Frozen Flow: Mobility of diatoms in ice

In the harsh environment of the Arctic, ice-trapped diatoms display remarkable, yet not fully understood, survival strategies. During our 45-day Arctic expedition aboard the RV Squiliak, we employ customized sub-zero cooled tracking microscopes to capture live imaging of ice diatoms in and atop ice - navigating a unique ecosystem. We find that these ice diatoms not only withstand subfreezing temperatures within the Arctic ice but also exhibit an astonishing ability to glide on it. Near freezing points, their mobility exceeds that of room-temperature diatoms by an order of magnitude. These diatoms present a notable shift in thermal response curves of mobility towards lower temperatures, underscoring evolutionary adaptations to the cold. We further develop frozen 'ice' microfluidic channels to emulate the brine network, the diatoms’ natural habitat in the ice. By comparing the activity and diffusivity of individual diatoms with their collective dynamics in these brine replicas, we demonstrate their complex interactions with the network topology of the ice environment. The dive into the microscopic world of ice diatoms enhances our understanding of life’s resilience and adaptability in extreme habitats, a critical insight given the swift changes in the polar regions due to global warming.