Shedding Light on Antarctic Microalgae Species: How might they cope in a brighter future?
Antarctica’s sea ice might look barren from above, but beneath its frozen surface lies a hidden world where many microalgae species thrive. These tiny organisms are the unsung heroes of the polar food web, supporting everything from krill to whales. But as sea ice thins and snow cover changes, the amount of light reaching these microalgae is changing—dramatically.
Our recently published study investigates how two Antarctic microalgae species, Nitzschia cf. biundulata (a diatom) and Polarella glacialis (a dinoflagellate), respond to varying light levels in controlled lab conditions. The results reveal not just their resilience, but also potential ripple effects for Antarctic ecosystems.
Antarctic microalgae cultures used in the experiment.
How did we do this?
To understand how light impacts these microalgae, we designed a laboratory experiment with three distinct light levels to simulate different sea ice and snow thicknesses. This allowed us to investigate how varying light availability influences microalgal physiology. Our experiment focused on two key approaches to uncover these changes:
Why Fatty Acids?
Fatty acids are essential components of cellular membranes and energy storage. By examining changes in fatty acid composition under different light levels, we can infer how microalgae adjust their cellular structures and energy reserves to cope with stress. These changes can also influence the broader Antarctic food web, as fatty acids are vital nutrients for higher organisms.
What is Transcriptomics?
Transcriptomics is the study of which genes are active (or expressed) in an organism at a given time. By analyzing the RNA produced by our microalgae under different light conditions, we could identify molecular strategies they use to adapt. For example, some genes might help optimize photosynthesis, while others could regulate stress responses. Together, fatty acid and transcriptomic analyses provide a comprehensive view of physiological and molecular changes.
Experiment design and key findings from the different light levels.
Key Findings
Fatty Acid Production
Nitzschia cf. biundulata thrives in brighter conditions, producing more energy-storing fatty acids.
Polarella glacialis increased the production of certain polyunsaturated fatty acids (PUFAs), including octadecapentaenoic acid (C18:5N-3) under different light conditions. While PUFAs are essential for maintaining cell function and survival in extreme environments, the increased production of certain PUFAs could signal potential emerging threats. For instance, octadecapentaenoic acid has been identified as a molecule that can be toxic to fish, with fish mortalities linked to other microalgae species that produce high amounts of this PUFA.
Growth Responses to Light
Both species showed altered growth rates under different light conditions, reflecting their unique strategies for coping with environmental stress.
Molecular Insights
Transcriptomics showed that these species respond differently at the molecular level, with Nitzschia cf. biundulata down-regulating photosynthetic genes under high light, while Polarella glacialis up-regulates them.
Why It Matters & What's Next?
Changes in sea ice thickness and snow cover may lead to significant shifts in the Antarctic food web. Microalgae, the foundation of this ecosystem, are adapting in different ways—some increasing energy storage, others altering the types of nutrients they produce. These shifts could affect the availability of macronutrients for higher trophic levels, with cascading effects on the entire ecosystem.
More research is needed to understand how diverse microalgal communities will respond to these changes. Studying their adaptability is key to predicting the future of polar ecosystems in a warming world.
If you are interested in reading the full published research paper, you can find it here.
Image: Flow of fatty acids and other biomolecules through the Antarctic food web
The Team
Huge thanks to my PhD supervisors Kirsty Smith (Cawthron Institute), Ken Ryan (Victoria University of Wellington) and all the co-authors for their work on this project. Cawthron Institute: Matt Miller, John Pearman, Lesley Rhodes, Lucy Thompson, Sarah Challenger. Antarctic Research Centre - Te Puna Pātiotio: Dr Natalie Robinson. Cawthron Summer Student: Nicole Parnell
