Zubov State Oceanographic Institute

The genomes of most gnathostomes contain two paralogs of the shox gene, shox and shox2, both of which are implicated in the development of two key morphological innovations: the jaw apparatus derived from the branchial arches and the paired appendages, whose evolutionary origins remain debated. Here, we investigate the expression patterns of shox and shox2 paralogs in the gray bamboo shark (Chiloscyllium griseum), a representative of Chondrichthyes, a basally divergent gnathostome lineage. The paired fins of cartilaginous fishes are considered a basal model for gnathostome appendages. Our findings suggest spatial subfunctionalization of the shox and shox2 genes. Specifically, shox is expressed in the mandibular and branchial arches, as well as in paired and unpaired fins, indicating shared developmental mechanisms among these structures. In contrast, shox2 expression is predominantly restricted to paired fins, highlighting distinct developmental features that differentiate them from the evolutionarily older median fins.

This article aims to assess wind regime variations in the Russian seas and identify shipping and fishing areas where the frequency of dangerous winds showed statistically significant upward trends. The assessment is based on ERA-5 global atmospheric reanalysis data on hourly mean wind velocity from 1991–2020. The methodology employed standard statistical methods for data processing. The results of the assessment of increased storm risks across all Russian seas are summarized in a table. The study confirms that the wind regime in the Russian seas is non-stationary and responds to global climate variations. The most dynamic changes in wind conditions occur in the open seas (Bering, Barents), which have free exchange with external seas and oceans. The greatest risks to shipping and fishing, associated with an increased frequency of dangerous winds given medium or high climatic norms for this indicator, were identified in the following areas: the northeastern part of the Black Sea, including approaches to the ports of Novorossiysk, Tuapse, and the Kerch Strait area (winter season); the Baltic Sea, including shipping lanes in its central part and the Gulf of Finland (winter season); the Barents Sea (winterspring season); the southwestern part of the Bering Sea, including sections of transoceanic routes (winter season); and the northwestern sector of the Pacific Ocean, including sections of shipping lanes and fishing areas off the eastern coasts of Kamchatka and the Kuril Islands (winter-spring season). It is noted that ship crews and shipping company personnel should account for the increasing storm risks when planning navigation in these areas (especially those with harsh climates) and take measures to minimize them, including considering alternative routes. Emphasis is placed on the critical importance of the quality of training of ship crews for navigation in storm conditions, icing, steering failure, and assisting vessels in distress.

Marine litter pollution is currently recognized as global problem at the level of all international organizations and conventions related to the marine protection. This review examines modern methods and approaches for detecting floating marine macrolitter. The task of detecting marine litter on the water surface is complicated by a large variety of objects, various degrees of their degradation, predominantly small size, partial immersion in the subsurface layer, colorlessness, disguising within the water, difficult observation conditions. The main approaches today include visual observations (from ships, aircraft), trawling, and remote sensing, especially using radar systems. In the last decade, deep learning methods have made significant progress, which has allowed error recognition and identification to be brought to a new level due to various modifications of artificial neural networks. In this review, we analyze the main research on the presented topic and significant achievements and prospects for the application of artificial intelligence to improve methods for detecting and classifying marine litter larger than 2.5 cm.

Abstract—Variations in the position of the dome of Weddell Sea Deep Water was studied based on the EN4 data on temperature and salinity for monthly mean conditions in February and August in 1993–2012 depending on the wind friction stress calculated according to the JRA55-do data. The dome itself is considered in the region 60°–67° S and 10°–25° W. The range of potential temperatures in the layer of Weddell Sea Deep Water is 0.02-0.20°C. Observed mean data of the dome of isotherms and isopycnals in February from 1993 to 2012 is formed as a sequence of the intensification of the thermohaline circulation in general and the wind circulation of water in the Weddell Sea. Isotherms experience periodic rise and descent under the influence of seasonal variability of the cyclonic nature and the intensity of the wind field. The outflow of deep water from the Weddell Sea mainly occurs through the Orkney Passage over a transverse ridge of about 3600 m deep. Depending on the rise or descent of the isotherms around this passage, warmer or colder Antarctic Bottom Waters enter the Scotia Sea.

In contrast to fairly good knowledge of seasonal and interannual variability in North Atlantic salinity, its long-term historical changes remain poorly characterized, making it difficult to assess the current state and possible future changes. To fill this gap, we present the results of applying a non-parametric method of regression analysis (quantile regression) to assess long-term changes in North Atlantic salinity (0°–70° N, 8°–80° W) based on multiple datasets. The features of quantile trends in monthly salinity for a median value in two periods (1948–2018 and 1961–2011) are considered. In 1948–2018, salinization was generally detected in North Atlantic tropical and subtropical latitudes, while desalination was found in subpolar latitudes. For the 71-year period under consideration, the median monthly salinity in subtropical latitudes increased by 0.07±0.02 PSU. Over the period 1961–2011, pronounced long-term changes in the North Atlantic salinity are difficult to identify based on the datasets used. A consistency analysis of significant salinity trends across the most used datasets allowed us to detect five small areas with pronounced positive trends in the upper ocean salinity. These include the Guiana Current, the vicinity of 12° N, 48° W, the Canary upwelling area, the region of the Gulf Stream transition to the North Atlantic Current and the western part of the North Atlantic Subpolar Gyre. In these areas, over a 51-year period, salinity in the 10–400 m layer increased by an average of 0.10±0.04 PSU.

In the Western Crimea coastal marine waters in June–July 2023 the pollution by petroleum hydrocarbons (TPHs), anionic detergents (APAV) and trace elements (heavy metals) was studied. There was no significant change in hydrological indicators, including the water salinity varied in range 17.27–18.71 ‰, which could have been the result of a recent breakthrough of the dam of the Kakhovsky reservoir. The results showed the predominant importance of petroleum hydrocarbons in assessing the quality of marine waters according the standard calculation of Index of Water Pollution (IWP). The concentration of TPHs was equal to or exceeded the established normative MAC = 0.05 mg/dm3 in 87 % of the samples taken. Two maxima (0.36 and 0.50 mg/dm3) were recorded in the Karkinite Bay apart from coast and reached 7–10 MAC. Near coast here the values were rather high also (0.08–0.09 mg/dm3). The content of of detergents and heavy metals was quite low and did not reach the corresponded MAC. The oxygen regime was generally within normal limits throughout the studied marine water area. The exception was only the top of the Karkinite Bay, where its deficit of dissolved oxygen reached 27 %. In the colder waters near the bottom the concentrations of oxygen increased. The contribution of each studied pollutants into the level of IWP was assessed. The difference in the hydrochemical state of the Karkinite and Kalamita Bays of the Western Crimea is shown. According to the magnitude of the pollution index, the waters of the Kalamita Bay were characterized as “clean” while the Karkinite Bay as “moderately polluted”.

This study assessed total hydrocarbon content and polycyclic aromatic hydrocarbon content in Grönfjord (the Greenland Sea, Svalbard). The field study was held in marine expeditions of research vessel “Barentsburg” by the North-Western Branch of the Federal State Budget Institution, Research and Production Associaton «Typhoon» in summer periods of 2012 to 2022. In the framework of the field works simultaneous measurements of hydrological and hydrochemical characteristics of the water column were done. The data was analyzed using standard procedure in purpose to gather new information about the levels of hydrocarbons (measured as total hydrocarbon contents), polycyclic aromatic hydrocarbons. The results showed pronounced interannual variations of total hydrocarbon contents and polycyclic aromatic hydrocarbons concentrations. Supposed that local natural sources contribute to elevated polycyclic aromatic hydrocarbons and total hydrocarbon content levels both in water and in sediments, the levels of contamination do not signify exclusively anthropogenic influence on the sea-body. At the same time, some local elevated petroleum hydrocarbons concentrations, which were detected in the surface water layer, may be a sign of existing industrial activity affecting the waters of the fjord. Continuity of tasks starting from earlier expeditions indicates that many processes in the Norwegian Sea, Greenland Sea require further research.

Abstract In this model study, we address the feasibility of rapid shutdown or, at least, substantial weakening of the Global Circulation Conveyor (GCC) caused by massive discharge of freshwater to the northern North Atlantic (NA). The source of this freshwater excess is the permanently ice-covered Arctic Ocean (AO), while its release may be caused by ice melting and intensified river runoff due to global warming. To check up the validity of this hypothesis, we carried out the two idealized experiments with opposite atmospheric forcings over the AO: the so-called "cyclonic" one, which favors intensive water exchange between the AO deep interior and the Nordic Seas (NS), and "anticyclonic" one, which impedes this exchange. We chose the two actual years with extremal forcings (1989 as cyclonic one, and 2004 as anticyclonic one) and artificially applied these forcings during the 10-year period assuming that such a duration is at the margin of physical realism. Our major finding, within the limitations of numerical experiments on the OGCM (Ocean General Circulation Model) INMOM (Institute of Numerical Mathematics Ocean Model), shows that anomalously long preservation of "cyclonic" forcing over the AO is able to substantially rearrange salinity in the upper ocean layer. However, it may not trigger massive "instant" outflow of freshwater through the Fram and Denmark Straits, since a large portion of accumulated in the Beaufort Gyre freshwater spreads around the AO following the circulation without reaching the Fram Strait. However, the tendency of the upper ocean layer freshening in the northern NA due to flushing of freshwater from the AO is confirmed in consistency with the basic concept of the GCC hiatus.

In this paper, a new analysis of the known topographic models of Rossby waves for piecewise exponential topography profiles is performed. A mathematical method is proposed that allows us to find analytically the group velocity and variance. A numerical comparison is made of the relations presented in the study of Buchwald and Adams and the dependencies obtained within the framework of a new analytical approach. Numerical comparative analysis showed that the discrepancy for the phase velocities lies in the range of five percent. For group speeds, the discrepancy reaches nineteen percent for the first mode and decreases for higher mode numbers. We also consider long-wave asymptotics of eigenfunctions. It is established that the long-wave limit for Rossby shelf waves has specifics: the longitudinal wave number tends to zero, and the transverse wave number reaches a certain finite positive constant, which is the greater the higher the mode number. It is shown that in the long-wave limit, Rossby shelf waves transform into shelf topographic currents, while there is a certain self-similarity for the phase and group velocities of shelf currents depending on the value of the topography gradient.