Coastal Waters Of China Research Articles

Preliminary study on the migration characteristics of swordtip squid (Uroteuthis edulis) based on the trace elements of statolith in the East China Sea

Uroteuthis edulis (U. edulis) is a commercially important cephalopod species widely distributed in the coastal waters of China. It has multiple cohorts and migration habits. Migration habits are important features in cephalopods’ life history. Trace elements derived from hard structures have been proved as a useful tool to study cephalopods. In this study, the statolith trace elements of spring and summer cohorts of U. edulis in the East China Sea were measured by Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The differences in both composition and concentrations of trace elements between different cohorts (spring and summer cohorts) were analyzed and the hatching temperature and area were estimated with key environmental variables. The analysis showed that calcium (Ca), sodium (Na), strontium (Sr), iron (Fe) and magnesium (Mg) were the top five elements in the spring and summer cohorts. The concentrations of the top five elements showed significant differences between two cohorts (P < 0.05). Ca, Na, Barium (Ba), Sr, Cobalt (Co), manganese (Mn) and lithium (Li) were selected as the key trace elements in two cohorts. Water temperature, salinity and mixed layer depth (MLD) were the key environmental variables affecting element concentration changes. In different growth stages of U. edulis life history, the ratios of Sr/Ca, Ba/Ca and Li/Ca in the summer cohort were higher than those in the spring cohort, whereas the ratio of Na/Ca in the summer cohort was lower than that in the spring cohort. The ratios of Sr/Ca and Ba/Ca in the two cohorts peaked in the embryonic period, and the differences in the ratios of Sr/Ca, Ba/Ca or Li/Ca between different growth stages were not significant (P > 0.05). The hatching water temperatures of spring and summer cohorts were 19∼ 24 °C and 18∼22 °C, respectively. The spawning ground of the summer cohort was potentially located in the center and northern part of the East China Sea. Therefore, Ca, Na, Sr, Fe and Mg elements are the potential elements for cohort discrimination and the ratios of Sr/Ca, Ba/Ca, Na/Ca and Li/Ca can be used as the potential indicators to construct the habitat history of U. edulis.

Integrative taxonomy and molecular phylogeny of three poorly known tintinnine ciliates, with the establishment of a new genus (Protista; Ciliophora; Oligotrichea)

BackgroundThe taxonomic classification of the suborder Tintinnina Kofoid & Campbell, 1929, a species-rich group of planktonic ciliated protistans with a characteristic lorica, has long been ambiguous largely due to the lack of cytological and molecular data for most species. Tintinnopsis is the largest, most widespread, and most taxonomically complex genus within this group with about 170 species occurring in nearshore waters. Previous molecular phylogenetic studies have revealed that Tintinnopsis is polyphyletic.ResultsHere we document the live morphology, infraciliature, gene sequences, and habitat characteristics of three poorly known tintinnine species, viz. Tintinnopsis karajacensis Brandt, 1896, Tintinnopsis gracilis Kofoid & Campbell, 1929, and Tintinnopsis tocantinensis Kofoid & Campbell, 1929, isolated from the coastal waters of China. Based on a unique cytological feature (i.e., an elongated ciliary tuft with densely arranged kinetids) in the former two species, Antetintinnopsis gen. nov. is erected with Antetintinnopsis hemispiralis (Yin, 1956) comb. nov. (original combination: Tintinnopsis hemispiralis Yin, 1956) designated as the type species. Moreover, A. karajacensis (Brandt, 1896) comb. nov. (original combination: Tintinnopsis karajacensis Brandt, 1896) and A. gracilis (Kofoid & Campbell, 1929) comb. nov. (original combination: Tintinnopsis gracilis Kofoid & Campbell, 1929) are placed in a highly supported clade that branches separately from Tintinnopsis clades in phylogenetic trees based on SSU rDNA and LSU rDNA sequence data, thus supporting the establishment of the new genus. One other species is assigned to Antetintinnopsis gen. nov., namely A. subacuta (Jörgensen, 1899) comb. nov. (original combination Tintinnopsis subacuta Jörgensen, 1899).ConclusionsThe findings of the phylogenetic analyses support the assertion that cytological characters are taxonomically informative for tintinnines. This study also contributes to the broadening of our understanding of the tintinnine biodiversity and evolution.

Genetic diversity of &amp;lt;italic&amp;gt;Platycephalus&amp;lt;/italic&amp;gt; sp.1 in coastal waters of China based on mtDNA &amp;lt;italic&amp;gt;cox&amp;lt;/italic&amp;gt;1 sequence

<italic>Platycephalus</italic> sp.1 is a commercially important trawling fish species widely distributed in the northwestern Pacific. For better protection and sustainable exploitation of this valuable fishery resource, sequences of partial mitochondrial <italic>cox</italic>1 gene of 155 individuals from 7 populations were determined to analyze genetic diversity of <italic>Platycephalus</italic> sp.1 in coastal waters of China. In total, 28 variable sites in the aligned 652 bp sequences determined 28 haplotypes, indicating low haplotype diversity (<italic>H</italic>_d = 0.428) and low nucleotide diversity (π=0.001 02). Fangchenggang, Lianyungang and Fuzhou population possessed the highest (<italic>H</italic>_d = 0.864), the second (<italic>H</italic>_d = 0.489) and the lowest (<italic>H</italic>_d = 0.298) haplotype diversity, while Fangchenggang, Lianyungang and Nantong population had the the highest (π=0.003 02), the second (π=0.001 24) and the lowest (π=0.000 61) nucleotide diversity respectively. Significant genetic differentiation existed between Fangchenggang population and other populations (east of Qiongzhou Strait population, composed of Dalian, Weifang, Lianyungang, Nantong, Fuzhou and Jieyang). The pairwise <italic>F</italic>_st between Fangchenggang population and east of Qiongzhou Strait population were significantly different, ranging from median to high level(0.088 61-0.189 29). Meanwhile, the result of AMOVA showed that molecular variation between Fangchenggang population and east of Qiongzhou Strait population explained 24.19 % of variance within the whole population. A star-like haplotype network indicated weak phylogenetic lineage and a possible recent fast population expansion. Furthermore, negative neutrality test result (<italic>D</italic> = -1.024, <italic>P</italic> = 0.152; <italic>F</italic>_s =-2.60, <italic>P</italic>=0.015) and unimodal mismatch distribution curve indicated a possible population expansion in Fangchengguang population around 167-56 Ka B.P. in the last interglacial period. Significant negative neutrality test result (<italic>D</italic>=-2.468, <italic>P</italic>= 0.000; <italic>F</italic>_s = - 34.02, <italic>P</italic>=0.000) and the nearly Z-shaped Bayesian skyline plot suggested a population expansion in east of Qiongzhou Srait population around 25-30 Ka B.P. in the late last glacial period. It is hypothesized that ancient <italic>Platycephulas</italic> sp.1 population had expanded in the last interglacial period, then returned to refuge in the last glacial period because of sea level drop. In the late last glacial period, it spreaded out in coastal waters of China with rising sea level and achieved population expansion. Simultaneously, Fangchenggang population gradually adapted to its environment and differentiated from east of Qiongzhou Strait population because Qiongzhou Strait had separated each other and restricted their exchange of eggs, larvae and juveniles via currents. By contrast, east of Qiongzhou Strait population was more homogeneous under the influence of current cycle and possible reproductive migration. Due to significant genetic differentiation on either side of Qiongzhou Strait, Fangchenggang population and east of Qiongzhou Strait population should be set as two independent management units respectively. As Fangchenggang population owned the highest genetic diversity, it should be protected in priority for exploitation. It is also recommended to protect Dalian population and to take measures to avoid the decrease of genetic diversity of Nantong population since they owned the highest and the lowest nucleotide diversity in east of Qiongzhou Strait population respectively.

Effects of Wave–Current Interaction on the Eastern China Coastal Waters during Super Typhoon Lekima (2019)

AbstractLekima was a devastating super typhoon hitting China in 2019. Here, we use a high-resolution wave–current coupling model to investigate the impacts of wave–current interaction during Lekima on wave height, storm surge, ocean currents, and momentum balance. The model results were in good agreement with observations. It was found that, in the open waters, the strong currents generated by the typhoon winds reduced the typhoon-induced maximum significant wave heights (MSWHs) by 6%–15%. The baroclinicity of seawater also slightly reduced the MSWHs by approximately 3%. In the coastal waters, the MSWHs were increased by 6%–15% when feedbacks from water levels were considered. The typhoon-induced highest storm surge occurred in the coastal waters right of the typhoon’s landing position. The nonconservative wave forces contributed by approximately 0.1–0.4 m to the most severe storm surge (3 m), with this effect being most prominent in coastal waters. The baroclinicity of seawater generally increased the storm surge but had little influence on very shallow waters. Tides tend to exacerbate storm surge in most nearshore waters, except in a small bay. Waves generally increased the velocity of offshore ocean currents via the wave-breaking-induced acceleration. A cross-shore momentum balance analysis shows that when the typhoon was near the shore, the dominant terms in the momentum equation were the horizontal pressure gradient force and the surface wind stress, and the contribution of wave breaking had similar pattern to that of the wind stress but a lower magnitude. Our findings have significant implications for the numerical modeling of typhoons and the prediction of their impacts in the coastal environment.

Distribution and Flora of Seaweed Beds in the Coastal Waters of China

Seaweed plays an important role in energy production in marine, coastal, and island ecosystems. The protection of seaweed beds is a key point for coastal ecosystem health, but the community characteristics, dominant species, and distribution of seaweed beds in the coastal waters of China are still unknown. Dividing seaweed beds based on their ecological function is also required for coastal ecosystem conservation, marine development, and utilization. We conducted ecological surveys on various types of ecosystems at approximately 50 sites dedicated to the conservation of seaweed bed biodiversity in China from 2018 to 2019. These seaweed beds were classified into different flora by water temperature and the attributes of the dominant species. The study showed that Sargassum dominated the coast of China. The coverage of the genus Undaria and the genus Laminaria in the coastal waters of Liaoning and Shandong was high and gradually decreased from Zhejiang to the south. The mean biomass of the seaweed beds along the coast of China was 7.29 kg/m2, and the mean coverage was 41.25%. The height and fresh weight of the dominant species gradually decreased with the decreasing latitude. The seaweed beds were distributed from the shallow water zone to the profundal zone along the coast from north to south, and the bathymetry of seaweed beds in Hainan was below 6 m. Based on the water temperature, the attributes of the seaweed beds, the temperature attributes of the dominant species, and the seaweed’s distribution, the seaweed beds in China can be specifically divided into temperate warm water types, subtropical warm water types, and tropical warm water types. This study is relevant to the development of regulations and directives to ensure biodiversity conservation and environmental sustainability.

MtDNA &amp;lt;italic&amp;gt;COⅠ&amp;lt;/italic&amp;gt; sequence diversity of &amp;lt;italic&amp;gt;Gerres limbatus&amp;lt;/italic&amp;gt; in coastal waters of China

In order to contribute information on genetic background of <italic>Gerres limbatus</italic> in coastal waters of China, 652 bp mtDNA <italic>COⅠ</italic> sequences of 140 individuals from 9 geographic populations were analyzed. 14 mutation sites were found and 13 haplotypes were identified, of which 9 were unique haplotypes and 4 were shared haplotypes. The overall haplotype and nucleotide diversity were low ( <italic>H</italic>_d=0.276±0.050, π =0.000 5±0.000 1 ), of which genetic diversity of populations from the east part of the Qiongzhou Strait ( <italic>H</italic>_d = 0.338-0.456, π = 0.000 6-0.001 1 ) was higher than those in the western Beibu Gulf ( <italic>H</italic>_d =0-0.295, π =0-0.000 5 ). Haplotype network diagrams did not show obvious genealogical and geographic structure. Genetic differentiation coefficicent(<italic>F</italic>_st) showed that there was indistinctively low-middle genetic differentiation between Naozhou population and other populations ( <italic>F</italic>_st= 0.0773-0.1696). No obvious differentiation was found among other populations ( <italic>F</italic>_st=-0.041 5-0.061 2). AMOVA analysis also showed that 95% population variation originated from within the group. The negative overall value of the neutrality test (Tajima’s <italic>D</italic>=-2.254 9; Fu’s <italic>F</italic>_s=-16.472 5 ) and a significant single peak in the nucleotide mismatch distribution were consistent with demographic expansion in the past, and deduced expansion time ranged from about 0.130 4 to 0.043 5 million years ago. Since the overall genetic diversity of the population was less than 0.5 and nucleotide diversity was less than 0.005, it was speculated that <italic>Gerres limbatus</italic> population in coastal waters of China had recently encountered a severe bottleneck effect. The nucleotide diversity of the Ningde and Naozhou populations was relatively high and had a conservation priority. As genetic diversity of populations in the Beibu Gulf was extremely low, measures should be taken to avoid further decline in genetic diversity.

The parasitic dinoflagellate Hematodinium infects marine crustaceans.

Hematodinium is a type of parasitic dinoflagellate that infects marine crustaceans globally. The parasite lives mainly in the hemolymph or hemocoels of affected hosts, and results in mortalities due to malfunction or loss of functions of major organs. In recent years, the parasite had developed into an emerging epidemic pathogen not only affecting wild populations of economically valuable marine crustaceans in western countries but also the sustainable yield of aquaculture of major crabs in China. The epidemics of the parasitic diseases expanded recently in the coastal waters of China, and caused frequent outbreaks in aquaculture of major crab species, especially Portunus trituberculatus and Scylla paramamosain. In addition, the pathogen infected two species of co-cultured shrimps and multiple cohabitating wild crabs, implying it is a significant threat to the sustainable culture of commercially valuable marine crustaceans. In particular, the polyculture system that is widely used along the coast of China may facilitate the spread and transmission of the pathogen. Thus, to provide a better understanding of the biological and ecological characteristics of the parasitic dinoflagellate and highlight important directions for future research, we have reviewed the current knowledge on the taxonomy, life cycle, pathogenesis, transmission and epidemiology of Hematodinium spp. Moreover, ecological countermeasures have been proposed for the prevention and control of the emerging infectious disease.

Population genetic structure analysis of big head croaker (&amp;lt;italic&amp;gt;Collichthys lucidus&amp;lt;/italic&amp;gt;) based on mitochondrial cytochrome &amp;lt;italic&amp;gt;b&amp;lt;/italic&amp;gt; gene sequences

With the collapse of inshore fishery resources, small economic fishes have become the major fish resource in the coastal waters of China. As one of the most important fish resources, big head croaker (<italic>Collichthys lucidus</italic>) has a wide distribution and high production in Chinese estuaries and is included on the List of China State Key Protected Commercial Sources of Aquatic Animals and Plants. However, the population structure of <italic>C. lucidus</italic> is still unclear, and knowledge of this is essential for decision-makers to sustainably develop the fishery industry. In the present study, the population genetic structure of <italic>C. lucidus</italic> in the coastal waters of China was examined based on mitochondrial cytochrome <italic>b</italic> gene sequences. A total of 342 individuals were sampled from nine localities from September to November 2019, and 174 haplotypes were subsequently identified. The median-joining network and neighbor-joining tree of haplotypes show two significantly divergent clades, Clade N and Clade S, which correspond to the geographical North group and South group, respectively. Analyses of molecular variance (AMOVA) also revealed significant genetic differentiation between the North and South groups (<italic>P</italic>&lt;0.01). The genetic diversity results indicated that the haplotype diversity of the South group was higher than that of the North group (0.9418 <italic>vs.</italic> 0.8758); however, the results of nucleotide diversity showed the opposite outcome (0.0036 <italic>vs.</italic> 0.0041). Analyses of pairwise <italic>F</italic>_ST and <italic>N</italic>_m revealed significant genetic differentiation between the North and South group populations (<italic>P</italic>&lt;0.05), with little gene exchange (<italic>N</italic>_m=0.06). The results of mismatch distribution and neutrality tests show that population expansion occurred for big head croaker along the coast of China in the Pleistocene era, and the expansion times of the North and South groups were estimated to be 7990–19900 and 26310–65770 years ago, respectively. The divergence time of big head croaker between the North and South groups was estimated at 345000–862500 years ago based on genetic distances. Historical events, biological characteristics, and other extrinsic forces (i.e., coastal currents) may all be associated with the current phylogeographic pattern of big head croaker in the coastal areas of China. In conclusion, the population structure of big head croaker along the coastal waters of China consist of the North group and the South group, which should be exploited and managed individually in fisheries.

Whole-genome resequencing of Japanese whiting ( Sillago japonica) provide insights into local adaptations.

The genetic adaptations of various organisms to heterogeneous environments in the northwestern Pacific remain poorly understood. Heterogeneous genomic divergence among populations may reflect environmental selection. Advancing our understanding of the mechanisms by which organisms adapt to different temperatures in response to climate change and predicting the adaptive potential and ecological consequences of anthropogenic global warming are critical. We sequenced the whole genomes of Japanese whiting (Sillago japonica) specimens collected from different latitudinal locations along the coastal waters of China and Japan to detect possible thermal adaptations. Using population genomics, a total of 5.48 million single nucleotide polymorphisms (SNPs) from five populations revealed a complete genetic break between the Chinese and Japanese groups, which was attributed to both geographic distance and local adaptation. The shared natural selection genes between two isolated populations (i.e., Zhoushan and Ise Bay/Tokyo Bay) indicated possible parallel evolution at the genetic level induced by temperature. These genes also indicated that the process of temperature selection on isolated populations is repeatable. Moreover, we observed natural candidate genes related to membrane fluidity, possibly underlying adaptation to cold environmental stress. These findings advance our understanding of the genetic mechanisms underlying the rapid adaptations of fish species. Species distribution projection models suggested that the Chinese and Japanese groups may have different responses to future climate change, with the former expanding and the latter contracting. The findings of this study enhance our understanding of genetic differentiation and adaptation to changing environments.

Interannual variability of larval fish assemblages associated with water masses in winter in the Taiwan Strait during 2007\u20132013

In this study, the interannual variations of ichthyoplankton assemblages in the Taiwan Strait (TS) during the winters of 2007–2013 were determined. The cold China Coastal Current (CCC) and Mixed China Coastal Water (MCCW) intruded into the TS and impinged with the warm Kuroshio Branch Current (KBC) with annual variations. Consequently, the ichthyoplankton community in the TS was mainly structured into two assemblages characterized by differing environmental conditions. The composition of the warm KBC assemblage was relatively stable and was characterized by Diaphus B and Bregmaceros spp. By contrast, the cold MCCW assemblage demonstrated considerable variations over the years, with demersal Gobiidae and Scorpaenidae families considered the most representative. In addition, Benthosema pterotum and Trichiurus spp. were common in both KBC and MCCW assemblages. The distribution of the KBC assemblage demonstrated sharp boundaries in the frontal zones, whereas changes in the assemblage structure between the frontal zones were gradual for the MCCW assemblage, particularly when demersal taxa were dominant. Sea surface temperature and salinity were most strongly associated with variability in the assemblage structure during the study period. Thus, this paper provides a better understanding of long-term larval fish dynamics during winter in the TS.

China Ocean ReAnalysis (CORA) version 1.0 products and validation for 2009–18: 2009–18年西北太平洋区域海洋再分析CORA1.0产品研制及检验

China Ocean ReAnalysis (CORA) version 1.0 products for the period 2009–18 have been developed and validated. The model configuration and assimilation algorithm have both been updated compared to those of the 51-year (1958–2008) products. The assimilated observations include temperature and salinity field data, satellite remote sensing sea surface temperature, and merged sea surface height (SSH) anomaly data. The validation includes the following three aspects: (1) Temperature, salinity, and SSH anomaly root-mean-square errors (RMSEs) are computed as a primary evaluation of the reanalysis quality. The 0–2000 m domain-averaged RMSEs of temperature and salinity are 0.61°C and 0.08 psu, respectively. The SSH anomaly RMSE is less than 0.2 m in most regions. (2) The 35°N temperature section is used to evaluate the ability to reproduce the thermocline, mixing layer, and Yellow Sea cold water mass. In summer, the thermocline is reinforced, with the gradient changing from 3°C in May to 10°C in August. The mixing-layer depth reproduced by CORA is consistent with that computed from the observed climatology. The Yellow Sea cold water mass forms at a depth of 50 m. (3) The reanalysis current is examined against the tracks of some drifting buoys. The results show that the reanalysis current can capture the mesoscale eddies near the Kuroshio, which are similar to those described by the drifting buoys. Overall, the 2009–18 CORA reanalysis products are capable of reproducing major oceanic phenomena and processes in the coastal waters of China and adjacent seas.摘要在51年 (1958–2008) 西北太平洋区域海洋再分析CORA1.0产品的基础上, 改进了模式配置和同化方法, 研制了2009-18年的CORA产品并对其进行以下检验: (1) 温盐和海表高度异常均方根误差分布检验; (2) 35°N处温度断面分布检验; (3) 再分析流场和表漂浮标轨迹对比检验.结果显示, 2009–18年的CORA产品可以再现海洋要素长时间序列,时空多尺度的变化特征, 为研究特征海洋现象和过程提供背景信息.

Three redescriptions in Tintinnopsis (Protista: Ciliophora: Tintinnina) from coastal waters of China, with cytology and phylogenetic analyses based on ribosomal RNA genes

BackgroundThe taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated cytological and molecular information. Tintinnopsis, the most speciose tintinnine genus, is also the most problematic: it is known to be non-monophyletic, but it cannot be revised until more of its species are studied with modern methods.ResultsHere, T. hemispiralis Yin, 1956, T. kiaochowensis Yin, 1956, and T. uruguayensis Balech, 1948, from coastal waters of China, were studied. Lorica and cell features were morphometrically investigated in living and protargol-stained specimens, and sequences of three ribosomal RNA (rRNA) loci were phylogenetically analyzed. The three species show a complex ciliary pattern (with ventral, dorsal, and posterior kineties and right, left, and lateral ciliary fields), but differ in lorica morphology, details of the somatic ciliature and rRNA gene sequences. Tintinnopsis hemispiralis is further distinguished by a ciliary tuft (a ribbon of very long cilia originated from the middle portion of the ventral kinety and extending out of the lorica) and multiple macronuclear nodules. Both T. kiaochowensis and T. uruguayensis have two macronuclear nodules, but differ in the number of somatic kineties and the position of the posterior kinety. Two neotypes are fixed for T. hemispiralis and T. kiaochowensis to stabilize the species names objectively, mainly because of the previous unavailability of type materials. By phylogenetic analysis and comparison with closely-related species, we infer that the ciliary tuft and details such as the commencement of the rightmost kinety in the lateral ciliary field are synapomorphies that may help clarify the systematics of Tintinnopsis-like taxa.ConclusionThe redescriptions of three poorly known Tintinnopsis species, namely T. hemispiralis, T. kiaochowensis, and T. uruguayensis firstly revealed their ciliary patterns and rRNA sequences. This study expands knowledge and database of tintinnines and helps in identifying potential synapomorphies for future taxonomic rearrangements.

Karenia mikimotoi blooms in coastal waters of China from 1998 to 2017

Karenia mikimotoi is a typical ichthyotoxic dinoflagellate species that causes blooms around the world. In China, the first K. mikimotoi bloom was recorded around the Pearl River estuary in 1998. There were 137 K. mikimotoi bloom events recorded in the four seas around China from 1998 to 2017. In the northernmost and southernmost regions, K. mikimotoi blooms occurred off of Qinhuangdao city and Zhanjiang city, respectively, with latitudinal range of approximately 20°. K. mikimotoi blooms were recorded almost every month from spring to autumn except November; however, no blooms occurred in winter during this 20-year period. In China, the 1998–2002 period represented the initial and developmental stages of K. mikimotoi blooms, while the 2003–2017 period represented the burst stage. Although large spatial and temporal distributions have been, K. mikimotoi blooms are generally centered on the period from May–June and on the coasts of the East China Sea, where the blooms have been correlated with conditions including eutrophication, meteorology and climate change, and sediment.

Isotopic evidence for size-based dietary shifts in the jellyfish Cyanea nozakii in the northern East China Sea

Abstract Cyanea nozakii is a common bloom-forming Scyphomedusa in coastal waters of China. To understand the diet of this jellyfish and its trophic relationship with other zooplankton groups, stable isotope δ13C and δ15N values of C. nozakii in the bloom area within the northern East China Sea (ECS) in August 2017 were analyzed. We examined: first, the size-based variation in C. nozakii stable isotope values, second, the contributions of different food sources to the C. nozakii diet, and possible size-based dietary shifts in individual C. nozakii and, third, the contribution of gelatinous prey to the C. nozakii diet. Isotope values of differently sized C. nozakii ranged from −18.81 to −16.88‰ for δ13C and from 8.23 to 10.46‰ for δ15N. A significant change in δ15N values implies that the trophic position and the diet of C. nozakii changed as body size increased. The MixSIAR model indicated that C. nozakii underwent a dietary shift during growth, from a seston-dominant diet in smaller medusae to a zooplankton-dominant diet in larger medusae. Copepods were an important food source for C. nozakii, irrespective of size. The mean proportions of gelatinous zooplankton increased significantly in the C. nozakii diet with increasing C. nozakii diameter, suggesting that larger C. nozakii consumed more gelatinous prey. The diet of larger C. nozakii included 9.54% Nemopilema nomurai and 9.53% small medusae. The results suggest that intraguild predation among these jellyfish exist in the northern ECS.

Modeling the Impact of Marine DMS Emissions on Summertime Air Quality Over the Coastal East China Seas

[1] Biogenic emission of dimethyl sulfide (DMS) from seawater is the major natural source of sulfur into the atmosphere. In this study, we use an advanced air quality model (CMAQv5.2) with DMS chemistry to examine the impact of DMS emissions from seawater on summertime air quality over China. A national scale database of DMS concentration in seawater is established based on a five-year observational record in the East China seas including the Bohai Sea, the Yellow Sea and the East China Sea. We employ a commonly used global database and also the newly developed local database of oceanic DMS concentration, calculate DMS emissions using three different parameterization schemes, and perform five different model simulations for July, 2018. Results indicate that in large coastal areas of China, the average DMS emissions flux obtained with the local database is three times higher than that resulting from the global database, with a mean value of 9.1 μmol m-2 d-1 in the Bohai Sea, 8.4 μmol m-2 d-1 in the Yellow Sea and 13.4 μmol m-2 d-1 in the East China Sea. The total DMS emissions flux calculated with the Nightingale scheme is 42% higher than that obtained with the Liss and Merlivat scheme, but is 15% lower than that obtained with the Wanninkhof scheme. Among the three parameterizations, results of the Liss and Merlivat scheme agree better with the ship-based observations over China's coastal waters. DMS emissions with the Liss and Merlivat parametrization increase atmospheric sulfur dioxide (SO2) and sulfate (SO4 2-) concentration over the East China seas by 6.4% and 3.3%, respectively. Our results indicate that although the anthropogenic source is still the dominant contributor of atmospheric sulfur burden in China, biogenic DMS emissions source is nonnegligible.

Pleistocene isolation caused by sea-level fluctuations shaped genetic characterization of Pampus minor over a large-scale geographical distribution.

The southern lesser pomfret (Pampus minor) is an economically important fish, and its numbers are declining because of overfishing and environmental pollution. In addition, owing to the similarities of its external morphological characteristics to other species in the genus Pampus, it is often mistaken for grey pomfret (P. cinereus) or silver pomfret (P. argenteus) juveniles. In this study, the genetic diversity and structure of 264 P. minor individuals from 11 populations in China and Malaysia coastal waters were evaluated for the first time, to the best of our knowledge, using mitochondrial cytochrome b fragments. The results showed that P. minor had moderate haplotype diversity and low nucleotide diversity. Furthermore, two divergent lineages were detected within the populations, but the phylogenetic structure corresponded imperfectly with geographical location; thus, the populations may have diverged in different glacial refugia during the Pleistocene low sea levels. Analysis of molecular variation (AMOVA) showed that genetic variation originated primarily from individuals within the population. Pairwise FST results showed significant differentiation between the Chinese and Malaysian populations. Except for the Xiamen population, which was classified as a marginal population, the genetic differentiation among the other Chinese populations was not significant. During the Late Pleistocene, P. minor experienced a population expansion event starting from the South China Sea refugium that expanded outward, and derivative populations quickly occupied and adapted to the new habitat. The results of this study will provide genetic information for the scientific conservation and management of P. minor resources.

Short-term exposure to norfloxacin induces oxidative stress, neurotoxicity and microbiota alteration in juvenile large yellow croaker Pseudosciaena crocea

In recent years, antibiotics have been widely detected in coastal waters of China, which raising concerns for coastal biodiversity and aquaculture. This study evaluated the effects of short-term exposure of norfloxacin (NOR) on oxidative stress and intestinal health of the large yellow croaker Pseudosciaena crocea. Juvenile fish were exposed to four concentrations of NOR (0.1, 10, 100 and 1000 μg/L) for 14 days. The results showed that NOR inhibited growth and threatened the survival of juveniles. According to the changes of intestinal microbiota, we found that NOR led to a significant decrease in intestinal microbiota diversity, with the decreased relative abundance of Proteobacteria, but the increased Tenericutes. From the perspective of microbial function, NOR inhibited metabolism, cellular defence mechanism and information transduction process. In terms of biochemical indicators, NOR caused an increase in malondialdehyde (MDA) level and inhibited superoxide dismutase (SOD) and acetyl cholinesterase (AChE) activities. Catalase (CAT) activity was activated at low concentration but significantly inhibited at high concentration of NOR. Moreover, there was a high correlation between change in biochemical indicators and change in the microbial community. Overall, environmentally relevant concentrations (0.1 μg/L) and high concentrations (10, 100 and 1000 μg/L) of NOR have negative effects on the defence function and intestinal health of large yellow croaker juveniles.

Dissolved and Particulate Primary Production and Subsequent Bacterial C Consumption in the Southern East China Sea

Dissolved primary production (DPP), particulate primary production (PPP), and the subsequent bacterial production (BP) and respiration (BR) were reported for the first time in the NW Pacific. The study area of the subtropical southern East China Sea covers different water types, including oligotrophic Kuroshio and Taiwan Strait waters, as well as nutrient-rich China coastal and upwelled Kuroshio subsurface waters. On an areal basis, DPP and PPP ranged from 67-1649 and 160-1182 mgC m-2 d-1, respectively, showing high values in the upwelling area. The contribution of DPP to total primary production (percent extracellular release; PER) averaged 40.8+/-12.2%with >50% in the upwelling stations. The BP and BR ranged from 48-245 and 709-2822 mgC m-2 d-1, respectively, showing patterns similar to those of primary production. Bacterial growth efficiency (BGE) averaged 5.7+/-1.4%, representing in the lower end of the global ocean values. Phytoplankton and bacteria were well coupled in the upwelling area, whereas primary production could not sustain the bacterial carbon demand (BCD) at other stations. The slope of the log-log relationship between DPP and PPP was >1, indicating that the microbial loop may receive less organic carbon supply in the future warmer, less productive ocean.

Distributions of volatile halocarbons and impacts of ocean acidification on their production in coastal waters of China

The volatile halocarbons (VHCs) CH3I, C2HCl3, C2Cl4, and CH2Br2 were measured in the Changjiang Estuary and adjacent waters during autumn 2018. Results revealed that their concentrations in coastal waters were influenced by anthropogenic activities, biological release, and complex hydrographic features. The vertical distributions of VHCs were determined mostly by the mixing of water masses. By investigating the impacts of temperature, salinity, chlorophyll a, nutrients, and pH on the distributions of these trace gases we revealed that C2HCl3 and C2Cl4 were positively correlated with salinity and nutrient availability. The sea-to-air fluxes of CH3I, C2HCl3, C2Cl4, and CH2Br2 were estimated to be 27.62, 280.3, 221.73, and 142.41 nmol m−2 day−1, respectively, suggesting that the study area was a net source of these trace gases. The impact of elevated fCO2 on the production of the four volatile halocarbons was studied using mesocosms in Wu Yuan Bay, Xiamen. The results showed that elevated fCO2 had little impact on the VHCs. Positive relationships were observed between CH2Br2 and phytoplankton biomass when fCO2 was low, and between CH3I and phytoplankton biomass when fCO2 was high, suggesting that algal release was a significant source of both compounds.

Optical proxy for the abundance of red Noctiluca scintillans from bioluminescence flash kinetics in the Yellow Sea and Bohai Sea.

Red Noctiluca scintillans (RNS) red tides frequently occur in coastal waters in China, leading to great ecological and economic losses. The prewarning of red tides via the monitoring of RNS abundance in the field is of great importance. Bioluminescence sensors are convenient to deploy on multiple underwater platforms, and bioluminescence is related to the abundance and species of dinoflagellates. As an optical proxy, the maximum bioluminescence potential (MBP) could respond in a timely manner to changes in RNS abundance and be utilized to estimate it. A novel method with high correlation (R2=0.82) is proposed to estimate the RNS abundance from the MBP in this study. The maximum RNS abundance range of the method is 380 cell L-1. Furthermore, the bioluminescence flash kinetics of dinoflagellate individuals are analyzed to demonstrate the applicability of the method in the Yellow Sea and Bohai Sea.