With the rapid economic development and increasing anthropogenic activities, the groundwater in the coastal area has been excessively exploited. The resulting seawater intrusion has become a widely distributed environmental geological problem. Taken the coastal area of Laizhou Bay as a research area, the dynamics of groundwater level (GWL) and electrical conductivity (EC) were analyzed with the continuous monitoring data. Based on the rainfall, evaporation, tide and agricultural irrigation and drainage electricity consumption that affect the groundwater variation, the hybrid model of wavelet analysis (WA) and NARX neural network was introduced to predict the dynamics of GWL and EC. The root mean square error (RMSE) and goodness of fit (R²) were used to measure the prediction accuracy. The results showed that the annual variation of GWL was characterized by a type of rainfall infiltration-exploitation. A significant correlation at the frequency of 0.5 d was observed between groundwater level and tide, and the influence of tide on EC was weaker than that on GWL. For the dynamics prediction with WA-NARX method, the RMSE was less than 0.03 and R² was greater than 0.98 in both the training and testing stages. The results indicated the hybrid model had a good performance and could effectively predict the dynamics of GWL and EC. The effects of different influencing factors as model input parameters on the prediction results were further compared. The results showed that rainfall and tide parameters were the main variables affecting the GWL and EC variations in the coastal zone. The pumping information reflected by the evaporation and agricultural drainage and irrigation power consumption also affected the groundwater dynamics. The degree of influence was related to the observation frequency. The research results can provide theoretical and technical support for real-time monitoring, prediction and early warning of seawater intrusion in coastal zone.

In view of the prominent partial wind effect on islands, the wind profiles of idealized islands topography with three slopes are fitted by means of boundary layer wind tunnel test and numerical simulation. The difference factor is defined to describe the variation of wind profile, the distribution of maximum acceleration ratio and difference factor on the windward side of islands is studied by numerical simulation, and the effects of island slope and height on maximum acceleration ratio and difference factor are discussed comprehensively. Moreover, based on the wind tunnel data, the along-wind, cross-wind and vertical turbulence intensity and gust factor of the windward and leeward sides are studied. The results show that the numerical simulation is basically consistent with the wind tunnel test results and the wind profile exponent (α) is smaller on the windward side of islands. It also shows acceleration effect near the top of the island is particularly obvious and its maximum acceleration ratio is between 0.4 and 1.0. Moreover, the difference factor at the hillside is lower, and with the increase of the angle of the island ridge, the position where the difference factor is 0 tends to approach the slope toe. As the island slope increases to 25°, the maximum acceleration ratio and difference factor on the 0° island ridge are large. The distribution of three-dimensional turbulence intensity on the windward side is relatively regular, while that on the leeward side is disordered especially in the range of 100 m away from the island’s surface. It is worth noting that the trends of gust factor and turbulence intensity are highly consistent.

To overcome the difficulty of removing the wind field contribution in the SAR Doppler centroid anomaly method when retrieving the ocean surface current, in this paper, a secant downhill method based on the M4S model is proposed. The contribution of the wind field is removed by iteratively calculating the sea surface current field in a local area and subsequently estimating the wind contribution factor to the Doppler velocity of the whole SAR map. Our method is used to retrieve the radial velocity of sea surface from Radarsat-2 data. Its retrieval accuracy is verified by matching measured data. The results show that the proposed method not only can possess well convergence and high convergent speed, but also the deviation of the radial velocity of the surface is 0.04 m/s and 0.15 m/s respectively for two scene SAR data used in this paper.

Based on mesoscale eddy dataset from February 1993 to January 2016, the distribution characteristics and evolution processes of mesoscale eddies in the Indo-Pacific Warm Pool (15º S~15º N, 60º E~170º W), and its seasonal variation and relationship with ENSO are statistically analyzed in this paper. It shows that most mesoscale eddies in the Indo-Pacific Warm Pool are short-lived and nonlinear, and propagate westward. The study also finds that the distribution characteristics of cyclonic eddies and anticyclone eddies are similar, and so do their variation trends over the eddy lifecycle. The seasonal numbers of mesoscale eddies vary insignificantly in the whole domain and are affected by ENSO in the meanwhile.

Water transparency (Z_sd) is an important optical parameter for evaluating water quality. This paper tuned a remote sensing model for estimating Z_sd from MODIS (moderate resolution imaging spectroradiometer) data in the South Yellow Sea. This model was then used to analyze the spatial and temporal variations of Z_sd in the South Yellow Sea based long-term MODIS data in the past 20 years (2002–2020), and their driving factors were examined. The results show that the Z_sd estimation model has good accuracy with R², root mean square error and mean absolute percent error values of 0.91, 1.69 m and 25.1%, respectively. The Z_sd levels are generally high in the offshore but low in the coastal area. Meanwhile, Z_sd indicates high values in summer but low values in winter. In the past 20 years, Z_sd in the central South Yellow Sea, the southern South Yellow Sea and the Changjiang River Estuary showed slowly increase trends, while Z_sd in the Jiangsu coast was decreasing slowly. In general, the Z_sd is negatively driven by the concentration of suspended particulate matter, of which the influence is the greatest. In addition, sea surface temperature and solar radiation have positive driving effects on Z_sd, while wind speed has negative driving effect.

In recent years, artificial islands have been widely constructed in coastal areas to quickly obtain high-quality land resources. However, the construction of artificial islands may exert substantial effects on the distribution patterns and transport processes of offshore seabed sediments. To understand the changes and transport characteristics of sediments after the construction of artificial islands, this article focuses on the impact of Nanhaimingzhu (NHMZ) artificial island on the properties and distribution of offshore seabed sediments in the Haikou Bay. With surface sediments sampled respectively in the offshore of the Haikou Bay before and after the construction of NHMZ artificial island, the changes in sediment characteristics were analyzed. The impact of NHMZ artificial island on the surface sediments properties and transport trend in the Haikou Bay was discussed with sedimentary dynamic and grain size trends analysis. The results showed that the surface sediment properties changed significantly after the construction of NHMZ artificial island, with the fine-grained sediment composition increased, grain size decreased and the sorting worsen. It was found that the weakening of sedimentary dynamic conditions in the Haikou Bay caused by NHMZ artificial island was an important factor for the changes in seabed surface sediments grain size and the trend of sediment transport.

In this study, we used stable isotope technology to analyze different species (fish, crustaceans, cephalopods, benthos, etc.) collected in spring, summer and autumn in the coastal waters of Jiangsu Province. We used SIBER model to calculate the trophic niche of consumers, and calculated the quantitative indicators of six metrics in different seasons. The results showed that there were no significant differences in δ¹³C and nitrogen δ¹⁵N values among three seasons (p>0.05). In spring, the δ¹³C values ranged from −24.47‰ to −14.50‰, the δ¹⁵N values ranged from 6.86‰ to (14.98±0.49)‰, and the trophic level ranged from 1.52 to 4.28±0.17. In summer, the δ¹³C values ranged from −19.86‰ to −14.44‰, the δ¹⁵N values ranged from 5.79‰ to (12.54±3.50)‰, and the trophic level ranged from 1.25 to 3.52. In autumn, the δ¹³C values ranged from (−22.17±4.90)‰ to (−14.21±0.36)‰, the δ¹⁵N values ranged from 6.30‰ to (14.60±0.51)‰, and the trophic level ranged from 1.34 to 4.15±0.14. The structure of food web was stable in each season, and the trophic niche of some species overlaps in different degrees. In addition, the food sources are more extensive, and the trophic level and community diversity are higher in spring, the food sources of consumers are more abundant, but the degree of trophic niche differentiation is lower in summer, while in autumn, the structure of food web is relatively simple, but the distribution of trophic niche is wider.

Corals are one of the carriers for recording information about changes in the marine environment. For example, determining U/Ca to reconstruction of sea water temperature or measure the Th/U isotopic ratio for dating to reconstruction sea level etc. However, measuring the U and Th contents and isotopic ratio of corals is a prerequisite for extracting the recorded marine environmental change information, the difficulty lies in the separation of Ca matrix and enrichment and purification of trace U and Th. Based on this, this study modified the pretreatment method of separation and purification U and Th with single column stage of UTEVA resin, and then combined with high resolution inductively coupled plasma mass spectrometry to determine U and Th contents of corals. The results demonstrate that the HNO₃ medium concentration decrease from 3 mol/L to 2 mol/L will not affect the absorption efficiency of U and Th; 2 mL Milli-Q water can completely elute U, which significantly reduces the procedure blank value of the entire process of U; the improved method is used to determine the U and Th contents of three Hainan littoral corals (n=6, 1σ): U are (3.46±0.02)μg/g, (2.67±0.05)μg/g, (2.15±0.07)μg/g, respectively, Th are (10.12±0.24)ng/g, (4.82±0.10)ng/g, (5.65±0.12)ng/g, respectively; and the determination accuracy is below 3.3%, recovery rate of standard addition of U, Th are 97.9%–100.9%, 97.3%–99.7%, respectively. The method has high accuracy and good precision. This study provides a more accurate, convenient and rapid experimental method for the analysis of U and Th content and isotopic ratio in corals and other carbonate samples.

According to the bottom trawl survey data of fishery resources in the offshore waters of Shandong from 2016 to 2017, the spatial autocorrelation and spatial heterogeneity of demersal fish in the offshore waters of Shandong were examined by using spatial autocorrelation indices and variogram. The results showed that there were significant spatial aggregation patterns and spatial autocorrelation in the demersal fish in the offshore waters of Shandong. The spatial autocorrelations were strong in spring, summer and winter, and weak in autumn. From the perspective of spatial distribution, the areas of high relative abundance index of demersal fish were mainly located in the southern waters of Shandong in spring and summer, and areas of high relative abundance greatly decreased in autumn and winter, while the areas of low value were mainly in the Laizhou Bay and adjacent waters in four seasons. The parameters of variogram showed that there was a strong nugget effect in autumn, and the spatial heterogeneity of random part accounted for 76.0% of the total spatial heterogeneity. The spatial heterogeneity of random part in spring, summer and winter only accounted for 26.2%, 27.7% and 23.6% of the total spatial heterogeneity. In the spatial autocorrelation and spatial heterogeneity of demersal fish showed seasonal variation in the offshore waters of Shandong, which was to some extent related with changes in environmental factors such as water temperature.

According to the data collected in April (spring) and October (autumn) of 2018 in the eastern sea area of Zhoushan Islands (29°10′25.54′′−30°45′00′′N, 122°53′3.88′′−124°48′28.31′′E) based on the crab data obtained from bottom trawl survey of fishery resources, the community structure characteristics of crab resources such as species composition, dominant species and biodiversity were studied, and the relationship between crab quantity distribution and community structure and environmental factors such as temperature and salinity was analyzed. The results show that there are 40 species of crabs in spring and autumn, belonging to 23 genera and 12 families; among them, the dominant species in spring is Charybdis bimaculatus, and in autumn are C. bimaculatus and Portunus trituberculatus; the richness index (D) and Shannon Wiener-diversity index (H′) in autumn are higher than those in spring, while Pielou evenness index (J') is similar in spring and autumn; independent sample t-test show that there is significant difference between spring and autumn; according to cluster analysis and non metric multi-dimensional scaling analysis, spring can be divided into four communities, and autumn can be divided into four communities; canonical correspondence analysis show that bottom water temperature and surface salinity are the main environmental factors affecting the community structure and quantity distribution of crabs in the investigated sea area.