Environmental Engineering Reference
In-Depth Information
Another important question is the identity, distribution and activity of mi-
crobial organisms responsible for anaerobic and aerobic methane oxidation in
the Black Sea water column. Biomarker and compound specific stable isotope
investigations on particulate material collected from the anoxic water column
showed that archaea may be involved in methane oxidation [43, 49]. Methane
oxidation rates are around 10
−
3
nM d
−
1
in the upper water layer and increase
to a few nanomoles per day below 100 m [37]. However, beside these organic
geochemical investigations there are no published molecular biological reports
so far that really identified those organisms.
Relatively recent findings especially in the north-western part of the Black
Sea are methane seeps [2, 18]. At these locations methane enters the water
column in the aerobic as well as in the anaerobic water zone and tremendously
influences the methane inventory of the Black Sea.
In order to better understand methane turnover in the Black Sea we measured
methane concentrations in the sediments at two shallow sites on the NW and
SW slope and at a deep site in the central basin. Additionally, we investigated
several biogeochemical parameters related to methane in the water column at
shallow and deep methane seeps and non-seep sites. Measurements were per-
formed in sediments as well as in the water column to investigate further the
sink/source behavior of the seafloor. Methane stable carbon isotopic compo-
sition was determined for further insight into the oxidation/formation patterns
of methane. Additional biomarker and molecular investigations of particulate
water column material were performed to reveal which organisms are involved
in the methane oxidation. The data presented are partly preliminary results from
ongoing research that will be further evaluated in the future.
2. METHODS AND MATERIALS
2.1 Sampling
During cruise M51-4 in December 2001 with the German research vessel
R/V Meteor
water column profiles and sediment cores were sampled at the
following stations: 7605 (42 30,71'N, 30 14,69'E) at 2130 m water depth in the
central basin, 7617 (43 38,04'N, 30 02,54'E) at 1560 m water depth from the
NW slope, and 7623 (41 44,77'N, 31 10,28'E) at 876 m water depth from the
SW slope (Fig. 1). Additionally, samples were recovered during the CRIMEA
cruise with
R/V Professor Vodyanitskiy
in 2003. Presence of gas seepage was
identified hydroacoustically by an echosounder system sensitive to gas bubbles
onboard. Water samples were taken at two shallow sites, namely a gas plume
site above a cold seep (CTD-038: 44
◦
50'N, 31
◦
59'E, 92 m water depth) and
a near by reference site without seepage (CTD-055: 44
◦
51'N, 32
◦
01'E, 76
m). Also two deep stations were sampled, a gas plume site (CTD-072: 44
◦
17'N, 35
◦
02'E, 1985 m) and a reference site without seepage to the west
