Typhoon Chaba, the fourth typhoon of 2022, exhibited an abnormal northward turn after making landfall in Guangxi on the night of July 2, resulting in significant deviations in wind and rainfall forecasts and posing major challenges to typhoon defense efforts. This study employs a comprehensive approach utilizing multi-source meteorological observation data from the upper-air, surface, and satellite platforms, along with ERA5 (the fifth generation of European Centre for Medium-range Weather Forecasts) reanalysis data of the global climate. Through synoptic diagnostic analysis and quantitative diagnosis using the potential vorticity tendency equation, we investigate the causes of the typhoon's abnormal northward turn. The results indicate that: (1) The northward turn of typhoon Chaba resulted from the combined effects of changes in the deep-layer steering flow due to large-scale circulation pattern shifts and changes in the typhoon's internal asymmetric structure; (2) The deep-layer steering flow played a dominant role in the track deflection. Key factors driving the steering flow changes included the westward extension and intensification of the Western Pacific Subtropical High, the interaction between the southwest flow ahead of the upper-level westerly trough and the northwest side of the South Asian High, and the typhoon's northward outflow. Meanwhile, changes in positive vorticity advection served as important indicators of the typhoon's northward turn; (3) Typhoon Chaba displayed distinct asymmetric structural characteristics, with cumulonimbus convection triggered by its internal vertical motion significantly influencing the northward turn. Changes in the typhoon's cloud pattern also provided valuable indications of its directional shift; (4) Quantitative diagnosis using the potential vorticity tendency equation further revealed that during its movement over the South China Sea, the typhoon was primarily controlled by the steering flow formed by the external large-scale circulation. The abrupt northward turn after landfall resulted from the combined effects of this steering flow and vertical motion induced by the typhoon's asymmetric structure. Additionally, typhoon Chaba exhibited a consistent movement tendency towards the center of positive potential vorticity tendency.

The Nansha Islands, located in the southern part of the South China Sea, hold significant strategic importance for China’s maritime rights and interests, development strategy, and national security due to its geographical location. It is of great significance to national strategy to carry out research on water depth monitoring and topographic changes of Nansha Islands and reefs. In this study, combined with Sentinel-2 and ICESat-2 (ice, cloud, land elevation satellite-2) data, an active-passive fusion remote sensing sounding algorithm was used to invert the shallow sea topography of the Bai Jiao and Beizi Dao areas in the Nansha Islands. This method enables time series analysis to reveal long-term trends and short-term fluctuations in water depth and reef terrain, providing new insights into the impacts of human activities and natural factors on reef topography changes. The research results are as follows: 1) A high-precision water depth inversion model was validated, showing excellent performance in the study area (R² > 0.9, MAE < 0.4 m, RMSE < 0.7 m). 2) From 2018 to 2024, both Bai Jiao and Beizi experienced varying degrees of terrain and spatial structure changes. Due to reclamation projects, the land area of Bai Jiao increased, whereas Beizi Dao’s changes were influenced by natural factors, exhibiting dynamic variations. 3) The topographic changes of Bai Jiao were mainly driven by human factors, including land reclamation and resource exploitation, while Beizi Dao’s changes mainly resulted from natural factors such as monsoons, typhoons, seawater erosion, and sediment deposition. This study demonstrates the effectiveness of active-passive fusion bathymetry, providing a valuable reference for efficient water depth and terrain detection of typical reefs in China. Moreover, it offers crucial technical support for long-term spatiotemporal monitoring of shallow sea terrain in areas such as the Nansha Islands.

Based on the ecological survey data of macrobenthos in the seagrass beds of Xincungang (2015−2016) and Li’angang (2017−2018) across four seasons, we compared their community structures. The results showed that: (1) A total of 96 species of macrobenthos were recorded in the seagrass beds of the two areas, with 50 species in Xincungang and 62 species in Li’angang. Both seagrass beds were dominated by annelids, and Dasybranchus caducus was a common dominant species. Except in autumn, the average density of inhabited macrobenthos in Xincungang was higher than in Li’angang, while, except in summer, the biomass in Li’angang was higher than in Xincungang. (2) The Shannon-Wiener diversity index (H′), Pielou’s evenness index (J′), and Margalef’s richness index (d) in Li’angang were all higher than those in Xincungang. The W value of the abundance/biomass curves (ABC) in Li’angang was also significantly higher than in Xincungang, indicating that the macrobenthos community structure in Li’angang’s seagrass beds was more stable and less disturbed. (3) Cluster analysis of community inhabited density and biomass revealed that the communities in the two areas could be divided into two distinct groups at a similarity level of approximately 15%, demonstrating significant differences in the macrobenthos community structure between Xincungang and Li’angang. Combined with historical research, these differences are likely attributed to variations in hydrological conditions and pollution from aquaculture activities. Compared with historical data, the macrobenthos communities in the seagrass bed protected areas of both locations have shown signs of recovery, suggesting that ongoing protection and restoration efforts are effective and necessary.

Coral sandy islands, as a typical tropical marine landform, play a significant ecological role and hold great scientific research value. However, the intensification of global climate change and human activities poses a serious threat to their stability. This study focuses on North Island, a typical coral sandy island in the Xisha Islands of the South China Sea, using multi-temporal high-resolution remote sensing imagery from 2002 to 2023 and the Digital Shoreline Analysis System (DSAS) to reveal its coastline dynamics and influencing factors. The study also proposes targeted protective measures. The results show that: 1) the coastline of North Island exhibits distinct stage characteristics. From 2002 to 2015, the coastline expanded slowly; from 2015 to 2019, due to dock construction at the southeastern end and island expansion, 57% of the coastline extended seaward through sediment deposition, with the coastline length and area sharply increasing, peaking in 2019. However, from 2019 to 2023, erosion intensified, with 47% of the coastline retreating and a total erosion area of 11846 m². The spit area, influenced by monsoons, exhibited seasonal erosion-deposition cycles (erosion during the northeast monsoon and deposition during the southwest monsoon), while the beach rock area decreased drastically due to erosion susceptibility, human activities, and natural factors, leaving only 3827 m² by 2023. 2) The evolution of coral sandy islands is fundamentally driven by the interaction between hydrodynamics and sediments, affected by both natural factors (e.g., coastal hydrodynamics, coral reef degradation, sea-level rise, extreme weather) and human disturbances. 3) This study proposes a hierarchical ecological protection system for coral sandy islands, with measures spanning from the supratidal to the subtidal zone, including vegetation-based sand fixation, mobile sand barriers, diamond-shaped sandbags, and beach rock restoration. These measures balance ecological conservation with island protection needs, providing practical and feasible recommendations for the protection and management of coral sandy islands in the South China Sea.

The Xisha Islands are located on the central route from the Hainan Island to other oceanic islands in the South China Sea (SCS). They are typical geological and geomorphological complexes formed by the coupling interaction between tectonic and biological processes. However, their exposed area is also within a typical climate-vulnerable zone of SCS, being severely influenced by extreme marine hazards, e.g., typhoons and storm surges. Coral reef coastal areas are anticipated to be broadly developed in the future, following the strategy of high-quality development of reef island resources in the Xisha Islands. With increasing risks and threats from marine environmental disasters due to global climate change, the challenges of marine hazards prevention and mitigation in the Xisha Islands are further heightened. Hence, revealing the geomorphic response of coral reef coasts to marine environments becomes a critical issue that urgently needs to be addressed. Therefore, this study employs 18 coral reefs in the Xisha Islands as their research subjects, using marine satellite remote sensing data to acquire their coastal geomorphology images in 2015 and 2023. Morphological changes of these coral reef coasts are characterized based upon marine geology and coastal geomorphology theories, while surrounding marine environmental conditions are examined using physical oceanographic analysis methods. This study attempts to link the spatial difference of coastal morphological change among reef islands to environmental conditions. Coupled analysis demonstrates only a weak correlation (R² ranging from 0.06 to 0.21) between the coastal morphological difference of these coral reefs and their regional marine environmental characteristics. Therefore, to scientifically assess the survival prospects of coral reefs in the Xisha Islands under the influence of global marine environmental changes, this work suggests the need to (1) comprehensively consider multiple marine environmental characteristics, and (2) strengthen the evaluation of their morphological evolution status, original geomorphology, sedimentary dynamics processes and the impact of marine biota of coral reefs.

To examine the effects of tourism disturbance on macrobenthic communities in the intertidal zones of Xisha Islands, this study compared the species number, species similarity index, abundance, biomass, index of relative importance, W-statistic index, and biodiversity indices between Quanfu Island, Yinyu Island, and adjacent non-tourist areas. The results revealed that: (1) natural fluctuations in macrobenthic communities were evident in Xisha’s intertidal zones, as demonstrated by background data from both tourist and non-tourist areas; (2) comprehensive difference analysis using standard values indicated that tourism disturbance imposed additional negative effects, with particularly significant effects on species number and Shannon-Wiener diversity index; (3) comparison of P-values across all tested indices confirmed a declining trend in species diversity due to tourism disturbance, suggesting that continued accumulation of such effects may lead to more severe damage to macrobenthic community in Quanfu and Yinyu Islands; and (4) proper tourism management measures showed potential protective benefits for endangered species. This study provides valuable insights for balancing tourism development and biodiversity conservation in Xisha Islands.

To distinguish related species of conasprella cones in Chinese waters, we compared the morphological differences among Conasprella orbignyi (Audouin, 1831), Conasprella ichinoseana (Kuroda, 1956), Conasprella comatosa (Pilsbry, 1904), Conasprella hopwoodi (Tomlin, 1936), Conasprella longurionis (Kiener, 1847) and Conus australis Holten, 1802. We also identified new distribution records for Conasprella hopwoodi and Conasprella longurionis in Chinese waters. Geometric morphometric methods were employed to analyze shell shape differences among these species. Principal component analysis (PCA) of shell outlines revealed distinct differences among Conasprella orbignyi, Conasprella longurionis, Conasprella hopwoodi, and Conus australis. Canonical variate analysis (CVA) demonstrated that the shell outlines effectively discriminate Conus australis and Conasprella orbignyi, with identification accuracy rates of 100.00% and 92.86%, respectively. PCA of spiral rib morphology on the body whorl of Conasprella longurionis and Conasprella hopwoodi indicated that the former exhibits a higher spire, wider body whorl, shorter base, and greater distances between spiral ribs, while the latter shows the opposite trends. CVA results indicated that body whorl landmarks effectively distinguish the two species, with accuracy rates of 87.50% for C. longurionis and 88.89% for C. hopwoodi. PCA of spire geometry revealed no significant separation between C. longurionis and C. hopwoodi, and CVA results aligned with those based on body whorl morphology. Similarly, PCA of aperture geometry showed no significant separation, and CVA yielded lower discrimination accuracy (62.50% and 77.78%, respectively), indicating that the aperture is not a reliable diagnostic feature for these species. This study provides a new supplementary method for identifying similar and easily confused species of conids.

Global coral reefs are undergoing continuous degradation, and it is universally acknowledged that alleviating local pressures stemming from regional coral reef degradation is crucial to counteracting the substantial impacts of escalating global stressors. The coral reefs of the Xisha Islands in the South China Sea, a vital component of the “Coral Triangle”, have exhibited varying degrees of degradation in recent years, as revealed by ecological monitoring. Analyzing coral reef degradation through relevant ecological indicators is vital for understanding coral reef trends and supporting restoration and management efforts. This paper, drawing upon existing surveys of Yongxing Island in the Xisha Islands, examines relevant ecological indicators such as coral coverage, replenishment, and bleaching rates. The results indicate that over the past 40 years, the scleractinian corals of Yongxing Island have undergone a phased pattern of degradation: healthy growth (1984-2006), rapid degradation (2006-2011), slow recovery (2011-2019), and renewed degradation (2019-2021). This trend follows a general pattern of “healthy growth→sharp degradation→slow recovery→renewed degradation”. The crown-of-thorns starfish emerges as the primary driver of rapid degradation, with coral diseases also playing a role during this stage. Human activities hindered the swift recovery of corals following the initial rapid degradation to a certain extent, while coral bleaching was the primary factor governing both slow recovery and later-stage renewed degradation. In comparison to the swift recovery of scleractinian corals in the Great Barrier Reef following its rapid degradation, the scleractinian corals of Yongxing Island have experienced more severe degradation, with a lower recovery rate over the past decade.

As global climate change intensifies, mangroves—a vital coastal blue carbon ecosystem—have garnered increasing attention. This study aimed to develop biomass models for juvenile mangroves and assess the carbon storage of young mangrove ecosystems in Kaozhouyang Bay. The results provide empirical methods and a scientific basis for the rapid and accurate assessment of carbon stocks in artificially planted young mangroves. The study focuses on five artificially planted juvenile mangrove species in Kaozhouyang Bay: Avicennia marina, Rhizophora stylosa, Kandelia obovata, Bruguiera gymnorhiza, and Aegiceras corniculatum. Various factors derived from basal diameter (D) and tree height (H) were used to construct optimal allometric equations between biomass and dendrometric parameters. Furthermore, the best-performing biomass models were applied to estimate vegetation carbon storage and ecosystem carbon storage in the artificially planted mangroves of Kaozhouyang Bay. The findings indicated that multivariable models generally outperformed univariable models, except for the below-ground biomass model of Aegiceras corniculatum. The optimal biomass models for Avicennia marina, Rhizophora stylosa, Bruguiera gymnorhiza, and Aegiceras corniculatum were power function models, whereas linear models best fit Kandelia obovata. The carbon density of the artificially planted young mangrove ecosystems in Kaozhouyang Bay was (91.26±17.32) Mg C·hm^-2, with a total carbon stock of approximately 35964.65 Mg C. Soil carbon constituted 78.3% to 98.5% of the total carbon stock in these ecosystems. Among the different mangrove communities, vegetation carbon density ranked as follows (from highest to lowest): Aegiceras corniculatum + Kandelia obovata communities, Rhizophora stylosa + Avicennia marina communities, Avicennia marina community, and Bruguiera gymnorhiza community. These results offer valuable insights for assessing carbon storage and guiding ecological restoration efforts in artificially planted mangroves in Guangdong Province and nationwide.

To explore the community characteristics and carbon accumulation function of mangroves under different coastal conditions in Shenzhen, we measured plant growth indices, soil organic carbon, and plant carbon content in three mangrove wetlands: Bao'an Xiwan Mangrove, Dapeng Luzui Mountain Mangrove, and Futian Mangrove National Nature Reserve. The biomass and soil carbon density of different communities were compared. The results showed that Kandelia obovata, Sonneratia caseolaris, and Sonneratia apetala were the constructive, dominant or associated species in the three mangrove communities of Shenzhen. The vegetation carbon density was highest in the K. obovata (88.03 t·hm^-2) and S. caseolaris+S. apetala (233.56 t·hm^-2) communities in the Xiwan Mangrove. The Futian Mangrove Reserve exhibited the highest soil organic carbon and soil carbon density (63.10 g·kg^-1, 134.65 t·hm^-2), though its soil water content and bulk density were significantly lower than the other two sites. The Dapeng Luzui Mangrove community showed the richest species composition and highest soil bulk density, but had relatively smaller plant height, DBH, and biomass. Among all communities, the S. apetala community displayed the greatest tree height, DBH, and vegetation carbon density, yet the lowest soil organic carbon content and soil carbon density. The soil organic carbon content in Futian’s natural K. obovata stand was higher than in other native and exotic mangroves. Among nine mangrove species, K. obovata showed the highest organic carbon content in stems, leaves, and fruits, while Acanthus ilicifolius had the lowest. In terms of carbon content in different plant organs, K. obovata and Bruguiera gymnorrhiza had the highest carbon content in fruits, whereas other mangrove species had higher carbon content in stems and leaves.

The complex salt components in seawater or other saline water may cause turbidity when measuring ammonia nitrogen by Nessler’s reagent colorimetric method. In this study, interference from Ca, Mg, Fe, Mn and other ions in seawater was eliminated by precisely matching sample salinity with the dosage of potassium sodium tartrate as a masking agent. The Nessler reagent spectrophotometery for rapid ammonia nitrogen determination was thus optimized. The results indicate that 1% potassium sodium tartrate solution is suitable for ammonia nitrogen determination in samples with salinity below 17.3‰, while 2% potassium sodium tartrate solution can be used for samples with salinity ranging from 4.5‰ to 34.1‰ under experimental conditions. The method’s detection range was 0.1-8.0 mg·L^-1, with a detection limit of 0.03 mg·L^-1. The spiked recovery rates of samples ranged from 96% to 105%, and the standard deviation of parallel samples was less than 3.94%. The method offers simple operation, a wide linear range, good sensitivity and accuracy, and broad applicability.

Carbon participates in the global carbon cycle in various forms in the ocean, with total organic carbon (TOC) buried in marine sediments playing a crucial role. As a transition zone characterized by high physical energy and productivity, marginal seas store more than 80% of the organic carbon in the global ocean. Covering a total area of about 4.7 million square kilometers, China’s marginal seas possess significant carbon storage capacity and potential. With the implementation of China’s “Dual Carbon” initiative, research on marine carbon storage has become a prominent topic in recent years. This review summarizes the distribution characteristics of organic carbon in the sediments of China’s marginal seas, revealing a decreasing tendency from the Bohai Sea to the South China Sea. Notably, organic carbon content in coastal waters and near estuaries is significantly higher than in the deep sea. In addition, the main sources, influencing factors, and storage potential of organic carbon are analyzed. Moreover, the review provides an outlook on potential future research directions, aiming to offer insights for the related work on marine carbon storage and the carbon cycle in China’s marginal seas.

Traditional eddy detection methods based on SAR data require manual threshold setting and feature parameter tuning, making processes complex and difficult to automate. Existing deep learning models also suffer from high rates of false negatives and false positives, failing to meet the accuracy and efficiency requirements of eddy detection. To address these issues, this paper proposes an improved model based on YOLOv8 (you only look once version 8), named EddyDetNet, to overcome the above limitations and enhance both detection accuracy and efficiency. This model introduces an adaptive feature compression module (AFCM) and a multi-scale feature spatial pyramid module (MFSP) in Backbone and Neck, optimizes the Neck structure, and adds a small target detection head in the Head part, thereby improving the detection accuracy of vortices of different scales. Experimental results show that EddyDetNet outperforms YOLOv8 by 2.4%, 3.2%, and 5.5% in precision (p), recall (r), and mean Average Precision (mAP), respectively, while reducing parameter size and computational complexity by 38.1% and 15.8%. Compared to YOLOv8, EddyDetNet reduces computational complexity and parameter size while maintaining high detection accuracy, making it suitable for eddy detection tasks in multi-target and complex background scenarios.

Estuarine and coastal waters, serving as critical interfaces between terrestrial and marine ecosystems, play a pivotal role in the biogeochemical cycling of nitrous oxide (N₂O), a potent greenhouse gas with significant impacts on global climate change. This review synthesizes current knowledge on the distribution patterns of N₂O in estuarine and coastal regions, the key microbial metabolic pathways driving N₂O emissions—including nitrification, nitrifier denitrification, incomplete denitrification, and coupled nitrification-denitrification—as well as the methodologies for quantifying N₂O production and consumption. Additionally, we examine the environmental factors influencing N₂O emissions. A deeper understanding of N₂O biogeochemical cycling in these waters is crucial for developing effective strategies to mitigate N₂O emissions and their contribution to global warming.

As one of the important environmental variables in the atmosphere-ocean system, sea surface temperature (SST) is of significant importance for oceanographic research. This paper utilizes domestic HaiYang (HY) and FengYun (FY) satellites remote sensing SST data to develop an autonomous, high spatiotemporal resolution satellite SST fusion product for the “Maritime Silk Road” region using the successive corrections method. First, the accuracy of SST observation data from HY and FY satellites was evaluated using iQuam in-situ data, with bias correction performed on HY-1C and HY-1D. Next, SST data from HY-1C, HY-1D, HY-2B, FY-3D, FY-3E, and FY-4B, along with a multi-scale successive corrections fusion algorithm, were used to create a daily 0.1°×0.1° resolution SST fusion product for the “Maritime Silk Road” region from April to June 2024. Finally, the accuracy of the fusion product was assessed using iQuam in-situ data. The results showed that the fusion product had an average bias of 0.08°C and a root mean square error (RMSE) of 0.67°C, indicating good accuracy. Power spectral analysis of different SST fusion products demonstrated that the SST fusion product generated in this study outperforms the Optimum Interpolation Sea Surface Temperature (OISST) in capturing small-scale features at the 100 km scale and shows comparable performance to the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) at the 50-100 km scale, reflecting its good application potential.

This study predicted the potential distribution of Trichiurus japonicus along China’s coastal waters under the influence of global climate change, using the maximum entropy (MaxEnt) model integrated with Geographic Information System (GIS) techniques. Species occurrence data (70 valid points) were obtained from Global Biodiversity Information Facility (GBIF) and FishBase, while environmental variables were sourced from Bio-ORACLE. Model performance was evaluated using the Receiver Operating Characteristic (ROC) curve, yielding a high accuracy (0.913) of Area Under the Curve (AUC). Our results indicated that suitable habitats for T. japonicus are distributed across China’s four major marine regions, with medium-to-high suitability areas accounting for 11.96% of the total predicted area. Temperature, chlorophyll concentration, and primary productivity were identified as key environmental factors affecting hairtail distribution. Model projections under different shared socioeconomic pathway (SSP) scenarios suggested an expansion of suitable habitats with a potential northward shift towards the Yellow Sea and Bohai Sea, while contracting in the waters of South China such as Beibu Gulf in the future.

The northeastern Indian Ocean Ridge area along the 90°E meridian exhibits complex and unique topographic features. To gain deeper insights into the benthic ecological characteristics, regional biological productivity, and terrigenous input influences across different parts of the ridge, a comprehensive identification and statistical analysis of benthic foraminifera (> 150 μm) was conducted on 13 surface sediment samples from this region. The study revealed that benthic foraminifera in the 150-250 μm size fraction dominated the area, with relative abundances of 60% to 84%, while the fraction larger than 250 μm exhibited lower relative abundances of 16% to 40%. The dominant benthic foraminiferal species were primarily epifaunal and shallow infaunal types. Among the three major benthic foraminiferal shell types, hyaline shells predominated, followed by agglutinated shells, with porcellaneous shells being the least abundant. Although no significant differences in dominant species were observed among stations, distinct regional variations emerged in shell-type proportions and epifaunal or infaunal distributions: the abundance of benthic foraminifera is relatively high on both sides of the northern ridge and relatively low on the ridge itself; the relative content of agglutinated benthic foraminifera is significantly higher in the northeastern side of the study area compared to other areas, and increases with water depth in the central part of the Indian Ocean Ridge. The particles selected for the construction of the shell walls of agglutinated benthic foraminifera are mainly composed of detrital minerals in the northeast, while multi-species planktic foraminifera have been used to build their tests in the central part of the Indian Ocean Ridge. Analysis suggests that benthic foraminifera in the northeast Indian Ocean Ridge area are mainly influenced by the transport of terrestrial materials, surface productivity distribution, and dissolution caused by changes in water depth. In addition, we note for the first time that the content of surface species is much higher than that of epifaunal species in the components larger than 250 μm. We believe this is the result of the adaptive evolution of benthic foraminifera to high-oxygen ecological environments.

The Indian Ocean Dipole (IOD) is an intrinsic climate mode in the Indian Ocean, typically occurring during the boreal fall, influencing weather and climate in surrounding regions and even China. The IOD is affected by both the El Niño-Southern Oscillation (ENSO) and internal variability within the Indian Ocean. However, the quantitative contributions of two types of ENSO, namely the eastern Pacific (EP) and the central Pacific (CP), and internal variability to the IOD remain unclear. Here, a binary combined linear regression method is used to separate and estimate the contributions of these three factors. The results show that internal variability is the primary source of IOD sea surface temperature (SST) changes, accounting for more than 60% of the variance. The contribution of ENSO is about one-third, predominantly driven by the CP ENSO, whereas the EP type tends to exert a stronger influence on the IOD during extreme events. Their influencing mechanisms are different: ENSO affects the Indian Ocean wind field primarily via the Walker circulation, with the efficiency depending on the location of the warming cores (EP vs. CP). In comparison, internal variability tends to induce SST anomalies through oceanic processes within the Indian Ocean, facilitating IOD development. Due to the longer lifetime of El Niño events, a co-occurring positive IOD has a higher chance of transforming into an Indian Ocean basin-wide warming event in the following spring, for which ENSO contributes more than 70% of the transition. Although internal variability does not show a significant statistical relationship with this transition, a strong positive IOD still has the potential to induce subsequent basin-wide warming. These findings improve our understanding of climate modes and inter-basin interactions.

The onshore Cenozoic basins of the southern margin of the South China Block (SCB) commonly exhibit an unconformity between the Paleogene and Quaternary systems. Restoration of the erosion at this unconformity provides critical constraints for reconstructing the complete Cenozoic tectonic evolution of the southern margin of the SCB. This study focuses on the Nanxiong Basin, employing vitrinite reflectance as a paleothermal indicator to restore the erosion thickness of the unconformity between the Guchengcun Formation (top age ~56 Ma) and overlying Quaternary strata. The onset time of erosion was constrained by integrating low-temperature thermochronology data from the basin periphery. Results show that the erosion thickness of Paleogene top strata is approximately (2700 ± 300) m in the Nanxiong Basin, with the erosion starting from the Early Oligocene and lasting until the Early Quaternary. This strong erosion caused the highly mature source rocks to be denudated to shallow burial depths. Analysis reveals that the basin faulting development did not end after the depositional period of Guchengcun Formation in Nanxiong Basin but continued until the early Oligocene. Subsequently, the tectonic environment changed from extension to compression, leading to basin uplift and erosion until the early Quaternary. This intense erosion removed the sedimentary record of the late Paleocene − early Oligocene. The erosion process of the southern margin of the SCB since the late Paleogene was affected by combined effects of southeast extrusion from the Indo-Eurasian plate collision and subduction of the Pacific plate underneath the Eurasia plate. The uplift amplitude tended to decrease gradually from inland to coastal areas, resulting in differential evolution between onshore uplift and offshore subsidence.

The construction of offshore wind power platforms urgently requires seabed geotechnical data to enhance the efficiency and accuracy of geological parameter prediction and modeling. Cone Penetration Testing (CPT) data offers unique advantages and plays a crucial role in geological parameter modeling for offshore wind farms. Traditional CPT-based prediction methods mainly utilize techniques such as Bayesian and Kriging interpolation. This study introduces Support Vector Regression (SVR), Random Forest (RF), and Neural Network (NN) algorithms into geological parameter prediction, combining the spatial continuity advantage of 2D seismic data with the vertical resolution advantage of CPT data to predict and model the CPT geotechnical parameters in shallow strata at the Eastern Offshore Wind Farm site in the Yinggehai Basin, South China Sea. The accuracy of the three methods is evaluated using error histograms and validation scatter plots. Results indicate that the Neural Network delivers the best overall performance, while the Support Vector Regression model yields simpler predictions. Due to the truncation nature of the Random Forest method, it yields the least accurate results, exhibiting abrupt horizontal variations. This study presents a novel research approach for predicting seabed geotechnical parameters.

To explore the factors influencing the population dynamics of macroalgae and benthic fauna in the marine area surrounding Lvhua Island, this study conducted field ecological surveys employing the index of relative importance (IRI), biodiversity indices, and canonical correspondence analysis (CCA). These methods were applied across three macroalgal growth stages in the algal beds: seedling (August-September 2021), growth (November-December 2021), and flourishing (May-June 2022), to analyze the community composition, biodiversity, and environmental factors associated to macrobenthic population changes in Lvhua Island and its adjacent waters. The results revealed the following: (1) A total of 113 macrobenthic species were identified in the algal beds of Lvhua Island and its neighboring waters, including 49 species of benthic fauna and 64 macroalgal species, belonging to nine phyla. Among them, Mollusca and Rhodophyta had the highest number of species, with Rhodophyta dominating species diversity across all observed periods. The dominant species included Sargassum vachellianum, Sargassum horneri, Chlorostoma rustica, and Anthocidaris crassispina. The average abundance of the nine phyla across the three growth stages was 30 ind·m^-2, and the average biomass was 23.83 g·m^-2. (2) Species richness varied by growth stage, peaking during the seedling stage. Abundance and biomass fluctuations were closely tied to periodic water temperature changes, with abundance ranked as seedling stage (36 ind·m^-2) > flourishing stage (30 ind·m^-2) > growth stage (23 ind·m^-2), and biomass following a similar trend: seedling stage (25.40 g·m^-2) > flourishing stage (23.88 g·m^-2) > growth stage (22.20 g·m^-2). Principal coordinates analysis (PCoA) indicated significant differences in macrobenthic community structure across different growth stages (P<0.05). (3) The Mentoushan station recorded the highest species richness, abundance, biomass, and biodiversity, while Menduishan station exhibited the lowest diversity, and the Xilvhua station had the fewest species. Dominant and important species showed minimal variation at Donglvhua South station, where both biomass and abundance were lowest, whereas the mussel farming area displayed relatively low overlap between dominant and important species. (4) Except for salinity, water temperature (P=0.009), pH (P=0.001), and dissolved oxygen (P=0.002) significantly influenced macrobenthic distribution in Lvhua Island waters, while salinity (P=0.149) had no significant effect. Organismal adaptability to environmental factors varied by station: Mentoushan and Menduishan stations showed positive correlations with all four environmental factors, whereas Yibeidi, Xilvhua, and Donglvhua North stations exhibited negative correlations. Among the nine phyla, Phaeophyta correlated negatively with all environmental factors, while Cnidaria showed a positive correlation with salinity. This study enhances understanding of the regulatory role of macrobenthic organisms in algal bed ecosystems and provides a scientific foundation for biological resource conservation, algal bed construction, and ecological restoration in the study area.

Zhanjiang, located in the South China Sea, is rich in seaweed resources. To clarify the species diversity of the genus Gracilaria in this region, this study conducted a taxonomic investigation of intertidal macroalgae in the coastal waters of Zhanjiang using morphological, anatomical, and molecular approaches. The findings revealed the presence of five species: Gracilaria hainanensis, G. spinulosa, G. salicornia, and two as-yet undescribed species (Gracilaria sp.). The current taxonomic status of these five species was discussed, and several existing issues and controversies within the classification system were revealed. This study not only clarifies the taxonomy of Gracilaria species in the Zhanjiang coastal area, but also provides a theoretical basis for the development of red algal resources and the conservation of biodiversity in this region.

The epilithic algal matrix (EAM) is widely distributed in coral reef ecosystems and plays a crucial role in key processes such as primary production, nutrient recycling, sediment deposition, and coral reef phase shifts. To investigate the morphological characteristics and distribution patterns of EAM, a survey was conducted in a typical Sanya fringing reef in January, April, July, and October 2022, covering three transects (1 m, 3 m, 6 m). Substrate types and their coverage were recorded via video, and three substrate types (branched, massive, planiform) with epiphytic algae were sampled by scuba diving. The results revealed significant spatial but no seasonal differences in EAM coverage in the study area. Coverage was higher at 1 m and 6 m depths (66.96%) but lower at 3 m (16.55%), showing a negative correlation with live coral coverage. EAM primarily colonized highly porous hard substrates, with the highest coverage (98%) observed on dead planiform coral reefs. However, dead massive coral reefs exhibited the highest algal height [(11.16 ± 0.68) mm], highest biomass [(118.51±33.64) g∙m^-2], and greatest organic matter content [(102.49±32.94) g C∙m^-2], likely due to their higher surface porosity. EAM morphological characteristics and biomass varied with depth and season, peaking at 3 m and reaching their lowest values at 1 m. Temporally, EAM height, density, and biomass were highest in summer and lowest in winter. The study indicates that the benthic community in Sanya’s Luhuitou area is dominated by long sediment-laden algal turfs (LSATs) with high sediment content and heights exceeding 5 mm. This community type is unfavorable for coral larvae sediment and is avoided by herbivorous fish. EAM morphological traits and organic matter content exhibit distinct variations across substrates, depths, and seasons. Additionally, the rich organic matter in EAM may serve as a potential food source for benthic invertebrates, playing a vital role in the coral reef ecosystem’s food web.

This study presents a newly recorded species of the Ulva algae in China, Ulva ohnoi Hiraoka & S. Shimada 2004, collected from Fangchenggang (Guangxi) and Zhanjiang (Guangdong). Detailed morphological characteristics were described, accompanied by a multi-gene marker analysis. The results indicate that Ulva ohnoi exhibits both attached and floating forms. The thalli are light green, 15-60 cm in length, solitary or tufted. The tissue is brittle and easily torn, displaying round, ovate, or irregular shapes. The thallus surface cells are square or polygonal, arranged irregularly, with jagged protrusions along the edges. The upper and middle parts of the thallus are similar, with cell dimensions of 10-20 μm×5-15 µm and a thickness of 20-45 µm. In contrast, the basal cells are nearly round, measuring 10-30 μm×10-22 µm, with a thickness of 70-90 µm. Analysis of the rbcL and tufA gene sequences revealed that the samples collected in this study are genetically identical to the type specimens of Ulva ohnoi, supported by high bootstrap values and posterior probabilities. This study enriches the species diversity of the Ulva genus in China, underscores the significance of molecular biology techniques in identifying green algae species, and provides essential taxonomic data for the conservation and utilization of marine algae resources in China.

The non-native mangrove species Sonneratia apetala (S. apetala) poses a serious threat to regional native mangroves by occupying the habitat of indigenous species and expanding rapidly. This study takes the Maowei Sea Mangrove Nature Reserve in Guangxi, China, as a case study and investigates the spatiotemporal dynamics and key driving factors of the exotic mangrove from 2000 to 2023, using multi-temporal remote sensing imagery, UAV aerial photography, field surveys, and machine learning. The primary findings are summarized as follows: (1) From 2002 to 2023, the distribution area of S. apetala gradually increased from zero to 1076.77 hm². Between 2002 and 2015, it expanded slowly at a rate of 11.43 hm²·a^-1, reaching 138.20 hm² by 2015. From 2015 to 2023, the expansion accelerated to 116.46 hm²·a^-1. (2) S. apetala exhibited a distinct gradient distribution pattern across the Maowei Sea: clustered in the west, interspersed with native mangroves in the central tidal flats, and scattered point occurrences in the east. Its expansion progressed in two stages: from 2002 to 2014, it spread from the western Kangxiling tidal flats along the banks of the Dalan River, followed by crossing the river and establishing itself in the central Maowei Sea by 2015, with subsequent eastward expansion between 2015 and 2023. (3) Artificial planting and mangrove conservation efforts within the reserve were the direct drivers of the establishment and continued expansion of S. apetala in the Maowei Sea. Sediment carried by riverine runoff contributed to tidal flat accretion, providing space for its expansion. Meanwhile, the Coriolis force, which causes a rightward deflection of tidal currents, was the primary factor driving the eastward spread and upstream migration of S. apetala along the river. This study offers theoretical insights and data support for controlling the rapid spread of S. apetala in the Maowei Sea and preserving the health and biodiversity of the native mangrove ecosystem.

Studying changes in estuarine saltwater intrusion patterns can deepen the understanding of its mechanism and help better ensure the safe use of freshwater resources. Based on measured topographic and salinity data, this paper analyzes changes in river regime and saltwater intrusion patterns in the Changjiang Estuary. A numerical model is used to reveal the causes of these pattern changes. From 2007 to 2021, major reclamation projects in the estuary led to channel narrowing and significant local topographic changes. Due to severe siltation on the south side of the lower North Branch and the emergence of a new sand body at its upper end, the channel volume decreased by 33.33% and 13.26% (with the negative sign denoting northward transport from the south), respectively. Salinity observations in the dry seasons of 2007 and 2025 indicate a significant weakening of saltwater intrusion and of the North Branch saltwater backflow into the South Branch. In the North Channel, saltwater intrusion weakened under prevailing climatic winds but intensified under strong northerly winds. Overall, the saltwater intrusion pattern in the Changjiang Estuary has changed. Numerical simulations, considering multi-year monthly mean river discharge and wind, show that from 2007 to 2021, saltwater intrusion weakened significantly in the North Branch, weakened in the upper and most middle reaches of the North Channel, but intensified significantly in the South Channel, North Passage, and South Passage. The saltwater backflow from the North Branch into the South Branch was greatly reduced, resulting in weakened saltwater intrusion in the South Branch, which is conducive to water intakes at source areas. In the North Branch, the tidal prism decreased by 2.88×10⁸ m³ and 1.98×10⁸ m³ during spring and neap tides in February, respectively. The net water flux into the South Branch decreased by 423 m³·s^-1 and 369 m³·s^-1, and the net salt flux into the South Branch decreased by 10.06 kg·s^-1 and 1.10 kg·s^-1. The variation of net unit-width salt flux in the upper North Branch also indicates a major reduction in salt transport to the South Branch. Significant North Branch backflow observed in 2007 had nearly disappeared by 2021. In the North Channel, during February spring and neap tides, the tidal prism decreased by 1.92×10⁸ m³ and 1.86×10⁸ m³, while the net water flux increased by 857 m³·s^-1 and 1379 m³·s^-1. The water diversion ratio increased by 12.79% and 7.79%, and the net seaward salt flux decreased by 2.28 kg·s^-1 and 5.42 kg·s^-1. These changes explain the weakening of saltwater intrusion in the upper and most middle reaches of the North Channel. The obvious increase in the North Channel’s water diversion ratio (corresponding to a decrease in the South Channel’s ratio) also accounts for the intensification of saltwater intrusion in the South Channel, North Passage, and South Passage. A localized salinity rise in a small part of the North Channel during spring tide is caused by a significant increase in the net salt flux from the North Passage into the North Channel. This paper reveals the hydrodynamic causes of the changing saltwater intrusion pattern in the Changjiang Estuary through changes in net water flux, net salt flux, tidal prism, and water diversion ratio.

The deep water of the Eastern Indian Ocean is a crucial component of the global deep-sea system, playing a significant role in the global carbon cycle and the distribution of heat and nutrients. It is divided by the Ninety East Ridge into the Central Indian Basin (CIB) and the West Australian Basin (WAB). These two basins exhibit distinct differences in their water mass characteristics and circulation patterns. To further understand the deep-sea circulation and water mass features in the Eastern Indian Ocean, this paper reviews existing research findings and summarizes the following aspects: 1) the unique topography of the deep Eastern Indian Ocean; 2) the sources and pathways of deep-sea water masses; 3) the deep meridional overturning circulation; and 4) the differences and connections between the deep-sea water masses in the CIB and the WAB. Finally, this paper highlights key scientific issues that need to be addressed in future research on the deep sea of the Eastern Indian Ocean, providing a reference for related studies.

Cnoidal waves can effectively characterize wave motion in shallow water regions, holding significant practical value for the precise description of nearshore hydrodynamic processes. To investigate the propagation and evolution patterns of cnoidal waves over typical reef-lagoon systems, this study conducted physical model experiments in a wave flume, with particular focus on the effects of incident wave height, reef flat submergence, and wave period on wave nonlinear characteristics, energy dissipation, and hydrodynamic parameters. The results demonstrate that reef topography substantially enhances wave nonlinearity, with conspicuous waveform steepening in the fore-reef slope zone and sawtooth-shaped wave profiles accompanied by phase lags over the reef flat. Increased incident wave height induces stronger nonlinear effects, promoting higher harmonic growth and significantly enhancing wave setup and run-up, while reducing reflection coefficients due to enhanced transmission. However, greater reef flat submergence weakens nonlinear wave effects and causes a monotonic decrease in reflection coefficients. Under deeper water conditions, vertical momentum flux intensifies, and run-up exhibits nonlinear growth. The influence of wave period manifests complex patterns: the maximum wave energy concentration and the most pronounced higher harmonics occur at T = 2.25s. Short-period waves (T < 2.25s) experience intensified shoaling deformation that aggravates waveform distortion, whereas long-period waves (T > 2.25s) exhibit characteristic attenuation through energy dissipation. This research provides critical experimental evidence for coral reef ecosystem conservation and coastal engineering design.

As an emerging offshore solar solution, floating photovoltaic technology can support the energy transition in coastal regions, expand the utilization of marine resources, and has broad development prospects. It is expected to provide significant support for the country's “3060” dual-carbon strategy. To address the current lack of research on power generation calculation methods for offshore floating photovoltaic systems, this study proposes a power generation calculation model based on the wave dynamics and other marine environmental characteristics of the target sea area. First, based on wave mechanics and floating body hydrodynamics, and considering the steepness of the target sea area d as a small value (wave height h / wave length l ≤ 1) as a boundary condition, the study uses the irradiation energy efficiency η and the time-averaged tilt angle ε to quantify the long-term impact of waves on photovoltaic modules. This yields an equivalent irradiance objective function for the inclined surface under regular wave action. Second, considering seawater reflection, evaporation, and convection, the influence of module backside and water surface cooling effects is incorporated. A practical calculation formula for backside irradiance and a water surface cooling effect factor are introduced to characterize the positive gains from the module backside and water surface cooling. Finally, a comparison with field measurements at the target site demonstrates that the calculated values deviate from the theoretical values by less than 10%, which falls within the expected margin of error.

Mangrove wetlands, located in the intertidal zones of tropical and subtropical regions, are critically important coastal ecosystems, providing significant value in typhoon resistance, coastal seawall protection, and carbon sequestration. However, complex land-sea couplings have caused large-scale mangrove loss worldwide. Understanding the dynamic changes of mangrove wetlands is crucial for comprehensive grasping their losses and underlying causes, providing necessary support for their restoration. Based on the Google Earth Engine platform, this study extracted spatiotemporal dynamic information of mangrove wetlands at the Maolingjiang Estuary of Beibu Gulf from 1992 to 2021, and analyzed mangrove dynamics and associated influencing factors. The results showed that: (1) as of 2021, the tidal flats at the Maolingjiang Estuary contained 707.76 hm² of mangroves, with Aegiceras corniculatum as the building species. Mangroves were mainly distributed in the Dalidun and Tuanhedao tidal flats, with the least distribution in the Liangwu tidal flat near the southern side of the main stream. (2) From 1992 to 2021, the tidal flats at the Maolingjiang Estuary experienced a process of "increase-decrease-increase", while mangrove area consistently expanded. (3) From 1992 to 2021, the construction of aquaculture ponds was the primary driver of phased regional mangrove loss, while large-scale mangrove afforestation projects initiated since 2002 led to a significant rebound in mangrove coverage, with tidal flat progradation serving as the key natural facilitator for seaward mangrove expansion.

The presence of offshore swell seriously affects the quality of high-resolution marine seismic data, posing substantial challenges for subsequent processing and geological interpretation. Existing swell static correction methods — whether based on intrinsic data features such as model channel cross-correlation and medium/mean filtering, or externally constrained approaches like single/multi-beam bathymetry — have inherent limitations in their applicability. Therefore, developing a simple, fast, and efficient swell static correction method is of great significance. To address this widespread issue, this paper proposes a more universal swell static correction technique. After briefly introducing its fundamental principles and implementation steps, we first analyze the swell effect on synthetic data from a horizontal layered model, then apply the method to field data for swell suppression. The reliability and effectiveness of the proposed method are quantitatively verified. The results demonstrate that regardless of whether the seafloor exhibit gentle undulations or complex rugged topography, our method effectively suppresses high-frequency jitter and energy dispersion in reflection events caused by swell effects. This enhances reflector clarity, smoothness, and continuity, significantly improving the resolution and signal-to-noise ratio of seismic sections. The method thus facilitates subsequent stratigraphic division and seismic interpretation.

Sri Lanka, an island nation, holds strategic importance as a key node in the Indian Ocean shipping routes. This paper delves into the unique geological structure of Sri Lanka, characterized by steep terrain and frequent geological hazards, against a backdrop of limited preventive capabilities. Commencing with an analysis of these geological structure, we highlight the pressing livelihood and welfare challenges caused by recurrent geological hazards. Subsequently, we underscore the urgency and feasibility of establishing a comprehensive geological monitoring platform in coastal cities to address these challenges. We then elaborate on a three-phase deployment strategy for this early geological hazard monitoring platform, demonstrating its practical application. Furthermore, we identify two critical scientific issues requiring immediate attention: (1) the tectonic evolution mechanism of Sri Lanka, and (2) the stability of shallow geological structures in coastal cities. To this end, we emphasize the necessity of utilizing the latest seismic data to focus on studies of geological and velocity structures in Sri Lanka's coastal areas. Establishing standards for geological stability assessment and analyzing the temporal and spatial variation characteristics of geological hazards will provide scientific evidence for effective hazard prevention. More importantly, a more comprehensive model of geological structure evolution will be built through multidisciplinary approaches, integrating petrology, geochemistry, geophysics, and geological dating. This research aligns with the Belt and Road Initiative by prioritizing geological hazard prevention and advancing fundamental research on geological structures, carrying profound scientific and strategic implications.

This study reconstructs the three-dimensional dynamic temperature field in the Northwest Pacific Ocean using high-resolution satellite sea surface data and historical ocean temperature and salinity profile data, based on the variational method. Compared to the array for real-time geostrophic oceanography (Argo) temperature profiles, the reconstructed temperature field reasonably reproduces the vertical distribution of seawater temperature, particularly in the thermocline region, where the results closely match the actual observed temperature profiles. Two typical mesoscale eddy cases were selected for analysis of their entire evolution process — from generation to decay — using the reconstructed temperature field, displaying the dynamic changes in the vertical and horizontal distribution of temperature anomalies induced by the eddies. In particular, during the mature stage of the eddies, the intensity and vertical extent of the temperature anomalies reach their maximum, reflecting the significant impact of the eddies on the oceanic thermocline. By analyzing the distribution of temperature anomalies at different stages, the study reveals the evolution of the spatial structure of cold and warm cores and the anomalous regions. The results show that the method can effectively utilize satellite sea surface observations to reconstruct the underwater temperature structure and dynamic evolution of mesoscale eddies, providing valuable data support for understanding their role in oceanic material and heat transport.

The outbreak of crown-of-thorns starfish (Acanthaster planci, CoTS) poses a significant threat to the health of coral reef ecosystems. Artificial removal is considered one of the most practical and effective methods for addressing local outbreaks of CoTS. However, the marine environmental impact of discarding inactivated CoTS after capture is currently unclear. In this study, an in situ experiment was conducted to assess the ecological and environmental effects of boiled and inactivated CoTS remains. The results showed that boiled CoTS tissues decomposed within 2 days, with the skeletal remains breaking down into granular fragments. By the 9th day after returning the CoTS to the sea, 63.20% of carbon, 62.18% of nitrogen, and 44.17% of phosphorus were released into the water, resulting in an increase of (0.08 ± 0.06) mg·L^-1 in carbon, (0.08 ± 0.08) mg·L^-1 in nitrogen, and a decrease of 0.01 mg·L^-1 in phosphorus concentrations. In addition, the dominant bacteria on the surface of the inactivated CoTS primarily belonged to Proteobacteria, Cyanobacteria, Actinobacteria, and Bacteroidetes. Dominant genera included Sphingomonas (Bacteroidetes), and Ruegeria, Pelomonas, Nautella, and Tenacibaculum (Proteobacteria), which are associated with CoTS decomposition. The boiled and inactivated CoTS remains decomposed rapidly and released nutrients directly. A small amount of inactivated CoTS does not cause significant adverse environmental effects, suggesting this method is a relatively economical and eco-friendly approach for managing CoTS outbreaks.

The interaction between phages and bacterial hosts significantly impacts coral health and reef stability, representing a key focus in virology. To combat phage infection, bacteria have evolved diverse innate and adaptive immune systems, including toxin-antitoxin (TA) systems, a crucial defense mechanism. In this study, bioinformatics analysis predicted that the CTT34_05265 and CTT34_05260 genes within the prophage Phm2 of the coral-associated bacterium Halomonas meridiana SCSIO 43005 (Hm43005) encode HmHicA and HmHicB proteins, respectively. Their TA system functionality was confirmed through E. coli growth assays. Pull-down and bacterial two-hybrid experiments validated the interaction between HmHicA and HmHicB. Electrophoretic mobility shift assays (EMSA) and DNase I footprinting revealed that HmHicB specifically binds to palindromic sequences upstream of the -35 and -10 regions of the hicAB promoter, mediating transcriptional autoregulation. Additionally, HmHicB alone exhibited mild toxicity, suggesting potential alternative regulatory targets for the antitoxin. Structural analysis indicated that HmHicA functions as a ribosome-independent RNase, while HmHicB contains an N-terminal toxin-binding domain and a C-terminal DNA-binding domain. HmHicB forms a homodimer via its C-terminus and assembles with HmHicA in a 2:2 stoichiometric complex. The molecular mechanism of antitoxin-mediated toxin inhibition likely involves electrostatic interactions between the positively charged active pocket of HmHicA and the negatively charged toxin-binding domain of HmHicB, as well as the burial of the HmHicA His24 active site. These findings provide a foundation for further exploration of the properties and physiological roles of this TA system.

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by the progressive loss of articular cartilage and the destruction of joint structures. This study investigates the potential role of sea cucumber peptides in combating OA. Potential bioactive peptides from sea cucumber protein were identified through computer simulations of gastrointestinal digestion and online database predictions. Using network pharmacology, molecular docking, and quantum chemical calculations, a sea cucumber peptide candidate (phenylalanine-aspartic acid-proline-valine-isoleucine-glutamic acid-glutamic acid-tyrosine-histidine-asparagine-glycine-phenylalanine, FDPVIEEYHNGF) with strong anti-OA activity was virtually screened. Further analysis suggests that this peptide may alleviate OA by modulating the IL-17 and TNF signaling pathways, inhibiting inflammation, collagen degradation, and the activity of matrix metalloproteinases (MMPs). The sea cucumber peptide may form hydrogen bonds with MMP9 and IL-17RA, potential core targets for OA, thereby influencing the related signaling pathways, reducing inflammation, intervening in extracellular matrix remodeling, and mitigating collagen degradation. This study provides new insights into the application of sea cucumber peptides as functional food ingredients in the development of therapeutic foods for OA.

Through detailed interpretation of high-resolution 3D seismic data from the deepwater area of the Qiongdongnan Basin, this study identifies four stages of Mass Transport Complexes (MTCs) on the northeastern slope of the basin: MTC1, MTC2, MTC3, and MTC4. Among these, MTC1, MTC2, and MTC4 are relatively small in scale with low internal compression, averaging 130-150 m in thickness, while MTC3 is the largest and exhibits the most intense internal deformation, with an average thickness of 200 m. By identifying and analyzing the kinematic indicators within and outside MTC3, its southwestward transport direction was determined, and its developmental process was divided into three stages: initial slope instability, sliding, and fluid transformation. Based on the morphology and internal structural characteristics of the identified MTCs, combined with the tectonic and climatic evolution of the study area, it is concluded that the development of these multi-stage MTCs is influenced by the combined effects of stratigraphic slope, sea-level fluctuations, and high sedimentation rates, with the continuous strike-slip movement of the Red River Fault Zone being the dominant controlling factor. Specifically, the rapid fall and rise of sea levels after the late Miocene (10.5 Ma) altered sediment strength and stratigraphic pressure parameters, promoting MTC development. The rapid subsidence of the Qiongdongnan Basin since 5.5 Ma increased accommodation space, enhanced sediment progradation, and steepened slopes, creating conditions for multi-stage MTC formation. Additionally, fault activity triggered by the continuous strike-slip movement of the Red River Fault Zone is the primary factor triggering the multi-stage MTCs in this region. This study enhances the understanding of the depositional characteristics and triggering factors of multi-phase MTCs on the northeastern slope of the Qiongdongdong Basin and provides insights for exploring MTC development in the South China Sea.

As secondary producers, zooplankton play an important role in marine food webs and biogeochemical cycles. Due to their small body size, rapid metabolism, and passive drifting lifestyle, zooplankton can respond sensitively to marine environmental changes, making them effective indicators of oceanic variability. Based on a review of scientific investigations of zooplankton in the South China Sea, this paper summarized current knowledge on species composition in the South China Sea, and compared and analyzed the distribution of zooplankton communities in typical ecological habitats (such as the Pearl River Estuary, Daya Bay, coral reefs, and the deep sea) as well as in the northern and southern waters of the South China Sea. It also discussed the effects of monsoons, monsoon-driven ocean currents, water masses and habitat heterogeneity on zooplankton community structure. In light of current hotspots and challenges under the background of climate change and anthropogenic stress, this article pointed out the shortcomings in zooplankton research in the South China Sea and proposed future research directions in biodiversity, ecological functions, and biological oceanography. The aim is to provide a scientific basis for biodiversity conservation, biogeochemical cycle studies, sustainable utilization of marine resources, and scientific support for predicting the adaptability of marine ecosystems to climate change in the South China Sea.

As a key component of the mid-latitude arid belt in Eurasia, arid West Asia is characterized by perennial aridity, low precipitation, intense evaporation, and fragile ecosystems, making it highly sensitive to coupled precipitation-temperature variations. Clarifying the climatic evolution patterns in West Asia is therefore crucial for predicting future climate trends and ensuring regional economic development and social stability. However, long-term trend analyses of precipitation in West Asia remain challenging due to the sparsity of paleoclimate records, which are often contradictory. This study synthesizes hydroclimatic records from the past three decades to summarize Holocene moisture patterns in West Asia and discuss their potential drivers. Existing pollen records suggest a long-term increase in effective moisture during the Holocene. In contrast, speleothem and lacustrine carbonate δ¹⁸O records demonstrate a progressive aridification trend during the Holocene. After reviewing existing hydroclimatic records in West Asia, we infer that the δ¹⁸O variations in secondary carbonates in West Asia are dominated by seawater δ¹⁸O dynamics in eastern Mediterranean, rather than directly recording local precipitation amount. Based on multi-proxy hydroclimatic records and reliability assessments of paleoclimate indicators in West Asia, this study infers that the millennial-scale climatic patterns in the arid regions of West Asia during the Holocene were closely linked to the intensity and latitudinal shifts of the westerlies, which were primarily modulated by summer insolation. During the early Holocene, increased summer insolation led to higher surface temperatures, driving a northward shift of the westerly circulation. It reduced moisture transport by the westerlies to West Asia, resulting in drier conditions. However, increased precipitation in the East African monsoon region enhanced freshwater discharge from the Nile and other rivers into the Mediterranean Sea, resulting in a negative δ¹⁸O excursion in Mediterranean seawater. Consequently, this modified moisture source signature led to depleted δ¹⁸O values in precipitation records across West Asia. The late Holocene exhibited opposite characteristics.

In this study, Lobophytum sp. was cultured under different water qualities for one month, and the community structure of Symbiodiniaceae, ambient water bacteria, and symbiotic bacteria were analyzed using high-throughput sequencing technology. The findings indicated the following. 1) Symbiodiniaceae richness decreased significantly under nutrients conditions ranging from 0 to 80.64 μmol·L^-1 nitrate and 0 to 1.05 μmol·L^-1 phosphate. Cladocopium sp. dominated the Symbiodiniaceae in all three coral groups, with a relative abundance ranging from 70.25% to 98.13%, exhibiting higher tolerance to low nutrients concentration but greater sensitivity to high nutrients concentration. 2) At the phylum level, water-associated bacteria and coral symbiotic bacteria differed in relative abundance, with all dominant bacterial populations belonging to Proteobacteria, ranging from 45.63% to 86.55% in relative abundance. However, the environmental bacterial diversity at the genus level (Shannon index 4.60~4.97) was higher than that of coral symbiotic bacteria (Shannon index 2.58~3.81), with distinct taxonomic separation between the two communities at the genus level. 3) The coral symbiotic bacterium Cohaesibacter exhibited high tolerance to low nutrient levels, with its relative abundance increasing significantly from < 3% to 40.27% as nutrient levels decreased. Additionally, this genus of soft corals demonstrated strong adaptability to symbiotic bacteria Vibrio, with no significant anomalies observed even at a high Vibrio abundance of 23.71%. These results suggest that the abundance of Symbiodiniaceae and symbiotic bacteria in corals is influenced by ambient water quality, leading to changes in dominant bacteria and alterations in community structure of symbiotic bacteria from corals. Moreover, nutrient fluctuations preferentially shaped the community structure of coral-associated bacteria over environmental bacteria, with more pronounced effects on the former. This study contributes to the growing body of research on soft corals by providing a foundation for understanding how different water quality parameters dynamically affect the structure of symbiotic microorganisms in soft corals. It also offers insights into the effect of water quality fluctuations on soft coral Symbiodiniaceae and bacterial community structure in artificial environments, thereby supporting the development of coral conservation programs.