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Titel |
Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment |
VerfasserIn |
S. F. Henley, A. L. Annett, R. S. Ganeshram, D. S. Carson, K. Weston, X. Crosta, A. Tait, J. Dougans, A. E. Fallick, A. Clarke |
Medientyp |
Artikel
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Sprache |
Englisch
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ISSN |
1726-4170
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Digitales Dokument |
URL |
Erschienen |
In: Biogeosciences ; 9, no. 3 ; Nr. 9, no. 3 (2012-03-27), S.1137-1157 |
Datensatznummer |
250006850
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Publikation (Nr.) |
copernicus.org/bg-9-1137-2012.pdf |
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Zusammenfassung |
A high resolution time-series analysis of stable carbon isotopic signatures
in particulate organic carbon (δ13CPOC) and associated
biogeochemical parameters in sea ice and surface waters provides an insight
into the factors affecting δ13CPOC in the coastal western
Antarctic Peninsula sea ice environment. The study covers two austral summer
seasons in Ryder Bay, northern Marguerite Bay between 2004 and 2006. A shift
in diatom species composition during the 2005/06 summer bloom to
near-complete biomass dominance of Proboscia inermis is strongly correlated with a large
~10 ‰ negative isotopic shift in δ13CPOC that cannot
be explained by a concurrent change in concentration or isotopic signature
of CO2. We hypothesise that the δ13CPOC shift may be
driven by the contrasting biochemical mechanisms and utilisation of
carbon-concentrating mechanisms (CCMs) in different diatom species.
Specifically, very low δ13CPOC in P. inermis may be caused by the
lack of a CCM, whilst some diatom species abundant at times of higher
δ13CPOC may employ CCMs. These short-lived yet pronounced
negative δ13CPOC excursions drive a 4 ‰ decrease in the
seasonal average δ13CPOC signal, which is transferred to
sediment traps and core-top sediments and consequently has the potential for
preservation in the sedimentary record. This 4 ‰ difference between seasons
of contrasting sea ice conditions and upper water column stratification
matches the full amplitude of glacial-interglacial Southern Ocean δ13CPOC variability and, as such, we invoke phytoplankton species
changes as a potentially important factor influencing sedimentary δ13CPOC. We also find significantly higher δ13CPOC in sea ice than surface waters, consistent with
autotrophic carbon fixation in a semi-closed environment and possible
contributions from post-production degradation, biological utilisation of
HCO3− and production of exopolymeric substances. This study
demonstrates the importance of surface water diatom speciation effects and
isotopically heavy sea ice-derived material for δ13CPOC in
Antarctic coastal environments and underlying sediments, with consequences
for the utility of diatom-based δ13CPOC in the sedimentary
record. |
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