Wave breaking over a submerged breakwater is simulated based on Lattice Boltzmann Method. By establishing a numerical wave flume and using a push plate to make waves, the interaction between waves and submerged breakwater is simulated. The calculated results are in good agreement with the experimental data, and verify that the model can well simulate the breaking and propagation of waves. It is proved that the wave height shows an attenuation trend due to the obstruction of the submerged breakwater and the breaking of the waves. Under the same wave height condition, with the increasing of wave period, the reflection coefficient increases first and then decreases while it only increases at the low water level.

We studied the ecological characteristics of macrobenthic community in the coastal area of Rongcheng and its ecological health status based on the investigation data collected in four seasons, 2016. A total of 163 macrobenthic species were identified. The dominant species throughout the four seasons were Lumbrineris cruzensis, Tharyx multifilis and Heteromastus filiformis. The average biomass of the macrobenthos was 58.89 g·m^-2 and the average abundance estimated from the four cruises was 301.83 ind·m^-2. The Shannon index (H′) of the macrobenthos community varied between 2.50 and 2.58, the species evenness index (J) varied between 0.80 and 0.87 while the species richness index (d) ranged from 1.20 to 1.89. The Bray-Curtis similarity cluster analysis showed that there is a distinct distribution of macrobenthic community from seashore to offshore, which is closely correlated with the spatial structure of bathymetry in the studying region. The benthic biological indices (AMBI and M-AMBI) indicated that the benthic ecosystem in the coastal area of Rongcheng tends to be moderately disturbed. Our findings revealed the community structure of macrobenthos in the coastal area of Rongcheng, which should provide a reference basis for ecological environment protection.

The South Yellow Sea and its adjacent sea area are selected as the research region, and the statistical characteristics of typhoons passing through this region from 1970 to 2016 are analyzed. The results showed that the frequency of typhoons in the South Yellow Sea region is high, and they are most likely to happen in July and August. Their paths are diverse, but most of them follow two paths: either landing and turning, or moving to the north at offshore. Based on the above two paths, this study uses several typhoon pressure field models and typhoon wind field models to construct and compare the wind fields of three typical typhoons, and to make error analysis with observation data. The result shows that the combined model of Fujita-Takahashi nested pressure distribution model and Jelesnianski wind field model could get a more reasonable simulation of MUIFA (201109) and Kompasu (201007). Myers pressure distribution model and Miyazaki wind field model have the best result on the simulation of Chan-hom (201509).

Large-scale reclamation had been carried out along the coast of the Bohai Sea, in order to alleviate the contradiction between the land supply and demand, until the full stop of approval of new reclamation projects in 2018. Long-term reclamation activities have led to significant changes in the coastline of the bays. In order to reveal the main causes of coastline changes in Laizhou Bay and the response of tidal wave system in Bohai Sea to coastline changes, the coastline data of Laizhou Bay in two typical years of 2000 and 2020 were selected to study the morphological changes in the Laizhou Bay during the 20 years, covering the changes of the coastline length, of the area and of the centroid of the bay. On the basis of the coastline and water depth data, a two-dimensional tidal wave mathematical model was established to study the impact of the coastline changes of the Laizhou Bay on tidal wave system, tidal types and maximum possible tidal range of the Bohai Sea in 20 years. The results showed that the bay area had decreased by 8.02% and the coastline length had increased by 77.65% in the Laizhou Bay during the 20 years from 2000 to 2020. The change of the southwestern coastline of the bay was the most dramatic, resulting in a 2.21 km shift of the centroid to the northeast. Coastline changes of the Laizhou Bay had led to the displacement of amphidromic points and the variation of amplitude for each constituent tide of the Bohai Sea. M₂ constituent tide amphidromic point near the Yellow River estuary moved northwestward by 1.4 km, M₂ constituent tide amphidromic point near Qinhuangdao moved northeastward by 1.7 km, and K₁ constituent tide amphidromic point in the southern part of the Bohai Strait moved eastward by 2.1 km. For the Bohai Sea, M₂ constituent tide amplitude showed a tendency of increasing as a whole, and the variation of K₁ constituent tide amplitude mainly occurred in the east of Bohai Strait. Irregular semi-diurnal tides are the main tides in the Bohai Sea. Affected by the coastline changes of the Laizhou Bay, the sea areas occupied by irregular diurnal tides and regular diurnal tides were reduced near the Yellow River estuary and Qinhuangdao, and the maximum possible tidal range in the Bohai Sea would increase.

This article focused on reviewing the main research achievements of domestic and foreign scholars on the path, influence mechanism, seasonal and interannual variability of the Kuroshio intrusion into the South China Sea, as well as its impact on the South China Sea circulation, water mass properties and mesoscale eddies in the past two decades. The path of Kuroshio's intrusion from the Luzon Strait into the South China Sea could be divided into three forms, and the transportation in the Luzon Strait presented a “sandwich structure”. Kuroshio intrusion was influenced by monsoon, sea pressure gradient, mesoscale vortex, β effect, sea pressure gradient, ENSO, PDO, typhoon and other factors. Due to the influence of the Kuroshio's own intensity and the East Asian monsoon, the intensity of the Kuroshio's intrusion into the South China Sea was greater in winter than in summer. Interannual variability depended on El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). ENSO and PDO controlled the kuroshio's intrusion intensity by affecting the location of North Equatorial Current bifurcation. Kuroshio water, as part of Indonesian throughflow, brought high-temperature salty water to the South China Sea, or shed anti-cyclonic eddies to affect the South China Sea mesoscale eddy structure.

When oil spill accident occurs, the spilled oil will spread under the current and wind, which will cause serious threat to the sensitive area of the sea. In order to study the diffusion trajectory of spilled oil, the prediction model of oil spill accident is established by using the Hydrodynamic Module (HD) and Particle Tracking Module (PT) of Mike21FM (DHI). Based on assumed oil spill accident of the project in the Lvhua island, the sweep area of oil film and the fate of oil particles are simulated under different wind conditions. The simulation results show that: (1) When the accident happened in the flood tide, it has great influence on the environment of the island and its surrounding area; (2) The wind has little influence on the oil particles in the early stage of oil spill, and after the oil particles are diffused, the influence become greater; (3) When the effect of the wind and the tide are superimposed, the oil film diffusion is intensified, and the sweep area is enlarged.

The eastern part of the Barents Sea is rich in oil and gas but covered by sea ice. With climate change, the sea ice continues to melt, making the eastern region maintain open water for longer, and wave characteristics will also change accordingly. It is necessary to carry out corresponding research for the design, construction and operation of marine engineering structures serving in this sea area. In this paper, the sea ice concentration data from the National Snow and Ice Data Center (NSIDC) were collected to drew the sea ice edge lines and analyzed the changes of sea ice extent. According to ice edge lines, one representative point was selected in the eastern sea ice melting zone. The wave data from the ERA5 dataset of the European Center for Medium-Range Weather Forecasts (ECMWF) were collected to study the basic wave characteristics and wave design parameters. The annual and seasonal extreme values of wave height were extract to estimate the return values of significant wave height by the GEV, Gumbel, Weibull and Maximum entropy distribution models, respectively. The results showed that with the reduction of sea ice, the frequency without wave at representative point had decreased significantly, and wave existence was throughout the year in recent years. According to the results of the return values, summer was the most suitable operating season.

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.

To investigate the effects of different diets on Scylla paramamosain after feeding for 56 days, multiple indexes including body weight, specific growth rate (SGR) and hepatopancreas index (HSI) were compared among four different diets (HM-Hypophthalmichthys molitrix, CF-crab compound feed, EF-eel feed, SC-Sinonovacula constricta). In addition, biochemical composition, serum biochemical indexes, hepatopancreas biochemical indexes and digestive enzyme activities (Protease, LPS, AMS) were calculated. The results showed that SGR of SC was significantly higher than that of other diets (P<0.05). In terms of serum biochemical, TP content of EF diet was significantly lower than that of other diets (P<0.05). In terms of hepatopancreas biochemical indexes, there was no significant difference in TP content among four diets (P>0.05), ALB content of EF diet was significantly lower than that of other diets (P<0.05). TG content of CF diet was the highest among all diets. Among the biochemical enzyme activity indexes, SOD activity in HM diet was significantly lower than that in other diets (P<0.05) while Na⁺K⁺-ATPase activity in EF diet was the lowest among all diets. In terms of digestive enzymes, there was no significant difference in protease and AMS in four diets (P>0.05) while LPS in HM diet was significantly higher than that in other diets (P<0.05). In terms of the correlation analysis, the specific growth rate of HM diet was positively correlated with protease activity (P<0.05). To sum up, Sinonovacula constricta was the best diet with the best comprehensive index under the condition of "crab apartment", which has great advantages in SGR and biochemical enzyme activity indexes. But crab compound feed has certain advantages in hepatopancreas TG content and hepatopancreas biochemical indexes.

A hydrodynamic numerical model of the Zhanjiang Bay area is established using the Delft3D model and the calculated value that was verified with the measured hydrological data. On the basis of the hydrodynamic model, a numerical model of oil spill diffusion in Zhanjiang Bay is established by considering the processes of oil spill drift, diffusion, evaporation, emulsification and adsorption. The oil spill drift and diffusion numerical model simulates the oil spill accidents under different tides (flood, ebb) and different wind conditions (no wind, summer constant wind, winter constant wind and two unfavorable wind conditions) and predicts the main drift path, sea sweep area and the time of oil film to reach environmental sensitive area within 24 h of oil spill. The analysis results show that the oil film drift and diffusion are mainly related to the current field and wind conditions, and the long-term diffusion direction of the oil film is consistent with the wind direction. Within 24 hours of the oil spill, only unfavorable wind conditions would affect the mangrove protection area and fishery aquaculture area in Nansan island. Marine reserve in Techeng island is the most vulnerable to pollution. Under the condition of calm wind, the affected area of oil spill is the widest. Under the condition of flood tide and calm wind, the area of oil film sweeping the sea after 24 hours is the largest, and the affected area of oil spill reaches 57.89 km². The oil film is most easily adsorbed on the top shoreline of Zhanjiang Bay.

According to survey and analysis of the sediment environment in Xiaohai lagoon of Wanning, the extent of surface heavy metals is used to assess the geoaccumulation index, enrichment factor and potential ecological risk index. The results showed that the average values of Zn, Cd, Pb, Cu , As, Hg in the surface sediment are 36.1 mg/kg, 0.09 mg/kg, 24.7 mg/kg, 4.0 mg/kg, 7.62 mg/kg and 0.100 mg/kg. The TOC is 0.42% and acid volatile sulfide (AVS) is 226.75 mg/kg. The sediment of Xiaohai lagoon area belongs to the first category of marine sediment quality standards. Zn, Cd, Pb, Cu, As and Hg showed a decreasing trend from 2005 to 2011, the average values of Zn, Cd, Pb and Cu were the lowest in 2011. The carbon cycle of Xiaohai lagoon was balanced, which was related to the comprehensive treatment. The ecological environment was improved and less affected by human beings of mariculture. The trend of TOC change rose from 1988 to 2004, reaching its peak of 1.20%, which was related to the vigorous development of mariculture. The trend of TOC was downward after 2004 and approached the value before 1988 in 2011. The correlation analysis shows that AVS, TOC, Cu, As and Hg had the same or similar pollution sources, which are related to mariculture and industrial waste water input. The averaged pollution degree of the geoaccumulation index and enrichment factor of heavy metals was decreased in the following order: Hg＞Cd＞Pb＞As＞Zn＞Cu. The mean potential ecology risk index (RI) value of heavy metal in Xiaohai was 219.76, which belongs to moderately potential ecology risk. The potential ecology risk index of 6 heavy metals was in the following order: Hg＞Cd＞As＞Pb＞Cu＞Zn. Hg and Cd were major potential ecology risk factors. The pattern of RI change was 2008<2011< 2005. Therefore, more attention should be paid to Hg and Cd pollution in order to prevent further deterioration of ecological marine environment of Xiaohai.

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.

Landsat imagesare used to extract the coastline of Yancheng from 1997 to 2017, and the baseline method is used to quantitatively analyze the changes of the coastline. The results show that during the 20 years from 1997 to 2017, the length of the Yancheng coastline has not changed much, but the proportion of artificial shorelines has increased gradually. The eroded coastline is located between Guanhe estuary and Sheyang estuary, with the abandoned Yellow River estuary as the center. The average changes of the coastline is -0.46 m/a. The silt coastline is distributed between the Sheyang and Beiling estuaries,with an average change rate of 140.6 m/a over 20 years, and with a change rate of 305.16 m/a, 160.79 m/a, 121.02 m/a, and 102.86 m/a every 5 years. Coastal silting is slowing down, and the extent of coastline advancement to the sea is decreasing year by year. The north-south erosion and inflection point extend southward to the vicinity of the Sheyang salt field. Agricultural reclamation, breeding reclamation, port and coastal protection engineering construction are the main reasons for the changes of the coastline of Yancheng.

The mid-latitude northwest Pacific Ocean is the high incidence area of sea fog, and it is also the way for China to reach the Arctic sea. However, due to the few observations at sea, the understanding of the formation mechanism of sea fog is limited. From September 12 to 14, 2019, the research ship "Xiangyanghong 1" recorded a sea fog event in the Oyashio extension area. In this paper, the formation mechanism of the sea fog was studied mainly by numerical simulation, numerical experiment and observations from scientific research ships. The results showed that: (1) The sea fog occurred in the warm area of the extratropical cyclone, and the warm front of the synoptic scale advanced to the north, forming a large range of front inversion over the cold water of the Oyashio extension providing favorable weather background conditions for the development of the clouds/fog. (2) The atmospheric boundary layer above the cold water side of the ocean front (sea surface temperature front) was a "double inversion" structure. The superposition of subsiding inversions and frontal inversions caused by the subsiding branch of the local low-level secondary circulation forced by ocean front was an important reason for the formation of the "double inversion". The numerical results showed that with the smoothed ocean front, the strength of the sinking branch of the secondary circulation in the boundary layer was weakened, the scope of the "double inversion" structure disappeared, and the scope of the fog area was significantly reduced. (3) Both temperature and humidity in the fog rose, but the actual water vapor pressure rose faster than saturated water vapor pressure, the humidification effect was greater than the warming effect, which was obviously different from the cooling and humidification dominance of sea fog in spring and in summer in the Yellow Sea. This study revealed one of the reasons why sea fog tends to occur on the cold side of the ocean front in the open ocean, which can provide a new theoretical support for sea fog forecast.

Based on the monthly tide level data and the hydrological synchronous survey data in spring and neap tides in Haitan strait in spring, summer, autumn and winter, characteristics of the tide and tidal current in sea area near Haitan strait were analyzed, and the influencing factors of residual current variation characteristics in Haitan strait were discussed. The results showed that the tide in the sea area near Haitan strait belonged to the regular semi-diurnal tide, and the ebb tide duration was generally slightly longer than the flood tide duration. The tidal current belonged to the regular semi-diurnal tidal current, the shallow water sub tidal current was relatively significant, and the main direction of the ebb and flow tidal current was obvious, which was a reciprocating current. The tidal waves in Haitan strait were standing waves. The seasonal variation of residual current was significantly affected by the coastal current of Fujian and Zhejiang in the East China Sea and monsoon, the residual current was generally southward in winter and northward in summer.

As necessary support for coastal engineering, non-submerged pile foundation greatly affects the coastal hydrodynamics and ecological environment. Taking Hangzhou bay as an example, we analyzed the influence of non-submerged pile foundation on the tidal dynamics and suspended sediment characteristics using a three-dimensional hydro-sediment numerical model. The results showed that before and after the construction of pile foundation, the distribution of the suspended sediment concentration (SSC) correlated with the currents. Owing to the blocking effect of pile foundations, there was an obvious cylindrical disturbed flow around the piles. The bridge blocked water and formed a low-flow negative pressure zone at the back side, and increased the order of vorticity near the pile foundation; the flow velocity and SSC increased between the pile foundations. The bridge affected the tidal phase and thus the tidal level and tidal asymmetry. The peak and ebb current direction was basically perpendicular to the axis of the bridge. Variations in the near bottom velocity changed the bottom stress, which affected the sediment resuspension and thus changed the SSC. The construction of the bridge accelerated/slowed down the southward sediment flux on the sea/land side. Turbine piles in the open ocean had similar effects with smaller magnitudes.

Water depth is an important topographical element in shallow seas. It is an important part of ocean mapping. Using remote sensing to retrieve water depth, underwater terrain can be obtained quickly and efficiently. Using WorldView-Ⅱ multi-spectral remote sensing image and laser measured data, BP neural network model, random forest model and extreme learning machine model are used to conduct water depth retrieval in Ganquan island of Sansha city, Hainan Province, and the accuracy is compared and evaluated. The results show that among the BP neural network model, the random forest model and the extreme learning machine model, the random forest model has the highest water depth retrieval accuracy. The root mean square error of the verification point is 0.85m, the average absolute error is 0.60m, and the average relative error is 3.54%. The coefficient of determination R² reaches 0.97; within the range of 0-10 meters and 15-20 meters water depth, the retrieval of the extreme learning machine model is the best; in the range of 10-15 meters water depth, the random forest model has the best retrieval effect.

Exchangeable phosphorus in natural sediments plays an important role in regulating phosphorus concentration in water columns, and it is one of the focuses considered in the prediction and regulation of water eutrophication. The intercept method is usually used to calculate the concentration of exchangeable phosphorus in sediment which is positively correlated with the solid concentration (C_s). However, this result is contrary to that obtained by the extraction method. This study discusses the potential causes of the contradiction through theoretical and experimental analyses. The results show that the phosphorus from the intercept method is not the total amount of native absorbed phosphorus (NAP), but the amount of phosphorus (Q₀) involved in the exchange process under actual experimental conditions. For the same set of experimental data, the selection of the abscissa for the adsorption isotherm affects the correlation between Q₀ and C_s: negative when C₀ is used, but positive when C_e is used. In addition, if C_e is taken as the abscissa, the physical meaning of the calculated Q₀ is unclear.Therefore, in order to avoid the positive correlation between C_s and Q₀, we suggest that the initial phosphorus concentration (C₀) should be used as the abscissa when obtaining Q₀ by the intercept method.

Typhoon disaster is one of the most important factors that should be considered in the construction of marine structures. In present study, 31 typhoons affecting the coastal areas of Gudong oil production plant in Dongying City during 1960 and 2019 were simulated and the tide levels near the project site were calculated. The generalized extreme value (GEV) distribution model was applied to fit the marginal distributions of both extreme tide level and storm surge duration. The dependence structure of these two environmental conditions was described by a Gumbel-Hougarrd copula function. Considering the effect of the typhoon frequency on the design values, the Poisson compound extreme value distribution was used to perform the statistical analysis. The results indicate that the joint return period estimated by the proposed model acts as a reasonable representation of the storm surge disaster grade, and thus provides essential information for coastal disaster prevention and mitigation and marine structure design.

The finger piers of Dongjiakou protrude out of the open ocean and are vulnerable to extreme sea state without the protection of breakwater. In this study, the abnormal changes and mechanism of hydrodynamic environment caused by typhoon Lekima captured by ADCP and bathythermograph at the front of Dongjiakou finger pier were analyzed, which could provide important reference for the prediction of berthing environment. It was found that the residual water level showed a "V" symmetric distribution with the maximum water reduction as the symmetry center, and its variation was dominated by wind. When the typhoon was close to Dongjiakou, the lag response time for storm surge was short. When the typhoon center was far away, it was the opposite. The observed residual current was generally less than 20 cm/s during typhoon Lekima, the coastal current had little threat to the port. The forehead swell reached the pier 12 h ahead of the extreme wind speed, and the wave spectrum peak period of forehead swell was in the rolling resonance region of 300 000 ton crude oil carrier and 400 000 ton ore carrier berthed at the jetty which needed to be prevented in advance. Due to the mixing effect of typhoon waves, the bottom water temperature of the observation point rose about 1℃, and the thermocline was destroyed. Even after the typhoon, the bottom water temperature dropped slowly, with a cooling trend of 0.15 ℃/day.

Based on coral reef survey in Wenchang waters with line transect method and historical data collected in 2012 and 2018, and using the semi-quantitative coral reef health index (hereafter as CI), the health status of coral reef ecosystem in Wenchang waters, the change trend and its main influencing factors were analyzed. A total of 79 species of hermatypic corals belonging to 11 families and 31 genera were identified, of them the dominants were the environmentally-tolerant massive ones, i.e., Porites lutea, Favia speciosa, Favites abdita, and Platygyra daedalea. However, Acroporidae, the environmental stress sensitive, were less observed, which had a low coverage. Despite the excellent water quality conditions of Wenchang waters, macroalgae were abundant with mean coverage up to 16%. The community structure of hermatypic corals have obviously changed. The CI value estimated ranged from -0.44 to 0.95, suggesting that the whole coral reef ecosystem was poor in Wenchang waters. Coastal engineering construction and aquaculture sewage discharge were perhaps the two driving factors leading to coral reef degradation in the region. However, compared with 2018, the health status of coral reefs in the region recovered significantly as were revealed by increased CI values from -0.59 in 2018 to -0.06 in 2020. Moreover, in this survey, the mean coverage of hermatypic corals was 12.73% and coral recruitment was 0.9 ind./m², displaying a slight increase compared with historical data. More importantly, little short-term dead corals and coral diseases were found in this survey. These signals indicated that the coral reef ecosystem in this area has a good potential for recovery. It was suggested that the ecological control should be strengthened, and coral reef restoration should be carried out to accelerate its natural recovery.

Using mature sporophyte of Laminaria digitata as material, the zoospores are released and attached to form embryo spores, and then cultured under different environmental factors. To explore the optimal environmental conditions for gametophyte formation, ovulation and young sporophyte formation of L. digitata, the process and characteristics from embryo spore to seedling formation were observed. The results showed: nitrogen concentration of 4 mg/L, phosphorus concentration of 0.4 mg/L, temperature of 15℃, light intensity of 20 μmol Photons/(m²·s) was the optimal conditions for gametophyte formation; Nitrogen: phosphorus concentration of 4 mg/L: 0.4 mg/L, temperature of 10 ℃, light intensity of 40 μmol Photons/(m²·s) were the optimal condition for L. digitata gametophyte ovulation; Under the nitrogen concentration of 4 mg/L, phosphorus concentration of 0.4 mg/L, temperature of 10-15 ℃, light intensity of 40 μmol Photons/(m²·s), the formation of L. digitata young sporophyte was most favorable. This study indicates that the optimal environmental conditions at different growth and development stages of L. digitata are different. The data obtained in this study can provide theoretical basis and data support for artificial seed breeding and breeding of L. digitata.

To study the effects of immobilized culturing method on the growth of marine microalgae, their pigment contents and their chlorophyll fluorescence parameters, we conducted this work by using Chlorella sp. as the material, sodium alginate (SA) as the carrier and calcium chloride (CaCl₂) as the linker. The effects of immobilized and liquid suspension culturing methods on the cell density, photosynthetic pigment contents, chlorophyll fluorescence parameters of Chlorella sp. were determined. The results showed that (1) the cell density of the immobilized and suspended Chlorella sp. was significantly different (P<0.05), the cell density of immobilized Chlorella sp. was significantly higher than that of the liquid suspended Chlorella sp. at the late growth stage (days 6 - 10); (2) there was a significant difference in photosynthetic pigment content between immobilized and suspended cultures of Chlorella sp. (P<0.05), the contents of chlorophylls a and b and carotenoids of Chlorella sp. of immobilized alga were all higher than those of the suspended at the middle and late growth stages (days 4 - 10); and (3) the chlorophyll fluorescence parameters of immobilized and liquid suspended Chlorella sp. were significantly different (P<0.05). The potential vigor and actual light energy of immobilized Chlorella sp. at the later growth stage were higher than those of the suspension cultured. The conversion efficiency and quantum efficiency of fixed Chlorella sp. were significantly higher than those of suspension cultured alga (P<0.05). In summary, the immobilization culture significantly promoted the growth and photosynthesis of Chlorella sp.

Three investigations of phytoplankton were carried out in Nanwan Reservoir in Mar., May and Sept., 2016. Phytoplankton and water samples were collected simultaneously. The common water quality indicators such as total nitrogen, total phosphorus and the permanganate index were analyzed. The stress response was analyzed based on phytoplankton abundance-biomass curves and the relations between water quality and phytoplankton community. The results showed that the water quality indicators changed significantly. Except permanganate index in May, most of the indicators were lower and can meet with II or III water quality standards. The abundance-biomass curve based on phytoplankton showed that the water body was subjected to a large environmental disturbance in May and reduced to a heavy pollution stage in Sept.. Further analysis of the relationship between water quality factors and phytoplankton community showed that organic pollution (permanganate index) is the main pollution factor which was related to the intense agricultural production activities in spring.

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.

Wave breaking can induce enhanced turbulent mixing at the ocean surface layer, but whether typhoon enhances wave-induced mixing and how it affects the thermocline below the mixing layer remain unclear. In this paper, taking typhoon Nepartak as the research object, based on the coupled ocean-atmosphere-wave-sediment transport (COAWST) model, the effects of turbulent mixing caused by wave breaking on the depth, thickness, and strength of the thermocline in the northwest Pacific were studied. The results showed that: during typhoon Nepartak, the wave-induced mixing significantly strengthened the turbulent mixing below 100m, resulting in the deepening of the mixing layer, the reduction of SST, the obvious deepening of the upper boundary depth of the thermocline, the small change of the lower boundary depth, the thinning of the thermocline thickness and the slight strengthening of the intensity. In addition, the introduction of wave-induced mixing could significantly improve the simulation effect of COAWST model on SST during typhoon.

Mangroves, seagrass beds and salt marshes are important components of marine "blue carbon" and marine ecosystems with strong carbon sinks. Based on the relevant studies at home and abroad, in this paper, we reviewed the studies on the carbon sequestration capacity of several typical coastal wetlands like mangrove, seagrass beds and salt marshes, the impact of wetland damage on such capacity, and the difficulties met in restoring and improving their carbon sequestration capacity. The reviewed included also the existing monitoring methods of coastal wetland carbon sink at home and abroad. We put forward suggestions and prospects from several aspects which include current monitoring of coastal wetland carbon sink, wetland protection and sink enhancement. Globally, coastal wetlands have a strong carbon sequestration capacity, 10 times that of terrestrial ecosystems. With urban expansion, human exploitation and utilization, the coastal wetlands may be transformed into industrial and construction lands, which is the main influencing factor for the loss of carbon sequestration capacity of coastal wetland ecosystem. Wetland restoration is difficult, has a long cycle and holds more uncertainties. At present, the monitoring methods of coastal wetland carbon source and sink mainly include inventory, direct measurement, remote sensing monitoring and ecosystem model methods. While countries are constantly exploring and improving the researches on coastal wetland carbon sink survey, there are still many problems. Therefore, the researches on coastal wetland survey should be strengthened in the following aspects including conduction of coastal wetland carbon sink and habitat quality surveys, establishment of the blue carbon survey system of coastal wetland, changing wetland use into account, integration of existing carbon sink survey data into databases supporting the optimization of policy making model, and exploring continuously the application of new survey methods in carbon sink investigation.

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.

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.

Based on the survey data of 46 stations Qinhuangdao sea area in Summer2013, distribution of hlorophyll a concentration and its relationship with environmental factors water temperature, salinity, chemical oxygen demand, dissolved oxygen, active phosphate and inorganic nitrogen were , and the nutritional status of Qinhuangdao sea area was evaluated. The results showed that the concentration of chlorophyll a ranged from 0.50 to 7.79 μg·L^-1 with an average of 2.10±1.38 μg·L^-1. The horizontal distribution of chlorophyll a tended to near shore and off shore. Through the correlation analysis chlorophyll a concentration environmental factors and the analysis of nitrogen/phosphorus ratio (N/P), itfound that the active phosphate the main of chlorophyll a concentration. According to the evaluation of nutritional quality index (NQI) and eutrophication index (EI), the overall nutritional status of Qinhuangdao sea area was poor.

In order to enhance the prediction ability of the wave risk level in the key notes of the 21^st-Century Maritime Silk Road, in this paper, we evaluated the wave risk index and made statistics on the wave risk level in the Sri Lankan waters based on the ERA-interim reanalysis data. Our findings has a practical reference value for disaster prevention and mitigation, coastal development and coastal zone management in the future. Single index of wave risk based on wave height or wave period cannot replace each other, and single index of wave risk level cannot fully represent the real sea conditions. Under the double indicator assessment of wave risk, the spatial and temporal distribution of wave risk index in Sri Lankan waters shows obvious seasonal differences. The waves with a risk level of III accounts for the largest percentage. The large value area is mainly distributed in the small areas of the west and south of Sri Lanka. According to the distribution of the annual average wave risk index, the risk level of small area has reached level 1, but 75.72 % of sea area is at level III. The assessment of double indicator of wave risk more comprehensively reflects the real sea situation.

According to the principle of remote sensing water depth inversion, this paper used the WorldView-2 multi-spectral satellite remote sensing image and airborne Lidar data for four machine learning models, including extreme gradient boosting (XGBoost), support vector machine (SVM), kernel ridge regression (KRR) and least absolute shrinkage and selection operator (LASSO), to explore the impact of different machine learning models on the accuracy of water depth inversion. For deepth data, when the training sample and the test sample were the same, the grid search method was used to find the optimal parameter combination of the machine learning algorithm, and the water depth inversion experiment was carried out on the shallow waters around Ganquan island. Through the comparison and analysis of the inversion results of four types of machine learning models, the results were as follows: in the shallow water depth area of 20m, XGBoost model had strong learning ability, with correlation coefficient (R²) of 0.97, root mean square error (RMSE) of 0.85 m, average absolute error (MAE) of 0.63 m and average relative error (RME) of 19%, which was better than the other three machine learning models, and the overall effect was the best. It can be used to predict the water depth around Ganquan island and provide reference for subsequent water depth inversion research.

In this paper, a new type of breakwater structure of semi-elliptic breakwater was proposed, and a series of model tests were carried out on two different size semi-elliptic breakwater models. The aim of this study was to analyze the hydraulic characteristics of elliptic arc-shaped structural plane under wave action. The results provided a reference for the construction design of this new type breakwater. The influencing factors of wave force of semi-elliptic breakwater were determined byπtheorem, including wave steepness H/L, relative wave height H/D and scale parameter b/L. Based on the experimental data, the variation characteristics of wave forces on semi-elliptic breakwater with these three factors were analyzed and the stress characteristics of two semi-elliptic breakwater models were compared. The results showed that the wave force increased with the increase of H/D and decreased with the increase of H/L and b/L. The wave force in model 1 was larger, and the horizontal wave force was much larger than the vertical wave force. The wave force in Model 2 was smaller, and the horizontal wave force was close to the vertical wave force.

In recent decades, the traditional marine fishery resources in the coastal waters of China have declined and the offshore fisheries resources have become "hollow", thus the foundation of sustainable development of fishery is not firm. From the perspective of the resource economics, in this paper, we analyzed the economic reasons for the decline of offshore fishery resources and the hollowing of resources. By combining with the blue growth idea put forward by FAO, we probed into the economic and social benefits brought by the green development at home and abroad, and made some suggestions on realizing the capitalization management of fishery resources, expanding the reproduction of resources, and transforming the property right of fishery shared resources among other. Our analysis will provide a reference for the green development of offshore marine fishery of China.

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.

The seasonal variation and spatial distribution characteristics of TN, TP and Chl.a in 20 sections of the Sihe river from 2016 to 2017 were analyzed. The water nutritional status was evaluated by using the universal index formula in the form of a logarithmic power function, and the factors affecting the distribution of nitrogen and phosphorus nutrients, and their environmental effects were discussed. The results showed that the average mass concentration of TN, TP and Chl.a in Sihe river from 2016 to 2017 were 5.52±2.83 mg·L^-1, 0.24±0.25 mg·L^-1 and 36.56±26.98 μg·L^-1. The seasonal difference of nitrogen nutrients in water was not obvious; the seasonal variation of phosphorus nutrients was significant (p＜0.01), and the TP concentration in autumn was about twice of that in summer. The nitrogen and phosphorus nutrients in the Sihe river had obvious spatial distribution characteristic. The two areas with higher content were the confluence of the Jihe river, the Pushan river, and the Yihe river. Overall, the main pollutant in Sihe river was TN, which was in the state of severe eutrophication. The point source pollution of industrial wastewater and domestic sewage was the main source of the Sihe river pollution, and the non-point source pollution of livestock and poultry breeding and agriculture also made an important contribution. Based on the analysis of the annual variation data of TN and TP from 2011 to 2021, it was found that the TN concentration reached peak in 2016—2017 and then decreases gradually. The TN concentration in 2021 was about 70% lower than that in 2016. In recent years, the water quality of the Sihe river has been significantly improved through the treatment of ecological environment and the control of pollution discharge.

Long-term wind characteristics and wind energy potential along the Philippines coast from 1987-2016 were investigated based on 30-year hindcast data. The data of Cross-Calibrated Multi-Platform (CCMP) (1987~2016) wind field was the background wind field to reconstruct the wind field in the Philippines for 30 years. By comparison, the observed wind field and the reconstructed wind field were in good agreement. Based on the reconstructed data, the spatio-temporal patterns of annual, seasonal, and monthly averaged wind speed and wind energy in the Philippines were analyzed. The results showed that the maximum values of the mean annual wind speed and wind energy were in the northwest part of the Philippines. Wind energy were abundant in January, February and December and scarce in June, July, August and September. Twelve representative points along the Philippine coast were selected to draw wind and wind energy roses. A directional analysis showed that the dominant wind speed and wind energy directions were in NNE, NE, and ENE. Through the analysis of gale frequency, it was found that the frequency of wind speed above grade 6 the northwest Philippines was the highest (about 30%). In addition, the utilization efficiency of wind energy converts in north and east of Philippines was higher.

This paper uses the ERA5 grid point data of the European Center for Medium-Range Weather Forecasts, as well as sounding and automatic station observation data, to observe and diagnose a sea fog process that occurred in Qingdao offshore on April 27, 2021. Before the occurrence of the sea fog, the rainfall in the Huanghuai and Jianghuai regions provided abundant water vapor for the surface atmosphere. With the change of the surface wind direction to the southwest wind, the warm and humid air flowed from the northeast of Jiangsu to the offshore of Qingdao under the action of the offshore wind, and generates advection cooling fog when encountering the cold sea surface. Analysis of sounding data shows that there are two temperature inversion layers in this process. Sea fog is generated under a lower temperature inversion layer, and the fog layer is thinner. There are low clouds below the upper inversion layer, and the height continues to decrease due to the weak subsidence movement. The existence of strong southwest warm and humid air flow in the lower layer, coupled with the slow development and movement of cold air, and the relatively stable circulation situation on the sea surface make the sea fog maintain for a long time and with the influence of Northwest air flow, the fog layer dissipates.

Algal calcification is one of the main forms of biological calcification and an important component of calcification productivity. Calcification is currently known to exist in some species of both microalgae and macroalgae, and involve four sequential steps including (i) CO₂ concentration, (ii) Ca²⁺ aggregation, (iii) CO₃^2- enrichment and ultimately, and (iv) CaCO₃ deposition by ionic bonding between Ca²⁺ and CO₃². However, due to differences in morphology and physiology, microalgae and macroalgae have unique characteristics of calcification. In this review article, we summarized the four main steps and the key mechanism of algal calcification by the model species Synechocystis sp. PCC6803. Corallina and Coccolithophores are separately taken as models to compare and summarize the calcification process and mechanism of calcification processes in macroalgae and microalgae. Based on the above analyses, calcified algae have great application potentials in the fields of carbon sink fisheries, blue carbon, and nanomaterials.

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.