Antarctic life – microalgae
What’s it like to live and work on the frozen ocean? A team of researchers are camping out on the sea ice to investigate the small critters and phytoplankton that live on the bottom of the ice and among the sloshy platelet ice layer just below it. From microalgae to krill, these tiny organisms 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.
Introducing Antarctic life – microalgae
RNZ science communicator Dr Claire Concannon gives us a short glimpse into microalgae communities in and below the sea ice in Antarctica. It is part of the third episode in her Voice of the Sea Ice podcast series.
Select here to view video transcript and copyright information.
In some places, the underside of the sea ice looks like giant green clouds. These are the ‘grass meadows’ of Antarctica, made up of phytoplankton – or microalgae – the foundation of the complex food web that powers all life here.
The charismatic microfauna
You know, there are 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.
Antarctic life – microalgae – podcast
This is the third episode of six in the Voice of the Sea Ice podcast series from RNZ science communicator Dr Claire Concannon. Hear about microalgae (phytoplankton) and learn about their sea ice and platelet ice habitats.
Select here to view the video transcript and copyright information.
Dr Jacqui Stuart is the self-described champion of these ‘little guys’. Sitting in a heated shipping container that’s kitted out as a mini laboratory, she arranges a sample under the microscope lens, bringing into focus a tiny floating shape on the attached monitor screen.
It’s a diatom. A long, thin type of microalgae that likes to group together to form a fan star array. But this is just one type of microalgae among a whole community of them. Microalgae come in all shapes and sizes.
Phytoplankton
Phytoplankton are important primary producers in the marine food web. They are microscopic, single-celled organisms that float freely in the ocean. They rely on energy from the sun for photosynthesis and are therefore most commonly found less than 100 metres below the surface. Phytoplankton are eaten by zooplankton.
These are diatoms, under the microscope. Diatoms are one of the most common types of phytoplankton.
Food web foundations
Jacqui is investigating these microalgal communities in the sloshy layer found just under the sea ice of McMurdo Sound. In this layer, big ice crystals known as platelets provide a safe haven from the currents for the algae to live.
Dr Jacqui Stuart
Marine ecologist Dr Jacqui Stuart in a container lab in Antarctica. Her research is deepening our understanding of the critical role microalgae play in the Antarctic food web.
Photo by Claire Concannon.
Microalgae can photosynthesise, just like plants on land do. When they take in energy from the sunlight and use it to make food, it’s the first step in the food web, supporting some of the iconic Antarctic life that we think of: emperor and Adélie penguins, Weddell seals, skua, orca and humpback whales.
The food web in the Ross Sea
This diagram shows how the food web in the Ross Sea, Antarctica, works. The arrows represent the energy flow and go from prey species (these get eaten) to predators (the hunters).
Notes: Baleen whales use baleen plates in their mouths to sieve plankton, krill and small fish from the water. Toothed whales have teeth for capturing prey. Krill is the dominant zooplankton species in the Ross Sea.
Skua (flying birds), phalder, 123RF Ltd; Adélie penguin, rhallam/123RF Ltd; Seal, Isselee/123RF Ltd; Fishing trawler, K_Stuart/123RF Ltd; Krill, Uwe Kils, CC BY-SA 3.0; Humpback whale (Baleen whale), Charles J Sharp CC BY-SA 4.0; Sperm whale (Toothed whales), Gabriel Barathieu, CC BY-SA 2.0; Phytoplankton, Public domain; Silverfish, martin_glhf, CC BY-NC 4.0, sourced from iNaturalistNZ; Toothfish, NOAA, Public domain; Zooplankton, Public domain; Flying squid, Darren Stevens, CC BY 3.0; Bacteria, Ivo Sedláček, CC BY 4.0; Benthic invertebrates, NIWA, CC BY-NC-ND 4.0; Ocellated icefish (Fish), Public domain.
Based on an original diagram by M. Pinkerton for NIWA.
Download a PDF version here.
In the warmer months, when the sea ice melts and there is an influx of nutrients, blooms of free-floating phytoplankton occur – massive patches of green that can be seen from space. It’s the kick starter for the giant Antarctic buffet that attracts the world’s largest whales to these waters each summer.
But in the dark winter and the shorter days of the year, the microalgae associated with sea ice are a vital food source for a host of tiny critters and fish.
That’s why Dr Natalie Robinson (Earth Sciences New Zealand) and her team have been camping out on the land-fast sea ice.
Monitoring microalgae on ice
Dr Natalie Robinson with platelet ice
Earth Sciences New Zealand (formerly NIWA) marine physicist and polar oceanographer Dr Natalie Robinson holds a sample of platelet ice.
Each day, Natalie and her team travel to one of their study sites to collect samples for investigation back in the makeshift biology lab.
Collecting platelet ice cores is a difficult task because it requires drilling down through the solid ice and then devising a way to recover the layers of these sloshing platelet crystals without mixing them all up.
Sampling sea ice and platelet ice in Antarctica
Marine scientist Dr Aimee van der Reis and PhD candidate Salvatore Campanile collect samples of microalgae in sea ice and platelet ice. They use a complicated coring system to collect the bottom 25 cm of solid ice and then the layers of platelet ice below.
Photo by Claire Concannon.
The system that Natalie and her team have engineered took many years to devise and test. It’s used extensively as they work to figure out how microalgal communities change under ice of different structures. The long version of the Life! podcast explains the work involved in the drilling.
Under the sea ice
This undersea view captured by a remotely operated vehicle shows the under the sea ice, which includes platelet ice. Scientists refer to this habitat as the sympagic environment and it includes microalgae and bacterial communities.
Curious about how this photo was captured? Meet Dr Leigh Tait and learn more in Marine Science and Robots.
Snow, solid ice and that sloshy platelet ice can all occur in different thicknesses, which will impact the amount of light that gets through to the phytoplankton. This then impacts what the microalgal community looks like. Some species like high light levels, others not so much.
Different types of phytoplankton provide different nutrients to those that eat them. So as the sea ice cycle changes, there are microalgal winners and losers – Natalie, Jacqui and the rest of the team are keen to figure out this ebb and flow.
Student activities
These activities visually demonstrate the implications of melting:
Simulate the work of Antarctic scientists by making ice cores in Pringles® tubes to investigate the relationship between the brightness of light and length of ice cores.
Related content
Voice of the Sea Ice is a six-part RNZ podcast series that delves into science research and adventure in Antarctica. Explore the other episodes:
A land of ice and ambition: Learn about different types of ice, crevasses and the work to map safe routes across Antarctica for scientists and their equipment.
The heartbeat of Antarctica: Meet and learn from some of the researchers studying the physics of the Antarctic annual sea ice cycle.
Antarctic life – penguins, seals and fish: Scientists are investigating the Antarctic food web to better understand the interconnections.
Changing times in Antarctica: Scientists talk about what sea ice decline means for the world and how they feel about it.
Climate change – where to? Human-induced climate change is impacting Earth’s global systems, including ice melt in Antarctica. What is the world doing to combat it? Where does New Zealand fit in, and are we doing our bit as a nation?
For resources that provide a deeper exploration of other ice forms in Antarctica, go to Icebergs and Glaciers. Antarctic sea ice decline and modelling explains sea ice around Antarctica, and Climate change, melting ice and sea level rise explores ice sheets and ice shelves.
Lichens and mosses are Antarctic lifeforms that also photosynthesise. Read more in Life in the freezer.
In the Connected article Catch my drift, students learn about phytoplankton – tiny floating organisms that form the base of the marine food web. The article looks at two types of phytoplankton – dinoflagellates and diatoms.
Further explore life in Antarctica with these articles:
Activity ideas
In the activity Animal and plant adaptations, students learn about animal and plant adaptations in Antarctic species and use these ideas to design their own unique animal or plant.
The activity Build a marine food web looks at marine food webs in temperate waters, and Making a food web is specific to Antarctica.
The teacher resource Antarctica – literacy learning links lists selected articles from the Connected and School Journal reading series that support the science concepts when teaching about Antarctica.
Useful links
Learn more about platelet ice in this well-illustrated article by Dr Natalie Robinson.
Jacqui Stuart and Natalie Robinson write about their research in this The Conversation article, Antarctica’s sea ice is changing, and so is a vital part of the marine food web that lives within it.
This article explains the sympagic sampler that Natalie and colleagues had to build in order to sample microalgae that live on and within platelet ice under the sea ice.
Listen to Dr Natalie Robinson speaking to The Detail and Morning Report in 2023 about the unprecedented sea ice conditions of that year.
Alison Ballance’s Voices from Antarctica series from 2020 explores what it’s like to live and work in Antarctica.
The Wikipedia page on diatoms has a selection of micrographs showing the diversity of diatoms.
Acknowledgement
This resource is adapted from the work of Dr Claire Concannon for the RNZ podcast series Voice of the Sea Ice. The series was made with travel support from the Antarctica New Zealand Community Engagement Programme.
