The research and development of radar systems generally require repeated tests. In order to solve the problem of wasting a lot of manpower and material resources in field tests, this paper established an echo simulator mainly based on sea clutter, which was used for radar tests to reduce costs. Based on the Elfouhaily spectrum, the nonlinear dynamic sea surface was established by using the Choppy wave model,and the sea surface was divided into different resolution units by using the grid mapping method. This paper combined the gridded sea surface with the backscatter characteristics of the echo to generate a simulated echo for the first time. And in the simulation process, an algorithm for correcting the grazing angle based on the characteristics of the waves was proposed. Finally, the simulated echo was analyzed and fitted with the measured and theoretical data, which proved the effectiveness of the simulated echo.

Based on the observations originated from satellites and archived in IFREMER, the sensitivity analysis and adaptive modification were conducted on the wind input source term, dissipation caused by white-capping and bottom friction and their parameters of SWAN model with unstructured mesh grid in the China adjacent sea. The applicability of the modified model was validated by performing 25 years numerical simulation. Results indicated that the reanalysis wind speed data from NCEP were consistent with observations in China sea and could be used as the wind forcing for wave simulation. The Komen pattern with the coefficient of 1.86×10^-5 for both the wind input source term and the dissipation caused by white-capping was considered as the optimal parameter combination for this sea area. As for calculating the dissipation due to the bottom friction, COLLINS model with default parameter was the most suitable. And the calibrated SWAN model was stable and could simulate the significant wave height more accurately in the China adjacent sea.

The underwater topography and hydrodynamic conditions of the coastal nuclear power plant area are complex and changeable, and the transport and diffusion of thermal discharge and liquid effluent are affected by the current flow and temperature difference reflow. This paper briefly introduced the research methods of thermal discharge and liquid effluent of coastal nuclear power plants in China. The research methods such as theoretical analysis, numerical simulation, physical testing, prototype observation and post-evaluation were systematically reviewed.The research progress of various research methods was given, and their advantages and disadvantages were analyzed. Combined with the respective characteristics of the mathematical model and physical model of thermal discharge and the actual operation of the project, it is preliminarily discussed that the physical model and mathematical simulation should be combined and complement each other. The physical model should be used to simulate its hydraulic and thermal characteristics in the sea area near the drainage outlet, and the numerical calculation should be used in the distant sea area. In order to further improve the safety of the project and to meet the protection requirements of the ecological environment, the work of prototype observation and post-engineering evaluation should be strengthened.

Since the 21^st century, the coastline of Laizhou Bay has changed significantly due to coastal reclamation activities such as port dam construction and aquaculture dikes, which have caused the change of the hydrodynamic environment of the bay. In order to investigate the response of the tidal prism and water exchange capacity of Laizhou Bay to its coastline change during the past 20 years, the influence of the coastline change on tidal prism and water exchange capacity was analyzed with two-dimensional flow and advection-diffusion models for the two typical years, 2000 and 2020. The results showed that from 2000 to 2020, aquaculture dikes have caused an increase in the potential energy of tidal waves, and the maximum possible tidal range of Laizhou Bay also shows an increasing trend. The head of the bay between Weifang Port and Guangli Port increased significantly with the maximum increase of 8 cm. The spring tidal prism was decreased by 2.91%, the neap tidal prism by 1.42% and the mean tidal prism by 2.33%, and decreased bay area was the main reason for the decrease of tidal prism. The decrease in the sea area of the bay has led to a reduction in its self-cleaning capacity and water exchange, increasing the bay half-life time by 15 days. As for the local water exchange capacity, the water exchange capacity in the western part of the bay was decreased by port dam construction and a deposition trend of the Yellow River Estuary, resulting in an increase of half-life time in the western part of the bay by 40 d.

The “14th Five-Year Plan” emphasizes that the development level of the three major ocean economic spheres should be comprehensively improved to achieve balanced development of the whole ocean area. Promoting the high-quality development of marine economy and marine ecological security in the three major marine economic circles, and narrowing the gap between the coordinated development of the regions are the key link to promoting the model of marine strongholds to the model of comprehensive and balanced development of the regions. This paper examines the spatial and temporal evolution characteristics of the spatial correlation patterns and the degree of synergistic promotion of MHQ and MES in China′s three major marine economic circles using the coupled coordination degree model and spatial auto correlation analysis. It is found that: (1) The level of coupling and coordination between the two systems has been fluctuating and increasing, and the whole area is in the transition stage from the decline of disorder to the primary coordinated development. (2) There is a significant unbalanced development trend in the level of synergistic development of the “three circles”, and the overall spatial distribution shows a pattern of “East > North > South”. (3) The spatial correlation of the coupling and coordination degree is significant, and the correlation degree increases and then decreases over time; the spatial correlation pattern of the coupling and coordination degree shows certain spatial clustering characteristics.

Under the action of waves and currents, offshore wind power foundations may experience local erosion, resulting in an increase in the length of the foundation cantilever, which seriously affects the stability and safety of the foundation. To investigate the local erosion characteristics of offshore wind power tripod foundations under the combined action of waves and currents, local erosion tests were conducted on tripod foundations with different installation angles in a wave current tank. The characteristics of local erosion depth, influencing factors, and the morphology of erosion pits were studied. The research results indicated that under the action of individual waves, the central column provided a certain protective effect on downstream piles, weakening the development of erosion. When waves and currents acted together, waves provided drag force on the bottom bed, while water flow provided sediment transport force, resulting in a significant increase in scouring depth. When the installation angle was 30°, the water blocking effect on the double pile side of the tripod was greater, and some water flow was directed towards the single pile side, resulting in an increase in the scouring depth. As the flow velocity, wave height, and KC increasing, the depth of erosion around the foundation gradually increased. An empirical formula using KC to predict the equilibrium scour depth had been proposed, which could accurately predict the equilibrium scour depth of local scour on a tripod foundation under wave action and wave current combined action.

Based on the monthly average wind speed and significant wave height of the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 from 1979 to 2019, the temporal and spatial characteristics of wind speed and significant wave height were analyzed. The Mann-Kendall test method was used to analyze its inter-annual variation and the Empirical Orthogonal Function (EOF) analysis method was used to study the spatial distribution characteristics. The results showed that: (1) The wind direction of the South Atlantic Ocean rotated counter clock wise with 30°S and 10°W as the center. The areas with high wind speed were mainly controlled by the southeast trade wind belt and the west wind belt, and the low value areas were controlled by the subtropical high and low pressure zone. The wind speed in winter was higher than other seasons, and the wind speed and wind direction distribution throughout the year were related to the seasonal changes of the weather system. (2) There was a strong correlation between wind speed and significant wave height, and both of them were distributed in a zonal ring shape. The overall significant wave height was the largest in winter and smaller in summer. (3) Mann-Kendall test results showed that the inter-annual variation of wind speed and significant wave height both showed an upward trend. The wind speed had abrupt changes around 2006 and 2009, and the significant wave was higher than around 1994 and had abrupt changes. (4) The first mode of EOF of the wind speed showed that the trade wind belt-westerly belt and the subtropical high belt-low pressure belt were distributed in the opposite pattern. The wind speed of the former showed a significant upward trend, and the latter showed a downward trend. The first modal of EOF of the significant wave height showed that the significant wave height variability in the north sea area of 60°S was the positive phase, and the south was the negative phase. The significant wave height in the positive phase region had a significant increasing trend, and the significant wave height in the negative phase region had a significant decreasing trend.

International BGC-Argo, which has been implemented officially since October,2016, is the first project that have the capability to monitor the global biogeochemistry. Therefore, understanding the number of its observation, the characteristics and the distribution of the data is very helpful for the subsequent use fully to improve our cognition on ocean acidification, marine carbon cycle as well as hypoxic zone variation, which influence the health of marine ecosystem significantly. In this paper, systematic statistics were made about the number and distribution of Argo dissolved oxygen data, the types of buoy data and the density of the data in the global ocean as well as several experimental areas. The results showed that until the end of 2019, the total number of dissolved oxygen profiles, which were acquired by BGC-Argo buoys in global ocean, accumulated to 1 hundred and 70 thousand and was increasing by 10 thousand per year. The spatial distribution of dissolved oxygen observation data was uneven. Only 36.8% of global grid points met the analysis need of spatial resolution of 1 degree objectively, and this kind of data which met the resolution need was more observed in five experimental areas.

In the design phase of a coastal power plant, numerical simulation is usually used to predict the influence scope of thermal water discharge needing the realistic heat transfer coefficients. The coefficient was almost judged based on experience and lack of systematic research actually so far. To solve this problem, this paper analyzed the comprehensive heat dissipation of the Meizhou bay power plant, and proposed a method for measuring the coefficients. The measured data showed that heat transfer coefficients fluctuated dramatically during high and low tides, so the empirical constant was not completely reliable with deviation. Conversely, the model results could reflect the temperature rise change more accurately caused by external factors, which was more consistent with the measured. This simulation method increased the accuracy of the heat transfer coefficients, and it had an important progress in rationally determining the influence of thermal water drainage.

Based on the FVCOM ocean model, a high-resolution three-dimensional ocean numerical model was established for the adjacent sea area of Liuheng island. The main characteristics of tides and tidal currents in the adjacent sea area of Liuheng island were simulated in detail. The results of the model were in good agreement with the observation data of one tide station and two current stations, which could reflect the movement characteristics of tides and tidal currents in the adjacent sea area of Liuheng island. Meanwhile, main tidal components, such as M₂, S₂, K₁, O₁, M₄ and M₆, and the elliptical spatial distribution of surface tidal currents as well as two shallow water tidal components were given. Finally, the surface flow field and the spatial distribution of residual current in the surface layer, 0.6 layer and bottom layer were analyzed. The results showed that M₂, S₂ and O₁ were high in the south and low in the north, and the amplitudes of M₂, S₂ and O₁ were 115-145 cm, 15-30 cm and 19-24 cm, respectively. K₁ was 20-30 cm, and the main tidal components propagated in the same direction. At the same time, the spatial distribution and propagation direction were opposite to the main tidal components. Based on the results of harmonic analysis, the tidal pattern coefficient and the maximum possible tidal range were calculated. The whole sea area was characterized by regular semidiurnal tide, and the maximum possible tidal range could reach 600-650 cm in the southern sea area and 450-550 cm in the northern sea area. According to the calculation of tidal asymmetry, the ebb tide speed in the south of Liuheng was higher than that in the north. Under the four tidal conditions, the maximum velocity of the ebb flow field was 22 cm/s, and the maximum velocity of the four main tidal components was 160 cm/s, 60 cm/s, 22 cm/s and 12 cm/s, respectively. The spatial distribution of the ebb flow field was characterized by offshore rotating current and inshore reciprocating current. In the distribution of residual current, the maximum of surface layer, 0.6h layer and bottom layer could reach 25 cm/s at the headland, but the residual current gradually weakened with the increase of water depth.

The wave transformation and the nonlinear characteristics along the coral reef coasts with the effect of tidal current were determined through laboratory experiments. The cross-reef variations of water surface time series, wave height, mean water level, wave nonlinear parameters and higher harmonic waves with both shoreward and seaward currents with and without the effect of tidal current are analyzed. Results showed that the presence of shoreward current causes a forward shift of wave phase on the reef flat while the seaward current leads to a phase lag. With the influence of the shoreward (seaward) current, the wave breaking point moved shoreward (seaward). The transmitted wave height on the reef flat with the shoreward current was larger than that with the seaward current while the mean water level was lower than that with the seaward current. The wave skewness amplitude and wave asymmetry amplitude on the reef flat increased and decreased with the shoreward (seaward) current, respectively, in comparison with the those without the current. The Ursell number increased as the flow direction varies from the seaward side to the shoreward side. Near the reef edge, the seaward current promoted the generation of the high harmonics while the shoreward current reduced the high harmonics. The attenuation of the higher harmonics on the reef flat was the largest in the presence of seaward current, and was the smallest when the shoreward current exists.

Return value calculation of extreme marine environmental parameters induced by typhoon is of great significance for engineering disaster prevention. The rationality of the calculation depends on the sampling method and probability distribution model. In this paper, the sampling method of typhoon process was combined with exponentiated Weibull distribution model. A Poisson-exponentiated Weibull compound extreme value distribution model was established based on the compound extreme value distribution theory. This new distribution model was applied to the probability prediction of extreme marine environmental parameters under typhoon, and the corresponding return values were calculated. The study showed that the annual typhoon frequency at the selected calculation points conformed to Poisson distribution, and the exponentiated Weibull distribution fitted the sequence of extreme wave height induced by typhoon well. It was reliable to calculate the return values by using Poisson-exponentiated Weibull compound distribution model. This compound model was more perfect in physical and statistical sense, and the calculation results were stable and reasonable.

Saline tolerant plant plays an important role in marine aquaculture wastewater treatment and seawater agriculture development. In order to explore the salt tolerance and nitrogen and phosphorus purification ability of S. portulacastrum, in this study, we carried out the indoor hydroponic experiments of S. portulacastrum salinity treatment and nitrogen and phosphorus concentration treatment. S. portulacastrum plants were grown in Hoagland nutrient solution at salinities of 0, 10, 20, 30 and 35, respectively, in salinity experiment, and were cultured in artificial seawater with N∶0 (P∶0.5) mg/L, N∶1 (P∶0.1) mg/L, N∶5 (P∶0.5) mg/L, N∶20 (P∶2) mg/L, N∶50 (P∶5) mg/L, respectively. The treatment period was 20 days. We found that 1) the absorption effect of nitrogen and phosphorus was obvious under the condition of medium and low salinities (0～20) while the absorption effect was significantly weaker than that of the low-medium salinity groups under the condition of high salinities (30～35) (P<0.05); 2) the Na⁺ content in S. portulacastrum tissues increased continuously with the increase of salinity while the K⁺ content showed a decreasing trend; and the effect of nitrogen and phosphorus concentration on the content of Na⁺ and K⁺ was not obvious; 3) under the conditions of all nitrogen and phosphorus treatments, S. portulacastrum grew normally and showed a high nitrogen and phosphorus removal ability, significantly reduced the nitrogen and phosphorus concentrations in the water. S. portulacastrum had a strong salt-tolerance ability and effectively alleviated the eutrophication, which can be used to purify the aquaculture wastewater and improve the aquaculture environment.

Geochemical sensitivity index is an important index to reflect the sensitivity of groundwater system to human activities and natural environment in a region. The geochemical susceptivity index (GSI) is the basis of geochemical susceptibility quantification. In the traditional method, the total amount of elements is directly substituted into the calculation when calculating GSI. The influence of element forms on mineral precipitation and dissolution is ignored, which will lead to inaccurate calculation results. In order to avoid such situation, an improved GSI calculation method was proposed in this paper. The improved method considered the existence forms of elements separately in the calculation process and was applied to the Huangshui river. The results showed that the complexation group would affect the judgment of the geochemical sensitivity index. The improved method took into account the different forms of elements. The presence of abundant forms of C, Mg and S had the greatest influence on the calculation results. This improved method took into account the existing forms of elements, which could improve the accuracy of GSI calculation and advance the quantitative study of geochemical sensitivity.

In order to describe the species composition and taxonomic diversity of fish inhabiting Dongping Lake, downstream of Yellow River, the species composition was analyzed and the taxonomic diversity and G-F diversity indexes were calculated based on the survey data of fish resources from 1979 to 1980 and the survey data of fish from 2020 to 2021. In total, 55 species belonging to 39 genera, 15 families and 8 orders of fish were recorded from 1979 to 1980, and 41 species belonging to 39 genera, 15 families and 7 orders of fish were recorded from 2020 to 2021, among them fish species in Cypriniformes were absolutely dominant. From 1979 to 1980 and from 2020 to 2021, the average taxonomic difference index (Δ⁺) of fish inhabiting Dongping Lake was 77.19 and 79.39, the taxonomic difference variation index (Λ⁺) was 581.9 and 561.5, the family diversity index (F index) was 5.05 and 4.15, the genus diversity index (G index) was 3.70 and 3.65, and the standardized G-F index was 0.27 and 0.12 respectively. Fish diversity of Dongping Lake displayed an overall downward trend. Fish germplasm resources protection and habitat restoration of Dongping Lake should be strengthened.

Disasters such as strong winds and huge waves caused by typhoons have a significant impact on the offshore area of Shandong peninsula. In this paper, by using the third-generation wave model SWAN, the driving field of the model was formed by ERA5 background wind field and the typhoon model wind field nested with Takahashi and Fujita. t formulas. The typhoon waves in the process of No. 9 typhoon "LIKEMA" in 2019 were simulated. According to the simulation results, the distribution of effective wave height, average period and wave age of typhoon wave was analyzed numerically, and the spatial distribution characteristics of typhoon wave during typhoon "LIKEMA" were preliminarily explored, which provided technical support for typhoon wave warning, disaster prevention and mitigation in Shandong province. The research results have certain scientific significance and application value.

CCMPv2, ERA5 and CFSR&CFSv2 are widely used in numerical simulation of wave and tide for their higher resolution in spatial and temporal, however the quality of the reanalysis wind field data is not constant in space. For the China Sea, due to the limited number of measured data, yet no scholar conducts extensive and detailed comparison of wind field data quality within the scope. In this paper, we extract ICOADS measured data from 1998 to 2014 and correct them to 10 meters height uniformly by utilizing anemometer height. Afterwards, the qualities of the three kinds of wind field data are compared firstly from the angle of wind speed and direction within China sea and different sea areas of it, the results show that: (1) The reanalysis wind speed and direction data from CFSR&CFSv2 and CCMPv2 respectively are consistent with measured data best in China Sea; (2) The optimal wind speed and direction data in the specific sea area mostly do not appear in the same wind field. From the angle of wind speed, ERA5 is optimal in area around the Sanba strait, the western Pacific and the northern Part of the South China Sea, and the optimal wind field in other sea areas is CFSR&CFSv2. From the angle of wind direction, CFSR&CFSv2 is optimal for the Bohai Sea, sea area around Fujian and Taiwan and Beibu Gulf respectively, and the optimal wind field in other sea areas is CCMPv2.

In this paper, the species, distribution area and biomass per unit area of macroalgae in the subtidal zone of Gouqi Island, Zhejiang Province, were investigated through acoustic side scanning and SCUBA diving. At the same time, the organic carbon content of different macroalgae was detected, and based on the biomass per unit area, the biomass and carbon sequestration capacity of the subtidal algal field in Gouqi Island were estimated. The results showed that the distribution area of the subtidal zone algal field is about 22.33 hectares in Gouqi Island, and there were 19 species of 3 phyla of macroalgae are distributed. The content of organic carbon in different species ranged from 29.11% to 36.85%. Brown algae contain a special blue light effect and have the highest average organic carbon content (32.62%) which was followed by Chlorophyta (31.82%) and Chlorophyta (29.39%). The macroalgal carbon sequestration capacity per unit area was estimated to be 176.15g·C/m², and the total carbon sequestration in the sea area is about 38.28 tons, equivalent to about 129.07 tons of CO₂ emission reduction. The results of this study can accumulate basic data for the study of carbon sequestration capacity of macroalgae farms in coastal waters, and also provided a scientific basis for the study of negative emission reduction path in the ocean.

Rocky reef habitat is an essential part of marine ecosystems because it boasts complex plant and animal communities, high biomass, stable material cycles and energy flows. However, human activities and frequent weather disasters have caused rocky reef habitat loss and biodiversity loss. Therefore, restoring degraded rocky reef habitats is considered a top-priority action. In this paper, we applies ecological theories such as ecological niche theory, succession theory, edge effect theory and disturbance-stability theory to restore the concrete rock reef ecosystem. As eco-concrete has a complex pore structure, rough surface and high strength, its application can offer an attachment base and habitat for marine organisms. Therefore, eco-concrete can be used to restore oyster reefs, algal reefs, coral reefs and ecological seawalls, to build an ecosystem with engineering values, to purify water, to provide biological habitat, to maintain biodiversity and to resist wave erosion and to achieve sustainable development. We aimed to protect and restore ecology by conducting research on eco-concrete in terms of its design, production, and construction technology. By doing so, the reef ecosystem survey technology, and an eco-concrete reef ecosystem modular restoration technology system were established, which should improve the management of the eco-concrete reef ecosystem.

The fishmen retreated from Yangtze River fishing have been facing many difficulties in adapting society, among them losing power is particularly prominent. Enhancing their rights is a key factor to their social adaptation and an important guarantee for the effective implementation of fishing banning. Based on the analysis of the field surveying findings, in this article, we concluded that the withdrawal of fishermen is mainly reflected in economic loss of power, social environmental loss of power and psychological loss of power. Therefore, the fishermen should be assisted as soon as possible from three perspectives, system empowerment, organizational empowerment and individual empowerment, which should aid to realizing social adaptation and finally the goals of retirement, stability and prosperity.

Jumbo flying squid Dosidicus gigas is a pelagic and economically important squid species widely distributed off Peru. The purposes of this study were to understand the relationship between spatio-temporal fishing grounds of D. gigas and environmental conditions, and to provide a scientific basis for the sustainable utilization and management of D. gigas resources. Based on the fisheries data of D. gigas in the southeast Pacific Ocean off Peru from September to December, 2006 thorough 2015 provided by National Data Center of Distant-water Fisheries of China, in this study, we determined the position of longitudinal and latitudinal gravity center of fishing ground, and quantified the temporal and spatial changes of fishing ground. In addition, the cluster analysis on the fishing ground gravity centers was performed. The relationship between fishing effort and sea surface temperature (SST) was examined based on frequency distribution analysis and the influence of SST on the changes of fishing ground gravity centers was further evaluated. The responses of fishing ground gravity centers to the La Niña and El Niño events were finally explored. Significant monthly and interannual variations were found in the longitudinal and latitudinal gravity centers of the fishing ground. Cluster analysis divided the fishing ground gravity centers into three categories. The fishing effort distribution in the longitude, latitude and SST showed a large difference from month to month. Compared with the El Niño year (2015), the SST on the fishing ground in the La Niña year (2007) was lower, leading to the northwestward shift of the most preferred temperature front for D. gigas. Therefore, the gravity centers of fishing ground in 2007 moved northwestward. The results indicated that spatio-temporal distribution of D. gigas was closely related to large-scale climate variability-induced SST change.

The pore water pressure in seabed sediments is sensitive to hydrodynamic changes, and investigating the response of pore water pressure in sediments under different sea conditions is of great significance to the study of seabed instability and dynamic evolution of seabed boundary layer. In the sea area of Zhoushan Zhujiajian, Zhejiang Province, the dynamic changes of the hydrodynamic conditions and the pore water pressure of seabed sediments at 1m, 3m, 5m and 7m below the sea bed before and after typhoon Lekima were recorded by using the pore water pressure monitoring system. The monitoring data showed that the variation of pore water pressure in seabed sediments was affected by hydrostatic pressure and sediment properties, and had obvious response to wave action in short term. During the typhoon, the hydrodynamic force was greatly enhanced, and the effective wave height could reach more than 5 times of that under the calm sea condition. The oscillation amplitude of the excess pore water pressure in the sediment at the shallow 1m layer could reach 1-2 kPa, and the change of the excess pore pressure value was strong consistently with the wave strength. In the process of wave load acting on seabed sediment, the wave pressure had obvious amplitude attenuation, and the attenuation could reach more than 70% at the shallow layer of 1 meter. The influence of waves could be almost ignored below 1 meter. The influence of rod stop plate was an important reason for the attenuation of pore pressure amplitude. The presence of gas in seabed sediments and the interaction between shallow active silt layer and waves could significantly reduce the influence of wave load on seabed pore water pressure, which was an important factor of wave energy consumption.

In recent years, marine litter pollution has received continuous attention from the public. In order to explore the pollution status and main sources of beach litter in Weihai, this article was based on the survey data of six beach litter sections in Weihai, then grasped the species, abundance and distribution characteristics of beach litter, and analyzed its source and temporal changes. The results showed that in 2020, the average quantity density of beach litter in Weihai was about 151,800 items/km², with the most being plastic litter (73.93%), and the average mass density was about 259.38kg/km², with the largest proportion of beach litter being the plastics (59.68%). The beach litter in Weihai was overall characterized by large quantity and light weight. Approximately 79.38% of the beach litter came from the human activities on land such as recreation and leisure, while 20.62% of beach litter came from production activities such as marine fishery and breeding Current statistics showed that the abundance of beach litter in Weihai was not only lower than the average level of beach litter in Rizhao and Shenzhen, but also lower than the abundance level of beach litter in different parts of the world, such as the Eastern Mediterranean Turkey and Croatia.

Seawalls play an important role in preventing coastal areas from storm surges, but the seabed in front of seawalls usually suffers serious erosion after their construction, which would threaten the safety of seawalls. To analysis the scour problem in Gudong Seawall, we recovered the scouring process according to the water depth during the past 20 years, discussed the scour mechanism and calculated the maximum scouring depth. The results showed that: (1) Gudong seawall was under the erosion background in the abandoned sub-lobes of the underwater delta of the Yellow River Delta, and the seabed within 500 m offshore suffered more severe erosion, which was called background scouring and toe scouring respectively in this manuscript. The background water depth had deepened from 2-3 m in 2000 to the present depth of 6 m, and the maximum water depth at the toe of the seawall had exceeded 7 m. (2) Background scouring was mainly caused by the diversion of the river course and the reduction of sediment into the sea. Waves were the main driving factor for seabed scouring. Seawall toe scouring was caused by complex hydrodynamic processes in front of the Gudong Seawall, such as wave reflections, wave breaking, turbulence, coastal current, offshore current, etc. (3) It was predicted that the maximum scouring depth for background erosion in the Gudong Sea area was 7 m, whilst for toe scouring was 1.7-2.5 m, so the maximum water depth in front of the Gudong seawall was 8.7-9.5 m.

Marine fishing villages are the unit form in overall rural area. Strengthening studies on the ecological environment management should prompt the implementation of rural revitalization strategy. By combing the current practicing effect of the ecological environment management of marine fishing villages, we found that the social capital plays a significant role. Selecting S Village of Shanwei City and K Village of Jiangmen City as the case sites, we compared the degree of social capital participation in environmental governance, the mechanism of action, and the difference in effectiveness through questionnaires and in-depth interviews. The results showed that the environmental governing ability and quality of governors, and the difference in social capital stock of fishing village communities are the main reasons for the obvious differences in governance effectiveness. It is believed that the follow-up of the ecological environment management of marine fishing villages should focus on improving the governance capabilities and political literacy of local governments and fishing village leaders, cultivating and making good use of the social capital of marine fishing villages to encourage the endogenous role of multi-participation, and promoting the modernization of marine fishing village ecological environmental governance.

Three-dimensional wave-current coupling numerical model was established based on the FVCOM (Finite-Volume Community Ocean Model) circulation model and wave model. Numerical simulation on the hydrodynamic environment characteristics of Zhoushan island sea area was performed. The tidal current and wave characteristics of Zhoushan island sea area were mainly investigated. The results showed that the reciprocating current was dominate in the nearshore area and the rotating current was dominant in the offshore area of Zhoushan islands. The ebb tide was stronger than the flood tide in most areas of the Zhoushan islands. The vertical current velocity in the bottom layer was about 59%~70% of that in the surface layer. The significant wave height during the spring tide was higher than that during the neap tide, and the significant wave height gradually decreased from the offshore to nearshore area. The effect of wave on the tidal current velocity was related to the water depth, where the current velocity in the nearshore area at small water depth was mostly affected by waves.

To understand Yangjiang, Guangdong nearshore sea surface water content and potential ecological risk of heavy metals, samples surface waters were collected at 14 stations. The content distribution characteristics of 7 kinds of heavy metals were analyzed in surface waters including Cr, Cu, Zn, Cd, Pb, As, and Hg. The Hakanson method was adopted to evaluate their ecological risk index and potential ecological harm. The results showed that the average concentrations of heavy metals Cr, Cu, Zn, Cd, Pb, As and Hg in the surface waters off Yangjiang were 1.10 μg/L, 5.25 μg/L, 9.91 μg/L, 0.027 μg/L, 0.945 μg/L, 1.06 μg/L and 0.027 μg/L, respectively. Among them, Cr, Zn, Cd, Pb, As and Hg met the quality standards for class I seawater, while Cu met the quality standards for class II seawater. There was a strong correlation among the 7 heavy metals, and each heavy metal also had a certain correlation with different environmental parameters. Based on the analysis of the potential ecological risk index, the average value of RI was calculated to be 6.59, which was a slight ecological hazard and the overall level of cleanliness.

The CTD and ADCP mounted on the submarine dynamic platform were used to conduct long-term and fixed-point observation of the deep waters in the northern South China Sea. Based on data such as thermohaline and ocean currents, we analyzed the marine environment characteristics by various data processing methods. According to the data analyzed, the temperature and salinity of the deep waters in the northern South China Sea were relatively stable with some seasonal differences, and the main characteristics were low temperature, high salt and high density. The current velocity ranged from -100 mm/s to 100 mm/s, and mainly about 50mm/s. The current velocity was inversely proportional to water depth, forming a typical deep ocean velocity profile. Tidal current harmonic analysis demonstrated that tidal currents are dominated by diurnal and semidiurnal tides, and the flow ellipse rotated with depth and changed in a complex way. Different vertical modes were calculated based on the Empirical Orthogonal Function (EOF) analysis of the eastern and northern components of the tidal currents, with a variance contribution for the first two modes of at least 85%, higher order modes were less than 5%. The results revealed a strong barotropic character for the tidal currents of this region.

In the world, many coastal underground brine resources are distributed in the muddy tidal flat area, but the research on the subterranean estuary in this area is only in the primary stage, and the model has not been established. In this paper, the southern bank of Laizhou bay was selected as a typical study area. Electrical resistivity tomography monitoring, pore water conductivity monitoring, seawater and groundwater conductivity measurement were carried out in the areas with different vertical permeability coefficients of surface sediments. The sediment-physical relationship of muddy tidal flat was clarified. A standard for the division of seawater-groundwater mixed zones was established. This standard combined with the electrical resistivity tomography monitoring results at each tidal time to analyze the complex exchange mode of seawater-groundwater and its influencing factors, and to reveal the temporal and spatial distribution of the mixing zone. The research results showed that the biological channels clustered in the silt layer were the main ways of seawater-groundwater exchange during the tidal cycles. The formation mechanism of "upper saline plume" and "groundwater discharge tunnel" in the muddy tidal flat subterranean estuary and the seawater-groundwater exchange process were different from those of sandy tidal flats. Decreasing the permeability of tidal flat sediments would cause the direct exchange rate of seawater-groundwater through sediments to decrease, leading the main exchange path to shift to high-permeability channels. The flow rate of intrusion and excretion in the channels would increase.

Under the action of external factors, the deep gas in seafloor sediments moves upward, which is easy to accumulate at the interface of shallow coarse-fine sediments and form gasbags. When the gas in the gasbag escapes, it will induce a variety of submarine geological disasters and bring harm to human engineering construction. Therefore, real-time monitoring of the formation-growth-dissipation process of gasbags is of great significance for effectively judging its development law and predicting the occurrence of follow-up potential disasters. In this study, the multi-point pore water pressure monitoring technique was used to simulate and monitor the forming and dissipation of gasbags in saturated fine-grained sediments by mathematical simulation and physical simulation experiments. The variation characteristics and mechanism of typical excess pore water pressure of fracture formation, gasbag formation and gas release were discussed in detail. According to the results of mathematical simulation and physical simulation experiments, combined with theoretical analysis, the formation-growth-dissipation process of gasbag was divided into three stages: transverse crack generation, gasbag longitudinal expansion and oblique or vertical crack generation, and its corresponding excess pore water pressure was concave. The formation of gasbag began with the transverse cracks at the interface of coarse and fine sediments, and excess pore water pressure attenuated rapidly. The gasbag showed the expansion of longitudinal cavity, and excess pore water pressure remained almost unchanged; oblique or vertical cracks appeared at the end of the evolution of gasbag, and excess pore water pressure accumulated and dissipated again. The variation curve of excess pore water pressure in gas release stage had obvious saw-tooth fluctuation characteristics, and it could be used to distinguish whether the gas was released intermittently or continuously. The accumulated extreme value of excess pore water pressure could be reduced during gas reinjection, which meant that a lower pressure could create cracks and reopen the gas channel, destroying the sediment and causing the gas to escape.

Water transparency is an important ecological indicator for evaluating the underwater light field, which determines the biological, physical and chemical processes in waters. Based on the field measurements from case I and case II waters, the effect of Secchi disk depth on remote sensing reflectance of water was performed to develop a Secchi disk depth estimation algorithm for coastal waters of the South China Sea. The optical model, validated by using local data in October 2015, was used with monthly VIIRS data from 2013 to 2016 to assess the temporal and spatial variability of the Secchi disk depth in coastal waters of the South China Sea. Furthermore, a comparison of VIIRS and MODIS for monitoring marine environment was performed in this study. Results demonstrated that the Secchi disk depth highly controlled the remote sensing reflectance of water at bands of 488 and 555 nm. A reflected peak was found at 555 nm when the Secchi disk depth higher than 5.3 m, while on the condition of the Secchi disk depth lower than 5.3 m, the peak moved to the waveband of 488 nm. The band ratio of VIIRS, R_rs (488)/R_rs (555), was highly correlated to the Secchi disk depth in coastal waters of the South China Sea, which was then applied to the calibrated VIIRS images and found that the Secchi disk depth was higher in the offshore than nearshore and also in the east than west. Compared to MODIS data, the VIIRS instrument has higher spatial resolution and calibration activities, which will provide more ocean color products in future.

Based on a total of 49a sea surface temperature (SST) data of SODA and net sea surface heat flux data of ECMWF from January 1960 to December 2008, the climatic evolution characteristics of the coupled main mode of the two anomalies were studied in the tropical Indian Ocean by using moving SVD method. The main results were as follows: (1) The coupling effect was gradually strengthened in the evolution process, the correlations between the two fields maintain well. (2) The sea surface net heat flux anomaly can better explain the basin variations of the SSTA field itself in most periods with the largest variations locating in the coastal area of Sumatra-Java and the sea area south of 20°S. And under its influence, the sea basin showed a warming trend in most periods. (3) The spatial distribution of the two fields of the coupled main mode changed significantly once from 1961~1970 to 1962~1971, under the significant influence of the year 1971. (4) The SSTA field changed significantly in the northeast Indian Ocean and the South China Sea with obvious positive change areas, while the sea area south of 20°S showed obvious negative changes. The net sea surface heat flux anomaly filed showed significant positive and negative changed in the South China Sea, the equatorial eastern Indian Ocean and somewhere east of Madagascar, respectively.

The temporal and spatial distribution characteristics, physical parameters, and fallout forecasts of strong convection under different weather typologies in Shandong peninsula from 2015 to 2020 were analyzed and studied. The results showed that: strong convective weather mainly occurred under five weather situations, namely, low trough, high-altitude cold vortex, northwesterly flow, edge of the sub-tropical height and transverse trough; strong convective weather events mainly concentrated in June-August, and were most likely to occur in the afternoon to the nighttime, and were mostly unevenly distributed; the spatial distribution mainly exhibited four characteristics, namely, western-type, eastern-type, area-wide-type, and local-type, with local-type events being the most frequent. The physical parameter characteristics differed greatly among different weather situation configurations, and the physical parameter characteristics varied greatly among different weather situations. The physical parameters of different weather configurations varied greatly, with the CAPE value and K index of the sub-tropical height edge type being larger than those of other situations, the vertical wind shear SHR6 and the total index TT of the high-altitude cold vortex type being the largest, the CAPE value and K index of the northwesterly flow type being small, and the SI value being positive. Strong convection caused by weak cold fronts and sea-breeze fronts was most likely to occur in the western part of Yantai, and then moved eastward to become weaker, and the eastern type was more likely to happen at night. The eastern type mostly occurred at night, mostly due to the influence of the surface convergence line, and the different positions of the inversion trough also determined the different fallout areas of the strong convection. The region-wide type mainly occurred under the influence of the upper-air cold vortex or the strong trough cold front; the local type corresponded to the edge of the subduction plateau and the northwesterly airflow type, with the surface convergence line as the main triggering system, which had a very good correlation with the sea-land topography and the mountainous topography.

The coastal zone is a fragile area affected by the global ecological environment and is extremely sensitive to global changes. Due to the change of climate environment and the excessive exploitation of groundwater, coastal geological hazards such as coastal erosion and seawater intrusion in Jiaodong peninsula have gradually become a serious threat to the sustainable economic development and people’s property security in this region. In this paper, based on the relevant data of coastal geological hazards in the coastal zone of Jiaodong peninsula, the qualitative analysis was carried out to determine that the main coastal geological hazards in this region were seawater intrusion and coastal erosion. On this basis, the risk assessment index system was established by selecting representative indicators. The quantitative risk assessment and GIS-based zoning of seawater intrusion and coastal erosion in Jiaodong peninsula were then carried out. The results showed that the comprehensive risk level of seawater intrusion in Jiaodong peninsula was ranked from high to low as Qingdao, Weihai, south Yantai and north Yantai. The comprehensive risk level of coastal erosion was ranked from high to low as Qingdao, north Yantai, Weihai and south Yantai. Accordingly, this paper proposed to rationally exploit groundwater in Weihai city and Yantai city, to protect coastal sand mines and vegetation in north Yantai and to move sand making beaches, to strengthen coastal defense projects in Qingdao and to pay attention to the pre-disaster investment.

Based on the digital elevation model and the spatial analysis techniques, in this paper, we studied the watershed landforms in the area of Chaiwen River in Yiyuan, Shandong Province, and divided the developing stages of the watershed landforms. Egou and Dazhangzhuang River are the head of Chaiwen River and Yihe River, respectively. Their water system fractal dimension, hypsometric index and geomorphic information entropy were calculated, and the geomorphologic development stages were divided. It is believed that the result of hypsometric index and geomorphic information entropy is more correct. The Egou River basin is now at the mature stage of geomorphologic development, and the Dazhangzhuang River basin is now at the old stage. River capture event enhanced the erosion ability of Egou and weakened the erosion ability of Dazhangzhuang River.

The immune system of Ruditapes philippinarum is non-specific, and the haemocytes play an important role in its immune defense. In this study, the morphology and structure of Escherichia coli, Staphylococcus aureus and Vibrio anguillarum were observed under scanning electron microscopy and transmission electron microscopy, and then the phagocytosis of haemocytes on these bacteria was compared and observed under light microscopy and transmission electron microscopy (TEM). The results showed that E. coli was rod-shaped, with an average size of 1.6×0.6 μm; S. aureus was spherical in shape, with an average size of 1.3×1.1 μm, and arranged in a grape string; V. anguillarum was arc-shaped, with a single slender polar flagellum, the average size was 1.3×0.7 μm, and the average flagellum length was 4.5 μm. The phagocytosis rate of E. coli, S. aureus and V. anguillarum was 38.7%, 30.0% and 24.4%, respectively. TEM observation found that the haemocytes can adhere and wrap the bacteria through filopodia, lamellipodia, or directly with the plasma membrane, and the phagocytized bacteria can be digested by lysosomes. It was also found that the ultrastructure of the haemocytes did not damage after phagocytosis of E. coli and S. aureus while after phagocytosis of V. anguillarum, the haemocytes ultrastructures were obviously damaged, and the apoptosis or death of the haemocytes occurred. We concluded that the difference of phagocytosis of R. philippinarum haemocytes to three kinds of bacteria was related to the size, aggregation degree and pathogenicity of the bacteria.

In this study, an ecological risk index system based on the pressure-state-response (PSR) model was developed to evaluate the marine ecological risk of Beibu Gulf sea area, Guangxi. Fifteen representative indicators were picked up for the ecological risk index system. Analytic hierarchy process (AHP) was used to obtain weights of the selected indicators. Marine risk index was calculated using synthetic index method. The result showed that the marine risk of Beibu Gulf sea area was at the level of early warning. Optimistically, the marine risk presented a declining tendency in recent 10 years. Some marine risk management countermeasures were put forward for marine sustainable development, which included science-based and strictly controlled land reclamation, controlling land-based pollution, controlling alien species invasion, controlling the population of coastal cities, reinforcement of coastline renovation and restoration among others.

The industries in the Bohai rim region are intensive, and heavy industries in coastal provinces and cities are gathering. Land-based pollution has become one of the important factors for the marine environmental pollution in the Bohai Sea. In the aspect of the restoration of marine environmental pollution in the Bohai Sea, the cooperation of the local governments of the Bohai Sea is crucial for the control of land-based pollution in the Bohai Sea. At present, the local governments in the Bohai rim have mainly problems such as inter-governmental coordinated governance motives and regional development differences, local government governance models and marine pollution attributes incompatibility, inter-governmental coordination concepts and local interests. In response to the above problems, the author proposes to cultivate the synergy awareness of the local governments of the Bohai rim, to improve the collaborative governance system, and to improve the coordinated governance mechanism from the perspective of inter-provincial synergy and synergy mechanism with a view to achieving inter-governmental coordinated governance of land-based pollution in the Bohai rim.

Methods such as spatial interpolation, principal component analysis, and the Nemero pollution index were used to analyze and evaluate the water pollution of Bosten lake. According to the result, the total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH₃-N), potassium permanganate index (COD_Mn), suspended solids (SS) and turbidity of Bosten lake water quality indicators indicated an obvious spatial difference, with the concentration of the southwest shore and the northeast shore of the lake being higher than that of central lake. the dissolved oxygen (DO) showed decreasing from east to west, and the pH value increasing from the southwest shore of the lake to the center and the middle zone of the north shore. There was a strong correlation between the water quality indicators. The DO and TN, TP, NH₃-N, COD_Mn and turbidity were significantly negatively correlated while TP and TN, NH₃-H, COD_Mn, turbidity, NH₃-N and COD_Mn and turbidity. COD_Mn and turbidity were significantly positively correlated. Organic matters such as DO, TN, TP, NH₃-N polluted the waterfront in the lake area heavily, with the pollution level of the south shore being the highest, then the north shore, the west shore, lake centre, followed by the east shore. The results of the pollution assessment showed that the east shore, centre and west bank of Bosten lake were lightly polluted with class III water quality, and the north shore and the south shore of the lake were medium pollution with class IV water quality. The spatial variation characteristics of water quality could reflect the main pollution factors and the pollution level of lake water quality, thus providing a reference for the protection and treatment of water resources in inland lakes in arid areas.

To explore the similarities and differences of the wave attenuation performance between double flat plate-type (DFPT) and double arc plate-type (DAPT) open breakwaters, a numerical model of the interactions between wave and plate type open breakwater based on the Navier-Stokes (N-S) equations with the help of Fluent, and their correctness was validated by experimental results. The results showed that when D=-0.04 and 0 m, the transmitted wave energy of the DAPT open breakwater was smaller than that of the DFPT open breakwater, and the maximum percentage reduction was 71% for the 90% cases. When D=0.04 m, the transmitted wave energy of the DAPT open breakwater was larger than that of the DFPT open breakwater, and the maximum increase was 82%. Under the various submergence conditions, reflected wave energy of the DAPT open breakwater was smaller than that of the DFPT open breakwater. Under the different submergence condition, the dissipated wave energy of the DAPT open breakwater was larger than that of the DFPT open breakwater, and the dissipated wave energy of the two open breakwaters increased as W/L increased. By comprehensively considering the transmitted, reflected and dissipated wave energy for the two types of open breakwaters, when placed at or above the still water surface, the DAPT open breakwater was found to exhibit higher wave dissipation performance than the DFPT open breakwater. In engineering practice, DAPT open breakwaters submerged at suitable depths could be selected based on the specific water conditions.