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Volume 43 ， Issue 3 ， 2025
- Abstract：The uncertainty of ocean turbulent mixing parameterization comprises a significant challenge in ocean and climate models. A depth-dependent deep learning ocean turbulent mixing parameterization scheme was proposed with the hydrological and microstructure observations conducted in summer 2012 in the shelf sea east of Hainan Island, in South China Sea (SCS). The deep neural network model is used and incorporates the Richardson number Ri, the normalized depth D, the horizontal velocity speed U, the shear S2, the stratification N2, and the density ρ as input parameters. Comparing to the scheme without parameter D and region division, the depth-dependent scheme improves the prediction of the turbulent kinetic energy dissipation rate ε. The correlation coefficient (r) between predicted and observed lgε increases from 0.49 to 0.62, and the root mean square error decreases from 0.56 to 0.48. Comparing to the traditional physics-driven parameterization schemes, such as the G89 and MG03, the data-driven approach achieves higher accuracy and generalization. The SHapley Additive Explanations (SHAP) framework analysis reveals the importance descending order of the input parameters as: ρ, D, U, N2, S2, and Ri in the whole depth, while D is most important in the upper and bottom boundary layers (D
- Abstract：The variations of the frontogenetic activity of cold filament driven by the different angle (θ=0°, 22.5°, 45°, 67.5°, and 90°) of the wind and wave fields and the filament axis are studied by non-hydrostatic large eddy simulation. Conversion between the frontogenesis and frontolysis of cold filament were created by the chang in the direction of secondary circulations. The changes in the direction of secondary circulation are induced by the Coriolis Effect regardless of wind direction and wave fields. The destructive action of the wind and wave fields on symmetry of the submesoscale flow fields becomes weak as the angle increases. The secondary downwelling jet induced by Stokes shear force is gradually close to that associated with secondary circulations as the angle changes from θ=0° to 45° and then the downwelling jet is only created by secondary circulations for θ=67.5° and 90°. The frontogenetic intensity of cold filament may be impacted by the angle of the wind and wave fields and the filament axis. The reason is that firstly the odd-symmetry of secondary circulations enhances with the angle increasing, and secondary the secondary downwelling jet created the Stokes shear force gradually weakens and then disappears with the angle increasing.Keywords：cold filament;frontogenesis;frontolysis;secondary circulation21|16|0Updated：2025-05-27
- Abstract：The river plume front between the diluted ocean water and salty ocean water in the Changjiang (Yangtze) River Delta (CRD) is well studied. Comparatively, less is known about the estuarine front in the CRD, which is formed between the riverine freshwater and the diluted ocean water and has the highest magnitude of salinity gradient (SG) in the CRD. Estuarine fronts are of great significance to the riverine material transport in the estuary. Many biogeochemical processes are enhanced in estuarine fronts, which have brought about environmental problems. In this study, the seasonal variations of the estuarine fronts in the CRD were studied in wet (July) and dry (January) seasons in 2017, based on model simulations with high spatiotemporal resolutions using the Finite-Volume Community Ocean Model (FVCOM). The estuarine front included several sharp fronts with a SG >4(/500 m), and was bottom-trapped on the submerged delta front. Seasonal changes mainly occurred off the Jiangsu coast, where a significant estuarine front was formed in July. The estuarine fronts generated around the submerged delta topography were accompanied by the offshore extension of older estuarine fronts, which were diluted and evolved into plume fronts over a tidal cycle. The simulated estuarine fronts had a salinity range of 6 to 22 in the dry season and 6 to 14 in wet season 2017. The estuarine fronts hindered the residual current by altering its flow direction to the southeast.Keywords：salinity front;Changjiang River Delta;residual current14|16|0Updated：2025-05-27
- Abstract：Internal solitary waves (ISWs) have considerable energy to drive the mixing of water masses in the Sulu Sea. The propagation speed is one of the critical parameters in quantifying the energy budget of the ISWs. We collected 1 354 groups of ISWs’ speeds from tandem satellite remote sensing images with temporal intervals shorter than 25 min and analyzed their spatial and multi-scale temporal variations in the Sulu Sea. We found that water depth plays an important role in modulating the spatial variation of wave speeds, which increase exponentially with water depth with a power of 0.26. Tidal currents, ocean stratification, background circulation, and climate affect the temporal variations of wave speeds from days to months or years. The fortnightly spring/neap tidal currents cause daily variations of wave speeds up to 40% by modulating the ISW amplitudes. In addition to the well-accepted results that monthly variations of wave speeds are related to density stratification, we found that enhanced stratification increases wave speeds, and the background circulation leads to a maximum decrease of 0.27 m/s in the linear counterparts of wave speed. Moreover, the averaged wave speed collected in October is lower than the corresponding linear one possibly due to some unknown dynamical processes or underestimation of background current. As for the interannual variations, we show that wave speed increases in La Niña years and decreases in El Niño years as a result of the climatic modulation on the depth of the maximum value of buoyancy frequency.Keywords：internal solitary wave (ISW);tidal current;circulation current;El Niño-Southern Oscillation (ENSO);Sulu Sea11|16|0Updated：2025-05-27
- Abstract：A massive amount of plastic waste has presented an immense management challenge. This escalating ecological damage, coupled with the detrimental effects of plastics infiltrating the marine food web, poses a significant threat to human livelihoods. To combat this, there is a call for the development of plastic detection algorithms using remote sensing data. Here we tested a new index, referred to indexMP, to detect clusters of floating macro plastics in the ocean using satellite imagery. The indexMP was applied to convolution high-pass filtered (3×3) Sentinel 2 Level 1C images, showing the potential to reduce atmospheric interference and enhance the object edges, thereby improving the clarity of detection. In the analysis, we used three scatter plots to identify and assess plastic pixels. To differentiate the common features of plastic from non-plastic objects, the Sentinel 2 bands 5, 8, and 9 were plotted against indexMP calculated and convolution high-pass filtered Level 1C (CHPIC) images. The plastic pixels, clustering in the three scatter plots, showed positive ‘X’, i.e., CHPIC image value and ‘Y’, i.e., each band 5, 8, and 9 reflectance values, along with a CHPIC image value exceeding 0.05. Using the indexMP and scatter plot analysis, we identified plastic pixels containing 14% or more plastic bottles. Detection of other types of plastics, such as fishing nets and plastic bags, required pixel proportions greater than 50%. Hence, plastic bottles were notably responsive even at a low pixel fraction. We further explored the classification of plastic and non-plastic objects by analyzing reed (plant) pixels; the differentiation between plastic and reed was conducted in the band 5 and 9 scatter plots.Keywords：floating macro plastic;Sentinel 2;Level 1C image;indexMP;scatter plot22|14|0Updated：2025-05-27
- Abstract：As a frequently occurred marine pollution phenomenon, red tides of water body due to eutrophication cause massive mortality of marine organisms and serious ecological problems. The early warning and prediction of red tide outbreak can provide guidance to the coastal management, and is of great value to the aquaculture industry and marine environment protection. An approach for the risk assessment of red tide occurrence using spectral indices was made. The optimal spectral indices were explored from three candidates, namely two-band ratio (TBR) method, three-band spectral index (TBSI) method, and fluorescence baseline (FLB) method. The correlations between the spectral indices and the red tide occurrence were quantitatively evaluated through analysis of variance (ANOVA). The risk maps for the Beibu Gulf and the Bohai Bay in China were produced with the normalized spectral indices based on the multi-spectral observation from Sentinel-3 satellite. Results show that both TBR and TBSI values have significant correlations with the occurrences of red tide as the ANOVA results. TBSI illustrated correctly the risk of red tide occurrence in the risk maps and was the optimal spectral index offshore risk assessment of red tide. FLB method failed to recognize the high-risk regions and may not be the appropriate spectral index. The risk assessment method proposed in this study can provide early alarms on red tide occurrence and help timely the countermeasure against potential harms.Keywords：red tide;environmental risk assessment;harmful algal bloom;hyperspectral remote sensing;spectral analysis58|22|0Updated：2025-05-27
Physics
- Abstract：The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits. This paper outlines the geochemical features of 24 surface sediments and one sediment core (26V-GC01, 294 cm) along the South Mid-Atlantic Ridge (SMAR) from 18°S to 22°S, an area where hydrothermal active fields have yet to be discovered. The surface sediments mainly consist of biogenic carbonates, aluminosilicates, and hydrothermal Fe-Mn (oxy) oxides. The core sediments primarily comprise organic matter, detrital materials, hydrothermal components, and substances scavenged from seawater. The rare Earth element (REE) patterns suggest the presence of hydrothermal contributions within the surface and core sediments. The enrichment factors for Fe, Mn, Cu, and Zn in surface sediments suggest these metals are concentrated at the 19°S, 21°S, and 21.5°S segments, further indicating their potential as hydrothermal active fields. Downcore variations of Fe, Mn, P, Cu, Pb, V, and Co suggest at least six episodes of hydrothermal activity. The impact of hydrothermal processes on the sediments from SMAR 18°S to 22°S indicates that the study area has the potential to host a significant number of hydrothermal active fields.7|23|0Updated：2025-05-27
- Abstract：The Yangtze Plate (YP) and the North China Plate (NCP) are key components of the East Asian continent, and their collision significantly influences the tectonic evolution of the eastern Asian continental margin. As the South Yellow Sea is located at the convergence of these plates, it becomes a pivotal area for understanding the tectonic evolution of East Asia. The characteristics and provenance of clastic rocks of the Middle Permian-the Early Triassic were analyzed and the strata in the Central Uplift including the Qinglong Formation (T1q) and Talung Formation (P3d), consisting of various mudstones and sandstones, were anatomized. Results show that quartz and feldspar are the main diagenetic minerals, while illite and chlorite show signs of secondary alterations. Geochemical imprints indicate a gradual shift in provenance from ancient sedimentary and mafic igneous rocks to intermediate igneous rocks. In the meantime, the tectonic background transformed from continent to continental island arc from the Middle Permian to the Early Triassic. Therefore, we inferred that a soft collision between the North China Plate and the Yangtze Plate likely occurred during the Late Permian, resulted in intensified collision between two plates in the Early Triassic, and shaped the South Yellow Sea. This study provided valuable information on the timing of plate collisions in the South Yellow Sea.Keywords：South Yellow Sea (SYS);Late Permian-Early Triassic;sedimentary geochemical characteristic;tectonic evolution12|19|0Updated：2025-05-27
Geology
- Abstract：Global coral reef ecosystems have been severely degraded due to the combined effects of climate change and human activities. Changes in the seawater carbonate system of coral reef ecosystems can reflect their status and their responses to the impacts of climate change and human activities. Winter and summer surveys in 2019 found that the ecological community of the Luhuitou coral reef flat was dominated by macroalgae and corals, respectively, contrasting with the conditions 10 years ago. The Luhuitou fringing reefs were sources of atmospheric CO2 in both seasons. In winter, the daily variation range of dissolved inorganic carbon (DIC) in Luhuitou coral reefs was up to 450 μmol/kg, while that of total alkalinity (TA) was only 68 μmol/kg. This indicated that the organic production was significantly higher than the calcification process during this period. The TA/DIC was approximately 0.15, which was less than half of that in healthy coral reefs; hence, photosynthesis-respiration processes were the most important factors controlling daily changes in the seawater carbonate system. The net community production (NCP) of the Luhuitou coral reef ecosystem in winter was as high as 47.65 mmol C/(m2·h). While the net community calcification (NCC) was approximately 3.35 and -4.15 mmol CaCO3/(m2·h) during the daytime and nighttime respectively. Therefore, the NCC for the entire day was -21.9 mmol CaCO3/(m2·d), indicating a net autotrophic dissolved state. In summer, the acidification was enhanced by thunderstorms and heavy rain with the highest seawater partial pressure of CO2 (pCO2) and lowest pHT. Over the past 10 years, the increase rate of seawater pCO2 in Luhuitou reef was approximately 13.3 μatm/a***, six times that of the open ocean, while the decrease rate of pH was approximately 0.008 3/a, being five times that of the global ocean. These findings underscore the importance of protecting and restoring Luhuitou fringing reef, as well as similar reefs worldwide.Keywords：Luhuitou;coral reef;carbonate system;acidification;calcification;dissolution15|13|0Updated：2025-05-27
- Abstract：The epizoic diatoms, especifically those living at the body surface of copepods has not garnered sufficient attention. This study focuses on the copepod Pseudodiaptomus annandalei and three epizoic diatom species isolated from its body surface: Pseudofalcula hyalina, Haslea sp., and Tabularia sp. The research explored the physiological and biochemical characteristics of diatoms under co-cultivation conditions with P. annandalei and different species of epizoic diatoms, along with variations in copepod survival rates. Results reveal that the growth rate, cell density, and chlorophyll-a content of the three epizoic diatoms were enhanced by P. annandalei. The photosynthesis of epizoic diatoms, particularly the photochemical efficiency of PSⅡ (Fv/Fm) of P. hyalina was positively influenced by P. annandalei. The impact of P. annandalei on biochemical compositions exhibited species-specific characteristics. Under co-culture conditions, the content of polysaccharides and proteins in the colloidal exopolymeric substance (CEPS) of P. hyalina and Haslea sp. increased, so did the intracellular protein content of Tabularia sp. The attachment of P. hyalina was most significantly influenced by P. annandalei, followed by Haslea sp., and then Tabularia sp., likely due to the increased uronic acid content of P. hyalina under co-culture conditions. Moreover, the three epizoic diatoms might have served as food sources for P. annandalei, as evidenced by the higher survival of copepods. The release of nitrate and phosphate from P. annandalei contributed to the nutrition for the growth of epizoic diatoms, indicating that the bottom-up effect resulting from P. annandalei excretion nutrition was greater than the top-down effect from predation.Keywords：epizoic diatom;copepod;interaction;biochemical composition7|15|0Updated：2025-05-27
- Abstract：Pigments are widely used as indices for estimation of phytoplankton biomass and composition, and many protocols have been developed to analyze pigments in phytoplankton. Different protocols were compared using four solvents (methanol, 95% methanol, dimethylformamide, and 90% acetone) and two instruments (fluorometer and high-performance liquid chromatography (HPLC) coupled with diode array detector). Analysis of chlorophyll a (Chl a) with fluorometer could lead to over- or underestimation due to the interference from its derivatives in all probability. Among the four extractants, 90% acetone had a high recovery for chlorophylls. In contrast, 95% methanol was a poor extractant for chlorophylls due to the degradation of Chl a, especially in diatoms. The 95% methanol, however, had high extraction efficiencies for most diagnostic xanthophylls. Therefore, the selection of pigment analytical protocols should follow the specific purpose of phytoplankton study. In addition to fluorometry, an HPLC method with 90% acetone as extractant shall be a good choice for the analysis of Chl a to estimate phytoplankton biomass, especially for diatom-dominated samples, while an HPLC method with 95% methanol as extractant be more suitable to characterize different taxa in phytoplankton communities.Keywords：pigment;fluorometry;high-performance liquid chromatography (HPLC);extraction;phytoplankton5|9|0Updated：2025-05-27
- Abstract：To assess the population development of submerged plant species in disturbed lake ecosystems, we need to better understand the genetic diversity and spatial genetic structure at a fine scale, as well as the impact of disturbances on the populations. Caohai Lake, in southwest China, is a suitable natural sampling lake because of its abundance of submerged plants and the intense human disturbance. Three widely distributed species, Potamogeton lucens, Ceratophyllum demersum, and Myriophyllum spicatum, were sampled; the spatial position of each individual was recorded in two-dimensional coordinates; and the species were analyzed genetically using microsatellite markers. Among the species studied, M. spicatum exhibited the highest genetic and clonal diversities. All P. lucens subpopulations but one showed a significant fine-scale spatial genetic structure (FSGS), which may result from the limited gene dispersal. However, M. spicatum and C. demersum, with a relatively large distance of gene dispersal, had no significant FSGS. The FSGS pattern of P. lucens at the dock site with intense boat disturbance was significantly different from that at other sites. Our results imply that the FSGS of submerged plants is affected by many factors including seed dispersal, vegetative reproduction and disturbance from birds and boats. Most subpopulations of the three species had
- Abstract：Decades of species composition changes can lead to the eutrophication-driven loss of submerged macrophytes in shallow lakes. Investigating the mechanisms of these nature- and human-driven changes is crucial for the restoration and management of such lakes. To investigate the changes in aquatic macrophyte communities over the past two centuries, we analyzed macrofossils in sediments from a 210Pb-dated core obtained in Dongping Lake in the lower Huanghe (Yellow) River Basin, eastern China. Multiple factor analysis (MFA) revealed an association between macrophyte shifts and changes in various environmental stressors (invertebrates, grain size, geochemistry, and documented records), indicating that macrophyte community changes before 1960 were predominately driven by flood disturbances. Ever since, anthropogenic pollution and the construction of water conservancy projects have caused variations in hydrology and nutrients, leading to significant changes in the composition of macrophyte communities. Macrofossil data reveal a decline in diversity and pollution-intolerant species during the late 1980s and the early 2000s, which is indicative of eutrophication. We also found that the current environment of Dongping Lake exhibits a clear degeneration in emergent plants and a proliferation of macrophyte species associated with eutrophic conditions, which could be attributed to water level fluctuation and nutrient input due to the water supply from the eastern route of the South-to-North Water Diversion Project as well as climate warming. Our results provide valuable insights for assessing ecosystem health and the restoration and management of Dongping Lake and similar lakes in the Huanghe River region and elsewhere.Keywords：aquatic macrophyte;Dongping Lake;paleoecology;plant macrofossil;restoration;Huanghe River11|3|0Updated：2025-05-27
- Abstract：Global warming has severe effects on cold-water habitats. The Yellow Sea Cold Water Mass (YSCWM) is a typical cold-water habitat in the western Pacific Ocean. The southern YSCWM face much more environmental pressure than the northern YSCWM. We hypothesize that the cold-water Ophiuroid species Ophiura sarsii vadicola, the dominant benthic species in the YSCWM, will be less abundant with an ageing population in the northern YSCWM. Based on a survey in 2018, we found the density of O. sarsii vadicola reached 315 inds./m2 in the northern Yellow Sea, higher than previous records. Biomass and organic mass peaked at 45.5 g/m2 and 4.89 g/m2. There was a strong linear relationship between wet weight and dry weight/ash-free dry weight (AFDW). Over 48 000 individuals were measured (diameter: 1.0–17.5 mm) and were notably smaller than related species from higher latitudes. A Gompertz growth model was established by examining ossicle growth bands. Age structures differed between the northern and southern YSCWM, and the former was dominated by younger individuals. This study enriched our understanding on the ecology of brittle star and provides valuable data and insights for future research on the benthic ecosystems of the Yellow Sea.Keywords：Ophiura sarsii vadicola;population characteristic;growth equation;Yellow Sea46|2|0Updated：2025-05-27
Ecology
- Abstract：Bathymodiolus mussels distribute in both deep-sea cold seep and hydrothermal vent environments, whose endosymbiotic gill tissue is a prominent character for the adaptation of extreme habitats. However, few studies explored the adaptation mechanisms through comparative transcriptome sequencing and analysis of different tissues between seep mussels and vent mussels. We performed the comparative transcriptome sequencing and analysis for three tissue types (gill, mantle, and adductor muscle) of Bathymodiolus mussels collected from a cold seeping site Station S11 and the 50-km away hydrothermal field Minami-Ensei Knoll in the Okinawa Trough. Results show that gene expression patterns had distinct tissue specificity. Compared with the non-endosymbiotic tissues (mantle and adductor muscle), the significantly strengthened gene functions in endosymbiotic gill included microbial recognition (fibrinogen C domain-containing protein 1-B-like (fibcd), fibrinogen-related protein 8 (frp), peptidoglycan recognition proteins (pgrp), and C-type lectin (clec)), cell apoptosis and immunity (interferon regulatory factor 1/2-like 1 (irf), cathepsin D (ctsd), caspase 2 (casp2)), and antioxidant capacity (copper/zinc superoxide dismutase (czsod), glutathione peroxidase (gpx), selenoprotein (sel)), in both seep and vent individuals. Consistent with metal accumulation, high expression levels of genes related to heavy metal detoxification (cytochrome P450 (cyp), ferritin-like ( ftl), metallothionein (mt), glutathione S-transferase (gst)) were also observed in gill. Moreover, to adapt to high hydrostatic pressure in the deep sea, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with cellular community were significantly enriched in all three tissues, suggesting the regulation of cell structure and cell adhesion at transcriptional level. This study obtained gene expression profiles of deep-sea mussels subsisting at cold seep and hydrothermal vent sites, which could lay foundations for comprehensive investigations of molecular basis in adaptation of deep-sea mussels to the two extreme ecosystems.Keywords：Bathymodiolus mussel;adaptation;cold seep;hydrothermal vent;comparative transcriptome18|5|0Updated：2025-05-27
- Abstract：Fish cell line provide a useful tool for studies in virology and molecular biology. To establish a novel continuous marine fish cell line (EFF) from caudal fin tissue of brown-marbled grouper Epinephelus fuscoguttatus, its susceptibility to the crustacean covert mortality nodavirus (CMNV) was evaluated. The primary cell cultures were initiated first by incomplete digestion of fin tissue blocks with dispase and collagenase, and then the explant was cultured in L-15 medium supplemented with 20% fetal bovine serum, 10% grouper muscle extract, and 20-ng/mL growth factors of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). The EFF cells were continuously passaged beyond 50 times in fibroblast-like morphology, and they grew well in L-15 medium supplemented with a lower concentration fetal bovine serum (10%) at 28 °C after passage 10, without muscle extract and the growth factors. In addition, their grouper origin was confirmed by chromosome analysis and cytochrome oxidase 1 (CO1) gene analysis of these EFF cells. Transfection experiment via lipofectamine 8 000 indicated that the EFF cells had a high transfection potential with a transfection efficiency up to 32%. Cross-species viral susceptibility analysis showed that CMNV not only successfully infected the EFF cells as evidenced by obvious cytopathic effects like vacuolation, detachment and death of cells, but also multiplied in the EFF cells as indicated by the results of semi-quantitative RT-PCR in transmission electron microscopy. Therefore, the establishment of immortal EFF cell line provided a useful cell model for future works on the isolation, multiplication, and pathogenic mechanism of cross-species infection of CMNV as well as genetic manipulation.Keywords：Epinephelus fuscoguttatus;fish cell line (EFF);caudal fin;transfection;covert mortality nodavirus (CMNV);cross-species infection6|10|0Updated：2025-05-27
- Abstract：Pyropia yezoensis (red algae) or commonly known as nori, is highly regarded for its nutritional benefits and distinct taste, leading to its widespread consumption. The bio-activity and sensory characteristics of P. yezoensis are attributed to the metabolites it contains. In this study, identification and quantification of the diverse range of metabolites of P. yezoensis and metabolomic analysis were conducted using gas chromatography-mass spectrometry (GC-MS). Furthermore, the impact of high temperature on its metabolites regulation was also investigated. Due to metabolomic analysis, a diverse range of metabolites were identified in P. yezoensis, including lipids, amino acids, carbohydrates, and secondary metabolites. Several known bioactive compounds, including alcohol and polyols, amines, amino acids-peptides-analogues, beta hydroxy acids and derivatives, carbohydrates and carbohydrate conjugates, cholestane steroids, dicarboxylic acid and derivatives, and fatty acids and conjugates were detected in abundance, highlighting the nutritional and functional properties of P. yezoensis. Additionally, the metabolites composition of P. yezoensis was significantly affected in high temperatures, which led to up-regulation of considerable primary metabolites and few were down-regulated, and suggested a potential response and adaptation mechanism of P. yezoensis to elevated temperature conditions. This research highlighted the metabolomics of P. yezoensis, provided insights into its metabolite composition and regulatory responses to high temperature conditions, enhanced our knowledge of the biochemical pathways and adaptive mechanisms of P. yezoensis, which can assist the improvement strategies of utilization and cultivation to promote this valuable alga in response to fluctuating environmental conditions.Keywords：metabolomics;Pyropia yezoensis;metabolite;gas chromatography-mass spectrometry (GC-MS);temperature stress7|9|0Updated：2025-05-27
- Abstract：Saline treatment is a low-cost, simple, and effective method to stimulate astaxanthin accumulation in Haematococcus pluvialis, and is proposed to be applied in the second stage of a 2-stage culture since it does not necessitate changing the medium. To understand the effect of salinity on the astaxanthin production of H. pluvialis, the photosynthetic activity and the biocomponents production in 1- and 2-stage cultures in different salinities were investigated. Except for astaxanthin synthesis, which increased at low salinities of 2 and 5-g/L NaCl, most biocomponent yields decreased in 1-stage cultures as salinity increased. At a salinity of 5-g/L NaCl, the 2-stage culture further increased astaxanthin production to 18.41±0.24 mg/L, which was more than 2.0 times that of the control. Saline treatment led to an overall decrease in photosynthetic performance indices of H. pluvialis, and had an impact on five sites of the electron transport chain: the energy connection between antenna and reaction center of photosystem II (PS II), oxygen evolving complex activity on the donor side, the electron transfer from plastoquinone A (QA) to plastoquinone B (QB) and from plastoquinone (PQ) to receptor side of photosystem I (PS I), and the pool size of the end electron acceptors in PS Ⅰ acceptor side. The excitation imbalance between PS Ⅰ and PS Ⅱ caused by the variance in the electron transfer chain necessitated the synthesis of antioxidants like astaxanthin in order to ensure cell viability. The accumulation of astaxanthin was found to be closely correlated with the stabilized or enhanced the maximum relative electron transfer rate (rETRmax) and the PS II actual quantum yield (QYSS) as well as the increased fluorescence yield at J-step (VJ). This work offers the novel insight of how saline stress controls H. pluvialis photosynthetic activity and astaxanthin synthesis.Keywords：Haematococcus pluvialis;salinity;2-stage culture;astaxanthin production6|4|0Updated：2025-05-27
- Abstract：Jellyfish outbreaks are severely exacerbated by coastal eutrophication, overfishing, and aquaculture. Jellyfish proliferation has been shown closely connected with larval populations during the early stages of their life cycle. However, the factors affecting larval populations have not been fully explored. The changes in metabolites during the transition from planula larvae to polyps were analyzed using ultra-performance liquid chromatography coupled with a mass spectrometer. In jellyfish planula larvae and polyps, lipids and lipid-like molecules are the most abundant metabolites, followed by organic acids and their derivatives, organic heterocyclic compounds, and organic oxygen compounds. In comparison with planula larvae, 13 metabolites were significantly increased while 212 were significantly decreased. Most of these metabolites are involved in lipid metabolism, amino acids metabolism, and nucleotide metabolism. Furthermore, during the jellyfish planula larvae metamorphosis and settlement, five differentially expressed metabolites were identified as candidate metabolites that facilitate larvae attachment and metamorphosis, including glycerol lactate pyruvate, N-stearoyl asparagine, 4-methyl-umbelliferyl-N-acetyl-chitobiose, levetiracetam, and 4-amino-1-[(2R,5R)-5-(hydroxymethyl)-4-sulfanyloxolan-2-yl] pyrimidin-2-one. This study identified the metabolites and helped understand the metabolic mechanisms underlying the attachment and metamorphosis of jellyfish larvae, which expands our knowledge of jellyfish blooming at the early life stage.Keywords：Aurelia coerulea;attachment;metamorphosis;metabolomic;jellyfish outbreak5|1|0Updated：2025-05-27
- Abstract：FOXL2 and CYP19B are crucial transcription factors in vertebrates and invertebrates that play pivotal roles in sex differentiation and gonadal development. The potential roles of the foxl2 and cyp19b genes in sex determination and gonadal development in Cyprinus carpio var. koi were explored using a non-invasive RNA interference (RNAi) method, histopathological observation and qPCR. Results demonstrate that foxl2 exhibited a sexually dimorphic expression pattern in gonads, with a notable expression in ovaries; cyp19b was expressed in all peripheral tissues, with a particularly prominent expression in brain and gonads. The knockdown of foxl2 by RNAi resulted in delay in the development of the female gonads. Conversely, no notable alterations were discerned in the gonads of C. carpio var. koi following the knockdown of cyp19b. The upregulation of sox9a, amh, and cyp19b following foxl2 knockdown indicates that foxl2 may play a pivotal role in gonadal development. Nevertheless, further investigation is required to ascertain the potential role of cyp19b. This study elucidated the role of foxl2 and enhanced the understanding of the mechanisms of sex determination and gonadal development in C. carpio var. koi.Keywords：RNA interference (RNAi);foxl2;cyp19b;sex differentiation;gonadal development4|4|0Updated：2025-05-27
- Abstract：The genus Selenastrum comprises common coccoid green algae found in diverse habitats worldwide. This genus has a complex taxonomic history, but recent applications of molecular phylogenetic methods have removed some members with similar morphologies from Selenastrum and established new genera. However, due to the lack of available molecular sequences and isolates, the species diversity of the genus has not been fully explored. We conducted a detailed examination of the taxonomy of genus Selenastrum based on 11 new strains collected from China. The multi-disciplinary study utilized morphology, ultrastructure, and phylogeny based on multiple molecular markers, and ITS-2 secondary structure. All the included strains of genus Selenastrum were clustered into two distinct clades. The members of one clade were similar morphologically to the type species Selenastrum bibraianum, whereas the strains of the other clade had distinctly different colony structures. Based on the latter clade’s larger colony cell numbers and independent phylogenetic position, we proposed that it as a new species of the genus Selenastrum, namely Selenastrum densum sp. nov. Additional taxa sampling and molecular data will help to discover additional new species and clarify the validity of morphological taxonomic characteristics within the genus Selenastrum.Keywords：colony structure;molecular phylogeny;Selenastraceae;Selenastrum;species diversity9|14|0Updated：2025-05-27
- Abstract：Three new free-living marine nematodes belong to the order Enoplida from the Yellow Sea, China are described. The first new species, Halanonchus gracilis sp. nov. is characterized by inner labial sensilla papillose, outer labial setae and cephalic setae thick, with thin tips; oval amphideal fovea located posterior to buccal cavity; males possessing midventral row of 10–12 papilliform pharyngeal supplements and 13–15 unequal papilliform precloacal supplements; spicules almost straight, 0.85–1.0 cloacal body diameter long; gubernaculum rod-shaped. The main difference between the described species and other known species within the genus is that precloacal supplements are unequal, 6–7 posterior supplements smaller and closer, the rest 7–8 proximal supplements larger and far away. The genus Halanonchus is the first record from the Chinese sea area. The second new species, Micoletzkyia oxycephalata sp. nov. is characterized by very sharp-pointed anterior part of body, paired spicules unequal and precloacal supplement situated anterior to proximal end of spicules. This new species can be easily distinguished from all other known species of Micoletzkyia by outstanding body shape, unequal spicules, stick shaped gubernaculum without apophysis, and the position of precloacal supplement. The third new species, Wieseria zhangi sp. nov. is characterized by slender body with a clavate tail; large amphideal fovea oblong, double contour with a manubrium basally, situated posterior to cephalic setae; spicules short, slightly arcuated, not cephalated proximally, without internal stripe and ventral alae; gubernaculum rodlike, without apophysis; a short midventral spine positioned 11–12 µm anterior to the cloaca. Updated keys to species of three genera Halanonchus, Micoletzkyia, and Wieseria are also given.Keywords：taxonomy;biodiversity0|10|0Updated：2025-05-27
Biology
- Abstract：Marine fisheries catches have significant economic, social, and cultural importance for coastal communities and nations worldwide. In addition to overfishing and predation, oceanic conditions linked to climate variability profoundly affect catches of oceanic fish species. Based on the fishery data from the Food and Agriculture Organization (FAO) of the United Nations and multiple physical and biogeochemical datasets, we examined the correlation between major modes of climate variability at high and low frequency and multiple key fish species in five major fishing grounds worldwide. The results reveal that over 80% of selected key fish species have declined over the past five decades, with more than 50% transitioning from an increasing to a decreasing trend in the 1990s. Additionally, over 80% of fish species directly correlate with low-frequency climate indices, including Pacific Decadal Oscillation (PDO), Atlantic Multi-decadal Oscillation (AMO) and tropical southern Atlantic (TSA). However, less than 40% of fish species exhibit a direct association with high-frequency climate indices of El Niño Southern Oscillation (ENSO), North Atlantic Ocean (NAO), and Atlantic Niño (ATL3). Synthetic analysis on the Sea Surface Temperature (SST), Mixed Layer Depth (MLD) and chlorophyll a revealed that shifts in the low-frequency climate can directly affect the habitats of numerous fish species, and subsequently influence their fishing yields. Specially, negative SST anomalies and positive chlorophyll-a anomalies were observed during a positive phase of PDO in the central and western Pacific regions, resulting in an increased catch values of Alaska pollock, Pacific sardine, and Chilean jack mackerel. Similar changes occur in positive and negative phases of other low frequency indices. Our research offered a comprehensive perspective on oceanic fish catch responses to climate change, serving as a guide for formulating effective management strategies for marine fish resources.Keywords：marine fishery;capture value;low-frequency climate indices;biophysical environment5|4|0Updated：2025-05-27
- Abstract：Hatchery release is a common and effective practice for protecting and restoring wild resources, and the success of the practice is commonly assessed using mark-recapture technology. We investigated the use of different dimensional X-ray imaging techniques for the strontium (Sr) marking of fish fin rays for stocking. Megalobrama amblycephala juveniles were marked by culturing specimens in 800-mg/L SrCl2·6H2O solution, the cross-sections of dorsal fin rays were subsequently obtained, and the concentrations Sr was analyzed by 2D imaging using an electron probe X-ray microanalyzer. Our preliminary findings indicate that the immersion marking method is effective for the Sr marking of fin rays in experimental fish. Moreover, we generated a bird’s-eye-view 3D mesh image of the Sr concentrations, which can provide a more comprehensive information for fish stocking than that using normal 2D imaging.Keywords：fishery restocking;stock enhancement;calcified tissue;chemical marking;microchemistry;effectiveness evaluation11|2|0Updated：2025-05-27
- Abstract：Oysters are of the most economically important bivalves worldwide. It has high nutritional value and is regarded as a good source of proteins, lipids, glycogen, and amino acids. C. gigas and C. angulata are allopatric congeneric dominant oysters that are widely cultivated in the northern and southern coast of China, and have shown remarkable differentiation in the nutritional content. Interspecific hybridization and backcross of the two species are effective ways to improve the nutritional quality of the oyster. Sixteen progenies were constructed based on a 4×4 diallel crosses among broodstock of C. gigas (G), C. angulata (A) and their hybrids GA(H) and AG(R). The glycogen, fatty acids, and amino acids performance of these progenies were evaluated in 22 months after fertilization. The glycogen content of AA was significantly lower than that of the other 15 progenies (P<0.05), while only the GH progeny was significantly higher than the GG (P<0.05), with a heterosis value of 21.06%. The backcross progenies GR exhibited significantly higher saturated fatty acids, eicosapentaenoic acid (EPA), and polyunsaturated fatty acids (PUFAs) content than those of GG (P<0.05), and did not show significant differences from AA. The AA showed significantly higher content of total amino acids (TAAs) than GG (P<0.05). The AH progeny displayed significantly higher taurine (Tau) content than GG (P<0.05), and the heterosis value was 27.88%. Therefore, the backcross breeding was shown an effective way to improve the glycogen, fatty acids, and TAAs of GG, and the glycogen of AA. This study provided useful information to characterize the benefits of backcrossing in nutritional quality, which will facilitate the production of differentiated products and increase the efficiency of the oyster industry.Keywords：Crassostrea gigas;C. angulata;interspecific backcross;glycogen;fatty acid;amino acid8|2|0Updated：2025-05-27
Aquaculture and Fisheries
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