Swordfish (Xiphias gladius) is a highly migratory fish whose habitat suitability is significantly influenced by the marine environment, and the prediction of its habitat using changes in the marine environment is of great scientific importance. In this study, we used the catch information of swordfish in the Chinese Indian Ocean Longline Fisheries Observer Data from 2017 to 2019 as species occurrence data, combined with the environmental data in the western Indian Ocean waters, including sea surface temperature (SST), sea surface height (SSH), chlorophyll a (Chl a) concentration, mixed layer depth (MLD), and sea surface salinity (SSS), the habitat suitability distribution of swordfish in the western Indian Ocean is simulated by using a maximum entropy model (MaxEnt). Model results show that: (1) the model has very high accuracy in simulating the habitat suitability distribution of swordfish in the western Indian Ocean, with AUC values greater than 0.9 in all seasons, and can be used to simulate the potential habitat suitability distribution of swordfish; (2) changes in the distribution of suitable habitat for swordfish in the study area are generally consistent with changes in the actual operational location, and the distribution of areas with high habitat suitability for swordfish is more concentrated in both the dry and rainy seasons, but the distribution range is greater in the wet season than in the dry season; (3) SST, SSS and MLD are important environmental factors affecting the habitat suitability distribution of swordfish in the western Indian Ocean. The optimum ranges of SST, SSS and MLD in the dry and rainy seasons are 25.8−31.6°C, 34.4−35.9 and 0.1−24.9 m, and 25.6−30.5°C, 34.8−36.4 and 13.1−54.1 m, respectively. The results of the study provide essential reference information for the sustainable use and scientific management of swordfish populations in the western Indian Ocean.

Marine sediments are characterized by soft texture and low strength, and their strength parameters are closely related to offshore platform pile placement and jacket installation, and are closely related to offshore operation safety. Conventional methods for obtaining strength parameters, such as drilling and cone penetration test, have high cost, few sampling points, and great disturbance to the soil. Therefore, it is of great significance to predict the strength parameters of marine sediments with easily accessible acoustic data. Based on the acoustic propagation theories such as Wood equation, Biot-Stoll model and Dvorkin equivalent medium model, the theoretical P-wave velocity under different physical parameter (density, porosity) gradients was calculated. Combined with the indoor simulated stratum acoustic experiment, the variation characteristics of the calculated and measured sound velocity were compared, and the relationship model between sound velocity and physical parameter was established. The relationship between soil physical parameter and shear strength, cohesive force and other parameters was revealed based on laboratory geotechnical test, and the relationship model between soil physical parameter and strength parameters was established. A prediction model for strength parameters of marine sediments based on acoustic characteristics was established by using physical parameters as bridge. This model not only avoids the problem of water loss disturbance of in-situ sampled soil, but also makes up for the limitation of empirical formula. It has universality and accuracy, and can effectively improve the precision of strength parameters of soil in unsampled areas, improve economic benefits, and play a theoretical guiding role in shallow exploration and development.

As an important part of monitoring oceanic phenomenon, it is essential to calibrate altimeter sea level height data. In 2020, the Haiyang-2C (HY-2C) satellite was sent to orbit as a follow-up mission of the HY-2B satellite. However, the quality of HY-2C sea level height is not fully known yet. In this paper, the quality and accuracy of HY-2C sensor geophysical data records (SGDR) of the latest version were assessed through the comparison with the HY-2B geophysical data records (GDR) and Jason-3 GDR measured at the same time. According to the results: self-crossover points analysis is carried out by star cross calibration of HY-2C satellite. The quality analysis results of sea level anomaly data of HY-2C SGDR are different. Through the comparison results, the optimal cubic spline interpolation method has the best quality analysis performance, with mean value is 0.03 cm and the standard deviation is 6.17 cm. The mean and standard deviation of sea level anomaly at the dual-crossing calibration of HY-2C and HY-2B satellites are −0.47 cm and 5.32 cm. The mean and standard deviation of sea level anomaly at the intersection of HY-2C and Jason-3 satellites are −0.3 cm and 5.32 cm. These results show that HY-2C has the same precision as HY-2B satellite and Jason-3 satellite. Data quality of HY-2C satellite is enough to meet the requirements of marine scientific research and application.

Estuarine flow is the fundamental driving of physical processes such as estuarine ecological environment, river evolution and material transport. Due to the runoff, tide, topography and meteorology, the estuarine flow presents a complex three-dimensional structure, including not only the residual flow induced by fresh water injection, but also the periodical tidal current, wind-driven flow, baroclinic flow and the residual flow caused by estuarine nonlinearity. In order to explore the composition and intra-tidal variation of estuarine flow, based on the field data in the Oujiang River Estuary, the estuarine flow is decomposed by principal component analysis (PCA) method, and the decomposition performance of PCA method for estuarine flow and high-frequency characteristics of baroclinic overtide are deeply discussed. The results show that PCA method can operate original data or standardized data in the study of estuarine flow structure. PCA method can decompose baroclinic components (estuarine gravitational circulation structure), but cannot separate barotropic components (runoff and tidal current). The coupled effect of runoff and tidal current is reflected in the score of principal components. The filter of principal components should employ conjoint judgment of flow structure and cumulative interpretation variance, rather than only cumulative interpretation variance. The estuarine baroclinic flow has clearly high-frequency characteristics, which approximates quarter-diurnal.

Insulin-like growth factors (IGFs) are key regulators downstream of the growth axis and play an important role in promoting cell differentiation and growth. In order to further study the expression mechanism and possible roles of IGF-1 and IGF-2 genes in the embryonic development of Acanthopagrus latus. Our research cloned and identified the cDNA sequence of IGF-2 gene from A. latus and proceeded a biological information analysis. At the same time, based on the foundation of continual observation of the embryonic development of A. latus. RT-qPCR was carried out to explore the expression levels of IGF-1 and IGF-2 genes. The results suggested that the full length and open reading frame of IGF-2 gene are 1 736 bp and 648 bp respectively, encoding a predicted peptide of 215 amino acids. Multiple alignment showed that A. latus IGF-2 was 99.95% similar to Sparus aurata and 98.14% similarity with Pagrus auriga, as well as relatively high homology with other teleosts, indicating that conservation of IGF-2 in teleost evolutionary relationships. Through continuous observation of the embryonic development of A. latus, it was found that under the conditions of water temperature of (26.5±0.5)℃, pH of 8.0 and salinity of 28, the time from fertilization of egg to hatching of membrane of A. latus was 25.5 h. Expression analysis showed that IGF-1 and IGF-2 genes constitutively expresses in various tested stages of embryo of A. latus. The expression of IGF-1 gene showed a trend of first increasing and then decreasing, reaching a relatively high expression in the muscle effect period, and the expression of IGF-2 gene showed a trend of first increasing and then decreasing and then increasing, IGF-2 gene was expressed in the gastrula stage, the muscle effect stage and 3 days after membrane emergence. Summarizing, all the data of our study above showed that IGF-1 and IGF-2 genes may play a crucial role in embryonic development in A. latus.

Characteristics of heavy metals in the Zhujiang River Estuary are mainly influenced by the interacting river-tide dynamics. Water and sediment samples were collected in the Zhujiang River Estuary and its adjacent zones in the summer of 2018. The present study aimed to investigate the estuarine behaviors (i.e., sedimentary, transportation, accumulation) of seven metals Hg, As, Zn, Cd, Pb, Cu, and Cr, which were co-influenced by the physicochemical properties in the estuary. The levels of heavy metals in sediments were higher than those dissolved in water. The heavy metals in sediments were more stable and the pollution was thus more serious. The results of Pearson correlation and principal component analysis showed that dissolved metals were more easily diluted and mixed, and the sediment metals were significantly influenced by the total organic carbon and redox. The metal partitioning between sediments and water was discussed as well in this study under the influence of estuarine dynamics, which indicated the phase exchange between multimedia in the estuary; Pb and Cr were more easily absorbed in the particulate particles, while Cd and Hg were intended to dissolve in water. The significant correlations between metals (e.g., Hg, Pb, and Zn) indicated the similar sources, and the principal component analysis was used to probe into the source contributions of heavy metals in sediments of the Zhujiang River Estuary, contributed mainly by industrial pollution, followed by agricultural pollution and atmospheric deposition. These findings will provide important information for the effective controls of heavy metal inputs and estuary management.

Based on the Earth System Model (ESM2M) of the Coupled Model Intercomparison Project 5 (CMIP5), combined with Argo observation data and the reanalysis dataset compiled by Ishii et al., this paper presents the seasonal variation characteristics of mixed layer depth (MLD) and subduction process in the subtropical Northeast Pacific Ocean (10°−40°N, 110°−160°W) under the present climate background and extreme enhancement of radiative forcing are presented, to study its response to global warming. Under the current climate background, both of MLD and subduction rate reach their maximum values in winter. The main contribution items of subduction rate have significant seasonal variation. From January to May, the subduction rate is mainly controlled by the change of lateral induction rate, while from June to December, the main mechanism is the change of Ekman pumping velocity controlled by wind stress curl. After global warming, the main control elements of seasonal signals remain unchanged. However, under the influences of wind stress curl and other factors, the MLD in each season decreased and the range of the core maximum region shrinks. As the decrease in winter is much larger than that in summer, the seasonal fluctuation range (amplitude) of MLD is significantly smaller. In the long run, MLD shows a trend of continuous shallower, and the weakening of MLD front caused by the weakening of its spatial non-uniformity is the key to control the weakening of lateral induction rate and eventually lead to the weakening of the subduction rate. Since the seasonal variation signal of Ekman pumping velocity has little response to global warming, subduction rate is most strongly affected in winter. The results show that the contribution proportion of the two key factors to the subduction rate changes with the seasons: when the MLD front is strong in winter, the influence of the lateral induction rate will be significantly enhanced. The different variations of the two factors before and after global warming will significantly change the seasonal amplitude of the subduction rate, which may have a profound impact on the formation and transport of mode water in the region.

A three-dimensional non-hydrostatic model based on volumed-averaged, Reynolds-averaged Navier-Stokes (VARANS) equations in sigma coordinate, is applied to simulate the propagation process of irregular wave over a typical fringing coral reef profile, with emphasis on the changes of wave height and wave setup on the reef flat. Compared with the laboratory measured data of several groups of wave and water level parameters, the model is shown to be capable of simulating well the wave transformation over the reef profile with and without porous media. Across all cases, the porous cases decrease the wave height by 12% around the breaking point, and by 28% on the reef flat than the smooth cases. As for the mean water level, the results show that the maximum setdown decreases by 43% on average for the porous cases than the smooth cases, while the wave setup on the reef flat for corresponding porous and smooth simulations is found to agree with an average difference of only 6%. In addition, the variation of porosity in the range 0.47−0.87 auses little effect on the wave setup.

In October 2020, we sampled the benthic ciliate communities in 14 sandy intertidal zones in northern China to gain insight into the relative influence of diverse geographical scale parameters on driving the spatial pattern of microbial communities. The main findings were as follow: (1) 105 ciliates were identified belonging to 65 genera and 26 orders, and Pleuronematida, Microthoracida, and Cyclotrichida were the dominant groups; (2) although significant differences in environmental conditions were detected between the Yellow Sea and the Bohai Sea, the community composition of ciliates did not show significant difference; (3) partial Mental test revealed that environmental factors were more important than spatial distance in determining ciliate community composition, with salinity, grain size, and beach slope were the most important environmental factors in explaining ciliate spatial distribution, while tidal range and dissolved inorganic nitrogen content were less important; (4) in coastal areas, the mass effect of microorganisms somewhat hided the effects of environmental heterogeneity. In conclusion, because microorganisms in coastal environments were less restricted by dispersal, environmental variables played a larger role in the establishment of spatial distribution patterns than spatial distance. This research gives basic information on marine microbial biogeography, which can aid beach management and conservation planning in the face of global change.

Depositional characteristics and process of deep-water channel sedimentary system influenced by contour currents is a current hotspot and new scientific issue in the study of deposits resulted from interaction between contour currents and turbidity flows. Using root mean square (RMS) attribute, coherenceseismic attribute, time structure and stratal slice, we focus on depositional characteristics and process of the channel sedimentary system in Pliocene strata in the Beijiao Sag, Qiongdongnan Basin. The results show that the channel sedimentary systems are divided into the early and late channel sedimentary systems. The depositonal units of the early system include channel, flake-shaped and fan-shaped overbank deposits. The units of the late systems incorporate: channel and flank-shaped overbank deposits. Fan-shaped overbank deposits are only distributed on the right side of the bend of the channel. Flake-shaped overbank deposits are only located on the left side of the channel. The channels are persistently oblique to the strike of the slope and they are symmetrical and characterized by vertical aggradations. Combined with the development features of mounded drifts and moats over the Beijiao uplift, it is inferred that the geometry of the channel sedimentary systems are mainly controlled by depositional products of the interaction between turbidity flows and contour currents. Contour currents flow across channels, forcing the upper part (low velocity and low density) of turbidity flows to deflect towards the left (downstream) side of channels and then form overspill currents. The direction of overspills is the same to that of contour currents, in this case, generating wide flake-shaped overbank deposits extending for several kmlometers. In the bend of channels, the direction of overspill currents is in contrast to that of contour currents, blocking or confining the range of the overbank deposits and then creating fan-shaped overbank deposits. This result are consistent with the previous results of flume-tank experiment.