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Volume 43 ， Issue 5 ， 2025
- Abstract：A cyclonic eddy (CE) is often accompanied by an anticyclonic eddy (AE) to the east of Vietnam in the South China Sea (SCS) in summer, but the dipole lifetime and the intrinsic connection between CE and AE are still understudied. Data from 1993–2021 reveal that the dipole lifetime are significantly correlated with the wind direction and speed in the dipole region. Higher wind speed was found to be associated with more eastward wind direction and tends to longer dipole lifetime. The wind stress work (WW) on the eddy is much stronger in the eastward jet region than in the CE and AE regions. Comparing of results of 12 higher and lower wind speed years reveal that higher wind can produce stronger mean current, WW and barotropic instability (T4) that further enhances eddy kinetic energy (EKE) and dipole lifetime. The correlations between the dipole CE and AE characteristics are insignificant on interannual scales and mostly insignificant on seasonal scales in the surface layer but significant on seasonal scales in the subsurface layers. In addition, the daily mean vertical profiles (0–500 m) of EKE, vorticity and total deformation rate (TD) between CE and AE remain significantly correlated throughout the dipole’s lifetime, which can be a useful criterion for judging if two eddies are a dipole.Keywords：South China Sea (SCS);dipole eddy;dipole lifetime;wind stress work24|15|0Updated：2025-10-16
- Abstract：We used the ocean reanalysis dataset SODA2.2.4 to investigate the relationship between the interior branch of subtropical-tropical cells (STCs) in the Pacific Ocean and El Niño-Southern Oscillation (ENSO) over interdecadal timescales between 1930 and 2010, as well as the possible mechanisms involved. Interior transport within the upper pycnocline layers of STCs (InSTC) along 9°S (InSTC9s) shows a significant correlation of 0.54 with ENSO over the study period. However, there is an interdecadal shift in the relationship between InSTC along 9°N (InSTC9n) and ENSO. The correlation coefficient between InSTC9n and ENSO is not statistically significant between 1930 and 1965 (PD1), but is as high as 0.68 (significant at the 95% confidence level) between 1965 and 2010 (PD2). Composite and regression analysis suggests that this shift may be caused by the relationship between InSTC9n and the tropical wind field. During PD1, InSTC9n was driven primarily by the local wind field outside equatorial region, with a relatively weak response to the equatorial wind related to ENSO. In contrast, during PD2, the wind field associated with InSTC9n showed a similar spatial distribution to that of ENSO within the equatorial region, indicating a close relationship between InSTC9n and ENSO. The wind stress curl associated with ENSO drives the anomalous InSTC9n in off-equatorial regions, whose signal can propagate westward in the form of Rossby wave and modulate the thermal structure of the tropical Pacific, favoring the development of ENSO. The possible connection between the Atlantic Multidecadal Oscillation (AMO) and interdecadal changes in the ENSO-InSTC9n relationship was also examined. There is a significant connection between the AMO and the interdecadal change in the relationship between ENSO and InSTC9n; however, the associated mechanism remains to be explored in future studies.Keywords：interior subtropical-tropical cells (STCs);interdecadal change;El Niño-Southern Oscillation (ENSO);Atlantic Multidecadal Oscillation (AMO)12|22|0Updated：2025-10-16
- Abstract：Marine heatwaves (MHWs) have become increasingly frequent and persistent in the context of global warming and the related underlying mechanisms are strongly region-dependent. We employed the NOAA (National Oceanic and Atmospheric Administration) CRW (Coral Reef Watch) daily mean sea surface temperature dataset spanning from 1985 to 2022 to comprehensively analyze the fundamental attributes and evolving patterns of marine heatwaves in the offshore waters of China. Eight pronounced marine heatwaves from frequently affected sensitive regions were investigated to explore their formation mechanisms. The relationship between the occurrences of marine heatwave and large-scale climate mode in the region was explored. Results show that the western Pacific subtropical high plays an essential role in triggering marine heatwaves in Chinese offshore waters, with an anomalous downward shortwave radiation flux acting to warm the sea surface, which is remotely associated to the large-scale sea surface temperature state. Distinct mechanisms for the MHWs were identified in the northern and southern offshore waters of China. MHWs in high latitudes (such as the Bohai Sea and the Yellow Sea) mainly occur during the negative phase of the Pacific Decadal Oscillation (PDO), while those in low latitudes (such as the South China Sea) are more common in about 5-month lags behind the El Niño, for which we purposed a mechanism to describe the main differences in the formation of MHWs in China and discussed the related implications.Keywords：marine heatwave;the offshore waters of China;Western Pacific Subtropical High;El Niño-Southern Oscillation (ENSO);Pacific Decadal Oscillation (PDO)18|20|0Updated：2025-10-16
Physics
- Abstract：Island-arc magmatism is a crucial process in the Earth’s crustal growth. However, how the island-arc magma production rate (MPR) changes and the key influencing factors remains unclear. This study employs numerical models to simulate island-arc growth, incorporating slab dehydration, mantle hydration and melting, and melt extraction. In addition, the impacts of convergence rate and slab dip angle on island-arc magma production were studied. Results suggest that, (1) MPR increases with higher convergence rates; high convergence rates enhance slab water transport efficiency and mantle wedge convection, thereby promoting water fraction and temperature in potential molten regions; (2) MPR initially rises and then falls as the slab dip angle varies from 30° to 45°, and to 60°. This variation is closely tied to water content in the wedge rather than mantle temperature. However, a higher slab dip promotes dehydration towards the potential-melting mantle wedge, which causes water to ascend to shallow areas and reduces the area of the potential molten region. Ultimately, a dip angle of 45° is optimal for retaining the most suitable water fraction and mantle wedge area, thereby maintaining the largest MPR; (3) convergence rate variation has a much larger influence on magma production rate than dip angle variation. When the convergence rate varies from 2 to 10 cm/a, the largest time-averaged MPR is 64.0 times the smallest one, whereas when the slab dip varies from 30° to 60°, the largest time-averaged MPR is only 3.5 times the smallest one. These findings align with numerous instances observed in modern-day subduction zones.Keywords：island-arc magmatism production rate (MPR);convergence rate;slab dip angle;mantle wedge temperature;hydration fraction;mantle melting9|19|0Updated：2025-10-16
Geology
- Abstract：Frequent typhoons can significantly change the temperature, nutrient availability, and phytoplankton biomass in marginal seas. The oceanic response to typhoons is usually influenced by the features of the typhoon, among which the translational speed is critically important. By using a high-resolution coupled physical-biological model, we investigated the response of the Yellow and East China seas (YECS) to two typhoons at different translational speeds, Muifa in August 2011 and Bolaven in August 2012. The model well reproduced the spatial and temporal variations of temperature, chlorophyll-a concentration over the YECS. Results show that typhoons with slower translational speeds uplift more deep water, leading to a more significant oceanic response. Divergence and convergence caused nutrient fluxes in opposite directions in the surface and bottom layers. Moreover, the nutrient flux in the bottom layer was greater than that in the surface layer. These phenomena are closely related to the spatial distribution of nutrients. Further studies show that the degree of ocean response to typhoons is highly correlated with the initial conditions of physical and biological elements of the upper ocean before the typhoon, as well as with ocean structure. Pretyphoon initial conditions of oceanic physical and ecological elements, mixed layer depth, and potential energy anomalies can all alter the degree of typhoon-induced oceanic response. This study emphasizes the important roles of the translational speed of typhoons and the initial oceanic conditions in the oceanic response to typhoons.Keywords：typhoon;Yellow and East China seas (YECS);translational speed;Ekman pumping6|23|0Updated：2025-10-16
- Abstract：The property of water mass plays an important role in determining the distribution of phytoplankton in the ocean. In the Yellow Sea, summer stratification constrains water exchange and differentiates the properties of the Yellow Sea Cold Water Mass (YSCWM) and surface water, which in turn affects the spatiotemporal patterns of phytoplankton communities. Here, based on four summer cruises in the Yellow Sea, we examined the response of phytoplankton pigment assemblages to three water masses, including surface water (water mass Ⅰ, WM-Ⅰ), thermocline water (WM-Ⅱ), and the YSCWM (WM-Ⅲ). Based on the opportunities for group dominance across the four cruises, Cyanophyceae, Haptophyceae, Chlorophyceae, and Cryptophyceae preferred living in WM-Ⅰ, characterized by relatively higher temperature and light intensity but lower nutrients; Bacillariophyceae, Chlorophyceae, Cyanophyceae, and Dinophyceae dominated in WM-Ⅲ, with relatively lower temperature and light intensity but higher nutrients. In comparison, the highest diversity of the dominant pigment groups was observed in WM-Ⅱ with intermediate temperature, light, and nutrient levels. The Dirichlet regression model identified the key environmental factors driving changes in phytoplankton assemblages in WM-Ⅰ, Ⅱ, and Ⅲ as dissolved inorganic phosphate (DIP), DIP and light, and temperature and ammonium, respectively. Under the impact of global environmental change, the fluctuations of key driving forces and their potential ecological implications need further investigation.Keywords：phytoplankton;stratification;Yellow Sea Cold Water Mass;nutrient7|20|0Updated：2025-10-16
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Long-term dynamics of net-phytoplankton community under environmental drivers in Jiaozhou Bay, China
Abstract：To better understand the spatial variations in phytoplankton abundance and community structure and their relationship with environmental parameters in Jiaozhou Bay, Yellow Sea, in Shandong, East China, observations were conducted to estimate abundance of net-phytoplankton and key groups along with environmental parameters in three typical sites in seasonal survey from 2004 to 2016 in the bay. The spatial patterns of phytoplankton abundance differed obviously between the inner and the outer bay. The abundance of total phytoplankton and diatoms increased obviously in the northern part of the bay, while decreased in the southern part and outer bay. An increase in dinoflagellate abundance was obvious in the outer bay. Variations in the dynamics of phytoplankton abundance could be largely explained by the succession of chain-forming diatoms and dinoflagellates. The key chain forming diatom groups Chaetoceros and Thalassiosira increased markedly, especially in winter in the northern part of the bay, while in the southern part and the outer bay, Chaetoceros declined. Besides, the key dinoflagellate groups Ceratium and Noctiluca increased noticeably, resulting in a significant increase in the dinoflagellate/diatom ratio in the outer bay. These variations has a significant correlation with environmental variables of surface seawater temperature, phosphorus, nitrogen, salinity, and N/Si ratio (P0.05). For the key groups, temperature was the primary driver of dinoflagellate abundance, while the N/P ratio was critical for chain-forming diatoms. The abundance of phytoplankton showed a clear spatial pattern and associated obviously with environmental factors in the marine ecosystems, offering insights into coastal ecosystem management and conservation strategies.Keywords：phytoplankton;abundance;long-term variation;environmental factor;Jiaozhou Bay8|14|0Updated：2025-10-16 - Abstract：Phytoplankton plays a crucial role in the energy flow and nutrient cycling of aquatic ecosystems. To understand the spatial and temporal distribution of phytoplankton in the Wujiang River, Yungui Plateau, SW China, samples were collected in 12 locations in wet and dry seasons and analyzed. We hypothesized that phytoplankton assemblages would exhibit significant temporal variability, with niche breadths of dominant species fluctuating seasonally, leading to distinct patterns of species association and community stability. Results show differences in community structure between the two seasons, but such changes did not cause non-significant differences in α-diversity. Diatoms were dominant in the assemblages in terms of biomass, while the numerical abundance of Cyanobacteria was highest in the wet season due to their relatively small cells. Rainfall-driven changes in runoff significantly altered nutrient availability, which in turn strongly affected phytoplankton structure. The more intense water flow contributed to a greater β-diversity in the wet season, driven primarily by species replacement, with stochastic processes played a more important role during the dry season. In the dry season, dominant species exhibited a broader niche breadth and greater niche overlap, along with more positive species associations, suggesting a more stable and resilient community structure. Conversely, in the wet season, species had narrower niche breadth and less niche overlap, leading to a less stable community. Both negative and positive species associations were observed, indicating a complex balance between environmental filtering and competition within the assemblages. These findings provide important insights into how seasonal environmental changes, particularly water flow and nutrient dynamics, shape phytoplankton communities in aquatic ecosystems. Understanding the mechanisms driving changes in community and stability is critical for predicting the impacts of climate change and managing aquatic biodiversity, as fluctuations in water flow and nutrient input may alter ecosystem functioning and productivity.Keywords：plateau river;dry and wet season;diversity;neutral community model;co-occurrence4|12|0Updated：2025-10-16
- Abstract：Inexpensive flocculant-modified iron tailings sand (ITS) were converted into effective flocculation materials for cyanobacteria blooms. After composite modification with polyaluminum chloride (PAC) and polyacrylamide (PAM), the surface charge of ITS was altered from negative to positive, and surface adhesion was increased by ~1.5 times. PAC/PAM-modified ITS (PP-ITS) had strong flocculating effects on cyanobacteria, facilitating their removal. When the dosage of PP-ITS was 150 mg/L and the ratio of flocculant to ITS was 1꞉20, the elimination rate of cyanobacteria was as high as 90%. The flocs formed were better than those with chitosan-modified clays (CS-CA) and PAC-modified ITS (PAC-ITS) in terms of settling velocity, size, and recovery ability. The positively charged groups in the flocculant, such as -NH2 and Al3+, are attracted to negatively charged ions on the surface of ITS, altering the surface charge. Additionally, hydrogen bonds could form between amide side groups, and surface adhesion was improved through molecular association. Coupled with the strong bridging and sweeping effects of the flocculant, the flocs generated by PP-ITS formed rapidly and were large and resilient. The use of PP-ITS could effectively treat cyanobacteria blooms as well as solve the problem of ore tailings disposal. These results are of practical importance for engineering strategies to control cyanobacteria blooms, though there are still some issues that need to be addressed, such as how cyanobacteria flocs are collected and utilized after settling.Keywords：flocculation material;cyanobacteria bloom;flocculation mechanism;iron tailings sand (ITS);settling velocity10|16|0Updated：2025-10-16
- Abstract：Coral reefs support a wide range of organisms in the world, including jellyfish and their benthic relatives. However, quantifying the biodiversity of these organisms in reefs is a challenge because of their uneven distribution and cryptic early life stages, requiring the validation of alternative techniques for biodiversity assessment. Here, the biodiversity and spatial distribution patterns of jellyfish and their benthic relatives, from the Scyphozoa, Hydrozoa, and Ctenophora taxa (hereafter referred to as SHC), were investigated in the coral reefs of Xisha, China, using environmental DNA (eDNA) metabarcoding technology by collecting shallow seawater, mesophotic seawater, and sediment samples. One-hundred and eighty-eight SHC species spanning two phyla (Cnidaria and Ctenophora), three classes, 11 orders, 65 families, and 104 genera were identified, among which hydrozoans were the most dominant taxa, accounting for 89.81% of all SHC species. SHC species showed low connectivity between shallow and mesophotic habitats, presenting a clear vertical distribution pattern in coral reefs. In the mesophotic coral ecosystems (MCEs), 140 SHC species (84.34%) were detected, of which 39.76% were exclusive to MCEs, with Zanclea sp.1, Orthopyxis integra, and Fabienna sphaerica being the dominant species. Additionally, although SHC diversity in seawater was higher than that in the sediment samples, 22 species were identified only in the sediment samples, indicating that sediment eDNA may represent a valuable supplementary tool for the investigation of SHC communities in hot spots. In addition to revealing the vast diversity of SHC species occupying coral reef ecosystems in the Xisha Islands, our findings confirm the potential of eDNA metabarcoding as an advanced tool for monitoring the biodiversity of cryptic species.Keywords：eDNA metabarcoding;mesophotic coral ecosystem;biodiversity;spatial distribution9|12|0Updated：2025-10-16
- Abstract：Understanding the seasonal variations of the zooplankton community’s structure in the Western Pacific Warm Pool (WPWP)—the most stable open marine environment in the Pacific Ocean—is crucial to predict the impacts of climate change on the ecosystem. However, knowledge on these variations in this region down to the mesopelagic zone is insufficient. In this study, the environmental DNA (eDNA) metabarcoding method was used to investigate the zooplankton community during summer, autumn, and winter, from the surface to a depth of 1 000 m spanning the epipelagic to mesopelagic zones. The zooplankton community structure exhibited seasonal fluctuations at multiple depths except for 200 and 1 000 m. In addition, a stronger zooplankton seasonality was particularly recorded in the epipelagic zone than in the mesopelagic zone, which is consistent with the environmental changes. The studied zooplanktons are dominated by medusae and copepods that showed distinct seasonality. At all depths, medusae exhibited greater seasonal variations than the overall zooplankton community, whereas the copepods did not exhibit significant seasonality. The environmental features and the seasons exerted greater influences on the structure of the zooplankton communities than did the spatial factors. The results of this study indicate that eDNA metabarcoding can provide novel insights into zooplankton assemblages due to its ability to capture a rich variety of medusae, which are often underestimated by net collection.Keywords：seasonality;zooplankton community;medusa;copepod;eDNA metabarcoding;Western Pacific Warm Pool (WPWP)6|14|0Updated：2025-10-16
- Abstract：The abundance of live and dead Oithona similis in Jiaozhou Bay, Shandong, China, was investigated monthly from December 2008 to November 2009 via the neutral red staining method. The annual variation in total abundance was similar for females, males, and copepodites, with a main numerical peak from February to July and a minor peak in November, but the variations in carcass abundance and death proportion were different. The monthly average abundance of male and copepodite carcasses significantly increased with their total abundance (P0.001), whereas no such correlation was observed for females. The abundance of female carcasses peaked at 12.4 inds./m3 in November but remained below 3.0 inds./m3 in all other months. The monthly average death proportion ranged 0.3%–4.9% for females, 3.6%–25.7% for males, and 2.6%–8.4% for copepodites. On average, the death proportion of males was 9.2 times greater than that of females and 3.5 times greater than that of copepodites. Therefore, significant sexual difference exists in the non-predatory mortality of O. similis and this difference is an important cause of the female-skewed sex ratios observed in the field.Keywords：Oithona similis;non-predatory mortality;Jiaozhou Bay;death proportion;staining method10|5|0Updated：2025-10-16
Ecology
- Abstract：Ulva prolifera, the primary causative species of green tide, has garnered significant attention due to its robust growth and reproductive capacity under high salt stress. However, there has been relatively little research on the regulation of high salt stress in this species. In this study, we observed that high salt stress suppressed the growth of U. prolifera and leading to the nitric oxide (NO) accumulation, along with increased gene expression levels and enzyme activity of S-nitrosoglutathione reductase (GSNOR). Treatment with GSNOR inhibitor resulted in elevated NO levels under high salt stress, accompanied by reduced activity of antioxidant enzymes and decreased glutathione (GSH) accumulation, making U. prolifera more sensitive to high salt stress. Conversely, NO scavenger treatment not only reduced NO levels, but also weakened the high salt stress tolerance of U. prolifera. Furthermore, using tandem mass tags (TMT) switch analysis and mass spectrometry, we observed a significant increase in S-nitrosylated protein levels in U. prolifera under high salt stress, with further augmentation upon GSNOR inhibitor treatment. We also found high salt stress induced S-nitrosylation (SNO) of glutathione reductase (GR), which is negatively regulated by GSNOR, resulting in increased GR activity. Our results show that under short-term high salt stress, the elevated expression level of GSNOR avoided excessive accumulation of NO, and a certain amount of NO enhanced the activity of antioxidant enzymes through SNO modification, which improve the high salt stress tolerance of U. prolifera, whereas under long-term high salt stress, excessive NO was toxic to U. prolifera.Keywords：Ulva prolifera;high salt stress;antioxidant;S-nitrosoglutathione reductase (GSNOR);S-nitrosylation9|6|0Updated：2025-10-16
- Abstract：Cyclotella cryptica, a model diatom known for its robust adaptability to variable salinity and temperature conditions, is a promising candidate for large-scale biotechnological applications. Nutrient availability, particularly nitrogen and phosphorus, plays a crucial role in the metabolic activities of microalgae, influencing its industrial utility. Exploring the relationship between these essential nutrients and both the yield and biochemical composition of this microalga is crucial for optimizing cultivation strategies. However, research focusing on the effects of nitrogen and phosphorus on C. cryptica remains limited. We investigated the impacts of varying concentrations of nitrate (0.25–3.96 mmol/L) and phosphate (14.4–229.6 μmol/L) on C. cryptica culture by analyzing its growth performance, photosynthetic activity, biochemical composition, and biosilica deposition. Results indicate that C. cryptica exhibited enhanced growth, photosynthetic efficiency, and carotenoid production under higher nutrient concentrations. However, the effects of nitrate on macronutrients composition and fatty acids profile differed from those of phosphate. Specifically, increased nitrate levels resulted in higher concentrations of polyunsaturated fatty acids (PUFAs) at the expense of saturated fatty acids (SFAs), while increased phosphate levels were associated with increased PUFAs and reduced monounsaturated fatty acids (MUFAs). Additionally, biosilica deposition was weakened by elevated nitrate but enhanced by increased phosphate levels. This study improved our understanding of nutrient-mediated regulatory mechanisms in diatoms and contributed valuable data to the broader field of algal biotechnology. Moreover, these findings are expected to advance the development of tailored nutrient management strategies, thereby enhancing the industrial potential of C. cryptica.Keywords：Cyclotella cryptica;nitrate;phosphate;fucoxanthin;frustule8|4|0Updated：2025-10-16
- Abstract：5-hydroxytryptamine (5-HT) is a biological monoamine neurotransmitter in the central nervous system and gonads of crustaceans to induce gonadal maturation. To better understand the effects of 5-HT and its receptors on reproductive development in Artemia, a 5-HT type 7 receptor gene (5-HT7Ar) was identified in parthenogenetic Artemia and characterized. Sequence analysis revealed that the open reading frame of 5-HT7Ar encodes a 414-aa protein. 5-HT7Ar showed higher expression in both brain and ovary at early embryo stage, 5-HT7Ar could be detected during ovarian development and the highest expression was observed at early embryo stage. Silencing of the 5-HT7Ar in Artemia at early embryo stage decreased significantly the expression level of 5-HT7Ar gene and protein at late oocyte, early embryo, and late embryo stage. Moreover, silencing of the 5-HT7Ar resulted in a decreased fecundity, which corresponds to abnormal oocytes during the embryo development. Artemia tended to produce nauplii after the silencing of 5-HT7Ar, indicating that 5-HT7Ar may also involve in the determination of its reproduction mode. The findings of this study provide an insight into the regulation of reproductive development in Artemia and the function of 5-HT7Ar.Keywords：parthenogenetic Artemia;5-HT7Ar gene;RNAi;fecundity;reproductive mode6|19|0Updated：2025-10-16
- Abstract：Antarctic krill (Euphausia superba) is a keystone species in the Southern Ocean; however, seasonal variations in reproductive development for krill are complex and remains unknown. A histological investigation with observations of external secondary sex features of krill in the south Scotia Sea region was carried out using a multi-seasonal dataset for detail reproductive descriptions for this commercially important species. The monthly development of secondary sexual characteristics, the thelycum, as well as of oocytes over a period of two years were described. It was observed that krill have diverse reproductive development characteristics within the ovary, and that this function differently between the juvenile, sub-adult, and adult stages. During the summer, adult krill ovaries are large and ripe with oocytes rich in yolk ready for release in late summer. Post spawning, the ovaries resorb, fragment, and regress throughout the autumn and winter. During reproductive diapause period, krill focus on absorbing nutrients. Un-released eggs are reabsorbed by the ovary, the permanent germinal zone is active, and early oocytes begin to develop in preparation for the egg production phase. Krill that are about to spawn have an ovary that fills the space between the digestive gland and muscle. The ovarian development of krill is divided into 10 sexual developmental stages. As a part of this study, data on the carapace thickness with similar development patterns in krill size and carapace width, was investigated for the first time to help understand krill growth and development.Keywords：Antarctic krill;ovarian development;reproduction;histology;seasonality6|1|0Updated：2025-10-16
- Abstract：Sea cucumber Apostichopus japonicus is a crucial aquatic species known for its nutritional value. However, the genetic basis and regulatory mechanisms underlying its nutritional quality remain underexplored. This study investigates the nutritional quality of A. japonicus from different geographical regions and identifies genetic markers associated with these traits through a genome-wide association study (GWAS). We observed significant regional variations in the nutritional content of A. japonicus. Samples collected from Nanhuangcheng Island displayed the highest levels of saponins, whereas those from Laizhou exhibited the highest concentrations of glycosaminoglycans. Lingshan Island samples were the richest in amino acids, while samples from Rizhao contained the highest levels of polyunsaturated fatty acids. Through GWAS, 265 candidate genes and related single nucleotide polymorphisms (SNPs) were identified as being significantly associated with essential nutritional traits, including genes like ubiquitin domain-containing protein 1 (UBTD1), inactive pancreatic lipase-related protein 1, protein arginine N-methyltransferase 5 (PRMT5) and GDP-fucose protein O-fucosyltransferase 1 (POFUT1). This study advanced our knowledge of the genetic mechanisms underlying the nutritional quality of A. japonicus. The genetic markers identified herein offer crucial insights for breeding initiatives aimed at optimizing the nutritional profile of sea cucumbers.Keywords：Apostichopus japonicus;nutritional quality trait;genome-wide association analysis;nutritional quality-related single nucleotide polymorphism (SNP)7|13|0Updated：2025-10-16
- Abstract：Recently, more and more bacteria have been reported to become tolerant to antibiotics. In this study, one tnaA gene involved in indole production, and the effect of exogenous indole on the formation of persister cells specific to tetracycline in Vibrio splendidus were characterized. The tnaAVs gene was first cloned and conditionally expressed in Escherichia coli Rosetta (DE3). To investigate the regulatory effect of TnaAVs, the tnaA deletion strain AJ01/∆tnaA was constructed by in-frame deletion. The undetected extracellular indole in the AJ01/∆tnaA indicated that TnaA was the solo enzyme to produce indole in V. splendidus. The drop plate method showed that AJ01/∆tnaA was more tolerant to the higher concentration of tetracycline than that of AJ01, being 340-fold higher in the proportion of survived cells when cell density OD600≈0.65. Moreover, the synergistic effects of indole and tetracycline on killing of V. splendidus were determined. Results show that addition of 2-mmol/L indole increased the susceptibility of both AJ01 and AJ01/∆tnaA to 10×minimum inhibitory concentration tetracycline. To explore the genes and pathways regulated by TnaAVs, the transcriptomic analysis between AJ01 and AJ01/∆tnaA was performed. Result shows that TCA cycle, arginine biosynthesis, quorum sensing and microbial metabolism in diverse environments were downregulated, while the ribosome pathways, the protein metabolic process, peptide biosynthetic and metabolic process were upregulated in the AJ01/∆tnaA. This study shows that indole could enhance the bactericidal effect of tetracycline on V. splendidus by decreased ribosome level probably but increased ATP level.Keywords：Vibrio splendidus;indole;persister cell;transcriptomic analysis8|0|0Updated：2025-10-16
- Abstract：A halophilic bacterium, named Halomonas sp. NEC-1 was isolated from the Nyer Co Salt Lake on the Xizang Plateau, SW China. The strain exhibited a broad pH tolerance range of 5–11, distinguishing it from Halomonas alkaliphila despite a 99% genetic similarity. Optimal growth conditions, determined through orthogonal experiments, were found to be 37 °C, 100-g/L salinity, and an initial pH of 6, resulting in a maximum OD600 of 7.98±0.06. Halomonas sp. NEC-1 produced 545.43±25.10 mg/L of ectoine under optimal conditions of 75-g/L salinity, 40-g/L sodium glutamate, and an initial pH of 6. This production increased to 1 388.81±3.69 mg/L after five rounds of hypo-osmotic shocks. During the shocks, ectoine productivity remained stable at approximately 16.29±0.04 to 17.28±0.48 mg/(L·h), representing a 43.40%–52.11% increase compared to the rate without any shock (11.36±1.05 mg/(L·h)). Additionally, the expression of the ectABC gene cluster, related to ectoine synthesis, significantly increased following the shocks, enhancing ectoine production. The ectoine extract demonstrated notable protective effects on Escherichia coli and plasmid DNA. After 10 min of exposure at 60 ℃, the colony count of E. coli treated with ectoine extract increased by 342% compared to treatment with distilled water. Furthermore, the ectoine extract protected plasmid DNA from 2,2′-Azobis (2-methylpropionamidine) dihydrochloride-induced damage. This study highlights Halomonas sp. NEC-1 is a promising strain for ectoine production and underscores the potential of microbial resources in salt lakes from Xizang region.Keywords：halophilic microorganism;ectoine;salt lake;Xizang6|2|0Updated：2025-10-16
Biology
- Abstract：Glugea plecoglossi, a microsporidia of the Glugea genus, can cause an infamous disease Plecoglossus altivelis in East Asia, resulting in heavy economic losses. At present, the main diagnostic methods for this disease include microscopy examination, quantitative real-time PCR, and loop-mediated isothermal amplification-lateral flow dipstick (LAMP-LFD). In this study, a recombinase polymerase amplification-lateral flow dipstick (RPA-LFD) method, targeting the beta-tubulin gene, was developed to detect G. plecoglossi, three sets of primers and probes were designed and screened, after which the initial reaction system was established. The RPA-LFD method for G. plecoglossi could complete nucleic acid amplification at 39 °C for 10 min, after which the amplification product was dropped on the LFD strip, and the results could then be observed within 5 min. A specificity assay revealed that there was no cross-reactivity with other protozoa except G. plecoglossi. A sensitivity assay revealed that the detection limit was 9.38×106 ng/μL, which was more sensitive than that of conventional PCR. Compared with conventional detection methods, the novel RPA-LFD method has the advantages of simple operation, short operation time, high sensitivity, and high specificity for G. plecoglossi detection, indicating its potential use in rapid field detection of G. plecoglossi.Keywords：Glugea plecoglossi;recombinase polymerase amplification;lateral flow dipstick;rapid detection;Plecoglossus altivelis11|1|0Updated：2025-10-16
- Abstract：Intraspecific conflict induced by the innate aggressiveness is one of the main reasons for the extremely low survival rate in mud crab Scylla paramamosain aquaculture, which have impeded the sustainable culture of the species. In this study, we first classified and quantified the aggressive behavior, and established a crab aggressive behavior model, laying the foundation for subsequent research on evaluating combat intensity. The contents of 5-hydroxytryptamine (5-HT), dopamine (DA), and cAMP in the hemolymph of the mud crabs before and after fighting were measured by high-performance liquid chromatography-mass spectrometry (HPLC-MS), and the mud crabs exhibited a significant increase of 5-HT (P0.05), while the DA and cAMP decreased significantly (P0.05). In addition, we applied EthoVision to examine the changes of the crab behavior after DA administration. After 0.5 h of injection, the movement speed, distance, duration of aggressive behavior, and intensity of aggression in the high concentration DA group were significantly higher than those in the saline injection group and the untreated control group (P0.05). The results of real-time quantitative polymerase chain reaction (qRT-PCR) analysis showed that the expression of DA1 in the thoracic ganglia of the mud crabs was significantly down-regulated in the DA injection group, and the aggressive behavior was weakened. Conversely, DA1 expression was up-regulated when aggressive behavior was strengthened. Besides, there were significant differences in the expression levels of receptor expression genes including 5-HT1, 5-HT2, and crustacean hyperglycemic hormone (CHH) in different tissues, indicating that the alteration of aggressive behavior of the mud crab after injection with different concentrations of DA could be regulated by changes in the expression levels of corresponding receptor genes. Our results contribute to a deeper analysis of the aggressive behavior mechanism of the mud crabs and provide a theoretical basis for reducing fighting-related mortalities in aquaculture.Keywords：Scylla paramamosain;aggressive behavior;behavior model;dopamine (DA);gene expression6|11|0Updated：2025-10-16
- Abstract：A comprehensive fishery-independent survey generally incorporates various specialized surveys and integrates different survey objectives to maximize benefits while accounting for cost limitations. It is important to evaluate the adaptability of the comprehensive survey for different taxon to get the optimal design. However, the validity and adaptability of ichthyoplankton sampling incorporated in a comprehensive fishery-independent survey program in estimating abundance of ichthyoplankton species is little known. This study included ichthyoplankton sampling in an integrated survey and assessed the appropriateness of survey design. The Kriging interpolation based on Gaussian models was used to estimate the values at unsurveyed locations based on the original ichthyoplankton survey data in the Haizhou Bay as the “true” values. The sampling performances of the ongoing stratified random sampling (StRS), simple random sampling (SRS), cluster sampling (CS), hexagonal systematic sampling (SYSh), and regular systematic sampling (SYSr) with different sample sizes in estimating ichthyoplankton abundance were compared in relative estimation error (REE), relative bias (RB), and coefficient of variation (CV) by computer simulation. The ongoing StRS performed better than CS and SRS, but not as good as the two systematic sampling methods, and the current sample size in StRS design was insufficient to estimate ichthyoplankton abundance. The average REE values (meanREE) were significantly smaller in two systematic sampling designs than those in other three sampling designs, and the two systematic sampling designs could maintain good inter-annual stability of sampling performances. It is suggested that incorporating ichthyoplankton survey directly into stratified random fishery-independent surveys could not achieve the desired level of accuracy for survey objectives, but the accuracy can be improved by setting additional stations. The assessment framework presented in this study serves as a reference for evaluating the adaptability of integrated surveys to different objectives in other waters.Keywords：ichthyoplankton abundance;sampling design;adaptability;inter-annual stability7|4|0Updated：2025-10-16
Aquaculture and Fisheries
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