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Volume 41 ， Issue 5 ， 2023
- Abstract：Rising sea level is of great significance to coastal societies; predicting sea level extent in coastal regions is critical. When carrying out predictions, the subsequences obtained using decomposition methods may exhibit a certain regularity and therefore can provide multidimensional information that can be used to improve prediction models. Traditional decomposition methods such as seasonal and trend decomposition using Loess (STL) focus mostly on the fluctuating trend of time series and ignore its impact on prediction. Methods in the signal decomposition domain, such as variational mode decomposition (VMD), have no physical significance. In response to the above problems, a new decomposition method for sea level anomaly time series prediction (DMSLAP) is proposed. With this method, the trend term in a time series can be isolated and the effects of abnormal sea level change behaviors can be attenuated. We decompose multiperiod characteristics using this method while maintaining the smoothness of the analyzed series. Satellite altimetry data from 1993 to 2020 are used in experiments conducted in the study area. The results are then compared with predictions obtained using existing decomposition methods such as the STL and VMD methods and time varying filtering based on empirical mode decomposition (TVF-EMD). The performance of DMSLAP combined with a prediction method resulted in optimal sea level anomaly (SLA) predictions, with a minimum root mean square error (RMSE) of 1.40 cm and a maximum determination coefficient (R2) of 0.93 during 2020. The DMSLAP method was more accurate when predicting 1-year data and 3-year data. The TVF-EMD and DMSLAP methods had comparable accuracies, and the periodic term decomposed by the DMSLAP method was more in line with the actual law than that derived using the TVF-EMD method. Thus, DMSLAP can decompose SLA time series better than existing methods and is an effective tool for obtaining short-term SLA prediction.Keywords：time series decomposition;satellite altimetry;China Sea and its vicinity;sea level change19|0|0Updated：2024-10-14
- Abstract：Relationship between sea level change and a single climate indicator has been widely discussed. However, few studies focused on the relationship between monthly mean sea level (MMSL) and several key impact factors, including CO2 concentration, sea ice area, and sunspots, on various time scales. In addition, research on the independent relationship between climate factors and sea level on various time scales is lacking, especially when the dependence of climate factors on Niño 3.4 is excluded. Based on this, we use wavelet coherence (WC) and partial wavelet coherence (PWC) to establish a relationship between MMSL and its influencing factors. The WC results show that the influence of climate indices on MMSL has strong regional characteristics. The significant correlation between Southern Hemisphere sea ice area and MMSL is opposite to that between Northern Hemisphere sea ice area and MMSL. The PWC results show that after removing the influence of Niño 3.4, the significant coherent regions of the Pacific Decadal Oscillation (PDO), Dipole Mode Index (DMI), Atlantic Multidecadal Oscillation (AMO), and Southern Oscillation Index (SOI) decrease to varying degrees on different time scales in different regions, demonstrating the influence of Niño 3.4. Our work emphasizes the interrelationship and independent relationship between MMSL and its influencing factors on various time scales and the use of PWC and WC to describe this relationship. The study has an important reference significance for selecting the best predictors of sea level change or climate systems.Keywords：wavelet coherence;partial wavelet coherence;monthly mean sea level;influencing factors;time scale;significant correlation13|0|0Updated：2024-10-14
- Abstract：Ocean salinity is an important variable that affects the ocean stratification. We compared the salinity and ocean stratification in the tropical Pacific derived from the Argo (Array for Real-time Geostrophic Oceanography data), EN4 (Ensemble 4 analysis), SODA (the Simple Ocean Data Assimilation reanalysis), IAP (Institute of Atmospheric Physics data), and ORAS4 (Ocean Reanalysis System 4) over 2005–2017. Results show that the spatial distribution of climatological mean of sea surface salinity (SSS) in all the products is consistent, and the low salinity region showed large deviation and strong dispersion. The Argo has the smallest RMSE and the highest correlation with the ensemble mean, while the IAP shows a high-salinity deviations relative to other datasets. All the products show high positive correlations between the sea surface density (SSD) and SSS with respect to the deviations of climatological mean from ensemble mean, suggesting that the SSD deviation may be mainly influenced by the SSS deviation. In the aspect of the ocean stratification, the mixed layer depth (MLD) climatological mean in the Argo shows the highest correlation with the ensemble mean, followed by EN4, IAP, ORAS4, and SODA. The Argo and EN4 show thicker barrier layer (BL) relative to the ensemble mean while the SODA displays the largest negative deviation in the tropical western Pacific. Furthermore, the EN4, ORAS4, and IAP underestimate the stability in the upper ocean at the depths of 20–140 m, while Argo overestimates ocean stability. The salinity fronts in the western-central equatorial Pacific from Argo, EN4, and ORAS4 are consistent, while those from SODA and IAP show large deviations with a westward position in amplitude of 0°–6° and 0°–10°, respectively. The SSS trend patterns from all the products are consistent in having ensemble mean with high spatial correlations of 0.95–0.97.Keywords：salinity;ocean stratification;upper ocean;tropical Pacific;data products12|0|0Updated：2024-10-14
- Abstract：Mooring arrays have been widely deployed in sustained ocean observation in high resolution to measure finer dynamic features of marine phenomena. However, the irregular posture changes and nonlinear response of moorings under the effect of ocean currents face huge challenges for the deployment of mooring arrays, which may cause the deviations of measurements and yield a vacuum of observation in the upper ocean. We developed a data-driven mooring simulation model based on LSTM (long short-term memory) neural network, coupling the ocean current with position data from moorings to predict the motion of moorings, including single-step output prediction and multi-step prediction. Based on the predictive information, the formation of the mooring array can be adjusted to improve the accuracy and integrity of measurements. Moreover, we proposed the cuckoo search (CS) optimization algorithm to tune the parameters of LSTM, which improves the robustness and generalization of the model. We utilize the datasets observed from moorings anchored in the Kuroshio Extension region to train and validate the simulation model. The experimental results demonstrate that the model can remarkably improve prediction accuracy and yield stable performance. Moreover, compared with other optimization algorithms, CS is more efficient and performs better in simulating the motion of moorings.Keywords：mooring;motion simulation;long short-term memory (LSTM);optimization strategy;hybrid deep learning10|0|1Updated：2024-10-14
- Abstract：Accurate measurements of upwelling irradiance just beneath the ocean surface, Eu(λ, 0-), can be used to calculate ocean optical parameters, and further develop retrieval algorithms for remotely sensing water component concentrations. Due to the effects of sea surface waves, perturbation from instrument platform (ship), and instrument self-shading, Eu(λ,0-) is often difficult to be accurately measured. This study presents a procedure for extrapolating the Eu(λ, 0-) from the in-water radiometric profile measurements. Using the optical profile data from 13 bands (ranging from 381 to 779 nm) measured by 45 casts in the Ligurian Sea during 2003–2009, the Eu(λ,0-) was extrapolated from in-water upwelling irradiance measurements between the initial shallow depth, Z0, and an optimal bottom depth, Z1, by three linear models (linear, 2-degree polynomial, and exponential) and two nonlinear models (LOESS and spline). The accumulated errors of extrapolated Eu(λ, 0-) at each wavelength for the five models were calculated. It was found that the optimal Z1 depth for the linear and exponential models was at the depth of 80% of Eu(λ, Z0), 50% of Eu(λ, Z0) for the 2-degree polynomial model, 40% of Eu(λ, Z0) for the LOESS model, and 15% of Eu(λ, Z0) for the spline model. The extrapolated Eu(λ,0-) derived from the five models was in good agreement with the calculated true Eu(λ,0-). In all bands, the 2-degree polynomial model achieved the highest accuracy, followed by the LOESS model. In the short band of 381–559 nm, the linear and exponential models had the third-best performance, and the spline model performed worst within this range. For the red band of 619–779 nm, the accuracies of the exponential and spline models had the third highest performance, and the linear model produced lowest accuracy. Hence, the 2-degree polynomial model was an optimal procedure for extrapolation of Eu(λ, 0-) from the in-water radiometric profile measurements.Keywords：extrapolation;upwelling irradiance;ocean;in-water;accuracy14|0|0Updated：2024-10-14
Physics
- Abstract：Six outcrop sections in Fenghe River, Northwestern China, were sampled and analyzed. This study aims to determine provenance, tectonic setting, and source-area paleoweathering of the sediments of Fenghe River in combination of lithofacies analysis and bulk-rock geochemical data. The lithofacies in the studied area were classified as gravel, sand, and fine-grained clastic lithofacies, reflecting generally channel fill deposits, channel bar deposits, and over-bank deposits, respectively. The Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), and Chemical Index of Weathering (CIW) values ranged 50.10–62.29, 50.13–66.35, 56.52–71.12, respectively, together with element ratios such as Rb/Sr, K/Na, Rb/K, Th/K, Rb/Ti, and Cs/Ti indicate that the source area was under a low to moderate chemical weathering condition probably in cold and semi-arid climates. Moreover, plot of SiO2 vs. (Al2O3+K2O+Na2O) suggests that the sediments were deposited in a semi-arid climate. Plots of Cr/Th vs. Th/Sc, TiO2 vs. Zr, La/Yb vs. rare earth element (REE), and La-Th-Sc ternary diagrams, along with the lithology, indicate that the sediments in Fenghe River were mainly originated from felsic igneous rocks. Major elements-based discrimination diagrams and Th-Sc-Zr/10 and La-Th-Sc ternary diagram of the samples indicates that the source rocks of Fenghe River developed in a composite active continental margin and continental island arc field.Keywords：geochemistry;lithofacies;sediments;provenance;paleoweathering;Fenghe River12|0|0Updated：2024-10-14
- Abstract：Rare earth elements (REEs) can be used to trace source materials and identify their provenances, because of significant conservation and immobility during chemical alteration processes after erosion of materials from the provenance. This study focused on the temporal variation of REEs for columnar sediments from the mouth of Jiaozhou Bay in North China to understand the potential controls for the geochemical variations of sediments. Through extraction experiments, we identified that the residual fraction is the main host for REEs compared with other fractions (i.e., exchangeable and carbonate fraction, easily reducible oxides fraction, reducible oxides fraction, magnetite fraction). REE ratios (e.g., LaN/SmN and LaN/YbN; N: normalized by chondrite) lack correlations with grain size or the chemical index of alteration (CIA), which is correlated with major elements. All these indicate that these REE variations reflect the varying contribution of source materials from different provenances instead of grain size or chemical weathering effects. REE ratios (e.g., LaN/SmN and LaN/YbN) remain relatively constant until the depth of roughly 40 cm (equivalent to the year 1995), and show obvious changes beyond this depth. Compared REE characteristics of Jiaozhou Bay with those of neighboring rivers and bedrocks, the relative contributions of Dagu River-Jiaolai River, and Licun River may have been increased during the sedimentary processes, which could be caused by the construction of reservoir and related change of aquaculture (e.g., rapid accumulation of organic materials).Keywords：Jiaozhou Bay;sediments;rare earth elements (REEs);sequential extraction;provenance12|0|0Updated：2024-10-14
- Abstract：Clay mineral composition represents an important tracer of sediment source area, migration processes, and paleoclimatic conditions. Clay mineral analysis was performed on 15 surface sediment samples collected from the coast of Chanthaburi, Thailand. Results show that the composition of clay minerals in the study area differs substantially from that in surrounding regions of the Gulf of Thailand. The clay minerals of the Chanthaburi coast are dominated by kaolinite (~56%), followed by smectite (~21%), illite (~14%), and low concentrations of chlorite (~8%). The average illite chemistry index and crystallinity are 0.93 and 0.32, respectively. Comparative analysis of the clay mineral composition of surface sediments in several typical areas around the Gulf of Thailand indicated that the clays of the Chanthaburi coast are mainly derived from parent rock weathering in the small watersheds of the Chanthaburi and Welu rivers and the surrounding islands. Terrestrial input from the northern coast of the Gulf of Thailand (excluding the Mekong River) was previously considered negligible; however, the present results indicate that such input has impact on the eastern Gulf of Thailand. The warm humid climatic conditions in Southeast Asia are the primary factors that affect the strong chemical weathering in the study area, followed by the nature of the parent rock.Keywords：clay mineral;surface sediment;provenance;coast of Thailand12|0|0Updated：2024-10-14
- Abstract：Cold seeps are widely developed on the seabed of continental margins and can form gas plumes due to the upward migration of methane-rich fluids. The detection and automatic segmentation of gas plumes are of great significance in locating and studying the cold seep system that is usually accompanied by hydrate layers in the subsurface. A multibeam echo-sounder system (MBES) can record the complete backscatter intensity of the water column, and it is one of the most effective means for detecting cold seeps. However, the gas plumes recorded in multibeam water column images (WCI) are usually blurred due to the interference of the complicated water environment and the sidelobes of the MBES, making it difficult to obtain the effective segmentation. Therefore, based on the existing UNet semantic segmentation network, this paper proposes an AP-UNet network combining the convolutional block attention module and the pyramid pooling module for the automatic segmentation and extraction of gas plumes. Comparative experiments are conducted among three traditional segmentation methods and two deep learning methods. The results show that the AP-UNet segmentation model can effectively suppress complicated water column noise interference. The segmentation precision, the Dice coefficient, and the recall rate of this model are 92.09%, 92.00%, and 92.49%, respectively, which are 1.17%, 2.10%, and 2.07% higher than the results of the UNet.Keywords：multibeam;water column image (WCI);gas plumes;UNet;automatic segmentation12|0|0Updated：2024-10-14
Geology
- Abstract：Microorganisms in sediments are critical to marine ecosystems. The microbial communities in marine sediments of the Bohai Sea (BS) and Yellow Sea (YS), the eastern Chinese marginal seas, were uncovered in employing the metagenomic approach. In addition, the taxonomic and functional compositions of microbes were compared among various sediment core depths. Results showing the compositions, diversities, and functions of the microbial communities showed no significant variations with sea areas, and significant seasonal variations was observed in station 3500-7 only on functions of the microbial communities. Moreover, the compositions, diversities, and functions of the microbial communities changed noticeably in different sediment depths in close correlation with physical and chemical properties of sediments. However, the large fraction of the variation in functional communities remained unexplained. From bioinformatic analysis of the metagenomic data, the carbon-metabolism-related genes such as glycosyl transferase (GT), glycoside hydrolase (GH), and carbohydrate esterase (CE) genes were rich in the microbial community, especially in the top sediment depth. Additionally, in this N-polluted habitat, nitrification and anaerobic ammonia oxidation (anammox) were dominant in the top sediment depth, whereas dissimilatory nitrate reduction to ammonium (DNRA) and denitrification were dominant in the middle and bottom depth, respectively. Further identification of possible biogeochemical links suggested that Gammaproteobacteria, Alphaproteobacteria, Nitrospirae, Nitrospinae, Chloroflexi, and Methanomicrobia might promote effective circulation of carbon and nitrogen cycling. This study expanded our knowledge about the structure and functional potential of microbial communities associated with different sediment depth, and provided further comprehensive information on element cycles in marine environments.Keywords：microbial community;function;metagenome sequencing;marine sediments12|0|0Updated：2024-10-14
- Abstract：The Liaoning Hongyan River Nuclear Power Plant is located on the east coast of Liaodong Bay in the Bohai Sea, China, and the safety of the cooling water is often threatened by large-scale jellyfish outbreaks. Thus, monitoring jellyfish growth, migration, and disappearance is essential to the safety of the nuclear power plant. In this study, high-throughput sequencing was used to analyze the community characteristics of mesoplankton in the sea area at the inlet and outlet from April to September 2019. At the same time, the micro-individuals of jellyfish (including oosperm, planula, polyps, or ephyra of jellyfish) in the water were detected by real-time fluorescent quantitative PCR (qPCR). Both the maximum abundance of Aureliacoerulea and Nemopilemanomurai in July were detected by high-throughput sequencing and qPCR. Only three common taxa of plankton (Paracalanus, Calanoida, and Poaceae) were found in the waters near the inlet and outlet, and the beta diversity of plankton in the waters near the inlet and outlet was low in the same period. Based on the plankton community composition in the sea water near the inlet, it could be speculated that jellyfish outbreaks would have a significant impact on the plankton via the predation effect. The maximum mt-16S rDNA copy numbers of A. coerulea and N. nomurai in the samples from the waters of Liaodong Bay were detected in June 2019, and that of N. nomurai showed an increasing trend from north to south, with the jellyfish tending to move to the seawaters near the plant. The results indicate that the optimum monitoring period for jellyfish outbreaks in Liaodong Bay is from the end of May to the end of July.Keywords：jellyfish;Aureliacoerulea;Nemopilemanomurai;molecular monitoring;community12|0|0Updated：2024-10-14
- Abstract：Substrate is an important abiotic factor for burrowing shellfish, as it not only provides them with shelter, but also impose significant effect on their physiological metabolism. However, the physiological responses of burrowing clams within various substrates get less attention due to difficulty in carrying out physiological tests in buried conditions. Consequently, this study investigated the burrowing behavior, feeding physiology and energy budget of Paphia undulata, which is an important aquaculture bivalve species in south China. The clams were exposed to mud and sand substrates with variable physical properties in the laboratory, to determine the suitable substrate conditions for this species. The results showed that the percentage of burrowing clams, digging index, burrowing time, burrowing depth and scope for growth (SFG) were higher in mud substrates with
- Abstract：Paclobutrazol is a plant growth regulator and inhibitor of endogenous gibberellin synthesis. It is a powerful inhibitor of vegetative growth by changing the photosynthetic rate and plant hormone levels, thereby affecting plant growth and development. In this study, the effects of paclobutrazol on the model diatom Phaeodactylum tricornutum were investigated. Results show that 2.5-mg/L and 10-mg/L paclobutrazol significantly inhibited the algal growth by inhibiting chlorophyll synthesis, which affects photosynthesis. The antioxidant system, including catalase (CAT) and glutathione peroxidase (GPx) was severely damaged. Chrysolaminarin content was significantly elevated and doubled up to 127 mg/g dry cell weight (DCW) by 10-mg/L paclobutrazol treatment. In combination with transcriptomic analysis, paclobutrazol was demonstrated to play a regulatory role in the accumulation of chrysolaminarin and neutral lipids.Keywords：chrysolaminarin;lipid;paclobutrazol;diatom12|0|0Updated：2024-10-14
- Abstract：Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes. However, little is known about the interactions between successional and existing species of different growth forms, particularly under the low light and high nutrient conditions of eutrophic lakes. We measured the functional traits of mature Vallisneria natans (Lour.) Hara plants and Potamogeton crispus L. shoots in monoculture and mosaic patterns under different light and nutrient conditions. The effect of light on functional traits of the submerged macrophyte species was more significant than that of nutrients, but the reverse was true for P. crispus biomass allocation. Moreover, interspecific interactions affected only the submerged macrophytes under the low light condition and varied with species. Specifically, the interaction of P. crispus to V. natans was biased towards competition, while the interaction of V. natans to P. crispus was converted from facilitation to competition by eutrophication, particularly in the homogenous mosaic growth pattern. This study demonstrates that sufficient light is a prerequisite and patch planting is an effective means to form a multispecies submerged vegetation system. In addition, we emphasize that the coexistence of eutrophication and low light will likely result in a competition between submerged macrophytes thus simplifying the vegetation, even if their growth forms and growing seasons are different. These findings help explain the collapse of multispecies submerged vegetation and guide the restoration of aquatic plants in eutrophic lakes.Keywords：submerged macrophyte;light;nutrient;monoculture;mosaic;interspecific interaction12|0|0Updated：2024-10-14
- Abstract：The Mediterranean basin is considered one of the most vulnerable areas in the world under the impacts of global warming and changes in precipitation patterns. Oubeira, a shallow and polymictic freshwater lake located in northeastern Algeria (36°50′N, 08°23′E), has recently experienced a significant proliferation of harmful cyanobacteria resulting in the generation of toxins. We carried out this study in order to understand the succession patterns of dominant cyanobacteria and cyanotoxin production and the factors driving this in Oubeira Lake. A total of 26 cyanobacterial genera were identified, and among them Microcystis and Planktothrix accounted for more than 60% of the overall cell abundance. The summer/fall period was dominated by Microcystis, Planktothrix, and in lesser extend by Cylindrospermum, Cylindrospermopsis. During the fall/winter transition, Dolichospermum, Pseudanabaena, and Aphanizomenon were the dominant genera. Statistically, the bloom-forming cyanobacteria showed significant differences between months but not between stations. Intracellular microcystins (MC-LR) was detected in all collected samples (0.62- and 19.14-μg MC-LR equivalent/L), but appeared in high concentrations throughout the period of dominance of Microcystis and Planktothrix. Microcystis was more sensitive to nutrients than to temperature. Planktothrix was more dependent on temperature than on nutrients, which explains their coexistence during summer-fall period. However, both genera are positively correlated with MC-LR and would probably be the main producers of microcystins. Pseudanabaena, Dolichospermum, and Aphanizomenon co-occurred at the end of Planktothrix dominance period (December). Aphanizomenon and Pseudanabaena were correlated negatively with temperature and positively with water conductivity. Dolichospermum showed a strong positive correlation with MC-LR. Oubeira Lake, could serve as a model of how cyanobacteria blooms may develop in lakes within Mediterranean climates.Keywords：Oubeira Lake;cyanobacteria;microcystin;spatiotemporal variations;shallow hypereutrophic lake19|0|0Updated：2024-10-14
- Abstract：The use patterns of salt marsh habitats by fish assemblages were investigated in two well-developed intertidal creeks in the Changjiang (Yangtze) River estuary on spatial and temporal scales. Samples were collected using fyke nets at two sites during day and night in each season throughout four years. Notable changes in fish assemblages were detected over seasonal and interannual cycles, with many more marine species present in winter assemblages, whereas freshwater and estuarine species characterized the other seasonal samplings. The appearance of catadromous species in intertidal creeks mainly depended upon their specific physiological requirements, such as spawning migration. No significant diel shifts were observed in fish assemblages. This diel pattern may be a combined consequence of avian predation pressure and other drivers (i.e., inherent living behaviors, food availability, and predation by piscivorous fishes). The spatial difference in fish community was insignificant even though the two intertidal creeks were different in size. Intertidal creeks with different size could possess similar ecological value for fish fauna. Redundancy analysis (RDA) showed that biological factors exerted greater effects on fish assemblages than physical variables. Temporal variations were strongly facilitated by food availability, but negatively impacted by avian predation. Salinity, water temperature, and river runoff had weak influence on temporal variations of fish communities. The length-frequency distribution showed that the fish collected in these two sites mainly consisted of young-of-year and juvenile fish, which confirmed that the creeks provided important nursery and forage roles in the process of fish ontogenetic development. Further, we proposed that salt marsh conservation management should be equally applied to all well-developed intertidal creeks regardless of creek size.Keywords：fish;temporal variation;intertidal creeks;Changjiang (Yangtze) River estuary12|0|0Updated：2024-10-14
Ecology
- Abstract：Pavlova sp. is not only one of the most popular microalgae in aquaculture, but also a source of high-quality biodiesel feedstock. With white light as a control (W), Pavlova sp. was cultured in this study under varying light quality, including monochromatic red light (R), blue light (B), and combinations thereof with different proportions (illuminators of mRnB, comprised of m red light units and n blue ones, m+n=7), to examine the effects of illuminating light quality on biocomponent production and biodiesel quality. The results show that combined monochromatic light, especially 2R5B, 3R4B, 4R3B, and 5R2B, could improve the growth of Pavlova sp. The dry weight of harvested algae powder in the 5R2B group reached 418.03 mg/L, and was 22.65% higher than that in the control group (W). Lipid production under combined monochromatic light of 4R3B reached 107.86 mg/L, and was 25.61% higher than in the control (W). In addition, illumination using 4R3B increased the proportion of C16∶0 (palmitic acid) and C16꞉1 (palmitoleic acid) fatty acids in Pavlova sp. by 15.55% and 21.94%, respectively, which translates into improved biodiesel quality. All cetane numbers (CN) for 4R3B–6R1B were over 51, while iodine values (IV) and degrees of unsaturation (DU) were reduced, leading to more stable biodiesel suitable for long-term storage. In addition, protein production under 6R1B was as high as 31.56 mg/L, 1.8 times greater than under W. Light quality is proposed as an effective tool to regulate biocomponent production by microalgae.Keywords：Pavlova sp.;light quality;growth;lipid;biodiesel12|0|1Updated：2024-10-14
- Abstract：Variation in metabolite profiles of Haematococcus pluvialis (a type of unicellular green algal) under light stress is a key issue of study at the present. To investigate the effect of light intensity on accumulation of astaxanthin in H. pluvialis, a 26-day batch culture experiment of H. pluvialis under the light intensity levels at 73, 127, 182, 236, and 291 μmol/(m2·s) was conducted. Therefore, the optimal light intensity and the corresponding metabolic pathways of accumulation in H. pluvialis were determined. Results show that 236 μmol/(m2·s) was the optimum light intensity to induce astaxanthin accumulation, at which a maximum content of 9.01 mg/L was achieved on Day 24. A total of 132 metabolites were identified and quantified, of which 38 differential metabolites were highlighted and classified, including 3 fatty acids or intermediates, 5 amino acids or derivatives, 5 carbohydrates or intermediates, 16 nucleoside derivatives, and 9 other metabolites using LC-MS/MS technique. Subsequently, 16 statistically significant differential metabolic pathways were enriched and annotated based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis between the control and the 236 μmol/(m2·s) treatment group (P<0.05). In addition, the bioprocesses included cellular basal metabolism and signaling systems, such as carbohydrate metabolism, amino acid metabolism, glycerol and derivatives metabolism, nucleotide and derivative metabolism, and inositol phosphate metabolism were activated and regulated under strong light stress conditions. Moreover, 4 hub metabolites containing D-glucose-6-phosphate, L-tyrosine, glycerol-3-phosphate, and L-glutamine were identified, based on which the associated metabolic network was constructed. The study provided a metabolomic view of astaxanthin accumulation in H. pluvialis under strong light stress.Keywords：Haematococcus pluvialis;astaxanthin;high light stress;metabolomic analysis13|0|0Updated：2024-10-14
- Abstract：The main protease (Mpro) is essential for the replication of SARS-COV-2 and therefore represents a promising anti-viral target. In this study, we screened Mpro inhibitory peptides from Ulva prolifera protein on in-silico proteolysis. Cytotoxicity analysis using the online toxic prediction tool ToxinPred revealed that all the peptides were non-cytotoxic. The hexapeptide (SSGFID) exhibited high Mpro inhibitory activity in molecular docking and its IC50 value was 139.40±0.82 μmol/L in vitro according to fluorescence resonance energy transfer assay (FRET). Quantitative real-time (qRT-) PCR results show that SSGFID could stimulate the expression of mitosis-related factors, including nuclear factor-κB, cyclin D1, and cyclin-dependent kinase 4, to promote the proliferation of mice splenocytes. Stability study revealed that SSGFID showed resistance against pepsin and trypsin but lost D (Asp) after pretreatment at 121 °C for 15 min. Besides, SSGFID was mainly transported through the Caco-2 cell monolayer by the peptide transporter PepT1 and passive-mediated transport during the transport study. Unfortunately, the peptide was also degraded by Caco-2 intracellular enzymes, and the transfer rate of intact peptide was 4.2%. Furthermore, Lineweaver–Burk plots demonstrated that SSGFID possessed a mixed inhibitory characteristic with Mpro. Our study indicated the potential of Ulva prolifera as antiviral and immune-enhancing functional food ingredients and nutraceuticals.Keywords：Mpro inhibitory peptide;Ulva prolifera protein;in-silico proteolysis;immunomodulatory peptide;gastrointestinal digestion;transport study12|0|0Updated：2024-10-14
- Abstract：The brown seaweed, Sacchairnajaponica, has been used in traditional Chinese medicine for over one thousand years. Oral administration of fucoidan or low molecular weight fucoidan (LMWF) from S. japonica could ameliorate kidney dysfunction in chronic kidney diseases and inhibit diabetic vascular complications. In many studies, LMWF was found to be more potent than fucoidan with high molecular weight. However, the pharmacokinetics of LMWF still remains unclear. The purpose of the research is to compare the pharmacokinetics of fucoidan with high molecular weight (136 kDa) with that low molecular weight (9.5 kDa) after oral administration to ICR mice. Since fucose is the main and representative monosaccharide of fucoidans, we evaluate the pharmacokinetics of fucoidan and LMWF by determining the fucose concentration in mice serum. Both fucoidan and LMWF were absorbed following oral administration. Fucoidan and LMWF were provided to mice by oral administration with 60 mg/kg and the maximum Concentration (Cmax) was found at 2.5 h (0.66±0.32 mg/L) for Fucoidan and 1.5 h (1.01±0.56 mg/L) for LMWF, respectively. It seems that LMWF had a higher area under the curve (AUC0–t) and was absorbed more quickly than fucoidan. The estimated bioavailability of LMWF was 28.3% in the mice treated with a single dose of 30 mg/kg. In addition, LMWF was found widely spreaded into different tissues following oral administration and the highest concentration was found in kidney at 19.93±7.02 μg/g. In this study, we first studied the pharmacokinetics of LMWF, in order to help to understand the function of LMWF. And our results shed light on the potential of development of drugs based on LMWF.Keywords：fucoidan;low molecular weight fucoidan;pharmacokinetics;bioavailability;tissue distribution12|0|0Updated：2024-10-14
- Abstract：The quantitative realtime polymerase chain reaction (RT-qPCR) is a powerful and sensitive method to measure expression of targeted gene but it highly relies on the use of suitable reference genes for data normalization. We evaluated the expressions of 8 housekeeping genes: 18S ribosomal rDNA (18S rDNA), 28S ribosomal rDNA (28S rDNA), rubisco large subunit (rbc-L), β-actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), elongation factor 1 (EF1), β-tubulin (TubB), and P-phycoerythrin B (PEB), to select the suitable reference genes for different life-history stages (tetrasporophyte, carposporophyte, and male/female gametophyte) of Gracilaria vermiculophylla by absolute quantitative method. Softwares geNorm and BestKeeper were used to verify the results acquired from copy number analysis. Results show that the expression of identified reference genes varied in comparing groups composed of different type of life stages. It is suggested that 18S rDNA and TubB could be used for highly complex samples composed of mixed ploidy and phases. 18S rDNA and 28S rDNA were also preferred for using among the matured isomorphic samples. But for samples with different maturities, TubB and ACT were recommended for tetrasporophytes and gametophytes respectively.Keywords：reference gene;Gracilaria vermiculophylla;life-history stage;quantitative real-time polymerase chain reaction (RT-qPCR);red algae12|0|0Updated：2024-10-14
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Long-term in-vitro culture and subculture of the hemocytes of swimming crab
Portunus trituberculatus Abstract：Crab cell line, especially continuous crab cell line, can provide us a useful tool for studies on the virology, immunology, and molecular biology of crabs. However, no continuous crab cell line has been available due to the lacking of suitable medium and the occurrence of mitosis-arrest. In this study, long-term in vitro culture conditions for both two- (2D) and three-dimensions (3D) were successfully developed for the circulating hemocytes of swimming crab Portunus trituberculatus, designated as PTH cells. In 2D culture, a novel crab basic medium in osmolarity of 990–1 100 mOsm/kg was optimized for the first time, which is different from Leibovitz’s L-15 medium in mainly the components of amino acids, containing double strengths of the contents of free amino acid mixture in the crab serum. Then an optimal crab growth medium was developed by supplementing 5% fetal bovine serum, 50-g/L yeast extract powder, 20-µg/L basic fibroblast growth factor and epidermal growth factor into the optimal crab basic medium, and found that it could support a long-term survival of PTH cells in a healthy monolayer up to 347 days and partially break through the mitosis-arrest of crab cells evidenced by the obvious increase of proliferating potential detected in the 10-d primarily cultured PTH cells. These 2D cultured PTH cells could be successfully sub-cultured for 11 times by physical flushing method and well cryopreserved in liquid nitrogen. In 3D culture, using the same crab growth medium, the PTH cell aggregates could be easily formed and healthily maintained on the surface of solidified Matrigel or in the ultra-low-attachment plate with a survival rate of 50%–60% on Day 103. This work largely improved the primary culture and subculture of crab cells and will facilitate the establishment of continuous crab cell line.Keywords：crab;Portunus trituberculatus;hemocyte;long-term cell culture;subculture;3D culture12|0|0Updated：2024-10-14 - Abstract：Glutathione S-transferases (GSTs) are a superfamily of multifunction enzymes involved in the regulation of redox homeostasis and innate immune responses against various pathogenic infections in marine invertebrates. In the present study, a delta class GST gene (designated as FcδGST) was cloned from Fenneropenaeuschinensis using rapid amplification of cDNA ends (RACE) technology. The complete cDNA sequence of FcδGST was 780 bp in length, which includes a 27-bp 5′ non-coding region (UTR), a 117-bp 3′ UTR, a 636-bp open reading frame (ORF), and a polyadenylate signal site (AATAAA) presented at the upstream of poly A tail. The FcδGST gene encoded 211 amino acids peptide, including a GST_N domain and a GST_C domain, and exhibited high similarity with previously reported delta GSTs. The predicted molecular mass of FcδGST protein was 23.39 kDa, and its theoretical isoelectric point (pI) was 5.34. The FcδGST mRNA transcripts were ubiquitously expressed in all the tested tissues, with the highest expression level in hemocytes and hepatopancreas. During the stimulation of Vibrioanguillarum or white spot syndrome virus (WSSV), the mRNA expression of FcδGST in hemocytes and hepatopancreas revealed significant up-regulation. The purified recombinant FcδGST protein (designated as rFcδGST) exhibited specific catalytic activity against 1-chloro-2, 4-dinitrobenzene (CDNB) substrate with relatively low stable enzymatic activities. These results indicated that FcδGST was a fragile but typical novel delta class GST member and potentially involved in the innate immune responses of F. chinensis.Keywords：glutathione S-transferase;innate immunity;Fenneropenaeuschinensis12|0|0Updated：2024-10-14
- Abstract：The sea urchin Heliocidaris crassispina has northern expanded in geographic range to Toga Bay, Oga Peninsula in the Sea of Japan due to the global warming. To demonstrate the gonad traits and age structure of H. crassispina in the central range and compare the difference with those in northern extended range, we collected 100 H. crassispina individuals from a barren off Shitsumi, Fukui (central range), in August 2018. Their growth, gonad traits (size, development and color), and sex ratio were investigated and compared with those in Toga Bay, in August 2014 (extended range). The successive 2012–2016 year classes of H. crassispina indicated successive juvenile recruitment in the central range, as found in the extended range. The individuals at three years old in central range were obviously larger than those in the extended range, showing large test diameter and body weight, possibly due to the higher temperature in central range than that in northern extended range. In addition, a balanced sex ratio in the central range was found, in contrast to the female-skewed sex ratio found in the extended range. Gonadal development was sex- and site-dependent. The testicular development in the central range was not only delayed in comparison to ovarian development, but also less delayed than those in the extended range, which possibly attribute to the higher water temperature in the central range. A significantly lower male gonad index and L* (lightness) value was recorded in central ranges compared to that in extended range, possibly due to the releasement of sperm of H. crassispina in central ranges.Keywords：Heliocidaris crassispina;age;gonad development;gonad color;range extension12|0|0Updated：2024-10-14
- Abstract：An interesting group of cymbelloid diatoms was collected from lakes in Yunnan Province, China, and observations on their valve morphology made using light and scanning electron microscopy. These cymbelloid species all have apical pore fields, slit-like areolae, and areolar occlusions, and they all lack of stigmata. In this paper we propose the new genus Qinia gen. nov. for these taxa and describe them as new: Q. lashii sp. nov., Q. aequalis sp. nov., and Q. daliensis sp. nov. The genus Qinia gen. nov. has lanceolate valves asymmetrical about their apical axes, raphe located in the middle of valve, distal raphe ends bent to the dorsal margin that bisects the apical pore fields (APFs), no stigmata, areolae with slit-like external openings and projections occluding the areolar openings internally. This genus resembles the genus Cymbella in the presence of APFs, but differs from Cymbella by a lack of stigmata, and by having external distal raphe ends that bisect the apical pore fields. Like Reimeria, the external distal raphe ends bisect the lobes of the APF, but Qinia species differ from Reimeria in that they have no stigmata and the distal raphe ends are deflected dorsally, not ventrally. Comparisons were made between Qinia and other cymbelloid genera whose members possess apical pore fields. Features that distinguish each species of the new genus are also discussed.Keywords：freshwater;new genus;cymbelloid diatom;morphology14|0|0Updated：2024-10-14
- Abstract：Benthodytes tetrapapillata sp. nov. was collected from a seamount located on the Caroline Ridge at a depth of 2 289 m, during the cruise of R/V Kexue in June 2019. We provided detailed descriptions of external and deposits morphology. The phylogenetic analyses based on cytochrome c oxidase I (COI) and a concatenated dataset of 16S and COI genes showed that the new species belonged to Benthodytes that is not monophyletic. Both details of morphological comparisons and molecular analyses confirmed that Benthodytes tetrapapillata sp. nov. is a new psychropotid species. A state of main morphological characters in valid species of Benthodytes is also provided in this study.Keywords：Holothuroidea;Benthodytes;16S;cytochrome c oxidase I (COI);new species;phylogenetic analysis12|0|0Updated：2024-10-14
Biology
- Abstract：Carnivorous fish have poor tolerance to carbohydrate in feed and low utilization rate of carbohydrate. Therefore, the balance of carbohydrate and lipids in the nutrient metabolism of carnivorous fish, the effective conversion and utilization of carbohydrate and lipids, and the feedback regulation of feeding are the key links for the efficient utilization of carnivorous fish feed. Carbohydrate response element binding protein (ChREBP) is a new transcription factor found in recent years in the glucose signaling pathway, and can also participate in feeding regulation. We performed in-vivo and in-vitro experiments to reveal the role of ChREBP in the glucose metabolism and feeding in mandarin fish. The mRNA expression of ChREBP and appetite regulatory factors were measured after intraperitoneal injection of glucose in mandarin fish Siniperca chuatsi and cotransfection with glucose and glucose+siRNA in the hypothalamic cells in mandarin fish. The results reveal that at hour 2 and 4 post intraperitoneal injection with 1 mg/g BW glucose, the blood glucose level of the mandarin fish increased significantly, but food intake decreased significantly, and it also displayed a significantly increased ChREBP mRNA expression levels in liver. At hour 4 post injection, hypothalamic ChREBP mRNA level was significantly increased, whereas the mRNA expression levels of appetite genes neuropeptide Y (npy) and agouti-related peptide (AgRP) were decreased significantly. When the glucose concentration was 40 mmol/L, the expression level of ChREBP mRNA in mandarin fish hypothalamic cells was significantly up-regulated, but the expression level of appetite gene npy mRNA was down-regulated. When siRNA and glucose were co-transfected into mandarin fish brain cells, the expression level of chrebp mRNA was significantly decreased, and the appetite gene npy mRNA was significantly increased. The results indicated that glucose regulated food intake through the modulation of appetite gene npy by C hREBP.Keywords：Siniperca chuatsi;mandarin fish;carbohydrate response element binding protein (ChREBP);glucose;ingestion;RNA interference10|0|0Updated：2024-10-14
- Abstract：Accurate species identification is a key component of biodiversity research. DNA barcoding is an effective molecular method used for fish species identification. We aimed to study the DNA barcoding of fish in Zhoushan coastal waters, explore the differences and applicability of two gene fragments (12S rRNA and COI) of DNA barcoding in fish species identification, and established a comprehensive fish barcoding reference database. Two hundred and eighty-seven captured fish samples from Zhoushan coastal waters were identified using morphological characteristics and DNA barcoding. A total of 264 12S rRNA sequences (belonging to eight orders, 31 families, 55 genera, and 66 species) and 188 COI sequences (belonging to seven orders, 30 families, 48 genera, and 58 species) were obtained. The lengths of the 12S rRNA sequences ranged from 165 to 178 bp, and the guanine-cytosine (GC) content was 45.37%. The average 12S rRNA interspecific and intraspecific genetic distances (K2P) were 0.10% and 26.66%, respectively. The length of the COI sequence ranged 574–655 bp, and the content of GC was 45.97%. The average 12S rRNA interspecific and intraspecific genetic distances (K2P) were 0.16% and 27.45%, respectively. The minimum interspecific genetic distances of 12S rRNA and COI (1.23% and 1.86%) were both greater than their maximum intraspecific genetic distances (2.42% and 8.66%). Three molecular analyses (NJ tree, ABGD, and GMYC) were performed to accurately identify and delineate species. Clustering errors occurred when the 12S rRNA sequences were delimited using the NJ tree method, and the delimitation results of ABGD and GMYC are consistent with the final species identification results. Our results demonstrate that DNA barcoding based on 12S rRNA and COI can be used as an effective tool for fish species identification, and 12S rRNA has good application prospects in the environmental DNA (eDNA) metabarcoding of marine fish.Keywords：DNA barcoding;cytochrome C oxidase subunit I (COI);12S rRNA;fish identification;species delimitation;Zhoushan coastal waters12|0|0Updated：2024-10-14
- Abstract：Oxidative stress induced by factors such as ammonia nitrogen has become a major issue in shrimp farming. The effects of carotenoids on the growth and antioxidant capability of Litopenaeus vannamei juveniles were investigated in this study using dietary archaeal carotenoids supplementation. For four weeks, shrimp were given diets containing 0 mg/kg (Ctrl) and 55.98 mg/kg (Car) archaeal carotenoids. Dietary archaeal carotenoids significantly enhanced the astaxanthin content in shrimp muscles and carapaces, as well as the superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity (P<0.05). The malonaldehyde (MDA) content in Car group significantly decreased (P<0.05). The transcriptome analysis was conducted to determine the molecular processes in response to archaeal carotenoids supplementation. A total of 1 536 differentially expressed genes (DEGs) were detected, including 538 upregulated DEGs and 998 downregulated DEGs. GO functional enrichment analysis between Ctrl and Car indicated that 26 GO terms including extracellular region, metabolic process, and proteolysis were enriched. The KEGG pathway enrichment analysis revealed that the amino sugar and nucleotide sugar metabolism, cysteine and methionine metabolism, glycine serine and threonine metabolism, and amino acid biosynthesis were enriched. Archaeal carotenoids influenced the expression of several important genes involved in reactive oxygen species (ROS) generation, Nrf2 signaling, and antioxidant enzymes. Seven DEGs were chosen to confirm the RNA-Seq data using qRT-PCR. The genes and pathways discovered in this work assist to elucidate the molecular processes through which archaeal carotenoid enhances L. vannamei antioxidative system.Keywords：archaeal carotenoid;Litopenaeus vannamei;transcriptome;antioxidative mechanism12|0|0Updated：2024-10-14
- Abstract：Jinjiang oyster Crassostrea ariakensis, a species with economic and ecological value, is distributed along the estuaries and coasts of East Asia. With the decline in natural resources, the conservation and aquaculture of this species is urgent. However, studies characterizing their shell shape remain scarce. We investigated the morphological differences in the shells of wild Jinjiang oysters from six populations (Qinzhou, Shanghai, Nantong, Qingdao, and Binzhou hard or muddy bottom) along the coast of China. The color of the shell and adductor muscle scar showed associations with temperature gradient along its geographical distribution. Oyster shape was defined by shell height to shell length ratio, and the ratio varies among geographic locations of the populations. They were found nearly round (Qinzhou and Nantong populations), oval (Qingdao and Binzhou populations), or water-droplet-shaped (Shanghai population). Binzhou populations living on muddy substrates are more elongated than those on hard substrate. In addition, we developed a method to measure the cavity volume in oysters. Correlation and path analysis showed that shell height significantly influenced cavity volume. The synergistic effect of the two factors (the height, length, and width of the shell in pairs) on the cavity volume resulted in differences between northern and southern groups: samples from the southern group (Qinzhou and Shanghai) showed correlation between shell height and shell width, while those from the northern group (Nantong, Qingdao, and Binzhou) showed correlation between shell height and shell length. All populations showed significant correlation between shell height and cavity height, and shell length and cavity length, while the correlation between shell width and cavity width was minimal, which may have been resulted from uneven shell thickness. The linear equation for shell height and cavity volume under different ratios of shell height to length was obtained. In this study, we determined that shell height has the most influence on cavity volume, and specific cavity volume fitting linear equations are given for different shell types, which may provide a reference for future oyster breeding for shell shaping.Keywords：shell shape;cavity volume;correlation analysis;path analysis;Crassostrea ariakensis14|0|0Updated：2024-10-14
Aquaculture and Fisheries
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