by Yuri SUPRUNENKO, Cand. Sc. (Geogr.), RAS Institute of Geography
Oxygen deficiency (hypoxia) in polluted bodies of water has become a common public concern in practically all of the industrially developed countries. How does this new threat affect the World Ocean, if at all?
Today we have no clear evidence of any growing oxygen deficiency in the World Ocean and of its poisoning with hydrogen sulfide. Why? Because appropriate observations are few and rare. As for the Black Sea, however, scientists have been monitoring the distribution of hydrogen sulfide in its water for many decades now * According to their findings, it is only the surface layer of water from 150 to 200 meters deep that contains enough oxygen to sustain all of the Black Sea flora and fauna. But the bulk of water in that sea has levels of hydrogen sulfide incompatible with any common life forms. This being so, a number of projects have been proposed for improving the situation. One suggests building a dam across the Bosphorus which could reduce the size of the hydrogen sulfide zone and cause its ultimate disappearance-just as was the case in the distant geological past when the dropping level of the ocean in the Ice Age practically closed the strait.
Other projects for the Black Sea involve its hydrological regime. According to calculations, by obstructing the Low Bosphorus current it would become possible to intensify the vertical intermixing of sea water thus increasing the rate of exchange between the upper (oxygenated) and lower (hydrogen sulfide) zones. This should lead, sooner or later, to the extinction of the latter. But attractive as it may appear, this project is not an ideal solution because according to some experts the main mechanism of water circulation in the Black Sea is connected not with the water exchange through the Bosphorus, and a gradual displacement of water upwards, but with the atmosphere.
There are several more "hydrogen sulfide" zones in the World Ocean, such as the ... Читать далее