Antarctic life – microalgae – podcast
Listen to the third episode of six in the Voice of the Sea Ice podcast series from RNZ science communicator Dr Claire Concannon.
Claire interviews a team of researchers camping out on the sea ice to investigate microalgae (phytoplankton) that live on the bottom of the ice and among the slushy platelet ice layer just below it.
Microalgae and krill hold up the big, complex food web of Antarctica. Scientists are keen to understand these communities and how they might shift as the sea ice cycle changes.
The long-form version of this podcast is on the RNZ website here.
Transcript
Dr Natalie Robinson
I’m making scones with dates, but I decided to use the last of the syrup from the can of peaches, so peach and date scones.
Dr Claire Concannon
Their camp is a series of modified shipping containers set up on the sea ice, with six bright yellow polar tents out in front. One of them is mine for the night.
We’re in the shipping container that serves as the kitchen, and the smell of scones slowly and distractingly fills the space as Natalie and I chat.
But she’s not out here for the baking challenge. Remember from last episode that, in McMurdo Sound, the sea ice has a few layers. As well as solid ice, there’s also the sub-ice platelet layer – a sloshy layer made of big ice crystals that form from super-cooled water, which float up to stick to the underside of the ice.
Natalie and her team are here to study the role that sea ice, and in particular this sub-ice platelet layer, plays in supporting Antarctic life.
Dr Natalie Robinson
It harbours an awful lot of what’s called primary productivity, so this is the very base of the food chain. In particular, algae, which you can think of in a terrestrial sense as like the grass meadows, and the concentrations of algae in platelet ice can be many times higher than it is associated with sea ice that doesn’t have platelet ice. So it’s really a hub for that base of the food chain.
Dr Claire Concannon
By first drilling most of the way through the solid ice and then using a complicated coring system, this team collect the bottom 25 cm of solid ice and then the sloshy layers of platelet ice below. They’ve been doing this in parts of McMurdo Sound where the ice formed at different times. So some formed early in March, another site in May and yet another in August.
The samples are placed in the camp’s lab to defrost – a large blue shipping container at one end of the line of containers. Aimee and Salvatore are already hard at work.
It looks very organised for a container lab.
Dr Aimee van der Reis
I think it has to be – too small a space to be messy.
Dr Claire Concannon
Climbing into this cosy lab, heated inside, it’s one of those times you could forget you’re in Antarctica. On the right is a bench with a microscope set up, and beyond that, a black plastic bag has been rigged up to act like a curtain around a series of pumps with different filters. Once the plated ice samples have melted within the buckets, the processing begins. Aimee explains.
Dr Aimee van der Reis
We take the water and we will run it through what we call a zooplankton tower, and so it’s capturing organisms of different sizes in three layers.
Dr Claire Concannon
Zooplankton is a collective term for a whole bunch of small living things, including krill. They snack on the phytoplankton, the plant-like microalgae.
Dr Aimee van der Reis
Thereafter, we take the remaining water that’s been filtered through these different size filters and that’s where the filtering starts for a diverse number of different studies.
Dr Claire Concannon
Dr Svenja Halfter is interested in the different zooplankton species that show up. Among other things, Salvatore wants to find out if there are microplastics in the samples. Aimee herself is using DNA studies to zoom out and get an overview.
Dr Aimee van der Reis
My focus is looking at the community composition in a general picture and looking at sort of how it all fits together. There’s so much not known about this that it’s quite exciting research.
Dr Claire Concannon
The last biologist in the group is Dr Jacqui Stuart, postdoctoral researcher, surfer, musician, artist and very much a champion of the little guys.
Dr Jacqui Stuart
And everyone you know, you’re like, I’m going to do research in Antarctica, and they’re like, oh, the penguins. And you’re like, yeah mate, they’re all good. But they’re stuffed without these little guys.
You know, there’s big charismatic things that we like to look at. But I’m out here to try and hype up the little charismatic ones so that we can have microalgae on pyjamas one day maybe, you know.
Dr Claire Concannon
Microalgae or phytoplankton is where the whole Antarctic food web begins. If you want penguins and seals and humpback whales and orcas, well, you need these teeny tiny single-celled plant-like organisms taking in sunlight and turning it into food. And while you can’t see them with the naked eye, under the microscope, they definitely have their own charm.
Dr Jacqui Stuart
This is one of the ones that a couple of years ago we saw kind of increase in the thinner sea ice. So this is a diatom, which is one of the main types of algae in the communities in the sea ice. And this one in particular is Nitzschia stellata.
So it’s a long, thin microalgae, and they like to kind of group together. And what we’re looking at here is kind of a partially formed star that they like to form where they all join from one end and create this quite beautiful little kind of fan star array, hence the name stellata. But they’re very diverse.
Dr Claire Concannon
Jacqui grabs another sample. There’s one that looks like a jester’s hat and another that looks like a tiny butterfly – the body a bright green, full of chlorophyll needed to absorb the sunlight, and the wings a translucent outline.
Dr Jacqui Stuart
You can get them in all shapes and sizes, and I think that’s one of the things that I underestimated the amazingness of algae for a very long time.
Dr Claire Concannon
That’s no longer the case. Now a true microalgae frother, Jacqui has a bunch of questions about how they hold up the big complex food web of Antarctica.
The key thing to remember is that different kinds of microalgae make different nutrients that the zooplankton then eat. The zooplankton then in turn get eaten by fish, which get eaten by the penguins or seals, which get eaten by the orca. You get it.
Dr Jacqui Stuart
When you think of a microalgal community, it helps to kind of picture it as the produce section at the supermarket, right? So there are lots of different types of microalgae. They’re not just these single cells that all look similar. They’re quite diverse. They’re quite beautiful. And they all produce different amounts of stuff like proteins and fatty acids, which are things like when you look at the back of a nutrition label, you see monounsaturated fats and things – so it’s that type of nutrients that they’re producing.
So what I’m interested in basically is what does that produce section look like normally? What’s available for things higher in the food web? And how might that change?
Dr Claire Concannon
Changes to when and how the sea ice forms means changes to snow cover and sea ice thickness, which changes the amount of light that gets through, which changes the microalgae community.
Dr Jacqui Stuart
Two years ago when we had similar ice conditions to what we’re seeing now – which were unprecedented at that time but now we’ve had, you know, that twice within the space of 3 years – we essentially saw that there were shifts in the main type of microalgae and there was also less diversity, so less produce available. And that’s why we’re back here asking that question as to, OK, what does that mean for things that actually want to – well that are eating them and that rely on that for survival.
Dr Claire Concannon
Jacqui works out how much algae is in each sample by looking for amounts of chlorophyll. Then she uses DNA to figure out what types of microalgae there are, and then she also looks at the nutrients, the proteins and the lipids that the algae are producing.
As well as the different samples from sites with different-aged ice, she also has manipulated the snow on top of a patch of ice, scraping some off in one area and piling it up in another to change the amount of light available.
Now, to be clear, microalgae don’t just live in the ice, they also live in the water. This is the same phytoplankton that sometimes blooms, and you get giant green patches that can be seen from space. But there’s evidence that the microalgae living in sea ice and in the platelet ice is particularly important.
Dr Jacqui Stuart
The ones that provide the most nutrients for the longest amount of time are the ones in the water column, so you end up with blooms in the spring and things like that. But at certain times a year, especially in the winter, that sea ice and platelet ice microalgal community becomes a lot more important to krill and other critters that grazes on the microalgae. And the ice-associated microalgae can end up being the majority of the nutrients for certain times of year.
Dr Claire Concannon
And not all microalgae are the same. The water column phytoplankton are used to getting a whole bunch of sunlight. The ones that live in ice are adapted to low light levels.
Think of it like running a marathon, says Jacqui. Some people are sprinters and will come out hot. Others will push to the front running downhill or maybe charge uphill. Who’s in front will change throughout the race depending on the conditions.
Dr Jacqui Stuart
During the winter when there’s more ice, those microalgae that can live in the low light conditions, they go out into the head of the pack, and the ones that like more light and those kind of water conditions pull back either into the main body or all the way down into kind of being quite hard to find. But they’re still there, and then when the conditions are right for them again, they move back forward in that marathon pack and take the lead again. So it’s that kind of ebb and flow.
Dr Claire Concannon
As the sea ice cycle changes, this ebb and flow will change too, as will the nutrients available for the rest of the Antarctic Ocean food web, impacting everything from the Antarctic toothfish that’s fished commercially here to the iconic emperor penguins and Weddell seals, who also rely on sea ice for habitat.
Associate Professor Michelle LaRue
Emperor penguins are, I think, some of the most badass animals, because they go through the most extreme situations that I can possibly think of.
Dr Claire Concannon
That’s next time on Voice of the Sea Ice.
Thanks to Dr Natalie Robinson and the platelet ice sampling team.
Reporting for the series was supported by Antarctica New Zealand, with special thanks to Megan Nicholl for her help on the ice and to Anthony Powell for audio recordings.
Tēnā koe i whakarongo mai. Thank you so much for listening. I’m Claire Concannon. Have a great week. Kia pai, te wiki.
Acknowledgements
This podcast is courtesy of RNZ. It is from the Voice of the Sea Ice series by Dr Claire Concannon. The series was made with travel support from the Antarctica New Zealand Community Engagement Programme.
Dr Natalie Robinson, NIWA
Dr Jacqui Stuart, Victoria University of Wellington
Dr Aimee van der Reis, University of Auckland
