Scientists studying the Black Sea water area agree that the ecological state of this reservoir can be defined as unfavorable. Researchers are greatly concerned about the huge amount of hydrogen sulfide concentrated in the area below the 150-200 m mark.
Hydrogen sulfide
For the first time, the Russian geologist Nikolai Andrusov, who organized an expedition to study this reservoir in 1890, spoke about the deposits of hydrogen sulfide in the Black Sea. This chemical compound is a flammable, colorless, toxic gas with a characteristic smell of rotten eggs, which is formed by rotting proteins and the absence of oxygen.
According to the latest expert estimates, the total amount of hydrogen sulfide dissolved in the Black Sea waters exceeds 3 billion tons and occupies 90% of their volume, which means that the entire biosphere of the sea is concentrated in only 10% of its surface layer.
This is not the limit, since, according to oceanographer Anatoly Ryabinin, over the past decades, periods of an increase in the level of hydrogen sulfide to the threatening mark of 75 m have been observed more than once.
Hydrogen sulfide, which kills all living things, is contained not only in the Black Sea, but only here its volume is so great that, according to the Kerch oceanographer Vladislav Shlyakhov, there is practically no life deeper than 100-150 m.
According to Sergei Konovalov, director of the Marine Hydrophysical Institute of the Russian Academy of Sciences, in the deep layers of the Black Sea, the level of hydrogen sulfide is slowly but surely increasing, which, gradually rising, is approaching the water surface.
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Layers of the Black Sea
This ecological situation is due to the unusual structure of the Black Sea - with a relatively small area, it has a rather great depth, divided into several layers, the water of which practically does not mix.
The scanty surface layer of this water area (100 m depth), which is called the cold boundary layer, is practically fresh water of river origin saturated with oxygen and nutrients. The next 100 m is characterized by a decrease in the oxygen level and an increase in salt concentration, and below 200 m there is a complete lack of oxygen and the presence of heavy salt water entering the Black Sea through the Bosphorus Strait and the recently discovered underwater river.
Stratification, or stratification of the Black Sea water area in terms of density, temperature and salinity, creates an obstacle for vertical water exchange and rapid penetration of oxygen to the depth of the reservoir. Some scientists assure that surface water reaches the Black Sea bottom for hundreds of years, and that is why below the 200 m mark, the sea is a lifeless reservoir filled with hydrogen sulfide, the largest accumulation of which is observed at a depth of 2 km - 9.6 mg / l of water.
Where does oxygen go?
Most of the oxygen enters the surface layer of the Black Sea from the air, and some is formed in the photic zone (illuminated water column) during photosynthesis of planktonic algae.
All oxygen in the water is used to support the life of the Black Sea fauna, represented by dolphins, various planktonic crustaceans, fish, jellyfish, crabs that do not live deeper than 100 m.
Where does hydrogen sulfide come from?
According to the geological version, the accumulation of hydrogen sulfide in the Black Sea is facilitated by insignificant underwater volcanic activity, during which gases from tectonic faults of the earth's crust enter the water.
However, most scientists, including the American Lee Camp, believe that hydrogen sulfide in the Black Sea is formed due to the activity of saprotroph bacteria, which, being anaerobic organisms, inhabit the deep layers and the bottom of the reservoir.
Taking part in the decomposition of dead organic matter, that is, being catalysts of the decay process, they form a substance from the sulfates contained in the sea soil, which, when combined with sea water, is converted into hydrogen sulfide.
Anthropogenic factors
A significant contribution to the destruction of the clean water of the Black Sea is made by people who, by their vigorous activity, have a negative impact on the ecological state of the water area.
The deepening of the seabed, the construction of breakwaters, the laying of oil pipelines, the extraction of minerals, are destroying the fragile ecosystem of this reservoir, which suffers from an overabundance of pollutants discharged into its waters.
Untreated domestic and industrial sewage, as well as streams of agricultural fertilizers rushing into the sea, reduce the transparency of the water and increase the nutritional value of the environment.
A cloudy surface reduces the carrying capacity, which means that the surface layer of water feels an insufficient supply of solar energy necessary for photosynthesis. For this reason, in 2003, in the Black Sea, the unique Zernov field, consisting of an accumulation of red alga phyllophora, growing on an area of 11 thousand km2, completely died.
Belgian researchers from the University of Liege see the reason for the deterioration in water quality and a decrease in the depth of oxygen penetration in the Black Sea in the release of huge amounts of nitrogen and phosphorus compounds.
The aquatic environment oversaturated with fertilizers contributes to the active growth of weed phytoplankton and the spread of thickets of primitive filamentous algae, the organic remains of which in huge quantities settle on the bottom, where bacteria generating hydrogen sulfide take over.
Effects
According to oceanologist Alexander Gorodnitsky, the threat posed by the waters of the Black Sea should not be underestimated. Even if mankind suddenly changes its mind and stops polluting the reservoir with waste of its life, nature can present an unpleasant surprise. The thing is that this water area is located in a seismically active region, and any powerful earthquake can provoke an explosion of poisonous hydrogen sulfide and the release of concentrated sulfuric acid into the atmosphere, which will destroy life in the coastal region and spill acid rain in other areas.
Solution to the problem
To prevent a negative scenario of the development of events, scientists put forward different solutions to the problem.
Researchers from Kherson call for the use of hydrogen sulfide as an alternative fuel: for this they propose to lower an 80-meter pipe vertically into the sea and, pumping air out of it, create a pressure difference, which will cause a fountain of the required gas to flow out of the water.
Other scientists propose to reduce the concentration of hydrogen sulfide in the Black Sea through artificial aeration, that is, to lower pipes into the lower layers of the water area and let fresh water through them, the density of which is less than that of sea water.
Methane
In addition to hydrogen sulfide, in the "bowels" of the Black Sea lies the explosive gas methane, which in 1927 provoked an amazing phenomenon - the burning of water.
Burst out from the vibrations caused by the Crimean earthquake, methane ignited from a lightning strike and filled the air with the disgusting smell of rotten cabbage and eggs.
Ashkhen Avanesova