25th International Meeting on Organic Geochemistry IMOG 2011

P-162
Lipid biomarkers and bulk biogenic components in sinking
particles from the SW Black Sea
Ioanna Bouloubassi 1 , Alexandra Gogou 2 , Anna Sanchez-Vidal 3 , Spyros Stavrakakis 2
1 LOCEAN, IPSL, CNRS/UPMC/IRD, Paris, France, 2 HCMR, Institute of Oceanography, Anavyssos, Greece,
3 GRC Geociencies Marines, Universitat de Barcelona, Barcelona, Spain (corresponding
author:ioanna.bouloubassi@upmc.fr)
Sinking particles were obtained with an instrumented
array moored in the SW Black Sea (2000 m water
depth) over a period of 12 months (Oct. 2007-
Oct.2008), equipped with two sediment traps (at
1000m and 1965m) with a sampling period of 15
days. The settling material was investigated in terms
of total mass flux, major biogenic components
(organic carbon, carbonates, opal) and lipid
biomarkers.
The mean annual mass fluxes were 109 and 86 mg
m -2 d -1 , at 1000m and 1965m, respectively. The
composition of particulate matter was similar at both
depths, characterized by high organic carbon
contents, reaching 11%. Overall, the biogenic
components were dominant, accounting for ca. 54%.
Mass fluxes showed strong temporal variations over
the experimental period with three major maxima in
early summer and fall/winter. Organic carbon fluxes
averaged 11 and 9 mg/m 2 /d in mid- and deep waters
and they generally followed the temporal pattern of
total mass fluxes. Carbonates showed a major peak
in late spring/summer reaching 178 mg/m 2 /d, while
high opal fluxes were recorded mainly in winter, with
secondary peaks in late spring/summer and fall.
Source-specific lipid biomarkers allowed assessing
the composition and variability of settling material in
detail. Terrestrial biomarkers (long chain n-alkanes)
were minor components, with high values reflecting
the periods of enhanced discharges of the Danube
River that control the pattern of lithogenic fluxes.
Marine biomarkers, deriving from primary producers,
were fairly predominant. High amounts and fluxes of
alkenones were observed, consistent with the high
coccolithophorid production in the Black Sea. The
temporal patterns delineate a major bloom in late
spring/summer that clearly controls the carbonate flux
variability. The concentrations and fluxes of diatombiomarkers
(C28 sterols, HBI) depict the temporal
patterns of downward organic carbon fluxes,
suggesting that diatom production exerts a main
control on carbon export. Moreover, diatom
biomarkers portray the temporal variability of opal
fluxes. Biomarkers tracing mainly dinoflagellates (e.g.
dinosterol) also show important temporal variation.
Besides, biomarkers derived mainly from zooplankton
show elevated concentrations and fluxes and their
temporal patterns indicate their links with enhanced
organic carbon export.
Comparisons between the mid-depth and deep traps
show that the transfer is rapid and that carbon
recycling is not very important, leading to enhanced
carbon sequestration in this marine site.
Overall, the lipid biomarker data set sheds light on the
origin of organic carbon in settling particles in the SW
Black Sea and, coupled to bulk parameters, enables
assessing the primary controls on the downward
biogenic fluxes.
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