Physiological Ecology of Antarctic Phytoplankton

Antarctic phytoplankton form the foundation of Southern Ocean food webs, driving carbon fixation, nutrient cycling and biogeochemical processes under extreme conditions. These microscopic algae endure prolonged periods of low light and subzero temperatures during the polar winter, and then respond rapidly to the return of sunlight in spring and summer. Key survival strategies include metabolic downregulation to a quiescent state, utilisation of internal energy reserves, maintenance of photosynthetic apparatus integrity and rapid activation of photoprotective processes on re-illumination. Physiological adaptations encompass flexible carbon allocation, shifts between respiratory and photosynthetic pathways, dynamic photophysiological responses to fluctuating light within and beneath sea ice, and modulation of pigment composition. Collectively, these traits determine bloom timing, magnitude and community composition, with consequences for higher trophic levels and carbon sequestration. In a warming climate, altered sea-ice dynamics, changes in light regimes and temperature shifts will exert strong selective pressures on phytoplankton physiology, with potential feedbacks on global carbon budgets and Southern Ocean ecosystems.

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Physiological Ecology of Antarctic Phytoplankton publication trend

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Technical terms

Quiescence: A reversible state of greatly reduced metabolic and transcriptional activity enabling survival during prolonged darkness.

Photophysiology: The study of how photosynthetic organisms regulate light absorption, energy conversion and photoprotection under changing light conditions.

Autophagy: A cellular process that degrades and recycles internal components to sustain energy balance during resource scarcity.

Polar night: A season in polar regions when the sun remains below the horizon for an extended period, resulting in continuous darkness.

Rubisco: Ribulose‐1,5‐bisphosphate carboxylase/oxygenase, the key enzyme catalysing carbon fixation in the Calvin cycle.

Non‐photochemical quenching (NPQ): A rapid mechanism by which excess absorbed light energy is dissipated as heat to protect photosynthetic systems from photodamage.

References

1. Hypometabolism to survive the long polar night and subsequent successful return to light in the diatom Fragilariopsis cylindrus. New Phytologist (2023).
2. Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity. Frontiers in Plant Science (2024).
3. Photosynthetic processes in Antarctic sea ice during the spring melt. Limnology and Oceanography (2024).