Comparison of biology of the Sakhalin sturgeon, Amur sturgeon, and kaluga from the Amur River, Sea of Okhotsk, and Sea of Japan biogeographic Province

Three Acipenseridae species live in the rivers and marine waters of the Khabarovsk Territory, Russia: Sakhalin sturgeon, Acipenser mikadoi, Amur sturgeon, A. schrenckii, and kaluga, Huso dauricus. We review the general biology and life history of each species, including their historic and current distributions, and examine current paleogeographic theories to outline the possible origin and evolution of these three species in the Amur River, Sea of Okhotsk, and Sea of Japan biogeographic province. Apparently, these species have evolved during distinct geologic time periods, which has reinforced the reproductive isolation of these species although hybridization does occur. They have convergently adapted to the unique environmental conditions of the Amur River and Russian Maritime regions, and yet developed behavioral adaptations to reduce competition between species. Sakhalin sturgeon is the least studied species among anadromous sturgeon in the world. This species is highly migratory and spends the majority of its life in the ocean only returning to natal rivers to spawn. Amur sturgeon and kaluga are distributed throughout the Amur River basin and the estuary and share many life history traits. They are both represented by distinct morphs. Additionally, we present size and weight relationships to estimate the growth of Amur sturgeon and kaluga. All three species have suffered declines in abundance due to over fishing and their contemporary distributions have contracted compared to their historic ranges. We identify gaps in knowledge and suggest further research useful for guiding management of each species.     

The species composition and quantitative distribution of the diatom genus Pseudo-nitzschia H. Peragallo, 1990 in Russian waters of the Sea of Japan and the Sea of Okhotsk

This paper studies the species composition and quantitative distribution of diatoms that belong to the genus Pseudo-nitzschia in the Russian waters of the Sea of Japan and the Sea of Okhotsk. In total, 11 species of this genus were found in the area, including 7 that are known as being potentially toxic. The highest concentrations of Pseudo-nitzschia microalgae (1.4 × 10⁶–2.7 × 10⁶ cells/L) were found in the summer and autumn in the Peter the Great Bay of the Sea of Japan and the lowest concentrations (2.5 × 10²–1 × 10⁴ cells/L) were found in the Sakhalinsky and Akademiya bays of the Sea of Okhotsk. The species diversity of potentially toxic diatoms was greatest (seven species) and the cell concentrations highest (over 6 × 10⁵ cells/L) in the Peter the Great Bay, Sea of Japan, and in the Aniva Bay, Sea of Okhotsk. The density of potentially toxic species was highest near the northeastern coast of Sakhalin Island, in the Amur River estuary, and in adjacent waters. This paper also presents geographical distribution maps of Pseudo-nitzschia species and maps of the density distribution of potentially toxic microalgae over the studied area and identifies potential amnesic shellfish poisoning areas.     

黄海和东海营养盐分布及其对浮游植物的限制

根据1997～1999年黄海和东海4个季节的现场调查资料,分析探讨了黄海、东海的营养盐分布特征及其对浮游植物生长的限制状况．结果表明,在长江口以东及其东北部海域终年存在一个范围很大的营养盐高值区．分析表明,这些营养盐主要来自长江冲淡水的扩展及苏北沿岸流的输送．此外,还获得了1998年长江流域特大洪水期间,迄今被观测到的长江冲淡水中营养盐的最大扩展范围,计算并研究了黄海、东海上层水中Si／N／P比值,结果表明,黄东海上层水中Si／N比值较高,Si不会成为黄东海浮游植物生长的限制因子;但在南黄海南部尤其是西南部、东海近岸及长江口以东海域,N／P比值很高(>30),说明与一般海洋环境的情况不同,黄海、东海有很大一部分海域浮游植物的生长受磷限制,而不是受氮限制．     

Endemic sturgeons of the Amur River: kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii

General biological characteristics and the contemporary status of the kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, are described. Both inhabit the Amur River basin. Kaluga is the largest freshwater fish in this river system reaching more than 5.6 m in length and more than 1000 kg in weight. We recognize four populations of kaluga: the first is from the estuary of the Amur River and coastal brackish waters of the Sea of Okhotsk and Sea of Japan, the second is from the lower Amur River, the third is from the middle-Amur, and the fourth occurs in lower reaches of the Zeya and Bureya rivers. Freshwater and brackish water morphs exist in the estuary population, with the freshwater morph predominating in number. The number of individuals in the lower Amur River population at age 2 or greater was recently estimated to be 40 000, and in the middle Amur, 30 000. The population will continue to decline because of rampant overfishing. The Amur sturgeon is represented in the Amur River basin by two morphs: brown and gray. Brown morphs occur in the middle and lower parts of the Amur River; they grow more slowly than the gray ones. Today, the lower Amur River population of Amur sturgeon is made up of 95 000 fish at age 2 or greater and is approximately half as large as the population in the middle Amur River. Populations of kaluga and Amur sturgeon in the Zeya and Bureya rivers are extremely small and on the verge of extinction.     

东海表层沉积硅藻组合与环境关系研究

对东海表层沉积硅藻分析研究,共发现有103种和变种,根据其中分布特征和规律,结合因子负荷变化曲线,把东海表层沉积分为六个硅藻组合和分布区,并探讨影响硅藻分布的环境因素,为恢复古环境提供科学依据。     

Macrozoobenthic Communities of the Piedmont and Lowland Watercourses of the Lower Amur Region

On the basis of 120 original stations, macrozoobenthic communities of rivers from two adjacent areas of the Lower Amur Region (Khabarovsk krai) have been described. Rivers basins are characterized by contrasting landscape conditions: the Anyuy River basin in the piedmonts of the Sikhote-Alin mountain range and the Simmi River basin on the Amur Lowland. About 250 taxa of macroinvertebrates have been found; 16 types of communities have been described. The principal differences in both benthic fauna and macrozoobenthic communities in the basins of the Anyuy River (cold-water rheophilic fauna as well as ritral and crenal communities predominate) and the Simmi River (warm-water limnophilic fauna and phytal communities predominate) are shown. We discuss the reasons for these differences, specific features of the fauna and communities of the whole region, and the biogeographical position of the region.     

Diatoms as a proxy in reconstructing the Holocene environmental changes in the south-western Baltic Sea: the lower Rega River Valley sedimentary record

This study focuses on diatom assemblages occurring in cores of Late-glacial and Holocene deposits retrieved from the mouth of the lower Rega River valley, of the southern coast of the Baltic Sea. Sediment samples from four cores were the subject of the present study. Diatom-inferred environmental characteristics, e.g., water level; water salinity (conductivity), trophic status and pH, within each core are presented. Diatom assemblage zones (DAZ) were distinguished, based on differences in the distribution of particular ecological groups. Each DAZ appears to be related to environmental changes during the deposition of a given sediment interval. The Late-glacial (Allerød) sediments originated in a shallow lake with increasing concentrations of solutes and nutrients. The Holocene record begins in the early Atlantic Chronozone and the diatoms point to weakly brackish-water sediments deposited in a shallow water environment. During the period of 8,500–5,800 cal year BP sedimentation took place in a shallow embayment and/or lagoon. From ca. 5,800 cal year BP onwards sedimentation took place in a peat bog environment alternating with Aeolian deposition. Changes in diatom community structure imply a close relationship with the climate-controlled eustatic rise of the ocean level and its consequence Littorina transgression. As with other southern Baltic Sea localities, brackish-water diatoms appear in the sediments, signaling the onset of marine transgression somewhat earlier than previously accepted. Differences and similarities in diatom assemblages and the palaeogeographic development of nearby regions within the Baltic Sea basin and lagoons (coastal areas) from different geographic regions, are also discussed.     

Diversity and abundance of ammonia-oxidizing prokaryotes in sediments from the coastal Pearl River estuary to the South China Sea

In the present study the diversity and abundance of nitrifying microbes including ammonia-oxidizing archaea (AOA) and betaproteobacteria (beta-AOB) were investigated, along with the physicochemical parameters potentially affecting them, in a transect of surface sediments from the coastal margin adjacent to the Pearl River estuary to the slope in the deep South China Sea. Nitrifying microbial diversity was determined by detecting the amoA (ammonia monooxygenase subunit A) gene. An obvious community structure shift for both AOA and beta-AOB from the coastal marginal areas to the slope in the deep-sea was detected, while the OTU numbers of AOA amoA were more stable than those of the beta-AOB. The OTUs of beta-AOB increased with the distance from the coastal margin areas to the slope in the deep-sea. Beta-AOB showed lower diversity with dominant strains in a polluted area but higher diversity without dominant strains in a clean area. Moreover, the diversity of beta-AOB was correlated with pH values, while no noticeable relationships were established between AOA and physicochemical parameters. Beta-AOB was more sensitive to transect environmental variability and might be a potential indicator for environmental changes. Additionally, the surface sediments surveyed in the South China Sea harboured diverse and distinct AOA and beta-AOB phylotypes different from other environments, suggesting the endemicity of some nitrifying prokaryotes in the South China Sea.     

On the systematics and phylogeography of eight-barbel loaches the genus Lefua (Cobitoidea: Nemacheilidae): mtDNA typing of L. pleskei

Comparative analysis of personal sequence data for the mtDNA control region (926 to 928 bp) from eight-barbel loaches inhabiting eight localities in the Amur River basin (4) and the Sea of Japan (4) and the GeneBank/NCBI data for the Lefua individuals from the other regions of the world showed that eight-barbel loaches from Primorskii krai water basins were marked by a specific group of mtDNA haplotypes. This finding is considered as supporting the species status of L. pleskei. Genetic distances within L. pleskei are small (on average 0.355) and close to those within L. nikkonis (on average 0.48%). The distances between this species pair are the least (on average 2.15%) among all other pairs compared. In MP, ML, and Bayesian trees, L. pleskei and L. nikkonis haplotypes formed a common clade with high statistically significant support. In all tree variants, L. costata mtDNA haplotypes were located out of the group of interest. A clade consisting of highly diverged lineages of Lefua sp. and L. echigonia haplotypes occupied even more independent position. The mtDNA haplotypes of L. pleskei and L. costata from the Amur River basin were evolutionary young and derived from the haplotypes found in these species from the Sea of Japan (L. pleskei) or the Yellow Sea (L. costata) basins. It is thereby suggested that both species rather recently migrated into the Amur River system. According to the molecular clock data, basal diversification of the eight-barbel loach lineages took place at the end of middle Miocene (about 11 to 12 Myr ago), while divergence of L. pleskei and L. costata ancestral forms probably occurred approximately, 5 Myr ago. Since all main lineages of eight-barbel loaches were found in the Sea of Japan basin (continental coastline and the islands), the divergence order and dispersal patterns of the Lafua species might have been largely determined by the geological development pattern of this water body and the adjacent territories.     

Distribution patterns of diatom surface sediment assemblages in the Laptev Sea (Arctic Ocean)

The modern diatom distribution in the Laptev Sea, Arctic Ocean, was investigated in 89 surface sediment samples. Diatom concentrations are relatively low showing values between 0.01×10⁶ and 6.7×10⁶ valves per gram dry sediment. Based on a factor analysis using seventeen taxa or taxa groups five diatom surface sediment assemblages can be defined: the ice diatom assemblage of the central region of the Laptev Sea, the Chaetoceros assemblage of the eastern and southeastern shelf, the Thalassiosira antarctica assemblage of the continental slope and deep sea, the freshwater diatom assemblage in the vicinity of river mouths and deltas, and the Thalassiosira nordenskioeldii assemblage which shows a patchy occurrence on the central Laptev Sea shelf. The distribution pattern of diatom assemblages in surface sediment is significantly related to oceanographic conditions of surface water masses. The main factors controlling the distribution of diatoms in the Laptev Sea are the riverine freshwater input during the summer which strongly affects the salinity conditions, and the sea-ice extent. Furthermore, the composition of the Thalassiosira antarctica assemblage of the continental slope is largely influenced by dissolution and lateral transport processes.     

Ichthyofauna of the Lena River (Laptev Sea Basin): Modern composition and historical formation

The modern ichthyofauna of the Lena River includes 46 species and subspecies: 45 bony fishes and one lamprey. In the upper reaches, 24 species have been recorded, 38 in the middle reaches, 36 in the lower reaches, and 24 in the delta. Four of the seven species intentionally introduced into water bodies of the Lena River basin have successfully naturalized; the presence of the others is unconfirmed. All areas of the river are dominated by fishes of the orders Salmoniformes and Cypriniformes. The ranges of the Amur carp Cyprinus rubrofuscus, common bream Abramis brama, ide Leuciscus idus, roach Rutilus rutilus, pike Esox lucius, and perch Perca fluviatilis have expanded over the last few years. The causes and possible ways of the historical formation of the Lena River fish population are discussed in the light of data on the Pleistocene paleogeographical events and patterns of the distribution of species in the river and in adjacent basins.     

Phytoplankton of the Amur River Estuary (Sea of Okhotsk) during the summer periods of 2005–2007

The qualitative composition of planktonic microalgae in the Amur River Estuary (in the Sea of Okhotsk) was studied in July 2005, June 2006, and June 2007. The biomass and abundance of phytoplankton were studied for the first time. The average cell density of the microalgae ranged from 194700 to 855100 cells/liter, being higher in 2006 than in 2005 and 2007. The average biomass of the community varied from 1.06 g/m³ in 2007 to 3.17 g/m³ in 2006. Analysis of the similarity of the species composition and cell density of the phytoplankton revealed two groups of stations: the first includes stations in the northern and central parts of the Amur Estuary; and the second includes stations in the southern and central parts. The first group was characterized by the predominance of freshwater diatoms and a high abundances of green and blue-green algae and the second group was characterized by the predominance of marine microalgae. The high cell density and biomass of phytoplankton were due to the increased nutrient input via the river runoff of the Amur.     

Across Siberia and over Europe: Phylogenetic relationships of the freshwater fish genus Rhodeus in Europe and the phylogenetic position of R. sericeus from the River Amur

We present the phylogenetic relationships of the freshwater fish genus Rhodeus from 45 localities in Europe and three localities in the Amur basin using the mitochondrial cytochrome b sequence. The study aims to (1) test the colonisation history between Europe and East Asia and (2) to reconstruct the evolutionary history of Rhodeus in Europe. Our analyses revealed five monophyletic clades which correspond to four species: R. sericeus in the Amur basin, R. meridionalis in the River Vardar, R. colchicus in western Caucasus and two sister lineages in most of Europe which together represent R. amarus. The reconstructed colonisation scenario assumes a continuous distribution of Rhodeus from Europe through Siberia until East Asia during Pliocene, depletion of the Siberian population in late Pliocene, isolation of the population in River Vardar during early Pleistocene, refuges during late Pleistocene glaciations in the Danubian basin, in the lowlands of western Black Sea and in western Caucasus Mountains and a post-glacial expansion from the Danubian refuge towards western Europe and from the Black Sea refuge across Eastern Europe.     

Ecological Risk Assessment of Arsenic and Metals in Surface Sediments from Estuarine and Coastal Areas of the Southern Bohai Sea,China

Distribution and magnitude of arsenic and metals in surface sediments collected from the coastal and estuarine areas of the southern Bohai Sea, China, were investigated. Sediments from the estuarine and coastal areas of the Jie and Xiaoqing Rivers contained highest concentrations of arsenic, cadmium, copper, mercury, and zinc. Mean concentrations of Cu, Zn, Cr, Pb, and Cd were higher than background concentrations determined for the areas. The magnitude of both enrichment factors (EF) and geoaccumulation indices (I_geo) suggested that pollution with As and metals was occurring along estuarine and coastal areas of the southern Bohai Sea. Risk analysis also suggested that concentrations of As and metals were sufficiently elevated as to cause adverse biological effects in the study area. According to the ecological risk index (RI) values, the upstream of the Jie River has a very high ecological risk for the waterbody. The data provided in this study are considered crucial for controlling and remediation of As and metals’ pollution of the southern Bohai Sea.     

Benthic Diatoms of the Russian Waters of the Sea of Japan and Adjacent Sea Areas

Russian Journal of Marine Biology - This review analyzes the current state of knowledge of the microphytobenthos in the Russian waters of the Sea of Japan and adjacent sea areas. A retrospective...     

An immunochemical in situ approach to detect adaptation processes in the photosynthetic apparatus of diatoms of the Wadden Sea sediment surface layers.

Intertidal Wadden Sea sediment surface layers located near the North Sea shore at Dangast (Germany) were subjected to quantitative chlorophyll and protein extractions followed by SDS-PAGE and Western immunoblotting. During the study, benthic diatoms were almost exclusively the only group of microphytobenthos in this area performing oxygenic photosynthesis. Three successive extractions with 90% acetone yielded more than 98% of the extractable pigments. The absorption spectra of the extracts of sediment samples were nearly identical to those obtained from the diatom Phaeodactylum tricornutum. Ten repetitive extractions with SDS containing loading buffer used for SDS-PAGE ensured that more than 98% of the extractable protein was recovered. Subsequent Western immunoblotting with an antiserum directed against the subunits of the main light harvesting complex of the diatom Cyclotella cryptica showed that the antiserum immunodecorated selectively subunits of diatomaceous light harvesting complexes. This finding demonstrated that a taxon specific class of polypeptides could be visualized and quantified directly in sediment samples. In shading experiments, shaded sedimient areas generally revealed higher amounts of light harvesting subunits which could be immunodecorized. The improved mnethodological approach and the results are discussed in the context of the current development of direct molecular methods for the investigation of activities and adaptation processes of specific groups of microorganisms in their natural habitats.     

Genetic analysis of four wild chum salmon<Emphasis Type="Italic">Oncorhynchus keta</Emphasis> populations in China based on microsatellite markers

Synopsis To assess the genetic variation and population structure of wild chum salmon in China, we analyzed microsatellite loci for populations in the Amur, Wusuli, Suifen Current and the Tumen rivers. We evaluated expected heterozygosity with two estimators of genetic differentiation (F_ST and G_ST) and Nei’s standard genetic distance. The average expected heterozygosity across the 10 loci was 0.65 in the Wusuli River and the Suifen Current River, 0.64 in the Amur River and 0.66 in the Tumen River, The results of this study show that the recent declines in chum salmon have not led to low levels of genetic variability in China. The proportion of inter-population subdivision among chum salmon was between 5.7 and 6.8%. According to the estimator used, the NJ tree based on Nei’s standard genetic distance indicated that there were two different branches (the Sea of Okhotsk branch and the Sea of Japan branch), the Amur River and the Wusuli River populations were closer, while the Suifen Current River and the Tumen River clustered together. The genetic test for population bottlenecks provided no evidence for a significant genetic signature of population decline, which is consistent with the record of the four populations we have in the last few years.     

The Spore-Pollen and Algal. Assemblages from the Surface Sediments of Yellow Sea

Yellow Sea is a shelf sea situated between China and Korea Peninsula. The distribution of spore-pollen and algae of the surface sediments of Yellow Sea may be divided into 4 characteristic regions:1. Artemisia-Chenopodiaccae-Gramineae region. 2. Pinus-Quercus-herbaceous pollen-Hystrichosphaera region. 3. Pinus-Balti-sphaeridinm-Quercus-Pteridium-Pteris region. 4. Pinus-Quercus-Pteris-Baltisphaeridium region. Through the study of spore-pollen and algae, the problems under discussion are: 1. the relationship between the spore-pollen assemblages of surface sediments and vegetation of continental margin, 2. resedimentation of fossils of spore-pollen and sedimental provenance of the sea basin, 3. the relationship between the distribution of Hystrichosphaera and Baltisphaeridium and water depth, 4. the relationship between the distribution of diatom and depth and characteristics of water bodies and 5. the relationship between mangrove pollen and sea currents.     

Seasonal variation in diet of juvenile Amur sturgeon Acipenser schrenckii in the lower reaches of the Songhua River,Northeast China

We investigated seasonal variation in the diet of hatchery-reared juvenile Amur sturgeon Acipenser schrenckii in the Tongjiang reach of the Songhua River, Northeast China. The results indicated that Amur sturgeon fed mainly on Chironomidae and Ephemeroptera and secondarily on unspecified bony fish, Odonata, and Trichoptera. Diet changed throughout the year, with autumn 2017 and spring 2018 dominated by Ephemeroptera larvae, while summer 2018 prey comprised primarily Chironomidae larvae. Unspecified bony fish were observed at greater frequency in autumn 2017. Amur sturgeon captured in summer contained a greater quantity of Trichoptera larvae compared to those from autumn and spring sampling. Results were consistent with previous reports of Amur sturgeon diet in other areas of its native distribution and suggested that they may be opportunistic feeders throughout the year, although larval Chironomidae and Ephemeroptera appear to be important prey. These results represent the first reported diet composition data for juvenile Amur sturgeon in the lower Songhua River. Results of the study form part of a comprehensive investigation of feeding habits of juvenile Amur sturgeon that provides basic data for study of the biological characteristics of the species.     

Biogeographic zonation of the Black Sea and Caspian Sea basin based on Mysid fauna (Crustacea: Mysidacea)

A biogeographic analysis of the Black Sea and Caspian Sea basin and adjacent Aegean Sea and the Sea of Marmara was conducted based on the distribution of 55 mysid species. The Black and Caspian Sea basin proper is inhabited by 35 mysid species belonging to 12 genera, among them 26 species and 3 genera are endemic to the region. Ponto-Caspian and Caspian species are predominant. The explored areas were included into two provinces of the Mediterranean subrealm of the East-Atlantic Subtropical realm and three provinces of the Ponto-Caspian realm.