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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 followed a survey route off the Caucasian coast of the Black Sea from Anapa to Adler at a distance of up to 165 km from the coast. There were 103 sightings of cetaceans (548 individuals) in 2018 and 347 sightings (1280 individuals) in 2019. Three species were recorded: common dolphin, bottlenose dolphin, and harbor porpoise; their ratios were 78.1 : 20.8 : 1.1 in 2018 and 90.1 : 7.1 : 2.8 in 2019. Common dolphins were sighted everywhere; in June, they were encountered more frequently in the coastal water area; in September, in the open sea. This was probably preconditioned by the availability of prey. Bottlenose dolphins and harbor porpoises performed short-distance seasonal migrations and preferred to remain in local coastal habitats.

Several Arctic marine mammal species are predicted to be negatively impacted by rapid sea ice loss associated with ongoing ocean warming. However, consequences for Arctic whales remain uncertain. To investigate how Arctic whales responded to past climatic fluctuations, we analysed 206 mitochondrial genomes from beluga whales (Delphinapterus leucas) sampled across their circumpolar range, and four nuclear genomes, covering both the Atlantic and the Pacific Arctic region. We found four well-differentiated mitochondrial lineages, which were established before the onset of the last glacial expansion ~110 thousand years ago. Our findings suggested these lineages diverged in allopatry, reflecting isolation of populations during glacial periods when the Arctic sea-shelf was covered by multiyear sea ice. Subsequent population expansion and secondary contact between the Atlantic and Pacific Oceans shaped the current geographic distribution of lineages, and may have facilitated mitochondrial introgression. Our demographic reconstructions based on both mitochondrial and nuclear genomes showed markedly lower population sizes during the Last Glacial Maximum (LGM) compared to the preceding Eemian and current Holocene interglacial periods. Habitat modelling similarly revealed less suitable habitat during the LGM (glacial) than at present (interglacial). Together, our findings suggested the association between climate, population size, and available habitat in belugas. Forecasts for year 2100 showed that beluga habitat will decrease and shift northwards as oceans continue to warm, putatively leading to population declines in some beluga populations. Finally, we identified vulnerable populations which, if extirpated as a consequence of ocean warming, will lead to a substantial decline of species-wide haplotype diversity.

The OCP and PCB contents in the tissues of beluga whales (Delphinapterus leucas) from the Russian Arctic have been studied for the first time. Skin and subcutaneous adipose tissue samples collected in the White, Kara, and Bering seas in 2012–2017 were analyzed for the animals of different age and sex (n = 22). 4,4'-DDE dominated among the OCPs analyzed; the main PCB congeners were PCB-138+PCB-158 and PCB-153 + PCB-168, which was also typical of other Arctic marine mammals. The highest concentrations and widest range of these compounds were found in beluga whales from the White Sea (4,4'-DDE: 3778.3 ± 4856.3 ng/g lipids; ranging as 33.2–16 007.8 ng/g lipids; PCB-138 + PCB-158: 1270.1 ± 1528.8 ng/g lipids; ranging as 127.6–4957.4 ng/g lipids; PCB-153 + PCB-168: 1144.1 ± 1230.2 ng/g lipids; ranging as 113.0–4515.2 ng/g lipids). The lowest concentration was found in the beluga whales from the Anadyr estuary of the Bering sea (4,4'-DDE: 1003.3 ± 1422.1 ng/g lipids; ranging as 186.0–3125.0 ng/g lipids; PCB-138 + PCB-158: 95.0 ± 99.2 ng/g lipids; ranging as 29.9–242.1 ng/g lipids; PCB-153 + PCB-168: 114.8 ± 118.8 ng/g lipids; ranging as 35.4–290.9 ng/g lipids). The biological parameters of the sampled animals, the features of PCB and OCP transport pathways, as well as regional environmental pollution, were considered the main reasons for the observed geographical variability of pollutant concentrations in beluga whales.

The influence of boat tourism on the beluga whale Delphinapterus leucas in the White Sea, Russia, was studied based on regular observations of belugas near the Solovetskiy Islands from 1995 to 2015. Changes in beluga behaviour, which were affected both by the distance between the boats and the whales and the character of boat activity (e.g. anchoring, drifting, or moving with the engine running) were observed. Boats following the belugas caused the greatest impact on the whales. This negative reaction was observed throughout all periods of observations. The results indicate the need to evaluate the potential long‐term, cumulative anthropogenic impact on beluga behaviour and the development of appropriate mitigation measures.

The study of the summer gathering of beluga whales, Delphinapterus leucas, off Cape Beluzhy, Solovetsky Island, White Sea, whose results are considered in the present work, is based on the analysis of photo identification materials over a 7-year period (2007–2013). The Solovetsky gathering is a structural unit of the Onega subpopulation of White Sea beluga whales that consists of individuals with varying degrees of fidelity to this water area. The resident individuals of the Solovetsky gathering usually remain in these waters throughout the summer season, with some of them returning here after each winter, thus, exhibiting philopatry. The non-resident belugas (adult males and females) visit the area only for a certain period of time. During the summer they freely move within the Onega Bay. According to photo identification data, considering the rotation of individuals in the gathering, approximately 195.4 ± 23.5 animals can visit the study area during each summer. This value is significantly greater than the results of visual observations.

The data on mtDNA sequences of the beluga whale (Delphinapterus leucas) from the central Eastern Arctic as well as coastal waters of the Chukchi Peninsula and different parts of the White Sea are presented and analyzed for the first time. Certain sequences found in the region form a separate phylogenetic clade. The distinctness of composition of maternal lineages found for the White Sea is noted. However, the set of sequences found in the Russian Arctic in whole cannot be characterized as region-specific.

Skin defects in beluga whales of the Solovetsky gathering (Onega Bay, White Sea) were found and systematized as a result of long-term (2007–2012) photo-identification work. The probable causes of the defects, based on their appearance as well as their duration are discussed. The occurrence of animals with skin defects of various etiologies and its dynamics over a 3-year period (2010–2012) are analyzed. An attempt is made to assess the health status of the Solovetsky beluga whales.

The parental behavior of beluga whales observed in a summer reproductive gathering (near Solovetsky Island, Onega Bay, White Sea) is described, including the parturition process. A tight association between the female and its newborn infant has been traced by the case study of a stillborn calf. Individual behavioral patterns of a mother and calves observable only in natural habitats are detailed.

Based on the data from long-term research in 1999–2009 we studied the population dynamics of Beluga whales in the Solovetsky reproductive gathering (RG) in the White Sea. This aggregation of Beluga whales is formed each year in the second half of May after the break-up of fast ice and persists to September inclusive. The aggregation numbers about 100 individuals from visual observations, with long-term variations of 20–30 individuals. The percentage of whales of different age groups also varied in the gathering depending on year, but typically one half was formed by mature animals and the other half consisted of immature whales and yearlings. There are two pronounced peaks in numbers for the summer season in the Solovetsky Beluga RG. The number of Belugas increased with the appearance of males and females that were ready to breed and females that were ready to bear calves. The daily dynamics of Belugas in the gathering largely depended on the time of day and tidal regime. In the summer season, the state of the sea and human impacts were key factors in number fluctuations of the Belugas of the Solovetsky RG. The revealed negative correlation of the long-term population of Belugas in the gathering on air temperature is considered as a special instance of general laws of the migration activities of Beluga whales in the White Sea.

The structure of the reproductive gathering of beluga whales (RG) was studied near Cape Beluzhii in the Solovetsky Islands in the White Sea by the photo identification of individuals in 2007–2008; in addition, the peculiarities of the seasonal and interseasonal dynamics of the RG incomings were analyzed. The gathering is formed by predominantly females and calves of different ages, which visit the RG area as stable “family” groups. About 15% of the observed females come to Beluzhii Cape every year and stay there during the whole summer season; thus, forming the regular part of the RG. The other animals come there for a certain time period, which is probably preconditioned by their physiological readiness for coupling and procreation for some of the females. When comparing our data with the catalogue of the visually registered beluga whales’ markers (1996–2008), we found that most of the identified animals of the Solovetsky RG appear here during one summer season or even with an off period of several years despite the significantly regular findings of most of them for this area. We conclude this may be linked with the natural changes of the individual markers due both to the shedding and the sexual cycle in the mature animals. Our data allow concluding that the total population of the Solovetsky PG is higher than was reported before using the visual supervision methods.

The periods of development individual behavior in beluga calves are described. During these periods, calves form locomotor skills and interrelations with other individuals, and this determines the overall social structure of a pod. The formation of behavior in White Sea beluga calves passes through a number of stages. New types of social interactions arose in the following sequence: the imprinting period, the first abandoning of the mother without contact with other members of the pod and accumulation of new locomotive elements, first contacts with other young-of-the-year calves, and the complication of interaction types through game activities. Calves usually formed pairs with coevals or elder calves that possessed a richer locomotor repertoire. New motions appeared as a result of imitation of adult animals. These periods do not have distinct terms and depend on the individual qualities of the calves. Some changes in the belugas’ behavior were seen under the conditions of the active development of managed ecotourism in the area around Solovetsky Island, the animals showed adaptation to the presence of man.

The parental behavior of beluga whales observed in a summer reproductive gathering (near Solovetsky Island, Onega Bay, White Sea) is described, including the parturition process. A tight association between the female and its newborn infant has been traced by the case study of a stillborn calf. Individual behavioral patterns of a mother and calves observable only in natural habitats are detailed.

Elements of behavior under natural conditions, their duration, and frequency are described in three age groups of belugas calves: newborn, one-month-old, and two-month-old. The quantitative and qualitative indices of the recognized behavioral elements allowed us to evaluate the mother-infant contacts and to analyze their dynamics during calf growth. The most common calf positions relative to the mother during this period were "at the cow's tail" and "at the cow's side." The importance of behavioral responses of calf for the development of social behavior in adult animals is emphasized.

Cancer of the buccal mucosa ranks fourth in the structure of cancers. Pretumor processes of the buccal mucosa are Bouin's disease, leukoplakia verrucosa, papillomatosis, erosive ulcerative and hyperkeratotic lupus erythematosus and lichen planus, and postradiation stomatitis. Two clinical cases of cancer of the tongue in young men aged 27 years are described. Preventive measures are treatment of pretumor processes in the buccal mucosa, absolute refusal from caustics and from dentures made of different materials, regular check-ups of patients, consultations at specialized oncological institutions with cytological and morphological studies, thorough sanitation of the oral cavity including therapy, surgery, and orthodontic treatment.

The detection of odontocete echolocation signals with acoustic loggers has proved to be a very effective way to monitor their distribution, seasonal patterns and habitat use. However, belugas (Delphinapterus leucas) have never been monitored using this methodology. In order to evaluate its viability, echolocation signals of captive belugas were analyzed and the performance of T‐POD (Chelonia Ltd., UK) acoustic loggers in captivity and in the Arctic environment was tested. Results from captivity demonstrated the potential of beluga remote monitoring by T‐PODs. Field tests were organized in different environmental conditions with different populations of belugas to ensure the validity and detection robustness of this method. T‐PODs were deployed in Svalbard (Norway) in Spring 2007, in Yakutat (Alaska) in Spring 2008, and in Solovetsky (Russia) in Summer 2008. Instruments were deployed concurrently with visual observations and hydrophone recordings to compare presence/absence data from the three different methods. Results proved that T‐PODs positively detected all the identified periods of beluga presence without false detections and revealed temporal distribution correlations with tide levels, feeding behaviors, and circadian rhythms in the echolocation activity. Results from this project indicate that beluga remote monitoring is feasible in the Arctic environment using acoustic loggers.

The authos investigated the K-spectrum of iron absorption in steel carbides, containing silicon and chromium. It is shown that the K-edge of iron absorption in steel carbide, alloyed with silicon and tempered at a high temperature (650‡), is similar to the K-edge of iron absorption in the carbide of carbon steek, tempered at 400‡. The presence of chromium in the carbide changes the form and energetic position of K-edge absorption in it. This change depends on the temperature of tempering and chromium concentration in the steel.