17β-hydroxysteroid dehydrogenases (17β-HSDs) are the oxidoreductases in the last step of sex steroid hormone synthesis process, and play important roles in animal gonadal development and reproductive regulation. In this study, on the basis of the genome data of the razor clam Sinonovacula constricta, 17β-HSD genes were cloned and identified, and their chromosome distributions, phylogenetic relationships and gene expression patterns in different tissues and under different gonadal developmental stages were analyzed. The results showed that 17β-HSD6, 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes of S. constricta were located on four different chromosomes, and the encoded proteins all contained the conserved SDR superfamily domains. The four 17β-HSD proteins were clearly differentiated and clustered into four independent branches in the phylogenetic trees. The results of qRT-PCR showed that 17β-HSD genes were all expressed in testes tissues, and possessed higher expression levels in gonads and hepatopancreas. During the gonadal development of S. constricta, 17β-HSD6 gene was expressed higher in testis and ovary at the spawning stage. The expression levels of 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes showed a trend of increasing first and then decreasing during the development cycle of testis and ovary, which were all expressed higher at the mature stage. At the mature stage, 17β-HSD10 gene was expressed significantly higher in testis than in ovary (p < 0.05) , while the expression levels of 17β-HSD12 and 17β-HSD14 genes were all significantly higher in ovary than in testis (p < 0.05). Therefore, 17β-HSD6 gene might not be involved in regulating gonadal development process, while the expressions of 17β-HSD10, 17β-HSD12 and 17β-HSD14 genes were closely related to the gonadal development, suggesting that they might affect the gonadal development by regulating the synthesis and metabolism of sex steroid hormones in S. constricta. These findings laid theoretical foundations for further study on mechanism of 17β-HSD genes in regulating gonadal development and reproductive endocrine of mollusks.

Random errors between systems are not correlated is a necessary assumption for Triple Collocation (TC) analysis, but this assumption does not always hold in practice. The least squares-based Extended Collocation (EC) method can estimate random error in the presence of error correlation, but it cannot accurately estimate standard deviation (SD) of the random error as error correlation is weak. This paper proposes an error estimation method for the fourth system using three error-independent systems, which can estimate the SD of the system error more accurately in case of weak correlation by considering both error correlation and representative error. The SD of the errors of the scatterometer, radiometer and altimeter are 0.600 m/s, 0.742 m/s and 0.533 m/s respectively, as assumed that random errors of three HY-2B wind speed products are independent. The SD of error of ERA5 reanalysis wind speed is also estimated to be 0.810 m/s, the correlation coefficient of the errors of wind speed between HY-2B scatterometer and the ERA5 is 0.231, the correlation coefficient of the errors of wind speed between HY-2B radiometer and the ERA5 is 0.105. This paper proposes a method to estimate random errors and their correlation with the fourth dataset using three known error independent datasets, which achieves a more precise estimation for the SD of the random error in the case of weak correlation, and it helps to use these data better in assimilation and fusion.

Here, stable carbon and nitrogen isotope (δ¹³C and δ¹⁵N) techniques are used to estimate the trophic levels (TL) and main carbon sources of the dominant fish in the coral reefs of Weizhou Island in autumn. Combined with the six quantitative indicators of community trophic structure, the trophic relationship of the dominant fish in the coral reefs of Weizhou Island in autumn is preliminarily analyzed. The results show that the δ¹³C and δ¹⁵N values of different fishes are significantly different (p < 0.01). The δ¹³C values are between −18.3‰ and −15.4‰, and the δ¹⁵N values are between 12.9‰ and 16.3‰. The trophic levels of fish ranged from 2.5 to 3.4, with an average values of 3.0 ± 0.8, indicating that fish in Weizhou Island are mainly carnivorous. The organic carbon sources of fish in Weizhou Island are complex, but macroalgae and benthic microalgae are the key carbon sources fuelling fish food webs. The food source diversity level and trophic level length (CR and NR) of fish community are 2.35 and 3.09, respectively. The total area (TA), mean centrifugal distance (CD), mean nearest neighbor distance (MNND) and standard deviation of nearest neighbor distance (SDNND) are 4.48, 0.89, 0.40 and 0.29, respectively. These above indicators suggest that the trophic structure of coral reef fish community in Weizhou Island has a high degree of nutritional redundancy, but the food chain is short and the nutritional diversity is low. The coral reef ecosystem in Weizhou Island is incomplete in food web structure. In the future, it is necessary to carry out appropriate control and restoration measures to restore the structure and function of the coral reef ecosystem in Weizhou Island.

Based on the dataset of 120 water quality monitoring sites (including 16 coastal sites) in rivers along Liaodong Bay, the principal component analysis-multiple linear regression (PCA-MLR) model was used to study the pollution characteristics and flux of organic matter, nutrients and heavy metals, and analyze their possible sources. The pollutants exceeding the first grade of Environmental Quality Standards for Surface Water were COD_Mn, AN concentration. TP concentration and TN concentration, and other water quality parameters met the standard. The TN/TP ratios were high and seriously deviated from the Redfield ratio. The input of high N and low P load from terrestrial sources was the main factor causing the increase of TN/TP in Bohai Sea. DO concentration, EC, AN concentration and TN concentration in non-flood season increased significantly than in flood season, while pH, turbidity, COD_Mn and TP concentration in non-flood season decreased significantly than in flood season. The concentrations of organic matter and nutrients in estuaries were affected by factors such as the agricultural areas that rivers flowed, while the concentrations of heavy metals were related to the distribution of industrial enterprises in the region. The annual fluxes of TN, TP, COD, AN and petroleum pollutant into Liaodong Bay were 3.63 × 10⁴ t, 1 608.5 t, 14.8 ×10⁴ t, 3 086.6 t and 221.9 t, respectively, and the fluxes of Hg, Cd, Pb, As and Cr⁶⁺ were 0.264 t, 0.253 t, 1.978 t, 20.434 t and 31.651 t, respectively. According to their contribution, the main pollution sources were domestic sewage and industrial wastewater, sources caused by hydrological factors (hydrodynamic conditions, etc.), water-gas interface pollutants exchange and secondary sources, non-point sources of farmland runoff and transportation.

The maximum entropy model (Maxent) and habitat suitability index (HSI) model are widely used in fishery forecasting studies. To compare the forecasting performance of these two models on fishing grounds and improve the scientific management of chub mackerel (Scomber japonicus) resources, this study used the fishery data of chub mackerel in the East China Sea and Yellow Sea from 2003 to 2012, and marine environmental data, including sea surface temperature, sea surface height, sea surface salinity and sea surface temperature gradient, to construct the Maxent model and HSI model. The aim was to analyze and compare the effectiveness of these two models in predicting the habitat of chub mackerel in the East China Sea and Yellow Sea. The quantitative evaluation of the prediction performance of the two models was conducted using the area under curve (AUC) of the receiver operating characteristic (ROC), and the correspondence between the probability of fishing grounds predicted by the models and the percentage of the actual catches. The results showed that: (1) locations predicted by the maximum entropy model to have a high probability of fishing occurrence coincided with actual fishing locations. The probability of predicting fishery occurrence in the sea area without historical fishing data was lower. Locations predicted to have a high habitat index by the HSI model partially overlapped with actual fishing locations. A high habitat index was obtained in the sea area without historical fishing data. The probability of the HSI model predicting non-fishing grounds as fishing grounds was higher than that of the Maxent model; (2) the monthly average AUC values of the Maxent and HSI model were 0.95 and 0.66, respectively, indicating that the Maxent had relatively better predictive results; (3) when using the HSI model, non-fishing grounds data should be added to the model, and the collection of such data should be strengthened otherwise, there is a possibility of overestimation when such models forecast fishing grounds. When using the Maxent, the spatial coverage of fishery data must be improved otherwise, it cannot fully reflect the spatial and temporal distribution dynamics of the fishery. The results of this study provide a reference for improving the accuracy of forecasting for the chub mackerel fishery in the East China Sea and Yellow Sea.

Numerical simulation play an important role in studying long-term climate change. For a long time, it has meted great challenges in characterizing the phase transitions of interdecadal climate changes like Pacific Decadal Oscillation (PDO). This study evaluates 145-year (1870–2014) historical PDO simulation results produced by the First Institute of Oceanography’s Earth System Model Version 2 (FIO-ESM v2.0) of Ministry of Natural Resources, in a comparison with reanalysis datasets and two other earth system model results. Results indicate that the FIO-ESM v2.0 can recreate the spatial modal distribution characteristics of the PDO from the historical period. The model’s PDO index has a period of 10 to 30 years and can describe the phase transition characteristics that resembles reanalysis datasets after 1960. Research shows that the FIO-ESM v2.0 can describe the phase transition features of PDO well. In addition, the model performance to simulate atmospheric circulation modes and relationship with PDO, as well as the possible mechanism for the model to simulate PDO are also discussed. The PDO of the model is related to the Aleutian Mode of atmospheric circulation. Further analysis shows that advection and heat flux are the main factors affecting the amplitude of SST anomalies in key decadal area, and the Rossby wave westward time may be the key factor affecting the phase transition of PDO.

Diaphus is one of the genera with the highest species abundance and the most abundant population in the family Myctophidae, and it is also the dominant group of deep sea fishes in the ocean. However, due to the high similarity of external morphology, it is difficult to identify the lanternfish species. In order to explore the feasibility of otoliths morphological analysis in identifying the otolith differences between Diaphus species with similar otoliths and large overlapping distribution areas, the otoliths of three Diaphus species were collected from the Indian Ocean and the South China Sea for morphometrics analysis with landmark method. The results showed that the morphological variation of sagittal otoliths in three lanternfishes were mainly in the internal main sulcus, and the internal punctuation contribution rate reached 62%. The grid difference visualization showed that the wing length of sagittal otoliths in D. thiollierei was longer than that of the other two species, while the width was slightly narrower. The Bayes function was used for classification and discrimination, and the results showed that the success rate of D. thiollierei was 100%, while the other two species had a few misjudgments. In addition, taking into account the habitat environment and the genetic relationship between these three species, we supposed that the main reason for the morphological differences in the main sulcus of the three spescies was the huge salinity difference in the habitat sea area. However, the impact and physiological mechanism of salinity on the morphology of the main sulcus of sagittal otoliths needs to be further studied.

Study on the structure and energy flow of food webs is important for maintaining the stability of structure and function of marine ecosystems, which will contribute to the in-depth understanding of the complex processes of marine ecosystems. Based on the seasonal bottom trawl survey data in the northern waters of Jiangsu Province from 2019−2021, a linear inverse models using a Monte Carlo method coupled with Markov chain model combined with ecological network analysis (ENA) were used to explore the status of the ecosystem and energy flow characteristics of the food web in this area. The results showed that there were 299 energy flow paths in the ecosystem, which showed a typical pyramid structure. In addition, the energy consumed by respiration and the energy flowing into the detritus of each functional group remains synchronized. Compared with other sea areas, connectance (C) and system omnivory index (SOI) were 0.40 and 0.22, respectively, which were at relatively high levels, indicating that organisms from different trophic levels in this ecosystem were closely connected. It has a relatively complex food web structure, which can resist external disturbance. Total primary production/total respiration (TPP/TR) and Finn’s cycling index (FCI) were 1.05 and 5.76%, respectively, indicating that the ecosystem was relatively mature and used energy efficiently. In addition, constraint efficiency (CE), extent of development (AC), synergism index (b/c) and dominance indirect effects (i/d) also indicated high potential for development and regeneration. This study will provide a theoretical basis for the restoration and sustainable utilization of fishery resources in the northern waters of Jiangsu Povince, and provide a scientific basis for the implementation of Ecosystem-based fishery management in this area.

The inhomogeneity of the seawater medium causes the refraction effect in the sound wave propagation process. The ultra-short baseline system using the planar acoustic array will be affected by this phenomenon during the measurement process, which will cause large errors in the measurement results. The sound ray tracking method is usually used to correct the sound ray by using the measured sound velocity profile. Accurate beam incident angle is the prerequisite to ensure the accuracy of sound ray tracking, but the ultra-short baseline system does not directly measure the beam incident angle but uses the approximate incident angle derived from the acoustic phase difference for sound ray tracking will cause a certain loss of accuracy. To solve the above problems, this paper proposes an iterative correction method of beam incidence angle for ultra-short baseline underwater acoustic positioning. Based on constant gradient acoustic ray tracking, the iterative calculation relationship between beam incidence angle and propagation time is constructed, the Aitken acceleration method is used to quickly solve the nonlinear equation of the beam incidence angle. Simulation experiments prove that the method proposed in this paper can accurately calculate the beam incident angle and target position, and effectively eliminate the influence of refraction effects on ultra-short baseline underwater positioning.

Early melt onset (EMO) is a crucial time index for sea ice melting and has a significant impact on the thermal balance of sea ice. In this paper, EMO remote sensing, ERA5 reanalysis, and sea ice concentration data have been used to reveal the relative contribution of surface air temperature and liquid precipitation. Our research indicates that, the most significant advancement of EMO is observed in the southern Atlantic sector among the five study sea areas from 1979−2021, with the rate of −3.3 d/(10 a). For the atmospheric factors affecting EMO, surface air temperature has a considerable correlation period lasting 1−2 months with EMO in all Arctic sea areas. In addition, surface air temperature in the southern Pacific sector and northern and southern Atlantic sectors have a longer duration and stronger correlation with EMO than liquid precipitation. However, for the northern Pacific sector and the central Arctic, liquid precipitation has a higher contribution only in the 2−3 weeks prior to EMO. For the northern Pacific sector, atmospheric circulation provides strong water vapor transport channel extends into this sea area, increasing saturated water vapor in the lower troposphere. Meanwhile, the trend of the 500 hPa potential height shows a three-wave strengthening atmospheric circulation structure around the pole, allowing meridional heat exchange and enhancing the vertical gradient of specific humidity, which promotes the advancement of EMO. For the central Arctic, in years when EMO is advanced, the liquid precipitation is 33% higher than climatology. Additionally, not only the Pacific water vapor transport in the climatology is enhanced, but also the converges with water vapor channel over Eurasia continent, contributing to the formation of cyclonic water vapor transport mode in the eastern Arctic, providing conditions for the advancement of EMO.