Family-level Niche Differentiation in Bacterial Communities Inhabiting Glacial Lakes in Rila Mountain, Bulgaria

Glacial lakes are harsh ecosystems harbouring unique microbiota. In this study, we investigated the distribution of bacterial families in the water and sediment of three glacial lakes located in Rila Mountain, Bulgaria. Our results revealed high bacterial diversity and pronounced habitat preferences, as evidenced by the presence of 310 bacterial families with distinct distribution patterns between lake water and sediments. Taxonomic dissimilarities between water and sediment bacterial communities ranged from 74% to 100%. In general, water communities exhibited a common set of bacterial families with relatively consistent abundances across lakes, whereas sediment communities were more lake specific. Dominant families in sediments included Bacteroidaceae, Veillonellaceae, and Nitrosomonadaceae, whereas Comamonadaceae, Mycobacteriaceae, and Sporichthyaceae were prevalent in water samples. These findings highlight a clear bacterial partitioning between lake habitats and provide new insights for glacial lake conservation in a changing environment, particularly in the context of global warming.