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T7
Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica: A
consideration for palaeoreconstructions
V.N. Panizzo 1 *, J. Crespin 2 , X. Crosta 3 , A. Shemesh 2 , G. Massé 4,5 , R. Yam 2 , N. Mattielli 7
and Damien Cardinal 5,6,7
1 School of Geography, University of Nottingham, University Park, Nottingham, NG27 2RD
2 Department of Environmental Sciences and Energy Research, Weizmann Institute of Science,
Rehovot, 76100, Israel
3 UMR-CNRS 5805 EPOC, Avenue des Facultés, Université Bordeaux I, 33405 Talence Cedex, France
4 UMI3376 TAKUVIK– CNRS/U. Laval, Université Laval, 1045 avenue de la Médecine, G1V 0A6
Québec, Canada
5 LOCEAN – IPSL, UPMC/IRD/CNRS/MNHN, Université Pierre et Marie Curie, 4 Place Jussieu, Boite
100, F-75252 PARIS Cedex 05, France
6 Université Libre de Bruxelles, Department of Earth and Environmental Sciences, CP 160/02 Avenue
F.D. Roosevelt 50, 1050 Bruxelles, Belgium
7 Section of Mineralogy and Geochemistry, Royal Museum for Central Africa, Leuvensesteenweg, 13,
B-3080, Tervuren, Belgium
The first combined high resolution Holocene δ 30 Si diat and δ 13 C diat paleorecords are
presented from the Seasonal Ice Zone, East Antarctica. Both data sets reflect periods of
increased nutrient utilization by diatoms during the Hypsithermal period (c. 7,800 to 3,500
years BP), coincident with a higher abundance of open water diatom species
(Fragilariopsis kerguelensis), increased biogenic silica productivity (%BSi) and higher
regional summer temperatures. The Neoglacial period (after c. 3,500 years BP) is
reflected by an increase in sea ice indicative species (Fragilariopsis curta and
Fragilariopsis cylindrus, up to 50%) along with a decrease in %BSi and δ13C diat (< -18‰).
However, over this period δ 30 Si diat data show an increasing trend, to some of the highest
values in the Holocene record (average of 0.43‰). Competing hypotheses are discussed
to account for the decoupling trend in utilization proxies including iron fertilization, speciesdependent
fractionation effects and diatom habitats. Based on mass balance calculations,
we highlight that diatom species derived from the semi-enclosed sea ice environment may
have a confounding effect upon δ 30 Si downcore compositions of the seasonal sea ice zone. A
diatom composition, with c. 28% of BSi derived from the sea ice environment (diat-SI) can
account for the increased average composition of δ 30 Si diat during the Neoglacial. These
data highlight the implications of productivity reconstructions from the seasonal ice zone
(SIZ) and argue that more comprehensive investigations of diatom habitats, sea ice
structure and upwelling are needed to help constrain these records.
Key words: diatoms; silicon isotopes; carbon specific isotopes; Seasonal Ice Zone; ice
cover; Holocene; Southern Ocean; East Antarctica