25th International Meeting on Organic Geochemistry IMOG 2011

P-427
Quantitative reconstructions of methanogenic and
methanotrophic archaeal communities in Lake Rotsee,
Switzerland, using biomarker concentrations and their carbon
isotopic compositions
Sebastian Naeher 1,2 , Rienk Smittenberg 3 , Carsten Schubert 1
1 Swiss Federal Institute of Aquatic Science and Technology (Eawag), Department of Surface Waters-
Research and Management, Kastanienbaum, Switzerland, 2 ETH Zurich, Department of Environmental
Sciences, Institute for Biogeochemistry and Pollution Dynamics, Zurich, Switzerland, 3 ETH Zurich,
Department of Earth Sciences, Climate Geology, Zurich, Switzerland (corresponding
author:sebastian.naeher@eawag.ch)
We quantitatively reconstructed methanogenic and
methanotrophic archaeal community changes from a
sediment core of the eutrophic Lake Rotsee in
Switzerland. This study is based on biomarker
concentrations in the sediment with a temporal
resolution of up to 3 years per sample, carbon
isotopes, combined with results from an earlier study
on vertical distributions of active methanogens in the
sediment of Lake Rotsee [1].
Lake Rotsee is a monomictic and stratified lake with
an anoxic hypolimnion most of the year. Because of
the shallow water column of Lake Rotsee (maximum
water depth 16m) and the stratification, relatively little
degradation of organic matter occurs. Methane
concentrations in the hypolimnion were up to 1mM in
fall 2007 [2].
Around 1920 not only the bioproductivity increased in
Lake Rotsee, but in coherence also the abundance of
methanogenic archaea, indicated by elevated
concentrations of caldarchaeol. In addition to
caldarchaeol also diplopterol and 17β(H),17β(H)homohopanoic
acid concentrations increased. We
relate this to the construction of a tunnel from Reuss
River which was constructed in 1922. The tunnel was
an unsuccessful attempt to increase the freshwater
input to recover the lake [3]. Zepp Falz et al. [1] could
show that on average 91% of the archaeal population
in Lake Rotsee is represented by the acetoclastic
Methanosaeta spp. alone. The methanogenic archaea
dominance is indicated by carbon isotopes
measurements from glycerol dialkyl glycerol
tetraethers (GDGTs) obtained by ether cleavage. Few
years later, higher concentrations of biomarkers
related to methanotrophic archaea could be
determined because of their highly depleted carbon
isotopic signal of diploptene, archaeol,
hydroxyarchaeol and 17β(H),17β(H)-homohopanoic
acid. In the 1970s Lake Rotsee reached another high
eutrophication state. During this time, stratification
seemed to become more stable and anoxic conditions
increased because of higher supply of organic
material into the sediment which triggered increased
abundances in methanogenic and methanotrophic
archaea.
Based on Zepp Falz et al. [1], microbial densities
could be calculated under certain assumptions
concerning biomarker degradation for the last 100
years.
References
[1] Zepp Falz K., Holliger C., Grosskopf R.,
Liesack W., Nozhevnikova A.N., Müller B., Wehrli B.,
Hahn D. (1999) Vertical distribution of methanogens
in the anoxic sediment of Rotsee (Switzerland). Appl
Environ Microbiol 65(6):2402–2408
[2] Schubert C.J., Lucas F.S., Durisch-Kaiser
E., Stierli R., Diem T., Scheidegger O., Vazquez F.,
Müller B. (2010) Oxidation and emission of methane
in a monomictic Lake (Rotsee, Switzerland). Aquat
Sci 72:455–466
[3] Kohler H-P, Ahring B, Albella C, Ingvorsen K,
Kewelsh H, Laczko E et al. (1984) Bacteriological
studies on the sulfur cycle in the anaerobic part of the
hypolimnion and in the surface sediments of Rotsee
in Switzerland. FEMS Microbiol Lett 21:279–286
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