Sea Camp: The Largest Daily Migration On Earth

The twilight zone of the ocean is a mysterious place. At 200-1000 meters below the surface, it's a tough place to study. That's why, during World War II, people reading sonograms from this zone were perplexed when it looked as if the ocean floor was moving up. Every day. And then back down again before dawn. In this latest installment of Sea Camp https://www.npr.org/series/g-s1-75877/short-wave-sea-camp, we explore what this historical mystery has to do with the Earth's ability to cycle and store carbon in the ocean's watery depths. SIGN UP https://www.npr.org/newsletter/sea-camp?utm_source=feeddescription FOR OUR SEA CAMP NEWSLETTER! WE WORKED SO HARD ON IT! Interested in more ocean mysteries? Let us know at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

  This message comes from Schwab. At Schwab, you can get everything from self-directed investing to full-service wealth management, all in one place. No matter your investing goal, life stage, amount to invest, or know-how, you can invest your way with Schwab. You're listening to Short Wave from NPR.

• 0:22Regina Barber?

  Hey, Short Wavers. Regina Barber here.

• 0:24Emily Kwong?

  And Emily Kwong.

• 0:25Regina Barber?

  Back with our next installment of the Sea Camp series.

• 0:29Emily Kwong?

  Yes.

• 0:29Regina Barber?

  Em, where are we going this week?

• 0:31Emily Kwong?

  We are diving into the twilight zone of the ocean. That's 200 to 1,000 meters below the surface, or about 650 to more than 3,000 feet. And it's where the sunlight is still present, but it's very dim.

• 0:45Regina Barber?

  The Twilight Zone. I love this name. It makes me think of one of my favorite TV shows. Is it mysterious, like the show is?

• 0:52Emily Kwong?

  Do, do, do, do, do, do, do, do. It is. It is. Noel Boland, the marine biologist at the National Oceanic and Atmospheric Administration, who we met last week, says, "We don't know a lot about the Twilight Zone because of its depth," which is also known as the mesopelagic zone.

• 1:09Speaker 03

  It is hard for us to access it. As you can imagine, there's great amounts of pressure. There's not a lot of oxygen, and it's deep.

• 1:16Regina Barber?

  So humans aren't exploring down there very often?

• 1:19Emily Kwong?

  No. However, during World War II, militaries were using sonar to look for enemy submarines in the ocean, in the Twilight Zone, hundreds of meters below the surface. And some of the people looking noticed something kind of odd.

• 1:34Speaker 03

  The signal coming back was so-- it was as if they were bouncing the sound off the bottom of the ocean.

• 1:39Emily Kwong?

  But that didn't make any sense, because the bottom of the ocean should have been farther away.

• 1:43Regina Barber?

  Mm-hmm.

• 1:44Emily Kwong?

  And even weirder.

• 1:45Speaker 03

  It seemed like the bottom was moving up.

• 1:49Regina Barber?

  What?

• 1:50Emily Kwong?

  Yeah. Scientists would eventually learn that they were seeing the largest synchronous migration on Earth.

• 1:56Regina Barber?

  Wow.

• 1:56Emily Kwong?

  When a massive amount of Twilight Zone living organisms come up and travel to the shallows to feed under the cover of night's darkness.

• 2:05Regina Barber?

  That is really, really fascinating.

• 2:07Emily Kwong?

  Yeah, it happens every day at twilight, in the Twilight Zone. But the movement of these organisms is just a huge distance. Noel said, "Think of it this way."

• 2:18Speaker 03

  So that's like saying, "Oh, Emily, you know, I'm really hungry. We're in Santa Yara right now. What are we going to do for dinner?" I, no, the sun is going down. Let's start walking to Los Angeles for dinner, and we need to walk back. Before the sun comes up. It's that kind of distance.

• 2:33Emily Kwong?

  Wow. And this mass movement is called deal vertical migration. And it includes mollusks, shrimps, jellyfish, and Noel's personal favorite.

• 2:43Speaker 03

  It's called a flashlight fish because one of the places it has some light organs are right in front of its eyes, facing forward like they've got headlights.

• 2:53Emily Kwong?

  It is critters like these that perform an essential service to not only their ecosystems, but to the entire Earth. Today on the show, how the largest synchronous migration of animals on Earth pulls carbon out of the atmosphere and stores it in the ocean. I'm Regina Barber. And I'm Emily Kwong, and you're listening to Short Wave's Sea Camp, the ocean science series from NPR.

• 3:22Speaker 04

  Stay tuned for the following announcements and messages from our sponsors. This message comes from 80,000 Hours. They're a nonprofit, and they're not asking you to buy anything. They want to help you find work that stays relevant, pays the bills, and makes a difference. Their career guide covers what makes for a dream job, how automation could affect your career choices, and how your work can have a positive impact. The new edition is an international bestseller, and it's free at 80000hours.org/NPR.

• 3:51Speaker 00

  This message comes from Midi Health. Most women never get real answers about their hormonal health. Midi is changing that with virtual care covered by most major insurances. Understand your hormones. Visit joinmidi.com to book your first visit today.

• 4:07Speaker 04

  This message comes from International Medical Corps. When crises strike, every second matters. And that's why International Medical Corps moves fast. From the flooding in Nepal to earthquakes in Venezuela, they deliver lifesaving medical care and supplies around the world while training local health workers to ensure care continues long after the emergency ends. This giving season, your generosity saves lives and builds resilience for tomorrow. Learn more or donate today at internationalmedicalcorps.org/NPR.

• 4:40Emily Kwong?

  So I'm going to take over the episode from here and have with me Noell Boland from NOAA to talk about the Twilight Zone of the ocean. Not the television show, though we appreciate its legacy. This ocean zone is very aptly named because it is still very mysterious. And it sounds like a lot of fish live in this zone. How much of the ocean's fish live in the Twilight Zone?

• 5:03Speaker 03

  I love that you use the word mysterious to describe this section of the ocean because it is mysterious. You know, so like, there's so much ocean. And so for us to be able to take samples of it, observe it, we can't get all of it at any time. There's no way. So we have to make inferences based on small sample sets. And so what we do know is that two families make up the most abundant in terms of biomass and number of fishes in the world, and that's where they live.

• 5:33Emily Kwong?

  Wow.

• 5:33Speaker 03

  And so

• 5:34Emily Kwong?

  In the Twilight Zone.

• 5:35Speaker 03

  In the Twilight Zone.

• 5:36Emily Kwong?

  And I know critters in the Twilight Zone, they have all kinds of adaptations. Some of them, for instance, have big eyes to try to capitalize on the lack of light. How else have critters adapted? Like, what do they even look like down there?

• 5:48Speaker 03

  Yeah, so they're not muscular. They're rather squishy. And so you think, well, they're not using muscles to deal with this vast distance that they have to travel. Which is actually really smart, because if you use a lot of muscle to move that kind of distance, you would have to consume so much food to maintain that muscle.

• 6:07Emily Kwong?

  Yeah. You were saying earlier, too, that for us, the distance these organisms travel every day would be like us walking from San Diego to LA and back, which I would get so hungry.

• 6:19Speaker 03

  Exactly. I mean, the amount of snacks you'd have to carry would just be really inconvenient.

• 6:25Emily Kwong?

  Yeah.

• 6:25Speaker 03

  And so what they have inside of them are swim bladders. And they inflate their swim bladder when they need to start moving up. And when it's time to move back down, they deflate that bladder.

• 6:36Emily Kwong?

  Oh, my gosh, that's so smart.

• 6:39Speaker 03

  I know.

• 6:40Emily Kwong?

  So it's not only the fish that are going up and down and that's happening every day. Uh, and not just fish, obviously lots of organisms, but it's also carbon. Can you explain how the carbon cycle works in the ocean? And what role these organisms are playing in it?

• 6:56Speaker 03

  Sure. So we all contain carbon.

• 6:59Emily Kwong?

  We're carbon life forms.

• 7:01Speaker 03

  We are carbon life forms, just like these fishes and the other organisms that are moving up and down.

• 7:06Emily Kwong?

  Yeah.

• 7:06Speaker 03

  Well, as they're making their living, just like you and me, as they move up to the surface to eat other organisms that are also carbon life forms. They then take that carbon with them, whatever they've consumed, they take it back down to depth. And that into the mesopelagic, then they expel waste. That isn't going back up to the surface, it's falling down.

• 7:33Emily Kwong?

  As poo.

• 7:34Speaker 03

  As poo and snow.

• 7:36Emily Kwong?

  Or in snow, as we call it.

• 7:39Speaker 03

  Right. Or they, and or they've eaten at the surface and then eventually they die, maybe they die at depth.

• 7:44Emily Kwong?

  And that brings the carbon back down. Yeah.

• 7:46Speaker 03

  That's right. And so this is a very simplistic way, of course, of without going through actual equations.

• 7:51Emily Kwong?

  I mean, what's incredible about this carbon is it's coming from the atmosphere as CO2, right? And then it's getting absorbed by phytoplankton, which are eaten by zooplankton, which are eaten by larger predators. Um, the carbon just keeps sinking down. But um, silly question, how does the carbon that's then in the bottom of the ocean come back up? And do we even want it to?

• 8:12Speaker 03

  So some of the carbon that will come back up will come back up in the form of animals that are consuming detritus or consuming other organisms that have fallen, you know, maybe a falling body or something. Um, they'll eat that carbon and then one way is that if it's a fish and it's going to spawn and release eggs, those eggs float right back up to the surface over time. It takes time for that to happen. Mining is another way that a lot of people are talking about right now. When we are scooping things up and bringing them up to the surface, forcing them up to the surface, we are releasing the carbon that has been.

• 8:50Speaker 03

  Sequestered or fallen and staying at the bottom.

• 8:53Emily Kwong?

  Yeah. You know, I think when it comes to mining and logging and all these practices that serve our human needs, we forget that what we're ultimately moving around a lot of the time is carbon and we're playing a role in the carbon cycle in that way.

• 9:05Speaker 03

  That's right.

• 9:06Emily Kwong?

  Is there currently fishing and mining that touches the Twilight Zone?

• 9:11Speaker 03

  Yes. Fishing in the Twilight Zone or Mesoplagic is not the most efficient use of resources like fuel, ship time, because it's so expansive.

• 9:24Emily Kwong?

  Yeah.

• 9:24Speaker 03

  But when you are headed to the bottom of the ocean to maybe mine for minerals, you drop your equipment from the ship through the Mesoplagic or Twilight Zone and then you scoop things up and you bring them up.

• 9:39Emily Kwong?

  Yeah, through the zone.

• 9:41Speaker 03

  Sediments through the zone. You're disturbing that habitat because naturally things are falling, you're filtering stuff, and then you're discharging the stuff that you don't want and it's clouds and plumes that are going to move through the sunlight zone and the Twilight Zone. So you're upsetting those, those environments.

• 10:01Emily Kwong?

  How is climate change impacting the Twilight Zone?

• 10:04Speaker 03

  One example is that we are getting the expansion of low oxygen concentrations that exist in pockets in the Twilight Zone are expanding and, and, and only specialized organisms in these zones can inhabit them with success.

• 10:22Emily Kwong?

  Yeah.

• 10:23Speaker 03

  And it's not, it's not the majority of them. As the water warms, there's less oxygen available and so you get lower oxygen concentrations and that makes a hostile living environment for a lot of organisms. And these low oxygen areas in the Twilight Zone are, are expanding and we call it shoaling when they move towards the surface.

• 10:47Emily Kwong?

  Wow.

• 10:48Speaker 03

  And that's a bad thing for the organisms that cannot inhabit those regions.

• 10:53Emily Kwong?

  It's almost like a kind of habitat loss. Like I'm picturing. Almost as if desert conditions are spreading throughout the ocean, except deserts are great. It's just the concept that regions where there isn't what life needs, in this case, oxygen, are just growing. And so, things are getting pushed to the margins because of it.

• 11:14Speaker 03

  That's right. That's right.

• 11:16Emily Kwong?

  Wow, that's really hard. Well, in, given how important the Twilight Zone is to the health of the planet, the health of humans, what research do you think is essential right now for people to be doing on the Twilight Zone?

• 11:31Speaker 03

  I think continuing research, understanding distribution and abundance of the different organisms and how they work together and how they interact. This is research that's happening and it's ongoing.

• 11:41Emily Kwong?

  Yeah.

• 11:42Speaker 03

  Something that I think is really important in terms of research is finding out the best ways to communicate the findings of these results and how they impact humans, so that more people know about it and more people can care and then have the chance to make changes.

• 12:00Emily Kwong?

  How is that hope of yours complicated in this reality with so many funding cuts to NOAA affecting research and also public engagement?

• 12:11Speaker 03

  I mean, you said it.

• 12:12Emily Kwong?

  Yeah.

• 12:13Speaker 03

  That's it. If we can't, if we can't get our science out, if we can't do our science, we can't get the word out, then I think what ends up happening is we, we all start moving in the dark. I'm scared that we're gonna, we're gonna lose a lot of, of information that's in the works and then we just don't know what the right and left hand are doing. I think some people view scientific research on something like a little mesoplaic fish is just, you know, an inflated privilege that you just get to look at these little fishes that don't matter for anything. But they do. They matter for our ability

• 12:53Speaker 03

  to understand how our habitats are linked. And I believe there's room for all of us. We just have to change the way we do some things, some big changes. But, golly, it's the thing I say to my kid every morning when I drop him off at school, "You can do anything."

• 13:10Emily Kwong?

  Noell Boland is a fisheries biologist at NOAA. Thank you for coming on the show and giving so much of your time to help all of us understand the Twilight Zone and just the ocean for the Seacamp series. It's been really great to talk to you.

• 13:24Speaker 03

  Thank you. I really enjoyed this, Emily. This has been an absolute privilege and joy. Thank you.

• 13:30Emily Kwong?

  Short Wave-ers, you do not want to miss out on the Seacamp newsletter because if you sign up, maybe we'll do it again. This newsletter dives deep into each ocean zone. It's got comics, it's got games, it's got ocean research. What else could you want? And if you want to support our show, share it with a friend. Follow us on your podcast platform and know we are grateful for your support. This episode was produced by Burley McCoy. It was edited by our showrunner Rebecca Ramirez and fact-checked by Tyler Jones. The audio engineer was co-Takasugi Chernowen. Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thank you for listening to Short Wave Seacamp from NPR.

• 14:22Speaker 04

  Stay tuned for the following announcements and messages from our sponsors.