The shoreline change is the most direct factor in studying landform erosion and deposition. The Huanghe River Delta is the world’s fastest-growing delta, and understanding its coastline changes and evolution trends is crucial to regional ecological environment protection, marine resource development, and infrastructure construction. In this study, we combined modified normalized difference water index (MNDWI) and multi-year water frequency index (MWFI) to analyze water quality in typical years from 1976 to 2021, based on previous research. We visually interpreted 207 remote sensing images to obtain an annual coastline that makes the obtained coastline more scientific and representative. We then analyzed the temporal and spatial evolution and stability characteristics of the coastline through quantitative calculations to explore the Qingshuigou sub-delta coastline of the Yellow River’s evolution mechanism since 1976. Our main findings are as follows: (1) In general, the evolution of Qingshuigou sub-delta coastline shows a trend of rapid sedimentation towards the sea, followed by fluctuations and stability. We can divide it into “rapid development” and “slow development,” with the “dynamic equilibrium” in between, taking 1996 and 2002 as nodes. (2) Over the past 45 years, the stability of the coastline in the study area has continued to increase. The coastline of the section of the coastline and the abandoned estuary section of Qingshuigou is relatively active, and its coastline stability index is generally lower than 0.5. (3) The migration of the sedimentation and erosion center of the land delta corresponds to the estuary location’s change, especially the migration of the sedimentation center, which has a positive relationship in the longitude direction between the change of the estuary position and the position of the estuary, R² = 0.690 4. (4) The Huanghe River’s sediment reduction into the sea, the relocation of the estuary position, and human activities have a significant impact on the delta coastline’s development and evolution. In the long run, the Huanghe River’s silt into the sea is still continuously reducing, and the future of the delta is still facing the threat of erosion.

Multispectral images are greatly affected by factors such as clouds, fog, and solar flares, which makes it difficult to automatically extract high-precision green tides under complex weather conditions. Based on the multi-spectral images of my country’s HY-1C/D satellite CZI payload, using data mining technology to explore the difference in data distribution between green tide areas and non-green tide areas, we propose a high-precision and fully automatic green tide extraction method , which can be applied to HY-1C/D CZI sensor data. First of all, the thick cloud area is removed by preliminary extraction rules to achieve preliminary classification. Then, the correctly classified green tide samples and non-green tide samples were used as positive and negative samples respectively, and these samples were used as experimental data to train the decision tree model, and the automatic extraction rules of green tide were obtained according to the model. Finally, 5 strategies for correcting misclassifications were designed to achieve fully automatic extraction of green tides. In order to verify the effectiveness of the method, we collected 25 images of the green tide outbreak period in the Yellow Sea in 2021 for automatic detection experiments, and compared the experimental results with traditional index methods (NDVI, VB-FAH) and deep learning methods (ResNet50, U-Net). The results showed that the method outperformed other methods in terms of accuracy, Kappa coefficient, F1-Score, and MIoU. The accuracy of green tide extraction was higher in areas with thick clouds, thin clouds, cloudless clouds, cloud spots, and flares.

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.

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.

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.

Nuclear factor κB (NF-κB) can regulate immunity, inflammation, apoptosis, cell proliferation, and organism development. At present, NF-κB has been well studied in vertebrates and fruit flies, while its role in shellfish is still elusive. In order to further explore the role of NF-κB in the immunity and development of mussel Mytilus coruscus, the full length McNF-κB cDNA sequence was cloned from M. coruscus. McNF-κB gene was 4087 bp long, and the open reading frame was 2 613 bp, encoding 871 amino acids and had a typical ankyrinrepeat (ANK) domain and DEATH domain. The results of amino acid sequence analysis showed that the gene had 72.76% homology with M. edulis and 66.58% with M. galloprovincialis, respectively, and was clustered with M. edulis and M. galloprovincialis in the phylogenetic tree. The real-time PCR (qRT-PCR) technology showed that the McNF-κB gene was expressed distributed in all tissues of M. coruscus, and the expression was the highest in the gill. McNF-κB gene was expressed in both the pediveliger larvae stage and the juvenile stage of M. coruscus, and the expression was significantly higher in the pediveliger larvae stage than that in the juvenile stage. After using RNA interference technology to silence the McNF-κB gene of pediveliger larvae, the larval metamorphosis rate decreased significantly, indicating that this gene was involved in regulating the metamorphosis process of M. coruscus. This study provides a basis for exploring how McNF-κB gene regulates development of M. coruscus.

Many of the global ecosystem functions are changing with the loss of biodiversity. It is therefore particularly important to understand the biodiversity-ecosystem functioning (BEF) relationships to support scientific ecological conservation and management. In this study, we evaluated the relationship between environmental factors, biodiversity (species richness and evenness) and ecosystem functions (measured as total biomass) in the benthic fish community of Haizhou Bay, using structural equation modeling (SEM) based on bottom trawl survey data conducted in spring 2013−2022. The results showed that there was a significant positive correlation between species richness and biomass, and a significant negative correlation between evenness and biomass. Among the environmental factors, salinity had significant effects on both species richness and biomass. Regarding the effects of temperature, the temperatures in winter and summer had a stronger effect on biomass than that of annual average temperature. The study suggested that two mechanisms, the niche complementarity mechanism and selection mechanism, may simultaneously play a role in maintaining the biodiversity-biomass relationships in the groundfish communities of Haizhou Bay, and in addition to the fact that such relationships depend on the environmental and habitat conditions.

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.

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.