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Metabolome-mediated biocryomorphic evolution promotes carbon fixation in Greenlandic cryoconite holesCook, J. M.; Edwards, Arwyn; Bulling, Mark T.; Mur, Luis A .J.; Cook, Sophie; Gokul, Jarishma K.; Cameron, Karen A.; Sweet, Michael J.; Irvine-Fynn, Tristram D. L.; University of Derby; et al. (2016-04-26)Microbial photoautotrophs on glaciers engineer the formation of granular microbial-mineral aggregate stermed cryoconite which accelerate ice melt, creating quasi-cylindrical pits called ‘cryoconite holes’. Theseact as biogeochemical reactors on the ice surface and provide habitats for remarkably active and diverse microbiota. Evolution of cryoconite holes towards an equilibrium depth is well known, yet inter-actions between microbial activity and hole morphology are currently weakly addressed. Here, we experimentally perturbed the depths and diameters of cryoconite holes on the Greenland Ice Sheet.Cryoconite holes responded by sensitively adjusting their shapes in three dimensions (‘biocryomorphic evolution’) thus maintaining favourable conditions for net autotrophy at the hole floors. Non-targeted metabolomics reveals concomitant shifts in cyclicAMP and fucose metabolism consistent with photo-taxis and extracellular polymer synthesis indicating metabolomic-level granular changes in response to perturbation. We present a conceptual model explain-ing this process and suggest that it results in remarkably robust net autotrophy on the Greenland Ice Sheet. We also describe observations of cryocon-ite migrating away from shade, implying a degree of self-regulation of carbon budgets over mesoscales. Since cryoconite is a microbe-mineral aggregate, itappears that microbial processes themselves formand maintain stable autotrophic habitats on the sur-face of the Greenland ice sheet.
Topographic shading influences cryoconite morphodynamics and carbon exchange.Cook, J. M.; Sweet, Michael J.; Cavalli, Ottavia; Taggart, Angus; Edwards, Arwyn; University of Derby; Aberystwyth University; University of Sheffield (Taylor and Francis, 2018-03-13)Cryoconite holes are the most active and diverse microbial habitats on glacier and ice-sheet surfaces. In this article the authors demonstrate that the shape of cryoconite holes varies depending on ice-surface topography and that this has implications for the carbon cycling regime within. Net ecosystem production is shown to be controlled primarily by sediment thickness within holes. The authors show that irregular hole shapes are indicative of hole migration away from topographic shade, which promotes carbon fixation at the mesoscale on ice surfaces. A cellular automaton is used in conjunction with sediment-delivery experiments to show that migration is the result of simple sediment transfer processes, implying a relationship between ice-surface evolution and cryoconite biogeochemistry that has not previously been examined.