Fig 1.
a) Position of the Forni Glacier in Italy; b) composite photograph obtained by an unmanned aerial vehicle (UAV) of the tongue of the Forni glacier with the glacier forefield. Symbols indicate the position where we collected samples on the supraglacial moraine and on the glacier forefield. The star denote the position of an automatic weather station (AWS) on the glacier surface; c) detailed UAV photograph of the study area. Position of each cryoconite hole is shown. Different symbols denote holes with overlapping positions sampled at different months. The dashed line delimits the study area.
Fig 2.
Difference in alpha and beta diversity among cryoconite holes and ice-marginal environments.
a) Barplot of the number of OTUs at cryoconite holes and ice-marginal environments. Asterisks denote significant differences at post-hoc tests (*** = P < 0.001). b) Biplot of first and second components from CCA of bacterial communities in cryoconite holes, moraines, dirt cone and glacier forefield. Each symbol represents the bacterial community in one sample. Different symbols represent different environments and polygons include samples at each environment (cryoconite holes = dots and solid line, moraines = triangles and dotted line, dirt cone = diamonds and dashed-dotted line, glacier forefield = squares and dashed line,). Letters denote the centroid of bacterial communities at each environment (C = cryoconite holes, D = dirt cone, M = moraines, F = glacier forefield). The amount of variance explained by each axis is shown as well as significance of each axis as assessed by a randomization test (*** = P < 0.001).
Fig 3.
Network showing significant (PFDR < 0.05) associations between indicator OTUs and specific habitats (diamonds; C = cryoconite holes, D = dirt cone, M = moraines, F = glacier forefield), or groups of habitats. OTUs (circles) were grouped according to classes. The most abundant classes are shown with different colours and circle size indicates the number of OTUs of each class (see legend in the graph). OTUs were connected to the environments to which they were significantly associated according to the Indicator Species analysis. In order to simplify the network, only OTUs associated to single habitats or to groups of habitats including the cryoconite were represented. Inserts show pictures of sampled habitats.