Projections of climate-driven biogeographical changes of benthic mollusks in the Yellow Sea and East China Sea.

Climate change influences the distribution of many marine species. To project the biogeographical changes of benthic mollusks in response to climate change in the Yellow Sea and East China Sea, ensemble species distribution models (SDMs) were applied. Ensemble SDMs performed well for ten of the thirteen selected benthic mollusks with environmental variables including temperature, salinity, current velocity, and depth. Six cold water mollusks, including bivalves Acila mirabilis, Ennucula niponica, Ennucula tenuis, Nuculana yokoyamai, Pendaloma otohimeae and Megayoldia japonica, were projected to contract their habitats and move northward in 2050s and 2100s under all of the RCP2.6, 4.5, 6.0 and 8.5 climate scenarios, with temperature being the most important environmental variable. Two warm water mollusks (bivalves Nucula tokyoensis and Leptomya minuta) were projected to lose their suitable habitats under future climate scenarios (all RCP scenarios), while two (the gastropod Cylichna biplicata and the bivalve Moerella hilaris) were projected to expand their habitats to the deeper water area. The most important environmental variable varied among warm water species between temperature, salinity and depth. This study will contribute to better understanding the marine species biogeographical changes under climate change, and thus we can better protect their biodiversity.

Potential impacts of climate change on the distribution of echinoderms in the Yellow Sea and East China Sea.

To detect potential impacts of climate change on the distribution of common echinoderm species in the Yellow Sea (YS) and East China Sea (ECS), species distribution models (SDMs) were applied. Ensemble SDMs were constructed and were in good model performance for six of the eight selected common echinoderm species. Under future climate scenarios, the brittle stars Ophiopholis mirabilis, Amphioplus depressus and the sea cucumber Protankyra bidentata were projected to expand in the southwestern areas of the YS, the ECS, and the coastal areas of the YS and ECS, respectively; the brittle stars Stegophiura sladeni, Amphiura digitula and Amphiura vadicola will likely contract their ranges in the south distribution areas and expand in the north, showing a northward movement trend. Temperature was the most important environmental variable influencing the distribution of the latter three echinoderms. Our findings will improve our understanding of the impacts of climate change on marine species distributions.

A new species of the genus Lindaspio Blake & Maciolek, 1992 (Annelida, Spionidae) from a cold seep near Hainan Island, China.

A new species of the spionid genus Lindaspio Blake & Maciolek, 1992 was collected from a cold seep near the Hainan Island at a depth of 1758 m. Morphologically, Lindaspiopolybranchiatasp. nov. differs from the congeners in having a narrow, folded caruncle and more neuropodial branchiae (from chaetiger 20). The 18S, COI, and 16S sequences of the new species have been submitted to GenBank. It is the first record of the genus Lindaspio from Chinese waters. A key to all species of Lindaspio is given.

The complete mitochondrial genome of Mesochaetopterus japonicus (Sedentaria: Chaetopteridae).

The benthic and tube-building polychaete worm Mesochaetopterus japonicus is abundantly present on the coast of the western Pacific. Here, we report the complete mitochondrial genome of M. japonicus, which is 19,326 bp in length and contains 13 protein-coding genes, 2 rRNA genes and 22 tRNA genes. All 37 genes are encoded on the heavy strand, and AT content is 70.17%. Phylogenetic analyses based on the M. japonicus mitogenome combined with previously published polychaete mitogenome data revealed that M. japonicus was closely related to Chaetopterus variopedatus and Phyllochaetopterus sp., all of which belong to Chaetopteridae. The mitochondrial genome of M. japonicus could provide useful molecular resources for further research on Polychaeta phylogeny and evolution.

Potential effects of climate change on the habitat suitability of macrobenthos in the Yellow Sea and East China Sea.

Species distribution models (SDMs) are used to detect potential effects of climate change on the habitat suitability of macrobenthos in the Yellow Sea and East China Sea. We obtained the presence/absence data of five dominant and characteristic macrobenthos from 268 sites investigated during 2000-2016 and 13 environmental variables from online datasets. The ensemble SDMs were constructed and were in good model performance for all five species. Model projections showed that the five species displayed different reactions to future climate scenarios: two species (the ophiuroid Ophiura sarsii vadicola and the bivalve Thyasira tokunagai) will likely contract their ranges, two (the crab Xenophthalmus pinnotheroides and the polychaete Sternaspis chinensis) will likely expand their ranges, and one (the ophiuroid Amphioplus japonicus) will likely move northward. Those differences were mainly due to their difference in thermal tolerance. Our findings provide important scientific basis for understanding the influence of climate change on marine benthic ecosystems.

Report of epibenthic macrofauna found from Haima cold seeps and adjacent deep-sea habitats, South China Sea.

This work reports on a preliminary taxonomic study of epibenthic macroinvertebrates collected or observed by underwater video at the Haima cold seeps and in adjacent deep-sea habitats, including a mud volcano field and Ganquan Plateau, during an expedition in the South China Sea by the Chinese-manned submersible Shenhai Yongshi in May 2018. A total of 41 species belonging to 6 phyla were identified, among which 34 species were collected from the Haima cold seeps. Mollusks and crustaceans that are specialized in reducing habitats were predominant in biotopes of the Haima cold seeps, whereas sponges and cold-water corals and their commensals were prominent in communities of the mud volcano field and the slopes of Ganquan Plateau. The distribution and faunal composition of each taxonomic group are discussed.

A new species of the genus Amphicteis Grube, 1850 (Annelida, Ampharetidae) from the Yellow Sea, China, together with a redescription of A. dalmatica Hutchings & Rainer, 1979.

A new species of the ampharetid genus Amphicteis, A. hwanghaiensis sp. nov., is described based on material from the Yellow Sea. The new species is characterized by the possession of long, stout, golden paleae with blunt tips, digitiform rudimentary notopodia on the abdominal uncinigers, uncini with a subrostral process, and a narrow rectangular hump separating branchial groups. Amphicteis dalmatica was redescribed from type materials at the Australian Museum, Sydney, and the differences between A. dalmatica and A. hwanghaiensis sp. nov. are discussed. A key to distinguish Amphicteis species described or reported in Western Pacific waters is provided.

Review of the genus Loimia Malmgren, 1866 (Annelida, Terebellidae) from China seas with recognition of two new species based on integrative taxonomy.

Specimens of the genus Loimia (Annelida, Terebellidae) deposited in the Marine Biological Museum of the Chinese Academy of Sciences (MBMCAS) together with materials newly collected from China seas were examined. Based on morphological comparisons and molecular analysis, some specimens collected from the coasts of Shandong province and Guangxi province were confirmed as two new Loimia species respectively (Loimia borealis sp. n. and Loimia macrobranchia sp. n.). Morphologically, L. borealis sp. n. is distinguished from previously known species of this genus by having seven equal sized ventral shields, with length five times the width; this species was retrieved as sister to the clades of Loimia arborea Moore, 1903 and Loimia bandera Hutchings, 1990 in the phylogenetic tree, which was reconstructed based on mitochondrial COI gene. Loimia macrobranchia sp. n. differs from congeners by the large size of its first pair of branchiae with a thick main stem and about 18 dendritic branches arranged in two levels. A key to identifying Loimia species found in Chinese seas is given.

Temporal variation of macrobenthic community zonation over nearly 60 years and the effects of latitude and depth in the southern Yellow Sea and East China Sea.

To examine the temporal variation of macrobenthic community zonation over nearly 60 years and the effects of latitude and depth in the southern Yellow Sea and East China Sea, a total of 1386 box-corer samples from four large spatial scale studies during 1958-1959, 2000-2004, 2011-2013 and 2014-2016 period, respectively, were compiled. A total of 26, 14, 13 and 18 communities were identified, respectively during the four periods with the same analytical method. The Yellow Sea Cold Water Mass (YSCWM) community, restricted to the 34°N latitude in the south and 50 m isobaths in the west, varied little in its spatial pattern over nearly 60 years, while other communities did not. The representative species in the YSCWM community changed from the polychaetes to the brittle stars during 1958-2016. However, in other large spatial scale communities except the YSCWM community, the representative species changed from the echinoderms, nemerteans or crustaceans to the polychaetes. For the revisited locations across studies, significant temporal and spatial variations in community structure at both species and family levels were detected. Macrobenthic species with high consecutive contributions to the community similarity were significantly influenced by latitude, depth, temperature and salinity, among which latitude and depth were the first two most significant environmental variables. Species diversity increased from 32 to 37°N during 1958-1959, but decreased during 2014-2016. It seems that the latitude of 32°N is an ecological barrier for macrobenthic community and diversity, but its effects weakened from 1958 to 2016. Species diversity roughly showed a first increasing then decreasing trend with the increase of the water depth in the southern Yellow Sea and East China Sea.

Assessment of the benthic ecological status in adjacent areas of the Yangtze River Estuary, China, using AMBI, M-AMBI and BOPA biotic indices.

The main environmental variables of bottom seawater and macrobenthic invertebrates were investigated from February 2015 to January 2016 to evaluate the benthic ecological status in adjacent areas of the Yangtze River Estuary, China. Diverse ecological assessment results were given by the AZTI Marine Biotic Index (AMBI), multivariate-AMBI (M-AMBI) and benthic opportunistic polychaetes amphipods (BOPA) index, showing that the M-AMBI was the most suitable in the study area. A clear spatial distribution pattern related to the distance from the estuary and the coasts was found both for the benthic ecological status and the eutrophication-related bottom seawater environmental variables, indicating that the study area was under eutrophication pressure. Two major disturbed regions (one was east of the Yangtze River Estuary, and the other was east of Zhejiang Province) were discovered, which was probably mainly caused by the Changjiang Diluted Water (CDW). No significant seasonal changes were found in the ecological status.

The complete mitochondrial genome of Calyptogena marissinica (Heterodonta: Veneroida: Vesicomyidae): Insight into the deep-sea adaptive evolution of vesicomyids.

The deep-sea chemosynthetic environment is one of the most extreme environments on the Earth, with low oxygen, high hydrostatic pressure and high levels of toxic substances. Species of the family Vesicomyidae are among the dominant chemosymbiotic bivalves found in this harsh habitat. Mitochondria play a vital role in oxygen usage and energy metabolism; thus, they may be under selection during the adaptive evolution of deep-sea vesicomyids. In this study, the mitochondrial genome (mitogenome) of the vesicomyid bivalve Calyptogena marissinica was sequenced with Illumina sequencing. The mitogenome of C. marissinica is 17,374 bp in length and contains 13 protein-coding genes, 2 ribosomal RNA genes (rrnS and rrnL) and 22 transfer RNA genes. All of these genes are encoded on the heavy strand. Some special elements, such as tandem repeat sequences, "G(A)nT" motifs and AT-rich sequences, were observed in the control region of the C. marissinica mitogenome, which is involved in the regulation of replication and transcription of the mitogenome and may be helpful in adjusting the mitochondrial energy metabolism of organisms to adapt to the deep-sea chemosynthetic environment. The gene arrangement of protein-coding genes was identical to that of other sequenced vesicomyids. Phylogenetic analyses clustered C. marissinica with previously reported vesicomyid bivalves with high support values. Positive selection analysis revealed evidence of adaptive change in the mitogenome of Vesicomyidae. Ten potentially important adaptive residues were identified, which were located in cox1, cox3, cob, nad2, nad4 and nad5. Overall, this study sheds light on the mitogenomic adaptation of vesicomyid bivalves that inhabit the deep-sea chemosynthetic environment.

Relationship between mild seasonal oxygen deficiency and seasonal variations of macrozoobenthic community: A case study in the Yangtze River estuary and its adjacent area, China.

In the present study, environmental parameters and macrozoobenthos in the Yangtze River estuary and its adjacent area, China, were investigated in summer and winter of 2015, and significant seasonal differences were found. Biodiversity was found to be lower in summer, which may result from the higher deposition rate. The relationship between the macrozoobenthic community and environmental parameters (especially dissolved oxygen) was revealed. Linear models describing the response of macrozoobenthic biodiversity indexes to mild oxygen deficiency were constructed. Mild seasonal oxygen deficiency was revealed significantly related to seasonal variations of the macrozoobenthic community, but this deficiency could not damage the community. In contrast, when mild oxygen deficiency occurred, natural predators of macrozoobenthos decreased, which may relieve the survival pressure of macrozoobenthos to some extent. Dissolved oxygen alone could not explain many variations of macrozoobenthos, and other environmental parameters, especially water depth, phosphate concentration and turbidity, also greatly contributed to those variations.

Spatiotemporal patterns of the macrofaunal community structure in the East China Sea, off the coast of Zhejiang, China, and the impact of the Kuroshio Branch Current.

The Kuroshio Current intrudes in the bottom layer of the East China Sea continental shelf from the northeast of Taiwan via two bottom branches named the Nearshore Kuroshio Branch Current (NKBC, along the 60 m isobath) and the Offshore Kuroshio Branch Current (OKBC, along the 100 m isobath). However, knowledge on the macrofaunal responses to these bottom branches is limited. This study examined the variations in the benthic macrofaunal community in a section of the East China Sea under the influence of the NKBC. Seven sites corresponding to three regions (the west, middle and east region) were sampled using an Agassiz trawl net at a monthly rate from February to November 2015 (except in August). A total of 270 macrofaunal species were collected in this study. Cluster analysis and nMDS ordination revealed three communities: the inshore, Kuroshio and offshore communities, roughly corresponding to the west, middle and east of NKBC route. Significant differences in the species composition (one-way PERMANOVA) and diversity indices (one-way ANOVA) among the regions and communities were observed, while no statistically significant difference among the months was detected. The indicator species also varied among the communities, with Sternaspis scutata and Odontamblyopus rubicundus dominating the inshore community, Camatopsis rubida, Schizaster lacunosus and Craspidaster hesperus dominating the Kuroshio community, and Portunus argentatus, Champsodon snyderi and Coelorinchus multispinulosus dominating the offshore community. Some rare species (e.g., Neobythites sivicola) may indicate the passage of the NKBC better than the indicator species. A redundancy analysis was used to describe the relationship between the macrofaunal species and environmental variables in this study. Water depth and turbidity played important roles in the distribution of the macrofauna. S. scutata and O. rubicundus were associated with high turbidity and shallow depth, while Plesionika izumiae and P. argentatus were associated with low turbidity and deep depth. This study outlines the impact of the NKBC on the distribution patterns of the macrofaunal community of the East China Sea. More studies are needed to understand the detailed interactions between macrofauna and the NKBC in the future.

Long-term variation of the macrobenthic community and its relationship with environmental factors in the Yangtze River estuary and its adjacent area.

Using data from four periods from 1959 to 2015, we report the long-term variation of the macrobenthic community in the Yangtze River estuary and its adjacent area. In total, 624 species were collected, and Polychaeta was the dominant group. Significant differences between the four periods were found. The CCA (canonical correspondence analysis) and RDA (redundancy analysis) results revealed that temperature, salinity, and depth significantly influenced the macrobenthic communities (89.6% of the species-environment relationship variance was explained by the first two axes of CCA and 94.3% was explained by RDA). The results of K-dominance curves (the elevation increased over time), ABC (abundance/biomass comparison) curves (the W value changed from 0.311 to 0.167 during 1959 to 2014-2015) and the Shannon-Wiener index (log base=2; 2.29-5.03 in 1959, 2.86-4.55 in 2000-2001, 2.28-4.56 in 2011-2012, and 1.79-4.43 in 2014-2015) showed that the ecological status of the benthic study area was deteriorating.

A new species of Phyllocomus Grube, 1878 from the Yellow Sea, China (Annelida, Ampharetidae).

A new species of the ampharetid genus Phyllocomus, P. chinensissp. n., is described based on material from the Yellow Sea. The new species is distinguished from the known species of this genus by having two thoracic regions, with segments of the anterior region (up to thoracic chaetiger 10) approximately half as long as those of the posterior region, neuropodia of the anterior region are large while those of the posterior region become gradually smaller, thoracic neuropodia without dorsal cirrus, and abdominal neuropodia with a papillary dorsal cirrus. A key to all species of Phyllocomus is given.

A new species and new record of deep-sea scale-worms (Polynoidae: Polychaeta) from the Okinawa Trough and the South China Sea.

A new species of scale-worm, Lepidonotopodium okinawae sp. nov. from the Okinawa Trough is described. The new species differs from the other species of Lepidonotopodium by having 24 segments and numerous foveolae on the surface of elytra with one globular micropapilla in every foveola. A new record of the mussel commensal Branchipolynoe pettiboneae Miura & Hashimoto, 1991 is reported and described from the northern South China Sea, where for the first time the scale-worm is noted as occurring at a cold-seep. Keys to distinguish the species of Branchipolynoe and Lepidonotopodium are provided.

Pseudoamphicteis sinensis sp. nov., a new species of Ampharetidae (Polychaeta) from China.

A new species of the ampharetid genus Pseudoamphicteis, P. sinensis sp. nov., is described based on material deposited in the Marine Biological Museum of the Chinese Academy of Sciences (Qingdao). The new species is widely distributed from depths of 7-103 m in the Yellow Sea and the East China Sea. It is distinguished from the only other known species of this genus Pseudoamphicteis papillosa Hutchings, 1977 by its grooved branchiae. The genus has not previously been reported from China.