25th International Meeting on Organic Geochemistry IMOG 2011

P-407
Compound specific hydrogen isotopes as indicator of core
metabolisms of benthic microorganisms in the Wadden Sea
Sandra Heinzelmann, Laura Villanueva, Stefan Schouten, Jaap Sinninghe Damsté,
Marcel van der Meer
NIOZ Netherlands Institute for Sea Research, Den Burg, Netherlands (corresponding
author:sandra.heinzelmann@nioz.nl)
The low elevation coastal zone is extremely
important since 10% of the human population lives
within 10 meters above the current sea level. In
addition, coastal areas form the habitat of a crucial
part of global biodiversity and play important roles in
global biogeochemical cycles. Climate changes of the
magnitude projected for the present century by the
Intergovernmental Panel on Climate Change would
impact the coastal zone in a number of ways, but
mainly by the projected global sea level rise. Microbial
communities in coastal environments are important in
this respect as they are at the bottom of the food
chain and thus often the first to deal with both natural
and human induced disturbances of the environment
and thereby form a natural buffer for the entire coastal
ecosystem. Microbial ecosystems also play an
important role in the intertidal areas of coastal zones
by sediment stabilization leading to sediment
accretion and even ―land‖ formation and thus form a
―natural‖ protection against potential sea level rises.
However, little is known about the fundamental role of
microbial communities in coastal zones and how this
might change under changing conditions. To
investigate their role, the main microbes in these
communities and especially the metabolisms
expressed in situ needs to be determined.
In this study, we examined microbial
communities present in different areas of the
Waddensea with a focus on the microbial mats on the
sandy beaches of the island Schiermonnikoog. These
microbial mats are ideal environments to study
different microbial metabolisms since they are formed
by photoautotrophic organisms producing organic
carbon used by heterotrophic organisms that deplete
the oxygen in the sediment. This enables sulphate
reducers to grow and produce sulphide, which in turn
is used by chemolithoautotrophic, photoautotrophic
and photoheterotrophic sulphide oxidizers.
We are also applying hydrogen isotopic
composition of lipid biomarkers as a new culture
independent tool for assessing the core metabolisms
of microorganisms as it has recently been shown that
there might be relatively large differences in hydrogen
isotopic composition of lipids produced by
microorganisms with different core metabolisms (1).
The results will be compared with those obtained by
stable isotope labelling of 16S rRNA and RNA
expression of specific genes for autotrophic and
heterotrophic microbes.
Figure 1: Indicated are those organisms that form
visible, well defined layers. Among the organisms that
are present, but do not produce visible layers are:
heterotrophs, Archaea and colorless sulfur bacteria
(chemolithoautotrophs).
1. X. Zhang, A. L. Gillespie, A. L. Sessions, Proc.
Natl. Acad. Sci. U. S. A 106, 12580 (2009).
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