The Black Sea biological viability area has been reduced by a third and confronted with serious environmental problems

Surrounded by Turkey and Russia etc.Black SeaIs known as the huge sea connecting Europe and Asia in the Utsumi that leads to the Mediterranean Sea, the Aegean Sea and others. The Black Sea is divided into upper and lower parts such as surface water with low salt concentration and deep water with high salt concentration and high concentration of hydrogen sulfide because it is Utsumi, and the feature that the sea looks black by virtue of deep water with many iron sulfide However, in recent years, we know that we are faced with the environmental problem that the area where living things can survive in surface waters drastically decreases.

The Black Sea has lost more than a third of its habitable volume - Science Bulletin
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A research team at the University of Liege in Belgium surveyed the living creatures in the Black Sea. In the survey, "Surface water" with high oxygen concentration and living organisms can survive, except for oxygen concentration, low concentration of hydrogen sulfide, iron sulfide which causes the sea to darken due to high concentration of hydrogen sulfide, and anaerobic bacteria etc. The depth of the boundary of "deep water" was investigated, which was 140 m deep in 1955, compared to the depth of 90 m in 2015, the surface water was reduced by 40% I understood that it was done.

In the Black Sea, rivers such as the Danube are the main sources of water. Hydrogen sulfide is generated and iron sulfide and the like are present in high concentrations and surface water to which fresh water is supplied from rivers is lower than that of deep water with high density and it is as deep as the "water and oil" Water and surface water are divided into two layers. Surface water on top of deep water not only has low salt concentration, but because there is a change of water, rich in oxygen, and more easily reachable by sunlight, the environment where living things survive is in place. On the other hand, it is not an exaggeration to say that the deep water is an environment where living things are hard to survive, so it can be said that a significant decrease in the surface water part directly leads to a large decrease in the living area of ​​organisms in the Black Sea.


Dr. Arthur Cappett of the University of Liège said, "Since the Black Sea is Utsumi where the basin is completely closed, there is a limit in the vertical direction of the living space of the creatures.This restricted survival area is affected by changes in the external environment Although it is brought about, the pace of decrease in the survival area is rapid ", I am concerned about the magnitude of the impact on the ecosystem.

The research team at Liege thinks that there are two factors as to why the surface water part of the Black Sea is decreasing sharply. One of them is "eutrophication"Problem of. During the former Soviet era in Russia a large farm was developed and cattle were breeding. Along with the development of the farm, a large amount of fertilizer was introduced into the soil and a large amount of organic waste such as cattle feces occurred, but at that time, consideration to the environment was not made at all and these ingredients It flows into the Black Sea through major rivers, causing eutrophication problems. Due to the algae that occurred in large quantities, it is thought that the problem of the oxygen concentration of the surface water sharply decreasing occurred.

And another cause is "Global warming". It is thought that the oxygen concentration in the surface water saturates and the oxygen can not be held because the seawater temperature has risen due to global warming. By the way, it seems that the decline of marine oxygen concentration accompanying global warming is becoming a global environmental problem not only in Black Sea.

The research team at the University of Liège thinks that environmental problems occurring in the Black Sea can not avoid inevitably bringing significant changes to the ecological and human economic activities. It is said that the balance of the food chain in the surface water has collapsed due to the lowering of the oxygen concentration of surface water and the explosive increase of phytoplankton generated from deep water. As for the fishing that is popular in the Black Sea, it is known that the catch is 376,000 tons in 2013, which is less than half of that in the whole Mediterranean Sea, and the economic activity is also affected I will.