Environmental Engineering Reference
In-Depth Information
RECENT STUDIES ON SOURCES AND SINKS OF
METHANE IN THE BLACK SEA
Carsten J. Schubert
1
, Edith Durisch-Kaiser
1
, Lucia Klauser
1
, Francisco Vazquez
1
,
Bernhard Wehrli
1
, Christian P. Holzner
2
, Rolf Kipfer
2
, Oliver Schmale
3
, Jens
Greinert
3
and Marcel M.M. Kuypers
4
1
EAWAG, Surface Waters, Seestrasse 79, 6047 Kastanienbaum, Switzerland
2
EAWAG, Water Resources and Drinking Water, Uberlandstrasse 133, 8600 D ubendorf, Switzer-
land
3
Leibniz-Institute of Marine Sciences (IFM-GEOMAR), Wischhofstrasse 1-3, 24148 Kiel, Ger-
many
4
Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany
Abstract
This study focuses on the influence of gas seepage on methane sources and
sinks, aerobic and anaerobic oxidation of methane and the mediating microbial
organisms in the Black Sea. We present data from two cruises that took place
in 2001 and 2003. Seven stations (two from the shelf, four from the upper and
lower slope, and one from the central basin) were compared with respect to
methane concentration and isotope signature. The stations differed in methane
concentration depending on the location on the slope. A strong change in the
concentration and isotopic composition of methane was observed below the
oxic/anoxic interface, coinciding with increased levels of archaeal biomarkers
(archaeol and sn-2-hydroxy-archaeol). Concentration and isotopic composition
of methane in the water column and sediments indicate that sediments from the
shelf, slope, and deep basin are only minor sources of methane. The main methane
sources are seeps located on the shelf and upper slope, but also in the deep basin.
The comparison of two shelf stations with and without methane seepage showed
a difference in methane concentrations, isotopic composition and oxidation rates,
but the presence of similar methanotrophic microbial assemblages. Also two deep
stations at a seep and outside of a seep area were compared, but here methane
concentrations and oxidation rates were not different from each other. Anaerobic
methane oxidizers (ANME-1 and ANME-2 group) were observed at both stations
with slightly higher cell counts at the seep station.
Keywords:
Black Sea, methane concentration, methane isotopic composition, methane oxi-
dation, methane seeps, methanotrophs
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