International Journal of Marine Science 2014, Vol.4, No.42, 1-11
4
and sulfide concentrations were measured in water
samples collected with Niskin bottles attached to the
CTD rosette.
At the same sites (Figure 1) where sediment cores for
benthos analyzes were collected, pore water was
extracted from sediments with Rhizons (type: CSS,
Rhizosphere Research Products), fixed with ZnAc for
total sulfide concentration analyzes and analyzed
according to the method of Cline (1969).
3 Results
3.1 Oxygen and sulfide concentrations in the water
column
Oxygen and sulfide concentrations measured in water
samples from the CTD rosette are plotted as a function
of water density (Figure 2). The disappearance of
oxygen and the onset of sulfide were found at a
density of approximately 1016 kg/m
3
. Oxygen
concentrations in the water column along the sediment
stations are shown in Figure 3. Further offshore, at
water depths between 150~300 m, the oxicline was
situated at 120 m depth and was characterized by
steep oxygen gradients. The onset of sulfide as
marked by the 1016 kg/m
3
density isoline was
between 150 and 200 m depth. Further inshore, at
water depths less than 150 m, the oxicline intersects
with the seafloor causing oxygen gradients to become
less steep. The bottom water at the sediments Station
285 (100 m depth, not shown in Figure 3) was fully
oxygenated, whereas the oxygen concentrations were
decreased to ~10 µmol/L at Station 243 (154 m). At
Station 224 (200 m) and 333 (200 m) the bottom water
was anoxic but not yet sulfidic, whereas at all other
stations (203, 204, 262, 263, 332; > 250 m) the bottom
water was sulfidic.
3.2 Sulfide concentrations in pore water
Sulfide concentrations in the sediment pore waters at
the different stations are displayed in Figure 4. In the
upper 30 cm of sediments from 100 m (Station 285)
and 150 m (Station 243) water depth no sulfide was
detected in the pore waters. At 200 m (Station 224,333)
water depth sulfide was occasionally presents in the
pore waters of the sediment. Sulfide concentrations
were variable here, however, in the two sampled
stations no free sulfide was found in the upper 5 cm of
the sediments. Only at 250 m (Station 250 m) water
depth sulfide was also detected close to the sediment
surface.
Figure 2 Compiled oxygen and sulfide concentrations in the
water sampled by the CTD rosette as a function of density. The
onset of the sulfidic layer is at 1016 kg m
-3
Figure 3 Oxygen concentrations in the water column along the
sediment sampling stations. Station numbers denote the stations
where sediment was sampled. The white lines represent density
isolines. The 1016 kg m
-3
isoline marks the onset of sulfide
Figure 4 Dissolved sulfide concentrations in pore waters along
the depth transect at the Bosporus outlet area of the Black Sea
4 Microscopic observations of animals
Using direct microscopic observations to test viability
of benthos, we found two ciliates species, one species
of free-living nematodes and one unknown organism,
alive and actively moving in sediments of Station 262
at 296 m water depth (Table 1). These observations
are further described in 4.1~4.3 (Figure 7, Figure 8;
Figure 10, Figure 11). This visual observation of
living organisms demonstrates that metazoa and
