The study investigates the impact of frazil ice on biogeochemical processes in the Lena River during winter. It highlights how frazil ice formation creates microzones that extend reaction times for solutes, leading to significant changes in silicon isotope composition and Ge/Si ratios. These microzones facilitate microbially mediated biogeochemical processes, particularly nitrogen cycling, under ice-covered conditions. The research underscores the potential implications of climate change, as shorter river ice durations could alter nutrient processing and greenhouse gas emissions in Arctic river systems.