The salt-containing characteristics of soft soil are an important indicator of foundation design, and salt-containing features are mainly protected by deposition environment, often with strong geographicalism. In the Changjiang River Ekimae, the softener of the Changjiang River Ekimae is a research object, collecting multi-sets of soil samples for indoor trials, and conducts salt-containing characteristics, parameter correlation and deposition environment analysis. The results show that the salt-containing salt is NaCl type, the salt content is 0.613%, mainly based on weak saline soil, accounting for 85.4%. The salt content, Cl⁻ content, Na⁺ content, K⁺ content peak test meets the regular distribution, but the reputation test value is located in the rejection domain, and does not belong to normal distribution. Other ion assumptions and peak tests do not comply with the right to distribution. The salt content of soft soil is highest in relationship with Cl⁻content, and is good to ion-relevance to the Ca²⁺ content and ${\rm{CO}}_3^{2-} $. The content of the soil-solvent Cl⁻ content and salt content, the ${\rm{SO}}_4^{2-} $ content is equipped with the highest multiplication effect; Cl⁻ content is best fitted with Na⁺, Ca²⁺, Mg²⁺, K⁺, ${\rm{HCO}}_3^- $ contents fitted to polynomial fitting effect. The soft soil is deposited by an alkaline environment. The sodium adsorption ratio of soft soil is 54.35, which is close to the sodium adsorption ratio of seawater, indicating that the salt-containing characteristics retains the seawater characteristics, and with the increase of depth, soft soil sodium adsorption ratio has reduced trend. The soft soil formation time is related, the older the formation of soft soil, the longer the time of penetration. The Sr/ Ba value of the soft soil is much greater than 1, indicating that the soil deposition environment is a marine environment. The γ_Mg/γ_Ca value in the soft soil leaching solution is much higher than the γ_Mg/γ_Ca background value, which is subjected to seawater dipping. The seawater mixing model is introduced, and the seawater mixing ratio is calculated. The low value of the seawater mixing ratio is mainly distributed in the west far away from the coast, and the soil deposition in this area is mainly controlled by the water of the Changjiang River. The high value of seawater mixing ratio is mainly distributed in coastal areas, where soil deposits are mainly controlled by transgression, and the marine facies attributes are heavier.

In order to explore the diversity of pure cultured bacteria in the deep-sea sedimentary environment of the Indian Ocean, bacteria were isolated and identified from 12 sediment samples collected from the Indian Ocean. A total of 343 strains of bacteria were obtained by pure culture isolation method and 16S rRNA gene sequence analysis showed that these isolates belonged to Firmicutes, Proteobacteria, Actinobacteria, Bacteroidete and were divided into 5 classes, 13 orders, 26 families and 121 species under 39 genera. The dominant taxa were Streptomyces (separation rate is 16.53%) and Bacillus (separation rate is 8.26%), among which there were 12 potential new taxa. The results show that the deep-sea sedimentary environment of the Indian Ocean is rich in culturable bacteria and contains many new species; secondly, the isolation and culture methods are directly related to the bacterial species diversity obtained from marine sediments.

To understand the species composition of the dominant fish species communities in the East China Sea and to monitor and protect their diversity, environmental DNA technology to analyze the species diversity of fish in the East China Sea was used in this study. Through the collection of seawater samples, eDNA extraction, amplification and high-throughput sequencing analysis, a total of 44 species of marine fishes in 2 classes, 23 orders, 29 families and 42 genera were detected, and most of the species were found in the traditional fishery resources survey in the East China Sea. Among them, the species with high relative abundance were red nose anchovy (Thryssa kammalensis), blue-spotted horse mackerel (Scomberomorus niphonius), Japanese mackerel (Scomber japonicus), small yellowtail (Larimichthys polyactis) and mullet (Mugil cephalus). The alpha diversity among stations was significant difference, and generally showed high biodiversity at coastal stations and high biological abundance at offshore stations. The results suggested that environmental DNA technology could quickly explore the diversity and spatial distribution of fish species in the East China Sea, as an effective supplementary to traditional fisheries resource monitoring.

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.

In this paper, using the equatorial beta-plane approximation of the linear barotropic perturbation equations and introducing the reduced gravitational acceleration, we obtain the analytical solutions of anomalous equatorial ocean stationary wave and give the calculation results of the solutions. Then we compare the results with the modes of complex EOF analysis about abnormal circulation of the real tropical Pacific Ocean and Indian Ocean. The main conclusions are: in the first mode of anomalous equatorial ocean stationary wave, the current disturbance throughout the whole ocean is the half wave, which appears as the consistent zonal flow. The maximum disturbance appears at the middle of the tropical ocean and decays rapidly from equator to north and south, which is restricted in about 2 degree range on both sides of the equator. In the second mode, the current disturbance throughout the whole ocean is the full wave and has the opposite flow direction at east and west of the ocean. The degree of the attenuation of the current disturbance from equator to north and south is as that of the first mode. Anomalous equatorial ocean stationary wave meets the boundary conditions of the east and west coast directing along the longitude. The coefficient is inversely proportional to the square root of the product of the reduced gravity acceleration and the upper water standard depth, which determines the decay rate of anomalous equatorial ocean stationary wave on both sides of the equator. If the square root values take the same, the decay rates are the same. The oscillation frequency of anomalous stationary wave is proportional to the modal number and the square root values, which is inversely proportional to the width of tropical ocean. The modal number is lower and the width is larger, the frequency is lower and the corresponding oscillation period is longer; the first mode of the oscillation period is the longest. Taking every parameters as the typical values and the modal number as one, then taking the width of the equatorial Pacific Ocean and Indian Ocean respectively, the calculation results show that the spatial distribution and interannual variability of the first mode are the same as the corresponding mode of the real abnormal circulation obtaining from the complex EOF analysis; this means that the nature of the first mode above is the anomalous equatorial ocean stationary wave and the anomalous stationary wave is one of the generating mechanism of ENSO and IOD.

Based on the data of Philippine shallow strata profile, combined with the sample data and borehole data in this area, this paper has a preliminary understanding of the shallow sediment characteristics of Kyushu-Palau Ridge and the West Philippine Basin and Parisi Vera Basin adjacent to the ridge. There are generally three wave impedance interfaces below the seabed, and the reflection characteristics of the shallow stratum profile are divided into four basic types. The causes of the profile characteristics are preliminarily discussed. It is believed that the sediment supply, tectonic activities, topography and hydrodynamic conditions play an important role in the deep-water sedimentation during the sedimentation process. Besides being influenced by the main control factors, most of them are also superimposed with the transformation effects of various factors in the later period. In this paper, the sedimentary characteristics and controlling factors of shallow strata in Philippine Sea are analyzed, which can provide useful reference for further study of deep shallow sediments in Philippine Sea.

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.

Morphodynamic relationships between fringing reefs and back-reef beach play key roles in understanding the evolution of coral coasts. The fringing reef coasts of Leizhou Peninsula, in Xiluo Port, Xuwen, are taken as the research object in this paper. RTK-GPS and unmanned-surface-vessel are used to measure and analyze the topography of the beach profile and reef as well as the sediment sampling in beach. FUNWAVE-TVD is used to simulate and analyze the hydrodynamic process of short wave and infragravity wave cross the different reef. The results show that the reef topography in the study area has significant effects on the morphology of back-reef beach. Whether the nearshore wave energy dominated by the short wave band or the infragravity band is controlled by the topography. In the narrow reef, there is a predominance of infragravity energy near the back-reef beach. The dominated wave band in the nearshore wave energy is the main factor shape the back-reef beach equilibrium profile. However, the beach equilibrium profile model of coral coast proposed by Muñóz-Pérez did not take this factor into account, it need to further research.

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.

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.