Identification and Global Distribution of a Core Microbiome From High‐Arctic Lakes

Arctic lakes are sentinels of climate change, yet their microbial community structure and functioning remain poorly understood. This study analysed the genetic content of clear-water Arctic lakes and their surroundings using high-throughput amplicon sequencing of the 16S rRNA gene to identify their core microbiome and its contribution to the overall taxonomy pool. To assess geographical constraints and oligotrophic conditions, these results were compared with a latitudinally diverse multi-basin oligotrophic lake in a temperate climate. Arctic and temperate lakes exhibited different assemblages, but both showed similar transitional gradients of microbial community composition from upstream soils/inlets through the lake system to the outlet, driven mainly by the dissolved organic matter (DOM) characteristics. Distinct core microbiomes were identified for temperate and Arctic lakes, with Arctic lakes appearing more diverse. A limited shared core microbiome was observed between the two regions, composed mostly of typical freshwater bacteria. While core taxa identities differed between regions, most exhibited characteristics of generalist bacteria with a strong global presence. These results provide key insights into the structure of remote high Arctic lakes, contributing to our understanding of aquatic microbial ecology in a transitioning Arctic and identifying microbial communities and individual taxa of interest for further study on oligotrophy.