Biogeochemistry and microbial diversity in the marine cavity beneath the McMurdo Ice Shelf, Antarctica

Vick‐Majors, Trista J.; Achberger, Amanda M.; Santibáñez, Pamela A.; Dore, John E.; Hodson, Timothy O.; Michaud, Alexander B.; Christner, Brent C.; Mikucki, Jill A.; Skidmore, M. L.; Powell, Ross D.; Adkins, W. Peyton; Barbante, Carlo; Mitchell, Andrew C.; Scherer, Reed P.; Priscu, John C.

doi:10.1002/lno.10234

Cited by 39 publications

(25 citation statements)

References 86 publications

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“…The J9 sediment and water column studies showed microbial communities capable of metabolizing organic carbon substrates and fixing inorganic C in the dark (Horrigan, ), and a benthic community dominated by scavengers (Lipps et al, ). Data from closer to the ice shelf margin (Vick‐Majors, Achberger et al, ) revealed dark inorganic C‐fixation rates similar to those determined by Horrigan (; ~6 nmol C L −1 day −1 ) that were exceeded by heterotrophic microbial carbon demand. These results imply that in situ carbon production is insufficient to sustain the carbon demand under the RIS and that other sources of DOC are required.…”

Section: Resultsmentioning

confidence: 64%

“…However, long residence times (~3.5 yr; Smethie & Jacobs, ) provide time for drawdown of supplemental DOC under the ice during water mass transport. Indeed, DOC concentrations in source waters beneath (Vick‐Majors, Achberger et al, ) or proximate to (Bercovici et al, ) the McMurdo Ice Shelf were approximately 40 μmol C L −1 (~37 μmol C L −1 , Vick‐Majors, Achberger et al, ; ~47 μmol C L −1 in Ross Sea Dense Shelf Water, Bercovici et al, ), while average DOC concentrations in water collected at the GZ were approximately twice these values (75 μmol C L −1 ). Apparent DOC enrichment at the GZ raises the possibility that subglacial outflows could be an important subsidy to coastal and estuarine biogeochemical processes under the RIS.…”

Section: Resultsmentioning

confidence: 99%

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Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment

Vick‐Majors

Michaud

Skidmore

et al. 2020

Global Biogeochemical Cycles

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Although subglacial aquatic environments are widespread beneath the Antarctic ice sheet, subglacial biogeochemistry is not well understood, and the contribution of subglacial water to coastal ocean carbon and nutrient cycling remains poorly constrained. The Whillans Subglacial Lake (SLW) ecosystem is upstream from West Antarctica's Gould‐Siple Coast ~800 m beneath the surface of the Whillans Ice Stream. SLW hosts an active microbial ecosystem and is part of an active hydrological system that drains into the marine cavity beneath the adjacent Ross Ice Shelf. Here we examine sources and sinks for organic matter in the lake and estimate the freshwater carbon and nutrient delivery from discharges into the coastal embayment. Fluorescence‐based characterization of dissolved organic matter revealed microbially driven differences between sediment pore waters and lake water, with an increasing contribution from relict humic‐like dissolved organic matter with sediment depth. Mass balance calculations indicated that the pool of dissolved organic carbon in the SLW water column could be produced in 4.8 to 11.9 yr, which is a time frame similar to that of the lakes’ fill‐drain cycle. Based on these estimates, subglacial lake water discharged at the Siple Coast could supply an average of 5,400% more than the heterotrophic carbon demand within Siple Coast embayments (6.5% for the entire Ross Ice Shelf cavity). Our results suggest that subglacial discharge represents a heretofore unappreciated source of microbially processed dissolved organic carbon and other nutrients to the Southern Ocean.

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Section: Resultsmentioning

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment

Vick‐Majors

Michaud

Skidmore

et al. 2020

Global Biogeochemical Cycles

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“…OTUs with high betweenness centrality values might possess high impact on other interactions in the community ( Greenblum et al, 2012 ). Keystone nodes in co-occurrence networks tend to have maximum betweenness centrality values ( Vick-Majors et al, 2015 ; Banerjee et al, 2016 ). Based on betweenness centrality, most keystone bacterial nodes in our study belonged to the most abundant phyla Proteobacteria and Bacteroidetes in both top- and subsoil.…”

Section: Discussionmentioning

confidence: 99%

Long-term Fertilization Structures Bacterial and Archaeal Communities along Soil Depth Gradient in a Paddy Soil

Wang

Shen

et al. 2017

Front. Microbiol.

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Soil microbes provide important ecosystem services. Though the effects of changes in nutrient availability due to fertilization on the soil microbial communities in the topsoil (tilled layer, 0–20 cm) have been extensively explored, the effects on communities and their associations with soil nutrients in the subsoil (below 20 cm) which is rarely impacted by tillage are still unclear. 16S rRNA gene amplicon sequencing was used to investigate bacterial and archaeal communities in a Pup-Calric-Entisol soil treated for 32 years with chemical fertilizer (CF) and CF combined with farmyard manure (CFM), and to reveal links between soil properties and specific bacterial and archaeal taxa in both the top- and subsoil. The results showed that both CF and CFM treatments increased soil organic carbon (SOC), soil moisture (MO) and total nitrogen (TN) while decreased the nitrate_N content through the profile. Fertilizer applications also increased Olsen phosphorus (OP) content in most soil layers. Microbial communities in the topsoil were significantly different from those in subsoil. Compared to the CF treatment, taxa such as Nitrososphaera, Nitrospira, and several members of Acidobacteria in topsoil and Subdivision 3 genera incertae sedis, Leptolinea, and Bellilinea in subsoil were substantially more abundant in CFM. A co-occurrence based network analysis demonstrated that SOC and OP were the most important soil parameters that positively correlated with specific bacterial and archaeal taxa in topsoil and subsoil, respectively. Hydrogenophaga was identified as the keystone genus in the topsoil, while genera Phenylobacterium and Steroidobacter were identified as the keystone taxa in subsoil. The taxa identified above are involved in the decomposition of complex organic compounds and soil carbon, nitrogen, and phosphorus transformations. This study revealed that the spatial variability of soil properties due to long-term fertilization strongly shapes the bacterial and archaeal community composition and their interactions at both high and low taxonomic levels across the whole soil profile.

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“…After passing through the filtration and UV treatment system, the drilling fluid was heated to 90 • C and pressurized for drilling operations within the boiler units [49], which also served to 'flash pasteurize' the water. The effectiveness of the water treatment unit was verified in the USA prior to deployment and when mated to the hot water drill during a test that penetrated the McMurdo Ice Shelf [50]. Drilling fluid was initially generated by melting snow collected at the surface near the drill location, but upwind of airfield and power generation operations.…”

Section: Sampling Subglacial Lake Whillans (A) Clean Access Approachmentioning

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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Biogeochemistry and microbial diversity in the marine cavity beneath the McMurdo Ice Shelf, Antarctica

Cited by 39 publications

References 86 publications

Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment

Biogeochemical Connectivity Between Freshwater Ecosystems beneath the West Antarctic Ice Sheet and the Sub‐Ice Marine Environment

Long-term Fertilization Structures Bacterial and Archaeal Communities along Soil Depth Gradient in a Paddy Soil

Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge

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