19 The Black Sea
F. VASILIU
19.1 Hydrological and Chemical Characterization
of the Black Sea
In order to understand the changes to the Black Sea ecosystems caused
by human impact especially during the past 20 - 30 years, it is necessary
to describe in short the physical and chemical peculiarities for which the
Black Sea is also sometimes named the "Unicum hydrobiologicum".
The Black Sea is an intercontinental basin, connected with the Mediterranean and the ocean only by the narrow Bosphorus Straits. Geologically, the Bosphorus is a tectonic ditch, only 250 to 550 m wide and 27.5
to 120 m deep. Two bodies of water flowing in opposite directions are
separated from each other by a sharp salinity gradient of approximately
18 PSU in the surface layer to 37 -40 PSU in the water below. The
boundary layer slopes down from about 10 m depth in the south to 40 m
in the north, depending on the volumes of flow and on the metereological conditions.
The geomorphological "threshold" features of the Bosphorus Straits
are a barrier for: (1) the influence of Mediterranean tidal fluctuations on
the Black Sea; (2) the exchange of water between the Mediterranean and
the Black Sea; and (3) the migration of plants and animals.
Another specific feature of the Black Sea is its role as a recipient of a
drainage area of about 2.4 million km 2 , covering 13 different countries.
The hydrological balance is shown in Table 19.1. River discharges
contribute about 54% of the total input, however, they represent only
0.075% of the 537 000 km 3 volume of the Black Sea. The brackish
character of the so-called Pontic Basin must also be related to the origin
of this sea, which, in fact, is a mixture of three different water bodies:
Complexui Muzeal de Stiinte ale Naturii-Constanta, Bul. Mamaia nr. 255, 8700 Constanta,
Romania
Ecological Studies, Vol. 123
Schramm/Nienhuis (eds) Marine Benthic Vegetation
© Springer-Verlag Berlin Heidelberg 1996
F. VASILIU
19.1 Hydrological and Chemical Characterization
of the Black Sea
In order to understand the changes to the Black Sea ecosystems caused
by human impact especially during the past 20 - 30 years, it is necessary
to describe in short the physical and chemical peculiarities for which the
Black Sea is also sometimes named the "Unicum hydrobiologicum".
The Black Sea is an intercontinental basin, connected with the Mediterranean and the ocean only by the narrow Bosphorus Straits. Geologically, the Bosphorus is a tectonic ditch, only 250 to 550 m wide and 27.5
to 120 m deep. Two bodies of water flowing in opposite directions are
separated from each other by a sharp salinity gradient of approximately
18 PSU in the surface layer to 37 -40 PSU in the water below. The
boundary layer slopes down from about 10 m depth in the south to 40 m
in the north, depending on the volumes of flow and on the metereological conditions.
The geomorphological "threshold" features of the Bosphorus Straits
are a barrier for: (1) the influence of Mediterranean tidal fluctuations on
the Black Sea; (2) the exchange of water between the Mediterranean and
the Black Sea; and (3) the migration of plants and animals.
Another specific feature of the Black Sea is its role as a recipient of a
drainage area of about 2.4 million km 2 , covering 13 different countries.
The hydrological balance is shown in Table 19.1. River discharges
contribute about 54% of the total input, however, they represent only
0.075% of the 537 000 km 3 volume of the Black Sea. The brackish
character of the so-called Pontic Basin must also be related to the origin
of this sea, which, in fact, is a mixture of three different water bodies:
Complexui Muzeal de Stiinte ale Naturii-Constanta, Bul. Mamaia nr. 255, 8700 Constanta,
Romania
Ecological Studies, Vol. 123
Schramm/Nienhuis (eds) Marine Benthic Vegetation
© Springer-Verlag Berlin Heidelberg 1996