Supraglacial microbial communities of Forni glacier

Glaciers are ecosystems hosting active communities, but the knowledge of the ecological processes that occur in these extreme environments is fragmented. More studies on the biodiversity, trophic networks and energy fluxes on glaciers are needed to better appreciate their ecological contribution on a global scale. This work shows the microbiological results of a research project that aims at describing the biodiversity and the ecological webs of the Forni Glacier (Stelvio National Park, Central Italian Alps). Samples were collected over two consecutive years from different supraglacial habitats, including cryoconite holes (i.e. small ponds full of melting water with a fine-grained sediment on the bottom), supraglacial sediment, bediere (i.e. supraglacial stream water), snow, dirt cones, moraines and ice. Englacial sediment samples and subglacial sediment samples were also collected on the second year. Microbial communities including bacteria, algae and fungi, were characterized by amplicon sequencing for all samples.  The most abundant bacterial phyla resulted to be Pseudomonadota, Bacteroidota, Actinomycetota and Cyanobacteria, the most abundant fungal classes resulted to be Microbotryomycetes, Dothideomycetes, Leotiomycetes, Lecanoromycetes and Agaricomycetes, and the most abundant algal phyla resulted to be Chrysocapsales, Prasiolales and Chlamydomonadales. All microbial communities resulted to change according to habitat and sampling time. Finally, the microbiome of "ice fleas" (ice-dwelling glacial springtails) was also characterized from individuals collected on the second year, as they play a crucial role in connecting microbial communities with higher trophic levels. Results showed that all microbiome samples shared only one bacterial Amplicon Sequence Variant (ASV) of the family Comamonadaceae which may be involved in iron oxidation, which has high concentrations on Forni glacier. Overall, these results provide a good description of the microbial biodiversity of the supraglacial environment of Forni glacier and a first insight into the trophic network.  Such studies are essential for properly understanding the dynamics of such a threatened ecosystem.