Microalgae are tiny organisms that convert energy from sunlight into fuel. The arctic ecosystem depends on them. In springtime, the algae bloom brilliant shades of green and draw tiny crustaceans, fish, birds and more to arctic waters. But what happens in wintertime, when the sun goes down and darkness reins for months? In the depths of the polar night, biogeochemist Clara Hoppe has found evidence that some microalgae are still ready to photosynthesize. Today on the show: how tiny microalgae limbo for their lives and come out more powerful than scientists ever imagined. Want to hear more stories of nature pushing the boundaries of what scientists previously thought possible? Let us know by emailing [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.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What are microalgae and why are they important?
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You're listening to Shortwave from NPR. Hey, short ravers, Emily Kwong here. And today we are headed north to Norway, the land of the midnight sun.
The sky looks like cotton candy the whole day because you have a sunrise that doesn't stop. It's just a full day of sunrise or sunset.
Chapter 2: How does the polar night affect the Arctic ecosystem?
Because Earth rotates on a tilt, there is a period of time during the summer where the North Pole always faces the sun, creating a polar day or perpetual sunlight. But in exchange, there's also a period of time during the winter of perpetual darkness. That's called the polar night.
So the polar night is the period between the last sunset in fall and the first sunset in spring, during which the sun never rises in the Arctic for several months.
This is Clara Hopper. She's a biogeochemist at the Alfred Wegener Institute in Germany. But a lot of her fieldwork is based here, around the Arctic Circle. During the polar night, she says, it's like everything is in grayscale.
When it's really dark, it's really a black and white world, I would say, where you see some gray shades of things and you see stars and the moon. It's really quiet here. There's wind, there's instrument noise, there's ship sounds and snowmobiles, but like natural sounds, it's probably mostly the wind and the snow moving. It's a very big, dark world.
Chapter 3: What did Clara Hoppe discover about microalgae during her research?
And because you're only seeing what you see with your little headlamp, you see very, very little and you feel very small.
In the winter of 2020, Clara embarked on an expedition into the heart of the polar night to study microalgae, these photosynthesizing microorganisms that are super small and delicate.
The most intriguing and beautiful group of organisms we found are diatoms. They are a group of microalgae that... built these little boxes out of glass, out of silica, that they use as grazer protection.
Clara thought that these microalgae might be the key to understanding the limits of photosynthesis. That's the process used by plants and microalgae to turn light into food.
When there's absolutely no light, we can be sure that there is no...
photosynthesis but we don't know how low this lower limit of light actually is where photosynthesis is possible you know you describing this what immediately comes to mind is limbo like how low can you go yes it's almost like you were studying like photosynthetic limbo or something yeah but we really didn't know um how low they could really go
So today on the show, we're headed into the polar night. How tiny microalgaes stare into the abyss, limbo for their lives, and come out more powerful than scientists ever imagined. You're listening to ShoreWave, the science podcast from NPR. Clara, thanks to your work, I have learned that microalgae are found in the Arctic. They exist up there.
And for a long time, scientists thought that microalgae were basically dormant for much of the year. Can you tell me what the traditional thinking was about their existence?
So the traditional thinking was very much when there is no light, there can't be active light. So what people have assumed is happening is that these cells hibernate. So they are in a resting stage. Some of them form actual resting spores that are very durable. And then they can overwinter, for example, in the sea ice.
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Chapter 4: What was the traditional view of microalgae in winter?
So on a weekly basis, we sampled the microalgae in the water column. So in the water under the ice and then in the ice itself. So we took water samples and we drilled cores out of the ice flow to study which algae are there and in which physiological state.
Science is fun. Yeah. Okay. So you're out there gathering ice, gathering seawater. Where is this all happening?
Yeah. So the water sampling initially happened mostly at a hole next to the ship, which was very convenient because then the samples were directly on the boat. But then in beginning of March, we had a lot of dynamics in the ice and And it destroyed our hole. So we couldn't sample anymore. And then we moved to Ocean City, which existed throughout the whole winter.
Ocean City is like a different location on the ice where you all gathered samples.
But it meant us dragging hundreds and hundreds of liters of water over the flow of... up the gangway and into the labs. So it was really, you know, us pulling those buckets and buckets of water on little pulkas, little sledges behind us through the snowstorm to the boat. So it was a lot of physical work involved getting those samples.
Wow. Science is not fun sometimes, actually.
Well, at least you can do it in the cold. You know, if people that work in the tropics have to do that in like hot human conditions. So I much rather do that at minus 20. Absolutely.
So what did you find within these samples? What was the biggest finding?
So the biggest finding for me was the super early increase in the biomass and activity of these microalgae. So we found just a few weeks after the first sunrise, we found the biomass of the microalgae increasing both in the water column and the sea ice. So the microalgae were growing.
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Chapter 5: How did Clara challenge the traditional view of microalgae?
Yes, they were growing. That's so cool. And just such a big deal that you found evidence of photosynthesis more north in even darker conditions than you did in Svalbard back in the day. And a key part of this... of course, was working with scientists to measure the actual levels of light under the Arctic sea ice, the levels at which this photosynthesis was happening.
And you documented a very low level of light, about 0.04 micromoles per second per square meter. So why was that such a big deal that you caught that, that you caught Arctic microalgae photosynthesizing at that low of a level?
Because it's several orders of magnitude lower than what people usually assume. For example, what is put into those big global ecosystem and ocean models. And if this light level is really several orders of magnitude lower, that means that there is a lot more productivity in parts of the oceans that we thought wouldn't be productive.
So, Clara, how are microalgae able to do this? How are they able to... you know, fire up their photosynthetic engines the moment the tiniest bit of light hits.
I mean, they must be incredibly efficient. They must transfer all that energy that comes in into biomass production. And I guess to some extent, we need to solve the riddle of what they actually do to survive the polar night, the proper darkness. But there seem to be a range of different mechanisms that allows them to survive the polar night. And those mechanisms...
don't respond to the increase in light, but they may give them some background energy that allows them to then start growing as soon as the light comes back.
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Chapter 6: What were the findings from Clara's expedition in 2020?
Oh, can you give me an example of one of those mechanisms that might give them that background energy?
So phytoplankton, even though they do photosynthesis, they are not... only plants in a traditional way we call them mixotrophs so they while they do photosynthesis they can also eat like an animal oh so some species can do something we call phagotrophy which is basically
eating bacteria or other small phytoplankton cells and then other species can do or probably most species can do something we call osmotrophy which is taking up dissolved organic compounds from the seawater so dissolved sugars or amino acids or something like that They're like omnivores. They like eat plants and meat or something.
Chapter 7: How do microalgae adapt to extreme conditions?
I think they do whatever they can to like, you know, fill up their energy reserves.
They're the ultimate survivors. Well, this is just such a paradigm shift from what has been said about Arctic life, polar nights, and what's really going on in our ocean. How has this shaped your view of the polar night and what's really going on there?
I think it's mostly shaped a feeling of not knowing. I mean, if you have those paradigms and then you realize that they can't really explain your observations, then you are in this, what is, you know, the magical science world. where you are like, whoa, I don't understand this at all. And there's so many things I want to study and find out.
So it's really, you know, the beginning of solving this riddle is understanding that it's a riddle. So you start thinking about a lot of different things that you haven't really been thinking before. And that's really the most fun.
Yeah. And that maybe the wintertime ocean is just far more alive than people thought. Yeah. Clara, thank you so much for coming on Shortwave to talk about this. Thank you for the interest. If you liked this episode, make sure you never miss a new one by following us on whichever podcasting platform you're listening from.
And if you have a science question you'd like us to investigate, send us an email at shortwave at npr.org. This episode was produced by Hannah Chin and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts. Robert Rodriguez was our audio engineer. 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, the science podcast from NPR.
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