title: Light-dependent microbial metabolisms drive carbon fluxes on glacier surfaces.
abstract: Biological processes on glacier surfaces affect glacier reflectance, influence surface energy budget and glacier response to climate warming, and determine glacier carbon exchange with the atmosphere. Currently, carbon balance of supraglacial environment is assessed as the balance between the activity of oxygenic phototrophs and the respiration rate of heterotrophic organisms. Here we present a metagenomic analysis of tiny wind-blown supraglacial sediment (cryoconite) from Baltoro (Pakistani Karakoram) and Forni (Italian Alps) glaciers, providing evidence for the occurrence in these environments of different and previously neglected metabolic pathways. Indeed, we observed high abundance of heterotrophic anoxygenic phototrophs, suggesting that light might directly supplement the energy demand of some bacterial strains allowing them to use as carbon source organic molecules, which otherwise would be respired. Furthermore, data suggest that CO2could be produced also by microbiologically mediated oxidation of CO, which may be produced by photodegradation of organic matter.
authors.affiliation: Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Franzetti
authors.affiliation: Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy.
authors.forename: Ilario
authors.initials: I
authors.lastname: Tagliaferri
authors.affiliation: Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy.
authors.forename: Isabella
authors.initials: I
authors.lastname: Gandolfi
authors.affiliation: Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Bestetti
authors.affiliation: "A. Desio" Department of Earth Sciences, Università degli Studi di Milano, Milano, Italy.
authors.forename: Umberto
authors.initials: U
authors.lastname: Minora
authors.affiliation: Bavarian Academy of Sciences and Humanities, Munich, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mayer
authors.affiliation: "A. Desio" Department of Earth Sciences, Università degli Studi di Milano, Milano, Italy.
authors.forename: Roberto S
authors.initials: RS
authors.lastname: Azzoni
authors.affiliation: "A. Desio" Department of Earth Sciences, Università degli Studi di Milano, Milano, Italy.
authors.forename: Guglielmina
authors.initials: G
authors.lastname: Diolaiuti
authors.affiliation: "A. Desio" Department of Earth Sciences, Università degli Studi di Milano, Milano, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Smiraglia
authors.affiliation: Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ambrosini
mesh_terms: D001419:Bacteria / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism* / Q000528:radiation effects*; D002244:Carbon / Q000378:metabolism*; D057486:Carbon Cycle; D002980:Climate; D046448:Ice Cover / Q000382:microbiology*; D008027:Light
chemical_list: D002244:Carbon