Northwestern Sea Of Japan Research Articles

Shear-driven vertical mixing and turbulent exchange over the continental slope in the northwestern Sea of Japan

Shear-driven vertical mixing and turbulent exchange over the continental slope in the northwestern Sea of Japan

Evolution and structure of a mesoscale anticyclonic eddy in the northwestern Japan Sea and its exchange with surrounding waters: in situ observations and Lagrangian analysis

Evolution and structure of a mesoscale anticyclonic eddy in the northwestern Japan Sea and its exchange with surrounding waters: in situ observations and Lagrangian analysis

First Investigations of Benthic Soft-walled Foraminifera and Gromiids (Protozoa) in the northwestern Sea of Japan

First Investigations of Benthic Soft-walled Foraminifera and Gromiids (Protozoa) in the northwestern Sea of Japan

Current status and trends for commercial stock of japanese anchovy <i>Engraulis japonicus</i> (Engraulidae) in Russian waters of the Japan Sea

Japanese anchovy Engraulis japonicus of the Tsushima Current stock migrate to the northwestern Japan Sea in warm season and play there an important role in the pelagic food web. According to survey and fishery data, the commercial stock of this species declines recently that determines decreasing of intensity of its migrations into the Russian waters, though its level is still appropriate for fishery. The anchovy releases ashore occur sometimes on the Far-Eastern coast, likely in cases of unstable environments that have become more frequent under climate change. More intense research of the pelagic ecosystem in the northwestern Japan Sea is necessary to clarify the status of fishery resources formed by southern migrants, including anchovy, sardine and mackerel.

New records of Cuspidaria trosaetes Dall, 1925 (Bivalvia: Anomalodesmata: Cuspidariidae) in the Sea of Japan with notes on the genus Nordoneaera

For the first time carnivorous bivalve mollusc Cuspidaria trosaetes Dall, 1925 was recorded in the north-western Sea of Japan. There was only one species of Cuspidaria, C. ascoldica, previously known in this region. Alive specimens of C. trosaetes were collected in the Tatarsky Strait on the continental slope on muddy sediment at the depths of 531–589 m. Stomach contents of C. trosaetes consist of foraminifers, copepods and rissoid gastropods. Cuspidaria trosaetes was selected as a type species of a monotypic subgenus C. (Nordoneaera) Okutani, 1985, which is now considered a separate genus, based on the presence of a thick shell without sculpture and with thick periostracum, as well as a short rostrum. The first obtained data on anatomy of C. trosaetes suggest its close affinity with the type species of the genus Cuspidaria, C. cuspidata. Cuspidaria trosaetes and C. cuspidata share such features as the presence of 5 pairs of septal pores, thin elongated posterior labial palps and the presence of two rows of papillae on the rim of the common siphonal sheath. Taking into account new data we propose to synonymize the monotypic genus Nordoneaera with the genus Cuspidaria.

First record of sharpbeak terapon Rhynchopelates oxyrhynchus (Centrarchiformes: Terapontidae) in the Russian waters of the Japan Sea

The first record of sharpbeak terapon Rhynchopelates oxyrhynchus in the waters of the Russian Federation. This species was known at the coast of Japan, but was not recorded previously in the northwestern Japan Sea.

Population biology of crab Hapalogaster dentata parasitized by rhizocephalan Briarosaccus hoegi in the northwestern Sea of Japan.

We studied the population and reproductive characteristics of the stone crab Hapalogaster dentata (De Haan, 1849) (Anomura: Lithodidae) parasitized by Briarosaccus hoegi (Rhizocephala: Peltogastridae) from Peter the Great Bay (northwestern Sea of Japan) in 2023. The sex structure of the H. dentata population was female-biased and represented by 39.1% males and 60.9% females. The size-frequency distribution differed between males and females. The prevalence of parasitization of H. dentata by B. hoegi reached 6.7%. No relationship between crab sex and parasitization prevalence was found. Most of the parasitized specimens (94.8%) had only a single parasitic externa. The non-parasitized and parasitized crabs did not differ in main carapace length. The pleopods in most of the externa-bearing females were shortened or completely atrophied. H. dentata produced 1 clutch per year with ovigerous females occurring from October to May. An obvious delay in embryonic development was observed in winter. None of the parasitized H. dentata females were ovigerous. Externae with embryos of B. hoegi were found from May to July.

First Investigations of Benthic Soft-Walled Foraminifera and Gromiids (Protozoa) in the northwestern Sea of Japan

First Investigations of Benthic Soft-Walled Foraminifera and Gromiids (Protozoa) in the northwestern Sea of Japan

Mesoscale Anticyclonic Eddies in the Primorye Current System of the Japan/East Sea in the Summer

This study identified a process of water supply due to discrete transport by anticyclonic eddies towards the formation region of the intermediate water in the northwestern Japan Sea in the summer season. The structures and dynamics of three anticyclonic mesoscale eddies were studied by means of the Aqualog moored profiler observational survey at the continental slope in the Primorsky Current region east of Peter the Great Bay in June–July 2015. It was shown that the eddy cores were of ellipsoidal shape with an elongated lower part. The anticyclones as isolated dynamic structures carried water enriched with dissolved oxygen in the west-southwest direction. In terms of the thermohaline characteristics the water transported was similar to the Japan Sea intermediate water at its formation region south of Peter the Great Bay.

Changes in the Composition of Bloom-Forming Toxic Pseudo-nitzschia Diatoms in Surface Waters in Ussuri Bay, Northwestern Sea of Japan, during the Autumn Seasons of 2017–2022

Diatoms of the genus Pseudo-nitzschia are producers of the neurotoxin domoic acid that causes serious damage to marine fauna and aquaculture farms. These microalgae are known as the most abundant group of toxic phytoplankton in Peter the Great Bay, Northwestern Sea of Japan, during the bloom season, which, as was previously reported for members of this group in the study region, lasts in the autumn months. Autumnal blooms of toxic diatoms Pseudo-nitzschia spp. were studied in the period from 2017 to 2022 in Ussuri Bay, the largest body of water in Peter the Great Bay, which harbors numerous recreational area and aquaculture farms. As a result, the following changes in the composition of bloom-forming species were recorded: blooms were caused by the Pseudo-nitzschia delicatissima group in the period from 2017 to 2020 and by P. multistriata in 2021–2022. An assumption has been made that one of the factors responsible for blooms of P. multistriata, known as one of the most widespread species in Asian warm-water areas, is an abnormally high water temperature in the autumn of 2021 in the study area.

Revisit the Upper Portion of the Japan Sea Proper Water: A Recent Structural Change and Freshening in the Formation Area

AbstractLong‐term transition in the deep water of the Japan Sea was investigated to understand how oceans respond to climate change. A basin‐scale density decrease in the upper portion of the Japan Sea Proper Water (UJSPW) by 0.01 σθ was detected from the period 1964–1985 (Period I) to that of 2001–2019 (Period II) using Argo‐ and ship‐based data sets. The density decrease was mainly due to a temperature increase of 0.3°C. Based on the pycnostad density, the UJSPW was redefined as the water mass of 27.30–27.33 σθ, along with the core density of 27.30–27.31 σθ. The dissolved oxygen (DO) and thickness in the UJSPW showed a notable decrease between the periods, along with the isopycnal surfaces flattening. Warming down to 700 m and freshening in the upper 300 m were observed in the winter UJSPW formation area in the northwestern Japan Sea. An influence of the hemispheric‐scale regime shift occurred in 1988/1989 on the UJSPW warming was suggested, along with the long‐term trend in the winter air temperature. The freshening in the formation area was attributable to the increase in winter precipitation in the Amur River basin and the decrease in winter sea‐ice extents in the Okhotsk and northern Japan Seas. The intensified stratification in the UJSPW formation area brought a decrease in the amount of the UJSPW formation through the prevention of winter deep convection, which resulted in the thinner thickness and lower DO in the UJSPW in Period II, along with the temperature increase.

Effects of Two-Species Infestation by Rhizocephalan Barnacles on the Population of the Kelp Crab Pugettia aff. ferox (Decapoda: Brachyura: Epialtidae) in the Northwestern Sea of Japan

Effects of Two-Species Infestation by Rhizocephalan Barnacles on the Population of the Kelp Crab Pugettia aff. ferox (Decapoda: Brachyura: Epialtidae) in the Northwestern Sea of Japan

The genus Schizymenia (Nemastomatales, Rhodophyta) on the Russian coast of the northwest Pacific and description of S. tamarae sp. nov

ABSTRACT We analysed rbcL and COI sequence data of specimens of Schizymenia from the Sea of Okhotsk and Sea of Japan. Our results revealed a new species of Schizymenia, S. tamarae sp. nov., from the northwestern Sea of Japan. This species is distinct based on shape and the position of glandular cells. Morphological and genetic analyses confirmed that the previously described S. jonssonii is a synonym of S. dubyi var. palmata, which was originally described from the Kuril Islands. The latter taxon was synonymized with Neoabbottiella valentinae. We verified the synonymy of the three names and the affinity of the taxon with the genus Schizymenia. Since the name N. valentinae has priority at the rank of species we propose Schizymenia valentinae comb. nov. The only species of Schizymenia currently known to occur along the Russian coast are S. valentinae and S. tamarae. Schizymenia valentinae is distributed along southeastern Kamchatka, on the Commander Islands and Kurile Islands, and S. tamarae is known only from the Sea of Japan, where it occurs from Olga Bay to Peter the Great Bay on the Russian coast, and in Japan.

Geophysical Studies of the Northwestern Japan Sea on the 78th Cruise of RV Professor Gagarinsky

Geophysical Studies of the Northwestern Japan Sea on the 78th Cruise of RV Professor Gagarinsky

Environmental changes clarified by pollen and diatom proxy records in the sedimentary archive of the northwestern Japan Sea during last 21.0 kyr

High-temporal resolution pollen and diatom records from the northwestern Japan Sea document environmental changes over the last 21.0 kyr. Vegetation and climate changes were evaluated using the forest-steppe (SFI) and the pollen temperature (Tp) indices. The highest SFI occurred between ca. 21.0 ka and 16.6 ka and indicates the presence of a relatively dry climate and large areas of forest-steppe in the region. Boreal forests covered the mountain slopes. The broad-leaved trees survived in refugia located in lower mountain belts. Beginning ca. 16.6 ka, SFI decreases, while Tp increases, especially between ca. 11.0 ka and 5.7 ka. However, variations in these indices indicate fluctuating climates during the deglaciation. Significant vegetation changes occurred in the Holocene. Mixed deciduous forests with a predominance of Quercus became widely present beginning ca. 9.8 ka. The area of forest-steppe was reduced occurring only in local habitats. Pinus became one of the most common taxa in the forest ca. 5.3 ka. The geographic features of the coring area have determined in the past the persistence throughout the record of cold-water diatom flora. Cold-water diatoms have dominated in both cool and warm intervals; however, a small increase in the percentage and species diversity of warm-water diatoms was noted for warming. Low sea level during the Last Glacial Maximum (LGM) and early Holocene changed the general patterns in the sea circulation and in the vectors of the longshore currents, which transported the waters formed in the shallow areas of the northeastern and northern parts of the Japan Sea. A slight increase in sublittoral benthic diatoms indicates a lowered sea level during the LGM. The increase in sublittoral planktonic diatoms reflects a gradual rise in sea level during the Bølling–Allerød (BA) and Younger Dryas (YD). A greater component of oceanic diatom species at Holocene indicates the inflow of Pacific waters across both the Tsushima and Tsugaru straits. This study of pollen and diatom records demonstrates a clear response to climatic fluctuations and sea level changes in the Japan Sea during the Late Pleistocene and Holocene.

A description of Dendronotus shpataki sp. nov. (Gastropoda: Nudibranchia) from the Sea of Japan: a contribution of citizen science to marine zoology

The nudibranch genus Dendronotus Alder et Hancock, 1845 is a common component of boreal and arctic ecosystems, which has recently received a considerable attention due to its high cryptic diversity. Here we describe a new species Dendronotus shpataki sp. nov. from the northwestern Sea of Japan, using the material and observations provided by Andrey Shpatak, a local citizen, diver and underwater photographer. We studied morphological features of the new species, including external morphology, coloration, jaw and radular morphology, and configuration of the reproductive system, as well as its ecological traits including possible diet preferences. We obtained DNA sequences and reconstructed the phylogeny by Bayesian Inference and Maximum Likelihood approaches using four molecular markers (mitochondrial COI and 16S rRNA, and nuclear histone H3 and 28S rRNA), and tested the boundaries between the species by calculating the uncorrected p-distances and automatic species delimitation methods ABGD and GMYC. Our results show that D. shpataki sp. nov. differs both morphologically and genetically from all other Dendronotus species. The new species possibly represents a unique example of local endemism, being found in a single locality, while other local Dendronotus species demonstrate wide distribution in the North-West Pacific. We also report on a considerable wearing of the radular teeth during feeding, which is a remarkable case for the Dendronotus.

A description of Dendronotus shpataki sp. nov. (Gastropoda: Nudibranchia) from the Sea of Japan: a contribution of citizen science to marine zoology

The nudibranch genus Dendronotus Alder et Hancock, 1845 is a common component of boreal and arctic ecosystems, which has recently received a considerable attention due to its high cryptic diversity. Here we describe a new species Dendronotus shpataki sp. nov. from the northwestern Sea of Japan, using the material and observations provided by Andrey Shpatak, a local citizen, diver and underwater photographer. We studied morphological features of the new species, including external morphology, coloration, jaw and radular morphology, and configuration of the reproductive system, as well as its ecological traits including possible diet preferences. We obtained DNA sequences and reconstructed the phylogeny by Bayesian Inference and Maximum Likelihood approaches using four molecular markers (mitochondrial COI and 16S rRNA, and nuclear histone H3 and 28S rRNA), and tested the boundaries between the species by calculating the uncorrected p-distances and automatic species delimitation methods ABGD and GMYC. Our results show that D. shpataki sp. nov. differs both morphologically and genetically from all other Dendronotus species. The new species possibly represents a unique example of local endemism, being found in a single locality, while other local Dendronotus species demonstrate wide distribution in the North-West Pacific. We also report on a considerable wearing of the radular teeth during feeding, which is a remarkable case for the Dendronotus.

Porcellanid crab Pachycheles stevensii parasitized by rhizocephalans Lernaeodiscus spp.: population biology in the northwestern Sea of Japan.

We examined the population and reproductive characteristics of the anomuran crab Pachycheles stevensii Stimpson, 1858 (Decapoda: Porcellanidae) heavily infested by 2 rhizocephalans of the genus Lernaeodiscus in the northern part of the species range (Peter the Great Bay, Sea of Japan) in 2020-2021. The prevalence of infestation reached 32.3%, and L. rybakovi proved to be much more numerous than L. kasyanovi. The sex structure of the P. stevensii population was represented by males (38.8%), females (50.6%), and modified specimens (10.6%), which were extremely feminized males. The latter had a broadened abdomen, smaller chelae, shortened gonopod, and 3 additional pairs of female-type pleopods. Thus, the initial sex ratio in the P. stevensii population approximated the expected 1:1, as in most porcellanid crabs. No significant modifications of the secondary sex characters of the female hosts were observed. The size structures of males and females did not significantly differ. P. stevensii produced 1 clutch yr-1. Oviposition and incubation lasted from summer to early fall; recruitment was noted in the fall. There was a correlation between the reproductive cycles of the host and parasites: rhizocephalans with mature externae were found from June-October. A large number of ovigerous female P. stevensii simultaneously carried parasitic externae of L. rybakovi; fecundity was considerably higher in non-infested females.

Morphological variability and genetic analysis of Thalassiosira tenera (Bacillariophyta), a dominant phytoplankton species from the northwestern Sea of Japan

ABSTRACT Thalassiosira species significantly contribute to phytoplankton communities, forming algal blooms in temperate and polar regions, and are broadly used as model organisms for nanotechnology and as important food sources in the aquaculture industry. Despite being widespread in the world’s oceans, data on abundance and seasonal patterns of individual species of Thalassiosira are sparse. In the present study, we have identified Thalassiosira tenera from the northwestern Sea of Japan, using light and scanning electron microscopy (SEM), and molecular genetic analysis of 28S rDNA sequence. Based on field and cultured material, morphological variability of T. tenera was studied; a detailed diagnostic description of the species is provided, and its morphometry is compared with that of the morphologically similar T. exigua. Growth peculiarities of the species were investigated in laboratory culture; variations in frustule morphology occur at different growth stages. The degree of frustule silicification is assumed to depend on the stage of cell development. By SEM observations of field samples, the seasonal dynamics of the species was examined and data on its abundance are provided for the first time. Findings indicate that T. tenera is present year-round in the phytoplankton assemblage in the northwestern Sea of Japan. The species dominates the community from November to February, accounting for more than 60% of the total phytoplankton abundance. The highest numbers, 7,281 cells l−1, were recorded under the sea ice in January, and the lowest numbers, less than 100 cells l−1, occurred in April. In addition, the study gives information on the species ecology.

Study of the State and Variability of the Northwestern Japan Sea in the Autumn–Winter Period on Cruise 62 of the R/V Akademik Oparin

Study of the State and Variability of the Northwestern Japan Sea in the Autumn–Winter Period on Cruise 62 of the R/V Akademik Oparin