25th International Meeting on Organic Geochemistry IMOG 2011

P-168
Correlation of crenarchaea and phytoplankton biomarkers
indicate metabolic dependence
Susanne Fietz 1 , Carme Huguet 1 , Alfredo Martinez-Garcia 3 , Gemma Rueda 1 , Vicky Peck 4 ,
Marina Escala 1 , Antoni Rosell-Melé 1,2
1 Institut de Ciència i Tecnlogia Ambientals (ICTA), Universitat Autònoma de Barcelona (UAB), Barcelona,
Spain, 2 Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain, 3 ETH Zürich, Zürich,
Switzerland, 4 British Antarctic Survey, Cmbridge, United Kingdom (corresponding
author:susanne.fietz@uab.cat)
Archaea are ubiquitously distributed and usually
constitute a large part (up to 30%) of the
picoplankton. However, their metabolic pathway
(chemoautotrophic, mixotrophic or heterotrophic) is
still discussed, and it remains debatable whether
phytoplankton derived organic matter is an important
energy or carbon source for Archaea. For bacteria, in
contrast, the dependence on phytoplankton and
consequent co-variation with phytoplankton has long
been established. To seek new evidence on the
existence of a coupling between phytoplankton and
Thaumarchaea 2 , we investigated the occurrence of
specific biomarkers of these organisms in
sedimentary archives, which encompass larger timespans
than snap-shot water column samples. We
used chlorins, chlorophyll transformation products
indicative of phytoplankton production 3 and
crenachaeol, a marker for Thaumarchaea
abundance 4 . Sedimentary records of freshwater (Lake
Baikal, Russia) and marine settings (Arctic Ocean,
Atlantic Ocean and Southern Ocean) covering glacial
and interglacial time spans were studied.
Despite the wide range of environmental conditions of
these records, we observed a pervasive tight (rs>0.75)
and statistically significant coupling between both
biomarkers at all investigated sites (example for Lake
Baikal in Fig.1A). The slopes of the regression line
between the two compounds (Fig. 1B) indicated
differential Crenarchaeal response strengths to
phytoplankton productivity between the studied
systems. Various factors such as degradation,
transport mechanisms or a common environmental
trigger may in part account for the tight correlation,
but these mechanisms cannot fully explain our
observations. Our findings instead indicate that
Thaumarchaea are dependent on resources released
by phytoplankton, such as organic carbon or
ammonium.
1 Könneke, M. et al. 2005. Nature 437: 543-546
2 Brochier-Armanet, C. et al. 2008. Nat Rev Microbiol
6: 245–252.
3
Sinninghe Damsté, J.S. et al. 2002. J. Lipid Res.
43:1641–1651.
4
Harris ,P.G. et al. 1996. Nature 383: 63–65.
Figure 1. Examples of the correlation of chlorins
(chlorophyll transformation products) and crenarchaeol A)
chlorins and crenarchaeol concentrations per gram dry
matter in Lake Baikal during the Last Interglacial
(approximate MIS5e) and transitional periods; B)
Correlation between chlorins and crenarchaeol
concentrations in Lake Baikal and the subantarctic
Southern Ocean (ODP site 1090); the log-log fits were
significant at 1%CI level with R²=0.90 in Lake Baikal and
R²=0.78 in the Southern Ocean.
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