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Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography

Lawson, E. C.; Wadham, J. L.; Lis, G. P.; Tranter, M.; Pickard, A. E.; Stibal, M.; Dewsbury, P.; Fitzsimons, S.

Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography Thumbnail


Authors

J. L. Wadham

G. P. Lis

M. Tranter

A. E. Pickard

M. Stibal

P. Dewsbury

S. Fitzsimons



Abstract

© Author(s) 2015. Glacial runoff is an important source of dissolved organic carbon (DOC) for downstream heterotrophic activity, despite the low overall DOC concentrations. This is because of the abundance of bioavailable, low molecular weight (LMW) DOC species. However, the provenance and character of LMW-DOC is not fully understood. We investigated the abundance and composition of DOC in subglacial environments via a molecular level DOC analysis of basal ice, which forms by water/sediment freeze-on to the glacier sole. Spectrofluorometry and a novel ion chromatographic method, which has been little utilised in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates and carboxylic acids) in basal ice from four glaciers, each with a different basal debris type. Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse FAA pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn, was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard) and Engabreen (Norway) were low (0-417 nM C), attributed to the relatively refractory nature of the OC in the overridden paleosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (>17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet sediments in current subglacial environments.

Citation

Lawson, E. C., Wadham, J. L., Lis, G. P., Tranter, M., Pickard, A. E., Stibal, M., …Fitzsimons, S. (2016). Identification and analysis of low molecular weight dissolved organic carbon in subglacial basal ice ecosystems by ion chromatography. Biogeosciences Discussions, 12(16), 14139-14174. https://doi.org/10.5194/bgd-12-14139-2015

Journal Article Type Article
Acceptance Date Jun 13, 2016
Online Publication Date Jul 1, 2016
Publication Date Jul 1, 2016
Deposit Date Nov 6, 2019
Publicly Available Date Mar 29, 2024
Journal Biogeosciences Discussions
Print ISSN 1810-6277
Electronic ISSN 1810-6285
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 12
Issue 16
Pages 14139-14174
DOI https://doi.org/10.5194/bgd-12-14139-2015
Keywords Earth-Surface Processes; Ecology, Evolution, Behavior and Systematics
Public URL https://nottingham-repository.worktribe.com/output/3031089
Publisher URL https://www.biogeosciences.net/13/3833/2016/bg-13-3833-2016-discussion.html

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