Sea Camp: The Largest Daily Migration On Earth

Summary

Short Wave: Sea Camp Episode Summary
Title: Sea Camp: The Largest Daily Migration On Earth
Release Date: July 28, 2025
Hosts: Regina Barber and Emily Kwong
Guest: Noel Boland, Fisheries Biologist at NOAA

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Exploring the Twilight Zone of the Ocean

In this episode of Short Wave’s Sea Camp series, hosts Regina Barber and Emily Kwong delve into the enigmatic Twilight Zone of the ocean, also known as the mesopelagic zone, which spans depths of 200 to 1,000 meters (approximately 650 to over 3,000 feet). This zone is characterized by dim sunlight and remains one of the least explored parts of the ocean due to its challenging conditions, including high pressure and low oxygen levels.

Regina Barber opens the discussion by likening the Twilight Zone to the mysterious Twilight Zone TV show, highlighting its elusive nature (00:53). Emily Kwong emphasizes the difficulty in accessing this zone, noting the high pressure and scarcity of oxygen that deter extensive human exploration (01:09).

The Largest Synchronous Migration

The conversation shifts to a fascinating discovery from World War II, where military sonar operations inadvertently observed unusual signals bouncing off what appeared to be the ocean floor moving upwards (01:34). This anomaly puzzled scientists until Noel Boland explained that these signals were actually the result of the largest synchronous migration on Earth.

This daily migration, known as diel vertical migration, involves massive numbers of mesopelagic organisms, including mollusks, shrimps, jellyfish, and the uniquely adapted flashlight fish, ascending to the ocean's surface under the cover of night to feed and then returning to deeper waters before dawn (01:50 - 02:43). Emily Kwong humorously compares the migration distance to walking from San Diego to Los Angeles for dinner, underscoring the immense scale and energy involved (02:18).

Noel Boland highlights the significance of these organisms in global ecosystems, stating, “They matter for our ability to understand how our habitats are linked” (12:02).

Carbon Cycle and Ecological Impact

The hosts and Boland explore the crucial role these migrating organisms play in the carbon cycle. As these creatures consume carbon-rich phytoplankton at the surface, they transport carbon to deeper waters through their waste (poo and fecal matter) and when they die, effectively sequestering carbon in the mesopelagic zone (06:48 - 07:38). Emily Kwong explains, “Whatever they've consumed, they take it back down to depth and into the mesopelagic” (06:51).

This process helps mitigate atmospheric CO₂ levels, as the carbon is stored in the ocean rather than remaining in the atmosphere. However, Boland raises concerns about human activities such as mining and fishing in the Twilight Zone, which can disrupt these natural processes by disturbing sediments and releasing stored carbon back into the atmosphere (09:03 - 09:52).

Human Impact: Fishing, Mining, and Climate Change

The episode further examines the impact of climate change on the Twilight Zone. Emily Kwong notes the expansion of low-oxygen pockets within this zone, a phenomenon known as shoaling, which creates hostile environments for many organisms not adapted to such conditions (09:56 - 10:44). Regina Barber aptly compares this to desertification, where regions unsuitable for life are spreading, pushing species to the margins of their habitats (10:44 - 11:06).

Boland stresses the urgency of understanding these changes, stating, “If we can't get our science out, we can't get the word out, then I think what ends up happening is we. We all start moving in the dark” (11:23). He underscores the necessity of continued research to map the distribution and behavior of Twilight Zone organisms and to communicate these findings effectively to the public (11:08 - 11:23).

The Path Forward: Research and Communication

In discussing future research priorities, Boland emphasizes the importance of not only conducting studies on the Twilight Zone but also effectively communicating their implications for human society and the planet. He highlights the challenges posed by funding cuts to NOAA and the broader issue of public engagement in marine science (12:02). Boland expresses concern over the loss of valuable scientific data and stresses that even seemingly obscure species play critical roles in maintaining ecological balance (12:02 - 13:02).

Regina Barber and Emily Kwong conclude the conversation by reiterating the significance of the Twilight Zone’s health to the planet and humanity, encouraging listeners to support scientific research and advocacy efforts.

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Key Takeaways:

• Twilight Zone (Mesopelagic Zone): A mysterious ocean layer between 200 to 1,000 meters deep, crucial for global carbon cycling.
• Diel Vertical Migration: The largest synchronous migration on Earth, where mesopelagic organisms move to the surface at night to feed and return to depth by day.
• Carbon Sequestration: Migrating organisms play a vital role in transporting carbon from the atmosphere to the deep ocean, aiding in climate regulation.
• Human Impacts: Activities like fishing and mining disrupt the Twilight Zone’s ecosystems, releasing sequestered carbon and harming marine life.
• Climate Change: Leads to expanding low-oxygen areas in the Twilight Zone, threatening many species and overall ocean health.
• Research and Communication: Ongoing scientific studies and effective public communication are essential to understand and protect this vital ocean zone.

Notable Quotes:

• Emily Kwong (02:18): “So that's like saying, oh, Emily, you know, I'm really hungry. We're in San Diego right now. What are we gonna do for dinner? I know the sun is going down. Let's start walking to Los Angeles for dinner.”
• Noel Boland (12:02): “You can do anything.”

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This episode underscores the critical importance of the Twilight Zone in maintaining ecological balance and combating climate change, while also highlighting the pressing need for continued research and public awareness.

Transcript

[Regina Barber]

This Message comes from AmazonOne Medical. Ever gotten sick on vacation? AmazonOne Medical has 24. 7 virtual care, so you can get help no matter where you are. It's kind of like the room service of medical care. Thanks to Amazon Healthcare just got less painful. You're listening to Short Wave from npr. Hey, short wavers. Regina Barber here and Emily Kwong back with our next installment of the Sea Camp series. Em, where are we going? This week, 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 3,000ft. And it's where the sunlight is still present, but it's very dim. 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.

[Emily Kwong]

Do do do do do do do do do?

[Regina Barber]

It is. It is. Noel Bo 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.

[Emily Kwong]

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.

[Regina Barber]

So humans aren't exploring down there very often. 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.

[Emily Kwong]

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

[Regina Barber]

But that didn't make any sense because the bottom of the ocean should have been farther away. And even weirder, it seemed like the.

[Emily Kwong]

Bottom was moving up. What?

[Regina Barber]

Yeah. Scientists would eventually learn that they were seeing the largest synchronous migration on Earth when a massive amount of Twilight Zone living organisms come up and. And travel to the shallows to feed under the COVID of night's darkness. That is really, really fascinating. Yeah, it happens every day at Twilight in the Twilight Zone. But the movement of these organisms is just a huge distance. Noelle said, think of it this way.

[Emily Kwong]

So that's like saying, oh, Emily, you know, I'm really hungry. We're in San Diego right now. What are we gonna do for dinner? I know 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. Wow.

[Regina Barber]

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

[Emily Kwong]

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.

[Regina Barber]

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 shortwave's Sea Camp, the ocean science series from npr. This message comes from Charles Schwab. When it comes to managing your wealth, Schwab gives you more choices like full service, wealth management and advice when you need it. You can also invest on your own and trade on thinkorswim. Visit schwab.com to learn more.

[Noel Boland]

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[Regina Barber]

I'm going to take over the episode from here and have with me Noelle 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?

[Emily Kwong]

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. Wow.

[Regina Barber]

In the Twilight Zone.

[Emily Kwong]

In the Twilight Zone.

[Regina Barber]

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?

[Emily Kwong]

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. Yeah.

[Regina Barber]

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.

[Emily Kwong]

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

[Regina Barber]

Oh, my gosh, that's so smart. I know. So it's not only the fish that are going up and down, and that's happening every day. 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?

[Emily Kwong]

Sure. So we all contain carbon.

[Regina Barber]

We're carbon life forms.

[Emily Kwong]

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

[Regina Barber]

Yeah.

[Emily Kwong]

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 into the mesopelagic. Then they expel waste that isn't going back up to the surface. It's falling down as poo. As poo and snow.

[Regina Barber]

And snow, as we call it.

[Emily Kwong]

Right. Or they. And. Or they've eaten at the surface and eventually they die. Maybe they die at death.

[Regina Barber]

That brings the carbon back down.

[Emily Kwong]

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

[Regina Barber]

I mean, what's incredible about this carbon is it's coming from the atmosphere as CO2.

[Emily Kwong]

Right.

[Regina Barber]

And then it.

[Emily Kwong]

That's right.

[Regina Barber]

It's getting absorbed by phytoplankton. Which are eaten by zooplankton, which are eaten by larger predators. The carbon just keeps sinking down. But 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?

[Emily Kwong]

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. 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 sequestered or fallen and staying at the bottom.

[Regina Barber]

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.

[Emily Kwong]

That's right.

[Regina Barber]

Is there currently fishing and mining that touches the twilight zone?

[Emily Kwong]

Yes. Fishing in the twilight zone or mesopagic Is not the most efficient use of resources like fuel, ship time, because it's so expansive.

[Regina Barber]

Yeah.

[Emily Kwong]

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 mesopelagic or twilight zone, and then you scoop things up and you bring them up.

[Regina Barber]

Yeah.

[Emily Kwong]

Through the zone, 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.

[Regina Barber]

How is climate change impacting the twilight zone?

[Emily Kwong]

One example is that we are getting the expansion of low oxygen concentrations that exist in pockets in the twilight zone are expanding, and only specialized organisms in these zones can inhabit them with success. 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. Wow. And that's a bad thing for the organisms that cannot inhabit those regions.

[Regina Barber]

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.

[Emily Kwong]

That's right. Yeah, that's right.

[Regina Barber]

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?

[Emily Kwong]

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. 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.

[Regina Barber]

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

[Emily Kwong]

I mean, you said it. Yeah, 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 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 mesoplagic 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 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 for school, you can do anything.

[Regina Barber]

Noel Bolen 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 Sea Camp series. It's been really great to talk to you.

[Emily Kwong]

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

[Regina Barber]

Shortwavers you do not want to miss out on the Sea Camp 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 Ko Takasugi Chernohin. 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 Shortwave C Camp from npr.

[Noel Boland]

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