Anaeroconture of the Black Sea

The work is devoted to the issue of the allocation of a new contour biotope in the Black Sea. Currently, in hydrobiology, it is customary to distinguish the following contour biotopes or contact zones of the sea: aerocontour, psammocontour, lithocontour, pelocontour, potamocontour (Zaitsev, 2012, 2015), which describe the ecological structure of any reservoir except for the Black Sea. This is due to the fact that most of the deep-water area of this water basin does not have a peloconture with higher forms of life due to hydrogen sulfide in its depths. This biotope exists is only in coastal shelf areas up to depths of 150-200m, where there is still oxygen. Until the end of the last century, it was believed that the Black Sea had only oxygen and hydrogen sulfide zones, with a mixing layer (or C-layer) between them. However, at the beginning of this century, a revolutionary discovery was made in hydrochemistry (Konovalov, Murray, 2001; Konovalov et al., 2005): it turned out that the C-layer does not exist and that the oxygen and hydrogen sulfide layers of water are separated by a special water mass where there is neither oxygen nor hydrogen sulfide. It turned out that this water mass (called the Suboxic layer) has a thickness of about 30-50 m, characteristic physicochemical properties and a certain history of origin (Konovalov et al., 2005). Like any water mass in the sea, it is a biotope that in hydrobiology does not yet have a name, is poorly described and its role in the ecosystem is insufficiently studied. However, there is already evidence that it plays an extremely important role in the ecosystem of the Black Sea because clusters of specific hydrobionts form on its borders and intensive chemosynthesis occurs in it, comparable in production with the photic zone (Polikarpov et al., 1990). This biotope is an obvious contour biotope, the opposite of the aeroconture, which is in contact with the oxygen environment. It is located on the border with anoxic layer and therefore the author called it the “anaerocontour” of the Black Sea. Based on the generalization of existing data and the results of his own research, the author of this work for the first time provides a generalized description of the structural and functional characteristics of this contour biotope and describes its role in the functioning of the ecosystem of the Black Sea. The results of this work are of fundamental interest for understanding biological processes in extreme conditions and their impact on long-period changes in the ecosystem of the Black Sea.