Bacterial community diversity in sparse debris and cryoconite holes on nearby glaciers

Supraglacial ecosystems concentrate their microbial communities mostly in cryoconite holes, small pits full of 11 melting water with a sediment on the bottom. The geographical differences of their bacterial communities (among 12 glaciers) are quite ascertained, especially at large scale. Furthermore, so far no data are available to confirm the 13 hypothesis that bacterial communities inhabiting cryoconite holes are different from those that can be found in the 14 sparse debris (the dry debris that is not immersed in the melting water), especially considering that the sparse 15 debris can form cryoconite holes and vice versa. In this study we characterized bacterial communities of the sparse 16 debris of three different glaciers belonging to a quite restricted area (maximum distance < 10 km) of the Ortles 17 Cevedale Group (Italian Alps) and confirmed that bacterial communities differ among different glaciers, but not 18 according to their geographic distance. Indeed, lithology seems to have an effect on their composition. 19 Furthermore, we found that bacterial communities of the sparse debris are significantly different from those 20 inhabiting cryoconite holes.