Bacterial divergence among the interconnected habitats of a High Arctic Lake

Climate warming is likely to increase the physical connectivity of ecosystems with their surroundings. For Arctic lakes, increasing meltwater and precipitation may enhance the inputs of nutrients, organic matter and microorganisms from their catchments, and the increasingly ice-free, open-water conditions of the Arctic Ocean may favor increased inputs of marine aerosols, including microbiota. This study therefore aimed to determine how changing connectivity to terrestrial and marine habitats may affect the dispersal, sorting, and establishment of bacterial communities in a coastal High Arctic lake. Three habitats in this model system were sampled for ice, water, and snow: the lake, inflowing water tracks over permafrost soils, and an adjacent ice-dammed bay connected to the Arctic Ocean. Lake water chemistry confirmed the hydrological connection between the lake and terrestrial habitats, with the lake fed by terrestrial carbon sources via snow and groundwater run-off. Sequencing of 16S rDNA and rRNA showed evidence of a small marine and terrestrial influence on the lake, but few bacterial phylotypes were common to all three connected habitats. These results imply ongoing strong environmental filtering by habitat type, despite the apparent and potentially rising connectivity, and provide an example of bacterial resilience in a region of rapid climate change.