The Black Sea

The Catchment area – Black Sea drainage basinwww.salix.od.ua

Kerch Strait

Strongly stratified:- its deep water is much more saline than its surface water the surface water is dilute because of inflow of freshwater from rivers (the Danube, but also the Dnieper, Bug and the Dniester). the deep water is more saline because of inflow of seawater from the Aegean Sea through the straits.

Because of the contrast in density between surface and deep water, in the Black Sea THERE IS NO vertical mixing.

NO VERTICAL MIXING of waters below 200 m depth lack of O2 in the deep water (enormous influence on life in the sea).

The decay of sinking organic matter consumes all available O2.

The Black Sea – the biggest anoxic water body in the world!

Anoxic waters allow the presence of methane, hydrogen sulfide & ammonia in the deep waters.

There can be also found iron (Fe), which in the presence of H2S can form iron sulfides like pyrite (FeS2).

Summary

• The Black Sea has 2 distinct water layers:1. Lighter upper layer (0 – 200 m depth): salinity = 18 ‰, temp. = 12-

14 ⁰C.2. Heavier down layer (200 m depth to the seabed): salinity = 22 ‰,

constant temp. = 9⁰C.

• In the entire Black Sea at a depth greater than 200 m (= 87 - 90 % of the waters) there is a permanent H2S and O2 is completely absent.