Influx of Streaming Methane into Anoxic Waters of the Black Sea Basin

Oceanology - Based on long-term data on the spatial distribution and fluxes of streaming (bubbling) methane in the Black Sea, the study considers various types of streaming gas emissions...     

Sulfur and iron speciation in surface sediments along the northwestern margin of the Black Sea

The speciation of sedimentary sulfur (pyrite, acid volatile sulfides (AVS), S⁰, H₂S, and sulfate) was analyzed in surface sediments recovered at different water depths from the northwestern margin of the Black Sea. Additionally, dissolved and dithionite-extractable iron were quantified, and the sulfur isotope ratios in pyrite were measured. Sulfur and iron cycling in surface sediments of the northwestern part of the Black Sea is largely influenced by (1) organic matter supply to the sediment, (2) availability of reactive iron compounds and (3) oxygen concentrations in the bottom waters. Biologically active, accumulating sediments just in front of the river deltas were characterized by high AVS contents and a fast depletion of sulfate concentration with depth, most likely due to high sulfate reduction rates (SRR). The δ³⁴S values of pyrite in these sediments were relatively heavy (−8‰ to −21‰ vs. V-CDT). On the central shelf, where benthic mineralization rates are lower, re-oxidation processes may become more important and result in pyrite extremely depleted in δ³⁴S (−39‰ to −46‰ vs. V-CDT). A high variability in δ³⁴S values of pyrite in sediments from the shelf-edge (−6‰ to −46‰ vs. V-CDT) reflects characteristic fluctuations in the oxygen concentrations of bottom waters or varying sediment accumulation rates. During periods of oxic conditions or low sediment accumulation rates, re-oxidation processes became important resulting in low AVS concentrations and light δ³⁴S values. Anoxic conditions in the bottom waters overlying shelf-edge sediments or periods of high accumulation rates are reflected in enhanced AVS contents and heavier sulfur isotope values. The sulfur and iron contents and the light and uniform pyrite isotopic composition (−37‰ to −39‰ vs. V-CDT) of sediments in the permanently anoxic deep sea (1494 m water depth) reflect the formation of pyrite in the upper part of the sulfidic water column and the anoxic surface sediment. The present study demonstrates that pyrite, which is extremely depleted in ³⁴S, can be found in the Black Sea surface sediments that are positioned both above and below the chemocline, despite differences in biogeochemical and microbial controlling factors.     

Variability of Particulate Organic Phosphorus in the Northwestern Part of the Black Sea

Based on long-term (1985–1995) monitoring data, the paper considers the peculiarities of seasonal variability in the spatial and vertical distribution of particulate organic phosphorus (Р_POM) in the surface layer and in the photosynthetic zone in the northwestern Black Sea. Regression equations, experimental data, and satellite observations for the chlorophyll a concentration allowed us to evaluate the seasonal longterm (1979–1995) variability in Р_POM in the surface layer and photosynthesis zone. The ratios of the concentrations of particulate organic carbon, nitrogen, phosphorus, and chlorophyll a are calculated and statistical estimates of seasonal changes in the Р_POM in the areas with different degrees of influence of river runoff and water of open seas are obtained. The consistency of intra-annual changes in the concentrations of Р_POM, chlorophyll a, and phytoplankton biomass is shown, which indicates the role of phytoplankton in the formation of Р_POM and in its intra- and interannual variability in the northwestern part of the sea. It is shown that long-term seasonal variations in Р_POM and related changes in the concentration of chlorophyll a depend on the variability of bulk river runoff, the extent of its abundance in the northwestern shelf, and regional hydrometeorological conditions.     

Occurrence and Distribution of Cetaceans in the Northeastern Part of the Black Sea

Oceanology - Studies of Black Sea cetaceans were carried out in September 2018 (11 days, 799 km of the survey route) and June 2019 (12 days, 1174 km of the survey route). The research vessel...     

Internal Waves in the Shelf Zone and near the Shelf Edge in the Black Sea

The data accumulated by a measuring complex equipped with a gradient-distributed temperature sensor in the course of towing in the shelf zone near the South Coast of the Crimea and in the region where the flow of the Rim Current crosses the shelf edge are used to analyze the energy and space characteristics of internal waves formed when the flow runs through the shelf edge and to study the process of their propagation both to the coast and to the open part of the sea.     

Specific Features of the Propagation of Tsunamis in the Northwest Part of the Black Sea

We perform the numerical analysis of the propagation of tsunamis in the Black Sea from the zones of seismic generation located to the south of the Crimea and in the northwest part of the sea. It is shown that the tsunamis induced by earthquakes in the Crimean seismic zone are entrapped by the nearest part of the shelf and do not result in noticeable oscillations of level in the northwest part of the sea. This enables us to explain the absence of manifestations of tsunamis in 1927, 1939, and 1966 near Odessa. The tsunami waves generated by earthquakes in the northwest part of the sea are characterized by the directivity of their propagation. The wave height is maximum in the areas corresponding to the north and east directions of propagation. Hence, the north coast of the sea and the Kalamit Bay (Crimean Peninsula) are characterized by elevated tsunami hazard for earthquakes occurring in the northwest part of the Black Sea. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 46–53, November–December, 2005.     

Long-Term Variability of the Dissolved Oxygen Content and Water Temperatures in the Upper Layer of the Black Sea

Oceanology - Based on the archival oceanographic databank of the Institute of Natural and Technical Systems, the annual and interannual variability was analyzed for the dissolved oxygen content and...     

Vertical transport in the Black Sea

Investigations of the vertical exchange coefficientK _z , considering turbulent and advective transport, are summarized. The values ofK _z are determined from the climaticT, S characteristics, heat and salinity fluxes, and the rate of the low-Bosporus water transformation over the entire Black Sea water column; namely, in the upper mixed layer, the active layer, the cold intermediate layer, the halocline, and in the deep and near-bottom waters. A characteristic for annual fluctuations ofK _z in the active layer is given; it is noted that the coefficient tends to grow in transit from the centre of the cyclonic gyre toward its periphery.Translated by V. Puchkin.     

Spatiotemporal Variability of Suspended Particulate Matter in the Surface Layer of the Open Part of the Black Sea

Oceanology - Based on long-term measurements of the concentration of total suspended particulate matter (TSM), particulate organic carbon, chlorophyll a, and the water transparency index for...     

Numerical Modeling of Meteorological Sea Level Oscillations in the Black Sea

Oceanology - To study the features of short-period meteorological sea level oscillations, adaptation of the numerical Princeton Ocean Model (POM) to the Black Sea conditions was performed. The...     

Variations of the Black Sea level

The annual course of sea level at various sections of the coastline is derived from the interpretation of empirical observations. The paper evaluates the effect of continental discharge, atmospheric pressure, and density distribution upon the local sea level vacillations, and the tendency to multi-annual sea level variability is determined. During this century, against the background of broad spectral oscillations, the Black Sea mean level is rising at the rate of 1.6 mm year⁻¹. The paper examines Man's impact upon the erosion of the shore and the departure of the coastline. Translated by Vladimir A. Puchkin.     

Modelling subsurface dynamics in the Black Sea

Dependency of major hydrophysical/chemical features of highly stratified basins on density surfaces in the vertical makes isopycnic models an attractive tool for simulating the dynamics of marginal marine environments such as the Black Sea because of the ability of these models to restrict vertical transport to some desirable degree. In the present work the seasonal variations of the subsurface dynamics of the Black Sea are investigated using an isopycnic model. Particular attention is given to the interfaces of the Cold intermediate layer and Suboxic layer and finally, the deep layer circulation in the basin is studied. It appears that although the depth range of the base of the Cold intermediate layer and the lower Soboxic layer interface do not change seasonally, their horizontal distribution is defined by the upper layer dynamics of the basin. Cyclonic surface circulation diminishes with increasing depth and the deep layer circulation is characterised by an anti-cyclonic rim current driven by density gradients created from river runoff and the influx of Mediterranean water.     

Methane gas Seeps Along the Oxic/Anoxic Gradient in the Black Sea: Manifestations, Biogenic Sediment Compounds and Preliminary Results on Benthic Ecology

Abstract. Sediment parameters (grain size, organic content, chloroplastic pigments, Adenylates, Potential hydrolytic activity and electron transport system activity) and benthic biota were studied in methane seep area south-west of the Crimean Peninsula in the Black Sea over a depth range from 60 to 260m. A control transect with similar depths was performed in an adjacent nonseep area. Methane seepage in this region occurs from 35 to ˜ 85m depth, passing the oxic anoxic interface zone at 130 to 180m. The methane seep areas were characterized by abundant carbonate precipitates which occurred in various shapes from small, flat structures to tall chimneys with increasing anoxia. The carbonates were associated with distinct bacterial mats. Most of the measured biochemical parameters in the sediment were quite similar in the seep and nonseep areas. The content of organic matter was higher and grain size was more uniform in the nonseep areas. However, the seep areas were charaterized by highter proportions of the larger fauna (size classes 0.5–1 mm and ≥ 1mm) as well as increased total numbers of benthic fauna in the suboxic and upper anoxic zone. The animals did not show any seep-specific adaptations. In addition to methane seepage, highly variable hydrochemical and sedimentary conditions on the lower shelf and upper slope may also play an important role in structuring the composition and distribution of the benthic fauna.     

Joint Soviet-Turkish expedition in the Black Sea

The hydrological and hydrochemical structures of the upper 300 m water column of the Black Sea in autumn 1988 have been studied. Regularities in the distribution of the physico-chemical characteristics in the zone of interaction between aerobic and anaerobic waters as well as the topography of the H₂S zone boundary and its connection with a certain density gradient have been found.Translated by Mikhail M. Trufanov.     

Components of Oil Pollution in Water and Bottom Sediments of the Northeastern Part of the Russian Black Sea Region

Oceanology - The results of studies of oil pollution (by the sum of hydrocarbons and resinous substances) of water and bottom sediments in the northeast Black Sea in spring and autumn are...     

Suboxic and Anoxic Conditions of Deep Waters in the Gdansk Basin of the Baltic Sea

Oceanology - Long-term variability of the concentrations of oxygen and hydrogen sulfide in deep waters of the Gdansk Basin of the Baltic Sea for the last 25 years was considered. The dependence of...     

Modelling of the Black Sea seasonal variability

The paper discusses the results of numerical experiments on response of the Black Sea to the ‘real’ (mean monthly) atmospheric forcing. A new version of the multi-layer quasi-isopycnic model is applied which does not use the rigid-lid approximation and allows for a salt flux through the sea surface. Ways of obtaining quantitative agreement between the calculated data due only to the external forcing, without invokingin situ temperature/salinity observations are suggested. Translated by Vladimir A. Puchkin.