Winter Metabolism in the High Arctic: A Multi-Habitat Metatranscriptomic Perspective

The cryosphere hosts diverse microbial communities adapted to steep temperature gradients, low water availability, and prolonged darkness. Despite evidence for sub-zero metabolic activity and long-term survival in ice cores, winter microbial ecology, particularly during the polar night, remains poorly constrained, with most studies focused on sunlit seasons. This has led to an incomplete, photosynthesis-centric view of polar ecosystem function, leaving open whether winter represents a period of dormancy or sustained metabolic activity. Here, we present the first multi-habitat metagenomic and metatranscriptomic study of High Arctic (79°N) microbial communities from glacier ice, snow, lake ice, and soils, sampled during mid-polar night. We examine transcriptional and translational activity to test for winter metabolic function, identify active taxa and pathways, and assess habitat-specific strategies. We evaluate how nutrient availability constrains winter metabolism and whether low-abundance taxa contribute disproportionately to activity. Our results indicate that cryospheric microbial communities maintain diverse metabolic functions throughout the polar night, redefining winter as a dynamic biogeochemical period with implications for Arctic ecosystem processes under changing climate.