We can discover that there exist storm currents along Yangjiang sea area of western Guangdong waters in spring and summer of 2019 by analyzing materials which measure hydrologic and hydrometeorological along west coast of Guangdong flow Yangjiang sea area from 2018 to 2019. The result of research shows: Firstly, the velocity of 2 m water depth at the observation site reached 164.7 cm/s and 9 m water depth at the observation site reached 127.6 cm/s at 6:00 a.m. on May 5, 2019. The velocity of Yangjiang Shapa sea area 2 m water depth at the observation site reached 161.8 cm/s and 9 m water depth at the observation site reached 156.6 cm/s at 4:00 to 5:00 a.m. on August 1, 2019. Secondly, the suddenly strong currents in spring and summer have typically shock current trait in the Yangjiang 20 m to 30 m sea area along the shore current area of western Guangdong. The strong current happens at the surface of the ocean during the time of rising tide for 2 h to 4 h. Thirdly, during the transition period of southwest wind and northeast wind, the coastal sea area of western Guangdong is prone to form a water convergence zone. The sea level of the coastal sea area rises, and the sea level of the offshore sea area drops. The strong horizontal pressure gradient force from the shore to the outside causes the coastal water to strengthen the westward movement, resulting in shock current.

In this paper, sediment smear observations, X-ray diffraction analyses, major, trace and rare earth elements analyses, and in situ micro zone geochemical analyses of single minerals were carried out on samples of core GC02 and GC06 from the rare earth-rich deep-sea sediments in the Central Indian Ocean Basin to explore their geochemical characteristics, material sources and enrichment mechanisms of rare earth elements (REY). The results show that the sediment types of core GC02 are calcareous clay and zeolitic clay, and the sediment types of core GC06 are calcareous clay, zeolite-bearing clay and zeolitic clay. Rare earth elements are enriched in zeolite-bearing clays and zeolitic clays. The North American Shale Composite (NASC) Standardized patterns of REY in the sediments indicate a possible seawater origin. Mineralogical and geochemical signatures indicate that the terrestrial fraction of these sediments in the study area should be the eolian dust material originated primarily from Australian. Elemental correlations and CaO/P₂O₅ ratios indicate that the main host mineral of REY in REY-rich deep-sea sediments is bioapatite (fish teeth/bone), followed by Fe-Mn micronodule. This study summarizes and discusses the formation mechanism of REY-rich sediments and improves a conceptual model for the formation process of REY-rich sediments.

Based on the non-hydrostatic numerical calculation model, this paper systematically studies the wave dissipation characteristics of permeable submerged breakwater under the impact of focused wave. By setting reasonable calculation conditions, the effects of wave height, water depth above the submerged breakwater, spectral peak period, porosity and the crest width of submerged breakwater on the wave dissipation characteristics of permeable submerged breakwater are analyzed in detail. At the same time, the calculation results of permeable submerged breakwater are compared with those of impermeable submerged breakwater. The calculation results show that the attenuation effect of permeable submerged breakwater on focused wave is stronger than that of impermeable submerged breakwater, which shows that permeable submerged breakwater can more effectively reduce the impact of freak wave on coastal infrastructure; wave height and the water depth above the submerged breakwater are important factors affecting the wave dissipation characteristics of submerged breakwater. With the increase of incident wave height and the decrease of the water depth above the submerged breakwater, the wave dissipation effect of permeable submerged breakwater increases gradually. The permeable submerged breakwater has poor wave dissipation effect on large-spectrum peak period waves. Within the range of porosity considered in this paper, as the porosity increases, the wave dissipation effect of permeable submerged breakwater is better; when the porosity is 0.4 and the crest width is 0.6125 m, the permeable submerged breakwater can reduce 54% of the incident wave energy, which is 36.1% higher than that of the impermeable submerged breakwater. The research results of this paper can provide corresponding reference for further understanding the wave dissipation characteristics of permeable submerged breakwater and the design of coastal protection engineering.

Based on the ERA5 reanalysis data and the meteorological observation data obtained during Chinese Arctic Research Expeditions, the temporal and spatial variation characteristics of the key near-surface meteorological parameters that influence ship navigation in the Arctic passages in summer are analyzed. The results show that the weather conditions in July and August are the most suitable for ship navigation in the Arctic passages. The low temperature, strong wind and huge wave weather increase significantly in September, which impacts ship navigation greatly. The weather in October is even worse, posing a quit challenge to ship navigation. Low temperature mainly occurs in the middle of each passage, and strong wind and huge wave are concentrated in the areas at both ends of the passages. Both the strong wind probability and huge wave probability show a decreasing tendency in the entire Arctic passages in summer with large interannual changes except for the Norwegian Sea and Barents Sea in October and the central Arctic in summer. According to the observation data, it is found that the northeast passage has the poorest visibility, the northwest passage has the best visibility, and the trans-Arctic passage has moderate visibility.

The Bering Sea is one of the most obvious areas with reduced winter sea ice in Arctic region. The seasonal and long-term variations of sea ice in this region are closely related to the local climate, hydrological environment and ecosystem, as well as to Chinese weather and climate. In order to identify the long-term variation of winter sea ice in this region, the trend and spatial difference of sea ice extent in Bering Sea from 1960 to 2020 were analyzed by using the sliding t-test and linear regression analysis method based on Hadley Center data, and the effects of atmospheric forcing, such as general circulation, on sea ice change were analyzed. The results showed that the winter sea ice extent of the Bering Sea decreased significantly from 1960 to 2020, and there were significant abrupt changes in the 1970s and around 2000. During these processes, the Aleutian low pressure center and low pressure were strengthened, the core position shifted to the west of Bering Sea and the corresponding wind field distribution changes. Such process has a nearly 20-year cycle of oscillation. At the same time, the phase change of the Pacific Decadal Oscillation can regulate the meridional wind by changing the sea level pressure, and alter the thermal advection into the Bering Sea, thus affecting the winter sea ice extent. Therefore, winter sea ice in the Bering Sea is mainly controlled both by the Aleutian low pressure system and the North Pacific decadal oscillation, as well as the gerneral climate warming.

To analyze the effects of wave height, vegetation density, submerged height of vegetation and current on the bed shear stress at vegetation zones, a three-dimensional wave-current numerical flume is established based on OpenFOAM in this study. The results show that the bed shear stress attenuates along the vegetation zones because of the blocking effect of vegetation, and the decay rate is positively correlated with the wave height, vegetation density and submerged height of vegetation. Compared with pure wave, the amplitude of positive bed shear stress increases and the amplitude of negative bed shear stress decreases under the condition of combined wave-current flows. The weak current has no obvious effect on the size and distribution of the bed shear stress at vegetation zones. In the case of strong current, the bed shear stress increases at vegetation zones and suddenly decreases after the vegetation zones.

In order to understand the relationship between zooplankton species in the Zhoushan waters and the impact of environmental factor changes on the niche differentiation of dominant species, according to the survey data of zooplankton in the Zhoushan waters in the summer of 2019 and 2020, the dominance index was used to judge the dominant species of zooplankton in this sea area. The Shannon formula and the Pianka formula were used to analyze the niche breadth and niche overlap index of the dominant zooplankton species, and the redundancy analysis (RDA) method was used to explore the main environmental factors affecting the niche differentiation of the dominant zooplankton species in the Zhoushan waters for two years. The results showed that the replacement rate of dominant zooplankton species in the Zhoushan waters was 66.67% in 2019 and 2020. According to the niche width value of the dominant species of zooplankton in the offshore Zhoushan waters, they could be divided into broad niche species, medium niche species, and narrow niche species. They accounted for 66.67% and 60.00% of the dominant species of zooplankton in 2019 and 2020, indicating that the broad niche species were the main components of the dominant species of zooplankton in the coastal waters of Zhoushan. The niche overlap index of the dominant zooplankton species ranged from 0.11 to 0.79 in 2019, and the range of the niche overlap index in 2020 was from 0 to 0.98. RDA analysis showed that the niche differentiation of zooplankton dominant species in 2019 was mainly affected by SiO₃-Si concentration, COD, temperature and Chl a concentration, and the niche differentiation of zooplankton dominant species in 2020 was mainly affected by SiO₃-Si concentration and DO concentration. This study is expected to further understand the interspecific relationships of zooplankton communities in the Zhoushan waters, and provide a data basis and scientific basis for studies such as elaborating the adaptation mechanism of zooplankton to environmental changes.

Tidal replacement has a significant impact on the physiology and behavior of intertidal organisms. Infauna can establish a suitable microenvironment to adapt to intertidal environment through the behavioral process. In this experiment, the behavioral response of Perinereis aibuhitensis Grube to tidal alternation were studied by behavioral observation device. Three temperature grades (15℃, 20℃ and 25℃) and four time periods (T1: before ebb tide, T2: after ebb tide, T3: within 30 minutes after rising tide and T4: 30 minutes after rising tide) were set up for the experiment, with six replications for each experimental group. The results showed that at the same time period, the radial undulation frequency, radial undulation pumping rate, axial crawling velocity and the frequency of head-tail exchange of P. aibuhitensis Grube tended to increase with the increase of temperature, while the time of head-tail exchange tended to decrease. At the same temperature, the radial undulation frequency, axial crawling velocity, radial undulation pumping rate, radial undulation pumping efficiency, axial crawling time and the frequency of head-tail exchange of P. aibuhitensis Grube in T3 were higher than those of other time periods, while the time of one head-tail exchange was lower. There was no significant difference in all behavioral indexes between T1 and T4 (p>0.05). At 20℃, the radial undulation frequency and pumping rate of P. aibuhitensis Grube in T3 were higher than T1. At the same time period, the radial undulation time and axial crawling time of P. aibuhitensis Grube were at the maximum and minimum at 20℃, respectively. There was no significant difference in axial crawling velocity of P. aibuhitensis Grube at 15℃ and 20℃ in T1 and T3. However, at 25℃, the axial crawling velocity in T3 was significantly higher than T1 (p<0.05). The results indicate that the motion intensity of P. aibuhitensis Grube increased with the increase of temperature. The motion state of P. aibuhitensis Grube was better at 20℃. After ebb tide, it is an important time for P. aibuhitensis Grube to forage for sediment, and its axial crawling motion is relatively slow. At the beginning of the rising tide, the motion intensity of P. aibuhitensis Grube increased significantly. 30 minutes after the rising tide, the motion of P. aibuhitensis Grube gradually returns to a state similar to that before the ebb tide. P. aibuhitensis Grube can deal with the adverse effects of tidal replacement through a series of behaviors.

Driven by the reanalysis wind data NCEP CFSV2, the third-generation wave model SWAN is utilized in a self-nested grid system to simulate waves in the Beibu Gulf (BG), South China Sea (SCS) for a period of one year. The model accuracy is examined by comparing the numerical results with the Jason-2 satellite altimetry data and the near-shore buoy measurements. Based on the numerical simulations, the influence of spatial resolutions on model predication is evaluated, the seasonal characteristics of waves in the BG are analyzed, and the forcing contributions of local wind in BG and sea waves from SCS are discussed. The results show that: (1) Compared with the Jason-2 satellite data, the root-mean square bias (RMSB) and scatter index (SI) for significant wave height are approximately 0.4 m and 0.2, respectively. Compared with the near-shore buoy observations, the RMSB and SI for significant wave height are about 0.2 m and 0.4, respectively; the RMSB and SI for mean wave period are roughly 0.6 s and 0.2, respectively; and the RMSB for mean wave direction is around 30°. (2) The numerical model with the spatial resolution 12'×12' can predict reasonable results for the open sea area of BG, and the mean relative bias compared to the model results of 2'×2' is not exceeding 10%. (3) In the BG, the northeasterly waves prevail in winter monsoon, the southerly waves reign in summer monsoon, and the southeast waves predominate during the periods of monsoon transition (MT). Waves are stronger in monsoons than MTs, up to the strongest in winter monsoon and down to the weakest when winter goes to summer. (4) The driving contribution of local wind to waves in the BG increases gradually from the bay mouth to the inner bay, and the contribution is stronger in monsoons than MTs. The driving contribution of sea waves from SCS gradually weakens from the bay mouth to the inner bay, and the contribution is weaker during monsoons than MTs. In the middle and northern parts of BG, waves are mainly controlled by local wind. In the water areas to the south and east of Hainan Island, waves are mainly dominated by sea waves from SCS. While in the areas to the southwest of Hainan Island, waves are jointly affected by the both factors.

Tachypleus tridentatus has been upgraded to the State Key Protection Wildlife GradeⅡ in China in 2021. The population of T. tridentatus decreased sharply in recent years. T. tridentatus has become an endangered species. Based on the investigation of coastal wetlands along the Beibu Gulf coast, the resource data of major benthic species of each habitat is added, and niche width and niche overlap index analysis are used to explore the resource utilization of juvenile T. tridentatus and inter-species competition in this study, so as to further explore the competition between juvenile T. tridentatus and various species by using interspecific connectivity. The results show that: (1) juvenile T. tridentatus belongs to a wide niche species in the benthic community, and its niche width is the largest (4.252 2); (2) the niches of juvenile T. tridentatus and various benthos are ecologically partitioned with partial overlap, among which the niche overlap with Mictyris brevidactylus is as high as 0.8375; (3) the population dynamics simulation result of juvenile T. tridentatus and Mictyris brevidactylus shows that the population size displays an opposite trend between the two species in Xibeiling area and Sanniangwan area, and the reduction of natural supplement is an important factor that limits the population growth. The research shows that the juvenile T. tridentatus can be used as the indicator species to characterize the health of coastal wetland ecosystem. It is suggested to take juvenile T. tridentatus as the flagship species to carry out biodiversity conservation, management and publicity in coastal wetland.