waters, and those nutrients feed the juvenile fish and a whole food chain there.
SPEAKER_01So they are the foundation.
SPEAKER_02Yeah, they are. And when I moved to Woods Hole in Massachusetts, um I started working on an entirely different group of microorganisms. Now, you know, there's three domains of life: there's bacteria, there's archaea, and there's eukaryotes. So people and whales and fish and fungi belong to the eukaryotes, and the other two domains are entirely microbial. Um, and in the eukaryotes, most of the uh taxa are microbial, things that you need a micro microscope to see. And uh those are the ones I focus on in the ocean when I'm uh out on ships and bringing samples back to the lab. I study uh the microscopic eukaryotes called protozoa. And you might remember from your high school biology class, you know, a paramecium, a freshwater paramecium, and looking at a meebe. Those are examples of microbial eukaryotes. And in the ocean, there's abundant types of microbial eukaryotes that have very complex interactions with bacteria and archaea to cycle nutrients, the carbon, the nitrogen, the sulfur that fuels the uh ocean life.
SPEAKER_01And and how is how are they different than the terrestrial? Obviously, they can live in water, but how is it different than the than their cousins on the terrestrial side?
SPEAKER_02Um they're different from their cousins on the terrestrial side because they have the ability to live in in salt water, for one. They have the ability to live often at great depths, and you find them all the way to the seafloor and below the seafloor and under thousands of meters of water. Um they they they uh participate in similar food webs just in the ocean.
SPEAKER_01So they're beautiful. Are there any parts of the ocean that don't have them?
SPEAKER_02Um I haven't found them yet. Uh we've we find uh active microbial life uh everywhere that we've looked in the ocean, including places where fish and other animals can't live because they require oxygen. So there are many, many microorganisms that don't require oxygen. They can they can breathe other things, they can breathe nitrate, they can breathe certain metals. They that's what they use to make energy.
SPEAKER_01I'm sorry, you say that quite casually, that there that there is a living being that can breathe metal. That's that's not a sentence that I'm 70. It's not a sentence I've heard before. And you just kind of threw it out there like, you know, when I had my fourth arm, how does how does something breathe metal?
SPEAKER_02Well, what we use oxygen for is is uh it's the it's the what we we take electrons from the food we eat, okay? We take uh electrons from the food we eat, and we we pass them through a complex series of chemical reactions, and at the end of that series of reactions, we generate energy in the form of ATP. That's what keeps us alive. And that's the same for microorganisms. And at the end of that chain of chemical reactions, we dump those electrons onto oxygen by breathing oxygen. And in the case of microorganisms, they have other ways to dump their electrons off, they can dump it on other molecules. Sometimes those molecules are metal, uh metal molecules, sometimes they're nitrate, sometimes they're other compounds. So microbes are very versatile.
SPEAKER_01Wow. Okay. Now, in doing some reading, uh some background uh before our conversation, one of the phrases that you have to know catches people's attention is extreme environment. So tell tell me about extreme environments. What does that mean and how what role are these playing in that?
SPEAKER_02So I uh as an oceanographer, I go out on ships and I study regions of the ocean that people would not call extreme. It's just a water column uh in places where oxygen happens to be depleted. Okay, these areas of the oceans are expanding uh quite a bit these days. But in other cases, my research has explored lesser known habitats, habitats that people would call extreme because they're really bizarre, like uh places on the seafloor where uh superheated fluids exit the seafloor along uh uh plate margins where continental plates are moving apart, sort of like undersea volcanoes. Um I study uh hyper saline uh environments that exist here and there. Okay, these are really, really salty environments, much saltier than the ocean. And I also look at microbial life that's below the seafloor, deep below the seafloor. So people call these extreme environments because there's multiple stressors on the organisms that live there, multiple stressors that you don't ordinarily see.
SPEAKER_01And they have found some way to deal with that.
SPEAKER_02Yes, the organisms that live there have found strategies for surviving, for making energy, for finding carbon, for recycling carbon in many cases. And when we when we study life in these really unusual places, we we can learn lots of interesting things. Like we can we can sometimes isolate organisms from these habitats that produce compounds that are really useful for humans, like new antibiotics or new uh compounds that are useful in industry. Um other angles are if we're looking for life on another planet in a moon of Jupiter, say, uh, we can learn from these environments what types of ornaments live there. Yeah, like you know, if you're gonna look uh in a in a super salty environment below the surface of some planet, you might want to look at a super salty environment here on Earth to see what kinds of life lived here, what makes them unique, and it might give you clues about what types of life to look for on that other planet. So that's another angle.
SPEAKER_01When you mention super salty, are we talking Great Salt Lake or Salt and Sea or what are you talking about?
SPEAKER_02Yeah, any of those places. In my case, I studied a really, really crazy uh set of habitats at the bottom of the Mediterranean uh sea. These are uh anoxic, they have no oxygen, and these are lakes on the seafloor of super salty water. So imagine, imagine, you know, you're looking at a camera from a remotely operated vehicle that's descending through through the ocean in the Mediterranean, and then you get to the bottom near the seafloor, and you start to see something that looks like a mirror on the seafloor. And because that's what it looks like. You see these depressions on the seafloor that are filled with something that's very reflective and mirror-like, and what that is is super, super salty water, ten times saltier than seawater, that accumulates in these depressions. And uh there are very, very interesting uh microbial communities that live in the transition zone between this the bottom water of the normal, you know, Mediterranean Sea and these super salty brines where very, very little life can live because it's so so salty.
SPEAKER_01You said ten times saltier than water. Is this not considered seawater?
SPEAKER_02Um it it is, it is considered um seawater. Um these these uh these lakes um originated from the last time the Mediterranean Sea dried up, the salt, you know, was precipitated and formed like a salt, yeah, you know, a rocky layer. All right, and then when the when the Mediterranean flooded again, some of those deposits became exposed, you know, about uh five million years ago uh to to uh the seafloor and they started to dissolve. And when this the the salts started to dissolve, their salt water is heavier than than less salty water. Okay, so these these very salty waters travel along the seafloor until they find a depression and they accumulate there. So that's the origin of these these what they call deep sea anoxic hypersaline anoxic basins, these brine lakes. Uh and they're so salty that you know you can't you send a remotely operated vehicle down into that brine because it floats. I mean, we're talking about huge vehicles cannot dive into these brines because it's so salty and it's strange. You know, you you go down there and you see bottles and cans and plastic bags and things from cruise ships floating on the surface of this brine. And you see really strange fish, you know, with uh the little lanterns coming off of their heads, and you know, they sort of swimming in and out of the surface of this transition zone. So the fish can't enter the brine itself, but they can they can feed in the transition zone where all the microbes are.
SPEAKER_01So the top of this lake is the bottom of their world.
SPEAKER_02Mm-hmm. Yes. Yep, that's right. And only microbes can really stay in the uh transition zone to the the brine itself, and uh very few of the basins have detectable life in the brine itself, and it's all microbial. Because think of think of how difficult it is for something to live in, something so salty, you know, it it's like if you put something in in that much salt, it draws all the water out of it and just sort of prunes it up, you know? So it's a real challenge for life to survive in like the Great Salt Lake or other places. So there are organisms that can do it, but they have to have specific strategies for doing that.
SPEAKER_01So, how with the difficulties you've expressed, how how is it you're getting samples from the bottom of this?
SPEAKER_02Ah, okay, that's a really good question. So, oceanographers like me use remotely operated vehicles, you know, robotic vehicles that go down to the seafloor and they can collect sediment cores and they can collect water samples and bring them up to the ship. And uh we use these kinds of vehicles for collecting samples all over the world, not just in these extreme environments. So in the other habitats that I study, like the hydrothermal vents, um, we use uh the deep submersible submarine alven can go down where people can go down in the submarine and look at the seafloor and choose where they want to sample and collect different types of samples. And sometimes we use remotely operated vehicles to do this that you control from the ship. And have you gone down in the manned ones? I've been inside Alvin, but I'm extremely claustrophobic. So when uh a submarine $75,000 a day to operate, it's very it's a very tight operation run by incredible engineers who uh pay attention to every little detail of safety. And it's it's an operation that starts, you know, before breakfast in the morning on the ship, and then it's launched, and then it's recovered by 6 p.m. usually, and then they stay up all night recycling the submarine and testing everything. So you don't want to be the person that they have to come back up to the surface for because they're having a meltdown. So I stay, I stay on the ship and and communicate with the people in the submarine and look at what they're looking at.
SPEAKER_01You have that in common with my wife. She can't even go through a car wash. Um I tried to get her certified for scuba. Um, I got certified back in 72. So I've been diving for a while. My first uh my first major in college was marine biology. And um she lasts about 15 minutes into a class we'd paid in full for. And then that was that was the end of her scuba experience. Yeah, um, yeah, yeah. So you mentioned the Mediterranean, uh, but in in some of the notes, you've also mentioned um the Gulf of California slash Mexico in the Indian Ocean. Yeah. Well, tell us what you're doing there.
SPEAKER_02Okay. Well, um, in uh in the Gulf of California, everybody knows the San Andreas Fault, right? So that's the source of all the earthquakes and misery uh associated with that along with the city.
SPEAKER_01I grew up in California.
SPEAKER_02There you go. So the uh that that uh that fracture zone, okay, tr goes right across the Gulf of California. And that's uh an area called Guaymas Basin, and it's an active hydrothermal area, meaning hot fluids percolate up from deep in the earth and uh exit at the seafloor. They can it can look like uh chimneys uh you know rising from the seafloor of of uh you know rocky material that's precipitated with black or white, you know, smoky fluids coming out of them.
SPEAKER_01And that must be otherworldly to see.
SPEAKER_02It is, it's totally otherworldly. And what's really amazing is that in the total absence of dark of light, you have these thriving communities of animals that live close to these vents. You'll see huge tube worms, you know, with big red, you know, uh, you know, feathery structures sticking out of them. You'll see giant clams, calytagena, you'll see shrimp, you'll see fish, you'll see crabs, you know, just covering these areas, and they're there because there are so many microbes living in the water uh in close proximity to these vents, because these vents uh release all these different kinds of nutrients from deep within the earth, and the microbes are there to uh capture those those nutrients to fix the carbon from the carbon dioxide and from you know they they uh capture methane and they produce methane and they capture carbon dioxide and they uh they build that into cells, and the water's like a sort of a thick soup. It's cloudy with microbial life, and that's what's fueling the that's what's the dinner table for all of these animals that are down there. So, what I'm interested in is I'm looking at these microbial eukaryotes, these protozoa, which I wish I could show all your listeners. They're just incredibly beautiful to look at. I can send you some pictures.
SPEAKER_01Please do, and we'll throw them up during the podcast.
SPEAKER_02Yeah. So, you know, they're they're they're just gorgeous to look at. Um, it's like looking at um snowflakes, you know, everyone is a little bit different. There's just so many different shapes and sizes and structures. And I'm I'm interested in the role that those microbial eukaryotes play in those communicate communities. Like, how do they contribute to carbon cycling? You know, how do they interact with the bacteria that are in the waters as well? So there's many interesting things that happen, like there's a lot of symbioses, and that's where two different organisms are living together for the majority of their life cycle, and they exchange important molecules. So we see protists that are covered with certain specific bacteria, and they have a very, you know, they they they exchange nutrients between each other, and that's how they make a living. And um recently I was out on uh recently and a few years ago I was out on a drill ship, the the Joides Resolution that spent uh almost uh two months out there drilling into the seafloor of Guaymas Basin. And so we looked to see how many, you know, how deep could we find evidence of life? And we found evidence of life hundreds of meters below the seafloor. And uh life, yeah, life exists wherever water can reach it and temperature conditions can um allow them to survive. So the highest uh temperature of that a microorganism can survive is somewhere around 121 degrees Celsius, which is well above the boiling point of water. And um then if you have you have pressure, all the pressure of being under 4,000 meters of water in in some cases, in some places, two to four thousand meters of water depending on where you're drilling. And uh you can uh Guaynus Basin um is a very active area. Like there's a lot of uh primary production in the water, so the waters are green at the surface. There are lots of fish, lots of plankton. And so lot all this material falls down and settles on the seafloor of Guaymas Basin, like it does anywhere in the ocean. But in Guaymas, there's the settling rate is very high. So there's thick, thick sediments in Guaymas Basin on the seafloor, you know, hundreds of meters thick. And these sediments get uh percolated by these superheated fluids. And the there's a reaction that happens where the hot fluids, the hot temperature, converts all that buried carbon to really quickly to petroleum compounds. It's like smells, the sediments smell like a gas station. And so on top of everything else, the microbes that live there have to be able to survive exposure to a lot of compounds that many things would find very toxic.
SPEAKER_01Wow. Well, I want to take you to the Indian Ocean, or I want you to take us to the Indian Ocean, but my mind has drifted a little bit, and this may be completely out of your area. But I was thinking about Yellowstone and Old Faithful and the Springs and all those. Is that related to the work that you're doing?
SPEAKER_02Oh yes, totally. Okay, so there's many of my colleagues study Yellowstone because it's easily accessible. Okay, so they they have access to that, and it's uh it's not a marine environment, it's a freshwater environment, but it shares many characteristics. It's extreme in many respects, and the chemistry of the different pools is very different, just like the chemistry of different sites in Guaymas Basin and the chemistry of these deep brine lakes in the Mediterranean are very different lake to lake.
SPEAKER_01So Yellowstone see them for 20 bucks on a walk along a boardwalk.
SPEAKER_02Yeah. So yeah, they're they Yellowstone is an incredibly complex place and a wonderful place to study microorganisms. That's absolutely true.
SPEAKER_01And are the microorganisms, and we're going to get back to Maureen, but while I've got you, are the microorganisms the ones that generate the different colors and the beautiful things that you see in Yellowstone?
SPEAKER_02Um, in some cases. So um a lot of times the colors are due to the minerals that are in the pools in Yellowstone. Okay. Okay, but if you look at some of the uh the little streams that exit from those pools where the waters get a little cooler, you'll see some stringy substances of different colors, greens, reds, oranges, those are all microbial. Okay. Okay.
SPEAKER_01All right, so take us to the Indian Ocean.
SPEAKER_02Okay, so um, yeah, one time I went on a drill ship to the Indian Ocean because uh there were a group of geologists who were studying uh important deep earth processes and and uh they were asking questions about the the ocean crust, the upper and the lower ocean crust. And the the lower ocean crust is um usually quite inaccessible because it's usually under, you know, uh, you know, a thousand meters of of upper crust. But uh the lower oceanic crust, which is just above the mantle of the earth, um, is is uh surprisingly uh exposed fairly close to the seafloor at a p one location in the Indian Ocean where plate tectonics have has exposed it, okay? And the drill ship went to that location and spent, you know, seven weeks there drilling into the lower crust. And you know, that was a strange experience because we were in a part of the ocean where you can totally understand why airplanes can disappear and people can have a hard time finding them. We didn't see a single ship uh for probably six weeks, aside from an occasional uh uh likely pirate uh ship, you know, a big supercharged, you know, speed boat with a bunch of people in it, you know, asking questions of the captain and wanting fuel, asking questions like that. So um the biggest sign of life macrofauna that I saw was a wandering albatross, you know, and that was a welcome sight, you know, after after six weeks of being out there.
SPEAKER_01But you read about from the sailors of hundreds of years ago.
SPEAKER_02Yes, exactly. They're beautiful, beautiful birds, you know.
SPEAKER_01They just either way, I I just have to stop you for a moment. You express some concern about whether uh my viewers and listeners would have an interest in what you're talking about, and let's just do a quick recap. You have talked about breathing metal, extreme environments, other planets, and pirates. What part didn't you think would be interesting? Oh, I don't know. I don't know. It's uh yeah, I I I find this fascinating. But you had you had suggested, and I want to do this, that you could tell us a little bit about ship life uh when you're out there. And I'm guessing it's different than a carnival cruise. Uh and you had mentioned dolphins and refugees and flying fish and and pirates. So in our last couple of minutes, tell us about these uh buffet-filled uh you know, nightclub-based cruise ships that you take to study this.
SPEAKER_02Oh yeah. Well, it's far from a carnival cruise. Uh where we usually we work a 24-hour clock, so we're either working during the night or during the day, people working all the time. Uh you sleep in a bunk with uh in a shared room, you walk the same pathway of stairs and deck levels to eat your breakfast and then you know go to work every day. Uh usually the the expeditions are anywhere from two weeks to three weeks, but in some cases they've been close to two months. And that gets very difficult after about six weeks of that and seeing the same people every day and being in the same hamster wheel. So people get a little squirrely after about six weeks, and they're really glad to get back on shore after that. But if you focus on the really wonderful things about it, uh when you're transiting, you can see dolphins riding the bow waves in many parts of the world. You see flying fish skittering away from the bow waves, uh, you see beautiful birds uh that land on the ship to rest for a while or don't land in the case of an albatross. Uh it when you're stationary, you can be visited at night by squid. Uh, you can see the occasional whale will come snooping around and will swim under the ship back and forth a few times just to see what you're doing. Um, and in the case of the uh Indian Ocean, unfortunately, we had to transit, you know, past uh, you know, close to Somalia and a few other locations where piracy was a concern. So we had to put concertino wire around the deck of the ship and have the water cannons ready. You know, American ships are not are not uh armed, so self-defense has to be creative. But we didn't have any problems. We go through safety drills, you know, for ship safety on every cruise. That's a big part of every week, and that includes drills for piracy and and other concerns. So, you know, you get to experience the wonders of nature when you're out on a ship. You get a full understanding for how the seafloor is being damaged by drag fishing, you know, in vast areas of the uh continental margins. And when you're studying oxygen depletion out in the middle of the ocean, you really understand, you know, how climate change is changing the ocean and who can live there. So you think of it as an Oreo cookie. There are these these huge areas of the ocean off of western continental margins where there's very little to no oxygen um in the in the middle region. So it's kind of like an Oreo cookie. The fish get compressed into the surface or below that depleted zone, and uh that makes them easier to uh they cannot live, fish can't live in if it gets really strongly depleted, like at the eastern tropical, north Pacific, and South Pacific oxygen minimum zones off of Mexico and South America, uh they can't live in that middle mid-waters, you know, anywhere from say 200 meters down to a thousand meters. And uh the greatest migration on Earth is is one that's that's uh of zooplankton that that migrates diurnally with the day and then and the night. And the these big depleted zones are interfering with the migration of these zooplankton. Some cannot cross the the uh the anoxic expanse any longer uh when at times of year when it's so depleted. So you you get an appreciation for how humans really uh must fe have a sense of themselves as being part of the the ecosystem, not you know, a ruler of the ecosystem. And uh the ocean is a beautiful place, but it is not the endless uh repository for waste and the the endless source of food that we've had a tendency to think of it for uh for a long time.
SPEAKER_01Well, Ginny, this has been a blast. Thank you. I have learned so much and you have been so entertaining. Thank you so much.
SPEAKER_02Well, I don't know about that, but it's been a blast for me to to be here with you. And uh I'm excited about this.
SPEAKER_01I'm gonna throw my I'm gonna throw my email up on the screen right now. It's Scott at naturally scott.com. If you've got questions for me, send them. If you've got questions for Ginny, send them. And I will I will get them to her. And if she can enlighten a handful of people, uh that would be great. Um if you happen to be watching this on YouTube, do me a favor and hit subscribe. Every time you do, YouTube throws this out to more people. And I think the more people that hear a story like the one that Ginny's been sharing today, just the better off we are. You can, you know, drop a comment, hit like, whatever you want to do. And Ginny, at the end of every show, I always encourage my audience to get outside. Uh, you know, whatever that is, the back porch, the front yard, the local park, the Serengeti, or, you know, Mariana's trench, whatever it is. Um and when you do and when you're out there, just remember to stay safe and stay curious. I'm Scott Harris of Naturally Scott. This is Ginny Edgecomb who's been generous with her time and knowledge and experience. Thank you so much. You're welcome, thank you. Have a great day. You too.
SPEAKER_00You've been listening to Naturally Scott with Scott Harris. Naturally Scott is hosted by Scott Harris, produced by Justin Harris, directed and edited by Frank Sierra. Follow us on our YouTube channel at Naturally Scott and Instagram at naturally Scott Harris. If this conversation resonated with you, please follow the show, leave a review, and share it with someone who needs to hear it. Naturally Scott thanks you for viewing and listening to this podcast.