The structure, biological activity and biogeochemistry of cryoconite aggregates upon an Arctic valley glacier: Longyearbreen, Svalbard

Hodson, Andy; Cameron, Karen A.; Bøggild, Carl Egede; Irvine‐Fynn, Tristram; Langford, Harry; Pearce, David A.; Banwart, Steven A.

doi:10.3189/002214310791968403

Cited by 139 publications

(205 citation statements)

References 30 publications

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“…Takeuchi (2002) found C/N mass ratios between 9 and 14 (mostly around 11) for different cryoconites of nine glaciers from the Himalaya, Tibet, and the Arctic. In addition, Hodson et al (2010b) found a C/N mass ratio of 13 ± 1 for cryoconite from Longyearbreen, a valley glacier in Svalbard.…”

Section: Discussionmentioning

confidence: 99%

“…Takeuchi (2002) found that the amount of dark coloured organic substances, possibly the residue of bacterial decomposition of organic matter, determines the optical characteristics of the cryoconite. In addition, the aggregation of dark particles and organic debris by extracellular polymeric substances affects the light absorbency of the cryoconite (Hodson et al, 2010b). Uetake et al (2010) found that a higher biovolume and differences in species composition account for the darker surface of Russell glacier compared to the Qaanaaq Glacier, both in West Greenland.…”

Section: Introductionmentioning

confidence: 99%

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Dust from the dark region in the western ablation zone of the Greenland ice sheet

et al. 2011

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Abstract.A dark region tens of kilometres wide is located in the western ablation zone of the Greenland ice sheet. The dark appearance is caused by higher amounts of dust relative to the brighter surroundings. This dust has either been deposited recently or was brought to the surface by melting of outcropping ice. Because the resulting lower albedos may have a significant effect on melt rates, we analysed surface dust on the ice, also called cryoconite, from locations in the dark region as well as locations from the brighter surrounding reference ice with microscopic and geochemical techniques to unravel its composition and origin. We find that (part of) the material is derived from the outcropping ice, and that there is little difference between dust from the dark region and from the reference ice. The dust from the dark region seems enriched in trace and minor elements that are mainly present in the current atmosphere because of anthropogenic activity. This enrichment is probably caused by higher precipitation and lower melt rates in the dark region relative to the ice marginal zone. The rare earth elemental ratios of the investigated material are approximately the same for all sites and resemble Earth's average crust composition. Therefore, the cryoconite probably does not contain volcanic material. The mineralogical composition of the dust excludes Asian deserts, which are often found as provenance for glacial dust in ice cores, as source regions. Consequently, the outcropping dust likely has a more local origin. Finally, we find cyanobacteria and algae in the cryoconite. Total Organic Carbon accounts for up to 5 weight per cent Correspondence to: I. G. M. Wientjes (i.g.m.wientjes@uu.nl) of the cryoconite from the dark region, whereas dust samples from the reference ice contain only 1 % or less. This organic material is likely formed in situ. Because of their high light absorbency, cyanobacteria and the organic material they produce contribute significantly to the low albedo of the dark region.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dust from the dark region in the western ablation zone of the Greenland ice sheet

et al. 2011

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“…For example, dispersed cryoconite can contribute up to half the total cryoconite coverage on Arctic valley glaciers, and may have the potential to be biologically active . Third, there may be significant additional loss of TIN (aq) via microbial denitrification, perhaps by microbes located within the anoxic interior of cryoconite granules (Hodson et al, 2010a).…”

Section: Active Nitrogen Fixation In the Marginal And Glacier Zonesmentioning

confidence: 99%

Microbial nitrogen cycling on the Greenland Ice Sheet

et al. 2012

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Abstract. Nitrogen inputs and microbial nitrogen cycling were investigated along a 79 km transect into the Greenland Ice Sheet (GrIS) during the main ablation season in summer 2010. The depletion of dissolved nitrate and production of ammonium (relative to icemelt) in cryoconite holes on Leverett Glacier, within 7.5 km of the ice sheet margin, suggested microbial uptake and ammonification respectively. Positive in situ acetylene assays indicated nitrogen fixation both in a debris-rich 100 m marginal zone and up to 5.7 km upslope on Leverett Glacier (with rates up to 16.3 µmoles C 2 H 4 m −2 day −1 ). No positive acetylene assays were detected > 5.7 km into the ablation zone of the ice sheet. Potential nitrogen fixation only occurred when concentrations of dissolved and sediment-bound inorganic nitrogen were undetectable. Estimates of nitrogen fluxes onto the transect suggest that nitrogen fixation is likely of minor importance to the overall nitrogen budget of Leverett Glacier and of negligible importance to the nitrogen budget on the main ice sheet itself. Nitrogen fixation is however potentially important as a source of nitrogen to microbial communities in the debrisrich marginal zone close to the terminus of the glacier, where nitrogen fixation may aid the colonization of subglacial and moraine-derived debris.

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“…Considering these factors, it is important to identify glacier-wide variability in carbohydrate production, as carbohydrates may control the formation of aggregates upon glaciers and ice sheets (e.g. Hodson et al, 2010;Stibal et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

A spatial investigation of the environmental controls over cryoconite aggregation on Longyearbreen glacier, Svalbard

et al. 2014

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Abstract.A cryoconite granule is a near-spherical aggregation of biota and abiotic particles found upon glacier surfaces. Recently, microstructural studies have revealed that photosynthetic microorganisms and extracellular polymeric substances (EPS) are omnipresent within cryoconite granules and have suggested their importance as biological "forming factors". To assess these forming factors, and their biological control over aggregate size and stability, across a typical Arctic valley glacier surface, a suite of rapid, spectrophotometric, microplate methods were utilised. Subsequent spatial mapping of these data revealed distinct patterns. Labile carbohydrates were found to increase up-glacier, suggestive of EPS production for cryoprotection and nutrient assimilation. Conversely, pigment concentrations were found to increase towards the glacier terminus and valley sides, suggestive of allochthonous input, a general reduction in physical disturbance and of the build-up of photosynthetic pigments and less labile cyanobacterial sheath material. Aggregate size was found to increase towards the glacier edges, linked to the input of particulate matter from the valley sides, and to broadly increase down-glacier, in the same way as pigment concentrations. Statistical analyses of transect data revealed that the photoautotrophic count and carbohydratechlorophyll ratio of the cryoconite sampled could explain 83 % of the measured variation in aggregate size and stability. Considering solely aggregate size, the number and length of photoautotrophic filaments could explain 92 % of the variation in this parameter. These findings demonstrate the twodimensional distribution of key biological controls upon cryoconite aggregation for the first time, and highlight the importance of filamentous cyanobacteria and EPS production to the development of stable cryoconite granules.

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The structure, biological activity and biogeochemistry of cryoconite aggregates upon an Arctic valley glacier: Longyearbreen, Svalbard

Cited by 139 publications

References 30 publications

Dust from the dark region in the western ablation zone of the Greenland ice sheet

Dust from the dark region in the western ablation zone of the Greenland ice sheet

Microbial nitrogen cycling on the Greenland Ice Sheet

A spatial investigation of the environmental controls over cryoconite aggregation on Longyearbreen glacier, Svalbard

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