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Volume 40 ， Issue 1 ， 2022
- Abstract：An eddy-resolving four-dimensional variational (adjoint) data assimilation and state estimate was constructed for the low- to mid-latitude Pacific, Indian Oceans, and South China Sea based on the framework of "Estimating the Circulation and Climate of the Oceans (ECCO)". It is named as the Two Oceans One Sea State Estimate (TOOSSE). It fits a model to a number of modern observations of 2015–2016, including the Argo float temperature and salinity, satellite altimetric sea surface anomalies, by adjusting initial temperature and salinity, sea surface boundary conditions, and background diapycnal diffusivities. In total, ~50% of the original model-data misfits have been eliminated, and the estimated state agreed well with a variety of independent observations at meso- to large scales, and on the intra-seasonal to interannual timescales. Mesoscale variability is systematically strengthened in TOOSSE and closer to observations than that without data assimilation, which is especially evidenced by the improved simulation of the mesoscale tropical instability waves (TIWs). Adjustments to ocean surface forcing parameters exhibit both large and frontal/mesoscale structures, and the magnitude reach 20%–100% of the first guesses; the adjustments to diapycnal diffusivity exhibit an obvious elevation (decrement) in (below) the thermocline in the equatorial band. The results indicate that TOOSSE represents a dynamically and thermodynamically consistent ocean state estimate of the 2015–2016 Indo-Pacific Ocean, and can be widely utilized for regional process studies.Keywords：Pacific Ocean;Indian Ocean;South China Sea;adjoint;four-dimensional variational data assimilation8|0|0Updated：2023-04-27
- Abstract：Northward inflow through the East Taiwan Channel is vital in modulation of water exchange processes off northeastern Taiwan, China. In addition to the effects of the Kuroshio Current and westward-propagating oceanic mesoscale eddies, the seas off eastern Taiwan, China, are frequently influenced by typhoons. Focusing on extrema of East Taiwan Channel volume transport (ETCVT) that appear within days of typhoon influence, this study investigated 124 historical cyclones including 91 typhoons that passed over the study sea area off eastern Taiwan, China. Based on 25-year HYbrid Coordinate Ocean Model (HYCOM) data, 71% of short-term (within 10 d) ETCVT absolute values with >5 Sv occurred under the influence of typhoons crossing the study sea area, and the maximum short-term ETCVT extrema induced by typhoons were 12.5 and -10.9 Sv. The ETCVT extrema induced by typhoons showed reasonable positive correlation with typhoon wind speed. More importantly, the ETCVT extrema differed in response to different typhoon tracks. Three types of typhoon were identified based on their track and impact on ETCVT. Representative typhoon cases were examined to elucidate the specifics of each typical response. Based on historical best track data and HYCOM data, it was established that Type I typhoons caused the ETCVT to exhibit a negative extremum followed by a positive extremum. All Type I, II, and III typhoons tended to result in typical ETCVT fluctuations in the surface mixing layer above the depth of 50–100 m, while Type II typhoons were more likely to induce ETCVT fluctuations in the subsurface layer. The findings of this study enhance understanding of ETCVT extrema that occur following typhoon passage, which is valuable for short-term physical-biogeochemical studies both in the study region and in areas downstream owing to the large net volume transport changes induced by typhoons.Keywords：ocean modeling;East Taiwan Channel;volume transport extrema;typhoon6|0|0Updated：2023-04-27
- Abstract：Temperature and salinity data, obtained by two snapshot surveys during 19–20 May 2019 and 12–25 September 2019 across the East China Sea (ECS) shelf, revealed that the Kuroshio intrusion to the north of 28°N comprised the Nearshore Kuroshio Branch Current (NKBC) and the Offshore Kuroshio Branch Current (OKBC) at the bottom of the ECS during spring 2019, and that the NKBC was weak during autumn 2019. The Regional Ocean Model System was used to reproduce the distribution of water masses and the current structure over the continental shelf of the ECS during 2019. Analyses of the momentum balances indicated that the cross-shore range and the intensity of the NKBC were determined by the combination of the geostrophic flow and bottom Ekman current. In comparison with that in May 2019, a weakened shoreward bottom Ekman current and an increased offshoreward geostrophic flow caused the disappearance of cross-shore range of the NKBC in September 2019. Meanwhile, a diminished northeastward alongshore geostrophic flow in September 2019 also weakened the intensity of the NKBC. Sensitivity experiments indicated that a strong southwestward wind can push the western (eastern) boundary of the NKBC further offshoreward (shoreward) by increasing (decreasing) the offshore geostrophic flow (bottom Ekman current). A weak Taiwan Warm Current (TWC) can move the eastern boundary of the NKBC shoreward by decreasing the onshore bottom Ekman current. A weak Kuroshio Current (KC) can move the eastern boundary of the NKBC shoreward by increasing the offshoreward geostrophic flow. Furthermore, a strong (weak) southwestward wind, weak (strong) TWC, and strong (weak) KC can diminish (enhance) the intensity of the NKBC. Of the three factors, the wind plays the major role in influencing the NKBC.Keywords：East China Sea;Nearshore Kuroshio Branch Current (NKBC);Regional Ocean Model System (ROMS);ocean modeling8|0|0Updated：2023-04-27
- Abstract：Data obtained from over 250 CTD stations in December 2006 and April 2007 were used to analyze the temperature and salinity structure of the water masses of the South Yellow Sea in spring. Six basic water masses were identified: the Southwest Yellow Sea Coastal Water Mass (SWYSCWM), Southwest Yellow Sea Local Water Mass (SWYSLWM), Qingdao Cold Water Mass (QDCWM), Yellow Sea Warm Current Water Mass (YSWCWM), Inchon Cold Water Mass (ICWM), and Subei Coastal Water Mass (SBCWM). The mechanisms of formation of these water masses are very different. The SWYSCWM is affected by continental water, whereas the SWYSLWM and SBCWM are local water masses that are less affected by other waters. The QDCWM derives from cold northern water. The YSWCWM exists from winter to spring. Because of the limited data coverage, the mechanism of formation of the ICWM remains unclear.Keywords：Yellow Sea;spring;water mass;formation6|0|0Updated：2023-04-27
- Abstract：The Lagrangian eddies in the western Pacific Ocean are identified and analysed based on Maps of Sea Level Anomaly (MSLA) data from 1998 to 2018. By calculating the Lagrangian eddy advected by the AVISO velocity field, we analyzed the variations in Lagrangian eddies and the average transport effects on different time scales. By introducing the Niño coefficient, the lag response of the Lagrangian eddy to El Niño is found. These data are helpful to further explore the role of mesoscale eddies in ocean energy transfer. Through normalized chlorophyll data, we observed chlorophyll aggregation and hole effects caused by Lagrangian eddies. These findings demonstrate the important role of Lagrangian eddies in material transport. The transportation volume of the Lagrangian eddy is calculated quantitatively, and several major transport routes have been identified, which helps us to more accurately and objectively estimate the transport capacity of Lagrangian eddies in the western Pacific Ocean.Keywords：Lagrangian coherent structure (LCS);mesoscale eddy;distribution character;material transport6|0|1Updated：2023-04-27
- Abstract：Deoxygenation has frequently appeared in coastal ecosystems over the past century due to the joint influence of increasing anthropogenically induced nutrient inputs and global warming. The semi-enclosed Bohai Sea is a typical system that is prone to deoxygenation, with regular hypoxia events consistently recorded in recent decades. Based on in-situ observation data collected in large-scale voyage surveys in the Bohai Sea during 2008–2017, the seasonal variability in dissolved oxygen (DO) and its controlling mechanisms were studied. The results indicated that in spring and autumn, the DO distributions exhibited similar spatial patterns in the surface and bottom layers, while in summer, its spatial distribution was characterized by large-scale oxygen-poor zones distributed off the Qinhuangdao Coast and the central southern Bohai Sea in the bottom layer. The controlling mechanisms of the DO distribution varied from season to season. Spring and autumn DO distributions were dominated by the seawater temperature. Under the combined effects of stratification and decomposition, the summer bottom DO exhibited dual-core distribution. On the one hand, stratification could greatly impede vertical mixing, resulting in reduced bottom DO replenishment. On the other hand, the increased bottom organic matter intensified the decomposition processes, inducing massive DO consumption and elevated dissolved inorganic nitrogen concentrations. In addition, the stronger stratification might be the reason for the more severe deoxygenation in the southern oxygen-poor zones in summer. Our study provides guidance for an in-depth understanding of the DO seasonality in the Bohai Sea and the mechanisms that modulate it and for the improvement of hypoxia forecasts in ocean models.Keywords：dissolved oxygen;seasonal variability;mechanism;the Bohai Sea6|0|5Updated：2023-04-27
Physics
- Abstract：Sea surface temperature (SST) in the Yellow Sea Warm Current (YSWC) pathway is sensitive to the East Asian Winter Monsoon (EAWM) and YSWC. However, the role of the YSWC in the evolution of regional SST remains unclear. Here, we present new U37k' based SST and grain size sequences spanning the last 6 092 years in the sediment core Z1, which was retrieved from the central Yellow Sea muddy area. Overall, U37k'-SST gradually increased since 6.1 ka BP, with a series of centennial-scale fluctuations. Its variation was mainly caused by EAWM when YSWC was weak between 6.1 and ~3.9 ka BP, as shown by the end-member content of grain size. However, after YSWC was fully developed, i.e., since ~3.9 ka BP, it exerted critical effects on SST evolution in its pathway. The 1 010, and 538-year cycles of the SST sequence indicated a basic control of solar activity on the oceanic conditions in the Yellow Sea. It is suggested that the variation of total solar irradiance was amplified by thermohaline circulation and then transmitted to the Yellow Sea through the EAWM. Meanwhile, the tropical Pacific signal of El Niño was transmitted to the YSWC through the Kuroshio Current. The dual properties of warm water transported by YSWC to compensate the EAWM and driving by Kuroshio Current closely linked the variation of SST in the YSWC pathway to the Northern Hemisphere high latitude climate and the tropical Pacific. These findings highlight the significance of YSWC on regional SST evolution and its teleconnection to high and low latitude forcing, which grains a better understanding of the long-term evolution of SST in the middle latitude Yellow Sea.Keywords：Yellow Sea Warm Current;U37k′-SST;East Asian Winter Monsoon;Kuroshio Current;high and low latitude forcing6|0|2Updated：2023-04-27
- Abstract：In-situ hydrothermal experiments using diamond-anvil cell show that sulfate and sulfide are the dominant sulfur species under P-T conditions similar to those of porphyry magmas. No sulfite was identified using in-situ Raman spectrometer. This supports that porphyry copper mineralization is controlled by sulfate reduction, rather than sulfite disproportionation.Keywords：diamond cell;sulfate;sulfide;porphyry deposits;magnetite crisis6|0|0Updated：2023-04-27
Geology
- Abstract：Dissolved organic matter (DOM) plays a vital role in promoting carbon and nutrient cycling. It is a food source for organisms and controls the migration and transformation of trace metals and other contaminants in aquatic systems. The contributions of aquatic DOM to the environment and ecology of a system are closely related to its abundance and chemical structure. In this study, the chemical composition and binding properties of DOM in a hypersaline lake watershed were investigated for the first time using dissolved organic carbon (DOC) analysis, absorption spectroscopy, Fourier transform infrared spectroscopy, pyrolysis-GC-MS (Py-GC-MS), and fluorescence parallel factor (PARAFAC) analysis combined with Pb(II) titration techniques. The results showed that DOM from the tributaries that flowed into the lake had a lower DOC content, higher molecular weight, and higher specific UV absorbance than the DOM in lake water. Protein-like fluorophores were mainly found in tributary and lake surface water DOM (LSDOM) and humic-like substances were abundant in lake groundwater DOM (LGDOM). Using this multi-methodological approach, we found that the DOM from the hypersaline lake watershed was mainly from microbial origins, and consisted of aromatics, carbohydrates, and aliphatics. The results from quantitative analysis showed that DOM from the inflowing tributaries contained more aromatics, lower carbohydrates, and lower aliphatics than DOM in the lake. Monocyclic aromatic hydrocarbons and carbohydrates were more abundant in LSDOM than LGDOM. The results from the Pb(II) titration technique coupled with PARAFAC analysis suggested that PARAFAC-derived components had relatively low condition stability constants (log KM<2). Of the two types of lake DOM, the LGDOM had a higher Pb(II) binding potential than the LSDOM. From this study we have improved our understanding of how DOM within a hypersaline lake watershed varies in its composition and potential to bind with metals.Keywords：dissolved organic matter;hypersaline lake watershed;composition;parallel factor analysis;Pb(II) titration6|0|2Updated：2023-04-27
- Abstract：Salt marshes are research hotspots of the carbon cycle in coastal zones because large amounts of atmospheric carbon dioxide is fixed by salt marshes vegetation and stored in its biomass and soil. Dissolved organic carbon (DOC) in submarine groundwater (well water and pore water) in salt marshes plays an important role in advective exchange between the salt marshes and coastal waters. However, the molecular characteristics of DOC in salt marsh groundwater are poorly understood because of the complex DOC structures and hydrodynamic process. In this study, fluorescent components and refractory DOC (RDOC) in submarine groundwater from a salt marsh (Chongming Island, China) and adjacent coastal water were characterized by fluorescence spectroscopy and nuclear magnetic resonance spectroscopy. The fluorescent components identified by parallel factor analysis indicated that humic-like substances dominated the chromophoric dissolved organic matter in the submarine groundwater. The chromophoric dissolved organic matter and dissolved organic matter in the submarine groundwater had non-conservative behaviors because of additions from terrestrial humic substances. The nuclear magnetic resonance spectra indicated that bioactive substances (carbohydrates) contributed only 13.2%–14.8% of the dissolved organic matter in the submarine groundwater but carboxyl-rich alicyclic molecules (CRAMs), the main components of RDOC, contributed 64.5% of the dissolved organic matter. Carbohydrates and CRAMs contributed 16.4% and 61.7% of the dissolved organic matter in the coastal water, similar to the contributions for submarine groundwater. The DOC concentration in submarine groundwater was 386±294 μmol/L, which was significantly higher than that in coastal water (91±19 μmol/L). The high DOC concentrations and>60% relative RDOC content suggested that submarine groundwater may be an important source of RDOC to coastal seawater. This information will be helpful for estimating the climate effects of salt marsh blue carbon.Keywords：submarine groundwater;dissolved organic carbon;fluorescence;refractory dissolved organic carbon;salt marsh;Chongming Island6|0|3Updated：2023-04-27
Chemistry
- Abstract：Aeration is an important measure to prevent cyanobacterial growth in eutrophic lakes and reservoirs. The purpose of this study is to clarify the influence of aeration induced turbulence on growth and competition of Microcystis and Scenedesmus in the presence of sediments with varying particle sizes. Microcystis aeruginosa and Scenedesmus obliquus were selected as the model organisms. Sediments with varying particle sizes were added into mono and mixed cultures of the organisms. In the absence of sediment, both low-, and high-intensity aerations (the turbulent dissipation rates were 1.60×10-6 and 1.16×10-5 m2/s3, respectively) promoted the growth of Scenedesmus, but the growth of Microcystis was inhibited particularly obvious under the high-intensity aeration conditions. In the presence of sediment, Scenedesmus was promoted under all aeration conditions, while Microcystis was inhibited. The inhibition rate of Microcystis decreased with the increase of sediment size when treated with low-intensity aeration in the nighttime. The highest inhibition rate of M. aeruginosa (89.2%) was identified under the condition of low-intensity aeration in the nighttime with small sediment addition. Furthermore, our results indicated that the impacts of sediment-induced light intensity reduction on algal growth were insignificant. In the mixed culture, the growth of Microcystis was inhibited by Scenedesmus in all treatments with aeration. Our results provided a theoretical basis for the practice in controlling cyanobacteria by aeration.Keywords：aeration induced turbulence;suspended sediment;phytoplankton community;cyanobacteria;Scenedesmus6|0|0Updated：2023-04-27
- Abstract：Blooms of Microcystis aeruginosa occur frequently in many freshwater ecosystems around the world, but the mechanism of recovery has not been fully understood. In our previous study, three benthic bacterial species (E.sp013, Ba.spD06, and Ba.spD24) were identified capable of promoting the recruitment of M. aeruginosa. Here, we further investigated the transcriptional response of M. aeruginosa to the benthic bacteria in early phase of recruitment by means of RNA-Seq analysis. In total, 5 803 803 unigenes on average length of 404 bp were obtained from the transcriptome of M. aeruginosa. There were 54 982 unigenes identified as benthic bacteria-responsive unigenes based on the expression level analysis. Results of the protein-protein interaction analysis (PPI) show that the hub genes of the benthic bacteria responsive unigenes mediated network were ribosomal proteins of 30S and 50S, and the most significant functional module of the network was related to the ribosome. Both the unigenes encoding the translation initiation factors (IF-2, IF-3) and elongation factors (lepA, fusA, and tufA) were up-regulated to respond benthic bacteria. Therefore, it indicates that the benthic bacteria have a positive influence on activating the ribosome during the early recovery stage of M. aeruginosa.Keywords：Microcystis aeruginosa;ribosome;benthic bacteria;chlorophyll a6|0|2Updated：2023-04-27
- Abstract：As an emerging pollutant, the presence of microplastics in marine organisms has been concerned increasingly. Shellfish, which are both economically and ecologically important, are of particular concern. In this study, we investigated the microplastic pollution in wild and farmed oysters (Crassostrea gigas) and clams (Ruditapes philippinarum) in the Jiaozhou Bay, China, for the first time. We found the microplastic pollution in shellfish in Jiaozhou Bay was at a moderate level. The abundance of microplastics in shellfish ranged from 0.16 to 12.09 items/g (wet weight, ww) or 1 to 9 items/ind. The average abundance of the ingested microplastics was 1.21 items/g (or 2.17 items/ind.) in all shellfish, 1.51 items/g (or 2.00 items/ind.) in clams and 0.92 items/g (or 2.34 items/ind.) in oysters. The abundance of microplastics in clams was significantly higher than that in oysters. Most microplastics (92.97%) were fibers, followed by fragments. The predominant color of the microplastics was black (42.97%), followed by blue, transparent, and red. Cellophane and polyethylene terephthalate (PET) dominated the microplastic composition. According to shellfish consumption, it can be inferred that the average microplastic consumption through Chinese diet is 1.27×103 items per capita per year.Keywords：microplastics;bivalves;Jiaozhou Bay;risk assessment8|0|0Updated：2023-04-27
- Abstract：The factors affecting lipid and fatty acid composition of copepod Calanus sinicus in the Yellow Sea (YS) and the East China Sea (ECS) were examined in this study. In spring, there were significant differences between these two regions for both environmental conditions and food availability. Such regional difference significantly influenced the lipid and fatty acid profiles of C. sinicus. Our results show that C. sinicus has a higher lipids content in ECS, especially for wax ester and triglyceride lipids, indicating a more active and efficient predation. According to BIO-ENV analysis, the variation of lipids profiles may be influenced majorly by water temperature. Moreover, the fatty acids (FAs) profiles of C. sinicus were also different between YS and ECS, especially in the four major contributors, C22:1ω11, eicosapentaenoic acid (EPA), docosahexenoic acid (DHA), and C20:1ω9. The considerable amounts of self-biosynthesized FAs of herbivorous copepod (C22:1ω11 and C20:1ω9) and low DHA/EPA ratio may indicate that C. sinicus in ECS feed mainly on phytoplankton comparing to those in YS. The fatty acid profiles of C. sinicus were affected by the differences in food availability.Keywords：Calanus sinicus;lipid storage;wax ester;fatty acid composition;Yellow Sea and East China Sea6|0|0Updated：2023-04-27
- Abstract：Estimating recovery times from pollution incident is an important issue of targeted biomonitoring programs. In the present study, the impact and recovery of macroinvertebrate communities from a cadmium wastewater discharge in the Longjiang River, Guangxi, China, in early January 2012 were studied based on 83 samples collected in five surveys within 20 months after the incident. The pollution affected seriously the local aquatic biota, and consequently, the invertebrate abundance and species richness were reduced considerably. Twelve months later, the taxonomic number of macroinvertebrates began to increase. However, sensitive taxa remained rare. Twenty months later, the taxon richness and abundance of macroinvertebrates increased significantly compared to those in the previous four time points. To explore the possible time-scale over which pre-disturbance conditions might occur, we chose four different typical metrics of taxa richness (total taxa number, cumulative taxa number, taxa number per samples, and the Shannon-Wiener diversity index) and extrapolated modeled recovery trajectories. Target values for the four metrics were set at average values for sites from the nearby Lijiang River, which were used as a reference. Assuming a continued linear trajectory, the recovery times were estimated to be 52, 39, 39, and 31 months, respectively, which was roughly 3–5 years. This is consistent with results from recovery times from other studies of acute pollution cases, but contrasted strongly to the much longer recovery times associated with chronic pollution from groundwater contamination and mine-tailing runoff.Keywords：macroinvertebrate community;recovery time;heavy metal pollution;cadmium;Longjiang River6|0|0Updated：2023-04-27
Ecology
- Abstract：Sargassum horneri is a foundational species and an important contributor to the floating seaweed stock along the northeastern coast of Asia. In this study, benthic and floating thalli of S. horneri were collected from Changdao Island (37°54'N, 120°43'E), Bohai Bay, China. We conducted an in-situ and an indoor experiment to study the acclimation potential in S. horneri to abiotic conditions at sea surface in autumn and winter. Both benthic and floating thalli were cultured in situ for two months (from October to December) at different depths: 0 m above sea level (masl) and 3 m below sea level (mbsl), and their growth rate, biochemical content, and photosynthetic performance were compared. During the first month of culture, the relative growth rate of floating thalli was 2-fold greater than that of benthic thalli at 0 masl. The photosynthetic rate of most thalli was significantly higher at 0 masl than at 3 mbsl. In the indoor experiments, floating and benthic thalli were exposed to high light intensity (400 μmol photons/(m2·s) photosynthetically active radiation (PAR)) for 21 d, and their photo-acclimation capacities were compared. Under high light intensity, the two types of thalli showed low maximum quantum yield (Fv/Fm) and light utilisation efficiency (α) but high light saturation point (Ek). Floating thalli showed higher photosynthetic rate and photoprotective ability than benthic thalli at high light intensity. The effective quantum yield of photosystem II [Y(II)] of both types of thalli recovered after a 6-day treatment with low light intensity (40 μmol photons/(m2·s)). These findings suggest that S. horneri is highly acclimated to the sea surface environment, which possibly contributes to its rapid accumulation and long free-floating periods at the sea surface.Keywords：chlorophyll-a fluorescence;growth;photosynthesis;photosynthetic pigments;Sargassum horneri6|0|1Updated：2023-04-27
- Abstract：PSI-driven cyclic electron flow (CEF-I) helps higher plants avoid severe heat damage. Gelidium amansii, a red seaweed used in the production of agar, inhabits subtidal rocks but can be found in the intertidal zone. The biological role of CEF-I is still unclear in this organism. Wild G. amansii was exposed to 30 ℃ heat stress for 12 h with continuous lighting. The results showed that treatment at 30 ℃ gradually decreased maximal PSII photochemical efficiency (Fv/Fm), linear electron transfer rate, and activity of photosynthetic reaction center. Both the maximal photochemical efficiency under light (Fv'/Fm') and maximum quantum yield of light-adapted PSII (ΦPSII) were maintained at a relatively stable level during the initial 6 h and then significantly decreased at 12 h. The up-regulated CEF-I helps to enhance proton gradient transfer across thylakoid membrane to protect oxygen-evolving complex against heat damage. Following the addition of a CEF-I inhibitor to plants, the Fv/Fm greatly decreased, suggesting that the CEF-I alleviates degree of photoinhibition caused by strong light. The results of measurement of antioxidant enzymes, including superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT), and the contents of H2O2 and malonaldehyde (MDA) provided additional evidence that CEF-I plays a protective role to a certain extent for G. amansii to manage stress at 30 ℃. Therefore, it can be concluded that CEF-I enables G. amansii to survive in intertidal zones by protecting it from the heat damage caused by high temperature stress.Keywords：cyclic electron flow;Gelidium amansii;heat stress;chlorophyll fluorescence;quantum yield;natural distribution6|0|0Updated：2023-04-27
Continued from the back cover
- Abstract：Although significant research efforts have been targeted toward conservation and management of endangered terrestrial flora and fauna, attempts have been limited to conserve threatened seaweeds. Silvetia siliquosa is an ecologically and commercially vital brown alga that is uniquely distributed in the Yellow-Bohai Sea and along the southwest coast of Korea. A massive decline in its distribution range and biomass from the mid-1990s onward indicates that this species has become endangered. In the present study, we used nuclear internal transcribed spacer and concatenated mitochondrial cytochrome oxidase I subunit+intergenic spacer to estimate the genetic diversity, population connectivity, and degree of genetic differentiation of S. siliquosa in China and Korea. The molecular results exhibited strikingly low levels of haplotype/ribotype and nucleotide diversity in S. siliquosa populations, with only three mitochondrial haplotypes and nuclear ribotypes detected in 136 and 143 specimens, respectively. The analysis of molecular variance revealed 85%–95% of genetic variance among populations. Population differentiation coefficient (FST) and gene flow (Nm) suggested that two populations (JIN and GWA) along the southern coast of Korea are highly divergent from the others, with weak genetic exchange. No significant genetic differentiation was observed among populations either in China or along the geographically proximate west coast of Korea. Thus, four independent management units were designated for sustainable management: the LII and RUS populations in China, the YEO and CHA populations along the west coast of Korea, and each of the GWA and JIN populations along the south coast of Korea. We suggest that artificial cultivation and transplantation of S. siliquosa are the effective approaches for restoration and conservation.Keywords：biodiversity conservation;endangered seaweed;genetic diversity;habitat loss;Silvetia siliquosa6|0|0Updated：2023-04-27
- Abstract：Strobilation is a well-organized metamorphosis process in scyphozoan jellyfish, through which the benthic polyp develops into the pelagic medusa. So far, knowledge on the molecular mechanisms behind the drastic morphological and physiological changes remains limited. In the present study, the metabolic profiles in polyp and strobila stages of jellyfish Rhopilema esculentum were examined using ultra-performance liquid chromatography coupled to a mass spectrometer. A total of 3 071 metabolites with putative annotation were detected, of which 167 were identified as differential metabolites between the polyp and strobila. Among the metabolites, 31 significantly decreased and 136 significantly increased in abundance in the strobila. Thyroxin, one of the previously proposed strobilation inducer of Aurelia, was not detected in this study. The indole-containing compounds are known for triggering strobilation in Discomedusae. Two indole derivatives and an indole-isomer containing metabolite were detected among the most significantly increased metabolites, which may be potential endogenous molecules for strobilation initiation. The membrane-associated phospholipids and the inflammation and oxidative stress-related eicosanoids were found to have significant changes. Although the functions of these metabolites in strobilation are not yet completely known, they provide some clues to the induction of the process of strobilation and metabolic responses that take place during strobilation.Keywords：Rhopilema esculentum;scyphozoan jellyfish;strobilation;metabolomics6|0|1Updated：2023-04-27
- Abstract：Seahorse embryos are brooded in the enclosed nutrient-rich environment of the male brood pouch, which may be prone to bacterial infection. The immune responses of interleukin (IL) genes in the brood pouch have not been well studied. We identified 13 interleukins in the lined seahorse Hippocampus erectus. Tissue-specific expression analysis revealed increased mRNA expression levels of il-1β, il-18, and il-8 in the brood pouch. When challenged with lipopolysaccharide or Vibrio parahaemolyticus, il-1β and il-18 were active as part of the acute and chronic inflammatory responses, respectively. Importantly, il-8 may be involved in powerful antibacterial immune responses and may be induced by il-1β and il-18 via a process involving the nuclear factor-κB signaling pathway. These results suggest that il-1β, il-18, and il-8 may play key roles in the antibacterial immune defense of the brood pouch in male seahorses.Keywords：lined seahorse;brood pouch;interleukin;antibacterial immunity6|0|1Updated：2023-04-27
- Abstract：The fermentation broth of Salinivibrio proteolyticus strain YCSC6 shows potent anti-parasitic activity against Uronema marinum, with activity varying in each fermentation stage. To investigate the biosynthetic mechanism of anti-parasitic compounds in strain YCSC6, a comprehensive analysis of metabolomics and transcriptomics over four different time points (12, 24, 48, and 72 h) was performed. Metabolomics detected 17 943 metabolites with 1 129 known metabolites. A trend analysis of the known metabolites showed that 575 metabolites, including 69 polyketides, were continuously enhanced, being the potential source of anti-parasitic agents. In addition, 941 genes mapped to the same pathways of these metabolites, were screened through the association analysis of metabolites and genes. KEGG pathway enrichment of these genes showed 270 genes mapped to the biosynthesis of secondary metabolites and 192 genes mapped to the biosynthesis of antibiotics. This demonstrates the potent secondary metabolic capacity of strain YCSC6. Finally, a gene-metabolite correlation network was created based on the 575 continuously enhanced metabolites and 43 continuously up-regulated genes. This revealed 13 genes at the key position that mapped to a putative metabolic pathway associated with the biosynthesis of polyketides and caprylic acid, which contributes to the potent anti-parasitic activity of strain YCSC6. This comprehensive analysis of metabolomics and transcriptomics provides insights into the biosynthetic mechanisms of anti-parasitic compounds in strain YCSC6 and guides the exploitation of more anti-parasitic agents for aquaculture.Keywords：metabolomics;transcriptomics;anti-parasitic;Salinivibrio proteolyticus;Uronema marinum6|0|0Updated：2023-04-27
- Abstract：Molluscan metabolomic analysis is essential for the understanding of the regulatory mechanism of aquatic invertebrate in response to hepatotoxic microcystins (MCs) stress. To understand the system responses of the gastropod to MC exposure, metabolomic alterations caused by two strains (MC-producing and non MC-producing) of Microcystis aeruginosa were characterized indifferent biological matrices (hepatopancreas and muscle) of Bellamya aeruginosa (Gastropoda) using 1H nuclear magnetic resonance (NMR) spectroscopy combined with MCs detections after exposure for 1, 7, and 14 d. Although ELISA analysis showed that no MCs was detected in both tissues after non MC-producing M. aeruginosa exposure, MCs concentrations were increasing in the hepatopancreas (from 1.29±0.48 μg/g to 3.17±0.11 μg/g) and foot muscle (from 0.07±0.02 μg/g to 0.21±0.08 μg/g) after 14-d exposure of MC-producing M. aeruginosa. Meanwhile, we observed that MC induced significant increase in creatine, a variety of amino acids (leucine, isoleucine, valine, threonine, alanine, methionine, glutamate, aspartate, and lysine), carboxylic acids (lactate, acetate, and D-3-hydroxybutyrate), and choline and its derivatives (phosphocholine and glycerophosphocholine) but decreased the energy substance (lipids, glucose, and glycogen) in the hepatopancreas. However, no significant metabolite differences were observed in the muscle between MC-producing and non MC-producing cyanobacteria treated groups. These results suggest that MC exposure may cause hepatic energy expenditure accompanied with various metabolic disorders that involve lipid metabolism, protein catabolism, osmoregulation, glycolysis, glycogenolysis, and tricarboxylic acid (TCA) cycle. Moreover, metabolic perturbation was aggravated as the level of accumulated MCs raised over time in the MC-producing cyanobacteria treatment. These findings indicated that MCs accumulation might lead to oxidative-stress-mediated damage of mitochondria functions.Keywords：Bellamya aeruginosa;Microcystis aeruginosa;metabolomic;nuclear magnetic resonance;microcystin6|0|0Updated：2023-04-27
- Abstract：Pyropia yezoensis is one of the most economical seaweed species in China. Determining how to make full use of mature P. yezoensis and exploring new ways to increase the value of its resources are important subjects of research for the development of the laver breeding industry. In this study, we provide a simple method to comprehensively extract the bioactive substances from P. yezoensis. The characteristics, functional properties, and antioxidant activities of two types of biopolymer extract from P. yezoensis were studied and analyzed relatively. Based on the characterization of water-soluble concentrate (WSC) and alkali-soluble concentrate (ASC), obtained via chemical analysis, including Fourier Transform Infrared Spectrometer (FT-IR) and Thermal Gravimetric Analyzer (TGA), and differential scanning calorimetry (DSC), they both had typical polysaccharide and protein characteristics and steady composition. ASC showed higher nitrogen solubility, water holding capacity, and foaming ability. ASC could not only be used as a protein supplement, but also performed well in improving the properties of foods in terms of water holding and fat-absorption. The emulsifying activity and oil-holding capacity of WSC were observed to be higher than those of ASC. Thus, WSC has the potential to be used as an emulsifier. Surprisingly, WSC and ASC have radical scavenging capacity in vitro, which broadens the direction of their application.Keywords：Pyropia yezoensis;water-soluble concentrate;alkali-soluble concentrate;chemical composition;functional properties6|0|0Updated：2023-04-27
- Abstract：To improve the solubility and bioactivity of chitosan, a new class of carboxymethyl chitosan derivatives possessing sulfonium salts was successfully designed and synthesized, including Methyl sulfide carboxymethyl chitosan (MCMCS), Ethyl sulfide carboxymethyl chitosan (ECMCS), Propyl sulfide carboxymethyl chitosan (PCMCS), and Butyl sulfide carboxymethyl chitosan (BCMCS). To determine the structure of the new class of the derivatives, methods of the Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance spectrometer (1H NMR), and 13C nuclear magnetic resonance spectrometer (13C NMR) were used. Moreover, the antioxidant activity of the derivatives for three types of free radicals, i.e., hydroxyl radical, superoxide radical, and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical was evaluated in vitro. In addition, the L929 cells were adopted to test the cytotoxicity of chitosan and its derivatives by CCK-8 assay. The class of the carboxymethyl chitosan derivatives showed a strong scavenging ability against the three free radicals at 1.6 mg/mL, with scavenging rate of over 70% and some up to 100%. At this high rate, the overall cell viability in the toxicity test reached more than 80%, indicating that the synthetic derivative had a little cytotoxicity. The results show that the introduction of carboxymethyl group to chitosan increased the water-solubility of chitosan, and the combination of sulfonate ions with different chain lengths further enhanced the antioxidant activity of chitosan. Therefore, the sulfonium-containing carboxymethyl chitosan derivatives had excellent bioactivity with good application prospects in food, biomedicine, and medical fields.Keywords：antioxidant activity;carboxymethyl chitosan derivative;sulfonium salts;structural characteristics/synthesis6|0|0Updated：2023-04-27
- Abstract：Five new records of the family Xanthidae are reported from China: Hypocolpus haanii Rathbun, 1909, Neoliomera variolosa (A. Milne-Edwards, 1873), Leptodius australis Ward, 1936, L. davaoensis Ward, 1941, and Xanthias joanneae Mendoza, 2013. The specimens were collected from Hainan Island and deposited in the Marine Biological Museum, Chinese Academy of Sciences. Diagnosis based on observation, photographs, line drawings, and some taxonomic discussions are provided.Keywords：morphology;Xanthidae;new records;South China Sea;taxonomy6|0|1Updated：2023-04-27
- Abstract：The polychaete species of Capitella are widely distributed in the China seas, however little is known about Capitella taxonomy, and specimens collected from China have been identified as Capitella capitata (Fabricius, 1780) for more than 50 years. C. capitata was considered to be Arctic and subarctic in distribution, therefore the records of C. capitata in the China seas probably represent other species. A taxonomic study based on the samples collected from the northeast coastal water of Shandong Province reveals a different species, Capitella teleta Blake et al., 2009, which is recorded in the China seas for the first time. Morphologically, C. teleta can be easily distinguished from C. capitata by the absence of neuropodial capillaries on chaetigers 8 and 9. The identity of C. teleta is further supported by genetic distance and phylogenetic analyses assessed from mitochondrial cytochrome c oxidase subunit I (COI) gene. In addition, the regeneration feature of C. teleta was studied through whole mount immunohistochemistry and chemical staining. After amputation, the wound of C. teleta was healed within 24 h, forming a significant regeneration blastema by 3 days post amputation (dpa). By 5 dpa, muscle tissues regenerated, nerve fibers also extended. By 7 dpa, neurites and muscle tissues are both significantly regenerated. Notably, there are more than ten segments regenerated until 16 dpa. As a highly opportunistic species, Capitella teleta is distributed in China, Japan, Korea, North America, and the Mediterranean. It is expected to be an excellent model for studying developmental genetics and evolution of regeneration.Keywords：Annelid;Capitella teleta;regeneration;Chinese waters6|0|1Updated：2023-04-27
Biology
- Abstract：Metalloproteases represent a class of extracellular proteases found in Vibrio anguillarum that can generate toxic and pathogenic effects in turbot (Scophthalmus maximus). The toxicological effect partly results from oxidative damage due to the production of excessive reactive oxygen species (ROS). Catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) are major antioxidant enzymes induced by various oxidative stresses and can scavenge peroxides generated in cells. To evaluate the effects of metalloprotease-induced ROS on the antioxidation defense mechanism of S. maximus head kidney cells, the cDNA of CAT gene (designated as SmCAT) was cloned and characterized. SmCAT comprises a 1 584-bp coding sequence that encodes a protein containing 527 amino acids with a poly(A) tail. Bioinformatics analysis revealed an active site signature sequence, a heme-ligand signature sequence, and three catalytic amino acid residues. The deduced SmCAT amino acid sequence shares a sequence similarity of 66.1%–92.4% with those of other species. Phylogenetic analysis revealed that SmCAT is classified with CAT of other fishes. Quantitative real-time PCR analysis showed that SmCAT was extensively expressed in all tested tissues, especially in blood. The expression of SmCAT, SmMnSOD, and SmGPx were inhibited significantly in head kidney cells treated with metalloprotease from 12 to 24 h. In 6 to 24 h metalloprotease-treated groups compared to that of the untreated group, it was found that the production of ROS was markedly increased, and the mitochondrial membrane potential was decreased considerably. Hoechst 33342 staining revealed the presence of apoptotic bodies when the cells were incubated with 8.0 or 40.0 μg/mL metalloprotease for 12 and 24 h. Hence, the toxic effects of metalloprotease are associated with the down-regulation of antioxidant enzyme expression and increased ROS levels, which trigger the activation of apoptosis in the head kidney cells of turbot. Our findings provide a better understanding on the mechanism of metalloprotease-induced apoptosis in fish.Keywords：gene cloning;expression;reactive oxygen species;metalloprotease;head kidney cells6|0|1Updated：2023-04-27
- Abstract：Although the immunomodulatory activity of bamboo vinegar and charcoal powder (BVC) has been increasingly documented in domestic animals, the use of BVC as immunostimulant in fish aquaculture awaits verification. In the present study, the immunostimulatory impacts of dietary BVC intake were investigated in an important aquaculture fish species, the African catfish Clarias gariepinus. Results show that the pathogen resistance of African catfish was significantly improved by dietary BVC intake at the tested levels (0.5%–2%), as indicated by higher survival rates (approximately 1.52–1.85 times that without BVC supplementation) upon intraperitoneally injection of bacterial pathogen Aeromonas hydrophila. In addition, both the count and phagocytic activity of blood cells were significantly up-regulated by a 45-day dietary supplementation of BVC. Moreover, compared to that of the control, fish individuals fed BVC containing diets exhibited significant higher activities of superoxide dismutase (SOD), myeloperoxidase (MPO), and lysozyme (LYZ). The content of immunoglobulin M (IgM) in serum of African catfish was also induced by dietary BVC supplementation. Furthermore, the expression levels of interleukin-8 (IL-8), toll-like receptor 1 and 5 (TLR1 and TLR5), myeloid differentiation factor 88 (MyD88), and nuclear factor kappa B (NFκB) in the head kidney were significantly up-regulated. Our findings indicate BVC could be an effective immunostimulant in teleost species, which may enhance fish immunity through improving hematic parameters, activating bioactive humoral molecules, and up-regulating immune related molecular pathways.Keywords：bamboo vinegar and charcoal powder (BVC);African catfish;immunostimulant;pathogen resistance6|0|0Updated：2023-04-27
- Abstract：Macrobrachium nipponense is an economically important freshwater prawn that is often threatened by many aquatic pathogens. In this study, comparative transcriptomic analysis was firstly used to explore the transcriptional response of M. nipponense to Aeromonas veronii or Staphylococcus aureus stimulation. A total of 400.19 million clean reads were obtained and assembled into 56 944 unigenes with an average length of 1 253 bp. A total of 1 857 differentially expressed genes were found after A. veronii infection, including 677 genes that were up-regulated and 1 180 genes that were down-regulated, while 1 061 significant differentially expressed genes were identified after S. aureus infection, including 390 up-regulated and 671 down-regulated genes. Many immune-related genes including Spaetzle, prophenoloxidase activating factor, C-type lectin, anti-lipopolysaccharide factor, and inhibitor of apoptosis 2 protein were commonly up-regulated after A. veronii or S. aureus infection. This study will enrich our understanding of the immune response to gram-positive and gram-negative bacteria infection in crustaceans.Keywords：Macrobrachium nipponense;differentially expressed genes;Aeromonas veronii;Staphylococcus aureus;immune response7|0|1Updated：2023-04-27
- Abstract：Sea cucumbers play an important role in sediment bioturbation in coral reef and rocky intertidal ecosystems, and bacteria were a commonly-reported component of holothuroid diets. Bacterial community composition in the foregut and hindgut of two common tropical sea cucumbers (Holothuria atra and H. leucospilota) and the ambient surface sediment were investigated using high throughput sequencing based on 16S rRNA gene analysis. A total of 5 584 operational taxonomic units (OTUs) were obtained from 25 samples based on a 97% threshold, and more than half of the OTUs (n=3 694, 66.2%) were shared by the gut contents of two species of sea cucumbers and surrounding sediments. Bacterial richness and diversity in sediment samples were significantly higher than those in the gut content samples (P < 0.05). Proteobacteria was the predominant phylum in most samples showing 45.69%±8.61%, 70.09%±4.03%, 45.88%±5.38%, and 55.19%±0.79% reads in the foregut of H. leucospilota, hindgut of H. leucospilota, hindgut of H. atra, and sediment libraries, respectively, but Bacteroidetes was the predominant phylum with the relative content of 34.98%±5.52% in the foregut of H. atra. Among the dominant genera, reads related to the genera Anderseniella, Ilumatobacter, and Ruegeria were detected in all the gut contents and sediment libraries. A comparison of gut bacteria community between the two species of sea cucumbers suggested that H. atra had stronger feeding preference than H. leucospilota, and the same types of microbes escaped digestion of the two sea cucumber species. Obvious different bacterial community composition in the foreguts of the two species of sea cucumbers and the surrounding sediments might result from the animal's selective feeding for sediment patches. Bacterial community structure in hindgut contents of H. atra and H. leucospilota both differed clearly from adjacent sediments, which indicated feeding activity of deposit-feeding sea cucumbers could change the sedimental bacterial composition. In conclusion, from the perspective of bacteria, sea cucumber H. atra and H. leucospilota had different feeding preferences, yet they could both affect bacterial composition in sediments by feeding activity. The motivation for selective feeding and sea cucumber-sediment interaction might be explored in the future.Keywords：sea cucumber;bacteria;gut;high-throughput sequencing;sediment6|0|2Updated：2023-04-27
- Abstract：Identifying the main factors on spatial differences in net growth rate of Yesso scallop (Patinopecten yessoensis) in culture system is the key to effective aquaculture management and development. Coupling a 3D ecosystem model (ROMS-CoSiNE) with a dynamic energy budget model for scallops, a Yesso scallop culture ecosystem (YeSCE) model was established with which scallop growth was simulated with real seeding density and juvenile size from local aquaculture experiments from December 1, 2012 to November 30, 2013. Results show that the YeSCE model has reasonably simulated the environmental variation and scallop net growth rate in the Changhai sea area. The growth of scallops was slow in winter and midsummer and was limited mainly by temperature. Food availability was a key factor that contributed to the fast growth of the scallops during spring to early summer and in autumn. Generally, the scallops cultured in the north part of the Changhai sea area grew faster than those in the south; and the net growth rate for scallops cultured near the island was significantly higher compare to the others, which is probably correlated to the spatial distribution of food availability. Based on the correlation analysis, the spatial differences of the net growth rate were largely affected by the length of the match timing of temperatures and food availability. The results of this study provide a scientific support for optimizing bottom culture planning and adjusting bottom culture methods.Keywords：3D ecosystem model;shellfish aquaculture;Yesso scallop;Patinopecten yessoensis;net growth rate;Changhai sea area6|0|1Updated：2023-04-27
Aquaculture and Fisheries
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