title: Photophysiology and albedo-changing potential of the ice algal community on the surface of the Greenland ice sheet.
abstract: Darkening of parts of the Greenland ice sheet surface during the summer months leads to reduced albedo and increased melting. Here we show that heavily pigmented, actively photosynthesising microalgae and cyanobacteria are present on the bare ice. We demonstrate the widespread abundance of green algae in the Zygnematophyceae on the ice sheet surface in Southwest Greenland. Photophysiological measurements (variable chlorophyll fluorescence) indicate that the ice algae likely use screening mechanisms to downregulate photosynthesis when exposed to high intensities of visible and ultraviolet radiation, rather than non-photochemical quenching or cell movement. Using imaging microspectrophotometry, we demonstrate that intact cells and filaments absorb light with characteristic spectral profiles across ultraviolet and visible wavelengths, whereas inorganic dust particles typical for these areas display little absorption. Our results indicate that the phototrophic community growing directly on the bare ice, through their photophysiology, most likely have an important role in changing albedo, and subsequently may impact melt rates on the ice sheet.
authors.affiliation: School of Biological Sciences, University of Bristol, Bristol, UK. Marian.Yallop@bristol.ac.uk
authors.forename: Marian L
authors.initials: ML
authors.lastname: Yallop
authors.forename: Alexandre M
authors.initials: AM
authors.lastname: Anesio
authors.forename: Rupert G
authors.initials: RG
authors.lastname: Perkins
authors.forename: Joseph
authors.initials: J
authors.lastname: Cook
authors.forename: Jon
authors.initials: J
authors.lastname: Telling
authors.forename: Daniel
authors.initials: D
authors.lastname: Fagan
authors.forename: James
authors.initials: J
authors.lastname: MacFarlane
authors.forename: Marek
authors.initials: M
authors.lastname: Stibal
authors.forename: Gary
authors.initials: G
authors.lastname: Barker
authors.forename: Chris
authors.initials: C
authors.lastname: Bellas
authors.forename: Andy
authors.initials: A
authors.lastname: Hodson
authors.forename: Martyn
authors.initials: M
authors.lastname: Tranter
authors.forename: Jemma
authors.initials: J
authors.lastname: Wadham
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Roberts
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis; D002734:Chlorophyll / Q000032:analysis; D000458:Cyanobacteria / Q000502:physiology*; D005615:Freezing; D006116:Greenland; D046448:Ice Cover / Q000382:microbiology*; D058086:Microalgae / Q000502:physiology*; D015591:Microspectrophotometry; D010788:Photosynthesis; D012621:Seasons
chemical_list: D002247:Carbon Isotopes; D002734:Chlorophyll