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Volume 44 ， Issue 2 ， 2026
- Abstract：This study evaluates the performance of a Regional Ocean Modeling System-based Hybrid Coupled Model (HCMROMS) in simulating tropical instability waves (TIWs), their modulation by the El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean, and their impacts on the mean state thermal conditions of the ocean. HCMROMS integrates the Regional Ocean Modeling System (ROMS) with a statistical atmospheric model for surface wind stress anomalies based on Singular Value Decomposition (SVD), aiming to accurately represent air-sea coupling interactions and TIWs-related ocean mesoscale processes. The model successfully reproduces the climatological state and seasonal variability of sea surface temperature (SST) in the tropical Pacific. In simulating ENSO, HCMROMS captures the quasi-three-year oscillation characteristic of ENSO. Regarding TIWs, the model accurately reproduces their main features and periods. Additionally, HCMROMS shows a significantly negative correlation between the strength of TIWs and the Niño3.4 index, being consistent with empirical analyses from observations. The model’s ability to simulate the interaction between TIWs and ENSO allows us to analyze the TIWs-related energy and heat budgets. The model’s energy budget reveals that the strength of TIWs is strongly modulated by ENSO phases. The study also examines the feedback effects of TIWs on the mean state through a heat budget analysis. These results indicate that TIWs play a crucial role in the climatological heat balance, with the amplitude being comparable to sea surface heat flux. These findings underscore the importance of accurately simulating TIWs to better represent and understand their role in the tropical Pacific climate system. Overall, HCMROMS demonstrated robust performance in representing both ENSO and TIWs, offering a reliable tool for future studies on their interactions and the broader dynamics of the tropical Pacific Ocean. The model’s precise representations of TIWs and their relationship with ENSO highlight its potential in advancing our understanding of ocean-atmosphere interactions and improving climate predictions.Keywords：Regional Ocean Modeling System (ROMS);statistical atmospheric model;tropical Pacific;tropical instability wave (TIW)56|25|0Updated：2026-05-07
- Abstract：Various physics-based dynamical and data-based statistical models have been developed for uses in predicting sea surface temperature (SST) evolution in relation to the El Niño-Southern Oscillation (ENSO) over the tropical Pacific. At present, clear limitations remain in their ENSO predictions, with predicted SST anomalies (SSTAs) being widely spread across diverse models and considerable inter-model uncertainty. Fortunately, deep learning (DL)-based modeling has recently made promising advances in ENSO prediction tasks; numerous neural networks (NNs) have been constructed for ENSO predictions. However, most NNs themselves are purely data-driven and lack constraints of the necessary physical processes in the coupled system; there are few studies in which DL models are directly integrated with physics-based dynamical models. Previously, such a new type of intermediate coupled models (ICMs) was developed by directly integrating U-Net-derived sea surface wind stress models with an intermediate ocean dynamical model (denoted as ICM-UNet), with demonstrated success in simulating ENSO evolutions in freely coupled runs. It is thus natural to take a step further for prediction applications. In this study, this new ICM-UNet is applied for retrospective ENSO predictions, the first time that such a fusion of DL atmospheric model and dynamical oceanic model with different architectures can be achieved to make ENSO predictions. The overall evaluations indicate that the ICM-UNet yields valid retrospective predictions during the period 1995–2023, confirming that the ICM-UNet is a credible ocean-atmosphere coupled model for ENSO predictions. In case studies during 2020–2023, the ICM-UNet predictions reveal that SSTAs over the equatorial Pacific evolved into a second-year cooling in late 2021 and a warming tendency in 2023, forming a three-year La Niña and an El Niño event thereafter, which is consistent with the reality. The ICM-UNet successful fusion, taking advantage of both the physical constraints due to dynamical oceanic models and nonlinear representations of wind responses due to DL capacity, further underscores the high adaptability of integrating data-driven NNs into the ocean-atmosphere coupled modeling for ENSO-related studies.Keywords：El Niño-Southern Oscillation (ENSO) prediction;intermediate coupled model;deep learning (DL);an integration of DL model with an ocean model;intermediate coupled model (ICM)- UNet107|34|0Updated：2026-05-07
- Abstract：Climate changes lead to significant warming of the Southern Ocean. By analyzing observational products and objective analysis data, this study reveals that the Antarctic Intermediate Water (AAIW) shows a zonal asymmetry of heat content changes, resulting from the different regional responses to the large-scale circulations. The heat content changes show significant interannual to decadal variations superimposed on a long-term trend, mainly attributed to the heat redistribution affected by the atmospheric circulations. AAIW in the Indian sector exhibits a significant widespread warming, and AAIW in the southwest Pacific sector presents an unexpected cooling. Warming has increased by 0.4 ZJ (zettajoules, 1 ZJ=1021 J) per decade since 1979 in the Indian sector, which is equivalent to the heat gain rate of 0.04 W/m2 during 1979–2019 in the Southern Ocean. Upwelling of warm circumpolar deep water driven by upward Ekman pumping, induced by the persistent positive phase of the Southern Annular Mode in recent years, plays a leading role in promoting this warming. The unexpected cooling in the southwest Pacific sector, reaching 0.2 ZJ per decade during 1979–2019, is due to the increasing cold water from sea ice and melting water. An increase of low-pressure anomaly facilitates the shallowing and tilting of isopycnals and the intrusion of cold water into the interior ocean, which is closely associated with the Atlantic multidecadal oscillation. The enhancement of this zonal asymmetry in the AAIW shows an increasing heat content in the Indian sector and a decreasing heat content in the Pacific sector, which implies that the Indian Ocean will become an important potential warming pool in the future.Keywords：Antarctic Intermediate Water (AAIW);Southern Ocean;climate variability;zonal asymmetry82|39|0Updated：2026-05-07
- Abstract：Short-term sea surface temperature (SST) forecasting is an essential operational task around China seas. However, the capability of short-term SST forecast from the dynamical numerical model for China seas has not been fully evaluated so far. We assessed the short-term SST forecast skill using a global eddy-resolving ocean forecast system, i.e., the LICOM Forecast System version 1.0 (LFS v1.0) for China seas in 2022 against satellite SST. Results show that LFS v1.0 was able to forecast the short-term SST variation in the study area. The SST with 1-, 7-, and 15-d lead time well captured the observed SST with average pattern correlation coefficient (PCC) of 0.94, 0.93, and 0.92 throughout 2022, the annual mean bias of the forecasted SST of 0.08, -0.16, and -0.33 ℃, and the average root mean square error (RMSE) of 0.61, 0.72, and 0.90 ℃, respectively. Geographically, the forecast RMSE with 1-d lead time in China seas increased from south to north, and the values were 0.41 ℃ in South China Sea (SCS) and 1.31 ℃ in the Bohai Sea (BS). In addition, LFS v1.0 showed better forecast SST abilities in the SCS and East China Sea (ECS) than those in the Yellow Sea and BS. In the ECS and SCS, the forecasted SST was less influenced by the ocean bottom topography due to accurately simulated ocean circulations like Kuroshio. The RMSEs of the SST forecasted by LFS v1.0 displayed seasonal variations, smaller in the area from the middle of boreal August to the middle of boreal December, and larger in boreal late spring and early summer.Keywords：sea surface temperature (SST);eddy-resolving ocean forecasting system;China seas;short-term forecast36|30|0Updated：2026-05-07
- Abstract：Typhoons can induce significant changes in the upper ocean, increasing sea surface nutrients via mixing, entrainment, and upwelling, which often leads to a substantial phytoplankton bloom in an oligotrophic region of the South China Sea (SCS), subsequently triggers carbon cycling and ecosystem responses, and enhances local marine primary productivity. Using a coupled physical-biogeochemical model, we analyzed the dynamic and ecological responses of the shelf region near the Dongsha Islands in the SCS caused by the fast-moving Typhoon Hagupit, and investigated the underlying mechanisms of sea surface chlorophyll-a increase. Results indicate that after Hagupit, sea surface temperature along the typhoon path rapidly decreased by maximum of 5.2 °C, and the chlorophyll a along the typhoon path increased. In the shelf region near the Dongsha Islands, the sea surface chlorophyll a increased from 0.07 mg/m3 (weekly average) to 0.14 mg/m3 after Hagupit. The maximum increase reached 0.16 mg/m3, occurred 6 days after Hagupit, which is more than twice the average concentration before the typhoon. In contrast, the subsurface chlorophyll a decreased from 0.18 to 0.10 mg/m3. Power spectral analysis of horizontal velocity indicated that Hagupit triggered strong near-inertial waves (NIWs), which had a period of approximately 31.45 h, slightly greater than the local inertial period, and lasted for about one week. Therefore, we believed that while fast-moving typhoons cannot induce strong Ekman pumping velocity (EPV) as slow-moving ones do, they can trigger NIWs. The NIWs enhanced turbulent mixing in the upper 60 m, causing directly a rapid increase in sea surface chlorophyll a and nutrients after the typhoon. Two to three days later, the nitrates uptake by sea surface phytoplankton increased, promoting phytoplankton growth. Therefore, the variability in upper-ocean chlorophyll a induced by fast-moving typhoons involves not only strong dynamic processes but also significant participation of marine biological processes.Keywords：fast-moving typhoon;near-inertial waves;chlorophyll-a concentration;Regional Ocean Modeling System (ROMS)-Carbon, Silicon, Nitrogen Ecosystem (CoSiNE) model;turbulent mixing28|39|0Updated：2026-05-07
- Abstract：With the development of methods for predicting extreme hydrological elements using probabilistic approaches, several commonly used methods have emerged for analyzing the risk of storm surge disasters, including the Annual Maxima method, the Peak-Over-Threshold method, the Gumbel distribution, and the Weibull distribution. Meanwhile, and emphases have been placed on assessing and comparing the applicability and stability of these various methods. To evaluate the rationality of different methods, we an entropy uncertainty analysis method was introduced based on information utilization efficiency, in which the sample Stochastic uncertainty is measured by the ratio of information entropy before and after sampling, i.e., the information extraction efficiency of the sampling method. Additionally, the cognitive uncertainty of the research method is assessed by the ratio of mutual information between the model and the sample to the information entropy of the sample, i.e., the information extraction efficiency of the mathematical model. Furthermore, we incorporated the group probability calculation method, information entropy and mutual information theory to analyze and calculate the entropy uncertainty more accurately. By applying this analysis to the design wave height and the recurrence period projected in the sea area west Guangdong of China, we believed that the most reasonable hazard assessment method shall be based on the over-threshold method combined with the Pareto distribution. Conversely, the assessment method based on the process extreme value method is deemed insufficiently reasonable and requires further research.Keywords：uncertainty;storm surge;information entropy;mutual information;group probability calculation method20|29|0Updated：2026-05-07
- Abstract：Driven by the persistent baroclinic pressure difference, the Luzon Strait deepwater overflow (LSDO) from the Pacific into the South China Sea (SCS) plays an influential role in the dynamical processes in the deep SCS. Based on the ocean bottom pressure (OBP) data, seasonal cycles of the OBP anomalies in the SCS and the LSDO are presented. On the seasonal scale, for shelf areas shallower than 200 m, the OBP anomalies are regulated by the wind stress curls: negative curls in winter lead to the Ekman convergences and the ensuing positive OBP anomalies and vice versa for positive curls in summer, while for the deep basin deeper than 2 000 m, the OBP anomalies show spatial consistency in sign: negative in winter and spring as well as positive in summer and autumn. The seasonal cycle of the LSDO is revealed and found to be mainly due to baroclinic processes east of the Luzon Strait. Along 21.25°N, significant seasonal signals extend downward and westward, reaching about 2 500-m depth at 124°E, and phase isolines are parallel to this extending. These facts suggest that the seasonal variability of the LSDO might originate from the upper ocean and meridional mode Rossby waves could be a possible dynamical mechanism.Keywords：seasonal cycle;ocean bottom pressure (OBP);South China Sea (SCS);Luzon Strait deepwater overflow (LSDO);vertically propagating Rossby wave23|40|0Updated：2026-05-07
- Abstract：The Ice, Cloud and Land Elevation Satellite 2 (ICESat-2) is equipped with an advanced topographic laser altimeter system (ATLAS), which uses a photon-counting technique to achieve high-precision measurements of nearshore bathymetry. The complexity of environmental factors hinders the extraction of signal photons from ICESat-2 data. In this study, we proposed a filtering method for ICESat-2 photon-counting data combing iterative median filter, i.e., skeleton extraction and adaptive ellipse dilation (SEAED). The iterative median filter was employed to differentiate above-water and water-column photons effectively, thereby enabling the precise extraction of signal photons of the water surface. Skeleton extraction, a type of erosion operation, could greatly reduce the number of photons to be processed and maintain underwater terrain features in the raw photon data. Adaptive ellipse dilation can then extract signal photons accurately and completely based on the underwater terrain skeleton. Five regions were selected to verify the accuracy and reliability of the SEAED method. Comparison with measured water depth data and simulated data based on the measured water depth data showed that, the data estimated by SEAED had an optimal root square error of 0.25 m, and an F1 score of 0.983, indicating that the SEAED could significantly improve the filtering accuracy, particularly in complex terrain areas.Keywords：Ice, Cloud and Land Elevation Satellite 2 (ICESat-2);photon-counting airborne light detection and ranging (LiDAR);bathymetry;filtering method27|38|0Updated：2026-05-07
- Abstract：Bottom frictional dissipation is one of the key mechanisms regulating the tidal movement in the areas surrounding Taiwan Island, China. However, our existing understanding in this field remains incomplete, because the bottom friction coefficient (BFC) of this area is still unclear. Based on the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) ocean numerical model, three bottom friction parameterization schemes (BFPSs) were compared, namely the Adjoint Data Assimilation (ADA), Manning Depth-dependent Formula (MDF), and Constant. This research finds that the ADA scheme performed best in tidal simulation. The error of elevation is less than 8.48 cm. Based on the simulation results of the ADA scheme, the tidal dynamic characteristics and bottom frictional dissipation surrounding Taiwan Island were systematically analyzed. Results show that the amplitude peaks of the semidiurnal tides are located in the vicinity of 25°N, 119°E. A densely-packed zone of isophase lines and a zero-ellipticity demarcation line were observed at 23.5°N. Regarding the diurnal tides, the amplitudes exhibit an increasing trend from the southeast towards the northwest, and the isophase lines are orthogonal to the coastline. The frictional dissipation rate is generally high within the strait (mean of 3.1×103 W/m2). However, it is relatively low in the Penghu Channel (mean of 1.34×105 W/m2). Therefore, the tidal energy flux in the strait is concentrated at the northern and southern extremities (mean of 1.5×106 W/m) as well as in the Penghu Channel. Similar correlations between tidal energy flux and bottom frictional dissipation rate are manifested in the eastern, southern, and northern parts of Taiwan Island.Keywords：tidal simulation;tidal energy flux;bottom friction parameterization schemes (BFPSs);bottom friction dissipation;areas surrounding Taiwan Island18|39|0Updated：2026-05-07
Physics
- Abstract：More than 721 submarine hydrothermal fields have been documented globally, however, the characterization of hydrothermal systems beneath the ice-covered Arctic Ocean remains poorly constrained. During the 2021 JASMInE expedition, a 369-cm-long sediment core was recovered from the central rift valley of the Gakkel Ridge 96°E. The core is predominantly composed of terrigenous debris, Fe-(oxyhydr)oxides, volcanic glass, and hydrogenetic Mn oxides. Three hydrothermal-affected layers (HA1–HA3) within the upper 85 centimeters below seafloor (cmbsf) exhibit enrichment in Fe, Cu, Pb, P, V, Mg, Ca, and Na, associated with accumulation of Fe-(oxyhydr)oxides and volcanic glass. Among these, Layer HA2 (13–16 centimeters below seafloor (cmbsf)) displays the most intense hydrothermal signature, characterized by high concentrations of Fe (12.06–15.22 wt.%), Mn (2 687–5 465 μg/g), Cu (245–373 μg/g), and Pb (248–342 μg/g), accompanied by reduced rare earth element (REE) concentrations, and shale-normalized patterns featuring negative Ce anomalies, and positive Eu anomalies. In comparison, Layers HA1 (83–85 cmbsf) and HA3 (6–7 cmbsf) exhibit only marginally elevated concentrations of hydrothermal-related elements (Fe, Cu, Pb, P, V) compared to pelagic background sediments, indicating a weaker hydrothermal influence. Overall, the observed coarsening of volcanic glass grain size and its increased abundance within hydrothermal-affected layers, coupled with diagnostic signatures from the Al-Fe-Mg ternary diagram and the detection of hydrothermal plume anomalies along the 100°E Axial Volcanic Ridge (AVR), collectively point to a basalt-hosted hydrothermal system associated with the AVR as the source of the hydrothermal signals recorded in the core. These findings reveal the geochemical fingerprints of hydrothermal materials in Arctic deep-sea sediments, offering new insights into their sources and formation processes in the ice-covered ocean.Keywords：ice-covered ocean;hydrothermal event;sediment core;major and trace element;Gakkel Ridge17|42|0Updated：2026-05-07
Geology
- Abstract：Particulate organic carbon (POC) is a key component of marine carbon cycling. However, its spatiotemporal dynamics in the Arabian Sea remain poorly understood. We investigated the distribution, seasonal variability, and environmental drivers of POC using moderate resolution Imaging Spectroradiometer Aqua (MODIS-Aqua) satellite data (2001–2021) and vertical profiles from the Pelagic Interactions Scheme for Carbon and Ecosystem Studies (PISCES) biogeochemical reanalysis model (Copernicus Marine Services). Surface POC concentrations exhibited profound seasonal variability. Values peaked at 500 mg/m3 in coastal zones during winter (January–March) and monsoon (July–August). The highest monthly averages were recorded in February (254.8±45.5 mg/m3), January (208.36±50.2 mg/m3), and March (196.45±75.3 mg/m3). Regional analysis revealed distinct patterns: Region A (Pakistan/Iran coast) had winter maxima (504.2 mg/m3 in January); Region B (Oman) peaked during the monsoon upwelling (835.4 mg/m3 in July); Region C (India) showed moderate values (327.9 mg/m3), while Region D (open sea) exhibited stable concentrations (~114 mg/m3). All regions showed declining POC trends, with the most profound decrease in Region A (-0.28 mg/m3). Surface POC was strongly correlated with chlorophyll a (Chl a), at 0.64 in coastal and 0.69 in offshore waters. Vertical profiles revealed strong correlations (>0.8) between POC, Chl a, and sea surface temperature (SST). Weaker associations were found with nutrients (NO3, PO4), salinity, pH, and oxygen. Seasonal SST maxima (29.1±0.7 °C in May) and deep mixed layers (54.3±5.1 m in January) influenced vertical carbon fluxes. Silicate and oxygen showed depth-dependent patterns. Surface waters were depleted (<2 mmol/m3), while mesopelagic layers were enriched (20–45 mmol/m3). This study provided the first integrated satellite-model analysis of POC dynamics in the Arabian Sea. It fills a critical knowledge gap in regional carbon cycling. The findings improved the ability to predict biogeochemical responses to monsoon variability and climate-driven oceanographic shifts, and they also have important implications for global carbon budget estimates.Keywords：particulate organic carbon (POC);biogeochemical processes;chlorophyll a;climate change;Arabian Sea24|20|0Updated：2026-05-07
- Abstract：This study investigated seasonal variations in the concentrations of 16 priority polycyclic aromatic hydrocarbons (Σ16 PAHs) in surface sediments of the central Bohai Sea during spring and summer 2022, to identify the underlying driving factors of seasonal changes. Principal component and multivariate linear regression analyses revealed that the PAHs were mainly originated from pyrolytic sources. Among 23 sampling stations, only one station had PHSs that could be derived from petroleum sources. The concentrations of dissolved PAHs in various water layers and seabottom surface sediments were measured, and the results show that the concentrations of Σ16 dissolved PAHs in most stations were higher in spring than in summer. A comprehensive analysis was conducted to explore the potential factors influencing the seasonal variation of PAH concentrations in the surface sediments, suggesting that the adsorption and absorption of PAHs in water by phytoplankton indirectly affect the concentration of PAHs in sediment, and that the phenomenon of high PAH concentrations in spring and low PAH concentrations in summer is related to the re-suspension by high tidal currents and occasional strong winds in summer.Keywords：polycyclic aromatic hydrocarbons (PAHs);central Bohai Sea;sediment;dissolved PAHs;seasonal variation;phytoplankton16|17|0Updated：2026-05-07
Chemistry
- Abstract：In recent studies, the most effective method for controlling harmful algal blooms (HABs) in field applications is the modified clay (MC) technology. While the MC technology has been proved highly effective for HABs control, emerging evidence highlights its limitations, particularly in the presence of algal organic matter (AOM) where the algal removal efficiency of MC can be significantly reduced. We compared the physicochemical properties of AOM derived from two dinoflagellate species, Prorocentrum donghaiense (also identified as Prorocentrum shikokuense Hada and Prorocentrum obtusidens Schiller) and Amphidinium carterae, and their effects on the MC flocculation of microalgae cells. The physicochemical properties of AOM in microalgal culture fluid can differ with species and growth phase. Various AOM samples had different effects on MC flocculation; for example, AOM derived from P. donghaiense in the exponential growth phase inhibited flocculation, while AOM derived from A. carterae in the exponential growth and stationary phases accelerated flocculation. The effect of AOM on MC flocculation was attributed to a combination of multiple mechanisms, with individual AOM properties displaying inconsistent effects under different sets of conditions. Notably, the ratio of the molecular weight to the electric charge (M/E) of the AOM can indicate how the AOM will affect the algae removal efficiency of MC: the larger the ratio is, the greater the promoting effect is likely to be, and vice versa.Keywords：harmful algal bloom (HAB);algal organic matter (AOM);modified clay (MC);molecular weight;electrical property92|28|0Updated：2026-05-07
- Abstract：This study is the first to explore the linkages among sediment dinocysts, their free-living forms, and environmental factors in a tropical marine setting. Here, we surveyed dinocyst composition and abundance and compared them with free-living dinoflagellates at 48 stations in five harmful algal bloom (HAB)-affected bays on three eastern islands of the Philippines bordering the western side of the Pacific Ocean. Through traditional light microscopy, we were able to confirm 18 dinocysts in the five bays, including those producing yessotoxins (YTX), paralytic shellfish poisoning (PSP) toxin, and those associated with ichthyotoxicity. Dinocyst composition in the bottom of each bay resembled the free-living dinoflagellates in the waters, with Samar Sea showing more uniformity than Leyte waters. Moreover, we observed an inverse relationship between Pyrodinium and Lingulodinium based on their abundance, suggesting a possible ecological preference or encystment potential of the free-living form. We notably observed an unusually high abundance of Pseudocochlodinium profundisulcus (3 000 cysts/g DS) on the western side of Biliran Bay, despite the absence of its free-living form during the sampling period. Multivariate analysis showed that dinocysts distribution and abundance in the eastern islands correlate with available phosphorus, organic matter, moisture content, and muddy type of sediment. Observations of the dinocyst-phytoplankton linkage in the field are important for understanding the ecology and biology of dinoflagellates. This will further our understanding and, hopefully, predict or mitigate HAB.Keywords：harmful algal bloom (HAB);dinoflagellate cyst;Pyrodinium;Pseudocochlodinium profundisulcus;dinoflagellate ecology97|9|0Updated：2026-05-07
- Abstract：Mobility is critical for the survival of flagellated microalgae and plays a key role in maintaining marine ecosystem stability. To assess the environmental risks posed by polylactic acid microplastics (PLA-MPs), we investigated their effects on the photosynthesis and motility of Microglena sp. through indoor and outdoor mesocosm experiments at concentrations of 10, 25, 50, 75, 225, and 375 particles/mL. Results reveal that PLA-MPs inhibited the growth of Microglena sp. in a dose-dependent manner, with a maximum inhibition rate of 44.07% at 375 particles/mL. Additionally, PLA-MPs disrupted photosynthetic activity, chlorophyll biosynthesis, and induced oxidative stress. The swimming velocity and motility patterns of Microglena sp. were also significantly affected. Transcriptomic analysis demonstrated that down-regulation of flagella-related genes contributed to reduced motility, while suppressed photosynthetic gene expression corresponded to decreased photosynthetic efficiency. These findings enhanced our understanding of the adverse effects of PLA-MPs on microalgae and provide valuable insights for evaluating the ecological risks of PLA-MPs in marine ecosystem.Keywords：polylactic acid (PLA);microplastic (MP);Microglena sp.;photosynthethesis;motility100|20|0Updated：2026-05-07
- Abstract：Biogeomorphic features are common in mangrove ecosystems worldwide, particularly crab burrows, which play a vital role in shaping regional material cycling processes. This study provides new insights into the distribution and indicators of microplastics in mangrove sediments by examining the role of biogeomorphology, specifically by investigating the distribution of crab burrows and microplastic pollution in the Jiulong River estuary, China. Results show that the abundance of microplastics in the sediments of mangroves in Jiulong River estuary was 286.45±18.98 items/kg (mean±SE). The microplastic distribution showed seasonal variations, with no significant differences among burrow treatments in rainy season but marked differences in dry season (P=0.037; F=3.403). There were significantly fewer microplastics in large burrows than in small burrows, with both burrow types showing substantially lower abundance than non-burrow sediments, especially for particles >500 μm in size. Vertical stratification was observed in dry season only during which microplastic level was lower in deeper sediment layers than in the surface layers of the burrows. Pearson’s coefficients highlighted significant correlations between crab burrow density and microplastic abundance in the sampling plots. The crab burrow area index (Sburrow) was used to reflect the area occupied by crab burrows, and we found that the index exhibited a highly significant correlation with microplastic abundance (P<0.001; R=0.997). Overall, the specific effects of crab burrows on the distribution of microplastics were highly variable and shaped by the interplay of hydrodynamic conditions, sedimentary environment stability, and burrow characteristics over time and space. Therefore, crab burrows can be used potentially to characterize the microplastic pollution level in mangrove ecosystems. We recommend to incorporate this biomonitoring method into existing coastal environmental assessment framework.Keywords：microplastics;biogeomorphology;mangrove;crab burrow;Jiulong River estuary112|22|0Updated：2026-05-07
- Abstract：Weizhou Island is the largest and youngest volcanic island in China, and has a great variety of marine organisms. However, the composition and distribution of its oysters are less known. To determine the diversity and distribution of oysters from Weizhou Island, 308 individuals were collected from 10 intertidal and 10 subtidal sites. All the samples were identified based on their morphological characteristics and mitochondrial 16S rRNA gene sequences. Our results indicate 13 Ostreoidea species from five genera existed on Weizhou Island. Among them, eight species were distributed in the intertidal zone (Crassostrea sikamea, C. gigas angulata, Saccostrea echinata, S. malabonensis, S. circumsuta, S. mordax, S. spathulata, and Dendostrea folium) and six species were distributed in subtidal zone (Hyotissa hyotis, H. sinensis, H. inaequivalvis, Hyotissa sp., Booneostrea subucula, and Dendostrea folium). Of these, S. spathulata was a new record species in China. An unassigned species belonged to the genus Hyotissa Stenzel, 1971 and was closely related to H. inaequivalvis. Weizhou Island exhibites high species-level oyster diversity. The dominant species in the intertidal zone was S. echinata, which accounted for 51% of the total species in intertidal samples. The dominant species in subtidal zone was H. inaequivalvis, accounted for 58% of the species found in subtidal zone. Our results provide a scientific basis for the reasonable development and management of oyster resources in the Weizhou Island, China.Keywords：Weizhou Island;Ostreoidea;diversity and distribution;taxonomy;16s rRNA17|22|0Updated：2026-05-07
Ecology
- Abstract：The development of microfluidic-based Raman devices has enabled the acquisition of thousands of single-cell Raman spectra from complex microbial populations, offering new avenues for characterizing environmental bacteria. We proposed and validated the convolutional deep embedded clustering (CDEC) model, a clustering framework designed for the unsupervised classification of marine microbial Raman spectra. A four-stage analytical framework was employed to systematically assess the performance of the CDEC model, with increasing dataset complexity ranging from mock communities of pure bacterial cultures to natural microbial populations isolated from seawater. The CDEC algorithm consistently distinguished bacterial species across all stages, achieving an average accuracy of 97.27%, and surpassed the baseline methods in performance. In natural microbial communities, the model resolved eight distinct clusters with unique Raman spectral markers, revealing underlying metabolic heterogeneity. These results highlight the scalability and utility of the CDEC model for studying marine microbial diversity and characterizing microbial composition and metabolic traits at single-cell resolution.Keywords：marine microbe;Raman spectroscopy;deep clustering;convolutional network144|30|0Updated：2026-05-07
- Abstract：Three photosystem I (PSⅠ) particles associated with different amounts of light-harvesting complex I (LHCI) were isolated from a phycocyanin 645 (PC645)-containing cryptophyte Chroomonas placoidea by Triton X-100 sucrose gradient centrifugation. Two active PSⅠ-LHCⅠ particles (Bands 4 and 5) were resolved from thylakoids stripped of cations only, which implied that LHC migration and the adjustment of energy distribution between photosystem II (PSⅡ) and PSⅠ facilitated by cations could also occur in cryptophytes, like in higher plants. Peptide analysis revealed that 19.8-, 10-, and 8.3-kDa peptides corresponding to β, α1, and α2 subunits of PC645, respectively, were present in Bands 4 and 5. Analyses of fluorescence and circular dichroism spectra and Gauss analyses revealed efficient energy couplings between PC645 and chlorophyll within both of these PSⅠ-LHCⅠ particles. The excitation energy absorbed by PC645 could be directly transferred to chlorophyll a in the PSⅠ core or via the chlorophyll a/c-protein complex of LHCⅠ. Based on these observations, we designated the two PSⅠ-LHCⅠ particles as phycocyanin-PSⅠ complexes, which have not been reported previously. Band 4-2 was a sub-complex of Band 4 and was almost depleted of LHCⅠ (the chlorophyll a/c-protein complex was designated as Band 4-1) and PC645. Therefore, Band 4-2 was recognized as the PSⅠ core complex. Negative staining and transmission electron microscopy images of Band 4 gave a direct view that the PC645 component attached with chlorophyll-protein complexes in a regular structure as hollow ring shape. Furthermore, while previous studies have indicated that PC645 associates with PSⅡ, our results reveal that, in this cryptophytic alga, PC645 exhibits structural—but not preferential—association with PSⅠ, which provided new information about the architecture and function of the energy transfer system comprising phycobiliproteins and chlorophyll-protein complexes in cryptophytes.Keywords：cryptophyte;phycocyanin-photosystem I (PSⅠ) complex;sub-complex;light-harvesting complex (LHCI);microstructure16|23|0Updated：2026-05-07
- Abstract：To minimize the high energy cost of biomass production in the large-scale production of Phaeodactylum tricornutum, the diatom was cultured outdoor under solar light. The damage caused by outdoor high-light stress to the photosynthetic apparatus is a major threat to the productivity of P. tricornutum. We demonstrated that the addition of alginate-derived oligosaccharides (ADOs) could significantly enhance the high-light resistance of photosystem II (PSII) in P. tricornutum. The ADOs decreased PSII photoinhibition and increased the electron transport rate under high light. The beneficial impact of the ADOs in reducing light inhibition was more noticeable under increased light intensities. This positive effect was attributed to two factors. The first: the ADOs lowered the capability for absorbing light energy in the PSII reaction centers, protecting PSII from excess light energy under high light. The second: the ADOs enhanced the activity of antioxidant enzymes (APX and SOD), reducing the over-accumulation of reactive oxygen species (ROS, i.e., H2O2), which further decreased the ROS-induced net degradation of D1 protein, ensuring the smooth photosynthetic electron transport of PSII under high light. Given the enhancement of high-light resistance in P. tricornutum, ADOs could serve as a protectant, which can be applied for large-scale production of P. tricornutum under outdoor culture conditions.Keywords：Phaeodactylum tricornutum;high-light stress;alginate-derived oligosaccharide (ADO);photosystem II (PSII);photosynthetic electron transport15|12|0Updated：2026-05-07
- Abstract：The effects and mechanism of NaAc addition and supply modes growth in both green and red stages of Haematococcus pluvialis were investigated, and 1-g/L NaAc was found the optimal initial concentration for the two stages. On this basis, the extra supplement of 1-g/L NaAc on Day 6 of the green stage or on Day 3 of the red stage could further increase the accumulation of biomass. Compared with autotrophic control, the optimal NaAc supply mode increased the dry weight by 135.71% (green stage) and 91.11% (red stage), while astaxanthin and lipid were increased by 56.9% and 42.86% in red stage, respectively. Gene expression detection revealed that acetyl-CoA synthetase (acs) acs2, acs3, and acs5 were primarily responsible for the NaAc uptake during the green stage, and acs4 played a critical role in stress response during the red stage, additionally, key genes associated with acetate metabolism, astaxanthin synthesis, and lipid synthesis, were significantly upregulated under optimal NaAc supply mode. The findings provide practical and theoretical insights for NaAc use in Haematococcus pluvialis.Keywords：Haematococcus pluvialis;acetate supply mode;acetate metabolism;astaxanthin;lipid34|11|0Updated：2026-05-07
- Abstract：Starfish are usually apex predators in marine benthic ecosystems, given that they have spines and use their secondary metabolites to defend against predators. Crude extracts of starfish have demonstrated their chemical defense function. However, the specific molecules utilized by starfish for chemical defense remain unknown. In this paper, we used a variety of chromatographic methods to systematically separate the secondary metabolites of starfish Asterias amurensis. The structures of the compounds were unambiguously solved by detailed nuclear magnetic resonance spectroscopy (NMR), mass spectra analysis, and time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations. Three new compounds, 3β,6α,12α-trihydroxyl-5α-pregn-9(11)-en-3-O-sulfate sodium salt (1), 5α-pregn-9(11)-en-12,20-dione-3β,6α-diol-3-O-sulfate sodium salt (2), and 6α-[O-β-D-quinovopyranosyl-(1→2)-β-D-xylopyranosyl-(1→3)-β-D-quinovopyranosyl]-5α-pregn-9(11)-en-20-one-3β-O-sulfate sodium salt (7), together with four known asterosaponins (3–6), were identified from the n-butanol extract of A. amurensis. A systematic assessment of the embryonic toxicity of the identified compounds was conducted using the model animal marine medaka (Oryzias melastigma). The findings suggest that compounds 1–7 exhibited no embryonic lethality. Compound 7 exhibits significant teratogenicity and has adverse effects on both cardiac function and voluntary movement. Integral analysis indicates that saponins and compounds containing sulphate groups have the potential to induce birth defects in embryos.Keywords：asterosaponin;steroid;embryonic toxicity;chemical defense;Oryzias melastigma19|7|0Updated：2026-05-07
- Abstract：Sympatric species coexisting in the same geographic region and habitat offer a unique opportunity to enhance our understanding of the effects of shared historical events on species evolution and distribution. We compared the phylogeographic patterns of two sympatric clams, Indoaustriella scarlatoi and Rugalucina vietnamica, by analyzing the spatial genetic diversity of these species focusing on variations in the mitochondrial cytochrome oxidase Ⅰ (COⅠ), 16S rRNA, and 12S rRNA genes. We observed significant isolation-by-distance (IBD) effects on the two clams in South China. Tajima’s D and Fu’s Fs tests yielded negative and significant values and the mismatch distributions exhibited unimodal shapes, indicating sudden population expansion events for both species. Bayesian skyline analyses further support these conclusions. Our findings suggest that both species respond consistently to the same geographical and historical environments. R. vietnamica exhibited relatively shallow genetic differentiation, while I. scarlatoi showed a greater divergence between groups on either side of the Qiongzhou Strait, indicating a more complex genetic structure. We believe that the distinct phylogeographic structures of sympatric species are resulted from the combined effects of microhabitat differentiation and dispersal capability.Keywords：comparative phylogeography;genetic differentiation;population structure;connectivity;sympatric distribution;Lucinidae26|16|0Updated：2026-05-07
- Abstract：In China, about 20 Nerita species have been reported, primarily from Taiwan coast and the South China Sea. However, only 8 Nerita species have been documented in the South China Sea according to past reports, indicating a significant discrepancy between the literature and the actual presence and distribution of these species in these waters. Based on the material historically deposited in Marine Biodiversity Collection of South China Sea (SCSMBC) in Guangzhou and the Marine Biological Museum of Chinese Academy of Sciences (MBMCAS), Qingdao, as well as specimens obtained from investigations in the South China Sea over the past few years, the present paper reports 18 Nerita species from the South China Sea, including one new recorded species: Nerita essingtoni Récluz, 1842; provides taxonomic information, habitat, distribution, and faunal formation data for these species; reports new distributions for three Nerita species in the South China Sea: Nerita argus Récluz, 1841, Nerita signata Lamarck, 1822, and Nerita ocellata Leguillou, 1841. The paper straightforwardly distinguishes among three species complexes using shell characteristics: Nerita undata complex (four species), Nerita histrio complex (three species), and Nerita incerta complex (five species), with keys provided in tabular form. Distribution and habitat notes for each species are based on verified historical collection records, personal collecting and observation, and reliable literature records. This report is part of ongoing work to revise and document the Neritidae of China Seas to understand the resources and conservation of neritids in China.Keywords：Neritidae;Nerita;South China Sea;new recorded species;distribution19|10|103Updated：2026-05-07
- Abstract：Eight species of the genus Gogorevia (Bacillariophyta) are reported from across China, of which five have been previously described and three of them, namely Gogorevia ellipticum sp. nov., Gogorevia rectangularis sp. nov., and Gogorevia subconstricta sp. nov., are new to science. The three new species are descripted in morphology with light and scanning electron microscope and compared with other closely related species of Gogorevia. Specifically, G. ellipticum sp. nov. has an elliptical valve with subrostrate or capitate apices. G. rectangularis sp. nov. has an elongated and rectangular valve with rostrate apices, parallel and slightly constricted at the center margins. G. subconstricta sp. nov. has a linear-elliptical valve with clearly undulate margins that are constricted in the center, protracted and distinctly capitate apices. This study enriched our knowledge on the species diversity and geographical distribution of Gogorevia in the world.Keywords：diatom;Gogorevia;new species;taxonomy;China17|24|0Updated：2026-05-07
- Abstract：Two filamentous cyanobacteria, isolated from different habitats in Yunnan Province, China, were described. Phylogenetic analysis and taxonomic identification were performed using a polyphasic approach that included morphological, ecological, and molecular data. Their morphological characteristics and microscopic structures were observed and recorded using an optical microscope. Filaments of the strain SXACC0113 are yellowish-green and relatively wide, ranging from 1.1 to 4.8 μm, and the cells are sometimes inflated. Strain SXACC0116 have no false branching, and the apical cells are cylindrical. Phylogenetic trees were constructed using maximum likelihood (ML) and bayesian inference (BI) based on the 16S rRNA gene sequences. The analysis showed that the algal strain SXACC0113 was distributed in the Elainella clade, and its similarity to the 16S rRNA genes of other species in the genus Elainella was 97.9%–98.2%. The strain SXACC0116 was distributed in the Pegethrix clade, and its similarity to the 16S rRNA genes of other species in the genus Pegethrix was 95.4%–97.3%. Additionally, unique forms were found in the D1-D1ʹ, Box B, and V3 helices of the 16S–23S internal transcribed spacer (ITS) secondary structure in these strains. These findings support the establishment of two new species, named Elainella yunnanensis sp. nov. and Pegethrix yunnanensis sp. nov. This discovery increases the diversity of cyanobacterial species in China, provides a scientific basis for further revision and classification of cyanobacteria, and supplements algae research information in China.Keywords：Elainella;Pegethrix;Oculatellaceae;new species;polyphasic approach;phylogeny21|12|103Updated：2026-05-07
- Abstract：Microevolution of commonly used model bacterial strains may lead to inconsistent genetic analysis results across laboratories. To address this issue, it is helpful to introduce a verification strain that belongs to the same species as the model strain. Anabaena sp. PCC 7120 is the model cyanobacterial strain for studies of heterocyst differentiation, and inconsistent results produced with different substrains have been reported. Novel Anabaena isolates outside PCC 7120 and derivatives are needed for verification on analysis results. We report that two Anabaena strains independently isolated from natural environments, FACHB-595 and FACHB-709, are nearly identical to Anabaena sp. PCC 7120 in genome sequence (hundreds of SNPs, indels, insertions/deletions), except for the changes in two of the six plasmids in one of the strains. We deleted genes involved in heterocyst differentiation and pattern formation—including hetR, hetZ, hetP, hetC, patS, patU3, patX, patL, and patA—in the two new strains and observed phenotypes consistent with previous reports; in mutants of nrrA or patN, however, we found accelerated or delayed heterocyst formation compared to the reports. Therefore, both FACHB-595 and FACHB-709 can serve as strains to verify the genetic analyses conducted using Anabaena sp. PCC 7120.Keywords：natural sibling strain;Anabaena sp. PCC 7120;comparative genome analysis;deletion mutant;heterocyst differentiation51|9|0Updated：2026-05-07
Biology
- Abstract：Currently, nitrates are the most commonly used nitrogen source for microalgal cultivation, but most of them are explosive chemicals, posing safety risks and their use is restricted. Therefore, microalgae producers urgently need to find safer and more economical alternatives. This work systematically investigated the development of novel culture medium to improve safety and reduce costs during microalgal cultivation. Urea was screened out as the best nitrogen source, and the optimum nitrogen concentration was 265 mg/L. When waste shells were used as pH stabilizer and carbon supplement, the biomass and biomass productivity were increased to 1.26 g/L and 71.59 mg/(L·d), respectively. Pilot-scale cultivation was carried out in 50-L flat plate photobioreactors, and the Logistic model fitted the growth curves well. Notably, economic analysis showed the new medium could save 29.09%–32.76% of the input cost. This work provided a new alternative culture medium for the large-scale culture of Haematococcus pluvialis.Keywords：economic evaluation;growth kinetics;Haematococcus pluvialis;microalgal culture medium;pilot-scale cultivation10|10|0Updated：2026-05-07
- Abstract：White spot syndrome virus (WSSV) is one of the most virulent pathogens in shrimp aquaculture. An in-depth understanding of the surface protein-protein interplays between WSSV and host is the key to further elucidating the pathogenesis mechanism. In this study, VP39A was identified as a novel cellular binding protein of WSSV by reversely conducting the biotinylation based affinity chromatography (BBAC) method. The result of indirect immunofluorescence assay, competitive ELISA, and in-vivo neutralization assays show that VP39A is vital to the cellular entry and infection of WSSV. Na+, K+-ATPase alpha subunit (NKAα), a trans-membrane subunit of complex Na+, K+-ATPase, was captured as the VP39A binding protein with pull-down assay. Co-localization of NKAα with VP39A in shrimp hemocytes was confirmed by immunofluorescence and co-immunoprecipitation studies. In addition, blocking with anti-NKAα antibody can reduce the binding of WSSV to the gill cellular membrane proteins. These results collectively demonstrate that VP39A plays an important role in the viral adsorption via its interaction with NKAα, which could be an effective target for drug design.Keywords：white spot syndrome virus (WSSV);biotinylation;viral adhesion;protein-protein interaction;Na+, K+-ATPase alpha subunit61|20|0Updated：2026-05-07
- Abstract：Marine ranch is a novel paradigm in the transformation of traditional fisheries, which embodies a modern and high-tech approach to increasing marine fishery production and enables the sustainable and efficient exploitation of marine resources. After several decades of development, the industrial model of marine ranch has matured. However, in several developing countries, subsequent management and evaluation remain inadequate. In this study, the Dachen Island Marine Ranch in the East China Sea was used as a case to explore two fishery management strategies. A multi-species size spectrum model (MSSM) was established for the Dachen Island Marine Ranch to simulate fish community dynamics. While considering interspecific interactions, the effectiveness of two management strategies was assessed: (1) altering fishing mortality; and (2) increasing cod-end mesh size. The findings indicate that the change in the fishing mortality of large predators can induce trophic cascade effects, and the large predators have the greatest impact on community structure. In scenarios that simulate fishing mortality for multiple species, competition is shown between two species occupying similar ecological niches. An increase in cod-end mesh size can be observed to decrease bycatch while positively impacting community structure. Our findings suggest that fisheries management reforms should consider the effects of management changes on the entire ecosystem (including environment and biodiversity), rather than concentrating solely on the long-term yield of fish harvests. A stable ecosystem can yield more products, and long-term sustainable fishery yields are one of them.Keywords：marine ranch;size spectrum model;fishing mortality;cod-end mesh size49|10|0Updated：2026-05-07
Aquaculture and Fisheries
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