Overview: Arctic ice diatoms and ice gliding
In the harsh Arctic environment, ice-dwelling diatoms endure extreme cold, variable brine pockets, and constrained liquid pathways within the ice. Our study provides direct cellular observations of these microorganisms embedded in ice and reveals a previously undocumented ice-gliding ability that helps them navigate the ice matrix to reach light and nutrients. The behavior is distinct from temperate diatoms, which lack this motility under similar conditions. The work, published in PNAS via PubMed (open access), and of interest to astrobiology, highlights how life adapts to extreme solid matrices.
Methods: From ice-incubated cells to thermo-hydrodynamic models
We combined direct in-ice observations of diatom cells with cryogenic imaging and micro-scale tracking to quantify locomotion. In parallel, thermo-hydrodynamic models were developed to understand how energy efficiency, mucilage properties, and ice microstructure interact to permit movement at subzero temperatures. The modeling helps explain why ice gliding emerges at all and why temperate relatives do not show the same method of motility under the same conditions.
Findings: Ice gliding at record-low temperatures
Arctic diatoms deploy a thin mucilage layer that mediates contact with micro-channels and brine films within the ice. The mucilage reduces friction and the cell modulates propulsion to conserve energy, enabling glide along the ice surface. This mechanism allows cells to exploit illuminated pockets and nutrient-rich brine channels that exist in the ice, even when ambient temperatures plummet toward -5°C or lower. Our observations document a record-low temperature limit for motility in a eukaryotic cell, a milestone for microbial physics.
Why temperate diatoms lack this trait
In temperate regions, ice structure and brine distribution differ, and the same mucilage–ice interface is not conducive to subzero locomotion. The Arctic diatoms appear specially adapted to harness brine channels and the rheology of mucilage for sustainable movement in frozen habitats.
Mechanisms: Energy efficiency and mucilage optimization
The thermo-hydrodynamic framework shows two complementary strategies: first, minimizing propulsion costs through streamlined gliding and optimal contact with brine films; second, tuning mucilage composition to balance viscosity, elasticity, and adhesion. Together, these features enable conduction through the ice matrix while maintaining cellular integrity and photosynthetic productivity in low light.
Ecological and astrobiological implications
By enabling motility within ice, ice gliding diatoms influence primary production, nutrient cycling, and albedo effects in polar ecosystems. Their mobility within the ice can affect particle resuspension, diffusion of gases, and vertical fluxes of organic matter. Moreover, the demonstrated physical strategies offer a useful analog for possible life in icy worlds, informing astrobiology about how microorganisms could navigate solid matrices beyond Earth.
Conclusion
Ice gliding diatoms push the boundaries of eukaryotic motility and redefine how we conceptualize life at the cold edge. Through direct cellular observations and thermo-hydrodynamic modeling, this work illuminates the resilience of polar phytoplankton and provides a foundation for predicting how Arctic and Antarctic ecosystems will respond to ongoing climate change.
