One of the main concerns about the Arctic Ocean has been the changing sea ice regime with a reduction in the summer sea ice extent and a shift in dominance from thicker, perennial multiyear ice towards thinner, first-year ice. As the dietary basis of marine food webs and central players of biogeochemical cycles, microbial communities play an irreplaceable role when evaluating the ecological impact of the Arctic’s thinner ice regime. During the Norwegian young sea Ice cruise 2015 (N-ICE2015), that took place in drifting pack ice north of Svalbard between January-June 2015, seawater was collected, at 5, 20 or 50, 250 m depth in 9th March, 27th April and 16th June, together with physical and biogeochemical data. Through the massively parallel sequencing of environmental DNA (metagenomics) we expect to get a snapshot of the Arctic’s microbiome structure, key functions and dynamic through the dark-light transition.