The sample was obtained in the South China Sea, and its morphological characters are very similar to those of the Phyllidiidae species. It is elongated and ovoid, with a dark grey dorsal surface and irregular creamy-white verrucae, and two rows of orange protrusions in the center of the dorsal surface in parallel. In this study, this species was identified by mitochondrial whole genome sequencing and analyzed based on the sequences of protein-coding genes (PCGs). The results show that the full length of the mitochondrial genome is 14677 bp, containing 37 genes, which are 13 PCGs, 2 rRNAs and 22 tRNAs. The base composition of the mitochondrial genome is 30.4% A, 37.3% T, 15.0% C, and 17.3% G, with a preference for AT (67.7%). Among the 13 PCGs, there are 11 start codons conformed to the codon form of ATN, which used TTG as the start codon. The evolutionary tree was constructed using the maximum likelihood method, and the results show that this species is closely related to Phyllidiella pustulosa and clustered with Phyllidia ocellata. The complete mitochondrial genome sequence similarity between this species and P. pustulosa reached 94.6% by BLAST, and the gene sequence similarity of COX1 reaches 98.8%. Based on combined morphological characters and molecular identification, it is a new species of the genus Phyllidiella in the South China Sea, Phyllidiella nanhaiensis sp. nov.. The mitogenome of P. nanhaiensis sp. nov. will provide a reference for further study of the genus Phyllidiella, which is important for the study of species diversity and phylogeny of sea slugs.

The Indo-Pacific Convergence Region is the center of the origin in marine biodiversity and has extremely high biodiversity. With the dramatic changes in global climate and human activities intensify, ecosystems are gradually fragmenting. In this context, marine fish play important ecological functions in connecting fragmented ecosystems and protecting biodiversity. Exploring the genetic structure and connectivity of typical fish species in the Indo-Pacific Convergence Region will clarify the genetic diversity patterns and diffusion paths among different populations, thereby providing scientific support for the protection of biological diversity. In this study, 8 fish species (Acanthurus japonicus, Balistapus undulatus, Cephalopholis urodeta, Ctenochaetus striatus, Gnathodentex aureolineatus, Lutjanus kasmira, Melichthys vidua and Parupeneus multifasciatus) were collected from 5 representative areas in the Indo-Pacific Convergence Region (Zhongsha Islands, Nansha Islands, Xisha Islands, Hainan Island, and the Philippines), totaling 309 samples, 515 mitochondrial COI genes and 16S sequences were obtained; To broaden the scope of the study, cytochrome C oxidase subunit I (COI ) gene sequences from the Taiwan Island in China and Indonesian were downloaded from GenBank, amounting to 86 sequences. Based on this, we analyzed the genetic diversity and genetic differentiation structure among different groups in the above seven study regions. The overall results show that 8 fish species have high levels of genetic diversity and low genetic differentiation, among which Parupeneus multifasciatus and Balistapus undulatus are the most obvious; Indonesia, Taiwan Island in China and South China Sea Island populations also have high genetic diversity. The study further developed the species distribution models and the least-cost paths model to explore the population connectivity. Based on this, distribution information for the eight fish species (collected from a total of 133, 047 points) was used to predict suitable distribution areas under current climate using the MaxEnt algorithm, and the connectivity between different populations was calculated using the ArcGis 10.2 software SDMtoolbox v2.5. Population connectivity reveals that the east coast of the Philippines-Sulawesi is an important dispersal path for the above eight typical fish species in the Indo-Pacific Convergence Region. The South China Sea Islands (Nansha, Zhongsha and Xisha Islands) connect Taiwan Island in China, the Philippines and Indonesia, and serve as connecting hubs for species spread. In summary, the Philippines, Indonesia, Taiwan Island in China, and the South China Sea should become priority protected areas for maintaining genetic diversity and protecting connectivity. When protecting biodiversity, population connectivity and genetic diversity should be comprehensively considered, and different research results reflected at the macro and micro levels should be combined to achieve more effective biodiversity conservation.

Cyclic GMP-AMP synthase (cGAS) is a critical intracellular sensor that can recognize abnormally located DNA in the cytoplasm and trigger immune responses. To elucidate the critical role of cGAS in the regulation of innate immunity in mollusks, we successfully cloned and analyzed Crassostrea gigas cGAS (CgcGAS). The open reading frame (ORF) of CgcGAS was 1623bp and encoded 540 amino acids with a theoretical molecular weight of 62.3 kDa and a conserved Mab21 domain. Phylogenetic analysis confirmed that CgcGAS was a member of the molluscan cGAS family. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) results revealed widespread expression of CgcGAS in various tissues, with the highest relative expression in the digestive glands. Subsequently, subcellular localization experiments showed that CgcGAS was observed in both the nucleus and cytoplasm, with a predominant nuclear localization, suggesting that CgcGAS may have played a role in DNA sensing in the nucleus and DNA binding and signaling in the cytoplasm. Furthermore, dual-luciferase reporter gene assays and RNA interference experiments revealed that CgcGAS could activate the NF-κB and ISRE signaling pathways, as well as the expression of downstream inflammation-related factors, such as virus inhibitory protein endoplasmic reticulum-associated interferon-inducible (viperin), tumor necrosis factor (TNF), interleukin-17 (IL-17), and the transcription factor interferon regulatory factor 2/8 (IRF2/8). In conclusion, CgcGAS played a critical role in the signal transduction process of innate immune responses in Crassostrea gigas.

In this experiment, the conditions for amplifying polyp populations and strobilation of Phyllorhiza sp. were studied. The asexual reproductive process and the metamorphosis of ephyra into medusa were observed and described. Phyllorhiza sp. is characterized by two asexual reproduction modes: swimming buds and strobilation. Polyps can be permanently stored in laboratory. Both the producing swimming buds and strobilation can be observed at 20~25°C. It takes 10~12 days for metamorphosis to mature polyps after swimming buds attachment. It takes 2~3 days to produce swimming buds for polyp asexual reproduction. Monodisc is the strobilation mode of Phyllorhiza sp. and it takes 4~5 days before the ephyra gets rid of the residual polyp. The edge of the central disc of strobila keeps blue-purple from the formation of rhopalia to the disappearing of polyp tentacles. It takes 12 days for ephyra to develop into juvenile medusa under 25°C, 29‰~32‰ (salinity).

Sargassum wightii is a common species in the Weizhou Island of Guangxi, Xuwen of Guangdong and other sea areas, and is an economic macroalgae. Understanding the annual growth and early development of macroalgae can predict the mature time of thalli and provide scientific basis for artificial seedling and cultivation of macroalgae. This paper reports the annual growth characteristics, the effect of temperature on ovulation and the early developmental process of sexual reproduction of S. wightii in the sea area of Xuwen, Guangdong. The results show that the annual growth of S. wightii can be divided into 4 periods: fast growing period, mature period, decline period and resting period. The average length of thalli reaches its maximum [(188.32±43.77) cm] in early April, exceeding 180 cm in both April and May, and less than 5 cm in late July to early November. The male and female reproductive parts of S. wightii are in the same receptacle, and the egg cell development belongs to 8-nucleui type. The culture temperature is very important to the ovulation process. Ovulation could not be achieved at 15, 27 and 30 ℃, but could be achieved at 18~24℃. The ovulation time is shortest at 24 ℃, only 3 d. The zygotes develop into germlings with rhizoid buds at 24 ℃ for about 24h, and the seedlings develop a fourth leaflet after 30 d of culture. The results of this study provide basic information for the biology, ecology, artificial seedling and cultivation of S.wightii.

The structure of phytoplankton community was investigated based on morphological identification and high-throughput sequencing in the Nan’ao waters in May 2022. The spatial distribution of phytoplankton in relation to environmental factors was explored and results from two different methods were also compared and discussed. According to the cluster analysis of environmental factors, the survey area can be divided into nearshore area and offshore area. Totally, 105 species belong to 52 genera, 39 families, 27 orders, 8 orders, 5 phyla were morphological identified, while 543 species in 6 phyla, 32 orders, 97 families, 155 families, 272 genera through high-throughput sequencing were identified. Bacillariophyta and Dinophyta were the main groups, composing 74.54% and 24.78% through microscopic identification, and 17.52% and 67.84% through high-throughput sequencing, respectively. The abundance of phytoplankton identified by morphology ranged from 0.11×10⁵ to 6.85×10⁵ cells·L^-1, which was significantly correlated with the distribution of chlorophyll a concentration, and the phytoplankton diversity index was lower than that of the high-throughput sequencing method. 7 dominant species were obtained by both methods, of which the absolutely dominant specie in the morphological identification results was Chaetoceros compressus, and the absolute dominant specie in the high-throughput sequencing identification results was Heterocapsa rotundata. Correlation analysis showed that the main environmental factor affecting phytoplankton community structure in Nan’ao in spring was pH, salinity and DIP (dissolved inorganic phosphorus). Using the combination of morphological identification and high-throughput sequencing technology, the structure and diversity of the phytoplankton community can be described more comprehensively and accurately.

Based on mooring data deployed west of the Xisha Islands from October to November 2020, we investigated the characteristics of near-inertial waves (NIWs) triggered by three consecutive typhoons in detail, including the decay time scales and vertical structures of the NIWs, as well as the modulation of the background vorticity and current fields on the NIWs, etc. The vertical wavelengths of NIWs induced by Typhoon Saudel, Molave and Vamco are 109 m, 133 m and 117 m, respectively, and the vertical group speeds are 29 m·d^-1, 26 m·d^-1 and 18 m·d^-1, respectively. The decay time scales for these internal waves are 3 d, 7 d and 15 d, respectively. It reveals that ocean stratification significantly impacts the vertical group speed of NIWs. The longest decay time in the Vamco case is attributed to the second EOF (empirical orthogonal function) mode of NIW propagated from far field. The results of the dynamical mode decomposition (DMD) and EOF are consistent with each other. Both show that the first modes contribute the most to near-inertial kinetic energy (NIKE), and the distributions of NIKE in different modes obtained from DMD and EOF are comparable. For example, the NIKE is mainly distributed in the first, third and second DMD modes at depths of < 100 m, 100~150 m and 150~350 m. The observed frequencies of the NIWs are all blue-shifted, and the blueshifts in Typhoon Saudel and Molave are due to the combination of the background current and vorticity, while the positive background vorticity due to the cyclonic eddy during the Vamco is the main reason for the observed blueshift. Our results are useful for a deeper understanding of the characteristics, propagation, dissipation and energy distribution of strong wind-induced NIWs and their mechanisms, and they also provide a good reference for numerical simulations.

The distribution characteristics of marine heatwaves in the northwest Pacific Ocean, from July 1 to September 30, 2022, were analyzed based on the coral reef watch (CRW) heatwaves monitoring dataset using satellite remote sensing. The typical marine heatwaves processes at single stations and formation mechanism of regional heatwaves in three regions with strong heatwaves were mainly explored. A composite analysis of atmospheric and ocean variables was used to investigate the mechanism of marine heatwaves. The results indicate that: (1) The spatial distribution of various attributes of marine heatwaves in the northwest Pacific has certain similarities except for the maximum intensity, and overall, the high values are relatively concentrated. (2) The properties of marine heatwaves in the offshore area of Jiangsu are significantly higher than those in other regions; the Kuroshio basin near Taiwan has a lower maximum intensity but longer duration of marine heatwaves; the values of various attributes of marine heatwaves in the offshore area of Guangdong are above the spatial mean of Northwest Pacific Ocean. (3) The generation of a marine heatwave in the offshore area of Jiangsu within 92 days is closely related to the combined effect of atmospheric forcing under the expansion of the Western Pacific Subtropical High and the transport process of atmospheric wind field with a large amount of sensible heat and latent heat from the Kuroshio basin. The marine heatwaves in the Kuroshio basin near Taiwan and the offshore area of Guangdong are mainly caused by the increased solar radiation under the control of the Western Pacific Subtropical High.

The tidal dynamics of lagoon systems exert profound influences on their geomorphic evolution, ecological conservation, and sustainable development of coastal resources. This study focuses on the Shuangyue Bay Lagoon in Huizhou, Guangdong Province. Utilizing four sets of tidal level observations from 2020 to 2023, we employed a modified harmonic analysis model based on the principle of smoothness (MHACS) alongside statistical methods to preliminarily investigate the propagation and variation processes of tidal waves within the lagoon system. The results reveal that the average tidal range in the Shuangyue Bay lagoon system spans from 0.52 to 0.69 m. As tidal waves propagate from the mouth to the upper reaches of the lagoon, their energy diminishes significantly, with an attenuation rate in the upstream region approximately 20 times greater than that near the mouth. Additionally, the propagation speed of tidal waves decreases to approximately 12% of its value near the mouth. Dominant tidal constituents within the lagoon include the semi-diurnal tide M₂, diurnal tide K₁, and shallow-water tide M₄, with amplitudes of 23.06 cm, 30.4 cm, and 7.74 cm, respectively. While the amplitudes of diurnal and semi-diurnal tides exhibit relatively stable monthly fluctuations, shallow-water tides display more pronounced seasonal variations, particularly evident when propagating upstream, where the amplitude and phase lag of tidal components undergo significant seasonal changes. Tidal waves enter the Shuangyue Bay Lagoon through its mouth, encountering influences from terrain convergence and bottom friction effects. The propagation speed of tidal waves varies significantly across different river sections, with the speed of semi-diurnal tides generally higher in the mouth area compared to diurnal tides. Moreover, the amplitude attenuation of each tidal component within the lagoon is substantial, particularly notable for the amplitude gradient of S₂, M₄, and MS₄ tidal constituents, which reaches up to 4×10^-6 m^-1.

Using in-situ data collected by summer cruises during 2021−2023, summer hydrological variations and their influencing factors were studied. The results show that the summer temperature and salinity were charactered by northeast-southwest distribution pattern, while variations in values were significant during the investigation. Mean sea surface temperature (SST) was lowest in 2021 but highest in 2022. Bottom temperature was highest in 2021, but moderate in 2022 and lowest in 2023. Strong runoff caused a significant outward expansion of diluted waters, sea surface salinity (SSS) was strikingly lower in 2022 than those in 2021 and 2023. Bottom salinity was highest in 2023, moderate in 2021 and lower in 2022. Temperature and salinity variations in the middle and low layers were related to the passage of typhoons and invasion of shelf cold and saline water. Those vertical temperature and salinity observed after Typhoon Lupit passed in 2021 mixed homogeneously, weakening stratification. Bottom shelf water intruded into the Lingding Bay, forming a low-temperature zone and apparent salinity front. Middle and bottom temperature (salinity) decreased (increased) owing to the enhanced bottom shelf water intrusion in sequence in 2022 and 2023. In 2023, strong upwelling inhibited the expansion of diluted water seaward to increase SSS over the shelf higher than those in 2021 and 2022. Bottom temperature and salinity varied with the tide, in which the shoreward movement of cold and saline water tended to decrease temperature and increase salinity during flood tide, while the opposite occurred during ebb tide. The positive correlation between SST and air temperature suggested that SST varied with air temperature.

As a result of climate change and human intervention, jellyfish outbreaks have become a serious ecological disaster that threatens coastal economies and marine ecosystems. Globally, there is an urgent need to prevent jellyfish blooms. Microorganisms play an important role in the growth and development of marine invertebrates. Co-culture experiments revealed that Bacillus paranthracis SG49 inhibits the settlement and metamorphosis of Aurelia coerulea planula larvae. The key metabolic pathways and mechanisms behind this inhibition, however, require further investigation. Using non-targeted metabolomics technology, the intracellular and extracellular metabolites of SG49 were detected, differences between the two groups were analyzed, and potential metabolites affecting planula larval metamorphosis were identified. Our results showed that SG49 intracellular and extracellular metabolites were significantly different. Specifically, seven substances were screened for their potential inhibitory activities, including 3-hydroxy-2-oxindole, kanamycin, apramycin, streptomycin, streptomycin sulfate, gallic acid, and coniferyl alcohol. Bacterial biofilms and microorganism growth can be inhibited by these metabolites. Our findings provide a theoretical basis and strain resources to prevent jellyfish outbreaks in the future.

2-ethylhexyl-4-methoxycinnamic acid (EHMC) is an organic UV filter that is widely used in domestic sunscreen products. It is released into the ocean via human activities and accumulated in coral tissues, hastening coral bleaching. Biodegradation is an effective method for removing EHMC from coral, but little is known about its biodegradation in coral and its impact on coral microorganisms. To study the diversity of EHMC biodegradation in coral, we collected coral samples from Luhuitou, Sanya. These samples were enriched multiple times with EHMC as the sole carbon source to obtain EHMC-tolerance bacteria. High-throughput sequencing technology was used to analyze the composition and diversity of bacteria communities from enrichment samples. Besides, potential EHMC-degrading strains were isolated and identified from the enrichment through activity tests. High-throughput 16S rRNA gene sequencing revealed that the microbial community diversity in coral samples of Porites lutea, Favosites sp. and Acropora sp. was reduced under high concentration of EHMC. In contrast to their low abundance in the original coral samples, Agromyces, Paracoccus, Pelagibaca and Erythrobacter were the dominant genera after multiple enrichment with EHMC. Furthermore, a total of 60 bacterial strains were isolated from the EHMC-enriched samples. Based on 16S rRNA gene identification, these strains belonged to three phyla, three classes, six orders, eight families, thirteen genera and seventeen species. The main dominant genera among the cultivable bacteria were Bacillus, followed by Rhodococcus, Paracoccus, Exiguobacterium and Acuticoccus. Moreover, eight potential EHMC-degrading strains were selected through activity tests, belonging to Bacillus, Brevundimonas, Paracoccus, Acuticoccus, Phycicoccus, Rhodococcus and Mycolicibacterium, respectively. Previous studies have shown that Rhodococcus, Bacillus and Paracoccus were correlated with the biodegradation of aromatic compounds. This study illustrates the impact of EHMC on coral microbial communities and isolates potential EHMC-degrading bacteria, providing valuable information for coral resilience against organic UV filters. Additionally, it accumulates valuable bacterial resources for eliminating organic contaminants in coral by the subsequent construction of coral probiotic consortium.

In order to discover the novel and bioactive secondary metabolites, the soft coral-associated symbiotic and epiphytic fungi Aspergillus terreus EGF7-0-1 were fermented in rice media. The secondary metabolites were isolated using various chromatographic technologies, yielding eight γ-aromatic butenolide lignans. Based on nuclear magnetic resonance (NMR), high resolution electrospray ionization mass spectroscopy (HR-ESI-MS) and comparison with the literature, their structures were determined to be butyrolactones I−V (1−5), aspernolide E (6), asperteretal D (7) and terrusnolide A (8). In this study, the inhibitory activity of these compounds against TDP1 (Tyrosyl-DNA phosphodiesterase 1) in vitro was studied for the first time, but it was unfortunate that compounds 1−8 did not show any inhibitory abilities against TDP1. This study provides theoretical data for the discovery of TDP1 inhibitors.

To explore the diversity of secondary metabolites of fungus Aspergillus sp. GXIMD 02045 from Sargassum fusiforme, the secondary metabolites were separated with various chromatographic techniques. Chemical structures were identified using mass spectroscopy, nuclear magnetic resonance spectroscopy, and optical rotation data with comparison of literature reported ones. 15 compounds were isolated from Aspergillus sp. GXIMD 02045, and identified as (3S)-6-hydroxy-8-methoxy-3, 5-dimethylisochroman (1), (3S)-6-hydroxy-8-methoxy-3-methylisochroman (2), (3S, 4R)-6-hydroxy-8-methoxy-3, 5-dimethylisochroman (3), (1S, 3R)-3, 7-dimethyl-1, 8-dihydroxy-6-methoxyisochroman (4), (S)-6-hydroxy-7-methoxy-3, 5-dimethylisochroman-1-one (5), anserinone A (6), anserinone B (7), (+)-formylanserinone B (8), 4-hydroxyphenylacetic acid (9), p-hydroxyphenylacetic acid methyl ester (10), Waol A (11), (S)-7-methoxy-2, 5-dimethyl-2, 3-dihydrobenzofuran-6-ol (12), 6-methylcurvulinic acid methyl ester (13), 4-hydroxy-3, 6-dimethyl-2-pyrone (14), trans-ferulic acid (15). Antibacterial activity of secondary metabolites from A. sp. GXIMD02045 was tested, which showed that compounds 6−8 displayed inhibitory activity against methicillin-resistant Staphylococcus aureus, and the minimum inhibitory concentration (MIC) values were ranging from 3.91 μg·mL^-1 to 7.81 μg·mL^-1. Compounds 6−8 and 11 showed inhibitory activity against Bacillus subtilis, and the MIC values were ranging from 7.81 μg·mL^-1 to 15.62 μg·mL^-1. Compounds 4, 6−8, 10 and 11 showed inhibitory activity against Pseudomona aeruginosa, and the MIC values were ranging from 1.95 μg·mL^-1 to 125.00 μg·mL^-1. This study provides a theoretical basis for the research on development and utilization of mangrove Sargassum fusiforme and its symbiotic fungus.

Karenia harmful algal blooms occur frequently worldwide, attracting extensive attention from countries around the globe. Karenia hui, identified as a new species of the genus Karenia in 2024, has been found to be lethal to Oryzias melastigma. Research on this species is currently quite limited. This study investigated its growth characteristics, acute toxicity on Artemia salina, and hemolytic activity at different growth stages. This study aims to reveal the growth curve of K. hui, its toxic effects, and changes in hemolytic activity. The results indicated that K. hui had a unique growth cycle. After the initial exponential growth period and the stable period, it entered the exponential growth period and the stable period again. Karenia hui possessed acute toxicity to Artemia salina, with the death rate of Artemia salina being positively correlated with the density of the algae and increasing with exposure time. In the study of the acute toxicity of K. hui at different growth stages to Artemia salina, the toxicity was the highest on day 23 of the initial stationary phase. The specific death rate of Artemia salina reached its peak at (0.22±0.03)h^-1 within 24 hours, and the death rate after 72 hours reached (98.33±4.08)%. The hemolytic activity of K. hui increased during the first exponential growth phase and reached its peak at the end of this phase (14.43×10^-6 HU·cells^-1). It began to decline during the first stationary phase, and remained low during the second exponential growth phase and stationary phase (0.31×10^-6 HU·cells^-1). The results of this study can provide a foundation for assessing and mitigating the potential ecological risks posed by K. hui blooms.

Coastal wetland restoration is an important measure to improve the blue carbon function in the coastal zone. Zhejiang Province has continuously carried out a series of large-scale mangrove introduction and afforestation projects. Yet, the carbon sink capacity and influence of factors for the high-latitude artificial mangroves still remain unclear. In this study, the soil organic carbon (SOC) content, organic carbon stock per unit area and their vertical distribution characteristics of the Kandelia obovata forests with different ages were investigated. The SOC content and stock in the mangroves were also compared with the Spartina alterniflora salt marsh and bare mudflat. The results showed that the SOC content and stock were the highest in the adult mangroves. The SOC content and stock in both mangroves and salt marshes were significantly higher than those in the mudflat. The SOC content in salt marshes was higher than that in the young mangroves, but due to the significant lower bulk density of Spartina alterniflora salt marsh soils compared to young mangrove forests, the SOC stock in the young mangroves was slightly higher than that of salt marshes. The SOC content and stock in the different habitats showed the distribution characteristics of first increasing and then decreasing with the soil depth, reaching the highest values at the soil depth of 20~50 cm. Site location and habitat type had a significant relationship with SOC content and stock, with significant interaction between site location and habitat type. Dissolved oxygen in pore water, soil total nitrogen, soil pH and pore water salinity were significantly associated with the SOC content. The results of this study can provide scientific basis and data support for assessing the carbon sequestration potential of artificial mangrove forests after northward migration, as well as wetland protection and restoration strategy.

The seaweed bed composed of macroalgae serves as a vital biological habitat in the coastal rocky zone and plays an ecological role as coral reefs, mangroves, seagrass beds and salt marshes do. Additionally, it constitutes a significant component of blue carbon. This study exemplified the Hainan Eucheuma Reserve to investigate and evaluate the distribution characteristics and carbon storage capacity of seaweed in this area, while establishing an investigation and evaluation method for Hainan's seaweed bed carbon storage. The results showed that the average coverage of macroalgae in the subtidal zone reached 50%. There were 34 species of macroalgae in 23 genera, and the dominant species were Zonaria diesingiana, Sargassum polycystum etc. The average biomass of marcoalgae was 267.75 g·m⁻². The dry-wet ratio of the collected macroalgae was 11.58%~43.54%, and the organic carbon content was 14.25%~39.19%. As a result, the carbon storage of seaweed in the Hainan Eucheuma Reserve was (2252.77±19.37) Mg C, and average carbon density of seaweed bed was (0.49±0.004) Mg C·hm⁻².

The orientation and intensity of fracture are important information for studying anisotropy, but they are difficult to identify through the conventional compression wave (P) of seismic data. In contrast, the shear wave splitting (SWS) caused by azimuth anisotropy in the converted seismic wave (PS) is helpful to characterize the strength and azimuth of fractures. In order to study the distribution characteristics of fractures in the Xihu Sag of East China Sea, the converted shear wave information recorded in four-component submarine nodes (ocean bottom nodes, OBN) was used to conduct SWS analysis. First, the principle of SWS and the layer-stripped method were introduced in detail. Then, the SWS analysis with the seismic data in the study area was carried out. The results show that in the shallow layer (0~3000 ms), the time delay of fast and slow shear waves is 3~5 ms, the average fracture direction is about 111°-117°, and the fracture similarity is as high as 80%~90%, which indicates that the fracture orientation is relatively concentrated. However, in the deep layer, the distribution of fracture is rather complex, for which the time delay is about 6~8 ms and the main azimuth is concentrated at 119°, but the fracture similarity is low (less than 50%) and the fracture direction is about 20°−40°, which indicates that the azimuth is not concentrated. The results show that NW-trending fractures are mainly developed in the shallow layer of the study area, and NW- and NE-trending fractures are mainly developed in the deep layer, which is consistent with the fault development directions obtained from the P results in the study area. The time delay gradually increases from the shallow to the deep part, indicating that the deeper the layer, the more intense the fracture develops. The time delay in the south of the study area is significantly higher than that in the north, indicating that the intensity of fracture in the south is higher than that in the north.

The marine engineering survey focuses on the geological hazards that threaten the marine engineering. In the process of moving towards the deep water, it has also been found that several unique geological phenomena, distinct from shallow water areas, have a certain impact on the positioning of drilling platforms, the design of jacket platforms and floating platforms, and the optimization of submarine pipeline and cable routes. Based on the results of many deepwater well site surveys and deep-water oil and gas field development project surveys, this paper expounds the characteristics of deep-water geological hazards, the methods of research and evaluation and the impact on marine engineering through the results of engineering geophysical survey, engineering geological survey and marine environmental survey, and provides a better idea for the investigation and design of deep-water marine engineering. The researches show that the deep water is widely developed with sand waves, scarps, hard seabed, faults, submarine canyons, mass transport deposits and other geological disaster phenomena. When conducting engineering geophysical survey, the use of autonomous underwater vehicle (AUV) and other survey methods to obtain centimeter resolution survey results can effectively reduce the observation period of seabed sand wave movement rate, and obtain more accurate water depth topographic data to support the marine engineering design. Combined with the shallow soil sample results and shallow profile results of the engineering geological survey, the seabed strata can be effectively divided and the slope stability analysis can be carried out, providing the design basis for the offshore engineering construction.

With the growing global demand for clean energy, hydrogen energy, as an important renewable energy reserve, has garnered widespread attention for its storage technology. Onshore hydrogen storage systems pose risks such as hydrogen leakage, drinking water contamination, and catastrophic injuries. In contrast, offshore geological environments are relatively stable and well-sealed, leading to widespread attention to and rapid development of offshore hydrogen storage technology. Currently, the main underground gas storage technologies include salt caverns, aquifers, and depleted oil and gas reservoirs. Salt cavern gas storage has been operating for many years in Europe and the USA and has a relatively mature technical foundation. However, there are no suitable locations for constructing salt caverns along China’s coast, which limits the build-up of salt cavern hydrogen storage to inland regions. However, China’s coastal areas have abundant underground aquifers and oil and gas reservoirs, necessitating timely related geological research to promote the development and application of relevant technologies in different marine areas and the comprehensive development of the hydrogen energy industry. Developing offshore hydrogen storage technology requires not only integrating the unique geological conditions of the margin with the special physical and chemical properties of hydrogen, but also considering geological, hydrological, biochemical, and mineralogical factors to ensure a rational planning and safe operation, in addition to using the latest geophysical methods in site selection. Looking ahead, offshore hydrogen storage technology will not only provide theoretical support for the development of renewable energy technologies in China but also play a significant role in promoting a low-carbon, green, and sustainable development.

With the goal of low-cost and high-accuracy estimation of Chlorophyll-a (Chl-a), a model for estimating Chl-a in the surface layer of the Western South China Sea (WSCS) was constructed in this study. Using the data from the WSCS cruises in the past ten years, and based on the influence of changes of hydro-meteorological conditions and their contribution to the oceanic biochemical processes, the hydro-meteorological parameters (HMPs) were used as the input data of the random forest (RF) algorithm. To evaluate the reliability of estimating Chl-a based on HMPs, the quasi-analytical algorithm (QAA) was used to derive the in-situ remote sensing reflectance (R_rs) based on the measured inherent optical property parameters. Then Chl-a was estimated and evaluated by the combination of classical empirical algorithms for water color products such as Ocean Color 4 (OC4), Aiken and Tassan, and the evaluation results showed that the OC4 algorithm had the highest estimation accuracy, with an R² of up to 0.438. The comparison with the R² of 0.568 of the RF-based model shows that, owing to the large data volume of HMPs, the Chl-a estimation results of the RF model based on HMPs show much better stability and generalization, and better spatial distribution consistency with the measured results. It was found in study of the importance of feature parameters that in the machine learning model for estimating Chl-a based on HMPs, salinity is the most important feature variable, followed in turn by temperature, wind and air pressure, and the lowest contributor is relative humidity.

The special geomorphological structure of coral reefs causes most of the incident waves to break at the reef edge, thus effectively reducing the intensity of waves on the reef apron and protecting the coastal area. However, the increasing human activities on the reefs, such as coral sand blowing and shore defense construction, not only threaten the fragile ecosystems of the reefs, but also significantly affect the complex wave evolution characteristics of the reefs. Nowadays, the construction of islands and reefs is facing the dual needs of promoting the ecological restoration of islands and reefs and improving the characteristics of wave protection and resistance of islands and reefs. Based on a physical model test, this paper systematically investigates the evolution of solitary wave hydrodynamic characteristics of island reefs with the existence of artificial ecological reef groups and analyzes the influence of wave height, water depth, reef body opening diameter and other factors. The experimental results show that the existence of artificial ecological reefs will have a significant impact on the propagation and evolution characteristics of island-type solitary waves. There is a complex interaction between the incident wave and the artificial reef, and the presence of the reef enhances the reflective strength of the incident wave. In addition, the complex vortex field inside the artificial reef body will consume more incident wave energy, resulting in a lower transmission coefficient of the incident wave on the reef pads, which better protects the coast.

In this paper, the FUNWAVE-TVD (fully nonlinear wave model with total variation diminishing) numerical model based on the two-dimensional horizontal Boussinesq equations was used to simulate the wave propagation and run-up near a three-dimensional barrier reef. Firstly, the model was verified by existing physical experiments. Subsequently, the effects of different reef widths, gap widths and gap locations on wave transformation and run-up around the three-dimensional barrier reef were analyzed. The results show that the existence of reefs can effectively reduce the impact of solitary waves. As the width of the reef increases, wave height decreases more rapidly, and wave run-up around the whole island drops continuously. The values of run-up near the leeward side are very small and exhibit some variability. The run-up decline due to reefs around the central island coastline decreases as the reef width increases. As the gap width increases, the extend of wave height increase in the lagoon near the gap increases. The influence of the gap width on the run-up is evident within a certain range on the windward side of the central island. As the gap width increases, the run-up on the windward side of the central island increases in this area, and the maximum run-up shifts from bimodal to unimodal. Outside this range, wave run-up is almost unaffected by the gap width. As the angle between the direction of the incident wave and the gap increases, the extent of wave height increase in the lagoon near the gap decreases. Moreover, the change of the gap location only affects the run-up in the region close to the gap of the central island, and this affected region shifts towards the back of the gap as the angle between the direction of the incident wave and the gap increases.

Data of significant wave heights (SWHs) is the basis of the investigations of tropical cyclone (TC) wave forecasting and retrieval technology. Based on the high-precision SWHs observed by the wave spectrometer of Surface Waves Investigation and Monitoring (SWIM) on board the China-France oceanography satellite (CFOSAT), this paper corrected the underestimation error of the SWHs under high sea state from the fifth generation reanalysis (ERA5) of European center for medium-range weather forecasts (ECMWF), providing a reliable support for the construction of a TC SWHs dataset with high accuracy and large sample quantity. Firstly, due to the temporal and spatial resolution differences between ERA5 and SWIM data, this paper utilized the latitude and longitude transformation and the inverse distance weighting method of spatial interpolation to match the two data spatially and temporally. Then, the correlation relationship that the ERA5 error increases with the increase of SWIM SWHs was obtained through data comparison. Based on this relationship, a reconstruction equation from ERA5 to SWIM was constructed using the linear regression method. Finally, the reconstruction equation was validated using the data from two (USA) National Data Buoy Center (NDBC) buoys. The results showed that for waves higher than 5 m, the Root Mean Square Error (RMSE) of the ERA5 SWHs reduced from 1.65 m and 1.08 m before the reconstruction to 1.18 m and 0.71 m after it, respectively, proving the effectiveness of the reconstruction equation.

In order to investigate the secondary metabolites of the fungal-bacterial symbiont Aspergillus spelaeus GXIMD 04541 / Sphingomonas echinoides GXIMD 04532 derived from Mauritia arabica, a series of isolation and purification techniques, including silica gel chromatography, gel column chromatography, and semi-preparative high performance liquid chromatography (HPLC), were employed. The structures of compounds were identified by spectroscopic analysis and literature comparison. Cytotoxic activity evaluation of compounds was conducted using the MTT (Methylthiazolyldiphenyl tetrazolium bromide) assay. Consequently, seven compounds were obtained from rice fermentation extracts of symbiont GXIMD 04541 / 04532, which were identified as trichalasins C (1), aspochalasin E (2), aspochalasin H (3), aspochalasin I (4), aspochalasin K (5), citreofuran (6), and cyclothiocurvularin B methyl ester (7). Activity assays demonstrated that compounds 2, 4, and 5 exhibited cytotoxic activity against PC3 cells, with IC₅₀ (half maximal inhibitory concentration) values of 17.23, 15.18 and 8.71 μmol·L^-1, respectively. However, compounds 1-5 showed no cytotoxicity against 22Rv1 cells.

In order to identify secondary metabolites and analyze the corresponding biosynthetic gene clusters, the strain GXIMD 03502, isolated from the mangroves in Hainan, was studied. The strain was identified by comparing the 16S rDNA sequence. The secondary metabolites were separated by various chromatographic separation techniques, and their structures were determined by spectral data analysis and literature comparison. Five 2-hydroxyphenylthiazoline derivatives were isolated from this strain and identified as (+)-(S)-pulicatin G (1), pulicatin A (2), aerugine (3), pulicatin F (4), and (+)-(S)-dihydraeruginoic acid (5). At the same time, the genomic DNA of the strain was obtained by Illumina novaseq 6000 sequencing technology. The bioinformatic approach was employed to annotate the biosynthetic gene cluster and deduce the biosynthetic pathways of the compounds. The analysis results of the whole genome DNA sequence indicated that it contained 31 secondary metabolic biosynthetic gene clusters, and revealed that cluster 11 may be responsible for the biosynthesis of 2-hydroxyphenylthiazoline derivatives. This study provided a mangroves-derived S. ardesiacus GXIMD 03502 to produce 2-hydroxyphenylthiazoline derivatives, and the whole genome sequence of this strain laid a foundation for the exploration of its secondary metabolites.

This paper investigated the chemical constituents of Penicillium sp. G5A-11, which was isolated from a sponge in the South China Sea, and their cytotoxicity. Various separation methods, including thin layer chromatography, silica gel column chromatography, gel column chromatography, and semi-preparative high-performance liquid chromatography, were used to isolate compounds from solid-rice culture of this marine derived fungus. Spectroscopic data, along with physical and chemical properties, were utilized to identify the structures of the isolated compounds, and compared with literature data. Their cytotoxic activities were tested by the MTT (methylthiazolyldiphenyl-tetrazolium bromide) method. Seventeen compounds were identified from the marine fungus Penicillium jiangxiense, including N-acetyltryptamine (1), methyl 2-(6-hydroxybenzothiazol-4-yl) acetate (2), R-mevalonolactone (3), nicotinic acid (4), altechromone A (5), 2, 5-dimethy-7-hydroxychromone (6), methyl 7-hydroxy-2-methylchromone-5-carboxylate (7), stagonoculiepine [(2S, 5R)-1-formyl-1, 2, 3, 4-tetrahydro-5H-2, 5-epiminobenzo[b]azepin-5-yl acetates] (8), (4R, 5S)-5-(hydroxymethyl)-5-methyl-4-(3-oxobutyl) dihydrofuran-2(3H)-one (9), 9α-hydroxy-1, 2, 3, 4, 5, 10, 19-heptanorergosta-7, 22-diene-6, 9-lact (10), 3β, 5α, 9α-trihydroxy-(22E, 24R)-ergosta-7, 22-dien-6-one (11), ergosterol peroxide (5α, 8α-epidioxy-24(R)-methylcholesta-6, 22-dien-3β-ol) (12), (22E, 24R)-24-methylcholesta-2, 22-diene-3β, 5α, 6β-triol (13), ergosterol (14), stigmasterol/β-sitosterol (15), 3β, 5α-dihydroxy-(22E, 24R)-ergosta-7, 22-dien-6-one (16), and 3β, 5α-dihydroxy-6β-methoxyergosta-7, 22-diene (17). Among them, compounds 7 and 9 were new natural products. Cytotoxic activity tests showed that compound 10 was moderately cytotoxic to human chronic myeloid leukemia cells (K562) and human gastric cancer cells (SGC-7901) with IC₅₀ values of (12.07 ± 0.12) μmol·L^-1 and (13.17 ± 0.02) μmol·L^-1, respectively. However, the results of the anti-inflammatory activity test revealed that none of the compounds exhibited anti-inflammatory activity.

Blood cells, as the main immune effector cells, play a very important role in the immune defense system of shellfish. The morphology, type and phagocytosis function of hemocytes of Spondylus sp. were studied by means of blood cell count, Giemsa staining, transmission electron microscopy, scanning electron microscopy and fluorescence phagocytosis. The results showed that the blood cell density of the Spondylus sp. was 3.296 × 10⁶ cells·mL^-1, and the blood cells differ significantly in size and with regard to whether they contain particles within the cytoplasm. Based on these differences, they are subdivided them into four types: hyalinocyte (9.74%), granulocyte (58.14%), agranular haemocyte (27.50%) and lymphoid (4.62%). Hyalinocytes, agranular haemocytes, granulocytes and lymphoids could be observed under transmission electron microscope. Under the observation of scanning electron microscope, four different types of cells can be clearly distinguished, which are oval cells, round cells, spindle cells, nucleated (conical) cells. A phagocytosis experiment was carried out with Escherichia coli BL21 labeled with the green fluorescent protein (GFP), and the results showed that the phagocytosis of the blood cells from Spondylus sp. was mainly dependent on granulocytes.

Hymenocera picta is popular in the aquarium market due to its attractive coloured pattern of the body and special feeding behavior on starfish. For this reason, observations and records have been made on the reproductive habits, reproductive cycle and embryonic development of harlequin shrimp. The results showed that the mating behavior of the broodstock was dominated by males in four main stages of contact, climb and straddle, spermatophore transfer and separation. Egg spawning occurred 2 hours after mating. Under the temperature of (27 ± 0.5) ℃, embryos developed in 14 to 15 days, going through 8 stages of fertilized egg, cleavage, blastula, gastrula, pre-nauplius, post-nauplius, membrane-zoea and pre-hatching until larvae hatched. Females molted within 12 to 24 hours after larvae hatching and began mating again within 2 hours, and then entered the next breeding cycle. Our results provide not only a better understanding of the reproductive biology in Hymenocera picta, but also a useful reference for its artificial breeding practices.

Species of the genus Hansarsia play crucial roles in marine planktonic ecosystems, but there is often confusion and misidentification. This paper employed morphological analysis methods to conduct in-depth research on the specimens of the genus Hansarsia collected by the Marine Biodiversity Collections of the South China Sea, Chinese Academy of Sciences, from the South China Sea and the East Indian Ocean, aiming to clarify differences between species and resolve taxonomic confusions. This paper a) supplemented and revised the characterizations of H. tenella, H. gracilis, H. microps, and H. atlantica; b) depicted the changes in the first and second thoracic legs of the four species from juvenile to adult; c) pointed out the phenomenon of two rostrum shapes in the adult H. gracilis, and the variation in the number of setae on the propodus of the first thoracic leg; and d) clarified the distinctions between H. microps and H. atlantica in the South China Sea and the East Indian Ocean.

An artificially bred protocol, developed for wild Gnathanodon speciosus, also named as golden trevally, was presented in this study. The embryonic development and growth process of the fish was also introduced. The wild fish were domesticated from 2017 to 2023. The fertilized eggs laid by naturally matured fish were transparent and buoyant. Single oil globule ((0.23 ± 0.02) mm in diameter) was observed in the yolk sac of eggs ((0.85 ± 0.04) mm in diameter). The number of eggs per gram was (3197 ± 210). The embryonic development went through six stages: cleavage, blastocyst, gastrulation, neuroblast, organogenesis and hatching. The hatching of fertilized eggs took 17 h 17 min and the hatching rate was 94.95% in sea water (salinity 30‰, pH 8.0 ~ 8.2, DO 6.05 ~ 7.13 mg∙L^-1) at (18 ± 0.5) ℃. The ecological accumulated temperature was 483.84 ℃·h. The body length of newly hatched larvae were (2.01 ± 0.14) mm. The nurture of fish fingerlings went through four stages: early larval, late larval, juvenile and fingerling, and took 45 dph with a 32.62% survival rate in sea water (salinity 26‰~32‰, pH 7.8~9.0, DO 4.90~7.50 mg∙L^-1) at (29.5 ± 2.0)℃. The transformation from juvenile to fingerling fish was completed at 26 dph. At 45 dph of growth, the fingerling fish ((51.05 ± 4.81) mm in body length) were similar to adult fish in body shape and color. This study indicated that the golden trevally grew and spawned naturally in artificial bred condition and could be artificially reproduced.

RAD-seq technology was utilized to develop 10 pairs of novel polymorphic microsatellite primers for assessing genetic 有时候diversity in nine populations of Sinonovacula constricta of Dandong in Liaoning (DD), Qinhuangdao in Hebei (QHD), Zhuanghe in Liaoning (ZH), Qindao in Shandong (QD), Lianyungang in Jiangsu (LYG), Ningbo in Zhejiang (NB), Xiamen in Fujian (XM), Huizhou in Guangdong (HZ), and Beihai in Guangxi (BH). In 270 individuals of S. constricta, a total of 352 alleles were detected. The average number of alleles (N_a) ranged from 3.2000 to 4.3000, with the average effective number of alleles (N_e) falling between 1.8789 and 2.5433. Observed heterozygosity (H_o) varied from 0.0000 to 0.9667, with an average ranging from 0.3088 to 0.5533. Expected heterozygosity (H_e) spanned from 0.0000 to 0.7945, with an average of 0.3456 to 0.5715. The average polymorphic information content (PIC) ranged from 0.3373 to 0.5989. Genetic diversity analysis indicated a moderate level of genetic diversity across the nine populations of S. constricta. The genetic differentiation coefficient (F_st) among populations ranged from 0.0547 to 0.3511, with the lowest F_st value observed between QHD and ZH (0.0547) and the highest between LYG and BH (0.3511). Gene flow (N_m) values ranged from 0.4620 to 4.3204, with the highest N_m value recorded between QHD and QD (4.3204) and the lowest between LYG and BH (0.4620). AMOVA analysis revealed that 33.04% of the total genetic variation existed among populations (p < 0.01), while 66.96% was within populations (p < 0.01), indicating that the genetic variation was observed not only among individuals but also among populations. However, the variation among individuals was greater than that among populations. Consistent results were obtained from UPGMA clustering, Structure clustering, and principal coordinate analysis (PCoA). The study delineated three main groups among the nine populations: the first group comprised QHD, ZH, QD and DD populations; the second group included LYG, NB, XM, and HZ populations; and the third group was independently represented by BH population.

Sargassum hemiphyllum var. chinense J. Agardh is an economic seaweed widely distributed along the coast of the South China Sea. To investigate the sexual reproductive characteristics and the feasibility of artificial seedling propagation of this brown macroalga, this study employed optical microscopy to examine the morphological features of the thallus, male and female receptacles, and the early developmental stages of fertilized eggs in S. hemiphyllum var. chinense from Naozhou Island. The results revealed that the mature thallus of this Chinese variant exhibited a yellow-brown hue with a height of 0.8 to 1 m. It exhibited dioecious traits and possessed discoid holdfasts composed of repetitive bifurcations. The female receptacles were yellow-brown and cylindrical, adorned with numerous surface spines, measuring (0.46 ± 0.05) mm in diameter and (2.50 ± 0.67) mm in length. Conversely, the male receptacles were lighter in color, adopting a rod-like morphology, with a diameter of (1.01 ± 0.18) mm and a length of (9.21 ± 2.36) mm. Eggs released from the female structures exhibited an eight-nucleate one-egg configuration, either ellipsoidal or oval, with an outside diameter of (76.32 ± 10.11) μm. Following ovulation, these eggs adhered to the female structures awaiting fertilization. Sperms released from the male structures were pear-shaped, measuring (27.52 ± 5.43) μm in length and equipped with flagella. At the post-fertilization stage, the majority of fertilized eggs detached from the receptacles, affixing to substrates and undergoing early developmental processes. Within six hours, these fertilized eggs underwent their initial transverse division, subsequently progressing through multiple transverse and longitudinal divisions, and ultimately culminating in the development of landmine-shaped sporophytes within 24 hours, with primary fronds emerging after 28 days. Additionally, this study investigated the indoor use of suitable artificial substrates for the germination of sporophytes and the effect of temperature on the S. hemiphyllum var. chinense growth. Results indicated that, after seven days of culture, the mesh curtain yielded a germination rate of (7.25 ± 3.64) sporophytes per cm², measuring (1.38 ± 0.35) mm in sporophytes’ length. Additional indoor suspension culture experiments revealed a 90% survival rate of sporophytes at the optimal temperature of 25℃, with a thallus growth rate of 90.1 μm·d⁻¹, significantly outperforming other temperatures. These findings provide valuable preliminary data on which to base further studies of the early development and large-scale artificial seedling propagation of S. hemiphyllum var. chinense, thereby facilitating the rapid establishment of natural Sargassum habitats in coastal regions and contributing to the swift rehabilitation of China’s nearshore marine ecosystems.

This study investigated the impacts of algae-fish interactions on wastewater purification in a recirculating aquaculture system, with and without the high-temperature resistant Gracilaria spp. as the experimental alga. The effects of Gracilaria spp. on the quality of the system wastewater and the growth performance of the hybrid pearl gentian groupers (Epinephelus fuscoguttatus^♀ × E. lanceolatus^♂) were examined. The results showed that the presence of Gracilaria spp.. 1) improved wastewater quality and reduced the concentrations of ammonia nitrogen, nitrite, and phosphate in the wastewater in the grouper culture bucket by 5.05%, 98.81%, and 69.26%, respectively, compared with the control group without Gracilaria spp., and 2) promoted the growth performance of the groupers, with their weight gain rate and survival rate in the experimental group increasing by 2.10- and 1.69-fold (to 67.37% and 96.43%), respectively, compared with the control group. In addition, the Gracilaria spp. grew rapidly in the experimental treatment. Their specific growth rate was more than 3%·d^-1 and their wet weight was more than 1.5 times as much during the culture experiments. We also conducted a Granger causality test. Our results confirmed that the addition of Gracilaria spp. to a recirculating aquaculture system should reduce the ammonia nitrogen concentration and increase the biomass and survival rate of the groupers. The study showed that a recirculating aquaculture system not only enhanced the mutualistic relationship between algae and fish but also efficiently improved water quality, potentially leading to further development and application of multi-level integrated aquaculture models.

In this study, we explored the changing characteristics of spatial patterns of lime-sand islands in the Xisha Islands under the impacts of typhoons and their driving factors, which are of great significance to the ecological protection and sustainable development of lime-sand islands in the South China Sea (SCS). First, to determine the area of the BeiDao, ZhongDao and Nandao islands of the Xisha Islands and their beaches, the toe of beach line (ToB) and the boundary of vegetation were extracted using the gradient vector flow-snake (GVF-snake) model based on Sentinel-2 remote sensing images. The monthly average area of the study islands from 2016 to 2022 was examined using the change point detection method, and the typhoon events that had caused significant changes in the size of the study islands were identified. Finally, the spatial and temporal characteristics of the islands affected by typhoons were analyzed based on the changes in lime-sand islands area, vegetation area, beach area and normalized difference vegetation index (NDVI) during typhoon events. The results are shown as follows. 1) The vegetation of the islands was mainly slightly stressed by the typhoons, and the severely stressed areas were mainly located along the shorelines. The typhoons caused a significant retreat of the vegetation boundary of the islands, and the sediments were stripped off with the damaged vegetation and washed to the beach with the wind and waves, resulting in the seaward advancement of the ToB line. The windward coasts were the first to be impacted by the direction of the typhoon path, and the vegetation along the windward side of the islands was heavily damaged, resulting in more significant changes in vegetation, vegetation boundary, and the ToB line on the windward side. 2) As the vegetation along the lime-sand islands was damaged, the retreat of the vegetation boundary line and the seaward advancement of the ToB line resulted in the expansion of the beach area, whereas after the typhoon, due to the loss of vegetation fixation, the loose sediment accumulated on the beach was transported away from the islands to the reef flats by the wind and wave action, resulting in the reduction of the beach area. Therefore, coastal vegetation that buffers and fixes the sand is critical to the stability of lime-sand islands. 3) Increased typhoon wind speeds and shorter distances between typhoon paths and the islands, as well as increased surface currents during the typhoon, made the islands exposed to extreme wave and storm currents, which led to an increase in the area of severely damaged vegetation on the islands, resulting in greater shoreline movement and changes in beach area. In addition, typhoons can cause sediment transport between the lime-sand islands and their surroundings, which can directly change the beach area and morphology of the lime-sand islands. The loss of large amounts of unconsolidated sediments on the lime-sand islands after the typhoon, which led to an abrupt decrease in the size of the islands, together with the decrease in the rate of biogenic carbonate production due to global warming and the insufficient supply of sediments from the surrounding environment, may be the reasons for the long-term decreasing trend in the size of the lime-sand islands in the Xisha Islands.

The Weizhou Oilfield in Beibu Bay, South China Sea, has a complex structure, developed faults and fractured strata, resulting in a non-uniform velocity structure. To meet production requirements, this area has undergone multi-round traveltime tomography velocity modeling, including velocity modeling of dual-azimuth streamer seismic data. However, imaging quality remains poor. Full waveform inversion (FWI) builds a more accurate velocity model by making full use of the amplitude and traveltime information of the seismic wavefield. However, this process usually requires that the seismic data contain long offset components. Given the limited offset of streamer seismic data in the Weixi exploration area, this paper develops a high-precision velocity modeling technique process that combines FWI and traveltime tomography. Firstly, multi-scale FWI from low to high frequency is used to invert shallow and intermediate layer velocity models derived from high-SNR turning and refracted wave signals. Reflection traveltime tomography is then used to update the deep-layer velocity model. Compared to conventional reflection traveltime tomography modeling, the accuracy of the velocity model is improved, which in turn improves the structural imaging of the target area, making the fault structure more discernible. This work lays a solid data foundation for the oilfield to increase storage and expand production and realize benefit exploitation.

Submarine landslides, as a natural disaster with immense destructive potential and widespread distribution worldwide, often pose significant threats to the safety of human lives. The massive waves generated by these landslides can cause severe damage to marine structures. Therefore, rapidly predicting and assessing the size of the waves generated by underwater landslides is a crucial part of disaster prevention and mitigation efforts, essential for the development and utilization of marine resources, as well as for the safety of human lives and properties. In this study, numerical simulations of landslide-generated waves were conducted using the non-hydrostatic wave model NHWAVE (a non-hydrostatic wave model) to obtain wave data for different types of landslides. Subsequently, a CONV1D (1-dimensional convolutional neural network) was trained as the prediction model for landslide-generated waves. The model was trained using datasets for various monitoring points and different types of landslides, and evaluation metrics such as mean squared error were employed to assess the prediction performance of the convolutional neural network. The results indicate that, under the condition of using a limited amount of data, the convolutional neural network can effectively learn the patterns of landslide-generated waves. Moreover, it can predict reasonably well even for features that are not uniquely present in the dataset, demonstrating good generalization capability. Once the model is trained, inputting real-time water level data from the location of the landslide occurrence enables the neural network to predict the temporal wave profiles at downstream monitoring points in a short time. By using neural networks for prediction, it is possible to assess disasters in advance and take timely and effective response measures.

The key environmental factors (nutrients, chlorophyll a (Chl a), chemical oxygen demand (COD), etc.) and eutrophication indexes were investigated in the surface water around the Nan’ao Island in 2022. The seasonal change of nutrients concentration was significant, which gradually declined from northwest to southeast in the surrounding region of the island. The nutrients concentration was significantly higher in winter than in other seasons. During summer, the nutrients concentration was high near the Qin’ao Bay, which possibly originated from the discharge of domestic wastewater. The highest dissolved inorganic nitrogen (DIN) was found near the estuary of the Rongjiang River and the highest dissolved inorganic phosphorus (DIP) was found near a net cage aquaculture zone in the Zhelin Bay. This phenomenon suggested that the river input increased the nitrogen loading and the cage aquaculture increased the phosphorus loading in this region. The seawater showed high Chl a and low nutrients in summer, suggesting the strong bio-assimilation effect of phytoplankton on the nutrients. The structure of nutrients was generally balanced, and no absolute limitation was detected for nitrogen, phosphorus or silicate. Nitrogen nutrients were relatively limited in the offshore region in autumn. According to the eutrophication index (EI), nutrient quality index (NQI) and trophic index (TRIX), the highest eutrophic status was generally located in the Zhelin Bay and the Rongjiang River estuary. However, the region near the Qing’ao Bay showed high eutrophic status in summer. With the rapid development of tourism, the influence of domestic wastewater should be paid more attention to in the Nan’ao Island. The eutrophication indices showed a significantly positive correlation with DIN and a negative correlation with salinity. River discharge should be the main reason for water eutrophication in this region. The eutrophic status could be much underestimated using the EI index for waters with low nutrients and high chlorophyll during summer. The results contribute to a better understanding of the water quality status around the Nan’ao Island and provide basic data for environment management and marine resource utilization.

This paper reviews the basic concepts of data security governance, summarizes the current status and challenges for data security in marine science in China, points out its basic characteristics, and extracts possible security risks for security process areas in the data life cycle. With the whole life cycle of marine scientific data as the core, a data security governance framework is constructed from three levels of governance objectives, security capabilities and governance systems, and specific security strategies are proposed, which provide theoretical support and practical reference for improving the security governance capabilities of data centers in marine science in China.