Nutrient cycling in supraglacial environments of the Dark Zone of the Greenland Ice Sheet

Holland, Alexandra; Williamson, Christopher; Sgouridis, Fotis; Tedstone, Andrew; McCutcheon, Jenine; Cook, Joseph M.; Poniecka, Ewa; Yallop, Marian L.; Tranter, Martyn; Anesio, Alexandre M.

doi:10.5194/bg-2019-69

Cited by 3 publications

(5 citation statements)

References 52 publications

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“…3d ). The ratio of TOC:N:P org measured in site 4 H bio particulates ranged between 690:48:1 and 2615:196:1, which mirrors the dissolved organic nutrient ratios reported in Holland, et al 19 (DOC:DON:DOP = 2017:117:1). In the present study, we find that as the concentration of solid-phase P min increases, the C:N:P ratio decreases and approaches the ideal Redfield C:N:P ratio.…”

Section: Resultssupporting

confidence: 83%

“…This accounts for the lower P min concentration at sites hosting more prolific algal blooms (4 and 5), where a higher proportion of P min has been transformed into P org through bioweathering and algal biomass accumulation. Glacier algal productivity outstrips that of associated heterotrophic assemblages 23 , and likely drives recycling of solubilized P. Site 4a H bio and DCC ice contained three to four times more dissolved P than clean ice or supraglacial stream water (Supplementary Table 8 ), substantiating claims that P is retained in surface ice habitats 19 .…”

Section: Resultsmentioning

confidence: 56%

“…Such a storage mechanism would be beneficial for glacier algae inhabiting the oligotrophic surface ice environments of the GrIS Dark Zone. The lack of a photophysiological response to the addition of nitrate or ammonium suggests that glacier algae are not limited by N. Although our measurements of dissolved inorganic N in surface ice and snow samples were low or below detection limit (Supplementary Table 8 ), inorganic and organic N have been documented in H bio ice habitats in concentrations of 1.0 and 14 µM, respectively 19 , indicating that N is available in the system.

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Section: Resultsmentioning

confidence: 72%

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Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

et al. 2021

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Melting of the Greenland Ice Sheet is a leading cause of land-ice mass loss and cryosphere-attributed sea level rise. Blooms of pigmented glacier ice algae lower ice albedo and accelerate surface melting in the ice sheet’s southwest sector. Although glacier ice algae cause up to 13% of the surface melting in this region, the controls on bloom development remain poorly understood. Here we show a direct link between mineral phosphorus in surface ice and glacier ice algae biomass through the quantification of solid and fluid phase phosphorus reservoirs in surface habitats across the southwest ablation zone of the ice sheet. We demonstrate that nutrients from mineral dust likely drive glacier ice algal growth, and thereby identify mineral dust as a secondary control on ice sheet melting.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 56%

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Section: Resultsmentioning

confidence: 72%

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Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

et al. 2021

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“…The negative influence of phosphorous limitation on zooplankton and benthic grazers is well known in freshwater systems (Hart & Robinson, 1990; Urabe et al ., 1997). Glaciers are very likely ecosystems where organisms are limited by dissolved phosphorous availability (Holland et al ., 2019), which is a crucial biogenic element. This, in turn, may limit the presence of other taxa in cryoconite holes, but to our knowledge nematodes are not more sensitive to the resulting effects on the food web of phosphorous limitation than are other microinvertebrates.…”

Section: Discussionmentioning

confidence: 99%

A hole in the nematosphere: tardigrades and rotifers dominate the cryoconite hole environment, whereas nematodes are missing

et al. 2020

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The worldwide distribution of microinvertebrates on glaciers, the coldest biome, is poorly known. Owing to their tolerance to hostile conditions, small size and dispersal abilities, nematodes, tardigrades and rotifers are considered cosmopolitan and together inhabit various ecosystems. In this study, we investigated their global distribution in cryoconite holes – a type of freshwater reservoir forming directly in the glacial ice that creates biodiversity hotspots on glaciers. We analysed cryoconite samples (using classical microscopic observations and environmental DNA metabarcoding) from 42 glaciers located around the world (the Arctic, Subarctic, Scandinavia, the Alps, the Caucasus, Siberia, Central Asia, Africa, South America and Antarctica), as well as using literature data. Samples from Antarctic, Karakoram and the Alps were analysed using next‐generation sequencing (NGS) and classical observations under microscopes, while all other samples were analysed by microscope alone. Three general outcomes were found: (1) tardigrades and rotifers represented the most common invertebrates in cryoconite holes; (2) tardigrades and rotifers often coexisted together, with one or the other dominating, but the dominant taxon varied by region or by glacier; (3) nematodes – the most abundant, hyperdiverse and widespread metazoans on Earth, including in environments surrounding and seeding glacial surfaces – were consistently absent from cryoconite holes. Despite the general similarity of environmental conditions in cryoconite holes, the distribution of tardigrades and rotifers differed among glaciers, but not in any predictable way, suggesting that their distribution mostly depended on the random dispersal, extreme changes of supraglacial zone or competition. Although nematodes have been found in supraglacial habitats, cryoconite hole environments seem not to provide the necessary conditions for their growth and reproduction. Lack of physiological adaptations to permanently low temperatures (~0°C) and competition for different food resources in the cryoconite hole environment may explain the absence of nematodes in cryoconite holes.

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“…We suggest that this may reflect nutrient limitation and competition between microbial communities. During an algal bloom, the sheer biomass of algal cells likely intercepts and retains the majority of available nutrients resulting in severe nutrient limitation for bacteria, particularly toward the end of the season, where inputs from snowmelt are reduced (Holland et al, in press). Nutrient limited conditions may also alter the quality and composition of DOC excreted by glacier algae (Dodds, 2010) resulting in less bioavailable species and a subsequent reduction in BP.…”

Section: Discussionmentioning

confidence: 99%

Bacterial Dynamics in Supraglacial Habitats of the Greenland Ice Sheet

et al. 2019

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Current research into bacterial dynamics on the Greenland Ice Sheet (GrIS) is biased toward cryoconite holes, despite this habitat covering less than 8% of the ablation (melt) zone surface. In contrast, the expansive surface ice, which supports wide-spread Streptophyte micro-algal blooms thought to enhance surface melt, has been relatively neglected. This study aims to understand variability in bacterial abundance and production across an ablation season on the GrIS, in relation to micro-algal bloom dynamics. Bacterial abundance reached 3.3 ± 0.3 × 10 5 cells ml −1 in surface ice and was significantly linearly related to algal abundances during the middle and late ablation periods ( R 2 = 0.62, p < 0.05; R 2 = 0.78, p < 0.001). Bacterial production (BP) of 0.03–0.6 μg C L −1 h −1 was observed in surface ice and increased in concert with glacier algal abundances, indicating that heterotrophic bacteria consume algal-derived dissolved organic carbon. However, BP remained at least 28 times lower than net primary production, indicating inefficient carbon cycling by heterotrophic bacteria and net accumulation of carbon in surface ice throughout the ablation season. Across the supraglacial environment, cryoconite sediment BP was at least four times greater than surface ice, confirming that cryoconite holes are the true “hot spots” of heterotrophic bacterial activity.

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Nutrient cycling in supraglacial environments of the Dark Zone of the Greenland Ice Sheet

Cited by 3 publications

References 52 publications

Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

A hole in the nematosphere: tardigrades and rotifers dominate the cryoconite hole environment, whereas nematodes are missing

Bacterial Dynamics in Supraglacial Habitats of the Greenland Ice Sheet

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