Distinct bacterial community structures with abundant sulfur metabolism prevalently found among different sea ice types in the Central Arctic Ocean

The rapid decline of sea ice in the relatively understudied Central Arctic Ocean has a significant impact on bacterial biodiversity and the ecological functions they support. We investigated the bacterial community composition and their associated metabolic functions from three geographically distinct sea ice floes at the North Pole, western Amundsen, and western Nansen basin. We resolved the bacterial community diversity inhabiting the sea ice habitat with species-level precision using a long-read amplicon sequencing approach. The study revealed 10 unique bacterial phyla, comprising 114 genera and 62 species, mainly belonging to Bacteroidota, Proteobacteria, and Cyanobacteria, which were found to be prevalent across the three ice stations. We relate community diversity to different physicochemical properties of sea ice, including ice age and ice floe origin, through sea ice back-trajectory analysis. We inferred key microbially mediated metabolic functions associated with carbon, sulfur, and nitrogen cycling processes among the three sites through genome-resolved metagenomics. The data suggests the prevalence of sulfur cycling-associated processes (assimilatory & dissimilatory sulfur metabolism) in the sea ice habitat. The heterotrophic bacterial groups were found to be dominant and significantly contribute to nutrient recycling and complex organic matter degradation during the summer sea ice melt season. Overall, our findings revealed that distinct differences were observed in bacterial community diversity and associated ecological functions correlating with sea ice type, origin and habitat characteristics in the Central Arctic Ocean.