To address the discrepancies in ocean current observation data processing methods, the study systematically elaborated the methods and compared the differences between four methods for calculating mean velocity and direction: arithmetic mean, unit vector mean, vector mean, and instantaneous value matching based on observation data continuously collected over 26 hours from 6 monitoring stations in the eastern waters of Weizhou island. Results confirmed that arithmetic mean velocities consistently exceeded vector mean values, the average relative deviation between the two methods for calculating flow velocity reached 9.55% in the surface layer, but was less than 1% in the middle and bottom layers. Directional discrepancies between unit vector and vector mean methods reached 2.7 ° in the surface layer, but was less than 0.5 ° in the middle and bottom layers. The deviation of the flow velocity and flow direction results had obvious vertical stratification characteristics. The surface layer seawater had high dispersion and significant calculation deviation due to wind and wave disturbance, while the middle and bottom layers had small deviations due to stable flow direction. Mid-bottom velocity deviations >5％ or directional differences >5 ° were proposed as robust quality control thresholds.

In this paper, the spatial-temporal characteristics of wind and waves along the northern coast of Zhejiang province during the impact of landing typhoon “In-Fa” and steering typhoon “Chanthu” were analyzed based on the third-generation SWAN model (Simulating wave nearshore, SWAN). The results showed that the wind and wave characteristics of the Zhoushan Islands during the impact of the landing typhoon “In-Fa” and steering typhoon “Chanthu” were compared. The results showed that there was a significant blocking effect of Zhoushan Islands on typhoon waves of different paths, which inhibits the growth of wind waves. The wind-wave characteristics of the two types of typhoons differed in different regions: the wind duration was longer during the landing typhoon “In-Fa”, and the significant wave height caused in Hangzhou Bay was about 39% higher than that of the steering typhoon “Chanthu”. The leading time of wind waves in the open sea region was about 1.7 times longer than that of landing typhoon “In-Fa”. The wave level and the maximum wave period of different regions during landing typhoon “In-Fa” showed a positive correlation. The wave types caused by the two kinds of typhoons differed in different regions: wind waves dominated in Hangzhou Bay; wind waves and mixed waves dominated in open sea area, but the effect of swell was more significant than that in the bay.

Accurate and real-time water level forecasting is of great significance for coastal economic activities. Residual water level is an important component of water level in nearshore waters. In this study, a multi-factor intelligent forecasting model was constructed for short-term prediction of residual water level at 10 tide gauge stations in the Bohai Sea using long and short-term memory networks, and a maximum of 12 hours of residual water level forecasting experiments were conducted with the test sets. The results showed that the multi-factor forecasting model with meteorological factors could capture the connection between sensitive information such as wind speed, wind direction and sea level pressure and the residual water level, which could further improve the accuracy of the residual water level forecast compared with the single-factor autoregressive forecasting model and traditional linear regression model. The average root-mean-square error and correlation coefficient of the maximum 12-hour residual water level prediction were 0.138 3 m and 0.616 4, respectively, and the average correlation coefficient of the integrated water level prediction was 0.952 3. The multi-factor forecasting model could be used to characterize extreme water increases during storm surges.

In order to improve the utilization efficiency of wave energy in the integrated structure of floating breakwater and wave energy device, Flow-3D software was applied to establish a three-dimensional numerical wave flume. The change of transmission coefficient, reflection coefficient and heave response amplitude operator of three kinds of heterogeneous layout floating breakwaters with different opening shapes in different periods under different draft was studied. Incident wave height and opening length were analyzed. The wave attenuation and focusing performance of three heterogeneous layout floating breakwaters were compared. The results showed that the V-type floating breakwater outperformed both the parabolic and concave types in terms of wave attenuation and focusing performance. At the same time, the depth of the structural draft was a critical factor that significantly impacted the performance of the breakwater. Reducing the opening length within a reasonable range could also enhance the wave attenuation and focusing performance.

A novel method using solidified soil for scour repair and protection around offshore foundation had been proposed recently. However, the engineering application of this method was very limited till now and still there was a lack of comprehensive study on the effect of scour protection of the solidified soil. A numerical study using FLOW-3D was conducted to simulate the local scour of the sandy seabed around the monopile under the sea current. The accuracy of the numerical model was verified by comparing the numerical and experimental results. The scour protection effect and mechanism behind were investigated in details. The results showed that for the sandy seabed in this study, scour protection layer of solidified soil could take effect and reduces the maximum scour depth around the monopile by 61%. If the scour repair was conducted in the early stage of rapid scour development around the monopile, new scour might occur again and the optimal scour protection effect could not be achieved. The scour depth around the protection layer decreased with the coverage and depth of the protection layer. The optimal coverage of protection layer was 2.6 times of the pile diameter,for which the best scour protection was achieved with a maximum scour depth of 0.011 7 m.

The soft soil around Jiaozhou Bay is the Holocene marine soft soil with short deposition time and small thickness. It is mainly mucky silty clay with medium and low liquid limit. The macro structure is layered or thin layered. It has certain structure, high water content, high degree of saturation, large void ratio, high compressibility, low shear strength and bearing capacity. Based on the systematic samples of marine soft soil around Jiaozhou Bay, the distribution, composition and structure of marine soft soil were analyzed through mathematical statistics. The probability distribution characteristics of physical and mechanical properties of marine soft soil and the correlation between their indices were analyzed. There was a significant or highly correlated linear relationship between the physical indices. The linear correlation between compression indices and physical indices was strong, and no obvious correlation was found between shear strength indices and physical indices.

As wave height is an important parameter of ocean characteristics, predicting wave height accurately is of great significance to human activities such as construction of marine projects and coastal hazard assessment. Most of the current studies mainly focus on single-step prediction of wave height, however, the single-step prediction model has limitations in long time series feature extraction. Therefore, this paper proposed a recursive multi-step wave height prediction model called DC-LSTM, by predicting the trend of the wave height sequence at future moments. The model used dynamic time warping (DTW) to measure the similarity between time series to find the historical wave height sequence that was most similar to the sequence and whose last moment trend was the same as the predicted trend, and finally fusing it with the wave height prediction results of LSTM, in order to reduce the cumulative error. Experiments were conducted on four stations from the Gulf of Alaska, North America Basin and Gulf of Mexico waters. Comparing with models such as LSTM and TCN, the results showed that the DC-LSTM model had the best prediction results, and the model provided an effective complement to the traditional wave prediction methods.

A new type of grouting material, FCM (Fast Cementing Material), was being used for the rehabilitation and strengthening of coastal and offshore infrastructure, such as the rehabilitation and strengthening of old harbours and the grouting of underwater tunnels. In order to test the fast setting performance of the FCM, fluidity tests of the FCM and strength tests of the rock mass were carried out to investigate the influence of the water-solid ratio on the fluidity and setting time of the new grouting material. The changes in compressive strength, damage pattern and surface microscopy of the grouted solids were investigated by means of erosion tests of the grout-reinforced specimens in acidic environments and freeze-thaw cycles. The results showed that the optimum water-solid ratio of FCM was 0.3 and the compressive strength of the grout-reinforced specimens with sandstone could match or exceed the original rock strength. The acidic environment and freeze-thaw cycles eroded the grout-reinforced specimens, and the acid-freeze-thaw coupling had a more significant degradation effect on the grouted material, with the fracture dip and number of freeze-thaw cycles significantly affecting the compressive strength of the specimens.

In order to explore the anesthetic effect of eugenol on juvenile Oplegnathus fasciatus, the effects of eugenol at different anesthetic concentrations on this fish species were studied, and described using anesthesia time, recovery time, survival rate and air exposure time, aiming to provide a reference for marker release, live transportation, production and breeding of O. fasciatus. When the concentration of eugenol was less than 20 mg/L, the ideal anesthetic effect cannot be achieved. When the concentration of eugenol was more than 30 mg/L, the anesthetic time decreased with the increase of concentration. With the prolongation of recovery time, all of them can be completely resuscitated within this range. The time required to enter deep anesthesia and recovery varied between 75.67 and 149 s and between 399.67 and 495 s, respectively, and the survival rate reached 100%. Among them, death occurred at 90 mg/L, and the suitable anesthetic concentration ranged from 30 to 80 mg/L. Within the range of effective anesthesia concentrations, the survival rate reached more than 93% within 10 min of anesthesia. With the increase of time, the higher the anesthesia concentration, the lower the survival rate of fish. The survival rate decreased to less than 50% at 20 min and 30% at 30 min, and the survival rate decreased significantly. Under the condition of 30 mg/L, the juvenile of O. fasciatus can be fully recovered within 12 min after entering ANES 5, and the recovery time reached 765.33 s at 12 min, not in line with the ideal recovery time. The suitable operation time should be less than 10 min. Studies have shown that in practical applications, attention should be paid to the time of soaking and air exposure. If the operation time is too long, the concentration of eugenol should be appropriately reduced to ensure the survival rate of fry.

The preservation of small yellow croaker (Larimichthys polyactis) is of the vital importance to the national marine protection areas (MPAs) of Lvsi fishing ground. In this study, we utilized the fishery data collected from the bottom trawl surveys in the MPAs and their surrounding waters during a period from spring to autumn, 2019 to 2022. The environmental data such as bottom temperature, bottom salinity and depth were simulated with the Marine Environmental Committee′s (MEC) ecosystem model. The arithmetic mean model (AMM) and geometric mean model (GMM) were used to develop the habitat suitability index (HSI) model for the MPAs and their surrounding waters from spring to autumn seasons, respectively. The regions characterized by the greatest suitable habitat of L. polyactis within the MPAs and the surrounding waters exhibited discernible seasonal fluctuations. The regions with the highest HSI value in spring were primarily covered the north of latitude 33°30′N and the west of longitude 122°15′E and the south of latitude 32°45′N and the west of longitude 122°15′E. The peak value of the HSI were observed in the northern region of the core area among the MPAs. The HSI for the central region of the MPAs and the waters located east 122°30′N exhibited a low value. The autumnal peak of the HSI center was situated within the sea areas ranging from 32°15′ to 34°15′N and from 122°00′ to 122°45′E, which predominantly located in the southern region of the core area and exhibited a noticeable eastward shift in comparison to the spring season. The appropriate habitats of L. polyactis were found predominantly in the northern regions of the MPAs in spring. The suitable habitat area of the MPAs in autumn exceeded that of spring, thereby potentially enhanced their protective efficacy.

Polychlorinated biphenyls (PCB₁₅₃) is a typical lipophilic persistent organic pollutant that can bioaccumulate in aquatic organisms and undergo trophic transfer through food chains, thereby pose potential risks to human health. In this study, the physiological and ecological response of Artemia salina in Bohai Bay to intermittent PCB₁₅₃ stress were investigated under waterborne and dietary exposure modes. The experimental setup included a control group, two waterborne exposure groups (W-0.2, W-2) and two dietary exposure groups (D-0.2, D-2). Multiple biological indicators including survival, growth, ingestion, reproduction and antioxidant indices were measured. The results showed that the body length of Artemia in the W-2 group was the lowest and significantly lower than that in the control group from day 6 to day 9 (P<0.05). On day 2, the dietary exposure group exhibited a lower grazing rate compared with the control and waterborne exposure groups. From day 6 to day 14, both grazing rate and filtration rate reached the minimum values in the W-2 group. Additionally, the W-2 group showed the lowest female proportion but the highest reproductive rate whereas the D-2 group had the earliest initial reproductive time. For antioxidant responses, waterborne exposure groups displayed a significantly decreased SOD activity and an elevated MDA content relative to other treatments (P<0.05). All PCB₁₅₃-stressed groups presented markedly reduced GSH content and GST activity compared with the control (P<0.05). In conclusion, both waterborne and dietary PCB₁₅₃ exposure significantly affected the growth, ingestion, sex ratio, reproduction, and antioxidant defense system of Artemia. PCB₁₅₃ stress inhibited individual growth and grazing capacity, increased male proportion, advanced reproductive initiation, improved reproductive output, and induced obvious antioxidant system disturbance in Artemia.

Nitzschia palea is an eutrophic diatom widely inhabiting freshwater ecosystems, which shows a strong adaptability to polluted water bodies, especially highly nitrified ones. In this study, we characterized the transcriptome of N. palea inhabiting Danjiangkou Reservoir with Illumina high-throughput sequencing technology. We obtained more than 42 573 060 clean reads, 88.53 Gb effective bases, and 79 224 transcripts in total after de novo assembly. Genes were annotated and metabolic pathways were analyzed with bioinformatic methods including NR annotation, GO annotation and KEGG pathway annotation among others. When focused on the nitrogen metabolism, a total of 78 unigenes involved in nitrogen regulation were identified, which encoded 13 enzymes functioning in nitrogen metabolism. A total of 19 538 differentially expressed genes (DEGs) were identified among different concentrations of ammonia nitrogen, among them, the most significantly down regulated DEGs encode glutamine synthetase, carbamate kinase, nitrate reductase, nitrate transporter and carbamoyl phosphate synthetase while the most significantly up regulated hydroxylamine reductase. The expression of carbonic anhydrase gene increased first and then decreased. Our findings provided a reference to further elucidating the molecular regulatory mechanism of N. palea in responding ammonia nitrogen and a basis for accurately monitoring the dynamic change of nitrogen nutrition in Danjiangkou Xichuan Reservoir and protection of water quality and safety of Danjiangkou Reservoir.

Betaphycus gelatinus is an important macroalga with important economic and ecological value. B. gelatinus is one of Eucheumatoid, which is used as the raw material in carrageenan industry world widely. At present, wild B. gelatinus is used as seed alga in the cultivation, resulted in the single germplasm and poor adaptability to environmental changes. In current study, the spontaneous mutant green B. gelatinus CJ2205 was isolated and used to analyze its differences in pigment content, temperature, light adaptability and photosynthesis compared from the wild type red B. gelatinus YS. It was found that the decrease of phycoerythrin content is the main reason for the green color. At the light intensity of 60 μmol/(m²·s), the phycoerythrin content of green strain (189.80±11.90 μg/g) was significantly lower than that of red strain (622.42±13.78 μg/g) (P<0.05), but no significant difference was found in other pigments. Under the conditions of temperature, light intensity and superposition of light intensity and temperature, the specific growth rate of green strain was significantly higher than that of red strain (P<0.05). Under the conditions of both light intensity and temperature, the Fv/Fm, NPQ, Y (Ⅱ) and rETR of green strain were significantly higher than those of red strain (P<0.05), especially at 30 ℃ and 380 μmol/ (m²·s). At the aspect of light quality, the SGR of green mutant was significantly lower than that of red wild-type B. gelatinus. Compared with the red strain YS, the green strain B. gelatinus CJ2205 had more advantages in the environment of high temperature and high light (30 ℃ and 380 μmol/(m²·s)). Our findings provided a reference for the studies of temperature and light adaptation of green B. gelatinus mutants.

Phascolosoma arcuatum has a high nutritional value, and it is generally believed that the nutritional value of the wild individuals is higher than that of the cultivated ones. Additionally, digging for the worms in mangrove areas has certain impacts on both mangrove plants and wild resource of P. arcuatum. In this study, we compared and analyzed the protein, fat, fatty acids and amino acids of the muscles of wild and cultivated P. arcuatum in mangrove areas, and evaluated the essential amino acids nutritionally. There was no significant difference in the general nutritional components and amino acid contents between the two groups (P>0.05). However, the essential amino acid index (EAAI) in the muscle of the cultivated P. arcuatum (1.15) was higher than that of the wild (0.98), and the concentrations of C18:0 and C20:4 (n-6) were significantly higher in the muscles of aquacultured P. arcuatum (P<0.05). Sixteen kinds of amino acids were detected each group, and the content of glutamic acid (Glu) was the highest, which was followed by Pro, Asp and His in order. The concentration of essential amino acids (EAA) was 54.0 and 50.9 mg/g, respectively. The concentrations of non-essential amino acids (NEAA) and flavor amino acids (DAA) were 138.2 and 124.6 mg/g, respectively. The concentration of taste amino acids (DAA) was 100.5 and 93.3 mg/g, respectively. These results indicated that the nutrient compositions of cultivated P. arcuatum was similar or even higher than that of the wild. Moreover, the difference in the nutrient composition indicated that the nutritional value of cultivated P. arcuatum can be improved through optimizing the nutrient composition of its diet.

The rapid development of methods and techniques of obtaining the information of phytoplankton dominant phylum in a large area has important application value in marine carbon cycle, marine ecosystem and red tide monitoring. The one-dimensional discrete wavelet transform (DWT) and Mallat fast algorithm were adopted. Meyer selected as wavelet function. The phytoplankton absorption spectra were decomposed by DWT and obtained 8-level wavelet detail signals. The combined signal of the decomposed details was used as the characteristic spectrum, which was combined with the similarity index to determine the dominant phytoplankton phylum. Firstly, this method was applied to the phytoplankton absorption spectra measured in European waters and the Red Tide waters in the East China Sea, to effectively extract the dominant phytoplankton phylum in natural water and obtain the alternation process of dominant phytoplankton phylum in the Red Tide waters. Then, the method was applied to the phytoplankton absorption spectrum inverted from the remote sensing reflectance, and the dominant phytoplankton phylum of the red tide near the Yangtze River Estuary and the Pearl River Estuary was correctly extracted. The application of DWT in satellite remote sensing data provided a potential and effective technical method for obtaining dominant phytoplankton phylum information of large-scale oceans. The following research work will apply DWT to hyperspectral remote sensing data (including drones and satellites) to further test the effectiveness of the method.

Groundwater nitrogen pollution has become an important environmental geological problem. In order to solve the problems of high construction difficulty and poor treatment effect of nitrate pollution, such as permeable reactive barrier and bio-aeration, we proposed an in situ treatment technology of nitrate pollution in groundwater, which uses groove to bury additional carbon source. According to the hydrogeological conditions and measured reaction parameters in Dagu River, Qingdao, a numerical model of groundwater movement and reactive pollutant migration in profile is constructed. Under the action of groove leaching, a local groundwater flow field will form near the groove, and the dissolved organic carbon (DOC) released from the slow-release carbon material will vertically migrate to the deep aquifer and denitrify the nitrate pollutants in the aquifer. The restoration of nitrate pollution in aquifers in the region was well realized. Through the optimization of three process parameters, the optimal leaching rate, groove width and the dosage range of slow-release carbon material are 0.70~0.75 m/d, 5.5~6.0 m and 45~55 kg/m³, respectively. Average nitrate concentration (C-NO^-₃) in polluted aquifers can reach the treatment standard (below 50 mg/L). Relative control area (a value) can reach above 70.0%.

Under the combined action of terrestrial facies and marine dynamics, the shoreline changes of the Yellow River Delta is very active. In order to explore the influencing factors of the spatial-temporal changes of the shoreline of the Yellow River Delta, this study collected the satellite remote sensing images of the Yellow River Delta in different years from 1976 to 2020. Based on RS and GIS technology, the changes of the shoreline length, fractal dimension and end point rate of the delta area were analyzed. The evolution law of silt and erosion along the delta area in recent 50 years was analyzed . The results showed that between 1976 and 2020, the change of the shoreline length of the Yellow River Delta could be divided into three stages, and the overall trend was increasing. There was a significant positive correlation between fractal dimension and shoreline length. The shoreline changes of different typical coastal sections had spatial-temporal heterogeneity. The maximum siltation rate and the maximum erosion rate appeared at the estuary southeast sandspit. The maximum siltation rate occurred between 1991 and 1996, which was 620.73 m/a. The maximum erosion rate was -662.41 m/a, which occurred between 1996 and 2001.

The coastline is an important national land resource and an important indicator of the ecological security of the coastal zone. In this paper, Rizhao in Shandong province, an important port city in the north, was selected as the research object. Based on Landsat remote sensing images, the spatial information of the coastline was extracted in 9 phases from 1978 to 2023. The process of changes, as well as the spatiotemporal differentiation characteristics, in length, shape, longitudinal, and type structure of the coastline were analyzed systematically, and the main driving factors of the coastline change were explored deeply. The results showed that over the past 45 years, the coastline changes in Rizhao had shown obvious characteristics of spatiotemporal differentiation, and the phased changes of the coastline were basically consistent with the phased development of Rizhao from a port to a city. The length of the coastline had increased from 92.25 km to 219.14 km, showing a trend from slow growth, to rapid growth, and then to slowdown in growth rate, with 2000 and 2015 as the breakpoints. Coastline tortuosity continued to increase, and the positional changes of the coastline were dominated by seaward expansion. The major changes concentrated in the coastline sections of Shijiu port and Lanshan port, and the fastest growth period was the rapid construction period of Rizhao port (2000-2015). The structure of the coastline had gradually changed from sand-dominant to port-and-dock-dominant, with the natural coastline decreasing from 77.61 km to 38.22 km. The process of coastline changes in Rizhao was the result of the combination of natural, human and policy factors, in which human activities, mainly the construction of Rizhao port and the development of port-related industries, were the dominant factors.

To obtain the spatial and temporal variation characteristics of maritime search and rescue difficulty (MSARD) with long time series data and the effect of impact factors in the Yellow Sea, which provides the basis for the optimization of the resource deployment and numerical model, several methods were used for the research in this study such as the empirical orthogonal function (EOF) analysis, power spectrum analysis and multiple linear regression fitting, etc. The temporal and spatial characteristics of MSARD were analyzed in the Yellow Sea based on the observation-reanalysis data from 1993 to 2022, while the spatial and annual variation characteristics of MSARD were studied in the four important ports of the Yellow Sea based on the observation data from 1997 to 2022. Maritime search and rescue success rate (hereinafter: success rate) was defined to represent MSARD in the paper, and the results were as follows. In the Yellow Sea, the cumulative variance contribution rate of the first two modes of EOF analysis was 94.39%, which means the main process of the success rate variation could be reflected. The spatial values of EOF1 were all positive and with the decreasing trend from the north to south, while the significant periods of time coefficient were 1.1 years and 12 years. The impact factor of EOF1 was the linear effect of the water temperature, wind speed and the wave. The significant seasonal variation characteristics were shown in the annual distribution of success rate, while the high value center appears in the sea area near Cheju island except summer. The annual average data of success rate had a 12-year decline cycle (from 1999 to 2010) and a 11-year rising cycle (from 2010 to 2020) in the three partial sea areas and the whole sea area. In the four ports area of the Yellow Sea, the variance contribution rate of the first mode of EOF analysis was 97.5%, which means the main variation process of the annual daily average data of success rate could be reflected. The result showed that the success rate was rising from the end of May to early November and decreasing in other months. The main impact factors of the success rate in each port area were as follows: the water temperature and wind speed in Dalian port, the water temperature, wind speed and wave in Yantai port and Qingdao port, the water temperature in Rizhao port.

In order to deeply study the characteristics of offshore current in autumn in Fangchenggang, a quasi-harmonic analysis was carried out at six stations in Fangchenggang port and bay estuary by introducing the difference ratio relationship. The results showed that in autumn, diurnal current was dominant in the Fangchenggang Bay, and semi-diurnal current existed in some sea areas. In the bay, the past recurve flow was dominant, while in the mouth of the bay, the rotation flow was dominant. The direction of residual current movement was mainly east-south (SE) in the bay and west-south (SW) in the bay mouth. The residual flow velocity was distributed from surface to bottom, and the residual flow decreased gradually. The residual flow velocity was the highest in the east bay, and in the inner bay of the west bay it was smaller than that in the east bay, and the residual flow at the headland at the top of the bay was smaller. The formation mechanism of tide and residual current, wind and runoff into the sea had influenced in the water transport in the bay, but they did not play a leading role. The topography of the headland in the bay should be one of the main factors. In addition, the continuous input of water from the South China Sea to the east of the Qiongzhou strait was an important basis for maintaining the westwards transport of Fangchenggang Bay estuary.

In this paper, the current data of 6 stations near Qianliyan island and 6 time periods in summer and winter were measured. The plane distribution, vertical distribution and seasonal characteristics of tidal current and residual current in the study area were obtained by analyzing the current data. The wind data and residual current in the synchronous observation period were compared, and the response law of residual current to wind was obtained. The analysis showed that the tidal current in the study area was a regular semi-diurnal tidal current. The form of tidal current movement was dominated by rotating flow, and the rotation direction was counterclockwise. The rotation direction of each layer of each station in the vertical direction was the same. The direction of the trend was W-E ; the average velocity of flood current was less than that of ebb current. The average tidal current velocity in summer was greater than that in winter. The flow velocity in spring tide period was greater than that in neap tide period. The flow velocity gradually decreased from the surface to the bottom, and the distribution of the flow direction on the vertical line was relatively consistent. The residual flow velocity in summer was greater than that in winter. The distribution of residual current in summer was basically consistent with the direction of tidal current, and it was mostly N-S direction in winter. In winter, the residual flow in the vertical direction of each layer was basically the same ; the vertical distribution of flow direction in the neap tide period in summer was relatively large, and the consistency in the middle tide period was strong. The wind in the observation period of the summer neap tide was dominated by the southeast wind, and the winter neap tide was dominated by the northwest wind. The direction of the surface residual current during the neap tide period of each station was consistent with the statistical characteristics of the wind. The response of the residual current to the wind in the winter neap tide period was greater than that in the summer.

Wind wave is an important hydrodynamic factor affecting flood control, water operations and water environment health in lake Hongze. The variation characteristics and influencing factors of wind wave in lake Hongze were analyzed by use of field monitoring and numerical simulation. The results showed the increase of wind speed would lead to the increase of wind wave intensity in different lake areas. At the same time, wind speed and water level would restrict each other, so that the increasing trend of wind wave intensity would gradually slow down with the increase of water level or wind speed. The lake current caused by the large amount of water entering and leaving the lake during the flood season would significantly affect the distribution and intensity of wind wave in lake Hongze. With the enhancement of the lake current, its influence range gradually expanded from the lake outlet to the waters of lake Chengzi and Lihewa, and the areas with strong influence were mainly distributed in the water passages of the Huaihe river passing through lake Hongze. Through the monitoring and simulation of wind wave in the overflow area of lake Hongze, the influencing factors of wind wave in lake Hongze were comprehensively and systematically analyzed, which provided important reference and basis for understanding the influencing factors of wind wave in the overflow lake.

Promoting the structural adjustment of freshwater aquaculture and protecting the ecological environment are key directions to and measures for achieving a green development of freshwater aquaculture. The economic development model of Chinese freshwater aquaculture industry urgently requires a dynamic and green transformation for shifting from factor intensive investment to green total factor productivity improvement. In this article, we used the SBM-GML index method to calculate the green total factor productivity and its decomposition terms of freshwater aquaculture in 30 provinces of China from 2011 to 2020, and analyze their regional differences. From 2011 to 2020, the freshwater aquaculture industry in 30 provinces of China was able to achieve a high efficiency in the production process and better achieve the goal of green environmental protection. However, there are problems such as insufficient rational allocation and utilization of freshwater aquaculture resources, and the need to improve production and management efficiency. There was a significant difference in green total factor productivity of freshwater aquaculture among the eastern, central, western and northeastern regions. A decreasing trend was found among the central, eastern, western and northeastern regions. In order to achieve a coordinated growth among the four major economic regions of green total factor productivity in freshwater aquaculture, we proposed the following approaches: optimizing the allocation and utilization of freshwater aquaculture resources; improving production and management efficiency; promoting technological progress; and utilizing regional advantages to achieve differentiated development and promote green development of freshwater aquaculture.

In order to analyze the conservation effect of the marine ranch constructs on the fish resource of the eastern coast of Haikou, the trawl fishing gear was used to clarify the background and track the marine ranches constructed in Sept. 2019, Apr. and Sept. 2020 and Nov. 2021. The investigation included fish species composition, resource density, eco-exergy and community structure characteristics, which was evaluated by indexing the relative importance and determining the dominant species. A total of 51 fish species were identified, which belonged to 11 orders, 29 families and 41 genera. The proportion of species in reef area increased from 45.45% to 64.28%. The resource density after reef placement was significantly higher than that before (P<0.05), and the resource density in reef area was significantly higher than that of the control area (P<0.05). The fish species inhabiting middle and lower water layers such as Gerres filamentosus and Nuchequula nuchalis became the mesopelagic demersal species. There was a significant difference in the community structure characteristic index and eco-exergy quality value between the reef and contrast area after reef placement (P<0.05), indicating that the marine ranches played a significant role in gathering fish resource, improving community structure and increasing biodiversity. Our findings provided a scientific basis for the rational construction and marine ranch planning of Hainan.

Artificial reefs exhibit enormous ecological benefits as an important engineering facility for marine ecological restoration. In this study, contents of six heavy metals (Cu, Pb, Zn, Cd, Hg and As) in sediments from Dongshan sea water, Huizhou city, before, during and after the reef placement were analyzed for understanding the change of ecological risk and elucidating relevant controlling factors and indications to ecological benefits. Results showed that: 1) The large variation of contents of Cu, Cd, Hg and As in sediments between before and after the placement of reefs reflects that the sediment composition was influenced. 2) Based on Pearson correlation analysis, the contents of Hg displayed a significant positive correlation with organic carbon (OC), suggesting that the variation of Hg content was associated to OC obviously. In addition, the significant positive correlation between the contents of Cu and Zn in sediments, suggesting similar behavior and same origin of these two elements. 3) The SFI values of Hg increased greatly with the reef placement. After the placement of reefs, the RI values decreased. 4) Overall, artificial reefs showed a positive response to ecological benefits for Cu and Cd contents in sediments, but contrary for Hg and As.

Seagrass beds are one of typical three major coastal ecosystems. Seagrasses are higher plants that complete their entire life cycle in seawater. In this study, we focus on tropical seagrasses, including Thalassia hemprichii, Enhalus acoroides, Halophila ovalis, Halophila beccarii, Halodule uninervis and Cymodocea serrulate, and examined the anatomy of their nutritional organs under an optical microscope. The tropical seagrasses have the following adaptive characteristics, well-developed aeration tissues enhancing their gas exchange and increasing their buoyancy, underdeveloped mechanical tissues reducing the impact of waves, leaf blades with thick-walled cells to improve the leaf flexibility, abundance of lignified cells in the stems enhancing stem stability, and vascular cylinders of the roots surrounding a zone called the Casparian strip which regulate substance transportation. Our findings should enrich the database of morphological changes in seagrasses and provide fundamental data for seagrass bed restoration and conservation.

The precise classification of coastal salt marsh plant populations is conducive to coastal ecological monitoring and biodiversity research. Taking some areas of Yancheng Wetland Reserve as the research areas, the multi-spectral unmanned aerial vehicle (UAV) images of four seasons were used to classify the plant populations in different seasons and among different combinations with the classification method in combination with object-oriented XGBoost. The overall accuracy of single-season phase classification ranged from summer to autumn, spring and winter gradually from high to low. The overall accuracy reached up to 85%, and the Kappa coefficient was 0.83. The overall accuracy of multi-season combination classification was the highest in spring, summer and autumn combination with an overall accuracy of 91.1% and a Kappa coefficient of 0.90. Spartina alterniflora, Suaeda salsa and Miscanthus sacchariflorus had the highest classification accuracy in autumn, Cogongrass, Artemisia capillaris and Calamagrostis epigeios had the highest classification accuracy in summer, and Phragmites australis had the lowest classification accuracy in single season. The classification accuracy of Phragmites australis increased by 16% after the combination of four seasons. The contribution distribution each feature in single-seasonal classification was different. DSM had a high contribution each seasonal classification. The feature importance of the four seasons combination classification ranged from elevation feature to principal component transformation, spectral reflection feature, vegetation index and texture feature from high to low.

Marine ranching policies are important for ensuring marine food supply and ecological safety, promoting fishermen's conversion to other industries, and promoting the integration of one, two and three industries. The analysis framework was constructed from three dimensions, policy tools, policy objectives and policy effectiveness. The content analysis method and the Policy Modeling Consistency index model were used to analyze quantitatively 71 marine ranching policy documents issued by the central government and ministries from 2006 to 2023. The policy objectives and tools of marine ranching policy are unbalanced, which are characterized by the unbalanced role of policy objectives and the distribution of policy tools that are environment-oriented and demand-oriented. The overall performance of policy effectiveness is good, but there are still problems such as inadequate integrated planning of long-, medium- and short-term policies, low level of existing policies, and incomplete description of policy contents from macro-, medium- and micro-perspectives. It is necessary to improve the structure of policy objectives, rationalize the configuration of policy tools, and improve the overall policy effectiveness so that the high-quality development of marine ranching can be promoted.

Although the economic development of Chinese coastal areas has made a great progress, there are still serious problems of unbalanced and uncoordinated development among regions. In this study, we used panel data from 11 Chinese coastal provinces and cities to construct an evaluation index system for the high-quality development of the marine economy and to measure its index. The modified gravity model was used to identify the regional correlation of high-quality development of marine economies, construct the spatial correlation network of high-quality development of marine economies, and further analyze the structural characteristics of the correlation network and its key influencing factors. Our findings provided the support for promoting integrated development among regions to achieve a high-quality development of the marine economy.

Scientific and technological innovation is the core driving force for high-quality development, and marine innovation is crucial to accelerating the building of a maritime power. Based on ecological theories, this paper established niche suitability evaluation system and evaluation model for regional marine innovation ecosystems. The data used was from 2011 to 2019 to measure the niche suitability and evolutionary momentum of marine innovation ecosystems in Liaoning, Tianjin, Hebei, Shandong and Jiangsu provinces around the Yellow and Bohai seas. The results showed that the location suitability level of Shandong and Jiangsu was high, while the overall level of other regions was low. The matching development of each subsystem was the necessary condition to improve the overall development level. The results of evolutionary momentum indicate that marine innovation ecosystems had a good prospect in the future. Therefore, this paper put forward countermeasures and suggestions from the aspects of cross-regional cooperative development, improving innovation ecological environment and promoting the coordinated development of innovation ecosystem.

The fishing moratorium is one of the most widely applied fishery management measures. Evaluating the effect of a fishing moratorium scientifically and accurately has a great significance on the improvement of policies and sustainability of fishery resource. Based on literature sample data related to the evaluation of fishing moratorium in the Web of Science Core database from 2000 to 2022, Citespace bibliometric software was used to systematically review the research status and frontier hotspots in the field of fishing moratorium evaluation through various methods including institution clustering analysis, keyword clustering analysis, keyword co-occurrence analysis, and literature co-citation analysis. Since the beginning of this century, studies on the evaluation of fishing moratorium effects have presented a development trend from low and stable to rapid rise to high and stable. Scientific institutions from countries and regions such as the United States, Australia and the European Union were the main forces in this field while studies by Chinese institutions in this field still needs to be strengthened. Internationally, studies in the field emphasized the importance of biomass, which was followed by biological characteristics. Ecosystem-based fishery management was the trend for future studies. Besides, economic and social impacts should also be considered. We suggested that future studies should focus on diversification and systematization; new research methods should be developed; international cooperation should be strengthened, and a multidimensional evaluation system integrating ecological, economic and social factors should be constructed so that a basis can be provided for the scientific conservation and management of fishery resources.

Nuttallia olivacea is a bivalve shellfish species with certain economic and ecological values in the coastal areas of East Asia. It is delicious and abundant in nutrition, rich protein, unsaturated fatty acids and various minerals, making it favored by consumers. Meanwhile, as a key member of the benthic community in estuaries, N. olivacea participates the material cycling and energy flowing, significantly purifying the surrounding sediment, and effectively maintaining the stability of ecosystem. In recent years, the continuous impacts of the global climate change on the marine ecosystem and continuously increasing market demand have caused a sharp decline in resource. Accordingly, the studies relative to the resource protection and development, reproduction biology and aquaculture technology are receiving intensive attentions. In this paper, we reviewed the research findings on the biology, ecology and breeding techniques of N. olivacea, and explored the management strategies and future research directions, aiming to provide beneficial references for the scientific understanding, resource conservation and sustainable development of this species.

The marine space resources of our country are extremely scarce, and the importance of sea parcel boundary charts as the basic data for maritime management is increasing. The compilation and drawing technologies of regulated sea parcel include the definition and mapping of sea parcel boundary. Currently, the sea parcel compilation standardization system is relatively complete, and the mapping techniques of sea parcel are relatively mature. However, the researches on sea parcel boundary definition technology are scarce. In this paper, we enhanced the accuracy and convenience of sea parcel boundary definition from four aspects, data acquisition, marine utilization analysis, sea parcel definition and area computation. We also summarized the use of various softwares such as AutoCAD and ArcGIS in the definition of sea parcel boundary in coordinate system and projection transformation, planar boundary definition and definition of boundary points for curved structures. In addition, we discussed preliminarily the definition of structures and three-dimensional rights involved in the sea parcel boundary definition. It is recommended to define as permeable structures if the permeability exceeds 70% under the condition of high tide during the spring tide period, and as impermeable structures otherwise. Vertical marine longitudinal sections and typical cross-sectional marine schematic diagrams should be drawn during the sea area use assessment phase to satisfy the three-dimensional rights determination.