Environmental Engineering Reference
In-Depth Information
smaller in the central part of the Black Sea because of the dome shape structure
of the pycnocline. As a result there is a smaller total inventory of oxygen in the
upper water column. Thus, an equal flux of sinking organic matter moves the
oxycline and the upper boundary of the suboxic zone upward more effectively
in the central part of the sea. In addition, the central part of the Black Sea is
considered to be more biologically productive, as compared to the periphery of
the deep part of the sea, especially in the early spring when blooms occur [48,
76]. This is another factor that results in a thicker suboxic zone in the central
gyre area. The thickness of the suboxic zone is larger in the central area because
the exported carbon flux has a greater impact in that region.
Figure 12.
Regional variability of the oxygen and sulfide distributions. a) distributions in the
central gyre, NW and NE regions b) distributions in the SW region influenced by the Bosporus
Plume.
More dramatic differences are observed in the southwestern part of the
Black Sea. This is the region influenced by the Bosporus Plume and is an area
of intensive redox processes in a multi-layered oxic/anoxic transition zone.
The suboxic zone cannot be traced into this region because of the intrusion of
the oxygenated Bosporus plume waters. In this region, dissolved manganese is
actively oxidized by the injected oxygen [58]. Maximum particulate manganese
concentrations are 3 to 7 times larger than those in the central and northwestern
parts of the sea. The onset of dissolved manganese in the SW region is moved
deeper from its usual density of
σ
θ
= 15.8 - 15.9 to a density of about
σ
θ
=
16.2. The onset of sulfide is moved deeper from
σ
θ
= 16.1 - 16.2 to about
σ
θ
=
16.4 and it usually exhibits an interleaved, multi-layered oxic-suboxic-sulfidic
structure.
