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A review of the long‐term changes and variations in benthic communities and the current status of the marine invasive species (MIS) in shallow waters of the Yellow Sea (Chinese sector) and the Sea of Japan (Russian and partly Korean sectors) is presented. This paper reflects on the progress and lessons learned, recommending actions for the future about the conservation of biodiversity. In the Bohai Sea, the benthic ecosystem has been degenerating due to anthropogenic activities such as overfishing and pollution since the 1950s. The dominant position of K‐strategy species is gradually being lost and replaced by R‐strategy species. In the Yellow Sea, the macrobenthic community is different from other areas due to the Yellow Sea Cold Water Mass. Many economic species have been destroyed, and the biotic structure has changed significantly due to overfishing and climate change. In the Russian sector of the Sea of Japan, the macrobenthic communities in the shallow‐water soft bottom have generally been in a stable condition for the last decades, except for some heavily polluted or disturbed areas due to dredging operations. The abundance of select large invertebrate species has changed considerably due to commercial fishing and poaching. Variations in macro‑ and meiobenthic communities under aquaculture conditions have occurred on a local scale during the last five decades. MIS show obvious differences between China and Russia in the following aspects: introduction pathways of MIS, composition and number of non‐native species, threats and impacts of MIS to native communities and ecosystems, and economic and public health impacts. Long‐term monitoring programmes should be developed to reveal future biotic changes and to separate the effects of cyclic variations of benthic communities from the impacts of pollution and eutrophication. Standardization of sampling procedures is required to compare changes/alternations in benthos across various regions worldwide.

According to COI DNA barcoding testing, the marine bivalve mollusc Mactra chinensis, which is native to the Asia-Pacific region, diverged into three species. These species were preliminary characterized as M. chinensis COI clade I, M. chinensis COI clade II and M. chinensis COI clade III. To find out whether it is possible to morphologically distinguish samples representing genetic clades, we examined the color of the shells and the structure of the spermatozoa. It was found that the number of detected coloration types exceeds the number of detected species. In addition, it was shown that individuals belonging to the same genetic clade can have shells of different colors. Consequently, it is impossible to choose one type of shell coloration as a species-specific trait. For sperm, the sperm morphological patterns found in each of the three species are consistent with the M. chinensis sperm model described in previous reports. However, the single sperm variant is also not applicable to discriminate between species derived from M. chinensis, since heterogeneous variants of spermatozoa differing in the length of the acrosomal rod were found. We hypothesized that genetic divergence of species could cause a shift towards predominance of one of the sperm variants, and that species-specific sperm morphs could be quantitatively dominant in molluscs belonging to different clades. However, the dominant sperm morphs were the same in COI clade I and COI clade III. Thus, dominant sperm morphs are useless as species-specific traits. However, shell color and sperm parameters are specific to different geographic regions, and it seems that unique environmental factors can determine shell color and sperm morphology. As a result, both shells and spermatozoa can be used to distinguish the geographical forms of M. chinensis, regardless of the belonging of the forms to a particular genetic clade. Here we propose the introduction of geographic identifiers, in which the shell color and parameters of sperm sets are used as morphological criteria to determine the geographical origin of mollusc specimens belonging to the M. chinensis species complex.

На пляже м. Шелеха (зал. Посьета) изучали распределение пустых раковин, створок и фрагментов двустворчатого моллюска Glycymeris yessoensis (Sowerby III, 1889). Всего было взято 13 проб с площади 1 м², плотность раковинного материала варьировала от 4 до 44 экз./м². Доля целых раковин от общего числа экземпляров на всем пляже невелика – 14%, т.к. раковины этого вида легко дисартикулируются при высыхании лигамента. Однако удельный вес экземпляров (от общего числа обнаруженных во всех пробах раковин и створок) с механическими повреждениями (12%) и со следами сохранившегося периостракума (31%) указывает на незначительное или кратковременное волновое влияние факторов механической деструкции, что подтверждает также небольшой удельный вес фрагментов (от общего числа всех экземпляров) – 9%. Довольно высокая доля экземпляров со следами длительного пребывания в составе донных осадков (дисколорация и следы растворения/ биоэрозии) (в среднем 29%, до 40–44% по пробам) свидетельствует о комплексном воздействии тафономических процессов на танатоценозы глицимериса в сублиторали и на пляже, расположенного в промежуточных по своим эколого-литологическим условиям районе – переходном от полузакрытой бухты в открытую акваторию. Ключевые слова: тафономия, деструкция раковин моллюсков, танатоценозы пляжа, Японское море. The distribution of empty shells, valves, and fragments of the bivalve mollusk Glycymeris yessoensis (Sowerby III, 1889) was studied on the beach of Cape Shelekha (Possjet Bay). A total of 13 samples were taken, each from an area of 1 m², the density of shell material varied from 4 to 44 specimens/m². The proportion of complete shells of the total number of specimens on the whole beach is low, 14%, because shells of this species are easily disarticulated when the ligament dries. However, the proportions of specimens (of the total number of shells and valves found in all samples) with mechanical damage (12%) and with traces of the preserved periostracum (31%) indicate an insignificant or short-term wave effect of mechanical destruction factors, which is also confirmed by the low proportion of fragments (of the total number of all specimens) – 9%. A rather high proportion of specimens with traces of a long repose in the bottom sediments (exemplified by discoloration and traces of dissolution/bioerosion) (on average 29%, up to 40–44% in samples) indicates a complex effect of taphonomic processes on the thanatocenosis of the G. yessoensis shells in the subtidal zone and on the beach. The studied area is intermediate in terms of ecological and lithological conditions and is transitional from a semi-closed bay to an open water area. Key words: taphonomy, destruction of mollusk shells, beach thanatocenoses, Sea of Japan.

On the basis of nucleotide sequences of three nuclear genes and using molecular phylogenetic and evolutionary genetic approaches, the phylogeny of the main representatives of one of the largest taxa of bivalve mollusks, the family Mytilidae, was studied, and its system and taxonomy were refined. A phylogenetic system for the family Mytilidae and closely relative taxa of the order Mytilida, which currently has no consensus among specialists on the basis of traditional characters, is presented. Using nucleotide sequences of the 28S rRNA, 18S pRNA, and histone H3 genes, this consensus was established by the study of Mytilidae. Some concerns of mussel systematics were resolved; in particular, the monophyly of the family Mytilidae Rafinesque, 1815 was established with the strongest support for the subfamily Mytilinae Rafinesque, 1815. The data obtained disprove Distel’s conclusion on polyphyly of the subfamily Mytilinae Rafinesque, 1815. Isolation of the taxa in the rank of the Modiolinae G. Termier & H. Termier, 1950 and Bathymodiolinae Kenk & Wilson, 1985 subfamilies in the family Mytilidae and also the family Septiferidae Scarlato et Starobogatov, 1979 was confirmed, although the rank of the later taxon is not universally recognized and it remains to be clarified in an additional study.

The soft-shell clam Mya arenaria Linnaeus, 1758 is a commercially important fishery resource that occurs in boreal and temperate environments in the Northern Hemisphere. Whether the soft-shell clam is a single species with a circumboreal range or a species complex also comprising Mya japonica Jay, 1857 distributed in the north Pacific has long been debated by malacologists and palaeontologists based on slight differences in shell morphology. We used an integrative taxonomic approach incorporating available Mya spp. mitochondrial COI and 16S rRNA, and nuclear 28S rRNA gene sequences, as well as spermatozoan and shell morphological characters to test the validity of M. japonica and examine the range of soft-shell clam distribution. Although differences in shell morphology were minor, the results from tree topologies, pairwise uncorrected p-distances, Automatic Barcode Gap Discovery (ABGD) and spermatozoan ultramorphological data confirm the validity of M. japonica in both its endemic region in the northwest Pacific, and as here newly reported introduced populations in British Columbia in the northeast Pacific, and show that M. arenaria is distributed in the northeast Pacific, North Atlantic, Barents Sea (Arctic Ocean) and Mediterranean. We estimate these two closely related sister species diverged 4.1-12.5 Myr during early Pliocene to late Miocene, which is consistent with current evolutionary theory regarding M. arenaria. In addition, ABGD indicated the congener Mya truncata Linnaeus, 1758 may represent a species complex, but additional evidence is still needed to clarify its taxonomic status.

Observations in beach, intertidal and upper subtidal environments in Peter the Great Bay (north-western East Sea) have shown that attached algae were found on empty shells of 13 species of epifaunal and infaunal bivalve mollusks. Thirteen algae species were identified on empty dislodged shells but more than 50 species are known to be epibiotic on living bivalves. The dislodgement of shells with attached algae takes place in semi-enclosed, low-energy areas, as well as those which are open and affected by strong wave action, indicating the large scale of this phenomenon. The significance of seaweed transportation of living mollusks and their empty shells in the coastal zone, involving both taphonomic and ecological processes, is stressed. Algae appear to be a taphonomic agent and play a similar role as compared to birds or hermit crabs, but they act passively and contribute to environmental mixing in death assemblages in coastal environments.

The biogeography and diversity patterns of the marine bivalve molluscan fauna of the East Sea coast of South Korea are analyzed. The total species richness of the continental Korean bivalve fauna, excluding insular regions (Dok-do and Ullung-do), is 304, and from north to south the species richness of bivalves increases showing a clear gradient: Gangwon, 143 species → Gyeongbuk, 131 → Gyeongnam, 183. A zonal-geographical analysis of the entire fauna shows that the great majority are warm-water mollusks, constituting 77% (subtropical, 37%, tropical-subtropical, 30%, subtropical-boreal, 10%), The number of boreal (low-boreal, widely distributed boreal and circumboreal) species is lower, 19%, whereas boreal-arctic mollusks have only 4%. This demonstrates that the bivalve molluscan fauna of the eastern coast of Korea is subtropical, and has more affinities to the fauna of the East China Sea than to the northern East Sea. Separate analysis by provinces shows the increasing role of warm-water mollusks from north to south. While tropical-subtropical and subtropical species constitute 47% (68 species) in Gangwon, their dominance increases to 71% (93 species) in Gyeongbuk, and to 80% (148 species) in Gyeongnam. The Gyeongnam bivalve fauna is the most diverse in species composition and has the largest number of “endemics” (species known only from this province), 46%. The Gangwon fauna also contains many “endemics”, up to 40%, while Gyeongbuk is an intermediate zone with low “endemicity”, only at one-fifth of the regional fauna, and has the most species in common among the three provinces.

The bivalve molluscan fauna of Ulsan Bay, East Sea coast of Korea, is summarized, based on original and literature data. The fauna consists of 61 species belonging to 20 families. Seven species are identified only to genus level. Two species (Carditellopsis toneana (Yokoyama, 1922), Carditidae and Fulvia hungerfordi (G.B. Sowerby III, 1901), Cardiidae) are new records for the East Sea coast of Korea, and one species (Crenella decussata (Montagu, 1808), Mytilidae) is a new record for Korea. Biogeographically, Ulsan Bay’s bivalve fauna is subtropical with a predominance of tropical-subtropical species, 21 species, or 39% of the total species number, subtropical, 14 species, or 26%, and subtropical-boreal (mostly subtropical-lowboreal), 11 species, 21%, totalling 86%. A remarkable feature of the Ulsan Bay fauna is the presence of tropical-subtropical species not found in Yeongil Bay but common in tidal flats and shallow waters of the Yellow Sea and the southern part of Korea. A cold water mass appearing off the southeast coast of Korea near Ulsan in summer seems responsible for the presence of boreal-arctic species in this area.

Syntypes of fourspecies of bivalve molluscs — Nucula laternaria Valenciennes, 1846; Nucula amygdalea Valenciennes, 1846; and Nucula oeolica Valenciennes, 1846, all Yoldiidae; and Cardium californiense Deshayes, 1839, Cardiidae — collected from Kamchatka during the historic voyage of the Venus (1836–1839), are illustrated and their taxonomic status and distribution are discussed.

An annotated listing of bivalve mollusks collected at 31 sampling sites in Yeongil Bay (eastern coast of Korea) at a depth of 0-52m is presented here. A total of 98 species belonging to 75 genera and 36 families are enumerated; all species are provided with habitat data (bathymetric distribution and bottom sediments character), given separately far living and dead (empty shells) specimens, and some with taxonomic and zoogeographic comments. Fifty-six species are illustrated with photographs. Astarte hakodatensis Yokoyama, 1920 (Astartidae), Nitidotellina pallidula (Lischke 1871) (Tellinidae) and Lyonsia nuculanoformis Scarlato in Volova et Scarlato, 1980 (Lyonsiidae) are found to be new to the Korean fauna, and the genus Salaputium Iredale, 1924 (Crassatellidae) with one species Salapurium Iredale, 1924(Crassatellidae) with one species Salaputium cf. unicum Hayami and Kase, 1993, previously described as being found only from submarine caves in the Ryukyu Islands, is recorded as being found in the East Sea(Sea of Japan) for the first time.

Natural middle-and late-Holocene environmental development of Kunashiri Island reflects global climatic changes and the migration of warm and cold currents. Dry and cool climate changed to warm and moist about 7000–6500 BP, later than on Hokkaido Island. At this time Kuroshio Current system became more active. On Kunashir Island birch assemblages were replaced by cool-temperate broadleaf forests in the south and mixed coniferous/broadleaf forests in the north. The highest sea-level position reached 2.5–3 m above PSL about 6500–6300 BP. Cooling about 4700–4500 BP island vegetation weakly changed that connected with warm current influence. Major regression at this period led to formation of extensive coastal dunefields. The warming at the beginning of the late Holocene was almost similar to the Holocene Optimum. Two minor transgressions are recorded about 4010–3400 and 2950–2620 BP. Active entrance of detrital material to the coastal zone resulted in growth of accumulative landforms. Vegetation changes and climatic deterioration took place in the second half of the late Holocene. Coniferous and mixed coniferous/broadleaf forests shifted southward and occupied a large part of the island. During cooling at 1700–1300 BP the isthmus area increased, coastal wetlands with lakes and coastal dunes were formed, and grassland and swamp landscapes developed. Late-Holocene warming was not intensive. Active aeolian accumulation took place during the ‘Little Ice Age’ cooling and regression.

132 The bivalve mollusk Mactra chinensis Philippi, 1847 is of significant commercial importance in the Asian–Pacific area; therefore, it is studied by malacol� ogists intensely. On the basis of morphological data, researchers suggested a divergence of this species in the Sea of Japan. As a consequence of the divergence, the southern and northern populations have already appeared which are different in the shape, color, and the shell pattern. For example, in the South Korean part of the Sea of Japan, the Mactra shell is described as faintly colored, yellowish, without any brown rays, while in the Russian part of the Sea of Japan, there is

LUTAENKO, KONSTANTIN A. (Laboratory of Benthos Ecology, Institute of Marine Biology, Far East Branch of Russian Academy of Sciences, and Zoological Museum, Far East State University). 1994. Beach Molluscan Thanatocoenoses in Possjet Bay, Sea of Japan : Comparison between Open and Sheltered Beaches. Benthos Research, 47: 1-12. Molluscan thanatocoenoses have been studied in 16 areas of the seashore of Possjet Bay (northwestern part of the Sea of Japan), and 58 species of bivalves, referred to 42 genera and 23 families, were identified. This is about 60% of the total number of bivalve molluscs inhabiting the Bay and surrounding waters. Peculiarities in the composition and taphonomy of the thanatocoenoses are described. The taxonomic composition of the beach thanatocoenoses of bivalve molluscs commonly reflects environmental variability in the shallow waters of Possjet Bay. There seems to be minimal postmortem migration of molluscan shells in Possjet Bay.

The geographical distribution of warm-water mollusks has been analyzed and the paleobiogeographical significance of the climatic optimum during the Holocene in the formation of the shallow-water malacofauna in the Sea of Japan has been assessed. The shift of the southern boundary of the Pacific boreal region was 700–800 km to the north compared to its present-day position (based on bivalve mollusks). On the continental coast of the Sea of Japan this boundary is observed in Peter the Great Bay (∼43°N) and on the Japanese side it seems to be at the central part of Hokkaido. It can be concluded that a temperature increase of the surface water mass of 0.1–0.2°C can cause a shift of about 100 km of the northern boundary of the area of warm-water mollusks.