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According to expeditionary and coastal monitoring studies carried out in 2019 and 2020, we analyzed the structure features and temporal variations of colored dissolved organic matter concentration in the Omega Bay field. It is shown that the structure of the analyzed parameter field in the Omega Bay is formed as a result of interactions in the system of local anticyclonic circulation that involves both Sevastopol seaside water, where its concentration is close to the natural normal, and water of the isolated apex part of the bay that experiences anthropogenic pressure. The field under consideration is well stratified in the apex of the bay and is characterized by poorly pronounced vertical stratification in the central and open marine part of the bay. The response to atmospheric and marine processes is traced in the field of colored dissolved organic matter concentration during the summer of 2020. It was revealed that rains and polluted water advection from the sea were accompanied by a noticeable increase in the concentration of the analyzed substance in the beach area of the bay. The opposite effect was observed during upwelling. [ABSTRACT FROM AUTHOR]

The article presents the results of geophysical and geomorphological works on the western shelf of the Crimean Peninsula (Yevpatoriya–Balaklava). The sedimentary sequence structure, seafloor topography, and paleogeographic reconstructions of the formation conditions of the western shelf in the Late Pleistocene–Holocene are considered. Geoacoustic profile analysis aided in identifying the main shelf morphostructures; a brief description is presented. The abrasion–accumulative complex is identified, which consists of the abrasion platform and associated accumulative clinoform, the formation of which is related to the coastline of Late Pleistocene Black Sea regression to depths of about 90 m, traced from Yevpatoriya to Yalta. On the shelf of Kalamita Bay, fragments of a drowned river network and coastal accumulative landforms such as bars were studied. [ABSTRACT FROM AUTHOR]

The results of studying the geological and archaeological traces of the strong earthquakes on Cape Zyuk where the ancient settlement existed from the turn of the 6th to the 5th centuries B.C. to the first-third–middle of the 6th century A.D. are presented. The detailed knowledge gained on this monument allowed us to compile the timeline of the strong earthquakes for the past 2500 years. The detection of the seismotectonic deformation of the Late Holocene sediments indicates that the rupture of the source of a strong earthquake at Cape Zyuk extended to the surface. The dating of this event is constrained by the upper age of the second half of the 4th century B.C. to the beginning of the third century B.C. The previous event is dated to before the turn of the 6th–5th centuries B.C. Besides these events, there were presumably another four earthquakes in 63 B.C., before the second half of the 4th century B.C., in the first third to the mid-6th century A.D., and in the 18th century. Presumably Cape Zyuk was struck by four or five strong earthquakes during the past 2500 years. The lack of information about the earthquakes between the 6th and 18th centuries, i.e., during more than a 1000-year period, can probably be related to both the long period of quiescence between seismic activations and to the incompleteness of the collected data. [ABSTRACT FROM AUTHOR]

The study of hydrocarbons has shown that their content in the surface water of Feodosiya Gulf varies greatly (from 11 to 179 µg/L) and sometimes exceeds the maximal permissible concentration (MPC) for oil hydrocarbons. Their greatest concentrations were revealed in 2016. Alkanes were of mixed autochthonous and allochthonous origin. Weathered oil hydrocarbons were revealed only in some samples. The content of hydrocarbons in bottom sediments depended on their granulometric composition, and they were dominated by terrigenous alkanes. Oil and pyrogenic hydrocarbons were revealed as components of polycyclic aromatic hydrocarbons. In an open part of the Black Sea to the south of the Crimean Peninsula, the content of hydrocarbons in the surface water and bottom sediments was at the level of background concentration, and they were dominated by terrigenous homologues. [ABSTRACT FROM AUTHOR]

Hydroacoustic techniques were used for detection and mapping of gas jet areas in the coastal regions of the Crimean Peninsula. Gas jet areas in the bays Laspi, Khersones, and Kazach'ya were chosen for detailed microbiological investigation. The first type of gas jets, observed in the Laspi Bay, was probably associated with discharge of deep thermogenic methane along the faults. Methane isotopic composition was characterized by δC of-35.3‰. While elevated rates of aerobic methane oxidation were revealed in the sandy sediments adjacent to the methane release site, no evidence of bacterial mats was found. The second type of gas emission, observed in the Khersones Bay, was accompanied by formation of bacterial biofilms of the ' Thiodendron' microbial community type, predominated by filamentous, spirochete-like organisms, in the areas of gas seepage. The isotopic composition of methane was considerably lower there (-60.4‰), indicating a considerable contribution of modern microbial methane to the gas bubbles discharged in this bay. Activity of the third type of gas emission, the jets of the Kazach'ya Bay, probably depended directly on modern microbial processes of organic matter (OM) degradation in the upper sediment layers. The rates of sulfate reduction and methanogenesis were 260 and 34 μmol dm day, respectively. Our results indicate different mechanisms responsible for formation of methane jets in the Laspi Bay and in the coastal areas of the Heracles Peninsula, where the bays Kazach'ya and Khersones are located. [ABSTRACT FROM AUTHOR]