In this study, Argo surface salinity, OSCAR current and other data are used to explore the influence of oceanic advection transport on the surface salinity in the Tropical Indian Ocean based on the advection term of the salinity budget equation. The adjustment mechanism of the spatial structure of surface salinity by oceanic advection is revealed by freshwater transport calculation along 6 key sections. The results show that the oceanic advection which transports the high-salinity water in the Equatorial Western Indian Ocean (EWIO) and the Arabian Sea (AS) to the Equatorial Eastern Indian Ocean (EEIO), the Bay of Bengal (BOB) and the Andaman Sea, and also transports the low-salinity water in the EEIO, the BOB and the Andaman Sea to the EWIO, the AS and the Equatorial Southern Indian Ocean, plays a role in adjusting the basic balance of salinity in the Indian Ocean. The analysis of freshwater transport along sections shows that the inconsistency between the center of high precipitation and low salinity in the western sea area of Sumatra, and the inconsistency between the center of high evaporation and high salinity in the western sea area of Australia, are both caused by oceanic advection. In summer, the high-salinity water in the EWIO and the AS transported by the southwest monsoon forced circulation into the BOB, is the main reason for the high surface salinity in the BOB.

The dramatic change of sea ice in the Beaufort Sea has an important impact on the regional ecosystem and economic activities. Based on the sea ice concentration released by the National Ice and Snow Center of the United States, the mechanism of extremely low summer sea ice in the Beaufort Sea in 2019 is discussed. The sea ice area in the melt season (May–September) of 2019 is 1.38×10⁵ km², far lower than the average of 2.28×10⁵ km² from 1998 to 2020. According to the statistics of the sea ice area in the preceding autumn (October–December 2018) and winter (January–April 2019) of 2019, there is no significant difference between the 2019 and the average results of 1998–2019, so it is not the main reason for the extremely low ice event. Combining the data of sea ice drift field, sea ice thickness, 10 m wind field, and net sea surface heat flux, it is found that the sea ice in May of 2019 decreased by 2.33×10⁵ km², which is the largest of sea ice loss in May since 1998, accounting for 62% of the loss of sea ice area in the melt season. Different from the mechanism of extremely low summer sea ice area in 1998, 2008, 2012, and 2016, decreasing sea ice thickness and abnormally strong wind field in May 2019 contribute to the rapid sea ice export, resulting in the formation of open water in the south of Beaufort Sea on May 16, 2019. The abnormally high sea surface net heat flux makes the sea ice melt more, resulting in the abnormal phenomenon of sea ice in the summer of 2019. With the continuous thinning of sea ice thickness, the response of sea ice to wind field is stronger and stronger, and the time of sea ice retreat is advanced, the phenomenon of extremely low summer ice condition in the Beaufort Sea may appear more frequently.

Through the analysis of the δ¹³C, δ¹⁸O, δ¹¹B, δ³⁷Cl isotopes and Cl⁻, ${\rm{SO}}_4^{2-} $, K⁺, and Na⁺ ion index in the sediment pore water of the core GSW1 in the East China Sea outer Slope-Okinawa Trough, the changes of early diagenesis, fluid sources, migration and oxidation environment of sediments were discussed. The results show that the pore water dissolved inorganic carbon of the core GSW1 mainly comes from sea water and organic matter, the concentration of ${\rm{SO}}_4^{2-} $ decreases more gently with depth, and the concentration of Cl⁻ is much lower than seawater. The sulfate consumption in the surface sediments of this pore is mainly caused by organoclastic sulfate reduction (OSR) controlled, anaerobic oxidation of methane (AOM) occurs in deeper layers below 4 m. The H₂S produced by OSR diffuses upwards and is enriched and oxidized, which is the main factor that causes the 110−360 cm ${\rm{SO}}_4^{2-} $ content to not significantly decrease. The overall trend of pore water ${\rm{SO}}_4^{2-} $ concentration decreases with depth, indicating that the deposition environment of core GSW1 has gradually changed from an oxidizing and sub-oxidizing environment to a reducing environment. The vertical changes of δ¹¹B and δ³⁷Cl fluctuate greatly. On the one hand, they are affected by the degradation of organic matter in the early diagenesis stage, and they may also be related to the diffusion of pore fluid and sediment/pore water interaction.

To understand the internal physical mechanism of wave breaking, it is important to study the distribution characteristics of the particle velocity field under breaking wave. In addition, a comparative study of the evolution characteristics of the gas-liquid mixing zone caused by different types of breaking is beneficial to the improvement of the whitecap coverage model. In the laboratory wave flume, a critical wave, a single spilling wave, and a single plunging wave are generated in deep water based on the linear phase focusing theory. The velocity fields below the wave surface and the velocity fields in the gas-liquid mixing zone are measured using particle image velocimetry (PIV) and bubble image velocimetry (BIV), respectively. The distribution characteristics of the velocity field at the extreme state of different breaking types are compared and discussed. The results show that the horizontal velocity u and vertical velocity v of the spilling wave are extremely asymmetrical in the front part and back part of the wave crest. In addition, the maximum horizontal velocity u_max is not at the top of the wave peak, but at the pre-peak position about 0.7$\eta_{\max} $ front part and back part of the wave crest. In addition, the maximum horizontal velocity of the peak. For plunging wave, the maximum horizontal velocity u_max appears at the top and very front of the wave peak with a very small region, and the velocity gradient between this area and the surrounding area is very large. The development characteristics of the gas-liquid mixing zone produced by different wave breaking also have differences. For spilling wave, the gas-liquid mixing zone generated by breaking has high horizontal movement speed, long influencing area, short influence time at each location, and small thickness. For plunging wave, the gas-liquid mixing zone has relatively slow horizontal movement speed and larger vertical input, shorter affected area, longer affected time at each location, and greater thickness.small thickness. However, for plunging wave, these characteristic parameters are in contrast with those of the spilling wave.

Hollow blocks have good water blocking and siltation promotion functions, and have been widely used in ecological restoration projects in recent years. In this paper, combined with flume experiment and Flow-3D numerical simulation, the water blocking effect and sedimentation characteristics of open and semi-closed hollow blocks are analyzed. The results show that the permeability of the hollow block plays a leading role in the internal flow velocity and turbulence intensity, and the semi-open hollow block with small permeability has a better effect in slowing down and turbulence control. The suspended sediment concentration near the bottom of open and semi-closed hollow blocks increases by 56% and 75%, respectively. Both of them can promote the deposition of sediment in the block. The environment of low flow velocity, sediment micro-deposition and water and sediment connected inside and outside by hollow blocks is the habitat requirement of macrobenthos, the structure of low turbulent flow inside the semi-enclosed hollow block is more favorable for the habitat and reproduction of macrobenthos.

In this paper, MIKE3 is used to establish a three-dimensional hydrodynamic model of Zhoushan and Ningbo. Based on the tidal current verification with the measured data, the difference between the three-dimensional model and the two-dimensional model is compared. Also, the influence of the change of the tidal current field around the Zhoushan Green Petrochemical Phase III reclamation project before and after the implementation is mainly predicted and analyzed. The results show that: (1) Under the same initial conditions, the tidal level and tidal current validation results of two-dimensional model and three-dimensional model are good, and the two-dimensional results are closer to the measured values in some cases. (2) The three-dimensional vertical velocity distribution shows a decreasing trend with the increase of water depth. In general, the tidal current fitting is good, and the relative error of velocity below 0.6H water depth is between 10% and 15%. Considering that the model may not consider the influence of wind field and wave, the calculated surface velocity of local stations is slightly larger than the measured value; the vertical distribution of flow direction is nearly consistent. (3) Before and after the reclamation project, there was no obvious influence on the tidal current field around the project. Only in the northeast, southeast and northwest corner of Dayushan Island, affected by the “bend improvement” and the channel closure between small islands, there is a change in the local tidal current form. On the whole, the layout of reclamation projects conforming to the shoreline will have an effect on the local coastal tidal current, and almost no effect on the large scale tidal current field in the far sea.

When oil spill occurs and the large scale covering on the sea surface has not been formed, it is hard to find oil film by existing oil spill detection technology. To solve this problem, a novel method for discriminating of oil spill by monitoring the area of oil film is presented based on thermal infrared video image, which combined with the diffusion characteristic of oil spill. Firstly, foreground regions (real oil film region and look-alikes interference region) on the sea surface are extracted and the actual physical area of each region is calculated based on single-frame thermal infrared image processing (i.e., the pixel area calculation method from the previous research). According to the video image processing, the change of the actual physical area of each region is tracked in real-time. The area change rate threshold is set to discriminate whether oil film on the foreground regions, then whether oil spill happened can be determined. The experimental results show that the proposed method can effectively discriminate oil film formed by different viscosity of oil and maintain good identification accuracy under sea surface with waves and floating objects. This strategy is suitable for specific scenes such as wharves and ships, and also can provide technical support for pollution control of oil spill.

Bacterial membrane vesicles (MVs), which are a kind of biological nanoparticles carrying proteins, nucleic acids, signaling molecules, and other important compounds, are involved in a variety of physiological and biochemical processes, such as horizontal gene transfer, quorum sensing, biofilm formation and so on. Studies showed that marine extracellular vesicles might be the third largest biological entity except for phages and bacteria. Besides, MVs-mediated intercellular communication across species could be of great significance to marine ecosystems. However, very little is known about the specific ecological role and biological function of MVs in the marine biosphere. In this review, we discuss the role of bacterial MVs in marine micro-ecology, marine symbiotic system, and the impact of MVs-mediated material delivery on marine ecosystem. Meanwhile, we also put forward some questions and opinions for study in marine bacterial MVs’ research.

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.

Based on the latest measured high-resolution shallow profile and multibeam bathymetric data in the West Philippine Basin in 2018, the marine geological disasters in the central rift and surrounding areas of the West Philippine Basin is analyzed in this paper. In the study area, two types of disaster geological factors are identified: one is destructive geological factors, mainly including landslide, active fault, gully and magma diapir; the second is the restrictive geological factors, mainly seamounts, scarps and trenches. Based on the shallow seismic profile, the type, shape and internal structure characteristics of geological hazards bodies are described in detail. The distribution area and development characteristics are discussed. The main inducing factors and adverse effects of geological hazards are discussed. The identification of geological hazards, the delineation of distribution range and the analysis of causes in the study area can provide important geological basis for marine engineering construction, equipment design and maritime navigation, avoid adverse effects and make risk prediction in advance.