25th International Meeting on Organic Geochemistry IMOG 2011

P-215
Distributions of long-chain diols in surface sediments from the
North Pacific: possible revised diatom biomarker
paleothermometry
Madoka Kobayashi 1 , Ken Sawada 1 , Osamu Seki 2
1 Fuculty of Science, Hokkaido University, Sapporo, Japan, 2 Institute of Low Temperature Sciences,
Hokkaido University, Sapporo, Japan (corresponding author:kmadoka@mail.sci.hokudai.ac.jp)
Biomarker thermometers such as alkenone
unsaturation index (U K 37 and U K‘ 37) have been often
used for reconstructing paleo-sea surface
temperatures since 1980s. The alkenones are well
known to be derived from Haptophycean algae, which
are ubiquitous species in shallow to open ocean
areas at low to high latitude, and therefore, their
thermometers are powerful proxies in the almost over
the world oceans. However, it has been pointed out
that there were limitations for alkenone proxies;
physiological effect, deflection of temperature records
during the season of high production, variability of
source species, and so on.
More recently, several researchers [1] suggest new
algal biomarker thermometer, the ratios of 28 carbon
numbers (C28) and C30 1,14-diols in marine
sediments. These compounds are likely to be derived
from specific diatom Proboscia.
In this study, we examine the applicability of such
diatom biomarker thermometer from thirty six surface
sediments around the Pacific Ocean. Three
sediments were collected by multiple corer, while
thirty three sediments are a part of ODP cores.
Annual mean SST range is 5°C to 29°C. Freeze dried
sediment samples were extracted and extracts were
fractionated by silica gel chromatography before
analyses using GC/MS.
The diol thermometer is proposed as the ratio of
monounsaturated and saturated C28 to monounsaturated
and saturated C30 1,14-diols, called
Proboscia diol index (PDI), by the analyses of the
Proboscia cultures and the sediments in the Atlantic
and Southern Oceans [1, 2].
The C28 and C30 1,14-diols could be detected in
most of sediment samples in this study (Fig.1). We
compared some kinds of the 1,14-diols ratios and
annual mean SST. It was clear that the PDI were not
correlated with annual mean SST in the Pacific
sediments. In addition, the PDI were not correlated
with U K‘ 37 in the most of samples. On the other hand,
the unsaturation ratios of C28 1,14-diols and C30 1,14diols,
which were newly defined as UD28 and UD30,
respectively, were well correlated with annual mean
temperature and U K‘ 37. These UD28 and UD30 indices
can be revised paleothemometer by using diatom
biomarkers for PDI. These results might be attributed
to the differences of source species (and/or genetic
variations) producing the long-chain 1,14-diol in the
North Pacific from those in the Atlantic and Southern
Oceans as reported by literature [1, 2].
Fig.1 Partial mass fragmentograms of C28 (m/z 299)
and C30 (m/z 327) 1,14-diols in a surface sediment
from the northwestern Pacific off northern Japan.
References
[1] Rampen, S.W., Schouten, S., Schefus, E.,
Sinninghe Damste, J.S. (2009) Organic
Geochemistry 40, 1124-1131.
[2] Willmott, V., Rampen, S.W., Domack, E., Canals,
Sinninghe Damste, J.S. Schouten, S.(2010)
Antarctic Science 22(1), 3-10.
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