Microorganisms in the Accreted Ice of Lake Vostok, Antarctica

Karl, David M.; Bird, David F.; Björkman, Karin M.; Houlihan, T.; Shackelford, Rachel; Tupas, Luis M.

doi:10.1126/science.286.5447.2144

Cited by 337 publications

(205 citation statements)

References 29 publications

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“…This, in turn, reflects that respiration and growth are the summation of numerous, discrete enzymatic pathways, all of which respond differently to temperature (Clarke, 1991). Similar, carbon-quality effects at a low temperature have previously been demonstrated in a study examining microbial activity in the accreted ice of Lake Vostok: melt water samples enriched with qualitatively different carbon substrates and incubated at 1 1C revealed clear substrate-identity effects on mineralization but not growth; substrate effects on growth were, however, apparent when incubated at 23 1C (Karl et al, 1999). The recent observation that the effects of food stoichiometry on growth rate diminish as an organism approaches its lower thermal limit (Persson et al, 2011) lends further support to our data interpretation.…”

Section: Discussionmentioning

confidence: 70%

Resource quality affects carbon cycling in deep-sea sediments

et al. 2012

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Deep-sea sediments cover B70% of Earth's surface and represent the largest interface between the biological and geological cycles of carbon. Diatoms and zooplankton faecal pellets naturally transport organic material from the upper ocean down to the deep seabed, but how these qualitatively different substrates affect the fate of carbon in this permanently cold environment remains unknown. We added equal quantities of 13 C-labelled diatoms and faecal pellets to a cold water (À0.7 1C) sediment community retrieved from 1080 m in the Faroe-Shetland Channel, Northeast Atlantic, and quantified carbon mineralization and uptake by the resident bacteria and macrofauna over a 6-day period. High-quality, diatom-derived carbon was mineralized 4300% faster than that from low-quality faecal pellets, demonstrating that qualitative differences in organic matter drive major changes in the residence time of carbon at the deep seabed. Benthic bacteria dominated biological carbon processing in our experiments, yet showed no evidence of resource qualitylimited growth; they displayed lower growth efficiencies when respiring diatoms. These effects were consistent in contrasting months. We contend that respiration and growth in the resident sediment microbial communities were substrate and temperature limited, respectively. Our study has important implications for how future changes in the biochemical makeup of exported organic matter will affect the balance between mineralization and sequestration of organic carbon in the largest ecosystem on Earth.

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Section: Discussionmentioning

confidence: 70%

Resource quality affects carbon cycling in deep-sea sediments

et al. 2012

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“…Surface water from Subglacial Lake Vostok, East Antarctica, which had accreted to the base of the ice sheet, was recovered during drilling of the Vostok ice core [15]. Samples of this material contained microbial cells and offered the first evidence for deep subsurface life in Antarctica [6,16,17]. A sediment core collected from under the Kamb Ice Stream (KIS), West Antarctica, which is due north of Whillans Ice Stream (WIS), was also shown to contain viable microbial cells [18].…”

Section: Antarctic Subglacial Lakes: An Underexplored Microbial Habitatmentioning

confidence: 99%

Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge

Mikucki

Lee

Ghosh

et al. 2016

Phil. Trans. R. Soc. A.

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Liquid water occurs below glaciers and ice sheets globally, enabling the existence of an array of aquatic microbial ecosystems. In Antarctica, large subglacial lakes are present beneath hundreds to thousands of metres of ice, and scientific interest in exploring these environments has escalated over the past decade. After years of planning, the first team of scientists and engineers cleanly accessed and retrieved pristine samples from a West Antarctic subglacial lake ecosystem in January 2013. This paper reviews the findings to date on Subglacial Lake Whillans and presents new supporting data on the carbon and energy metabolism of resident microbes. The analysis of water and sediments from the lake revealed a diverse microbial community composed of bacteria and archaea that are close relatives of species known to use reduced N, S or Fe and CH4 as energy sources. The water chemistry of Subglacial Lake Whillans was dominated by weathering products from silicate minerals with a minor influence from seawater. Contributions to water chemistry from microbial sulfide oxidation and carbonation reactions were supported by genomic data. Collectively, these results provide unequivocal evidence that subglacial environments in this region of West Antarctica host active microbial ecosystems that participate in subglacial biogeochemical cyclingauthorsversionPeer reviewe

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“…For the lower estimate, we assume that subglacial microbes have rates of metabolism in line with other parts [Price and Sowers, 2004;after Jakosky et al, 2003] (2360/2320) (A) (2170/2500) (B) (4200/480) (C) Lower estimate 10 À2 10 7 22 [Christner et al, 2003;Karl et al, 1999;Parkes et al, 1990] (42/À1) (A) (10/11) (B) (19/2) (C) a Assumptions are as follows: (1) Biogenic gas production can only occur in warm-based areas of the LIS and FIS. (2) Thirty percent of the LIS was warm-based on average for the first 75 ka of the last glacial; between the LGM (20 ka B.P.)…”

Section: Rates Of Carbon Turnovermentioning

confidence: 99%

Subglacial methanogenesis: A potential climatic amplifier?

Wadham

Tranter

Tulaczyk

et al. 2008

Global Biogeochemical Cycles

114

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[1] Subglacial environments are a previously neglected component of the Earth's global carbon cycle, a reflection of the view held until recently that they are dominated by abiotic and oxic conditions. Here we provide a realistic assessment of the theory that the basal regions of the ice sheets that formed over North America and Europe during glaciations were host to significant populations of anaerobic microorganisms, including methanogens, able to metabolize organic carbon sequestered during interglacials and overridden during Quaternary glacials. In doing so, we review the current evidence for subglacial methane release during deglaciation, estimate the size of the subglacial reservoir of organic carbon (SOC), and assess the amount of SOC available to subglacial microbes and the likely pathways and rates of carbon turnover. We then discuss the fate of subglacial methane and the potential impact of its release on atmospheric methane concentrations. We calculate that the SOC equates to 418-610 Pg C and includes carbon from terrestrial soils/vegetation, peatlands, lake, and marine sediments. The SOC that is potentially available for microbial conversion to methane is smaller than this estimate due to (1) glacial erosion, (2) accumulation of recalcitrant organic carbon compounds over time, (3) conversion to carbon dioxide by aerobic/anaerobic respiration, and (4) incomplete conversion of labile organic matter to methane. We estimate that the total SOC available for conversion to methane is 63 Pg C. Our estimates of methane production potentials span a wide range because of the current uncertainty surrounding subglacial metabolic rates. We believe, however, that there is a strong likelihood that subglacial microbes could convert 63 Pg of SOC to methane during a glacial cycle. If this were the case, release of this methane from the ice sheet margins during retreat would need to be episodic in order to significantly impact atmospheric methane concentrations. Our findings suggest that it may well be important to consider subglacial environments as active components of the Earth's carbon cycle. Conclusive determination of the potential impact of subglacial methane production on atmospheric methane concentrations during deglaciation, however, awaits more precise determination of the ability of subglacial microbes to degrade organic carbon components and their associated rates of metabolism under in situ conditions.

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Microorganisms in the Accreted Ice of Lake Vostok, Antarctica

Cited by 337 publications

References 29 publications

Resource quality affects carbon cycling in deep-sea sediments

Resource quality affects carbon cycling in deep-sea sediments

Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge

Subglacial methanogenesis: A potential climatic amplifier?

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