To investigate the trophic structure characteristics of the main fish species in the coral reefs of the Nansha Islands, twenty three fish species were collected from waters of the Yongshu Reef and Meiji Reef during the spring of 2023, and the stable isotopes of carbon and nitrogen of fish were measured and used to analyze their trophic structure, and a trophic level spectrum was constructed for the fish. The δ¹³C and δ¹⁵N values of fish from the Yongshu Reef ranged from -18.74‰ to -14.33‰ and 5.96‰ to 9.37‰, with an average value of (-16.33±1.28)‰ and (8.46±0.48)‰, respectively. The δ¹³C and δ¹⁵N values of fish from the Meiji Reef ranged from -18.01‰ to -12.70‰ and 7.31‰ to 8.82‰, with an average value of (-15.02±1.53)‰ and (8.21±0.93)‰, respectively. The δ¹³C values of fish from the Yongshu Reef and Meiji Reef showed significant differences, indicating a wider food source for fish in the Meiji Reef. However, there was no significant difference in the δ¹⁵N values of fish between the two the reefs, indicating no difference in trophic structure composition between them. Cluster analysis based on the values of carbon and nitrogen stable isotope of fish divided the fishes from the two reefs into the benthic fish group and the mixed group of benthic and pelagic fishes. The trophic groups in the Meiji Reef were more vaguely defined, with evident feeding competition among carnivorous fishes. The trophic levels of fish from the Meiji Reef and the Yongshu Reef were (2.79-3.23) and (2.39-3.39), respectively. Both coral reefs were dominated by carnivorous fish at medium and low trophic levels. Most carnivorous fish were in relatively narrow ecological niches. These results suggest that the fish from the coral reefs of the Nansha Islands had a more complex trophic structure composition, wider food sources and lower community redundancy, compared with the fish from coastal tropical and subtropical bays. This study provides basic data and scientific basis for the protection and sustainable management of fishery resources in the coral reef waters of the Nansha Islands.

Based on the two-dimensional incompressible two-phase flow numerical model, the reliability of the two-phase flow surge computational model in simulating the interaction between the wave-like surge and the sea pond is verified by comparing the numerical computational results with the experimental data. Then, this paper systematically analyses the effects of wind speed, surge height, pre-tidal water depth and slope gradient on the wave-exceeding characteristics of the undulating surge on the seapond by setting up reasonable calculation conditions. Calculation results show that wind speed significantly affects the wave overtopping of the wave-like surge on the seapond, the higher the wind speed, the higher the wave overtopping of the surge, and the higher the load on the retaining wall; with the increase of surge height and pre-tidal depth, the wave overtopping of the surge and the load on the retaining wall increase; when the slope of the seapond is increased, the wave overtopping and the load on the retaining wall show the tendency to increase firstly and then decrease later. The research results of this paper have certain reference significance for the correct understanding of wave surge in the pond under the action of wind, and the change rule of the load law of wave retaining wall, which provides a scientific basis for the engineering design and safety assessment of water-related buildings in the river section of wave surge.

Typical tropical marine ecosystems are composed of unique habitats and organisms, such as coral reefs, mangroves and seagrass beds. These ecosystems are mainly distributed in tropical and subtropical marine areas worldwide. It is characterized by high material cycling efficiency, unique ecological functions, rich biodiversity and extremely high productivity, and thus a key object of marine scientific research and resource utilization. Under the multiple pressures of human activities and global changes, its degradation trend has become increasingly prominent. How to restore the function of these typical ecosystems and maintain their sustainable development for the benefit of mankind has attracted increasing amounts of attention from the academic community and the international society. In this paper, the distribution patterns, degradation trends and influencing factors of such typical marine ecosystems in the world are described, with an emphasis on the distribution patterns and biodiversity characteristics of coral reef, mangrove and seagrass bed ecosystems in China. Focusing on coral reef ecosystems, this paper discusses the causes of degradation in the ecosystems and relevant action measurements for restoration and protection in China. According to the global action plan for biodiversity conservation and the actual situation of China, countermeasures and suggestions for the restoration, reconstruction and protection of the typical marine ecosystems were proposed: 1) Establishment of a research center for typical ecosystems in the South China Sea, an intelligent monitoring system and database, and an expert think tank; 2) establishing a demonstration zone for the restoration and protection of the typical marine ecosystems, and inviting experts from multiple disciplines to work together on research-experimentation-demonstration-estimate--promotion-monitor; and 3) optimizing policies and regulations, strengthening law enforcement and management, increasing efforts in science popularization and education, raising public awareness of environmental protection, and promoting conscious social actions. This study aims to provide references for strengthening the conservation and management of typical marine ecosystems and biodiversity, maintaining their sustainable development and implementing the 30×30 goals of the Kunming-Montreal Global Biodiversity Framework.

The health of aquaculture ecosystem and the ecological effects of aquaculture activities have been paid increasing attentions in recent years. As an important part of marine aquaculture ecosystem, ciliates play a key role in matter cycling and energy flow in aquaculture water. In this paper, the research progress about ciliates in mariculture water was reviewed. The biodiversity of ciliates, ciliates diseases, the impact of aquaculture activities on ciliates, and the indication of ciliates to aquaculture environment were introduced. In addition, the limitations of past studies are considered, and the potential research hotspots are prospected for ciliates in aquaculture. This review is aimed at providing some updated information on the ecological effects of mariculture and offering available reference for further understanding the ecological role of ciliates in mariculture.

The intensification of extreme wave marine hazard induced by global ocean change is very likely to accelerate the geo-hazard risk of cliff erosion in Hainan Island. Shore platforms are expected to effectively attenuate wave energy approaching the shore and consequently reduce the erosive impact of extreme waves on cliff. Shore platforms are commonly observed in volcanic rocky coasts on NW Hainan Island, providing an ideal natural laboratory to evaluate the effect of shore platform morphology on cliff erosion. This study employs the Wucaiwan Bay rocky coastline in the E’man Town, Danzhou City, Hainan Island as the study area. Time-lapsed marine remote sensing images revealed the cliff erosion rate is about 0.26 m·a^-1 in the last decade in the area. Physical oceanography analysis suggested a maximum significant wave height of 7.8 m could be expected visiting the area in a 100-years return level. The geomorphological characteristics of the sloping shore platform and the rock strength of cliffs were further surveyed via coastal geomorphological approaches. Numerical computation outputs suggest the shore platforms is capable of reducing the wave erosional forces on cliff by over 80% under future extreme wave conditions. This study further discusses the natural coastal protection from sediment beaches, vegetations and in situ deposition of eroded boulders at rock cliff foot.

Since the Eocene, the West Philippine Sea Plate has undergone complex geological evolution, accompanied by a large amount of magmatism during the basin formation process, forming a large number of intraplate volcanic rocks. The intraplate volcanic rocks mainly occur in the ocean floor plateau, and the interrelationships between these intraplate volcanic rocks have always been a focus of research attention. Among them, the Benham Rise and the Urdaneta Plateau are good entry points for studying the interrelationships between volcanic rocks within the ocean floor plateaus in the West Philippine Basin due to their unique tectonic positions. This study conducted electron probe mineral analysis on 10 volcanic rock samples obtained from the Urdaneta Plateau, including major, trace, and isotopic analyses of the whole rock. The analysis results indicate that all the volcanic rocks in the Urdaneta Plateau we obtained are alkaline basalts, and their mantle normalized trace element patterns exhibit typical oceanic island basalt characteristics; They have high (Sm/Yb)_N values (1.89~3.92), indicating the possible presence of garnet in the source area. Based on the volcanic rock data obtained from previous studies on the seafloor of the West Philippine Basin, we found that the Sr-Nd-Hf isotope composition range of alkaline island basalts and tholeiitic island basalts in the West Philippine Basin is almost the same, but there is a significant difference in lead isotope composition, with a larger range of lead isotope ratios for alkaline island basalts. These alkaline basalts from the Urdaneta Plateau have Sr-Nd-Hf isotopic compositions similar to those of the Benham Rise tholeiitic basalts, but have significantly lower ²⁰⁶Pb/²⁰⁴Pb isotopic compositions. The formation environment of the West Philippine Basin is complex, and the formation of intraplate volcanic rocks may be influenced by basin expansion and mantle plumes. We simulated the impact of the interaction between mantle plumes and expansion centers on intraplate alkaline basalts based on isotope values. The simulation results show that ²⁰⁶Pb/²⁰⁴Pb values cannot be achieved by mixing enriched components related to mantle plumes with depleted components related to basin expansion, this indicates that the alkaline volcanic rocks in the Urdaneta Plateau have a relatively independent mantle source area, which was formed far from the spreading center and not affected by the spreading process. The formation of alkaline basalts in the Urdaneta Plateau occurred 1~2 Ma later than tholeiitic basalts, and the degree of partial melting was lower. The tholeiitic and alkaline basalts in the Urdaneta Plateau may correspond to the main and late stages of magmatic activity, respectively. Therefore, we believe that the main stages of magmatic activity in the Urdaneta Plateau and the Benham Rise may have the same mantle source region, and the two plateaus are influenced by the same mantle plume; in the late stage of magmatic activity on the Urdaneta Plateau, there is a relatively independent source area.

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.

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).

Based on the best typhoon track data provided by the China Meteorological Administration, according to K-means clustering analysis, typhoons entering the coastal waters of China from the West Pacific Warm Pool from 2002 to 2021 are divided into three types, and the three types are named as westward path typhoon, northwestward path typhoon and turning path typhoon according to typhoon path characteristics. In addition, the optimal daily product of sea surface temperature interpolation provided by remote sensing systems (REMSS) and simulation results of coupled ocean atmosphere wave sediment transport modeling system (COAWST) are used to study the changes of upper ocean temperature caused by these three typhoons with different path. The results show that the influence characteristics of three different typhoon paths on sea surface temperature (SST) are mainly reflected in the cooling amplitude and recover time: the turning typhoon exhibits the largest cooling amplitude and the longest-lasting effect on sea surface temperature, followed by the northwestward typhoon, the westward typhoon has the smallest cooling amplitude and the shortest duration of impact. The difference of three different typhoon paths on the mixed layer thickness (MLT) and thermocline thickness (TT) are mainly reflected in the rangeability of thickness and recovery time: for the rangeability of MLT and TT, the turning typhoon is the largest, followed by the northwestward typhoon, and the westward typhoon is the least. For the recovery speed of MLT and TT, the northwestward typhoon is obviously faster than the westward typhoon and the turning typhoon.

The implementation of the carbon sequestration function of carbon sinks from typical blue carbon ecosystems (BCEs), such as mangroves and seagrass beds, is one of the natural solutions to mitigate global climate change. Guangdong Province has abundant blue carbon sink resources; a scientific finding on the research progress on carbon sinks in typical BCEs is of great significance for ecosystem protecting and restoring and policy making. In this study, literatures from the Chinese National Knowledge Infrastructure (CNKI) database on carbon sinks related to BECs in Guangdong Province published in the past 20 years were analyzed by using the CiteSpace bibliometrics method from the aspects of research status and development trend, to explore the research hotspots and future research trends in this field. The visualization analysis of article authors, research institutions, keywords, etc., showed that the research development on carbon sinks in BCEs in Guangdong Province can be preliminary divided into three stages: the initial stage (2003—2011), the slow development stage (2012—2016) and the rapid development stage (2017—2023). The results of keyword co-occurrence map and cluster map analysis showed that the relevant researches were mainly focused on carbon storage, mangroves, marine carbon sinks, seagrass beds, biomass, etc, respectively, and the future research hotspots would still be oriented to carbon neutrality and carbon peaking. The study proposed that in the future, researches should be emphasized on the monitoring and accounting methods and the sink-enhancing technologies for carbon sinks in typical BCEs including mangrove forests and seagrass beds in Guangdong Province, and on the construction of a carbon-negative technology system for typical BCEs as well, which will contribute to realizing the synergy between the protection and restoration of BCEs and the enhancement of carbon sequestration and carbon sinks, and will finally achieve carbon neutrality and carbon peak.

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.

Marine heatwaves are extreme high temperature events that occur on the oceans and have devastating impact of marine environment and ecosystems. Using the fifth generation of European centre for medium-range weather forecasts atmospheric reanalysis data (ERA5) and the Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) dataset during the period of 1960-2020, and data from the North Atlantic idealized experiments performed with the CESM1 model, this study investigated the variation of the interannual relationship between the El Niño-Southern Oscillation (ENSO) and the following early summer marine heatwaves in the western Pacific, and the possible reasons for their decadal variation based on correlation, synthetic analysis and other statistical methods. The results are shown as follows. 1) The interdecadal relationship between the ENSO and the following early summer marine heatwaves months in the western Pacific displays a prominent decadal variation, which is modulated by the Atlantic Multidecadal Oscillation (AMO). A high correlation between the ENSO and the following early summer marine heatwaves in the western Pacific appears during the positive AMO phase, while no significant correlation is found during the negative AMO phase. 2) AMO mainly affects the response of atmospheric circulation in the Northwest Pacific by modulating ENSO amplitude, thereby affecting the relationship between the ENSO and the following early summer marine heatwaves in the western Pacific. During the negative (positive) AMO phases, the Northwest Pacific anomalous anticyclone/cyclone appears strong (weak), and its position shifts toward east (west) in the following early summer, due to the relatively strong (weak) ENSO events through strong (weak) wind-evaporation-SST positive feedback mechanism. Thus, the position and intensity of anomalous anticyclones/cyclones led to significant differences in the distribution of early summer marine heatwaves in the western Pacific between the positive and negative AMO phase.

To elucidate the species composition of fishes in the Langhua Reef of Xisha Islands, reveal their evolutionary traits, and ensure the protection and sustainable use of coral reef fishes in this region, a comprehensive survey was conducted in 2023. Employing techniques such as dive-fishing, hand-fishing, underwater videography, and environmental DNA (eDNA) analysis, this study integrated historical data from 1979, 1998—1999, and 2003 to analyze the species composition and temporal fluctuations in the fish population of the Langhua Reef. To date, a total of 259 fish species have been identified in the reef, classified into 12 orders, 47 families, and 115 genera. Among these, the most populous are the perch-like species, accounting for 200 varieties. The results indicate an exponential relationship between the number of fish species in the reef and their corresponding maximum overall length, with a significant decline in species count as the maximum length increases. Predominantly, the reef is inhabited by small-sized and carnivorous fish, constituting 49.03% and 59.07% of the total species, respectively. The 2023 survey highlighted that 77 fish species, previously recorded in historical data, have not been observed in recent years, predominantly among carnivorous types. Notably, almost all large fish in the reef are carnivorous. Seven species, listed on the IUCN Red List and categorized as large fish, were absent from the current study, with the exception of the brown-spotted grouper (Epinephelus fuscoguttatus).The species composition, dietary patterns, and historical similarity indices of the Langhua Reef fish varied significantly, especially among large and carnivorous species, which demonstrated the lowest similarity indices. Furthermore, the study revealed a downward trend in both the mean taxonomic distinctness index (Δ⁺) and the variance in taxonomic distinctness index (Λ⁺), falling significantly below the 95% confidence intervals. These findings suggest that environmental disturbances, climate change, and human activities have led to a notable turnover in the fish composition of the reef, with large carnivorous species being the most severely affected. This research provides a theoretical reference for a deeper understanding, effective management, and conservation of the Langhua Reef coral reef ecosystem. It also offers foundational data and scientific insights crucial for the restoration of the coral reef ecosystem.

Black carbon is one of the carbonaceous materials, it exists ubiquitously in the environment and could be resistant to oxidation and decomposition. Black carbon might strongly affect the global carbon cycle as an important component of recalcitrant organic carbon. The current discrepancy of marine black carbon budgets indicates that there are unknown sources or buried pathways of black carbon in the ocean. It has been confirmed that marine extreme environments, such as abyssal trenches, hydrothermal vents and cold seeps, may be important sources or sinks of marine black carbon with the continuous deepening of the research on black carbon in these environments. In this review, the geochemical characteristics of black carbon in extreme marine environment are summarized. It is found that the unique “V”-shaped terrain of the abyssal trenches is conducive to the accumulation of materials, in which the black carbon is older than the syn-sedimentary organic carbon, and the annual buried amount of black carbon is about (1.0±0.5) Tg. The high-temperature fluid in hydrothermal vents forms in-situ authigenic black carbon by “burning” organic matter, and its annual contribution to the ocean is about 1.6~9.7Tg, which is an important source of marine black carbon. The source and sink process of black carbon in cold seeps remain unclear, but the high abundance of anaerobic methanotrophic archaea in these areas has recently been proved to directly produce black carbon, and its carbon isotope value is negatively below -60‰. As the only microbial source of black carbon found so far, it is an important supplement to the traditional understanding of black carbon types. The overall framework of marine black carbon source and sink process has been established notwithstanding, there is a lack of direct morphological observation and characterization of black carbon in marine extreme environments. It is necessary to clarify the ratio between terrestrial black carbon input and marine authigenic black carbon in extreme marine environments, to further understand the source and sink process of marine black carbon and explore the role of extreme environmental black carbon in marine black carbon budgets in the future.

There are rich fishery resources and complicated hydrologic environment in the coastal waters of eastern Guangdong. In order to systematically improve the level of oceanic observation and the knowledge of ecological dynamic processes in the coastal waters of eastern Guangdong under the changing climate, a comprehensive investigation of ecological and environmental factors such as hydrodynamics, biology and chemistry during four seasons was carried out in May (spring), July (summer), October (autumn) 2022 and January 2023 (winter). Based on the taxonomic identification of zooplankton, the characteristics of community structure of zooplankton in the surveyed area were analyzed, and the effects of environmental factors on their spatial and temporal distribution were discussed. According to the environmental parameters, the survey area can be divided into the near-shore (mainly affected by human activities) and off-shore (mainly affected by ocean currents) areas, and the zooplankton were characterized by the seasonal and regional pattern. Seasonally, the species, biomass and abundance of zooplankton in spring and summer were higher than those in autumn and winter. Regionally, the species, biomass and abundance of zooplankton in the off-shore waters are generally higher than those in the near-shore waters. Moreover, there are differences in the contribution groups and dominant species to the total zooplankton abundance in different seasons in the off-shore waters. Although copepods and chaetognaths were the main groups of zooplankton, the abundance of planktonic larvae and fish eggs in spring was higher than in other seasons, and the peak value is concentrated in the southwestern Hanjiang Estuary, indicating that this surveyed area was still an important spawning ground in the coastal waters of eastern Guangdong. The increase in copepods species and abundance in summer is related to the high chlorophyll a concentration improved by coastal upwelling in eastern Guangdong. Warm-temperate species carried by Fujian and Zhejiang coastal currents in winter are the main contributors to zooplankton abundance. Although chlorophyll a concentrations are higher in the near-shore waters, zooplankton species, biomass and abundance are lower. Under the effect of anthropogenic activities and climate change, long-term systematic monitoring and analysis of the response of zooplankton to the dynamics of the marine environment are needed in the coastal waters of eastern Guangdong.

Sandy coast is one type of coastal wetland ecosystems, which has important ecological service functions and is also susceptible to human activities and global changes. In September and December 2022, ten survey profiles were set up on the sandy coast in the Shenhu Bay, Fujian Province to conduct observations of the terrain and geomorphic characteristics as well as measurements of sediment granularity. A comprehensive evaluation of the natural resource endowment and disaster bearing capacity of the sandy coast in the Shenhu Bay was conducted based on the related national standards which provide corresponding indexes and grading criteria. The width of intertidal zone of Shenhu Bay beach is 150-800 m in autumn and 150-950 m in winter. The overall trend is narrow in the middle and wide on both sides. The slope of intertidal zone is generally slow. Elevation, dry beach width and intertidal zone width increase in winter, compared with those of autumn. For two of the sediment grain size characteristics survey sections, the composition of the beach shoulder area is sand, the composition of the sediments in the high tide area is sand and gravel, and the main components in the middle tide and low tide areas are sand and silt, but the components vary across the seasons. The overall natural resource endowment of the sandy coast in the Shenhu Bay is good, but due to factors such as seaward width and relative tidal range, the natural disaster bearing capacity is moderate. As the first-hand basic data of Shenhu Bay, the research results provide technological support for improving its natural resource endowment, natural disaster bearing capacity, and protection and restoration of the sandy coast.

To investigate the chemical composition and biological activity of the soft coral Lobophytum sp. collected from South China Sea. A series of methods such as silica gel column chromatography, thin-layer chromatography, Sephadex LH-20 column chromatography, and semi-preparative high performance liquid chromatography were used to separate and purify. The structure of the compounds was characterized by analysis of NMR data and comparison with the data reported in literature. Twelve compounds were identified from the soft coral Lobophytum sp., including nine diterpenoids: (+)-(7R, 8R)-epoxy-7, 8-dihydrocembrene C(1), (1R, 2E, 4R, 7E, 11E)-cembra-2, 7, 11- triene-4-ol(2), (-)-(2R, 7R, 8R)-sarcophytoxide(3), entsarcophine(4), sarcotenusene C(5), (7S, 8S)-epoxy-1, 3, 11-cembratrien-16-oic methyl ester(6), sarcophytonin B(7), sarcoconvolutum D(8), laevigatol A(9); three steroids: campesterol(10), (24S)-24-methylcholesterol(11), gorgonol(12). Compound 8 was isolated from the soft coral Lobophytum sp. for the first time. The bioassay results revealed that compounds 3, 4, 5, 7 and 10 show significant antibacterial activity against fish pathogens Photobacterium damselae FP2244, oxytetracycline-resistant Streptococcus parauberis SPOF3K, and human pathogen vancomycin-resistant Enterococcus faecium.

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.

Data sharing is an important task during the implementation of compilation project for the historical data reorganization of scientific investigation in the South China Sea and its affiliated islands and reefs. This study mainly introduces the design and construction of comprehensive database for scientific investigation in the South China Sea and the “Digital South China Sea” platform. First, the design and development focus of the “Digital South China Sea” will be elaborated to achieve the intensification of data management, sharing processes and efficient resource utilization. Then, the interactive analysis application of data and dynamic visualization application are introduced using the “Voyage Map” and “Island Reef Map” modules. The construction of the “Digital South China Sea” platform follows the project objectives, with unified planning and deployment, unified standard system, unified data platform, and unified achievement release. Data services run through the entire lifecycle of project implementation, promoting the formation of a new pattern of data work development that involves joint consultation, construction, sharing, and win-win results.

Marine environmental data is an important strategic resource for mankind to understand, protect and exploit the ocean. With the rapid development of digital economy and science and technology, marine environmental data has become a new and important factor of production. As a new form of asset, how to value marine environmental data assets has become a new problem. Through the in-depth investigation and research of the value assessment of domestic marine data assets, it is concluded that the traditional cost method and the benefit method and their combination are the basis for the current valuation of marine environmental data, and it is found that the method of value assessment of marine environmental data in the new era has complexity, flexibility and multi-dimensional evaluation methods, which have very important economic value for the development of marine economy and the sustainability of marine scientific research.

The environmental and ecological effects of oyster culture are controversial, and the mechanism of its impact on macrobenthic fauna remains unclear. In this study, two comprehensive investigations referring to macrobenthic communities and environmental variables were conducted in November 2020 (autumn) and January 2021 (winter) in a raft-string oyster culture zone and its adjacent waters in the Dapeng Cove. A total of 103 species were obtained, with polychaetes, bivalves, and crustaceans dominating the species composition. Significant seasonal variations were observed, emphasizing the influence of seasonality on macrobenthic communities. Distinct regional differences were also noted between the culture zone and control zone, highlighting the impact of oyster culture on community composition. The community parameters, including species number, density, and biomass, exhibited higher values during winter and in the control zone compared to autumn and the culture zone. The results of biological traits analysis (BTA) indicated that the trait composition of macrobenthic communities differed significantly only between seasons. There was no significant difference in the trait composition of macrobenthic communities between the culture zone and control zone. Nevertheless, regional disparities in bioturbation mode, body size, and feeding type were evident. Functional richness (F_ric) displayed lower values in the culture zone compared to the control zone, whereas functional evenness (F_eve) and functional divergence (F_div) indices remained relatively consistent across regions. This study identified several critical environmental variables shaping macrobenthic community composition, including chlorophyll a, suspended matter, nutrients, sediment organic carbon, sulfide levels, and sediment particle size. Notably, the feeding type, living habit, and larval development patterns of macrobenthic fauna closely correlated with environmental variables. Furthermore, both the species richness (d) and the functional richness (F_ric) indices emerged as valuable environmental indicators.

The secondary metabolites and antibacterial activities of the Weizhou Island coral Acropora austera associated fungus Arachniotus ruber GXIMD 02510 were investigated. Various modern chromatographic techniques were used to isolate and purify the fermentation products of this strain. Their structures were determined by comprehensive spectroscopic methods, including nuclear magnetic resonance and by comparison with literature data. The antibacterial activity was determined. A total of 13 compounds were obtained and characterized, which were auxarthrols B, E, F, and H (1—4), paradictyoarthrin A (5), chrysoqueen (6), ocauxarthrol A (7), 1, 3, 6-trihydroxy-8-methylxanthone (8), N-acetyltyramine (9), methyl 2-(4-hydroxyphenyl)acetate (10), m-hydroxylphenylacitic acid (11), L-tenuazonic acid (12), and 2, 3, 22, 23-tertrahydroxy-2, 6, 10, 15, 19, 23-hexamethyl-tetracosa-6, 10, 14, 18-tetraene (13). Antibacterial activity test showed that compounds 1, 4—6, and 11 showed inhibitory activity against Pseudomonas aeruginosa, and the minimum inhibitory concentration (MIC) values were ranging from 0.078 mg·mL^-1 to 0.312 mg·mL^-1. This study will expand the chemical diversity of the genus Arachniotus and also provide chemical entities for the development of antibiotics.

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.

Phaeocystis globosa is an important and cosmopolitan harmful alga in coastal area. This study conducted a comparative analysis on the cell morphological characteristics and transcriptome of P. globosa isolated from the Beibu Gulf of Guangxi Province. The results indicate that P. globosa contains two types of cells: motile flagellated cells and non-motile cells without flagella. The cell size is 2-5 μm and the non-motile cells are capable of forming colonies, with diameters ranging from few micrometers to several hundred micrometers. Transcriptome analysis reveals that colonial cells exhibit more genes with upregulated expression than solitary cells and most of the differentially expressed genes are associated with transport, decomposition metabolism, amino acids, lipids, carbohydrates, and other metabolic pathways. Particularly, the gene encoding UDP-glucose-4-epimerase, which is involved in polysaccharide biosynthesis, shows significantly upregulated expression, indicating extensive synthesis of glycosaminoglycans during the formation of colony. These results provide basic information for further understanding the morphological transformation mechanism of P. globosa in different geographical strains.

Using the first level brightness temperature data of the microwave radiation imager (MWRI) carried on the FY-3D (Fengyun-3D) satellite, combined with the second level (L2) precipitation orbit product, and based on the polarization corrected temperature and scattering index (PCT-SI) comprehensive method, two precipitation rate inversion models for the ascending and descending orbit ocean surfaces were established, the two models established in this study were also validated by multiple typhoon cases. The results show that there is little difference in the effectiveness of inversion of precipitation between the ascending orbit data and the descending orbit data, and the precipitation distribution area retrieved is slightly larger than that of the L2 product precipitation area; both models tend to overestimate the low value of precipitation and underestimate the high value of precipitation; the correlation coefficient, mean absolute error, and root mean square error of the ascending orbit inversion model are 0.72632, 2.3055 mm·h^-1 and 2.7254 mm·h^-1, respectively. The correlation coefficient, average absolute error, and root mean square error of the descending orbit inversion model are 0.73363, 1.9079 mm·h^-1 and 2.3651 mm·h^-1, respectively. This study has successfully inverted the distribution area of ocean surface precipitation and near surface precipitation rate, providing a reference for estimating the distribution of ocean surface typhoon precipitation and precipitation rate inversion using satellite borne microwave imaging data.

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.

The global carbon and nitrogen cycles depend heavily on deep-sea microorganisms, and the majority of current, refined research on these organisms is based on high-pressure simulation culture and detection in laboratories. However, when deep-sea samples are brought in for culture and detection, the environmental parameters, such as temperature, pressure, etc, change at various degrees, which has an impact on the results of subsequent experiments and detection. For this reason, a device (ocean automatic series incubation system, OASIS) was developed for in situ automatic series incubation of deep-sea microorganisms. This research emphasizes the accuracy of deep-sea liquid transfer and focuses on the OASIS operating concept, system design, and experimental validation. The device can function normally under 30 MPa high pressure, and it can automatically finish the culture of microorganisms and the fixation of life information in accordance with the chronological order. These test results demonstrate that OASIS has passed the pressure, sea, pool, and other tests. They also accurately provide an understanding of the ecological benefits of deep-sea ecosystems. It offers strong equipment assistance for precisely identifying the ecological advantages of deep-sea environments.

Bioclastic sediments are an important part of marine sediments, and the motion characteristics are the key to study their depositional process. From the characteristics of bioclastic sediments, we summarize the two main characteristics of shape and internal pore space that affect sediment motion. From the experimental studies of settlement, inception and bank evolution, the influence of bioclastic sand properties on sediment motion characteristics was analyzed. Existing studies have only explored the effect of shape on the motion of single-particle bioclastic sediments and lacked the exploration of the motion of clusters of particles. Due to the limitation of the research tools, the influence of internal pore properties on the motion of bioclastic sediments was not discussed. In the future, we should take into account the shape of bioclastic sediments and internal porosity characteristics in the context of oceanic hydrodynamic conditions to characterize the motion of bioclastic sediments, to quantify the influence of the characteristics of bioclastic sediments, and to apply the results to the practical application in order to predict the evolution of the geomorphology of the shore and beach in the environment of bioclastic sedimentation.

Based on ocean reanalysis system version 5 (ORAS5) and ECMWF reanalysis v5 (ERA5) data, the strength of oceanic stratification and its influencing factors in the Indonesian-Australian basin and its surrounding waters are revealed by using the buoyancy frequency of mixed layer bottom to characterize the oceanic stratification intensity. The results show that the oceanic stratification in this basin is stronger in the north and weaker in the south spatially, while stronger in the boreal spring and weaker in autumn temporally. The analysis of the factors influencing the changes of mixed layer temperature and mixed layer salinity in the basin highlights the significant contributions of surface flux and ocean advection. Particularly, zonal advection associated with the Indonesian Throughflow plays a crucial role in pycnocline stratification by affecting the density structure of the subsurface. Further analysis of the influence of the Indonesian Throughflow on the oceanic stratification in the basin indicates close relationships between the throughflow and thermohaline anomalies above and below the mixed layer interface of the basin; the salinity anomalies affect the seasonal variations in the oceanic stratification by influencing the vertical density gradient.

The outbreak of the crown-of-thorns starfish (COTS, Acanthaster solaris) population has severely damaged coral reef ecosystems, leading to a significant impact on biodiversity. The knowledge of the reproductive characteristics of the COTS is crucial for predicting population outbreaks and scientific management strategies. In this study, the samples were collected from ten reefs in the Xisha Islands from May to July 2022, and a total of 928 individuals were conducted for the reproductive biology analysis. The results revealed that the body diameter (diameter, D) of the Xisha Islands ranges from 82 to 363 mm, the mean value was (217±45) mm, the body weight (weight, W) range was 16.89~1 003.98g, and the mean value was (224.69±123.6) g. The relationship between body diameter and weight followed a power function, expressed as W=3.357×10^-4D^2.48 (R²=0.86), indicating allometric growth in the population. The sex ratio of male to female individuals was 1.22:1. The initial sexual maturity body diameter for female COTS was 206.38mm. Gonadal maturity was classified into four stages, with the highest gonadosomatic index (GSI) and egg diameter occurring in Stage Ⅱ, averaging (15.68±6.35)%and (1.27±0.32) mm, respectively. The absolute fecundity range was 174 720~11 317 560 eggs, with mean of (3 555 081±2 301 657) eggs, relative fecundity range was 2 176.65~23 851.30 eggs·g^-1, and the mean value was (10 581.89±4 213.73) eggs·g^-1. The relationship between absolute fecundity and body diameter exhibited a power function (F_a=0.028 8D^3.346, R²=0.67, P<0.01), and the relationship between relative fecundity and body weight exhibited a power function (F_a=2 588.38W^1.234, R²=0.73, P<0.01). Reproductive capacity in COTS was closely related to individual size. This study, for the first time, reveals the reproductive characteristics of COTS in the Xisha Islands during the summer, providing a scientific basis for understanding the population dynamics and outbreak mechanisms of COTS. The results are significant for formulating effective conservation measures for coral reef ecosystems.

In this study, based on the field survey data of the Guangxi Shankou National Mangrove Ecological and Natural Reserve (hereinafter referred to as the Shankou Mangrove Reserve) in 2022, six time-phase remote sensing images during 1987—2021 were selected, and an object-oriented image classification method was used to analyze the status of the land-use and land-cover change (LUCC) and to calculate the landscape pattern index (LPI) based on the LUCC. This study combined LPI with LUCC to focus on exploring the wetland change process and its important influencing factors in the Guangxi Shankou Mangrove Reserve. There has been a continuous transition between land types over the past 35 years, including cultivated land continued to decrease, and Spartina alterniflora and aquaculture ponds increased, with Spartina alterniflora mainly encroaching on the former coastal mudflats, and aquaculture ponds mainly converted from forested land and cultivated land. In terms of landscape, landscape fragmentation increased, connectivity decreased, landscape shape became more complex, and landform succession became more frequent; Based on Pearson's correlation analysis, there were highly significant or significant correlations between land use change and landscape indices for coastal mudflats, mizuna mudflats, and aquaculture ponds. Significant land use changes have occurred in the Shankou Mangrove Reserve over the past 35 years, with invasive species (Spartina alterniflora) and anthropogenic disturbances (aquaculture ponds) being the main factors influencing changes in mangrove wetlands in the area, and the main contributors to the continued increase in landscape fragmentation. This study reveals the influencing factors of regional landscape changes, which can provide a theoretical basis for the environmental management and protection of typical mangrove ecosystems.

Dissimilatory nitrate reduction processes, including denitrification, anaerobic ammonium oxidation, and dissimilatory nitrate reduction to ammonium (DNRA) regulate the removal and retention of nitrogen elements in the ocean. Global warming affecting the nitrogen cycling processes in sediments, but it is not yet clear the differences in response of dissimilatory nitrate reduction processes in carbonate sand and silicate sand sediments to increased temperature. Therefore, we used ¹⁵N isotope tracing technology and temperature-controlled incubation of sediments to investigate the response of dissimilatory nitrate reduction processes in different sediment types in the coral reef area of the Weizhou Island to increased temperature. The results indicate that DNRA and denitrification processes exhibited significant differences in response to increased temperature in two different types of sediments. The rates of denitrification and DNRA in silicate sand were significantly increased with the increased temperature, but those in carbonate sand exhibited opposite trend, which may be related to differences in microbial community in different sediments. Due to anaerobic ammonium oxidation process being more sensitive to increased temperature, the contribution of denitrification to nitrogen removal increased, but its byproduct N₂O may have a negative impact on climate. In addition, the increase in temperature led to an increase in the contribution of DNRA to nitrate dissimilation reduction, which will exacerbate the negative impact of nitrogen excess on the coral reef ecosystem of the Weizhou Island.

The monitoring of water quality is very important to understand the changes in marine ecosystem. Based on the continuous monitoring data of two buoys in the southwest of the Daya Bay from 2022 to 2023, this paper analyzes the time series changes in water quality environment. The results showed that the temperature and salinity in the southwest of the Daya Bay were affected by solar radiation and precipitation, with obvious seasonal differences. The temperature and salinity were high in summer and low in winter; chlorophyll a, dissolved oxygen and pH showed obvious diurnal changes. In summer and autumn, the Dapeng Cove was characterized by high temperature, low salinity, low dissolved oxygen, low pH, and high chlorophyll a compared with the Yangmeikeng. Pearson correlation analysis showed that there was a significant correlation among temperature, salinity, dissolved oxygen, pH, and chlorophyll a in summer and autumn, and there were regional differences. Near the bay mouth, waves, upwelling, and other water movements may be the main influencing factors; nearshore, the increase of runoff input may be the primary dominant factor causing changes of water quality. In addition, this article also recorded the impact of distant typhoons causing waves and precipitation events, thus affecting the environment of the Daya Bay. Analyzing the characteristics of the changes in the time series of coastal environmental parameters has important implications for studying the evolutionary characteristics of marine ecosystems.

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.

Mangroves are an integral part of ecological civilization and hold significant importance in achieving carbon neutrality goals. In recent years, numerous conservation and restoration efforts have been undertaken to protect mangrove ecosystems. However, there is currently a lack of predictive methods for comparing and selecting effective conservation measures to guide mangrove ecological reconstruction. Therefore, a novel research approach combining “numerical simulation models” with “classification models” is proposed. In the application of this approach, the hydrodynamic and sedimentary environment of the Zhelin Bay in Guangdong Province was simulated for one year. By considering factors such as flooding time, relative peak bed shear stress, and bed level change, the stressors faced during the process of mangrove colonization were described. And ecological reconstruction effects of mangroves distributed on the inner tidal flats of the Ligang tidal inlet were predicted under four different conditions. The results indicate that restoring the inlet depth slightly alters the regional hydrodynamics and sediment environment, leading to a decrease of 3.12% in the success rate of ecological reconstruction. Elevating the bed elevation significantly reduces flow velocity and intensifies outer-side scouring. Raising the elevation by 0.5 meters and 1.0 meter increases the success rate of ecological reconstruction by 16.43% and 32.75%, respectively.

The prediction of significant wave height (SWH) plays an important role in marine transportation and maritime activities. Based on the near-shore real measurement data of the Hailing Island, Yangjiang, China, a network model integrating the maximum information coefficient algorithm (MIC), residual network (ResNet) and long and short-term memory network (LSTM) is proposed. Firstly, the MIC algorithm was used to screen out the parameters with high correlation with the target predictors from the dataset as the input of the model. Then the residual network was introduced into the LSTM to construct the Res-LSTM prediction model. Finally, the r-squared (R²), root mean square error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) were selected to evaluate the prediction results. Meanwhile, the prediction results of extreme gradient boosting (XGBoost) network, support vector regression (SVR) network and LSTM network were compared. The results demonstrate that the MIC-Res-LSTM model can improve the accuracy of the short-time significant wave height prediction values.

To investigate the behavior and related factors of hermit crabs in selecting shells for settlement, this study collected 81 empty gastropod shells and 72 hermit crab samples from the intertidal zone of the Xisha Islands. Results obtained through morphometric measurements and statistical methods on two species of hermit crabs and the shells of Turbo argyrostomus show that in the environments where the types and abundance of shells are relatively rich, both Dardanus deformi and Calcinus laevimanus preferentially choose shells from the family Turbinidae for settlement. Specifically, the shells of T. argyrostomus are more likely to become settlement sites for both hermit crab species. Statistical analysis of morphological parameters reveals significant differences between the two species in shell weight, shell length, shell width, shell height, aperture length, and aperture width during shell selection. Standardized data indicate differences in shell size preferences between the two hermit crab species. D. deformi primarily considers the ratio of cephalothoracic length to shell length, while C. laevimanus focuses on the ratios of cheliped width to shell width, shell height, and aperture length. In summary, this study provides an in-depth exploration of the complex process of hermit crab shell selection, revealing differences in shell preferences among different hermit crab species. The findings contribute valuable insights into the ecological behavior of hermit crabs, aiding in understanding their roles and adaptive mechanisms in intertidal ecosystems.

Tsunami is a serious marine disaster, and accurate tsunami prediction is of great significance to marine engineering and the safety of people’s lives and property. In this paper, based on 1-dimensional convolutional neural network (CONV1D), the evolution model of tsunami-like hydrodynamic characteristics of reef topography is constructed. By inputting observed values of wave heights resembling tsunami waves, the water inundation time series curves for specified locations on islands and reefs are generated. This achieves a prediction from one time series to another, serving the purpose of marine disaster prevention. The results indicate that the average relative error in predicting the arrival time of tsunami-like waves is 0.71%, and the average relative error in predicting maximum water levels is 6.99%. The hydrodynamic characteristics of island and reef terrains resembling tsunami waves obtained through CONV1D exhibit a strong alignment with numerical results.

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.