When the wharf project of Tieshan Port in Beibu Gulf was constructed, nearby mangrove plants were damaged. A coupled model of hydrodynamic force and sedimentation in the gulf including mangrove intertidal zone based on remote sensing enhancement was built. Impacts of the wharf on the tide, sediment transport, erosion and deposition in the mangrove zone were evaluated. Results showed that the model can make full use of the tidal simulation information in the South China Sea and can finely simulate the sediment transport principle nearby the wharf. In association with information fusion technology of remote sensing inversion of the cover probability of global surface water and local tidal levels, elevation data in mangrove zone were reliably obtained. The tides mainly in the southern of the mangrove zone were influenced by the wharf. The velocity decreased at the most rising tide, and that in the tidal channel increased at the most ebb tide. When the way to the wharf was transferred using a steel trestle, the velocity in the southeast of the mangrove zone increased slightly. During the construction period of the wharf, the increase of suspended sediment concentration varied from 20 mg/L to 50 mg/L in the range of 69% and 72% of the mangrove zone. Before the wharf construction, the average sediment deposition in the mangrove zone accounted for 0.27 cm/a. For two designed ways to the wharf, i.e. the road isolating tide and the steel trestle allowing tide passing, the average deposition accounted for 0.45 cm/a and 0.36 cm/a with the range of 96.6% and 89.3% in the mangrove zone respectively. Provided that the steel trestle to the wharf would be selected, the average increment of the deposition in the mangrove zone decreased by 50%. The conclusions can provide the scientific basis for the simulation of tide and sedimentation in intertidal zone and the decision of the mangrove protection.

Transoceanic tsunamis can be guided by oceanic ridges and transferred large energy with slower velocity, hitting far-field regions and causing disaster effects. Therefore, the study on guided waves is crucial to improve the understanding of tsunami propagation characteristics. Based on the linear shallow water equation, the complete analytical solutions for guided waves over a parabolic symmetric ridge are derived. It is shown that both symmetric and anti-symmetric guided waves can exist along symmetric ridges and the free surface is described using the modified Bessel functions. Dispersion relationships, determining the relationship between the wave frequency and the wavenumber, are obtained from the continuity of water surface and velocity at the top of the ridge. The kinematic characteristics of guided waves, such as phase velocity, group velocity and surface spatial distribution are further revealed. This paper theoretically elaborates the guided waves over the ridge with its topographic slope generally increasing from the top to the bottom and provides the formulas to predicate the arrival time of the most threatening waves for the actual transoceanic tsunamis.

The Kyushu-Palau ridge (KPR) is an important part of the proto-Izu-Bonin-Mariana arc. The mineralogical and petrological studies of the arc basement rocks can provide significant insights for understanding the petrogenesis and magmatism characteristics of the early stage of intra-oceanic island arc evolution. In this paper, we performed petrographic and detailed mineral geochemical analyses including in situ major-trace elements of clinopyroxene (Cpx) phenocrysts and microcrystals from the basement basalts from the southern KPR. The results show that clinopyroxenes are mainly augites and diopside, which generally have similar chemical components for the phenocrysts and microcrystals. These clinopyroxenes are depleted in light rare earth elements with weak Eu negative anomalies. Most of the Cpx macrocrysts display zoning structures, which can be classified into basic and oscillatory zoning. The MgO, FeO, Al₂O₃, TiO₂ and Mg# contents show complex high-low variations from the pyroxene core to the rim, indicating multi-period magma mixing and replenishment events. The crystallization temperature and pressure of Cpx phenocrysts are 1 151−1210℃ and 1.3×10⁸−4.2×10⁸ Pa, respectively. In addition, the water content of parent magma obtained by the inversion calculated from Cpx components is 0.8%−2.3% (wet weight). Conclusively, we suggested that the parent magma of the southern KPR lavas that formed within a typical intra-oceanic island-arc setting is a sub-alkaline island-arc tholeiite basaltic melt with high temperature, medium pressure, and high oxygen fugacity. The magma chambers were shallow in depth and there existed multi-period replenishment and mixing of primitive magma.

Combined with hydrometeorological data, a six-day tracking survey was carried out in the coastal waters of Changhua Town, Changjiang County, western Hainan Island on March 10 to 15, 2022. And this study analyzed the variation characteristics of environmental factors and influencing factors in the process of Phaeocystis globose bloom. During the peak of the bloom, the abundance of Phaeocystis globosa and COD_Mn were as high as 3.10×10⁸ cells/L and 35 mg/L, which were much higher than those reported in other areas. The rainfall and wind wave disturbance before the bloom promoted the terrestrial runoff and the release of sedimentary nutrients, which provided material conditions for the bloom. The sudden rise of temperature induces the bloom, and the larger tidal range and lower wind speed create favorable external conditions for the accumulation along the colony. During the elimination of the bloom, the concentrations of DIN, PO₄-P, DO, COD_Mn and Mn decreased significantly, in which DIN and PO₄-P were the limiting factors, and DO, COD_Mn and Mn were important characteristic factors. After the yellow colony broken, the concentrations of Chl a and SiO₃-Si also decreased rapidly, and then slowly increased or even higher than the peak concentration level, when the diatom abundance represented by Chaetoceros curvisetus gradually increased. The study also preliminarily explores the basic generation and elimination process of the bloom, which provides an important reference for the further study of the bloom mechanism of P. globosa in this area.

Beibu Gulf is located in the northwestern part of the South China Sea and is experiencing a significant increase in the frequency, duration and extent of harmful algal blooms (HABs) outbreaks in the last 30 years. To characterize phytoplankton and bacterial communities during the massive Noctiluca scintillans bloom in the Beibu Gulf, seawater samples were collected from the area of a massive N. scintillans outbreak west from Weizhou Island on February 21, 2021, and environmental factors, along with phytoplankton and bacterial communities were analyzed. The results showed that the sea water quality of this area met the standards of Chinese Class I seawater quality, mainly in the absolute phosphate limit state. In recent years, other studies reported low nutrient content and limited phosphorus in waters adjacent to Weizhou Island and in the central part of Beibu Gulf during the non-harmful algal bloom (HAB) period. Therefore, N. scintillans bloom investigated in this study belonged to a non-eutrophication HAB event. Two phyla, five genera, and five species of phytoplankton were identified in seawater, among which N. scintillans was the absolute dominant species, with a cell density of 2.00×10³–3.75×10³ cells/L. The red discoloration of the sea water was caused by the red heterotrophic N. scintillans. Both phylogenetic and genetic distance analyses demonstrated that the causative N. scintillans in the Beibu Gulf was similar to N. scintillans along the coast of China. High-throughput sequencing of the V3–V4 region of the 16S rRNA gene in seawater samples revealed that the number of OTUs (operational taxonomic units) in bacterial community ranged from 294 to 414, with Alphaproteobacteria and Gammaproteobacteria as the dominant groups. The bacterial community structure was affected by various environmental factors, including COD, DO, DIN, ${\rm{PO}}_4^{3-} $-P, and N/P, among which COD was predominant. This research provides new insights into the environmental characteristics and microbial composition of sea water during a massive N. scintillans bloom and will aid bloom management in the Beibu Gulf.

Carrying out researches on marine sediments’ source can help to better understand the mechanism of material transport and the process of regional and global material circulation. A sediment provenance study has been conducted by analyzing the rare earth element and Sr-Nd isotopes of the ANT36-C4-05 core sediment in the Cosmonaut Sea, Antarctic. The results show that the average content of rare earth element (REE) in the sediment is relatively high, with an obvious fractionation between light REE (LREE) and heavy REE (HREE); and the average ⁸⁷Sr/⁸⁶Sr value of the sediment is relatively high, while the average εNd(0) value is significantly negative. The REE and Sr-Nd isotopic characteristics indicate that since the late Middle-Holocene, the sediment is mainly originated from high-grade metamorphic rocks in the vicinity of the Prydz Bay and Enderby Land, East Antarctic. These detrital materials are partly introduced into the Cosmonaut Sea under the ice-sea interaction, with the Antarctic Coastal Current and Antarctic Slope Current playing important roles in the transportation; simultaneously, it may also rely on katabatic winds originating from the Antarctic interior plateau to complete the transport process from source areas to the study area. The results of the provenance end member mixing model show that the sediment is mainly originated from metamorphic rocks in the Prydz Bay area (>70%), while the contribution from Enderby Land is relatively small. The significant difference in the contribution of two source areas is related to the differences in glaciers, ocean currents, and wind forces between two areas: compared to Enderby Land, the glacier in the Prydz Bay area is larger in scale and moves at a faster speed, with a stronger erosive and transport capacity for the bedrock; in the meanwhile, the Antarctic Bottom Water originating from the bottom of the Prydz Bay area may play an important role during the westward transportation; and the Prydz Bay area is one of the stronger wind force regions of katabatic winds, which can contribute more bedrock debris to downwind areas, for example the Cosmonaut Sea. These factors result in the characteristic of the ANT36-C4-05 core sediment in the Cosmonaut Sea which is mainly from the Prydz Bay area.

To identify abalone species effectively for better management and protection of abalone germplasm resources, we have obtained the complete mitochondrial genome of juvenile green abalone (Haliotis fulgens) through high-throughput sequencing, and its sequences and structural characteristics are analyzed accordingly. The results show that the mitogenome of H. fulgens is 17 041 bp in total length and encoded 37 genes, including 13 protein coding genes, 22 transfer RNA (tRNA) genes and 2 ribosomal RNA (rRNA) genes. The 13 protein coding genes used AUG as the starting codon and UAA or UAG as the termination codon. Twenty-one tRNA genes other than tRNA-Ser^(AGN) could be folded into a typical cloverleaf structure. There is a rich A+T non-coding region between tRNA-Glu and COX3, with two hairpin structures containing palindromes in it. A phylogenetic tree was constructed based on the reported complete mitochondrial genome sequences of Haliotis genus species, and phylogenetic analysis shows that H. fulgens is clustered with H. discus hannai, H. rufescens and H. cracherodii. Comparing the domains of 13 proteins of mitogenome of H. fulgens and H. discus hannai, we found the number of transmembrane domains of ND2 or ND4 dehydrogenase subunits were different in them. Whether this is related to the difference of high temperature tolerance between them needs further study. In brief, the first acquisition and analysis of the complete mitochondrial genome of H. fulgens has enriched the abalone cellular genetic information, and provided basic data and references for abalone species classification, germplasm identification, and protection of germplasm resources of H. fulgens as well.

Quantitative analysis on the properties of marine phytoplankton bloom events is helpful to understand the marine ecology, environment, and dynamic processes. In the South China Sea, remote sensing is vulnerable to clouds. Previous studies were mostly conducted with discontinuous observation or remote sensing data, which failed to comprehensively understand the characteristics and controlling factors of marine bloom events in the South China Sea. This study applied the statistical framework for defining marine heat waves, based on previously reconstructed daily full coverage remotely sensed chlorophyll a product from 2005 to 2019, to extract marine bloom events in two representative subregions, i.e., the northwestern Luzon in winter and southeastern Vietnam in summer. The duration, intensity, and corresponding long-term trends of marine bloom events in the two representative sea areas were analyzed. The results showed that the bloom frequency in the Luzon Strait has decreased, while the intensity has increased. These trends were significant in most areas for the winter Luzon Strait, while the trends for most of the summer Vietnam coasts were not significant. We further analyzed the influencing factors of marine bloom events and found that the winds (positive correlation) and sea surface temperature (negative correlation) had the greatest impacts on the bloom events. In both two representative sea areas, the marine bloom events were mainly dominated by upwelling, and the wind was the most important influencing factor. Analysis on the precursor conditions of marine bloom events found that the sub-mesoscale activity represented by the temperature front is also an important influencing factor. The study applied in South China Sea as a case study, as well can provide a new perspective to study marine ecosystem and environment.

Here we examine the history of sea ice activity recorded in the Core LV87-54-1 recovered from the northern Okhotsk Sea shelf using high-resolution grain-size analyses. We extracted 3 end members and use EM3 as the sea-ice proxy, using the program AnalySize to conduct end members analyses on the data. According to EM3 results, active sea ice was persistently predominant in the northern Okhotsk Sea shelf since the Last Glacial Maximum. The EM3 content was high and the sea ice activity was intense during the Last Glacial Maximum and Heinrich Stadial 1. The climate cooling at the middle and high latitudes of the Northern Hemisphere and the negative Arctic Oscillation were the main controlling mechanism for sea ice expansion during glacial periods. And weakened runoff from the Amur caused by decreased East Asian Summer Monsoon would allow more sea ice formation in the Okhotsk Sea. Sea ice formation decreased at the onset of the Bølling-Allerød warm period, and then decreased sharply after a slight peak during the Younger Dryas Event. EM3 levels remained low stably since the Holocene due to: increased local autumn insolation, positive Arctic Oscillation and enhanced East Asian Summer Monsoon suppresses subsequent sea ice formation.

Implementation of the artificial sandbar is a typical measure for the beach nourishment. Research on the morphological evolution of the artificial sandbar meets the important need for coastal protection and restoration. Domestic and international research on morphological evolution of nearshore artificial sandbar and underlying sediment transport mechanisms are summarized in this paper, focusing on the theoretical aspects, e.g. cross-shore migration, morphology evolution, morphology coupling and mechanisms of sediment transport of the artificial sandbar. In the methodology perspective, the description of the equilibrium profile and numerical modelling of morphology evolution of the artificial sandbar are also highlighted. It is also proposed that future research should focus on the deepening of mechanisms of key processes, the improvement of simulation and prediction methods and the application of practical beach nourishment projects.