25th International Meeting on Organic Geochemistry IMOG 2011

P-437
Microbial community shifts at temperature and geochemical
gradients at sulfur-rich shallow hydrothermal vents offshore
Panarea Island, Sicily
Florence Schubotz 1,4 , Chia-I Huang 2 , Gunter Wegener 2 , Jan P. Amend 3 , Roy Price 3 ,
Thomas Holler 2 , Anke Meyerdierks 2 , Rudolf Amann 2 , Roger E. Summons 4 , Kai-Uwe
Hinrichs 1
1 Department of Geosciences and MARUM - Center for Marine Environmental Sciences, Bremen, Germany,
2 Max-Planck Institute for Marine Microbiology, Bremen, Germany, 3 Department of Earth, Atmospheric and
Planetary Sciences, Washington University, St. Louis, Germany, 4 Department of Earth, Atmospheric and
Planetary Sciences, Massachusetts Institute of Technology, Cambridge, United States of America
(corresponding author:schubotz@uni-bremen.de)
The active volcanic islands of the Eolian
Archipelago north of Sicily, Italy, have been used for
many decades as a natural laboratory for the study of
thermophilic Bacteria and Archaea [1]. Most recently,
the shallow marine hydrothermal vents off the coast of
Panarea Island have attracted attention due to a
submarine volcanic exhalative event in 2002. Some
sites (Blackpoint) are characterized by vigorous
venting with maximum temperatures of up to 135°C,
whereas other sites exhibit more diffusive venting with
temperatures ranging from 40 to 70°C (Hot Lake).
The hydrothermal fluids off Panarea Island are rich in
CO2 (up to 97 vol.%), and H2S (up to 2 Vol.%) [2], and
are slightly acidic (pH 5-6; Fig. 1a).
Investigations of the intact polar membrane lipid
(IPL) composition in sediments ranging from ca. 40-
90°C (Fig. 1a) showed a dominance of bacterial lipids
at lower temperatures (Hot Lake I) mainly comprised
of ornithine lipids and the phospholipids
phosphoethanolamine, phospho-(N)-methylethanolamine,
phosphocholine, phosphoglycerol and
diphosphoglycerol (Fig 1b). Betaine lipids and
glycolipids, which are likely derived from phototrophic
organisms in the surface sediments decrease with
increasing sediment depth. Notable is a shift to a
dominance of archaeal lipids with depth and/or
temperature at Hot Lake II and Blackpoint I. The
observed archaeal IPLs are diglycosidic glycerol
dibiphytanyl tetraethers (GDGT) with core lipids
comprised of 0 to 2 pentacyclic rings and a series of
H-shaped GDGTs. IPL investigations are
accompanied by a series of molecular biological
analyses such as fluorescence in situ hybridization
(FISH) and comparative 16S rRNA gene analyses.
FISH results are consistent with an increase of
Archaea relative to Bacteria with increasing sediment
depth. Epsilonproteobacteria, Bacteriodetes and
Deltaproteobacteria are identified as major bacterial
groups at lower temperatures while clones affiliated to
the crenarchaeotal Desulfurococcaceae and
Korarchaeota are found with increasing temperature
and sediment depth.
To investigate major pathways of carbon turnover
under anaerobic conditions in the sediments we have
conducted a 13 C and deuterium lipid-labelling study.
The results will be evaluated by head group specific
label uptake [2] in concert with gene-based analyses
to enable more detailed chemotaxonomic
assignments.
Fig. 1. a) Depth profiles of temperature, pH, and IPL
total concentration at sites Hot Lake and Blackpoint.
b) Composition of IPLs at two depth intervals of the
three investigated sites.
References
[1] Amend J.P. and Shock E.L. (2001) FEMS
Microbiol. Rev. 25, 175-243.
[2] Schubotz F., et al. (2011) Geochim. Cosmo-chim.
Acta. doi:10.1016/j.gca.2011.05.018
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