Position of the top boundary of the hydrogen sulfide zone over the shelf edge of the Сrimea
Abstract
The purpose of the work is to discuss and identify the reasons of 2015-2019 rise of the upper boundary of the hydrogen sulfide zone above the edge of the Black Sea shelf. The position of the boundary is particularly important for the hydrochemistry of the Black Sea, since its rise to the surface could create a threat of the ecological catastrophe. Taking into account the intensive inter-basin water exchange, this may affect the state of the ecosystems of the Eastern Mediterranean and the Sea of Azov.
The paper discusses the position of the top boundary of hydrogen sulfide, identified by the 3 μM isosulfide, above the edge of the Crimean shelf, according to the data of 2015-2019 expeditionary studies of the Marine Hydrophysical Institute of the Russian Academy of Sciences. The position of the hydrogen sulfide boundary over the edge is of particular importance for the western shelf of Crimea, which is part of the northwestern shelf of the Black Sea (NWS). Probable leakage of hydrogen sulfide from the deeper part of the sea to the northwestern shelf can further aggravate the already less favorable ecological state of the shelf bottom waters, in which hypoxia regularly occurs in the warm season, sometimes culminating in fish kills.
Comparison of the averaged profiles of hydrogen sulfide concentration in terms of the scale of conditional density (σt) shows that the profiles over the southern shelf of the Crimea (to the east of the Khersones Cape) differ just slightly from those for the deeper part of the sea; the hydrogen sulfide zone appears on the isopycnic surface of σt = 16.15 kg/m3 in these areas. On the NWS of the Black Sea its occurrence is somewhat higher, i. e. at σt = 16.06-16.09 kg/m3. Among the profiles of 21 stations surveyed in 2015-2019 on the NWS, three stations were identified at which hydrogen sulfide appeared unexpectedly high at a depth of 85-90 m. The rise is exclusively related to water dynamics in early December 2017, since the stations were not distinguished in any way on the density scale. Their profiles were located side by side and intersected with the average profile along the NWS; like at most other offshore stations, their 3 μM isosulfide was located on the isopycnic surface of σt = 16.06-16.09 kg/m3. Five stations above the shelf edge were also identified, where the hydrogen sulfide occurred above the isopycnic surface of σt = 16.0 kg/m3. The analysis of hydrological situation showed that these stations were located on the periphery of anticyclonic eddies, which in all cases contributed to the ascent of the hydrogen sulfide-containing bottom water.
Keywords
Supporting agencies: The authors express their gratitude to the crew of the NIS Professor Vodyanitsky for their help in collecting field data within the shelf areas of the Crimean Peninsula. The work was carried out under the state task on the topic AAAA-A18-118020790209-9; on the topics 0555-2021-0004 Fundamental studies of oceanological processes that determine the state and evolution of the marine environment under the influence of natural and anthropogenic factors, using the methods of observation and modeling (code Oceanological processes) and 0555-2021-0005 Comprehensive interdisciplinary studies of oceanological processes that determine the functioning and evolution of ecosystems in the coastal zones of the Black and Azov seas (code Coastal Research); and financially supported by the Russian Foundation for Basic Research (project no. 18-05-80028).
About the Authors
S. I. Kondratev
Federal Research Center "Marine Hydrophysical Institute of RAS”
Russian Federation
Russian Federation
Senior Scientific Researcher, Ph.D. in Chemistry, Department of Marine Biogeochemistry, Department of Oceanography.
Sevastopol.
A. V. Masevich
Federal Research Center "Marine Hydrophysical Institute of RAS”
Russian Federation
Russian Federation
Junior Scientific Researcher, Department of Marine Biogeochemistry, Department of Oceanography.
Sevastopol.
V. N. Belokopytov
Federal Research Center "Marine Hydrophysical Institute of RAS”
Russian Federation
Russian Federation
Head of the Oceanography Department, D.Sc. in Geography, Department of Marine Biogeochemistry, Department of Oceanography.
Sevastopol.
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Review
For citations:
Kondratev S.I., Masevich A.V., Belokopytov V.N. Position of the top boundary of the hydrogen sulfide zone over the shelf edge of the Сrimea. Vestnik Moskovskogo universiteta. Seriya 5, Geografiya. 2022;(3):97-107. (In Russ.)
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