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Data of morphometric measurements of Strongylura anastomellaFL 71.2 cm, which entered the fixed seine set near the mouth of the Lyutoga River on June 8, 2023 are presented. Information on its catches at other coastal sites in Sakhalin waters is considered. [ABSTRACT FROM AUTHOR]

The results of studying the bathymetric and spatial distribution of the barred snailfish Crystallias matsushimae are presented according to bottom trawl surveys in the Russian waters of the Sea of Japan. The species does not form dense aggregations, although it is not as rare as was previously thought: in bottom trawl catches on the continental slope, the frequency of its occurrence is about 30%. The main areas of the species aggregations are the western part of the Peter the Great Gulf and the deep-water section of the Tatar Strait between the mainland and Sakhalin Island. Despite the relatively wide range of water temperature and depths at which the snailfish was found in catches, the species prefers rather narrow thermal and bathymetric ranges: 0.6–1.5°C and 200–500 m. Mysids, amphipods and decapods dominate in the diet. [ABSTRACT FROM AUTHOR]

The fish species diversity, fish density, and distribution in the nearshore beds of Zostera marina and Ulva fenestrata have been assessed by SCUBA visual counts in May–September and November 2021. In total, 23 fish species have been registered. The fish species richness increases from 8–13 species in May to a maximum of 17–19 species at the end of June. Then it slightly decreases in July–September and reaches its lowest values in November (2–5 species). The same changes have been noted for the fish density. Fish diversity in the Zostera beds is higher than in the Ulva ones. The similarity of the fish species composition between Zostera and Ulva is low (the Sørensen-Czekanowski index varied from 0.32 to 0.44). In general, fish density is low (from 2.4 to 112.4 ind./50 m2 in Ulva (in November) and Zostera (in July) beds, respectively), although with an exception for Opisthocentrus spp. and Gymnogobius heptacanthus juveniles. An abnormal high bottom water temperature (above 26°C) in late July–early August has led to temporal avoidance of shallow water with plant beds by fishes (except for Gymnogobius heptacanthus) and their shift to a depth of 3.5–4.5 m, where the temperature was lower by 4.0–5.7°С. [ABSTRACT FROM AUTHOR]

A comparative morphological analysis has been conducted for antlered sculpins of the genus Enophrys from three remote regions: the Sea of Japan, the Sea of Okhotsk, and the Bering Sea. Variations in their body color pattern and also meristic and measurable characters have been analyzed. As the analysis has shown, antlered sculpins from the Sea of Japan differ significantly from the two other samples in their body color, some head proportions, and the size and location of the fins D1, D2, A, V, and P. Differences on the subspecies level (CD > 1.28) have been found for five of the studied characters and a hiatus (differences on the species level) for one character (depth of D1). The data we obtained confirm the previously published assumption that the fish from the Sea of Japan possibly belong to the species E. namiyei. [ABSTRACT FROM AUTHOR]

Abstract River discharge to the ocean influences the transport of salts and nutrients and is a source of variability in water mass distribution and the elemental cycle. Recently, using an underwater glider, we detected thick, low-salinity water offshore for the first time, probably derived from coastal waters, in the central-eastern Sea of Japan, whose primary productivity is comparable to that of the western North Pacific. Thereafter, we aimed to investigate the offshore advection and diffusion of coastal water and its variability and assess their impact. We examined the effects of river water discharge on the flow field and biological production. Numerical experiments demonstrated that low-salinity water observed by the glider in spring was discharged from the Japanese coast to offshore regions. The water is discharged offshore because of its interaction with mesoscale eddies. A relationship between the modeled low-salinity water transport to the offshore region and the observed chlorophyll-a in the offshore region was also observed, indicating the influence of river water on offshore biological production. This study contributes to understanding coastal-offshore water exchange, ocean circulation, elemental cycles, and biological production, which are frontiers in the Sea of Japan and throughout the world.

River discharge to the ocean influences the transport of salts and nutrients and is a source of variability in water mass distribution and the elemental cycle. Recently, using an underwater glider, we detected thick, low-salinity water offshore for the first time, probably derived from coastal waters, in the central-eastern Sea of Japan, whose primary productivity is comparable to that of the western North Pacific. Thereafter, we aimed to investigate the offshore advection and diffusion of coastal water and its variability and assess their impact. We examined the effects of river water discharge on the flow field and biological production. Numerical experiments demonstrated that low-salinity water observed by the glider in spring was discharged from the Japanese coast to offshore regions. The water is discharged offshore because of its interaction with mesoscale eddies. A relationship between the modeled low-salinity water transport to the offshore region and the observed chlorophyll-a in the offshore region was also observed, indicating the influence of river water on offshore biological production. This study contributes to understanding coastal-offshore water exchange, ocean circulation, elemental cycles, and biological production, which are frontiers in the Sea of Japan and throughout the world. [ABSTRACT FROM AUTHOR]

A hypoxic zone with dissolved oxygen concentrations of 3.0–3.6 mL/L (42–51% saturation) was first discovered in the bottom depression in the Srednyaya Cove (between the Pushchin and Pashinnikov capes) in Vostok Bay in July–September 2021. It existed from mid-July to mid-September. It was revealed that the surveyed area was characterized by high concentrations of phosphates at bottom horizons and organic carbon in sediments. It was shown that the formation of the hypoxic zone occurred as the result of an increase in the anthropogenic impact on this sea area. [ABSTRACT FROM AUTHOR]

Benthic dinoflagellates have been the subject of extensive taxonomic research in recent decades. Studies of morphologies of already known species of benthic dinoflagellates from various geographical populations remain relevant, as these allow elucidation of some details that were overlooked in the original species descriptions or assessment of their morphological variability. In the present study, two rare species of dinoflagellates, Amphidiniella sedentaria and Pachena cf. leibnizii, have been studied, for the first time, from coastal sands of the northwestern Sea of Japan. In the cells of A. sedentaria from the Sea of Japan, we have found two anterior intercalar plates instead of one. Therefore, the original formula has been changed to APC 4′ 2a 7″ 5c 4s 6‴ 2⁗. As a result of the examination of P. cf. leibnizii from the Sea of Japan, we have counted seven precingular plates and six cingular plates, instead of six and five, respectively, indicated in the original description. The plate formula of the cells of P. cf. leibnizii from the Sea of Japan is APC 4′ 3a 7″ 6c 5s 5‴ 2⁗. It is currently difficult to judge whether these differences are morphological variations. Therefore, we have identified these cells as P. cf. leibnizii. [ABSTRACT FROM AUTHOR]

The paper presents brief results of gas-geochemical and hydrometeorological studies of the outer water area of Peter the Great Bay (Sea of Japan), obtained as a result of a marine expedition study on the R/V Professor Gagarinskiy (cruise 83) in October–November 2022. Areal atmochemical measurements of climatically active gases (CH4, CO2, H2O vapor) and Hg(0) in the near layer of the atmosphere of the outer water area of Peter the Great Bay were performed for the first time. Gas geochemical fields in bottom sediments and water column are detailed. The current position of gas flares within the outer shelf of Posyet Bay is determined. Long-term stations for marine daily monitoring were carried out. [ABSTRACT FROM AUTHOR]

The fauna of planktonic and benthic foraminifera of the Tatar Strait in the surface layer of sediments from cores sampled during the cruise LV85 on the R/V «Akademik Lavrentiev» in May 2019 has been studied. The benthic foraminifera assemblages, consisting of living and dead shells, correspond in their ecological appearance to the modern cold-water oceanographic conditions of the studied area. Among planktonic foraminifera, along with the dominant subarctic form Neogloboquadrina pachyderma dex., there are single tropical and subtropical species (Globorotalia inflatа, Globigerinoides ruber and Neogloboquadrina dutertrei). The authors believe that the above warm-water forms entered the Tatar Strait from the southwestern part of the Sea of Japan with the warm waters of the Tsushima Current. Fossil finds of warm-water fauna in Pleistocene and Holocene sediments play an important role in deciphering the geological record in the northern part of the Sea of Japan. Their presence in sedimentary sections makes it possible to trace the northward migration of the warm current and assess the extent of its influence on coastal ecosystems in the past.

Abstract The 1 January 2024 Noto-Hanto (Noto Peninsula) earthquake (MJMA 7.6) generated strong ground motion, large crustal deformation and tsunamis that caused significant damage in the region. Around Noto Peninsula, both offshore submarine and partially inland active faults have been identified by previous projects: Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and Japan Sea Earthquake and Tsunami Research Project (JSPJ). We inverted the tsunami waveforms recorded on 6 wave gauges and 12 tide gauges around Sea of Japan and the GNSS data recorded at 53 stations in Noto Peninsula to estimate the slip amount and seismic moment on each of active faults. The results show that the 2024 coseismic slips were 3.5 m, 3.2 m, and 3.2 m on subfaults NT4, NT5 and NT6 of the JSPJ model, located on the northern coast of Noto Peninsula and dipping toward southeast. A smaller slip, 1.0 m, estimated on NT8 on the southwestern end of the 2024 rupture, may be attributed to its previous rupture during the 2007 Noto earthquake. The total length of these four faults is ~ 100 km, and the seismic moment is 1.90 × 1020 Nm (Mw = 7.5). Almost no slip was estimated on the northeastern subfaults NT2 and NT3, which dip northwestward, opposite to NT4–NT5–NT6, and western subfault NT8. Aftershocks including the MJMA 6.1 event occurred in the NT2–NT3 region, but they are smaller than the potential magnitude (Mw 7.1) those faults can release in a tsunamigenic earthquake. Similar features are also found for the MLIT model; the 2024 slip was only on F43 along the northern coast of Noto Peninsula, and northeastern F42 did not rupture, leaving potential for future event. Graphical Abstract

The Hunga Tonga–Hunga Ha'apai volcanic eruption on January 15, 2022 generated a tsunami that affected the entire Pacific Ocean. Tsunami waves from the event have been generated both by incoming waves from the source area with a long-wave speed in the ocean of ~200–220 m/s, and by an atmospheric wave propagating at a sound speed of ~315 m/s. Such a dual source mechanism created a serious problem and was a real challenge for the Pacific tsunami warning services. The work of the Russian Tsunami Warning Service (Yuzhno-Sakhalinsk) during this event is considered in detail. The tsunami was clearly recorded on the coasts of the Northwest Pacific and in the adjacent marginal seas, including the Sea of Japan, the Sea of Okhotsk, and the Bering Sea. We examined high-resolution records (1-min sampling) of 20 tide gauges and 8 air pressure stations in this region for the period of January 14–17, 2022. On the Russian coast, the highest waves, with a trough-to-crest wave height of 1.3 m, were recorded at Malokurilskoe (Shikotan Island) and Vodopadnaya (southeastern coast of Kamchatka). Using numerical simulation and data analysis methods, we were able to separate oceanic "gravity" tsunami waves from propagating atmospheric pressure waves. In general, we found that on the outer (oceanic) coasts and southern coast of the Sea of Okhotsk, oceanic tsunami waves prevailed, while on the coast of the Sea of Japan, oceanic and atmospheric tsunami waves had similar heights. [ABSTRACT FROM AUTHOR]

The first case of hydrothermal brecciated crusts composed of goethite with quartz veinlets is described for the Sea of Japan. [ABSTRACT FROM AUTHOR]

The 1 January 2024 Noto-Hanto (Noto Peninsula) earthquake (MJMA 7.6) generated strong ground motion, large crustal deformation and tsunamis that caused significant damage in the region. Around Noto Peninsula, both offshore submarine and partially inland active faults have been identified by previous projects: Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and Japan Sea Earthquake and Tsunami Research Project (JSPJ). We inverted the tsunami waveforms recorded on 6 wave gauges and 12 tide gauges around Sea of Japan and the GNSS data recorded at 53 stations in Noto Peninsula to estimate the slip amount and seismic moment on each of active faults. The results show that the 2024 coseismic slips were 3.5 m, 3.2 m, and 3.2 m on subfaults NT4, NT5 and NT6 of the JSPJ model, located on the northern coast of Noto Peninsula and dipping toward southeast. A smaller slip, 1.0 m, estimated on NT8 on the southwestern end of the 2024 rupture, may be attributed to its previous rupture during the 2007 Noto earthquake. The total length of these four faults is ~ 100 km, and the seismic moment is 1.90 × 1020 Nm (Mw = 7.5). Almost no slip was estimated on the northeastern subfaults NT2 and NT3, which dip northwestward, opposite to NT4–NT5–NT6, and western subfault NT8. Aftershocks including the MJMA 6.1 event occurred in the NT2–NT3 region, but they are smaller than the potential magnitude (Mw 7.1) those faults can release in a tsunamigenic earthquake. Similar features are also found for the MLIT model; the 2024 slip was only on F43 along the northern coast of Noto Peninsula, and northeastern F42 did not rupture, leaving potential for future event. [ABSTRACT FROM AUTHOR]

The present study is devoted to a comparison of the structure and quantitative ratio of heterogeneous spermatozoa of native wild mussels Mytilus trossulus Gould, 1850, collected in four areas of the Peter the Great Bay of the Sea of Japan (the northwestern part of the Pacific Ocean). The mussels were identified as M. trossulus by shell appearance, and the species was confirmed by sequencing the mitochondrial cytochrome c oxidase subunit I gene (COI). Heteromorphic spermatozoa were found; namely, a total of eight morphs (SPERM1–SPERM8) in M. trossulus. Surprisingly, some of the detected sperm morphs overlap morphologically with the sperms of other mytilids such as M. edulis, Crenomytilus (M.) grayanus and M. coruscus. Possible reasons for this phenomenon are discussed. In each geographic area, the 'quantitative proportions of heterogeneous spermatozoa' (QPHS) were unique. It has been suggested that the QPHS score can be considered in the context of its applicability as a biological marker for finding optimal mussel rearing sites. [ABSTRACT FROM AUTHOR]

Samples of the holothurian Eupentacta fraudatrix (Djakonov & Baranova in Djakonov, Baranova & Saveljeva, 1958) from the Sea of Japan were studied and the relationships of the genera Eupentacta and Sclerodactyla, as well as related taxa, were evaluated on the basis of phylogenetic analysis of the mitochondrial DNA COI and 16S rRNA genes. Using three methods, phylogenetic trees were constructed, and the degree of reliability of topological reconstructions was estimated by means of a nonparametric bootstrap test for the neighbor joining (NJ) and maximum likelihood (ML) techniques, as well as by a posteriori probability for Bayesian inference (BI) analysis. Genetic data confirm the validity of the assignment of Cucumaria fraudatrix to the genus Eupentacta Deichmann, 1938. The study of sequences obtained from the holothurian specimens collected in Russian waters, near the city of Vladivostok, and determined by morphological characters clearly indicate that these specimens belong to the genus Eupentacta and are assigned as E. fraudatrix. The specimens from China in GenBank named as Sclerodactyla multipes and used in the present study, were likely misidentified, and after re-examination they may be assigned to the genus Eupentacta, either as E. fraudatrix or another taxon. Analyses of morphological characters of S. multipes unequivocally affirm that this species must be excluded from Sclerodactyla Ayres, 1851 and is provisionally assigned to the genus Sclerothyone Thandar, 1989 based on the external morphological characters and the body wall ossicles. [ABSTRACT FROM AUTHOR]

Understanding the causes and consequences of foraging behaviour has been a longstanding research interest in the study of animal behaviour. Long-lived seabirds adapt their foraging behaviour in response to seasonal changes in marine environments, particularly to food availability, and the trade-off between current and future reproduction. This postulates the links and direction of causality between environments, foraging behaviour and chick growth; however, these relationships remain unclear, especially on a decadal scale. Here, we focused on streaked shearwaters, Calonectris leucomelas , breeding in the Sea of Japan, as they are an ideal species for examining seabird behavioural and reproductive responses to marine environmental changes. Individuals of this species have two alternative choices for foraging trips, selecting either the northern part of the Sea of Japan or the northwest Pacific Ocean, which have different oceanographic features. From 2011 to 2021, we recorded foraging trips of chick-rearing streaked shearwaters tagged with GPS loggers, and weighed chicks to obtain yearly chick growth rates. Path analyses were conducted to examine the relationships between the sea surface temperature, foraging behaviour of chick-rearing adults and chick growth rate. The results revealed that a larger variability in the surface temperature of the Pacific Ocean and higher demand from chicks attracted the adults towards the Pacific Ocean, suggesting that the foraging area and marine predator distribution are determined by the interplay of food availability and offspring condition. These findings illustrate the importance of using long-term foraging behaviour data sets to better understand the relationships between environmental conditions, foraging behaviour and chick growth. • Streaked shearwater foraging and chick growth were analysed for 11 years. • Shearwaters were attracted to areas with high-variability sea surface temperatures. • Shearwaters flew to high-productivity areas when the chick growth rate was low. • Long-term biologging elucidated the environment–behaviour relationship. [ABSTRACT FROM AUTHOR]

A comparative assessment of the contents of Fe, Zn, Cu, Cd, Mn, Pb, and Ni in the soft tissues of bivalve mollusks Mytilus trossulus, Mytilus galloprovincialis, and their hybrid forms from Minonosok Bay of Peter the Great Bay (Sea of Japan) has been made. No significant differences in the accumulation of Fe and Cd in the tissues of all studied groups of mollusks were found. It has been shown that the hybrid forms of these species had more intensive growth, and against this background they accumulated significantly lower concentrations of such metals as Cu, Mn, Pb, and Ni in their soft tissues compared to the parental species. A significant negative correlation has been found between the accumulation of these metals in the tissues of mollusks and the length and weight of their shells and whole soft tissues M. trossulus, which had a significantly lower weight of valves and soft tissues, differed from M. galloprovincialis in the accumulation of significantly higher concentrations of Zn, for which no relationship has been found between its content and all the studied size and weight characteristics. The conducted testing did not reveal any significant dependence of the accumulation of all studied metals, with the exception of Pb, in the tissues of mollusks on their condition index. The results we obtained indicate the need to take the above features of the trace metal composition of the soft tissues of the studied species into account when using them in monitoring environmental pollution with heavy metals. [ABSTRACT FROM AUTHOR]

The spatial distribution and seasonal variability of mesoscale eddies in the Sea of Japan have been investigated based on the regional database created from the AVISO Mesoscale Eddies Trajectory Atlas (1993–2020). The database contains information about the trajectories and parameters of mesoscale eddies in the Sea of Japan. The eddy detection method is based on the analysis of altimetric maps of absolute dynamic topography. A total of 578 eddies with a lifetime of more than 90 days have been identified (273 anticyclonic and 305 cyclonic). The average lifetime of eddies is 202 days for anticyclonic and 143 days for cyclonic and mean radius of 58 km for anticyclonic and 61 km for cyclonic. The mean speed of anticyclones and cyclones along their trajectories is 2.8 and 3.7 cm/s; the mean orbital velocities of geostrophic currents are 19.0 and 15.1 cm/s, respectively. The maximum number of cases of formation and destruction of anticyclones falls in July–September during the period with high values of water inflow through the Korea Strait. Most of the cyclonic eddies are generated between January and June and decay during the cold half of the year (October–March). A joint analysis of maps of the mean surface circulation in the Sea of Japan (satellite altimetry data) and the spatial distribution of mesoscale eddy shows that the stable eddies of the Sea of Japan are associated with the quasi-stationary meanders of the East Korea East Korea Warm Curent, Subpolar Front, and Tsushima current. The position of meanders is mainly determined by the interaction of the currents with the bottom topography. [ABSTRACT FROM AUTHOR]

The current status of Chlamys swiftii beds and resources of this species in the coastal waters of Primorsky krai, Sea of Japan, are assessed on the basis of data collected in 2007–2021. It has been found that scallops do not form dense aggregations sufficient for commercial harvesting. Scallop beds with the highest average biomass (22.5 ± 5.0 g/m2) are concentrated in the waters from Cape Povorotny to Cape Yuzhny; beds with the lowest biomass are in Peter the Great Bay (3.7 ± 2.1 g/m2). All beds have a mosaic pattern of distribution. The total stock of this scallop species is estimated at 1400 t; the commercial stock, at 1300 t. About 99% of the total stock in the coastal waters of Primorsky krai is concentrated in the area from Cape Povorotny to Cape Zolotoy. In these waters, the recruitment of juveniles to the stock has been found to be more regular and active than in Peter the Great Bay. The percentage of scallops of noncommercial size varies from 1.9 to 19.0%. The Ch. swiftii beds in Peter the Great Bay are dominated by individuals at age of 3–6 years with a shell height of 80–115 mm; in the area from Cape Povorotny to Cape Zolotoy, by individuals at ages of 3–7 years with a shell height of 70–110 mm. The modal age of scallops is 4 years, and the maximum age ranges from 7 to 12 years. [ABSTRACT FROM AUTHOR]

The structure and chemical composition of ferromanganese crusts formed on the sedimentary cover of the underwater volcanoes of the Peter the Great Seamount and the Vasilkovsky Ridge, located near the continental slope of Primorye (Sea of Japan), are studied. The crusts were formed as a result of cementation and precipitation of manganese hydroxides on the sediment surface. The signs of the hydrothermal nature of these formations are very high titanium and low aluminum modules, low contents of nonferrous and rare-earth elements (REEs), and an excess of heavy REE contents over the light ones. An ore substance was probably deposited in the Pleistocene–Holocene from postvolcanic hydrothermal solutions. Unlike the crusts deposited on basalts in the central parts of the Sea of Japan, these crusts do not contain inclusions of fine grains of medium- and high-temperature mineral phases of nonferrous metals. [ABSTRACT FROM AUTHOR]

Rhizocephalan barnacle Parasacculina pilosella Van Kampen & Boschma, 1925, being a common parasite of the spider crab Pugettia aff. ferox Ohtsuchi & Kawamura, 2019, was founded for the first time on the crab Scyra bidentata (A. Milne-Edwards, 1873) (Brachyura: Epialtidae) in Peter the Great Bay (Russian waters of the Sea of Japan). Taxonomical identification of the parasite was made using morphological and molecular methods. [ABSTRACT FROM AUTHOR]

The results of gas geochemical and lithogeochemical studies of bottom sediments in the Tatar Strait trough (Sea of Japan) based on cruise data from the R/V Akademik M.A. Lavrentyev (LV-81 and LV-85) are presented. Anomalies of hydrocarbon gases (HCGs) and chemical elements in the surface bottom sediments were determined. It has been established that sediments with anomalous methane contents are significantly enriched in Mn, Sc, V, Co, Ni, Cu, As, Se, Mo, Cd, Sb, Te, Tl, and U, the coefficients of the concentration (Kc) of which are 1.3–5.9 times higher than similar values at other stations. The data obtained allow us to assume the presence of gas sources of hydrocarbon migration; the continental slope and deep-water area of the Tatar trough are promising for setting up detailed work on the assessment of the oil and gas potential and the gas hydrate content. [ABSTRACT FROM AUTHOR]

During the propagation of the Hinnamnor typhoon from September 5 to 6, 2022, swell waves were recorded that arrived at the recording point 20 h before the typhoon entered the Sea of Japan. While analyzing the field data of the laser meter of fluid pressure variation, it was possible to calculate the area of the formation of the main group of swell waves generated by the propagating typhoon and to localize the region of generation of forerunner waves and also to describe the mechanisms of their formation and propagation. [ABSTRACT FROM AUTHOR]

The taxonomic and quantitative composition of the meiobenthos, with an emphasis on foraminifera and gromiids were studied on the coast of Primorsky krai, northwestern part of the Sea of Japan, at water depths of 0.3–86.0 m. The Protozoa were evaluated for the first time in this region as a component of the meiobenthic communities. The protozoa are represented by four morpho-ecological groups: Ciliophora (free-moving and epibionts), both hard-shelled and soft-walled Foraminifera, and Cercozoa (class Gromiidea). The total abundance of the meiobenthos varied from 32 500 to 2 107 500 ind./m2. The presence of Protozoa was extremely variable. They were completely absent (station 62) and reached a maximum 155 000 ind./m2 (station 42). Among the protozoans, soft-walled foraminifers (SWF) and gromiids (GR) dominated. GRs accounted for up to 51–85% of the abundance of the total protozoa at some stations in Peter the Great Bay. At other stations, SWFs prevailed and reached 93–100% of the total protozoa. The most numerous hard-shelled foraminifers (HSF) and ciliates (CL) were obtained in the Vladimir Bay and at individual stations off the eastern coast of Primorsky krai. Brief descriptions with illustrations are given for 45 representatives of the SWF belonging to the families Allogromiidae and Saccamminidae, of which 22 of them are identified to the species or genus level, and 23 morphotypes are identified to the family level. The gromiid fauna is represented by six morphotypes. [ABSTRACT FROM AUTHOR]

In July–August 2022, the spatial distribution and the composition of local settlements of the bivalve mollusc Mya japonica Jay, 1857 in the Vostok Bay (Peter the Great Bay of the Sea of Japan) were studied. M. japonica occurred almost throughout the entire bay in a wide range of depths from 0 to 22 m at water temperatures from –1.9 to 25°С and salinity from 0 to 34‰. M. japonica was the most abundant in the shallow areas of the bays, closed from the direct wave impact, where, at a depth of up to 4–5 m, the density of the mollusc reached 27 ind./m2, and the biomass was almost 4 kg/m2, which averaged 56% of the total macrozoobenthos biomass. With increasing depth and moving from the dead-end of the bay to the open sea, the abundance of M. japonica decreased by one or two orders of magnitude. Local settlements differed significantly in size and age composition, size-frequency distribution of molluscs, indicating the nature of the replenishment of the benthic population with juveniles, as well as the proportion of commercial size individuals, which ranged from 37 to 98%. The reasons for the revealed features of the distribution and structure of the population of M. japonica are discussed. [ABSTRACT FROM AUTHOR]

This study investigates extreme sea level variations recorded by tide gauges in the coastal regions of the Sea of Japan during the passage of the typhoons Maysak and Haishen in September 2020. Specific focus is on storm surges, seiches and infragravity waves (IG waves) identified in the time series using tidal and statistical analyses. In most cases, storm surges formed through the combined effect of atmospheric pressure changes and strong winds were the major contributors to the extreme sea level rise. The first typhoon, Maysak, was the most significant in strength at the Russian and Japanese coasts, while the largest sea level variations at the southeastern coast of the Korean Peninsula were caused by the second cyclone Haishen. At all sites, the passing storms generated eigen oscillations in bays and harbors. The maximum range of high-frequency oscillations with periods of two to seven minutes, caused by IG waves, was recorded in Preobrazheniye and amounted to 2 m. The observed differences in sea level variations arise from differences in the topographic features of the corresponding coastal sites. Statistical analysis of the atmospheric pressure and wind speed series from weather stations and from the ERA5 reanalysis shows that the atmospheric pressure is reproduced by the reanalysis with high accuracy, whereas the wind speed at different stations has significant discrepancies related to the differences in local features of specific areas. [ABSTRACT FROM AUTHOR]

A new mechanism for the renewal of the Sea of Japan intermediate water mass due to the transport of water volumes by mesoscale anticyclonic eddies in the summer season has been established. The structure and dynamics of three eddies over the continental slope east of the Peter the Great Bay are studied in the Sea of Japan based on the data of an autonomous mooring with the Aqualog profiler in June–July 2015. It is shown that the cores of the eddies had an ellipsoidal shape with an elongated lower part. Anticyclones, as isolated dynamic formations, transported water enriched with dissolved oxygen in the western-southwestern direction downstream the Primorye Current along the continental slope. This water based on its thermohaline characteristics corresponded to an intermediate water mass of low salinity in the source of its formation south of the Peter the Great Bay. [ABSTRACT FROM AUTHOR]

This article is devoted to an analysis of double diffusion processes responsible for diapycnal mixing in the zone of the westward Primorye Current in the northern part of the Sea of Japan. This article presents the results of processing and analysis of a long time series of regular measurements of vertical profiles of thermohaline characteristics and current velocity over the upper part of the continental slope between the depths of 60 and 420 m using the Aqualog mooring station from April to October 2015. Efficient heat and salt exchange coefficients and the buoyancy flux are estimated using the Osborne–Cox (1972) and Gregg (1989) parameterizations. The Turner angle for the verification of double diffusion processes is estimated. The contributions of diffusive convection and salt fingers to the buoyancy flux are studied. It is established that, due to differential diffusion, the layer from 80 to 170 m was involved in intense vertical mixing. Moreover, from midspring to early May, diffusive convection penetrates to a depth of 250 m, and then a process like salt fingers plays a leading role. Shear instability, caused, among other processes, by the weakly nonlinear interaction of internal waves, prevails in the underlying layers. [ABSTRACT FROM AUTHOR]

This paper presents the recent data on the distribution and breeding abundance and distribution of the Mongolian Gull, Slaty-backed Gull, Black-tailed Gull and the Common Tern nesting within Peter the Great Bay of the Sea of Japan. Over the past 30 years, all species of gulls increased their abundance, while the Common Tern has almost ceased to nest on the islands of the bay. [ABSTRACT FROM AUTHOR]

Carbonate nodules were recovered by gravity coring during a complex research expedition conducted in the Sea of Japan aboard the R/V Akademik Oparin (cruise 61), which were identified as pseudomorphs after ikaite (glendonite). This article presents the results of electron-probe analysis and tomography studies of authigenic carbonates and describes gas-geochemical features of host sediments along the continental slope of the Sea of Japan and in the Tatar Strait. [ABSTRACT FROM AUTHOR]

Manganese crusts, composed of manganite with an admixture of pyrochroite and quartz, are revealed for the first time in the Sea of Japan. According to a combination of features, these are low-temperature hydrothermal mineral formations that appeared on the slope of the South Yamato Ridge at a depth of no more than 1300 m under conditions of oxygen deficiency. [ABSTRACT FROM AUTHOR]

The genetic diversity of Pacific rainbow smelt Osmerus dentex from the seas of Okhotsk and Japan has been studied based on nine microsatellite loci and the control region of mitochondrial DNA (940 base pairs). The lowest values of all parameters of genetic diversity of mitochondrial DNA were observed in the group of samples from the northern coast of the Sea of Okhotsk. The highest value of the haplotype diversity was found in the sample from the Sakhalin Island and in rainbow smelt from the Sea of Japan. The star-shaped topology of the genealogical structures indicates a rapid expansion of the abundance and the origin of all populations of the species from a single common ancestor from the main refugium. Based on the results of analysis of nuclear markers, we have revealed a statistically significant genetic structuring of rainbow smelt within its Pacific range (the coefficient of genetic differentiation (FST) is 0.033), which is adequately described by the model of isolation by distance. The greatest genetic differences in two types of markers from the other samples have been found in rainbow smelt from the Shkotovka and Botchi rivers of the basin of the Sea of Japan and from the Naiba River (Sakhalin). The observed patterns of genetic differentiation of Pacific rainbow smelt by the nuclear and mitochondrial markers complement each other well and are most likely associated with differences in the distribution of smelt larvae from the spawning grounds, which are determined by the differentiation of oceanographic conditions. [ABSTRACT FROM AUTHOR]

We identified Gymnocanthus detrisus as the absolute dominant species in the taxocene of sculpins (family Cottidae) caught below the 20-m depth in the aquatic area between Cape Povorotny and Cape Mapatsa. Myoxocephalus polyacanthocephalus, Gymnocanthus herzensteini, Enophrys diceraus, and Triglops pingelii are dominant as well. Subdominant species are Triglops septicus, Icelus cataphractus, Hemilepidotus gilberti, Myoxocephalus brandtii, Myoxocephalus jaok, Taurocottus bergii, and Gymnocanthus pistilliger. Other types of fish identified in this area are insignificant in abundance. Sculpins aggregate at greater depths in the southern aquatic areas, from Cape Povorotny to Olga Bay, and from Olga Bay to Cape Belkin, than in the northern areas, between Cape Belkin and Cape Zolotoy, particularly between Cape Zolotoi and Cape Mapatsa. We attribute this phenomenon to the differences in water regimes. The highest densities of sculpins are generally typical for the southern area. Conversely, the lowest densities are typical in the northern area. However, some species prefer northern areas. The minimum depths of the habitat for different species vary from less than 20 m to 82 m; the maximum depths range from 80 m to 530 m. Due to the high species diversity, aggregations of sculpins are observed in a wide bathymetric range from 20 to 300 m, with peak values at depths of 150–200 m. Sculpins live in summer at water temperatures above 0.4ºC. The shallow water species of sculpins tolerate much greater temperature ranges then deep water species. Hence, the stenotherm increases in deep water species. [ABSTRACT FROM AUTHOR]

Accurate identification of interspecific hybrids is vital for breeding programs in hybridizing taxa, as well as for the use of hybrids in aquaculture and fisheries. The use of species-specific single nucleotide polymorphisms (SNPs) has become the standard for the molecular identification of hybrids. However, it remains challenging to use these SNPs to identify hybrids involving multiple candidate parental species. Here, we developed and validated SNP markers for the identification of hybrids of the 11 closely related pufferfish species (genus Takifugu) distributed in Japan; these species have different aquacultural characteristics, such as growth rate, physiology, behavior, and toxicity. In total, 1232 species-specific SNPs were identified through double-digest restriction-site-associated DNA sequencing. The species had 11 (T. flavipterus) to 295 (T. chrysops) species-specific SNPs. We validated 33 genome-wide species-specific SNPs using TaqMan® genotyping assays for the 11 species and their hybrids, which were identified using amplified fragment length polymorphism analyses. No false negative or positive assignments were observed in 77 and 30 specimens of pure species and F1 hybrids, respectively. This marker combination allows rapid and reliable identification of natural hybrids, which will be useful for pufferfish aquaculture and will enhance our understanding of the natural hybridization between various Takifugu species.

Experiments were carried out on intravital otolith-tagging of juveniles of ocellated blenny after transition to benthic life mode with Alizarin Red S. Tagging at a dye concentration of 200 mg/L for 16–18 h at night, yielded 100% formation of fluorescent tags with zero mortality of experimental individuals. Alizarin tags on the otoliths correspond to "stress" tags in the form of darker microincrements, visible in transmitted light. Calculation of the microincrements in the zone between two consecutive taggings at an interval of 9 days confirmed the daily periodicity of their formation at this stage of development of ocellated blenny. This made it possible to determine the hatching period of juveniles in natural conditions in Zhitkov Bay (Russky Island, Peter the Great Bay, Sea of Japan). Larvae in 2017 for this species hatched, according to our estimates, from the last ten days of March to the end of the second ten days of April, with a peak in the first ten days of April. Hatching begins even under the ice at a slightly negative water temperature of –1 to 0°C, but it proceeds mainly already at a temperature of 1–3°C, after the bay is clear of ice. Taking into account the known timing of spawning of ocellated blenny in Peter the Great Bay (November–early December), it can be stated that development of their eggs in this area is greatly slowed at water temperatures below zero in December–March and can span 4–5 months, which is almost three times longer than the development time in the milder conditions of southern Hokkaido. [ABSTRACT FROM AUTHOR]

Two intraspecific groups of the plain sculpin Myoxocephalus jaok inhabiting the Russian territoral waters in the Sea of Japan, representing the northern and southern species groups, have been revealed. In a summer season, the species groups are separated from each other by a wide water area extending from 45° to 48° N. The northern species-group nucleus in this period is located in the Tatar Strait inlet, while the southern species group inhabits the Peter the Great Bay. In the summertime, the plain sculpin prefers the upper slope shelf area with water column depths ranged from 80 m (for the southern species group) to 60 m (for the northern species group). The juvenile fish tend to be found in shallower waters as opposed to the mature fish. In a cold season, the majority of fish stocks of the southern species group is still congregating in the Peter the Great Bay, shifting to the shelf edge and the continental slope. Some porton of male fish remains at spawning grounds in the coastal zone to the springtime to guard egg clutches. The specimens of the nothern group leave the shallow-water Tatar Bay inlet at massive level to congregate over the winter in the locations of a deep-water area off the mid-coastal zone of the Sakhalin Island. The specimens of the northern group reach the body length of 67 cm, while the sizes in the southern fish group are larger, reaching 75 cm in length. [ABSTRACT FROM AUTHOR]

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Abstract We conducted seismic tomography for entire Japanese Islands including the Sea of Japan and the Pacific Ocean using arrival times from reflection survey as well as the routine seismic network. We successfully imaged the shallow zone along the Sea of Japan from offshore Yamagata to the Noto Peninsula by using air gun data. An extremely low-V shallow zone is imaged between Sado Island and Noto Peninsula. We also obtained detailed seismic velocity structure beneath the Pacific Ocean at depths of 20–50 km using S-net data. The 2007 Noto Peninsula, the 2007 offshore Chuetsu, and the 2019 offshore Yamagata earthquakes occurred at the boundary between high-Vp and low-Vp zones. The west side of the hypocenter of the 2019 offshore Yamagata earthquake at depths of 10–30 km has high-V corresponding to the Mogami Trough. This high-V zone passes through Awa Island and reaches Sado Basin between Sado Island and Honshu. A major rift zone in the Tohoku Arc extending from the Akita region to the Niigata region along the coast of Sea of Japan corresponds to high-V lower crust and a shallow Moho. Graphical Abstract

Simple Summary: Todarodes pacificus is an important cephalopod. This study analyzed the migration path and feeding ecology of T. pacificus by the stable isotope values of the proostracum of the gladius. This result showed that T. pacificus in the East China Sea migrated to low latitudes and nearshore areas during their life history, and the trophic level of their food exhibited no large changes during migration. T. pacificus in the Sea of Japan migrated to high latitudes and offshore areas during their life history, and the trophic level of their food decreased during migration. When the proostracum grew to 120 mm from the distal end, T. pacificus in both areas began to migrate. This study provides a scientific basis for further study on the fishery ecology and life history of T. pacificus. The Japanese flying squid (Todarodes pacificus) is an important cephalopod in the northwest Pacific Ocean. In this study, the proostracum of the gladius of T. pacificus samples collected by Chinese squid fishing vessels in the East China Sea and the Sea of Japan in August and December 2018 were continuously cut, and stable isotope values of the cut fragments were used to analyze the migration path and feeding ecology of T. pacificus. The results showed that when the proostracum grew to 120 mm from the distal end, T. pacificus began to migrate. In the East China Sea, T. pacificus migrated to low latitudes and nearshore areas, and the trophic level of their food showed no large changes during migration. In the Sea of Japan, T. pacificus migrated to high latitudes and offshore areas, and the trophic level of their food showed a decreasing trend during migration. There was no significant difference in migration or feeding ecology between females and males, but the competitive capacity of the females may be stronger than that of the males. The results provided a scientific basis for the scientific management and development of T. pacificus resources. [ABSTRACT FROM AUTHOR]

A palynological assemblage, which was identified during micropaleontological study of the oldest Cenozoic sedimentary cover of the Sea of Japan found at the Yamato Rise, allowed the substantiation of the late Paleocene (59.2–56.0 Ma) age of host deposits. The findings of only marine microfossils in these deposits, the high values of paleosalinity indicators (B, B/Ga), the chemical composition of authigenic minerals, as well as the presence of organic aggregates similar to marine algae, prove a marine genesis of these deposits. It is suggested that sedimentation occurred at the periphery of an epicontinental shallow marine basin under a subtropical climate. [ABSTRACT FROM AUTHOR]

The research outcomes of spatial and bathymetric distribution of dragon poacher Percis japonica are reported based on the bottom trawl surveys carried out in the Russian territorial waters in the Sea of Japan. The species can be found in the waters along the entire coastline. However, its spatial distribution pattern is variable. Thus, its distribution is sparse off the coasts of West Sakhalin, especially off the southern part of the island, while the species tends to congregate in the Peter the Great Bay and the Tatar Strait, where the locations of the species across these water areas remain almost unchanged throughout the year. With respect to the Northern Primorye Coastal Zone, the even distribution is typical for the entire water area, without any high congregation locations. Therefore, the dragon poacher can be found in wide ranges of depths and temperatures. However, its preferable ranges are substantially narrower. The highest values for available biomass resources are typical for the water areas off the Northern Primorye Coastal Zone. [ABSTRACT FROM AUTHOR]