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Biological monitoring of marine microplastic pollution based on mussel indicator is a monitoring method with broad application prospects. However, the current pretreatment process includes a variety of mussel tissue digestion and microplastic density separation technologies, and the scientific nature of pretreatment technology has yet to be verified, which makes it difficult to guarantee the accuracy of marine microplastic pollution monitoring results obtained by this method and the data are difficult to compare. In order to comprehensively evaluate the accuracy of multiple mussel tissue digestion and microplastic density separation operations and to obtain a cost-effective and reliable pretreatment technology, comparison tests of 4 common digestion methods (mixed acid digestion, potassium hydroxide digestion, Fenton digestion and protease K digestion) and density separation tests of 3 microplastic flotation fluids (sodium chloride saturated solution, sodium iodide saturated solution and potassium formate saturated solution) were carried out. The effects of different digestion methods on the digestion efficiency of mussel tissue and on the morphology, spectral characteristics and recovery rate of common microplastic in the ocean, as well as the separation effect of microplastic in different flotation fluids were evaluated, and the digestion conditions were optimized by single factor and response surface tests. The results showed that the Fenton digestion method had both efficient digestion of mussel tissue and low destructive effect on microplastic, and could be used as the optimal method for digestion of mussel tissue. After optimization, under the conditions of H2O2 (30%) volume 40 mL, Fe2+ concentration 0.020 mol/L, temperature 59℃, pH 3.7 and digestion time 24 h, the digestion rate of 10 g mussel tissue reached 96.7%. At the same time, this study confirmed that potassium formate saturated solution could replace sodium chloride and sodium iodide saturated solution as the flotation fluid with high efficiency. The development of the above research provides a reference for the improvement and standardization of the pretreatment technology for biological monitoring of marine microplastic pollution based on mussel indicator.
Biological monitoring of marine microplastic pollution based on mussel indicator is a monitoring method with broad application prospects. However, the current pretreatment process includes a variety of mussel tissue digestion and microplastic density separation technologies, and the scientific nature of pretreatment technology has yet to be verified, which makes it difficult to guarantee the accuracy of marine microplastic pollution monitoring results obtained by this method and the data are difficult to compare. In order to comprehensively evaluate the accuracy of multiple mussel tissue digestion and microplastic density separation operations and to obtain a cost-effective and reliable pretreatment technology, comparison tests of 4 common digestion methods (mixed acid digestion, potassium hydroxide digestion, Fenton digestion and protease K digestion) and density separation tests of 3 microplastic flotation fluids (sodium chloride saturated solution, sodium iodide saturated solution and potassium formate saturated solution) were carried out. The effects of different digestion methods on the digestion efficiency of mussel tissue and on the morphology, spectral characteristics and recovery rate of common microplastic in the ocean, as well as the separation effect of microplastic in different flotation fluids were evaluated, and the digestion conditions were optimized by single factor and response surface tests. The results showed that the Fenton digestion method had both efficient digestion of mussel tissue and low destructive effect on microplastic, and could be used as the optimal method for digestion of mussel tissue. After optimization, under the conditions of H2O2 (30%) volume 40 mL, Fe2+ concentration 0.020 mol/L, temperature 59℃, pH 3.7 and digestion time 24 h, the digestion rate of 10 g mussel tissue reached 96.7%. At the same time, this study confirmed that potassium formate saturated solution could replace sodium chloride and sodium iodide saturated solution as the flotation fluid with high efficiency. The development of the above research provides a reference for the improvement and standardization of the pretreatment technology for biological monitoring of marine microplastic pollution based on mussel indicator.
, Available online ,
doi: 10.12284/hyxb2024128
Abstract:
Sargassum horneri has good economic traits and value, and its culture is gradually being emphasized. However, the suitable water depth for culture is still unclear, and the physiological characteristics and ecological functions of Culex pipiens in different water depths are not clear. In this paper, we compared the primary productivity, nutrient uptake capacity, and algal trophic composition of S. horneri at different water depths (0.5 m and 2 m) based on light intensity in different water depths. The results showed that light intensity varied significantly (P < 0.05) with water depths and that the difference in light intensity due to water depth was significantly correlated with the primary productivity of S. horneri. The total productivity of S. horneri grown at 0.5 m water depth (upper layer) was significantly higher than that of S. horneri grown at 2 m water depth (lower layer) (P < 0.05), and S. horneri in the upper layer showed higher primary productivity and carbon sequestration capacity. The uptake of \begin{document}${{\rm {NH}}_4^+} $\end{document} ![]()
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, Available online ,
doi: 10.12284/hyxb2024132
Abstract:
In response to contingencies that arise during the underwater coverage missions of multiple autonomous underwater vehicles (AUVs), this study addresses the problem of coverage path replanning for multiple AUVs. A multi-robot multi-regional coverage path planning (M2CPP) method is proposed to reassign uncovered areas to available AUVs and plan their coverage paths. Initially, the lawnmower algorithm is employed to determine the internal paths and candidate entry points within each region. Subsequently, a coevolutionary approach is utilized to solve for the optimal region allocation, region sequence, and the best entry points for each region. Three populations coevolve collaboratively to determine the complete paths for all AUVs, ensuring population diversity and preventing convergence into local optima. Simulation results demonstrate that the proposed method not only replans shorter paths for multiple AUVs based on their initial positions and remaining energy but also optimizes the path structure to ensure a balanced workload among the AUVs, effectively resolving the replanning issue under such scenarios.
In response to contingencies that arise during the underwater coverage missions of multiple autonomous underwater vehicles (AUVs), this study addresses the problem of coverage path replanning for multiple AUVs. A multi-robot multi-regional coverage path planning (M2CPP) method is proposed to reassign uncovered areas to available AUVs and plan their coverage paths. Initially, the lawnmower algorithm is employed to determine the internal paths and candidate entry points within each region. Subsequently, a coevolutionary approach is utilized to solve for the optimal region allocation, region sequence, and the best entry points for each region. Three populations coevolve collaboratively to determine the complete paths for all AUVs, ensuring population diversity and preventing convergence into local optima. Simulation results demonstrate that the proposed method not only replans shorter paths for multiple AUVs based on their initial positions and remaining energy but also optimizes the path structure to ensure a balanced workload among the AUVs, effectively resolving the replanning issue under such scenarios.
, Available online ,
doi: 10.12284/hyxb2024120
Abstract:
During June 9th to 15th in 2017, the dynamic of Gymnodinium catenatum bloom along the coast of Hui’an County Fujian Province, were investigated. Six monitoring stations were established for marine environmental factors assessment over seven sampling trips. The water quality data from June 6th, along with the phytoplankton data collected in March and November 2017, was selected for comparative analysis. Furthermore, the survey results of dinoflagellate cysts and paralytic shellfish poison (PSP) in cultured shellfish were integrated to explore the relationship between dormant cysts and the bloom dynamics, as well as the patterns of PSP accumulation and elimination in cultured shellfish. The results revealed that during the bloom, conditions were characterized by sunny weather and favorable sea states, with water temperature ranging from 24.2℃ to 26.8℃ and the salinity between 30.4 and 33.2. The concentrations of nutrients were low, indicating oligotrophic conditions, while the density of G. catenatum peaked at 1.79×106 cells/L during the bloom period. The interplay of favorable hydro-meteorological conditions, N/P ratio and the trophic pattern of G. catenatum provided a basis for the evolution of the bloom, whereas adverse weather conditions primarily contributed to its decline. The average density of G. catenatum cysts in the surveyed sea area was 33.2 cysts/g, suggesting potential for these cysts to germinate into trophic cells, which could lead to the reemergence of the bloom and therefore it necessitates further attention. During the bloom period, both oysters and mussels rapidly accumulated high concentrations of PSP toxins, with levels directly proportional to G. catenatum density. Additionally, even low densities of G. catenatum posed a risk for PSP exceedances. Mussels exhibited a rapid accumulation and slow elimination of PSP, with a significantly greater capacity for toxin accumulation compared to oysters, while their elimination rate was significantly slower.
During June 9th to 15th in 2017, the dynamic of Gymnodinium catenatum bloom along the coast of Hui’an County Fujian Province, were investigated. Six monitoring stations were established for marine environmental factors assessment over seven sampling trips. The water quality data from June 6th, along with the phytoplankton data collected in March and November 2017, was selected for comparative analysis. Furthermore, the survey results of dinoflagellate cysts and paralytic shellfish poison (PSP) in cultured shellfish were integrated to explore the relationship between dormant cysts and the bloom dynamics, as well as the patterns of PSP accumulation and elimination in cultured shellfish. The results revealed that during the bloom, conditions were characterized by sunny weather and favorable sea states, with water temperature ranging from 24.2℃ to 26.8℃ and the salinity between 30.4 and 33.2. The concentrations of nutrients were low, indicating oligotrophic conditions, while the density of G. catenatum peaked at 1.79×106 cells/L during the bloom period. The interplay of favorable hydro-meteorological conditions, N/P ratio and the trophic pattern of G. catenatum provided a basis for the evolution of the bloom, whereas adverse weather conditions primarily contributed to its decline. The average density of G. catenatum cysts in the surveyed sea area was 33.2 cysts/g, suggesting potential for these cysts to germinate into trophic cells, which could lead to the reemergence of the bloom and therefore it necessitates further attention. During the bloom period, both oysters and mussels rapidly accumulated high concentrations of PSP toxins, with levels directly proportional to G. catenatum density. Additionally, even low densities of G. catenatum posed a risk for PSP exceedances. Mussels exhibited a rapid accumulation and slow elimination of PSP, with a significantly greater capacity for toxin accumulation compared to oysters, while their elimination rate was significantly slower.
, Available online ,
doi: 10.12284/hyxb2024118
Abstract:
In November 2020, sediment samples were collected from the Yalong Bay Qingmei Port mangrove nature reserve and the Sanya River mangrove nature reserve in Hainan Province. The present study focused on the community characteristics of marine nematodes and their influencing factors in these two mangroves. The results of the present study showed that the average abundance of marine nematodes was (80.4 ± 40.3) ind./cm2 in the Qingmei Port mangrove, while it was (96.7 ± 55.6) ind./cm2 in the Sanya River mangrove. In this study, the average abundance of marine nematodes in the two study mangrove wetlands was (88.5 ± 47.1) ind./cm2. There were significant differences in the abundance of marine nematodes between the two mangrove wetlands. A total of 77 species of marine nematodes were identified, belonging to 56 genera, 21 families and 7 orders. The dominant genera in the Qingmei Port mangrove were Neochromadora, Terschellingia, Paramonohystera, Daptonema, and Desmodora, and epigrowth feeders were the dominant feeding type. The dominant genera in the Sanya River mangrove were Terschellingia, Sabatieria, Eleutherolaimus, Parodontophora and Ptycholaimellus, and the selective deposit feeders dominated. Terschellingia dominated in both mangroves. There were spatial differences in the community structure of marine nematodes in study mangroves. Although the marine nematode communities differentiated between the two mangroves, the difference was not significant. Organic matter content and phaeophorbide content in sediments were important factors affecting the abundance and community structure of marine nematodes in Sanya River mangrove. The differences in mangrove vegetation types may affect the abundance and community structure of marine nematodes in Qingmei Port mangrove to some extent. The differences of sediment granularity characteristics, seawater pH and salinity could explain the differentiation of marine nematode communities at selected sites of the two mangrove. In addition, there are sewage project, port construction and tourism development in Qingmei Port mangrove, and felling, dike construction, salt pan development and wastewater discharge from shrimp ponds in Sanya River mangrove. The different pollution status in these two mangroves may also be the reason for the differences in the abundance and community structure of marine nematodes in this study.
In November 2020, sediment samples were collected from the Yalong Bay Qingmei Port mangrove nature reserve and the Sanya River mangrove nature reserve in Hainan Province. The present study focused on the community characteristics of marine nematodes and their influencing factors in these two mangroves. The results of the present study showed that the average abundance of marine nematodes was (80.4 ± 40.3) ind./cm2 in the Qingmei Port mangrove, while it was (96.7 ± 55.6) ind./cm2 in the Sanya River mangrove. In this study, the average abundance of marine nematodes in the two study mangrove wetlands was (88.5 ± 47.1) ind./cm2. There were significant differences in the abundance of marine nematodes between the two mangrove wetlands. A total of 77 species of marine nematodes were identified, belonging to 56 genera, 21 families and 7 orders. The dominant genera in the Qingmei Port mangrove were Neochromadora, Terschellingia, Paramonohystera, Daptonema, and Desmodora, and epigrowth feeders were the dominant feeding type. The dominant genera in the Sanya River mangrove were Terschellingia, Sabatieria, Eleutherolaimus, Parodontophora and Ptycholaimellus, and the selective deposit feeders dominated. Terschellingia dominated in both mangroves. There were spatial differences in the community structure of marine nematodes in study mangroves. Although the marine nematode communities differentiated between the two mangroves, the difference was not significant. Organic matter content and phaeophorbide content in sediments were important factors affecting the abundance and community structure of marine nematodes in Sanya River mangrove. The differences in mangrove vegetation types may affect the abundance and community structure of marine nematodes in Qingmei Port mangrove to some extent. The differences of sediment granularity characteristics, seawater pH and salinity could explain the differentiation of marine nematode communities at selected sites of the two mangrove. In addition, there are sewage project, port construction and tourism development in Qingmei Port mangrove, and felling, dike construction, salt pan development and wastewater discharge from shrimp ponds in Sanya River mangrove. The different pollution status in these two mangroves may also be the reason for the differences in the abundance and community structure of marine nematodes in this study.
, Available online ,
doi: 10.12284/hyxb2024122
Abstract:
The tidal creek system is an active geomorphic unit in coastal wetlands, and the water environment of different level tidal creeks changes significantly, leading to spatial distribution differences of biological communities. This study selected a typical tidal creek unit in the Huanghe River Delta and used environmental DNA metabarcoding (eDNA) technique to detect the diversity of invertebrates. The biological co-occurrence network analysis was used to reveal the key species and driving factors of invertebrates in the typical tidal creek. The results showed that a total of 127 operational taxonomic units (OTUs) of invertebrates were detected in the tidal creek unit, belonging to 9 phyla, 24 classes, 53 orders, 103 families, 87 genera, and 90 species; among them, the class level was dominated by the Arthropoda (43.9%), and the genus level was dominated by the Perinereis (25.2%). The comprehensive diversity index (CD) analysis showed that the comprehensive diversity of invertebrates in the third-level tidal creek was the highest, and the comprehensive diversity of invertebrates in the first-level tidal creek was the lowest. The biological co-occurrence network analysis showed that the Perinereis linea and the Obelia dichotoma were the keystone species, which played a key role in maintaining the stability of the invertebrate community structure in the tidal creek. The RDA showed that the silicate content of the water body, temperature, and the proportion of fine sand and clay in the sediment were the main environmental factors affecting the invertebrate community characteristics in the tidal creek. Correlation network analysis showed that the keystone species were significantly affected by silicate content, clay, and nitrogen content in water (P < 0.05). The research results are helpful for understanding the community structure of typical tidal ditch invertebrates, revealing the keystone species of typical tidal ditch invertebrates, and providing data support and theoretical reference for the monitoring and protection of invertebrate diversity.
The tidal creek system is an active geomorphic unit in coastal wetlands, and the water environment of different level tidal creeks changes significantly, leading to spatial distribution differences of biological communities. This study selected a typical tidal creek unit in the Huanghe River Delta and used environmental DNA metabarcoding (eDNA) technique to detect the diversity of invertebrates. The biological co-occurrence network analysis was used to reveal the key species and driving factors of invertebrates in the typical tidal creek. The results showed that a total of 127 operational taxonomic units (OTUs) of invertebrates were detected in the tidal creek unit, belonging to 9 phyla, 24 classes, 53 orders, 103 families, 87 genera, and 90 species; among them, the class level was dominated by the Arthropoda (43.9%), and the genus level was dominated by the Perinereis (25.2%). The comprehensive diversity index (CD) analysis showed that the comprehensive diversity of invertebrates in the third-level tidal creek was the highest, and the comprehensive diversity of invertebrates in the first-level tidal creek was the lowest. The biological co-occurrence network analysis showed that the Perinereis linea and the Obelia dichotoma were the keystone species, which played a key role in maintaining the stability of the invertebrate community structure in the tidal creek. The RDA showed that the silicate content of the water body, temperature, and the proportion of fine sand and clay in the sediment were the main environmental factors affecting the invertebrate community characteristics in the tidal creek. Correlation network analysis showed that the keystone species were significantly affected by silicate content, clay, and nitrogen content in water (P < 0.05). The research results are helpful for understanding the community structure of typical tidal ditch invertebrates, revealing the keystone species of typical tidal ditch invertebrates, and providing data support and theoretical reference for the monitoring and protection of invertebrate diversity.
, Available online ,
doi: 10.12284/hyxb2024104
Abstract:
The phenomenon of marine phytoplankton bloom in ocean refers to the annual cycle increase in biomass caused by rapid reproduction, which plays an important role in the biochemical cycles of marine organisms. However, the spatiotemporal variation characteristics of global phytoplankton blooms and their response mechanisms to the environment still require further exploration. Based on the chlorophyll a products of the MODIS-Aqua (Moderate Resolution Imaging Spectroradiometer) from 2003 to 2022, we extracted the bloom indexes of global ocean phytoplankton (the ratio of bloom duration and bloom intensity). Then, we analyzed their spatiotemporal characteristics, trends, and correlations with environmental factors. The results indicated that there are significant seasonal and latitudinal difference in the distribution of the bloom indexes. Blooms in high latitudes of the Northern Hemisphere mainly occurring from April to October, while in mid-low latitudes, blooms mainly occur from November to March of the following year. In the Southern Hemisphere, blooms develop in the month of November and persist until March of the following year in high latitudes, while those in low and middle latitudes occur from May to September. The ratio of bloom duration and bloom intensity shows a decreasing trend mainly in the mid-low latitude regions of the North Pacific, while increasing trends are observed in mid-high latitude regions of the Southern Hemisphere. The distribution and trends changes of blooms are both regulated by environmental factors. Sea surface temperature and photosynthetically active radiation promote blooms intensity in high latitude waters, but inhibit them in low latitude waters. Meanwhile, the wind speed plays a restraining role in the high latitude sea area and a promoting role in the low latitude sea area.
The phenomenon of marine phytoplankton bloom in ocean refers to the annual cycle increase in biomass caused by rapid reproduction, which plays an important role in the biochemical cycles of marine organisms. However, the spatiotemporal variation characteristics of global phytoplankton blooms and their response mechanisms to the environment still require further exploration. Based on the chlorophyll a products of the MODIS-Aqua (Moderate Resolution Imaging Spectroradiometer) from 2003 to 2022, we extracted the bloom indexes of global ocean phytoplankton (the ratio of bloom duration and bloom intensity). Then, we analyzed their spatiotemporal characteristics, trends, and correlations with environmental factors. The results indicated that there are significant seasonal and latitudinal difference in the distribution of the bloom indexes. Blooms in high latitudes of the Northern Hemisphere mainly occurring from April to October, while in mid-low latitudes, blooms mainly occur from November to March of the following year. In the Southern Hemisphere, blooms develop in the month of November and persist until March of the following year in high latitudes, while those in low and middle latitudes occur from May to September. The ratio of bloom duration and bloom intensity shows a decreasing trend mainly in the mid-low latitude regions of the North Pacific, while increasing trends are observed in mid-high latitude regions of the Southern Hemisphere. The distribution and trends changes of blooms are both regulated by environmental factors. Sea surface temperature and photosynthetically active radiation promote blooms intensity in high latitude waters, but inhibit them in low latitude waters. Meanwhile, the wind speed plays a restraining role in the high latitude sea area and a promoting role in the low latitude sea area.
, Available online ,
doi: 10.12284/hyxb2024124
Abstract:
Seagrass meadows play a vital role in protecting marine biodiversity, mitigating ocean acidification, and preventing soil erosion in the coastal ecosystem. However, global climate change and human activities seriously affect the life of seagrass, which causes the widespread degradation of the seagrass and threatens the safety of coastal ecosystems. Recently, the vital value of microorganisms in promoting the energy flow of seagrass meadows and their growth and development has gradually gained attention. Plant Growth-Promoting microorganisms(PGPM) will play their value in seedling cultivation, plant transplantation, seed planting, and other techniques of seagrass meadow restoration. This paper reviewed the research on how seagrass interacts with microorganisms to promote the growth of plants and increase the resistance to abiotic stress. We introduced the mechanism of PGPM to enhance plant stress tolerance under high temperature, high salt, and low light. The proposed use of modern molecular biology technology to screen seagrass PGPM, clarify the colonization site of PGPM, and explore the molecular interaction mechanism between PGPM and seagrass under different environmental conditions. To provide a reference for promoting the application of PGPM in seagrass meadow restoration and seagrass protection.
Seagrass meadows play a vital role in protecting marine biodiversity, mitigating ocean acidification, and preventing soil erosion in the coastal ecosystem. However, global climate change and human activities seriously affect the life of seagrass, which causes the widespread degradation of the seagrass and threatens the safety of coastal ecosystems. Recently, the vital value of microorganisms in promoting the energy flow of seagrass meadows and their growth and development has gradually gained attention. Plant Growth-Promoting microorganisms(PGPM) will play their value in seedling cultivation, plant transplantation, seed planting, and other techniques of seagrass meadow restoration. This paper reviewed the research on how seagrass interacts with microorganisms to promote the growth of plants and increase the resistance to abiotic stress. We introduced the mechanism of PGPM to enhance plant stress tolerance under high temperature, high salt, and low light. The proposed use of modern molecular biology technology to screen seagrass PGPM, clarify the colonization site of PGPM, and explore the molecular interaction mechanism between PGPM and seagrass under different environmental conditions. To provide a reference for promoting the application of PGPM in seagrass meadow restoration and seagrass protection.
, Available online ,
doi: 10.12284/hyxb2024126
Abstract:
The distribution of wave energy in enclosure aquaculture areas not only significantly influences nutrient transport but also constitutes a critical hydrological factor in validating the design of structures in inner aquaculture area. Investigating the changes in wave field energy influenced by these structures is crucial. The FUNWAVE 2.0 numerical model was employed to simulate irregular wave propagation in aquaculture areas with varying pile-net enclosure structures. The effects of pile spacing and incident wave angles in the evolution of wave energy was examined. The results indicate that if the internal facilities are positioned close to the outer pile-net enclosure structure, the pile spacing should be less than 1.0 m, provided that structural stability is ensured. Conversely, if the internal facilities are located farther from the outer pile-net enclosure, a pile spacing greater than 1.0 m should be selected. Additionally, oblique wave incidents may pose greater structural challenges at certain locations compared to normally incident waves, which should also be considered during design.
The distribution of wave energy in enclosure aquaculture areas not only significantly influences nutrient transport but also constitutes a critical hydrological factor in validating the design of structures in inner aquaculture area. Investigating the changes in wave field energy influenced by these structures is crucial. The FUNWAVE 2.0 numerical model was employed to simulate irregular wave propagation in aquaculture areas with varying pile-net enclosure structures. The effects of pile spacing and incident wave angles in the evolution of wave energy was examined. The results indicate that if the internal facilities are positioned close to the outer pile-net enclosure structure, the pile spacing should be less than 1.0 m, provided that structural stability is ensured. Conversely, if the internal facilities are located farther from the outer pile-net enclosure, a pile spacing greater than 1.0 m should be selected. Additionally, oblique wave incidents may pose greater structural challenges at certain locations compared to normally incident waves, which should also be considered during design.
, Available online
Abstract:
Due to the limitations of the Rayleigh criterion, classical harmonic analysis (CHA) model requires half a year of data records to analyze the eight main tidal constituents, namely, M2, S2, N2, K2, K1, O1, P1, Q1. For short-term tidal records, the unresolved constituents typically rely on the ratio differences from nearby long-term tidal stations for estimation. However, there is a scarcity of publicly available long-term tidal data in the coastal areas of Zhejiang, which currently prevents the accurate extraction of the main constituents from short-term records. This paper introduces a modified harmonic analysis model, referred to as the Modified Harmonic Analysis model based on the Credo of Smoothness (MHACS). Based on the smooth functions established by the intrinsic connections between major constituents, it breaks through the Rayleigh criterion, significantly reducing the length of tidal records required, especially suitable for coastal areas with abundant short-term data. This algorithm was applied to the multi-island area of Zhejiang offshore, using tidal records shorter than 15 days. The results show that the harmonic constants of the eight main constituents at the Shipu station are very close to the results obtained by the CHA method, and the required data length is reduced from8760 hours to 336 hours, which can be used to calculate characteristic parameters such as the theoretical depth datum. For analyzing the eight main constituents along the Zhejiang coast using MHACS, a minimum data length of 5 days is recommended.
Due to the limitations of the Rayleigh criterion, classical harmonic analysis (CHA) model requires half a year of data records to analyze the eight main tidal constituents, namely, M2, S2, N2, K2, K1, O1, P1, Q1. For short-term tidal records, the unresolved constituents typically rely on the ratio differences from nearby long-term tidal stations for estimation. However, there is a scarcity of publicly available long-term tidal data in the coastal areas of Zhejiang, which currently prevents the accurate extraction of the main constituents from short-term records. This paper introduces a modified harmonic analysis model, referred to as the Modified Harmonic Analysis model based on the Credo of Smoothness (MHACS). Based on the smooth functions established by the intrinsic connections between major constituents, it breaks through the Rayleigh criterion, significantly reducing the length of tidal records required, especially suitable for coastal areas with abundant short-term data. This algorithm was applied to the multi-island area of Zhejiang offshore, using tidal records shorter than 15 days. The results show that the harmonic constants of the eight main constituents at the Shipu station are very close to the results obtained by the CHA method, and the required data length is reduced from
, Available online
Abstract:
Three-dimensional (3D) geological models enable the intuitive representation of seabed geological conditions through using marine survey data, which actively promotes the development and construction of offshore wind farms. To enhance the accuracy and modelling efficiency of 3D geological models for offshore wind farms, a geological modelling method is proposed based on multi-source data fusion. This method conducts an integrated interpretation of geotechnical investigation data and engineering geophysical data, employs spatial interpolation algorithms to generate continuous and smooth layer interfaces, and utilizes Python open-source libraries to construct and visualize the 3D geological models. Furthermore, taking an offshore wind farm in eastern Guangdong as an example, the reliability of the geological modelling method is validated. The results demonstrate that the method achieves the effective integration of geotechnical and geophysical data, and the constructed 3D geological model could reflect the complex geological characteristics of the offshore wind farm. The proposed 3D geological modelling method is applicable to a diverse range of engineering geological conditions, providing solid technical support for the full lifecycle management of offshore wind farms, from exploration, design, installation, operation and maintenance to decommissioning.
Three-dimensional (3D) geological models enable the intuitive representation of seabed geological conditions through using marine survey data, which actively promotes the development and construction of offshore wind farms. To enhance the accuracy and modelling efficiency of 3D geological models for offshore wind farms, a geological modelling method is proposed based on multi-source data fusion. This method conducts an integrated interpretation of geotechnical investigation data and engineering geophysical data, employs spatial interpolation algorithms to generate continuous and smooth layer interfaces, and utilizes Python open-source libraries to construct and visualize the 3D geological models. Furthermore, taking an offshore wind farm in eastern Guangdong as an example, the reliability of the geological modelling method is validated. The results demonstrate that the method achieves the effective integration of geotechnical and geophysical data, and the constructed 3D geological model could reflect the complex geological characteristics of the offshore wind farm. The proposed 3D geological modelling method is applicable to a diverse range of engineering geological conditions, providing solid technical support for the full lifecycle management of offshore wind farms, from exploration, design, installation, operation and maintenance to decommissioning.
, Available online
Abstract:
Sea ice is a typical environmental feature of polar sea areas, and pixel-level classification of ship-borne video images can provide high-resolution sea ice information. Due to the complex light conditions and sea ice morphology in polar scenes, traditional computer graphics methods lack the generalization needed for intelligent identification of sea ice elements. Therefore, this paper deploys a deep learning approach based on the DeeplabV3+ semantic segmentation network structure to identify sea ice elements in polar scenes. The dataset consists of sea ice images captured by the icebreaker ‘Xuelong’ during its navigation in ice-covered regions, and also is used to train and validate the deep learning model. To meet the requirements of sea ice element identification and the characteristics of the underway observation video images, the pixel information is divided into four semantic categories: sea ice, sky, seawater, and ship. The deep learning model is built based on the correlation between image information and semantic information in the training set. The model trained is used to predict the semantic information of pixels in the validation set or other images, thereby achieving automatic identification of sea ice information. To study the robustness of this method, the influences of sea ice concentration, lighting conditions, and sea ice types on the identification results was further analyzed. Additionally, the effects of dataset size and the number of iterations on identification accuracy were examined. The recognition results for images show that the mean Intersection over Union (mIoU) for the four types of semantic information exceeds 95%, indicating that the deep learning method can accurately classify various elements in the polar environment.
Sea ice is a typical environmental feature of polar sea areas, and pixel-level classification of ship-borne video images can provide high-resolution sea ice information. Due to the complex light conditions and sea ice morphology in polar scenes, traditional computer graphics methods lack the generalization needed for intelligent identification of sea ice elements. Therefore, this paper deploys a deep learning approach based on the DeeplabV3+ semantic segmentation network structure to identify sea ice elements in polar scenes. The dataset consists of sea ice images captured by the icebreaker ‘Xuelong’ during its navigation in ice-covered regions, and also is used to train and validate the deep learning model. To meet the requirements of sea ice element identification and the characteristics of the underway observation video images, the pixel information is divided into four semantic categories: sea ice, sky, seawater, and ship. The deep learning model is built based on the correlation between image information and semantic information in the training set. The model trained is used to predict the semantic information of pixels in the validation set or other images, thereby achieving automatic identification of sea ice information. To study the robustness of this method, the influences of sea ice concentration, lighting conditions, and sea ice types on the identification results was further analyzed. Additionally, the effects of dataset size and the number of iterations on identification accuracy were examined. The recognition results for images show that the mean Intersection over Union (mIoU) for the four types of semantic information exceeds 95%, indicating that the deep learning method can accurately classify various elements in the polar environment.
, Available online ,
doi: 10.12284/hyxb2024005
Abstract:
High-quality in situ measurement data is a prerequisite for the validation of ocean color remote sensing data products, algorithm development, and climate change research. The in situ measurement data were mainly collected through methods such as ship-based measurements, mooring platforms (buoys), and Argo profiling floats. However, these processes typically require a substantial investment of manpower, resources, and finances, and data collected by individual research teams often struggle to support long-term and large-scale studies. Driven by the advances in "big data" science, several open-access data platforms, intergovernmental and national marine science data centers, as well as database platforms of major marine-related departments, have released diverse types of marine in situ measurement data, making them accessible freely to users. It is difficult for data users to quickly understand and apply shared data from these platforms, because of the discrete distribution of datasets on different platforms, and differences in data collection time, regions, disciplinary categories, and acquisition methods. This results in a time-consuming and labor-intensive process of gathering relevant research data. 29 database platforms were compiled and organized, including the open-access data platforms, marine science data centers, and marine science long-time series observation stations, that can be used or have potential use value in ocean color remote sensing studies and provided examples of typical applications of the shared data within these platforms for various studies. The applications mainly include the alternative calibration and validation of satellite products, the development and improvement of remote sensing retrieval models for biogeochemical parameters, and research on the optical properties of seas. In terms of data sources, the shared data primarily originate from developed countries such as Europe and the United States. Temporally and spatially, the collection time of shared data spans a century, with the majority collected in the past 30 years and distributed mainly in the open oceans and coastal waters of countries such as the United States and Australia. Regarding data types, there are richness in ocean optical and biogeochemical parameters, but insufficient synchronous collection of both data, which may hamper the study of the optical characteristics of biogeochemical parameters.
High-quality in situ measurement data is a prerequisite for the validation of ocean color remote sensing data products, algorithm development, and climate change research. The in situ measurement data were mainly collected through methods such as ship-based measurements, mooring platforms (buoys), and Argo profiling floats. However, these processes typically require a substantial investment of manpower, resources, and finances, and data collected by individual research teams often struggle to support long-term and large-scale studies. Driven by the advances in "big data" science, several open-access data platforms, intergovernmental and national marine science data centers, as well as database platforms of major marine-related departments, have released diverse types of marine in situ measurement data, making them accessible freely to users. It is difficult for data users to quickly understand and apply shared data from these platforms, because of the discrete distribution of datasets on different platforms, and differences in data collection time, regions, disciplinary categories, and acquisition methods. This results in a time-consuming and labor-intensive process of gathering relevant research data. 29 database platforms were compiled and organized, including the open-access data platforms, marine science data centers, and marine science long-time series observation stations, that can be used or have potential use value in ocean color remote sensing studies and provided examples of typical applications of the shared data within these platforms for various studies. The applications mainly include the alternative calibration and validation of satellite products, the development and improvement of remote sensing retrieval models for biogeochemical parameters, and research on the optical properties of seas. In terms of data sources, the shared data primarily originate from developed countries such as Europe and the United States. Temporally and spatially, the collection time of shared data spans a century, with the majority collected in the past 30 years and distributed mainly in the open oceans and coastal waters of countries such as the United States and Australia. Regarding data types, there are richness in ocean optical and biogeochemical parameters, but insufficient synchronous collection of both data, which may hamper the study of the optical characteristics of biogeochemical parameters.
, Available online ,
doi: 10.12284/hyxb2024055
Abstract:
Sandy and mixed beach-bar, which has good exploration potential, are widely developed in the upper fourth member of Shahejie Formation(Es4U) to the lower third member of Shahejie Formation (Es3L) of the Laizhou Bay Sag in the Bohai Bay Basin. At present, the sedimentary characteristics, genesis mechanism, and evolution mode of the beach-bar are still poorly understood, which seriously restricts the exploration and prediction of this type of sedimentation. Therefore, this study makes comprehensive use of drilling, logging, and seismic data to finely recover the micro-paleogeomorphology of the study area, clarifies the controlling role of geomorphology of the multi-stage gentle slope on the development of the beach-bar in the study area, sums up the depositional characteristics and the main controlling factors of the sand bodies of the beach-bar at different locations, and constructs the depositional model. The results show that: (1) sandy beach-bar are mainly developed in the front flanks of the braided river delta of the Es4U, which are mainly controlled by the windward geomorphic features of the first-stage gentle slope, strong sediment supply, and paleo-wind direction. (2) The thick-layered mixed beach-bar are mainly developed in the windward zone of the secondary gentle slope of the Es4U, which is jointly influenced by paleo-morphology, medium sediment supply, and coastal currents. (3) The thin-layered mixed beach-bar are developed in the windward zone of the first-stage gentle slope of the Es3L, which is influenced by the combination of paleo-morphology, weak sediment supply, paleo-wind direction, and littoral current. By dividing the multi-stage gentle slope geomorphology, the establishment of the depositional model can help to predict the distribution of the sand body of the beach-bar and provide a reference for the exploration of the sand body of the beach-bar in the Bohai Bay Basin.
Sandy and mixed beach-bar, which has good exploration potential, are widely developed in the upper fourth member of Shahejie Formation(Es4U) to the lower third member of Shahejie Formation (Es3L) of the Laizhou Bay Sag in the Bohai Bay Basin. At present, the sedimentary characteristics, genesis mechanism, and evolution mode of the beach-bar are still poorly understood, which seriously restricts the exploration and prediction of this type of sedimentation. Therefore, this study makes comprehensive use of drilling, logging, and seismic data to finely recover the micro-paleogeomorphology of the study area, clarifies the controlling role of geomorphology of the multi-stage gentle slope on the development of the beach-bar in the study area, sums up the depositional characteristics and the main controlling factors of the sand bodies of the beach-bar at different locations, and constructs the depositional model. The results show that: (1) sandy beach-bar are mainly developed in the front flanks of the braided river delta of the Es4U, which are mainly controlled by the windward geomorphic features of the first-stage gentle slope, strong sediment supply, and paleo-wind direction. (2) The thick-layered mixed beach-bar are mainly developed in the windward zone of the secondary gentle slope of the Es4U, which is jointly influenced by paleo-morphology, medium sediment supply, and coastal currents. (3) The thin-layered mixed beach-bar are developed in the windward zone of the first-stage gentle slope of the Es3L, which is influenced by the combination of paleo-morphology, weak sediment supply, paleo-wind direction, and littoral current. By dividing the multi-stage gentle slope geomorphology, the establishment of the depositional model can help to predict the distribution of the sand body of the beach-bar and provide a reference for the exploration of the sand body of the beach-bar in the Bohai Bay Basin.
, Available online
Abstract:
Saline water intrusion at the Yangtze River Estuary severely affects the security of upstream water supply, agricultural irrigation, and ecological environmental health. The distance of saline water intrusion upstream, influenced by the interaction between runoff and tidal forces, has received considerable attention. However, research on the extent of this intrusion under the influence of the runoff-tide interaction remains insufficient.This paper establishes a three-dimensional hydrodynamic and salinity mathematical model of the Yangtze River Estuary using the MIKE 3 hydrodynamic model. The model is validated against field measurements of water levels, flow velocities, flow directions, and salinity from the Yangtze River Estuary in 2016. The validation results show a good agreement between the simulated and measured values, indicating that the three-dimensional hydrodynamic and salinity mathematical model of the Yangtze River Estuary established in this study can effectively simulate the hydrodynamic and salinity characteristics in the vicinity of the estuary.To investigate the impact of upstream runoff on the extent of saltwater intrusion in the Yangtze River Estuary, this study sets up eight different flow rates ranging from 15,000 to 50,000 m3/s for the upstream section of the Yangtze River Estuary. The simulations focus on the effects of these varying upstream flow rates on the saltwater intrusion distances in three navigation channels: the South Branch-North Port, the South Branch-South Port-North Channel, and the South Branch-South Port-South Channel. The simulation results indicate that the degree of saltwater intrusion in all three channels is significantly dependent on tidal dynamics. During spring tides, when tidal forces are stronger, both the seawater backflow into the North Port and the saltwater intrusion into the North Branch are more pronounced compared to neap tides, resulting in longer saltwater intrusion distances overall during spring tides. When the upstream discharge is low, backflow from the North Branch also contributes to increased saltwater intrusion distances.The vertical distribution of salinity and stratification phenomena in the three channels under different flow conditions were also analyzed, and the relationships between upstream flow rates and the distances of saltwater intrusion in the three channels were established. The findings of this study provide valuable references for research on "salinity control and freshwater supplementation" in the Yangtze River Estuary, as well as studies on material transport.
Saline water intrusion at the Yangtze River Estuary severely affects the security of upstream water supply, agricultural irrigation, and ecological environmental health. The distance of saline water intrusion upstream, influenced by the interaction between runoff and tidal forces, has received considerable attention. However, research on the extent of this intrusion under the influence of the runoff-tide interaction remains insufficient.This paper establishes a three-dimensional hydrodynamic and salinity mathematical model of the Yangtze River Estuary using the MIKE 3 hydrodynamic model. The model is validated against field measurements of water levels, flow velocities, flow directions, and salinity from the Yangtze River Estuary in 2016. The validation results show a good agreement between the simulated and measured values, indicating that the three-dimensional hydrodynamic and salinity mathematical model of the Yangtze River Estuary established in this study can effectively simulate the hydrodynamic and salinity characteristics in the vicinity of the estuary.To investigate the impact of upstream runoff on the extent of saltwater intrusion in the Yangtze River Estuary, this study sets up eight different flow rates ranging from 15,000 to 50,000 m3/s for the upstream section of the Yangtze River Estuary. The simulations focus on the effects of these varying upstream flow rates on the saltwater intrusion distances in three navigation channels: the South Branch-North Port, the South Branch-South Port-North Channel, and the South Branch-South Port-South Channel. The simulation results indicate that the degree of saltwater intrusion in all three channels is significantly dependent on tidal dynamics. During spring tides, when tidal forces are stronger, both the seawater backflow into the North Port and the saltwater intrusion into the North Branch are more pronounced compared to neap tides, resulting in longer saltwater intrusion distances overall during spring tides. When the upstream discharge is low, backflow from the North Branch also contributes to increased saltwater intrusion distances.The vertical distribution of salinity and stratification phenomena in the three channels under different flow conditions were also analyzed, and the relationships between upstream flow rates and the distances of saltwater intrusion in the three channels were established. The findings of this study provide valuable references for research on "salinity control and freshwater supplementation" in the Yangtze River Estuary, as well as studies on material transport.
, Available online
Abstract:
To better understand the community patterns and their interconnections between different habitats in coastal areas, it is essential to explore the potential factors influencing species distribution and ecological connectivity between artificial and natural habitats. This study conducted a comprehensive survey of fish and invertebrate communities across four typical habitats in Haizhou Bay, Jiangsu Province: artificial reef area (ARA), nori culture area (NCA), oyster culture area (OCA), and natural area (NA). The results showed significant differences in species abundance among the four habitats (P<0.05), with some important species occurring across multiple habitats, and some endemic species restricted to a single habitat. The biomass of Oratosquilla oratoria in ARA was significantly higher compared to other habitats, and the body length of Chaeturichthys stigmatias in ARA, NCA, and OCA was significantly greater than in NA (P<0.05), which was strongly associated with the distribution of prey organisms. Differences in body length distributions of fish with different life habits indicate that species migration behavior plays an important role in species distribution and habitat connectivity. Migratory fish species, such as Larimichthys polyactis and Sardinella zunasi, exhibited significantly greater body lengths in artificial habitats compared to natural habitats (P<0.05). Resident fish species, such as Chaeturichthys stigmatias, exhibited significantly larger body lengths in OCA compared to ARA and NCA (P<0.05), while Cynoglossus joyneri exhibited a significantly greater body length in NCA than in ARA and OCA (P<0.05). This study demonstrates that artificial habitats, by enhancing habitat complexity, provide favorable environmental conditions for the restoration of marine biological resources and the development of individuals. The distribution of prey organisms and species migration characteristics are likely associated with connectivity between different habitats.
To better understand the community patterns and their interconnections between different habitats in coastal areas, it is essential to explore the potential factors influencing species distribution and ecological connectivity between artificial and natural habitats. This study conducted a comprehensive survey of fish and invertebrate communities across four typical habitats in Haizhou Bay, Jiangsu Province: artificial reef area (ARA), nori culture area (NCA), oyster culture area (OCA), and natural area (NA). The results showed significant differences in species abundance among the four habitats (P<0.05), with some important species occurring across multiple habitats, and some endemic species restricted to a single habitat. The biomass of Oratosquilla oratoria in ARA was significantly higher compared to other habitats, and the body length of Chaeturichthys stigmatias in ARA, NCA, and OCA was significantly greater than in NA (P<0.05), which was strongly associated with the distribution of prey organisms. Differences in body length distributions of fish with different life habits indicate that species migration behavior plays an important role in species distribution and habitat connectivity. Migratory fish species, such as Larimichthys polyactis and Sardinella zunasi, exhibited significantly greater body lengths in artificial habitats compared to natural habitats (P<0.05). Resident fish species, such as Chaeturichthys stigmatias, exhibited significantly larger body lengths in OCA compared to ARA and NCA (P<0.05), while Cynoglossus joyneri exhibited a significantly greater body length in NCA than in ARA and OCA (P<0.05). This study demonstrates that artificial habitats, by enhancing habitat complexity, provide favorable environmental conditions for the restoration of marine biological resources and the development of individuals. The distribution of prey organisms and species migration characteristics are likely associated with connectivity between different habitats.
, Available online
Abstract:
Dissolved oxygen concentration is one of the important indexes to measure seawater quality. In order to grasp the change of seawater quality in time and reduce the risk and loss of seawater pollution, it is very important to establish the prediction mechanism of Marine water quality parameters. Therefore, this paper proposes a prediction model of dissolved oxygen concentration in seawater based on temporal and spatial information fusion of buoy Networks and Generative Adversarial Networks (GAN), which aims to integrate topological information of buoy networks in the monitoring area and realize multi-feature fusion of buoy sensors. The model uses the Graph Attention Mechanism (GAT) to mine the influence of different nearest neighbor points on the target node and calculate the weights of the adjacent nodes, so as to capture the spatio-temporal characteristics of the buoy data. The two-head attention mechanism and the two-time-scale Update Rule (TTUR) were used to optimize the GAN prediction network and the network training process, improve the training speed balance of the generated adduction network, and improve the fitting effect of the generator network. The mean squared error, root mean squared error, mean absolute error and R-Square are used as evaluation indexes to compare the model prediction performance. The results show that the evaluation indexes of the proposed model are superior to other models, and can effectively mine the spatial information of multiple buoys. It overcomes the shortcomings of traditional methods in the prediction of dissolved oxygen concentration in seawater, such as low accuracy, inability to flexibly use historical spatial data, poor training stability and slow speed, and can provide important technical support for Marine water quality monitoring and prediction.
Dissolved oxygen concentration is one of the important indexes to measure seawater quality. In order to grasp the change of seawater quality in time and reduce the risk and loss of seawater pollution, it is very important to establish the prediction mechanism of Marine water quality parameters. Therefore, this paper proposes a prediction model of dissolved oxygen concentration in seawater based on temporal and spatial information fusion of buoy Networks and Generative Adversarial Networks (GAN), which aims to integrate topological information of buoy networks in the monitoring area and realize multi-feature fusion of buoy sensors. The model uses the Graph Attention Mechanism (GAT) to mine the influence of different nearest neighbor points on the target node and calculate the weights of the adjacent nodes, so as to capture the spatio-temporal characteristics of the buoy data. The two-head attention mechanism and the two-time-scale Update Rule (TTUR) were used to optimize the GAN prediction network and the network training process, improve the training speed balance of the generated adduction network, and improve the fitting effect of the generator network. The mean squared error, root mean squared error, mean absolute error and R-Square are used as evaluation indexes to compare the model prediction performance. The results show that the evaluation indexes of the proposed model are superior to other models, and can effectively mine the spatial information of multiple buoys. It overcomes the shortcomings of traditional methods in the prediction of dissolved oxygen concentration in seawater, such as low accuracy, inability to flexibly use historical spatial data, poor training stability and slow speed, and can provide important technical support for Marine water quality monitoring and prediction.
, Available online ,
doi: 10.12284/hyxb2025006
Abstract:
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
, Available online ,
doi: 10.12284/hyxb2025012
Abstract:
Understanding the distribution, migration, and transformation of organic carbon in the ocean is of great significance to study the global carbon cycle and tackle climate change. Here, surface sediment samples were collected from the Bohai Sea and the Yellow Sea. For illustrating the source composition, distribution pattern, and their constraints, material characterization such as specific surface area, total organic carbon, nitrogen, sulfur contents and their isotopes (TOC, TN, TS, S2‒, δ13C, δ15N, and δ34S), as well as pigment biomarkers and thermos-gravimetric analysis were conducted. The results showed that the TOC and TN contents were lower in the nearshore but higher in the offshore region due to stronger hydrodynamics nearshore. The specific surface area had significant impacts on the distribution of organic carbon. Three-endmember mixing model suggested that sediments near the Huanghe River mouth and the shallower region along the Liaodong Peninsula in the Bohai Sea were dominated by soil-derived organic carbon with a smaller carbon reactivity index, while marine phytoplankton contributed mostly to the southern Yellow Sea with increasing carbon reactivity index. Significant correlation between TOC and TS in the Bohai Sea and northern Yellow Sea indicated significant linkages between organic carbon degradation and sulfate reduction. The negative δ34S indicated the process of sulfate reduction-sulfide oxidation-seawater sulfate diffusion at the sediment-water interface, which hinted the oxidation of organic carbon from oxic to anoxic condition. Pigment degradation potentially resulted in its weak correlation with the TOC content. As the risk of harmful algal bloom and hypoxia is becoming more severe, it is essential to monitor the water chemistry and elemental cycling in the sediment to comprehensively understand the role of the continental shelf on organic carbon burial.
Understanding the distribution, migration, and transformation of organic carbon in the ocean is of great significance to study the global carbon cycle and tackle climate change. Here, surface sediment samples were collected from the Bohai Sea and the Yellow Sea. For illustrating the source composition, distribution pattern, and their constraints, material characterization such as specific surface area, total organic carbon, nitrogen, sulfur contents and their isotopes (TOC, TN, TS, S2‒, δ13C, δ15N, and δ34S), as well as pigment biomarkers and thermos-gravimetric analysis were conducted. The results showed that the TOC and TN contents were lower in the nearshore but higher in the offshore region due to stronger hydrodynamics nearshore. The specific surface area had significant impacts on the distribution of organic carbon. Three-endmember mixing model suggested that sediments near the Huanghe River mouth and the shallower region along the Liaodong Peninsula in the Bohai Sea were dominated by soil-derived organic carbon with a smaller carbon reactivity index, while marine phytoplankton contributed mostly to the southern Yellow Sea with increasing carbon reactivity index. Significant correlation between TOC and TS in the Bohai Sea and northern Yellow Sea indicated significant linkages between organic carbon degradation and sulfate reduction. The negative δ34S indicated the process of sulfate reduction-sulfide oxidation-seawater sulfate diffusion at the sediment-water interface, which hinted the oxidation of organic carbon from oxic to anoxic condition. Pigment degradation potentially resulted in its weak correlation with the TOC content. As the risk of harmful algal bloom and hypoxia is becoming more severe, it is essential to monitor the water chemistry and elemental cycling in the sediment to comprehensively understand the role of the continental shelf on organic carbon burial.
, Available online ,
doi: 10.12284/hyxb2025004
Abstract:
The Trachurus murphyi is affected by the environment, and the environment itself changes with time, with short-term seasonal changes and long-term regime shifts. Based on the data on jack mackerel stock and the environment from 1970 to 2017, this paper analyzes the relationship between the environment and jack mackerel stock from month to year using integral regression, modal analysis, and full subset regression analysis. The month-on-month analysis results show that the influence of Sea Surface Temperature (SST) on stock biomass changes most obviously with time. Chilean jack mackerel is more dependent on SST in spawning and overwintering seasons; Followed by the Pacific Decadal Oscillation (PDO), The effects of Sea Surface Salinity (SSS) and Oceanic Nino Index (ONI) vary less in different months; The impact of Sea Surface Height (SSH) hardly changes from month to month. The annual analysis revealed four distinct regime shifts in Chilean mackerel resources over a long-time scale, with each regime characterized by unique dominant factor combinations. Notably, with the escalation of global climate change in recent years, a broader array of environmental factors has potentially influenced fishery resources, leading to substantial modifications in the environmental impact mode on fisheries.
The Trachurus murphyi is affected by the environment, and the environment itself changes with time, with short-term seasonal changes and long-term regime shifts. Based on the data on jack mackerel stock and the environment from 1970 to 2017, this paper analyzes the relationship between the environment and jack mackerel stock from month to year using integral regression, modal analysis, and full subset regression analysis. The month-on-month analysis results show that the influence of Sea Surface Temperature (SST) on stock biomass changes most obviously with time. Chilean jack mackerel is more dependent on SST in spawning and overwintering seasons; Followed by the Pacific Decadal Oscillation (PDO), The effects of Sea Surface Salinity (SSS) and Oceanic Nino Index (ONI) vary less in different months; The impact of Sea Surface Height (SSH) hardly changes from month to month. The annual analysis revealed four distinct regime shifts in Chilean mackerel resources over a long-time scale, with each regime characterized by unique dominant factor combinations. Notably, with the escalation of global climate change in recent years, a broader array of environmental factors has potentially influenced fishery resources, leading to substantial modifications in the environmental impact mode on fisheries.
, Available online
Abstract:
Bigeye grunt Brachydeuterus auritus is an important economic species in the waters off Sierra Leone in West Africa, with great ecological value. Based on the survey data of bottom trawl nets from 6 samples from 2019 to 2021, the body weight-length relationship (WLR), as well as their relative weight, were studied in depth using the method of body length and its corresponding mean body weight. This study fitted the WLR of bigeye grunt by gender, calculated its fullness, and analyzed the influence of environmental factors. The results showed that month and gender had a significant impact on body length and weight distribution (P<0.01). There was a highly significant negative correlation (P<0.01) between a value and b value in the WLR, and salinity significantly affects b value (P<0.05). The (lga)/b ratio was less affected by environmental factors which may be related to the body size and density of the fish. The difference in b between male and female populations was highly significant (P<0.01). The relative weight had significant seasonal variation characteristics, with highly significant effects of sex and body length (P<0.01). With increasing body length, the relative weight showed two types of changes, continuously increasing and first increasing then decreasing, with salinity and b significantly affecting the type of change (P<0.05) and depth having a highly significant effect (P<0.01). The bigeye grunt off the coast Sierra Leone exhibited significant seasonal growth characteristics, with significant differences in growth characteristics between male and female individuals. This study suggested that salinity may be the main factor affecting its growth and development. In addition, this study hypothesised that the peak breeding season may occur during the dry season, beginning in December and ending before April of the following year. The study provides updated and more comprehensive insights into the biology and ecology of the bigeye grunt offshore Sierra Leone, West Africa, which can provide scientific basis for its resource assessment, development and utilization, and resource management.
Bigeye grunt Brachydeuterus auritus is an important economic species in the waters off Sierra Leone in West Africa, with great ecological value. Based on the survey data of bottom trawl nets from 6 samples from 2019 to 2021, the body weight-length relationship (WLR), as well as their relative weight, were studied in depth using the method of body length and its corresponding mean body weight. This study fitted the WLR of bigeye grunt by gender, calculated its fullness, and analyzed the influence of environmental factors. The results showed that month and gender had a significant impact on body length and weight distribution (P<0.01). There was a highly significant negative correlation (P<0.01) between a value and b value in the WLR, and salinity significantly affects b value (P<0.05). The (lga)/b ratio was less affected by environmental factors which may be related to the body size and density of the fish. The difference in b between male and female populations was highly significant (P<0.01). The relative weight had significant seasonal variation characteristics, with highly significant effects of sex and body length (P<0.01). With increasing body length, the relative weight showed two types of changes, continuously increasing and first increasing then decreasing, with salinity and b significantly affecting the type of change (P<0.05) and depth having a highly significant effect (P<0.01). The bigeye grunt off the coast Sierra Leone exhibited significant seasonal growth characteristics, with significant differences in growth characteristics between male and female individuals. This study suggested that salinity may be the main factor affecting its growth and development. In addition, this study hypothesised that the peak breeding season may occur during the dry season, beginning in December and ending before April of the following year. The study provides updated and more comprehensive insights into the biology and ecology of the bigeye grunt offshore Sierra Leone, West Africa, which can provide scientific basis for its resource assessment, development and utilization, and resource management.
, Available online
Abstract:
Investigating the impact of high-level pond aquaculture effluent discharge on the response mechanisms of sandy coastlines to typhoons is of significant importance for promoting the sustainable use and enhancement of coastal resources. This study conducts a comparative analysis of sediment characteristics, including particle size, grain size distribution, and grain size parameters, before and after Typhoon No. 2203, " Xianba," focusing on the influence of effluent discharge from high-level ponds on the coastal sediment distribution at Donghai Island in western Guangdong, as well as on normal coastal areas. The research findings indicate the following: (1) After the typhoon, the sediment in normal coastal areas exhibited poorer sorting, with finer sediments nearshore and coarser sediments offshore; (2) The sorting coefficient of sediment from the affected coastal area remained stable post-typhoon, while other parameters (characteristic particle size, grain size composition, and grain size parameters) did not show a consistent pattern of change; (3) The average changes in characteristic particle sizes (D10, D50, and D90) and mean particle size of the affected coastal sediments were significantly greater than those of the normal coastal sediments after the typhoon. The intense wave action and rising water levels induced by the typhoon are critical factors influencing the sediment response in normal coastal areas. In contrast, the response of sediments in the affected coastal areas is more complex, resulting from the interplay between the gully topography created by effluent discharge and sediment redistribution processes, coupled with storm surge dynamics during the storm. This study provides a case for understanding the sediment grain size response characteristics of coastal areas influenced by high-level pond effluent during typhoon events, contributing to a better understanding of the interaction mechanisms between extreme events and aquaculture activities in coastal geomorphological evolution.
Investigating the impact of high-level pond aquaculture effluent discharge on the response mechanisms of sandy coastlines to typhoons is of significant importance for promoting the sustainable use and enhancement of coastal resources. This study conducts a comparative analysis of sediment characteristics, including particle size, grain size distribution, and grain size parameters, before and after Typhoon No. 2203, " Xianba," focusing on the influence of effluent discharge from high-level ponds on the coastal sediment distribution at Donghai Island in western Guangdong, as well as on normal coastal areas. The research findings indicate the following: (1) After the typhoon, the sediment in normal coastal areas exhibited poorer sorting, with finer sediments nearshore and coarser sediments offshore; (2) The sorting coefficient of sediment from the affected coastal area remained stable post-typhoon, while other parameters (characteristic particle size, grain size composition, and grain size parameters) did not show a consistent pattern of change; (3) The average changes in characteristic particle sizes (D10, D50, and D90) and mean particle size of the affected coastal sediments were significantly greater than those of the normal coastal sediments after the typhoon. The intense wave action and rising water levels induced by the typhoon are critical factors influencing the sediment response in normal coastal areas. In contrast, the response of sediments in the affected coastal areas is more complex, resulting from the interplay between the gully topography created by effluent discharge and sediment redistribution processes, coupled with storm surge dynamics during the storm. This study provides a case for understanding the sediment grain size response characteristics of coastal areas influenced by high-level pond effluent during typhoon events, contributing to a better understanding of the interaction mechanisms between extreme events and aquaculture activities in coastal geomorphological evolution.
, Available online ,
doi: 10.12284/hyxb2024130
Abstract:
The stratospheric sulfate aerosol layer formed after large volcanic eruptions can inhibit the formation and development of tropical cyclones, but relevant studies mainly focus on the Atlantic Ocean, and few involve other sea areas. The Northwest Pacific Ocean is the area where most tropical cyclones are generated. Exploring the climate influencing factors is helpful for us to deeply understand the generation and development mechanism of tropical cyclones. Based on the data of tropical cyclones in the Northwest Pacific Ocean recorded in the International Optimum Orbit Database and the China Meteorological Administration database, the changes of sea surface temperature and the number of tropical cyclones in the Northwest Pacific Ocean before and after major volcanic eruptions during 1900—2023 are compared, and the effects of major volcanic eruptions on tropical cyclones in the Northwest Pacific Ocean are discussed. By comparing the number of tropical cyclones two years before the eruption and two years after the eruption, we found that the number of tropical cyclones in the Northwest Pacific decreased significantly after a major eruption. The sea surface temperature significantly responds to low-latitude volcanic eruptions, but does not significantly respond to high-latitude volcanic eruptions. Our study shows that the increase of aerosol forcing after large volcanic eruptions is closely related to the frequency of tropical cyclones, but the decrease of sea surface temperature caused by it may not be the direct cause of the decrease of tropical cyclones, and its mechanism may be related to the migration of the intertropical convergence zone caused by aerosol forcing, which still needs further investigation.
The stratospheric sulfate aerosol layer formed after large volcanic eruptions can inhibit the formation and development of tropical cyclones, but relevant studies mainly focus on the Atlantic Ocean, and few involve other sea areas. The Northwest Pacific Ocean is the area where most tropical cyclones are generated. Exploring the climate influencing factors is helpful for us to deeply understand the generation and development mechanism of tropical cyclones. Based on the data of tropical cyclones in the Northwest Pacific Ocean recorded in the International Optimum Orbit Database and the China Meteorological Administration database, the changes of sea surface temperature and the number of tropical cyclones in the Northwest Pacific Ocean before and after major volcanic eruptions during 1900—2023 are compared, and the effects of major volcanic eruptions on tropical cyclones in the Northwest Pacific Ocean are discussed. By comparing the number of tropical cyclones two years before the eruption and two years after the eruption, we found that the number of tropical cyclones in the Northwest Pacific decreased significantly after a major eruption. The sea surface temperature significantly responds to low-latitude volcanic eruptions, but does not significantly respond to high-latitude volcanic eruptions. Our study shows that the increase of aerosol forcing after large volcanic eruptions is closely related to the frequency of tropical cyclones, but the decrease of sea surface temperature caused by it may not be the direct cause of the decrease of tropical cyclones, and its mechanism may be related to the migration of the intertropical convergence zone caused by aerosol forcing, which still needs further investigation.
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Abstract:
During an investigation of marine diatom flora in the sand samples from Guangxi, three species were identified as new records in China, which were Halamphora woelfeliae Stachura-Suchoples, Enke, Schlie, Schaub, Karsten & R.Jahn, Psammodiscus calceatus Tsuy.Watanabe, Nagumo & Ji.Tanaka and Ehrenbergiulva granulosa (Grunow) A.Witkowski, Lange-Bertalot & Metzeltin. Their morphological features, ecological habitats and geographical distribution were described in detail. This study enriched the biodiversity of marine diatoms in China.
During an investigation of marine diatom flora in the sand samples from Guangxi, three species were identified as new records in China, which were Halamphora woelfeliae Stachura-Suchoples, Enke, Schlie, Schaub, Karsten & R.Jahn, Psammodiscus calceatus Tsuy.Watanabe, Nagumo & Ji.Tanaka and Ehrenbergiulva granulosa (Grunow) A.Witkowski, Lange-Bertalot & Metzeltin. Their morphological features, ecological habitats and geographical distribution were described in detail. This study enriched the biodiversity of marine diatoms in China.
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Abstract:
This study compiled data on the 239+240Pu concentration or specific ratio-activity, 240Pu/239Pu atom ratio, and 239+240Pu flux or inventory in seawater, corals, shells and sediment samples in the Northern South China Sea. The 239+240Pu sources and trends in surface seawater, water columns, surface sediments, and sediment cores in this area were presented. According to the two end member model, global fallout (GF) and the Pacific Proving Grounds (PPG) were currently the sources of 239+240Pu in environmental samples investigated from the northern South China Sea. Meanwhile, according to the migration model, it was found for the first time that a positive linear relationship between the water depth corresponding to the 239+240Pu peak concentration in the water column and its migration rate. The correlation between the organic matter content or particle size of surface sediments and the 239+240Pu specific ratio-activity had a segmented nature, showing positive and negative correlations, respectively. The numerical result of the 239+240Pu chrono-marker sedimentation rate in sediment core samples was usually greater than or equal to the maximum apparent diffusion rate of relatively exchangeable 239+240Pu in the same core sample, and there was a significant positive linear relationship between the sedimentation rate and the maximum apparent diffusion rate, the maximum apparent diffusion rate of relatively exchangeable 239+240Pu does not affect the sedimentation rate.
This study compiled data on the 239+240Pu concentration or specific ratio-activity, 240Pu/239Pu atom ratio, and 239+240Pu flux or inventory in seawater, corals, shells and sediment samples in the Northern South China Sea. The 239+240Pu sources and trends in surface seawater, water columns, surface sediments, and sediment cores in this area were presented. According to the two end member model, global fallout (GF) and the Pacific Proving Grounds (PPG) were currently the sources of 239+240Pu in environmental samples investigated from the northern South China Sea. Meanwhile, according to the migration model, it was found for the first time that a positive linear relationship between the water depth corresponding to the 239+240Pu peak concentration in the water column and its migration rate. The correlation between the organic matter content or particle size of surface sediments and the 239+240Pu specific ratio-activity had a segmented nature, showing positive and negative correlations, respectively. The numerical result of the 239+240Pu chrono-marker sedimentation rate in sediment core samples was usually greater than or equal to the maximum apparent diffusion rate of relatively exchangeable 239+240Pu in the same core sample, and there was a significant positive linear relationship between the sedimentation rate and the maximum apparent diffusion rate, the maximum apparent diffusion rate of relatively exchangeable 239+240Pu does not affect the sedimentation rate.
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Abstract:
In order to systematically study the effect of low temperature stress on the lipid metabolism of cobia juvenile, cobia juveniles were raised at normal temperature (30.5±1.0℃) and low temperature (20.0±0.5℃) for 7 days, and then the cobia livers were sequenced with genome-based transcriptome, and there were 3 biological replicates in each group. The research results show that a total of 243,694,134 row reads were found in 6 sequencing samples. The Q30% of all samples exceeded 94%, and the GC% was in the range of 47.65%-48.16%. A total of 4,362 differentially expressed genes were screened, of which 2,793 genes were up-regulated, and 1,569 genes were down-regulated. In terms of lipid metabolism, A large number of differential genes are enriched in biological processes such as lipid metabolism, lipid biosynthesis, glycerophospholipid metabolism, phospholipid metabolism and glycerideid metabolism, and also found that multiple lipid metabolism-related genes in the PPAR signaling pathway, such as PPARα, PPARβ, SCD-1, CPT-1, and CPT-2 play a key role in cobia juvenile under low temperature stress. In terms of glucose metabolism, a great many of genes are enriched in biological processes such as glycolysis/gluconeogenesis, galactose metabolism, starch and sucrose metabolism, and pentose and glucuronate interconversions. Notably, genes such as G6PC and ENO play crucial regulatory roles in the response of cobia juvenile to low temperature stress.
In order to systematically study the effect of low temperature stress on the lipid metabolism of cobia juvenile, cobia juveniles were raised at normal temperature (30.5±1.0℃) and low temperature (20.0±0.5℃) for 7 days, and then the cobia livers were sequenced with genome-based transcriptome, and there were 3 biological replicates in each group. The research results show that a total of 243,694,134 row reads were found in 6 sequencing samples. The Q30% of all samples exceeded 94%, and the GC% was in the range of 47.65%-48.16%. A total of 4,362 differentially expressed genes were screened, of which 2,793 genes were up-regulated, and 1,569 genes were down-regulated. In terms of lipid metabolism, A large number of differential genes are enriched in biological processes such as lipid metabolism, lipid biosynthesis, glycerophospholipid metabolism, phospholipid metabolism and glycerideid metabolism, and also found that multiple lipid metabolism-related genes in the PPAR signaling pathway, such as PPARα, PPARβ, SCD-1, CPT-1, and CPT-2 play a key role in cobia juvenile under low temperature stress. In terms of glucose metabolism, a great many of genes are enriched in biological processes such as glycolysis/gluconeogenesis, galactose metabolism, starch and sucrose metabolism, and pentose and glucuronate interconversions. Notably, genes such as G6PC and ENO play crucial regulatory roles in the response of cobia juvenile to low temperature stress.
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doi: 10.12284/hyxb2024125
Abstract:
In recent decades, the beaches on both sides of the Jiehe River (hereinafter referred to as Jiehe Beach) in the northeastern part of Laizhou Bay have suffered severe erosion against the backdrop of reduced riverine sediment input to the sea. Additionally, the construction of coastal engineering projects such as Yulong Island (a large artificial offshore island) has made the evolution of the Jiehe Beach shoreline exceptionally complex. This paper utilizes1186 satellite images from 1984 to 2024, employing a transect-focused method and sub-pixel shoreline recognition technology to study the evolution of the Jiehe Beach shoreline and assess the impacts of river sediment discharge and coastal engineering. The results show that the early evolution (1984−2004) of Jiehe Beach was primarily controlled by the closure and opening of the Jiehe River estuary, the alongshore movement of sand spits, and the onshore movement of sandbars, with overall erosion occurring. The later evolution (2004−2024) of Jiehe Beach was mainly influenced by the construction of coastal engineering projects such as Yulong Island, with overall accretion occurring. In today’s era of intensifying coastal development, the rational layout of coastal engineering is expected to mitigate beach erosion.
In recent decades, the beaches on both sides of the Jiehe River (hereinafter referred to as Jiehe Beach) in the northeastern part of Laizhou Bay have suffered severe erosion against the backdrop of reduced riverine sediment input to the sea. Additionally, the construction of coastal engineering projects such as Yulong Island (a large artificial offshore island) has made the evolution of the Jiehe Beach shoreline exceptionally complex. This paper utilizes
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doi: 10.12284/hyxb2024129
Abstract:
Sediment transport is a fundamental issue in the study of coastal and estuarine environments, holding significant scientific importance and practical value for the evolution of estuarine geomorphology, ecological environment, and engineering construction. This paper takes the estuary of the Moyang River as an example, based on the sea current, wave and suspended sediment concentration data measured by ship and bottom tripod, analyzes the alongshore and cross-shore transport trends of suspended sediment on the fixed cross-section of the Moyang River estuary, and calculates the sediment transport flux. It explores the sediment transport mechanisms and patterns in wave-tidal estuaries, with the main findings including: (1) During the flood season at the river mouth, the sediment transport is mainly controlled by the runoff, with the sediment transport rate increasing as the flow rate increases. The alongshore and cross-shore sediment transport reaches the maximum value during the neap tide with the largest flow, which are 111.9 g/m²/s and 269.5 g/m²/s respectively. At the mouth bar in the flood season, the sediment transport is jointly controlled by waves and tides. The alongshore sediment transport is consistently westward along the coast during both spring and neap tides, while the cross-shore sediment transport is dominated by the ebb tide during the spring tide with an offshore transport of 4.0 g/m²/s, and by waves during the neap tide with an onshore transport of 19.0 g/m²/s.(2) During the dry season, the mouth bar is primarily influenced by tidal currents and wave action. Sediment transport along the vertical shore predominantly occurs due to falling tidal currents moving seaward, while coastal transport is governed by wave energy, resulting in an eastward movement under the influence of wave-generated coastal currents. On the eastern side of the mouth bar during this season, tidal currents and waves also play a significant role; vertical shore transport is mainly driven by rising tides during spring tide periods before transitioning to offshore transport as tidal forces diminish. Coastal transport remains affected by wave-induced coastal currents and continues its eastward trajectory. (3) During the flood season observation period, the offshore transport at the river mouth is significant, and the flow direction of each water layer is consistent vertically. During the neap tide, there is a differentiation in the flow direction of the water layers, with the surface layer transporting offshore and the bottom layer onshore. At the mouth bar, the flow direction of each water layer is relatively consistent vertically during both spring and neap tides. Still, after tidal averaging, the spring tide shows offshore transport in all water layers, while the neap tide shows onshore transport in all water layers. During the neap tide, the influence of waves is evident, with the onshore transport ratio reaching 79%. (4) Under the influence of runoff and tidal current, the mouth of Moyang River estuary mainly carries sediment to the sea. The most significant factors affecting sediment transport at the mouth bar are the seaward tidal currents and the alongshore and cross-shore sediment movements driven by waves.
Sediment transport is a fundamental issue in the study of coastal and estuarine environments, holding significant scientific importance and practical value for the evolution of estuarine geomorphology, ecological environment, and engineering construction. This paper takes the estuary of the Moyang River as an example, based on the sea current, wave and suspended sediment concentration data measured by ship and bottom tripod, analyzes the alongshore and cross-shore transport trends of suspended sediment on the fixed cross-section of the Moyang River estuary, and calculates the sediment transport flux. It explores the sediment transport mechanisms and patterns in wave-tidal estuaries, with the main findings including: (1) During the flood season at the river mouth, the sediment transport is mainly controlled by the runoff, with the sediment transport rate increasing as the flow rate increases. The alongshore and cross-shore sediment transport reaches the maximum value during the neap tide with the largest flow, which are 111.9 g/m²/s and 269.5 g/m²/s respectively. At the mouth bar in the flood season, the sediment transport is jointly controlled by waves and tides. The alongshore sediment transport is consistently westward along the coast during both spring and neap tides, while the cross-shore sediment transport is dominated by the ebb tide during the spring tide with an offshore transport of 4.0 g/m²/s, and by waves during the neap tide with an onshore transport of 19.0 g/m²/s.(2) During the dry season, the mouth bar is primarily influenced by tidal currents and wave action. Sediment transport along the vertical shore predominantly occurs due to falling tidal currents moving seaward, while coastal transport is governed by wave energy, resulting in an eastward movement under the influence of wave-generated coastal currents. On the eastern side of the mouth bar during this season, tidal currents and waves also play a significant role; vertical shore transport is mainly driven by rising tides during spring tide periods before transitioning to offshore transport as tidal forces diminish. Coastal transport remains affected by wave-induced coastal currents and continues its eastward trajectory. (3) During the flood season observation period, the offshore transport at the river mouth is significant, and the flow direction of each water layer is consistent vertically. During the neap tide, there is a differentiation in the flow direction of the water layers, with the surface layer transporting offshore and the bottom layer onshore. At the mouth bar, the flow direction of each water layer is relatively consistent vertically during both spring and neap tides. Still, after tidal averaging, the spring tide shows offshore transport in all water layers, while the neap tide shows onshore transport in all water layers. During the neap tide, the influence of waves is evident, with the onshore transport ratio reaching 79%. (4) Under the influence of runoff and tidal current, the mouth of Moyang River estuary mainly carries sediment to the sea. The most significant factors affecting sediment transport at the mouth bar are the seaward tidal currents and the alongshore and cross-shore sediment movements driven by waves.
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doi: 10.12284/hyxb2024000
Abstract:
In real ocean environments, natural reefs typically exhibit complex topography, with reef platforms presenting non-uniform characteristics. Previous extensive research has mainly focused on simplified stepped reef models and has not conducted in-depth studies on the impact of non-uniform reef platforms on the propagation and evolution characteristics of waves. To address the shortcomings of previous research, this paper conducted physical model experiments to systematically study the propagation and evolution characteristics of tsunami-like waves over complex reef platforms. Previous studies did not consider the impact of the non-uniformity of reef platform topography on solitary waves, therefore, this paper also analyzed the effects of incident wave height and reef platform water depth. To investigate the impact of non-uniform reef platform geometric characteristics on the propagation and evolution of tsunami-like waves and the load characteristics of sea walls under different incident wave conditions, this paper further carried out a series of high-resolution numerical calculations. First, physical experiments were used to verify the accuracy of the numerical simulation method, and then numerical calculations were used to study the effects of two wave parameters, incident wave height and reef platform submergence depth, as well as three complex reef topography factors: the height of the second reef platform, the position of the reef platform steps, and the slope of the reef front slope on the maximum wave height along the path, reflection coefficient, maximum run-up height, distribution of the maximum impact pressure on the sea wall, and the variation of the maximum total force and total moment on the sea wall. The research results indicate that the reflection coefficient of solitary waves decreases with increasing incident wave height and increases with increasing reef platform water depth. The maximum run-up height increases with increasing incident wave height and decreases with increasing cotα of the reef front slope. The maximum total force and maximum total moment on the sea wall increase with increasing incident wave height and reef platform water depth, and decrease with increasing height of the second reef platform. The position of the maximum impact pressure on the sea wall rises with increasing incident wave height, increasing reef platform water depth, and decreasing distance between the reef platform steps and the sea wall. The research results can provide a reference for further protecting coastal facilities from the impact of extreme marine environments.
In real ocean environments, natural reefs typically exhibit complex topography, with reef platforms presenting non-uniform characteristics. Previous extensive research has mainly focused on simplified stepped reef models and has not conducted in-depth studies on the impact of non-uniform reef platforms on the propagation and evolution characteristics of waves. To address the shortcomings of previous research, this paper conducted physical model experiments to systematically study the propagation and evolution characteristics of tsunami-like waves over complex reef platforms. Previous studies did not consider the impact of the non-uniformity of reef platform topography on solitary waves, therefore, this paper also analyzed the effects of incident wave height and reef platform water depth. To investigate the impact of non-uniform reef platform geometric characteristics on the propagation and evolution of tsunami-like waves and the load characteristics of sea walls under different incident wave conditions, this paper further carried out a series of high-resolution numerical calculations. First, physical experiments were used to verify the accuracy of the numerical simulation method, and then numerical calculations were used to study the effects of two wave parameters, incident wave height and reef platform submergence depth, as well as three complex reef topography factors: the height of the second reef platform, the position of the reef platform steps, and the slope of the reef front slope on the maximum wave height along the path, reflection coefficient, maximum run-up height, distribution of the maximum impact pressure on the sea wall, and the variation of the maximum total force and total moment on the sea wall. The research results indicate that the reflection coefficient of solitary waves decreases with increasing incident wave height and increases with increasing reef platform water depth. The maximum run-up height increases with increasing incident wave height and decreases with increasing cotα of the reef front slope. The maximum total force and maximum total moment on the sea wall increase with increasing incident wave height and reef platform water depth, and decrease with increasing height of the second reef platform. The position of the maximum impact pressure on the sea wall rises with increasing incident wave height, increasing reef platform water depth, and decreasing distance between the reef platform steps and the sea wall. The research results can provide a reference for further protecting coastal facilities from the impact of extreme marine environments.
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Abstract:
Abstrart: The streamline construction and placement of the marine flow field is of great significance for recognizing and understanding the marine flow field. In the process of streamline drawing, the selection of integration step is very important, which can directly affect the effect of streamline placement. The fixed step size algorithm is often not used because it cannot adapt to the changing curvature. The previous adaptive step size streamline algorithm has the problems of low degree of freedom and poor multi-scale applicability. In view of the above problems, this paper introduces information entropy into the step size calculation for the first time, and proposes an adaptive step size algorithm of marine streamline controlled by information entropy. Firstly, the entropy field is obtained by calculating the information entropy of the flow field, and then the flow field is divided into high entropy region and low entropy region according to the entropy value, and each integration point is given a new step size, so that the flow field can adaptively adjust the step size according to the intensity of change, that is, the step size of the high entropy region (the region with sharp change) is smaller, and the step size of the low entropy region (the region with gentle change) is larger. The experimental results show that the proposed algorithm can significantly increase the number of integration points and streamlines in the rapidly changing region, better draw the details of the streamline at the feature, and reduce the number of integration points and streamlines in the unimportant region without affecting the placement effect to improve the computational efficiency. Compared with the previous adaptive step size algorithm, the proposed algorithm significantly improves the degree of freedom of step size adjustment and the scale applicability, and can be applied to different scales of marine flow field.
Abstrart: The streamline construction and placement of the marine flow field is of great significance for recognizing and understanding the marine flow field. In the process of streamline drawing, the selection of integration step is very important, which can directly affect the effect of streamline placement. The fixed step size algorithm is often not used because it cannot adapt to the changing curvature. The previous adaptive step size streamline algorithm has the problems of low degree of freedom and poor multi-scale applicability. In view of the above problems, this paper introduces information entropy into the step size calculation for the first time, and proposes an adaptive step size algorithm of marine streamline controlled by information entropy. Firstly, the entropy field is obtained by calculating the information entropy of the flow field, and then the flow field is divided into high entropy region and low entropy region according to the entropy value, and each integration point is given a new step size, so that the flow field can adaptively adjust the step size according to the intensity of change, that is, the step size of the high entropy region (the region with sharp change) is smaller, and the step size of the low entropy region (the region with gentle change) is larger. The experimental results show that the proposed algorithm can significantly increase the number of integration points and streamlines in the rapidly changing region, better draw the details of the streamline at the feature, and reduce the number of integration points and streamlines in the unimportant region without affecting the placement effect to improve the computational efficiency. Compared with the previous adaptive step size algorithm, the proposed algorithm significantly improves the degree of freedom of step size adjustment and the scale applicability, and can be applied to different scales of marine flow field.
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Abstract:
In engineering practice, the Morison equation is commonly used to calculate wave loads on slender structures. Traditionally, the Morison equation for wave force calculation is often simplified, assuming the pile as a rigid body and neglecting the elastic deformation of the pile. By employing the Radial Basis Function (RBF), a mesh-free method, this study simultaneously solves the Morison equation, which considers pile elastic deformation, and the dynamic balance equation. This approach obtains the wave force and dynamic response of a single pile under wave load, and compares the results with those from standard methods and previous literature to validate its accuracy. Applying this method to actual engineering cases reveals the dynamic response of the working platform under the most unfavorable conditions. The RBF method is computationally straightforward and easy to master, making it suitable for practical engineering applications and providing a new direction for the calculation of offshore structures in the future.
In engineering practice, the Morison equation is commonly used to calculate wave loads on slender structures. Traditionally, the Morison equation for wave force calculation is often simplified, assuming the pile as a rigid body and neglecting the elastic deformation of the pile. By employing the Radial Basis Function (RBF), a mesh-free method, this study simultaneously solves the Morison equation, which considers pile elastic deformation, and the dynamic balance equation. This approach obtains the wave force and dynamic response of a single pile under wave load, and compares the results with those from standard methods and previous literature to validate its accuracy. Applying this method to actual engineering cases reveals the dynamic response of the working platform under the most unfavorable conditions. The RBF method is computationally straightforward and easy to master, making it suitable for practical engineering applications and providing a new direction for the calculation of offshore structures in the future.
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Abstract:
Rapid changes in the Arctic environment significantly impact the characteristics of water masses in the Arctic Ocean, potentially affecting the ocean’s physical and biogeochemical processes. This study utilizes the latest MOSAiC observation data (from October 2019 to August 2020) and high-resolution reanalysis data (GLORYS12V1) to analyze the variations in temperature and salinity of water masses across the Eurasian Basin along the MOSAiC drift trajectory, and to explore the influence of the Atlantic inflow on these variations. The results show that: (1) Both temperature and salinity within the upper 100 m layer along the drift trajectory exhibit an overall pattern of initially increasing and then decreasing from the Amundsen Basin to the Nansen Basin. The spatial variation in salinity is greatest within the 0－20 m layer, with highly saline surface water (S >34) present in Nansen Basin. In contrast, the variation in temperature is greatest at the 100 m layer, with the depth of 0℃ isothermal less than 100 m in parts of the Nansen Basin. Although GLORYS12V1 simulates the higher temperature in the upper Nansen Basin, it reasonably captures the main features of horizontal and vertical variations in temperature and salinity along the drift trajectory. (2) The warm and saline Atlantic water generally flows anticlockwise in the Eurasian Basin, with its depth gradually deepening during transport, which predominantly determines the overall variations in temperature and salinity in intermedia and upper layers in the Eurasian Basin. The high salinity of surface water in the Nansen Basin is due to the drift trajectory involved into the regions influenced by deep winter convection in northern Svalbard. Strong wind events play a limited role in the distributional differences of temperature and salinity along the drift trajectory. (3) In the western Nansen Basin, GLORYS12V1 indicates a northward extension of Atlantic Water beyond what is observed, with its northern boundary nearing the Gakkel Ridge. This discrepancy results in an overestimation of temperature compared to in-situ observations. To improve the accuracy of the GLORYS12V1 simulated results, refining the setting of Atlantic inflow flux at the open boundary is suggested.
Rapid changes in the Arctic environment significantly impact the characteristics of water masses in the Arctic Ocean, potentially affecting the ocean’s physical and biogeochemical processes. This study utilizes the latest MOSAiC observation data (from October 2019 to August 2020) and high-resolution reanalysis data (GLORYS12V1) to analyze the variations in temperature and salinity of water masses across the Eurasian Basin along the MOSAiC drift trajectory, and to explore the influence of the Atlantic inflow on these variations. The results show that: (1) Both temperature and salinity within the upper 100 m layer along the drift trajectory exhibit an overall pattern of initially increasing and then decreasing from the Amundsen Basin to the Nansen Basin. The spatial variation in salinity is greatest within the 0－20 m layer, with highly saline surface water (S >34) present in Nansen Basin. In contrast, the variation in temperature is greatest at the 100 m layer, with the depth of 0℃ isothermal less than 100 m in parts of the Nansen Basin. Although GLORYS12V1 simulates the higher temperature in the upper Nansen Basin, it reasonably captures the main features of horizontal and vertical variations in temperature and salinity along the drift trajectory. (2) The warm and saline Atlantic water generally flows anticlockwise in the Eurasian Basin, with its depth gradually deepening during transport, which predominantly determines the overall variations in temperature and salinity in intermedia and upper layers in the Eurasian Basin. The high salinity of surface water in the Nansen Basin is due to the drift trajectory involved into the regions influenced by deep winter convection in northern Svalbard. Strong wind events play a limited role in the distributional differences of temperature and salinity along the drift trajectory. (3) In the western Nansen Basin, GLORYS12V1 indicates a northward extension of Atlantic Water beyond what is observed, with its northern boundary nearing the Gakkel Ridge. This discrepancy results in an overestimation of temperature compared to in-situ observations. To improve the accuracy of the GLORYS12V1 simulated results, refining the setting of Atlantic inflow flux at the open boundary is suggested.
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Abstract:
Iron oxides play a significant role in the global soil (sediment) organic carbon (OC) storage. Mangrove wetlands, receiving both terrestrial and marine inputs, provide a unique habitat for the preservation of organic carbon by reactive iron oxides (FeR). However, the impact of FeR in the surface sediments of mangroves on the preservation process of OC, as well as the selectivity of FeR towards different OC components, is still unclear. The surface sediments in the present work was collected in the natural mangrove areas around the estuaries of the Dafeng River and Maowei Sea in Guangxi, which are highly influenced by tides and rivers. The research was focused on the changes in the content and composition of iron-bound organic carbon (Fe-OC) in sediments. The results indicated that the average content of Fe-OC in surface sediments in the estuaries of Dafeng River and Maowei Sea was 0.16 ± 0.07% and 0.17 ± 0.07%, respectively. These values represented 16.2 ± 5.04% and 10.9 ± 5.63% of the total organic carbon (TOC) content in the respective sediments, which were primarily preserved through adsorption. Furthermore, the preservation of OC by FeR was influenced by the sediment particle size, the content and form of FeR, and the source and composition of TOC. TOC, FeR and Fe-OC were mainly distributed in the smaller grain size sediment fractions. The predominant form of iron in surface sediments was Fe3+, accounting for 87.42% of the total iron, and is relatively higher in high salinity sediments. FeR selectively preserved OC with higher δ13C (stable carbon isotope natural abundance) and aromatic OC. Compared with the Maowei Sea, the proportion of protein-like fluorescent components in Fe-OC of surface sediments from the Dafeng River estuary was higher and the proportion of protein-like fluorescent components increased as the molar ratio of Fe-OC:Fe increased. This study helps to clarify the selective preservation mechanism of OC by FeR in mangrove surface sediments in Guangxi, and deepen our understanding of the preservation process of OC in land-sea interface sediments.
Iron oxides play a significant role in the global soil (sediment) organic carbon (OC) storage. Mangrove wetlands, receiving both terrestrial and marine inputs, provide a unique habitat for the preservation of organic carbon by reactive iron oxides (FeR). However, the impact of FeR in the surface sediments of mangroves on the preservation process of OC, as well as the selectivity of FeR towards different OC components, is still unclear. The surface sediments in the present work was collected in the natural mangrove areas around the estuaries of the Dafeng River and Maowei Sea in Guangxi, which are highly influenced by tides and rivers. The research was focused on the changes in the content and composition of iron-bound organic carbon (Fe-OC) in sediments. The results indicated that the average content of Fe-OC in surface sediments in the estuaries of Dafeng River and Maowei Sea was 0.16 ± 0.07% and 0.17 ± 0.07%, respectively. These values represented 16.2 ± 5.04% and 10.9 ± 5.63% of the total organic carbon (TOC) content in the respective sediments, which were primarily preserved through adsorption. Furthermore, the preservation of OC by FeR was influenced by the sediment particle size, the content and form of FeR, and the source and composition of TOC. TOC, FeR and Fe-OC were mainly distributed in the smaller grain size sediment fractions. The predominant form of iron in surface sediments was Fe3+, accounting for 87.42% of the total iron, and is relatively higher in high salinity sediments. FeR selectively preserved OC with higher δ13C (stable carbon isotope natural abundance) and aromatic OC. Compared with the Maowei Sea, the proportion of protein-like fluorescent components in Fe-OC of surface sediments from the Dafeng River estuary was higher and the proportion of protein-like fluorescent components increased as the molar ratio of Fe-OC:Fe increased. This study helps to clarify the selective preservation mechanism of OC by FeR in mangrove surface sediments in Guangxi, and deepen our understanding of the preservation process of OC in land-sea interface sediments.
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Abstract:
To analysis the suitability of using wind field data for forecasting Pacific saury habitat in the northwest Pacific, this paper use the generalized additive model to fit the habitat suitability index (HSI) for Pacific saury in summer and autumn, based on the Chinese fishery data, environmental data and four types of wind field data included the China-France oceanography satellite (CFOSAT) during June to November in 2019−2020.Result indicates that, (1) Weighted analysis shows distinct seasonal variation of environmental variables on catch per unit effort, with chlorophyll concentration and sea surface temperature having the highest weights in summer and autumn, respectively, while wind speed had the lowest weight and directly proportional to the weight. (2) The average accuracy of the four data in summer and autumn is 68.37% and 76.65%, respectively, and CFOSAT reaching the highest accuracy of 80.94% in autumn. (3) The high-HSI areas are consistent with the fishing grounds of Pacific saury, while the high-value regions of scatter meter in autumn show clear and focus. The advantages of using wind speed on the forecast model in autumn, which can explain the influence of transient variation factors on the migration and aggregation of Pacific saury.
To analysis the suitability of using wind field data for forecasting Pacific saury habitat in the northwest Pacific, this paper use the generalized additive model to fit the habitat suitability index (HSI) for Pacific saury in summer and autumn, based on the Chinese fishery data, environmental data and four types of wind field data included the China-France oceanography satellite (CFOSAT) during June to November in 2019−2020.Result indicates that, (1) Weighted analysis shows distinct seasonal variation of environmental variables on catch per unit effort, with chlorophyll concentration and sea surface temperature having the highest weights in summer and autumn, respectively, while wind speed had the lowest weight and directly proportional to the weight. (2) The average accuracy of the four data in summer and autumn is 68.37% and 76.65%, respectively, and CFOSAT reaching the highest accuracy of 80.94% in autumn. (3) The high-HSI areas are consistent with the fishing grounds of Pacific saury, while the high-value regions of scatter meter in autumn show clear and focus. The advantages of using wind speed on the forecast model in autumn, which can explain the influence of transient variation factors on the migration and aggregation of Pacific saury.
, Available online ,
doi: 10.12284/hyxb2024031
Abstract:
The buried hill oil and gas reservoirs have become an important exploration field in China’s marine basins. The northwestern area of Shaleitian area of Bohai Bay Basin is a typical carbonate buried hill zone. Due to the lack of research on the reservoir control effect of multiple stage fractures and their related karstification, the oil and gas exploration of carbonate buried hills is restricted. This paper conducts a detailed analysis of the development characteristics of the fracture-cave system in carbonate buried hill reservoirs in the northwestern Shaleitian Uplift, and studies the reservoir control effects of fractures and karst. The results indicate that the lower Paleozoic carbonate buried hills in the northwestern area of Shaleitian Uplift belong to fracture related karst reservoirs. The reservoir space includes dissolution pores, structural fractures, and expansion pores along the structural fractures. High quality reservoirs have lithological selectivity, and fractures and dissolution pores developed in microlite crystalline dolomite and fine crystalline dolomite are better. The reservoir mainly develops three sets of fractures, with NW and NEE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian . The third set of WE oriented tensile fractures is related to the intracratonic movement during the Himalayan orogeny, and compression is the main mechanism for forming high-density fractures. The later stage of extension is a necessary condition for the relaxation of fractures to form reservoir spaces. The Lower Paleozoic carbonate buried hill reservoirs have undergone three stages ofkarstification, which are karstification in the steady Caledonian tectonic background, karstification in the Indosinian compressive background, and fault block-horst karstification in the Yanshanian-Himalayan extensional background. In summary, the carbonate buried hill reservoirs in the northwestern Shaleitian Uplift are formed by multiple stages and multiple types of tectonic-karst processes, and the analysis of the differences in the degree of recombination in different structural parts is an important factor in understanding the reservoir formation mechanism.
The buried hill oil and gas reservoirs have become an important exploration field in China’s marine basins. The northwestern area of Shaleitian area of Bohai Bay Basin is a typical carbonate buried hill zone. Due to the lack of research on the reservoir control effect of multiple stage fractures and their related karstification, the oil and gas exploration of carbonate buried hills is restricted. This paper conducts a detailed analysis of the development characteristics of the fracture-cave system in carbonate buried hill reservoirs in the northwestern Shaleitian Uplift, and studies the reservoir control effects of fractures and karst. The results indicate that the lower Paleozoic carbonate buried hills in the northwestern area of Shaleitian Uplift belong to fracture related karst reservoirs. The reservoir space includes dissolution pores, structural fractures, and expansion pores along the structural fractures. High quality reservoirs have lithological selectivity, and fractures and dissolution pores developed in microlite crystalline dolomite and fine crystalline dolomite are better. The reservoir mainly develops three sets of fractures, with NW and NEE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian . The third set of WE oriented tensile fractures is related to the intracratonic movement during the Himalayan orogeny, and compression is the main mechanism for forming high-density fractures. The later stage of extension is a necessary condition for the relaxation of fractures to form reservoir spaces. The Lower Paleozoic carbonate buried hill reservoirs have undergone three stages ofkarstification, which are karstification in the steady Caledonian tectonic background, karstification in the Indosinian compressive background, and fault block-horst karstification in the Yanshanian-Himalayan extensional background. In summary, the carbonate buried hill reservoirs in the northwestern Shaleitian Uplift are formed by multiple stages and multiple types of tectonic-karst processes, and the analysis of the differences in the degree of recombination in different structural parts is an important factor in understanding the reservoir formation mechanism.
, Available online
Abstract:
Submarine fans developed in the middle Miocene Meishan formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores reveal the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibit good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.
Submarine fans developed in the middle Miocene Meishan formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores reveal the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibit good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.
, Available online
Abstract:
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
, Available online
Abstract:
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
, Available online
Abstract:
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
Display Method:
2024, 46(10): 1-15.
doi: 10.12284/hyxb2024093
Abstract:
Under the backdrop of climate change, mass sea level change rates are varied across regions. Therein, under the combined effect of the self-attraction and loading effect and polar motion feedback, freshwater transported from land to sea resulted in the spatiotemporal heterogeneous change of mass sea level, termed sea level fingerprints. The sea level fingerprints are important components of mass sea level. This study utilized three terrestrial water storage anomalies datasets to simulate sea level fingerprints under three scenarios, following a sea level equation that incorporated the self-attraction and loading effect along with polar motion feedback. The simulated scenarios were: (1) aligning with the actual glacial mass balance; (2) consistent with the recent climate change rates; (3) considering climate natural variability alone. Based on simulation results, this study analyzed the evolution ofsea level fingerprints under multiple scenarios and assessed their contribution to observed mass sea level anomalies. The study revealed that glacier melting in regions such as Greenland, Alaska, the Caucasus and Middle East, the Southern Andes, and Antarctica dominated the trend term of sea level fingerprints. The sea level fingerprints, which align with the actual glacier mass balance, better replicated the global distribution pattern of the observed mass sea level anomalies trend term, as shown by the spatial similarity coefficients of 0.31 with the GRACE/GRACE-FO results and 0.71 with the altimetry satellite results. Non-glacial regional terrestrial water storage anomalies better captured the amplitude term of the observed mass sea level anomalies, as shown by sea level fingerprints, which consider climate natural variability alone, having spatial similarity coefficients of 0.67 with the GRACE/GRACE-FO results and 0.84 with the altimetry satellite results. The sea level fingerprints were the primary contributing source to mass sea level anomalies in low-latitude regions.
Under the backdrop of climate change, mass sea level change rates are varied across regions. Therein, under the combined effect of the self-attraction and loading effect and polar motion feedback, freshwater transported from land to sea resulted in the spatiotemporal heterogeneous change of mass sea level, termed sea level fingerprints. The sea level fingerprints are important components of mass sea level. This study utilized three terrestrial water storage anomalies datasets to simulate sea level fingerprints under three scenarios, following a sea level equation that incorporated the self-attraction and loading effect along with polar motion feedback. The simulated scenarios were: (1) aligning with the actual glacial mass balance; (2) consistent with the recent climate change rates; (3) considering climate natural variability alone. Based on simulation results, this study analyzed the evolution ofsea level fingerprints under multiple scenarios and assessed their contribution to observed mass sea level anomalies. The study revealed that glacier melting in regions such as Greenland, Alaska, the Caucasus and Middle East, the Southern Andes, and Antarctica dominated the trend term of sea level fingerprints. The sea level fingerprints, which align with the actual glacier mass balance, better replicated the global distribution pattern of the observed mass sea level anomalies trend term, as shown by the spatial similarity coefficients of 0.31 with the GRACE/GRACE-FO results and 0.71 with the altimetry satellite results. Non-glacial regional terrestrial water storage anomalies better captured the amplitude term of the observed mass sea level anomalies, as shown by sea level fingerprints, which consider climate natural variability alone, having spatial similarity coefficients of 0.67 with the GRACE/GRACE-FO results and 0.84 with the altimetry satellite results. The sea level fingerprints were the primary contributing source to mass sea level anomalies in low-latitude regions.
2024, 46(10): 16-24.
doi: 10.12284/hyxb2024095
Abstract:
Based on the stratification characteristics of the South China Sea and the finite depth theoretical equation, the two-dimensional sound velocity field under different amplitudes of soliton internal waves is reconstructed by using the temperature and salinity data measured by submersible moorings and WOA2023 climate states. Combined with the BELLHOP ray acoustic model, the sound propagation loss, the ray path, the sound ray arrival structure and so on are simulated under different sound speed environment. The simulation results show that soliton internal waves will change the propagation path of the sound rays. When the sound rays pass through the center of internal wave from the sea surface to the sea bottom or from the sea bottom to the sea surface, the horizontal direction of the sound rays track will be offset towards the sound source and away from the sound source, respectively. The larger the amplitude of soliton internal wave, the larger the offset distance of the sound rays track. Soliton internal waves can also change the arrival structure of the sound rays, and the sound signal will propagate to the receiving point faster when there are soliton internal wave conditions at a specific receiving point.
Based on the stratification characteristics of the South China Sea and the finite depth theoretical equation, the two-dimensional sound velocity field under different amplitudes of soliton internal waves is reconstructed by using the temperature and salinity data measured by submersible moorings and WOA2023 climate states. Combined with the BELLHOP ray acoustic model, the sound propagation loss, the ray path, the sound ray arrival structure and so on are simulated under different sound speed environment. The simulation results show that soliton internal waves will change the propagation path of the sound rays. When the sound rays pass through the center of internal wave from the sea surface to the sea bottom or from the sea bottom to the sea surface, the horizontal direction of the sound rays track will be offset towards the sound source and away from the sound source, respectively. The larger the amplitude of soliton internal wave, the larger the offset distance of the sound rays track. Soliton internal waves can also change the arrival structure of the sound rays, and the sound signal will propagate to the receiving point faster when there are soliton internal wave conditions at a specific receiving point.
2024, 46(10): 25-36.
doi: 10.12284/hyxb2024105
Abstract:
The real-time changes of the internal water structure accompanied by the evolution of eddies have always been one of the important influencing factors to further study the ecological effects of mesoscale eddies. In this paper, three eddies in the Kuroshio-Oyashio confluence region are taken as examples. Based on satellite altimeter and Argo profile data, the gradient-dependent optimal interpolation method is used to construct the real-time internal structures of eddies. The reliability and effectiveness of this method in constructing the real-time structures of eddies are systematically evaluated through comparison with satellite observation, in-situ data and numerical simulation data. The results show that the orders of magnitude for the reconstructed surface geostrophic current of three eddies are consistent with satellite altimetry. Compared with the in-situ data of the ADCP (Acoustic Doppler Current Profiler, ADCP), it is found that the locations of the eddy centers are coincident with the velocity turning position of the ADCP observed sections. The fluctuation shapes and amplitudes of the isodensity lines of the three eddies are consistent with the XCTD (Expendable Conductivity-Temperature-Depth, XCTD) observations. In addition, the eddy center and mean radius of the numerical output are basically consistent with the constructed ones. Therefore, the gradient-dependent OI was a hopeful technique for representing the real-time internal features during eddy evolution.
The real-time changes of the internal water structure accompanied by the evolution of eddies have always been one of the important influencing factors to further study the ecological effects of mesoscale eddies. In this paper, three eddies in the Kuroshio-Oyashio confluence region are taken as examples. Based on satellite altimeter and Argo profile data, the gradient-dependent optimal interpolation method is used to construct the real-time internal structures of eddies. The reliability and effectiveness of this method in constructing the real-time structures of eddies are systematically evaluated through comparison with satellite observation, in-situ data and numerical simulation data. The results show that the orders of magnitude for the reconstructed surface geostrophic current of three eddies are consistent with satellite altimetry. Compared with the in-situ data of the ADCP (Acoustic Doppler Current Profiler, ADCP), it is found that the locations of the eddy centers are coincident with the velocity turning position of the ADCP observed sections. The fluctuation shapes and amplitudes of the isodensity lines of the three eddies are consistent with the XCTD (Expendable Conductivity-Temperature-Depth, XCTD) observations. In addition, the eddy center and mean radius of the numerical output are basically consistent with the constructed ones. Therefore, the gradient-dependent OI was a hopeful technique for representing the real-time internal features during eddy evolution.
2024, 46(10): 37-49.
doi: 10.12284/hyxb2024101
Abstract:
Both the southeastern tropical Indian Ocean and the northern South China Sea are similar in topography and background circulation characteristics, and both have active mesoscale eddy motion. Based on satellite altimeter data, the seasonal and interannual variations of mesoscale eddies in these two sea areas are compared. The results show that the number of mesoscale eddies generated in the southeastern tropical Indian Ocean and the northern South China Sea decay exponentially with the growth of their life time. Mesoscale eddies in these two sea areas move to the west or southwest with an average speed of 0.2 m/s, but the average radius of the former is larger and the average amplitude of the latter is stronger. In terms of seasonal variation, the eddy kinetic energy is smallest in spring and largest in autumn in the northern hemisphere, but the eddy generation number in the southeastern tropical Indian Ocean is largest in summer-autumn and the northern South China Sea is largest in winter-spring. In interannual variation, the eddy activity in the southeastern tropical Indian Ocean and the northern South China Sea is affected by El Niño-Southern Oscillation (ENSO). The eddy kinetic energy is stronger in El Niño year and weaker in La Niña year, but the mechanism of ENSO affecting the mesoscale eddy in these two areas is slightly different. The former is mainly achieved by modulating Indonesian Throughflow to suppress or enhance the baroclinic instability energy in this area, while the latter is mainly achieved by changing the local wind field in the northern South China Sea to produce wind stress curl anomaly. In addition, the mesoscale eddy in the southeastern tropical Indian Ocean is also affected by the Indian Ocean Dipole, while the correlation between the mesoscale eddy in the northern South China Sea and the Indian Ocean Dipole is weak.
Both the southeastern tropical Indian Ocean and the northern South China Sea are similar in topography and background circulation characteristics, and both have active mesoscale eddy motion. Based on satellite altimeter data, the seasonal and interannual variations of mesoscale eddies in these two sea areas are compared. The results show that the number of mesoscale eddies generated in the southeastern tropical Indian Ocean and the northern South China Sea decay exponentially with the growth of their life time. Mesoscale eddies in these two sea areas move to the west or southwest with an average speed of 0.2 m/s, but the average radius of the former is larger and the average amplitude of the latter is stronger. In terms of seasonal variation, the eddy kinetic energy is smallest in spring and largest in autumn in the northern hemisphere, but the eddy generation number in the southeastern tropical Indian Ocean is largest in summer-autumn and the northern South China Sea is largest in winter-spring. In interannual variation, the eddy activity in the southeastern tropical Indian Ocean and the northern South China Sea is affected by El Niño-Southern Oscillation (ENSO). The eddy kinetic energy is stronger in El Niño year and weaker in La Niña year, but the mechanism of ENSO affecting the mesoscale eddy in these two areas is slightly different. The former is mainly achieved by modulating Indonesian Throughflow to suppress or enhance the baroclinic instability energy in this area, while the latter is mainly achieved by changing the local wind field in the northern South China Sea to produce wind stress curl anomaly. In addition, the mesoscale eddy in the southeastern tropical Indian Ocean is also affected by the Indian Ocean Dipole, while the correlation between the mesoscale eddy in the northern South China Sea and the Indian Ocean Dipole is weak.
2024, 46(10): 50-64.
doi: 10.12284/hyxb2024099
Abstract:
Due to global warming, a significant amount of multi-year ice(MYI) has been replaced by seasonal ice in recent years. In this study, the multi-year ice flux of representative sections(Northern Beaufort (NB) section, W150° Section, Eastern Chukchi (EC) Section and Central Arctic (CA) Section) of the Arctic Ocean is calculated based on ice age, ice concentration and ice velocity data. The main factors affecting ice fluxes at each section from 1984 to 2021 were investigated in the context of atmospheric reanalysis data. The occurrence time and reasons for theMYI transport interruptions were analyzed. The results show that the weakening of the Beaufort High (BH) corresponds to a reduction in MYI transport in the NB section and an increase in the CA Section along Transpolar Drift region. During the negative phase of the Arctic Dipole (DA), the anticyclonic wind field weak, which reduced the south winds in East Siberia, leading to a decrease in the MYI flux in the EC Section. The decrease in meridional wind has reduced the flux in the CA Section. However, after 2004, the correlation between sea ice flux in the Beaufort gyre region and the Transpolar drift region sections with the DA index decreased. This is mainly due to the continuous contraction of the MYI extent, which has resulted in a decreasing trend in section and even interruptions. The contraction also changes the periodicity of the MYI flux. At the same time, interannual variations of ice velocity can also cause interruptions of multi-year ice transport in the Beaufort gyre. The results indicate that interruptions usually occur during the negative phase periods of the BH index and DA index. However, it is noteworthy that not all months with BH and DA index below the negative standard deviation correspond to the time oftransport interruption. When an interruption occurs, the wind field anomaly center is closer to the North Pole than in the normal of the negative phase of the BH. Furthermore, the spatial distribution of positive and negative sea level pressure anomalies is more symmetrical, compared to the normal negative phase of the DA.
Due to global warming, a significant amount of multi-year ice(MYI) has been replaced by seasonal ice in recent years. In this study, the multi-year ice flux of representative sections(Northern Beaufort (NB) section, W150° Section, Eastern Chukchi (EC) Section and Central Arctic (CA) Section) of the Arctic Ocean is calculated based on ice age, ice concentration and ice velocity data. The main factors affecting ice fluxes at each section from 1984 to 2021 were investigated in the context of atmospheric reanalysis data. The occurrence time and reasons for theMYI transport interruptions were analyzed. The results show that the weakening of the Beaufort High (BH) corresponds to a reduction in MYI transport in the NB section and an increase in the CA Section along Transpolar Drift region. During the negative phase of the Arctic Dipole (DA), the anticyclonic wind field weak, which reduced the south winds in East Siberia, leading to a decrease in the MYI flux in the EC Section. The decrease in meridional wind has reduced the flux in the CA Section. However, after 2004, the correlation between sea ice flux in the Beaufort gyre region and the Transpolar drift region sections with the DA index decreased. This is mainly due to the continuous contraction of the MYI extent, which has resulted in a decreasing trend in section and even interruptions. The contraction also changes the periodicity of the MYI flux. At the same time, interannual variations of ice velocity can also cause interruptions of multi-year ice transport in the Beaufort gyre. The results indicate that interruptions usually occur during the negative phase periods of the BH index and DA index. However, it is noteworthy that not all months with BH and DA index below the negative standard deviation correspond to the time oftransport interruption. When an interruption occurs, the wind field anomaly center is closer to the North Pole than in the normal of the negative phase of the BH. Furthermore, the spatial distribution of positive and negative sea level pressure anomalies is more symmetrical, compared to the normal negative phase of the DA.
2024, 46(10): 65-75.
doi: 10.12284/hyxb2024103
Abstract:
Pore structure is an important mesoscopic feature of sea ice affecting its mechanical properties. In order to investigate the mesoscopic structure of melting sea ice, a sea ice block was collected during severe ice period in the Bohai Sea. The ice block was put in a low temperature environment (−1.0℃) for 48 h, which was then observed using a CT scanner. The thresholds of CT values between air, ice and brine were set to −310 HU and −30 HU for segmentation of the CT image, respectively. The air and brine pores were able to be identified in the CT image, and the two-dimensional morphological characteristics of the pores in ice were analyzed. On the basis of image segmentation, the three-dimensional reconstruction of the ice pores was carried out, and the three-dimensional morphological characteristics of the pores were analyzed. It was found that along the ice thickness, the air area fraction was 5.00%～35.93%, and the brine distribution was discontinuous with maximum area fraction of 0.06%. The cross-sectional shape of the air and brine pores parallel to the ice surface was approximately circular, with a roundness more than 0.60. The equivalent circle diameter of air pore was 1.1～3.2 mm, and that of brine was 0.2～2.0 mm. The equivalent circle diameter of pores was positively correlated with the area fraction and negatively correlated with the roundness. In terms of three-dimensional structure, 4 types of air pores were divided according to sphericity (Rsph) into coronary pores (Rsph ≤ 0.25), irregular pores (0.25 < Rsph ≤ 0.45), strip pores (0.45 < Rsph ≤ 0.60), and spherical bubbles (0.60 < Rsph ≤ 1.00). The coronary pore was the largest (average volume (11522.8 ± 5610.2 ) mm3) with smallest amount, and the spherical bubble was the smallest (average diameter (2.0 ± 1.1) mm) with the largest amount. The brine pores were divided into brine channels (0.45 < Rsph ≤ 0.60) and brine cells (0.60 < Rsph ≤ 1.00). The average length of the brine channel was (17.1 ± 12.1) mm, and the average diameter of the brine cell was (1.5 ± 0.9) mm. The amount of brine channels was less, but the volume proportion was comparable to that of brine cells.
Pore structure is an important mesoscopic feature of sea ice affecting its mechanical properties. In order to investigate the mesoscopic structure of melting sea ice, a sea ice block was collected during severe ice period in the Bohai Sea. The ice block was put in a low temperature environment (−1.0℃) for 48 h, which was then observed using a CT scanner. The thresholds of CT values between air, ice and brine were set to −310 HU and −30 HU for segmentation of the CT image, respectively. The air and brine pores were able to be identified in the CT image, and the two-dimensional morphological characteristics of the pores in ice were analyzed. On the basis of image segmentation, the three-dimensional reconstruction of the ice pores was carried out, and the three-dimensional morphological characteristics of the pores were analyzed. It was found that along the ice thickness, the air area fraction was 5.00%～35.93%, and the brine distribution was discontinuous with maximum area fraction of 0.06%. The cross-sectional shape of the air and brine pores parallel to the ice surface was approximately circular, with a roundness more than 0.60. The equivalent circle diameter of air pore was 1.1～3.2 mm, and that of brine was 0.2～2.0 mm. The equivalent circle diameter of pores was positively correlated with the area fraction and negatively correlated with the roundness. In terms of three-dimensional structure, 4 types of air pores were divided according to sphericity (Rsph) into coronary pores (Rsph ≤ 0.25), irregular pores (0.25 < Rsph ≤ 0.45), strip pores (0.45 < Rsph ≤ 0.60), and spherical bubbles (0.60 < Rsph ≤ 1.00). The coronary pore was the largest (average volume (
2024, 46(10): 76-87.
doi: 10.12284/hyxb2024121
Abstract:
In recent decades, a newly formed sand bar has developed at the entrance to the North Branch of the Changjiang Estuary, gradually accumulating sediment and showing signs of blocking the entrance to the North Branch. Understanding the hydrodynamics and sediment transport in the North Branch after the formation of the Xinjiangxin Shoal can help to further identify the trend of channel evolution. Based on the synchronised water-sediment observation data from several stations along the North Branch during flood season and dry season in January and August 2023, the analysis shows that: (1) The water dynamics in the flood season is stronger than that in the dry season, the water dynamics in the North Branch is stronger than that in the branch point. In the dry season, the water dynamics in the lower part is strong, and that in the middle and upper part is weak. The situation is reversed in the flood saeson. (2) The suspended sediment concentration near the Xinjiangxin Shoal is low, that in the North Branch is high. The suspended sediment concentration along the river gradually increases and then decreases spatially. The suspended sediment concentration in the flood season is significantly greater than that in the dry season. (3) The sediment transport in the North Branch is greater than that near the Xinjiangxin Shoal, and the exchange intensity between the Xinjiangxin Shoal and the surrounding waters is small. (4) With the influence of human activities, the narrow and shallow North Branch intensified the sedimentation and development of the Xinjiangxin Shoal, and the North Branch with high turbidity provided rich material sources for the development of the Xinjiangxin Shoal, and the phase difference of the upflowing tide to the branch point of the North Branch and South Branch provided dynamic conditions for the sedimentation of the Xinjiangxin Shoal, explaining the sediment source and dynamic mechanism of the Xinjiangxin Shoal. The understanding of the hydrodynamics and sediment transport can provide the basis for the treatment of the North Branch.
In recent decades, a newly formed sand bar has developed at the entrance to the North Branch of the Changjiang Estuary, gradually accumulating sediment and showing signs of blocking the entrance to the North Branch. Understanding the hydrodynamics and sediment transport in the North Branch after the formation of the Xinjiangxin Shoal can help to further identify the trend of channel evolution. Based on the synchronised water-sediment observation data from several stations along the North Branch during flood season and dry season in January and August 2023, the analysis shows that: (1) The water dynamics in the flood season is stronger than that in the dry season, the water dynamics in the North Branch is stronger than that in the branch point. In the dry season, the water dynamics in the lower part is strong, and that in the middle and upper part is weak. The situation is reversed in the flood saeson. (2) The suspended sediment concentration near the Xinjiangxin Shoal is low, that in the North Branch is high. The suspended sediment concentration along the river gradually increases and then decreases spatially. The suspended sediment concentration in the flood season is significantly greater than that in the dry season. (3) The sediment transport in the North Branch is greater than that near the Xinjiangxin Shoal, and the exchange intensity between the Xinjiangxin Shoal and the surrounding waters is small. (4) With the influence of human activities, the narrow and shallow North Branch intensified the sedimentation and development of the Xinjiangxin Shoal, and the North Branch with high turbidity provided rich material sources for the development of the Xinjiangxin Shoal, and the phase difference of the upflowing tide to the branch point of the North Branch and South Branch provided dynamic conditions for the sedimentation of the Xinjiangxin Shoal, explaining the sediment source and dynamic mechanism of the Xinjiangxin Shoal. The understanding of the hydrodynamics and sediment transport can provide the basis for the treatment of the North Branch.
2024, 46(10): 88-96.
doi: 10.12284/hyxb2024113
Abstract:
As a natural barrier to the coast, coral reefs have been irreversible damaged in recent years due to the influence of human activities. How to resist the erosion of extreme waves has become an urgent problem for islands that have lost their natural barriers. Based on the physical model test of wave flume, this paper studies the complex hydrodynamic characteristics of solitary waves near coral reef topography from the parameters of incident wave height, reef flat water depth and pore radius, and reveals the wave dissipation mechanism of artificial reefs from the perspective of energy. The test results show that the permeable trapezoidal reef can weaken the wave energy and advance the wave breaking position. Under the influence of the reef, the wave is partially reduced after passing through the reef, and the effective water depth of the subsequent propagation on the reef flat can be reduced. The transmission coefficient and reflection coefficient increase with the increase of incident wave height. With the increase of reef flat water depth, the reflection coefficient decreases and the transmission coefficient increases. The reflection coefficient decreases with the increase of pore radius, and the transmission coefficient has no obvious law. The permeable trapezoidal reef can effectively reduce the transmission intensity of waves and realize the protection of islands. The permeable trapezoidal reef can not only weaken the wave energy, but also take into account the ecological friendliness, reduce the force of structures and provide space for water exchange.
As a natural barrier to the coast, coral reefs have been irreversible damaged in recent years due to the influence of human activities. How to resist the erosion of extreme waves has become an urgent problem for islands that have lost their natural barriers. Based on the physical model test of wave flume, this paper studies the complex hydrodynamic characteristics of solitary waves near coral reef topography from the parameters of incident wave height, reef flat water depth and pore radius, and reveals the wave dissipation mechanism of artificial reefs from the perspective of energy. The test results show that the permeable trapezoidal reef can weaken the wave energy and advance the wave breaking position. Under the influence of the reef, the wave is partially reduced after passing through the reef, and the effective water depth of the subsequent propagation on the reef flat can be reduced. The transmission coefficient and reflection coefficient increase with the increase of incident wave height. With the increase of reef flat water depth, the reflection coefficient decreases and the transmission coefficient increases. The reflection coefficient decreases with the increase of pore radius, and the transmission coefficient has no obvious law. The permeable trapezoidal reef can effectively reduce the transmission intensity of waves and realize the protection of islands. The permeable trapezoidal reef can not only weaken the wave energy, but also take into account the ecological friendliness, reduce the force of structures and provide space for water exchange.
2024, 46(10): 97-106.
doi: 10.12284/hyxb2024109
Abstract:
A method for the fast calculation of steadily progressing periodic waves by using parameterized expressions is presented. The free surface elevation of steady periodic water waves is approximated by ABR triangular series, and the nonlinear parameter in ABR series is obtained by a numerical calculation of the free surface boundary conditions. The advantage of using ABR series is that it is simple in form and contains only one parameter, so it is convenient to study the relationship between this parameter and wave parameters, and then to estimate the wave free surface elevation. For conditions of different wave theories applying (Stokes wave theory and cnoidal wave theory), the results calculated by the new method are compared with the analytical solutions of Stokes wave theory, cnoidal wave theory, and the numerical solutions given by the Fourier method, and the applicability of the results calculated by the new numerical method is discussed. In addition, the expressions of the nonlinear parameter in the ABR series determined by the wave steepness (in deep water) or the Ursell number (in non-deep water) are given in order to efficiently predict free surface elevations by means of local wave parameters. Finally, the method of calculating time averaged sand transport rates related to wave nonlinearity by using free surface elevation is given for practical engineering applications.
A method for the fast calculation of steadily progressing periodic waves by using parameterized expressions is presented. The free surface elevation of steady periodic water waves is approximated by ABR triangular series, and the nonlinear parameter in ABR series is obtained by a numerical calculation of the free surface boundary conditions. The advantage of using ABR series is that it is simple in form and contains only one parameter, so it is convenient to study the relationship between this parameter and wave parameters, and then to estimate the wave free surface elevation. For conditions of different wave theories applying (Stokes wave theory and cnoidal wave theory), the results calculated by the new method are compared with the analytical solutions of Stokes wave theory, cnoidal wave theory, and the numerical solutions given by the Fourier method, and the applicability of the results calculated by the new numerical method is discussed. In addition, the expressions of the nonlinear parameter in the ABR series determined by the wave steepness (in deep water) or the Ursell number (in non-deep water) are given in order to efficiently predict free surface elevations by means of local wave parameters. Finally, the method of calculating time averaged sand transport rates related to wave nonlinearity by using free surface elevation is given for practical engineering applications.
2024, 46(10): 107-116.
doi: 10.12284/hyxb2024089
Abstract:
With the impact of climate change such as rising sea levels and intensified storms, it is particularly important to quickly and accurately predict typhoon wave heights for coastal protection and marine disaster prevention. This article first generates a large number of virtual typhoons based on the TCWiSE model, uses the SWAN numerical model to calculate the significant wave height at the observation station during the typhoon, and constructs a sample database of typhoon waves; then evaluates and selects the input factors and hyperparameters of the BO-LSTM neural network model, and trains and tests it using a sample database. The results show that the constructed virtual typhoon has good similarity with historical typhoons, which can provide sufficient data basis for the construction of intelligent typhoon wave height prediction models. The BO-LSTM model built can quickly achieve intelligent prediction of typhoon wave height at a single station, and has prediction accuracy comparable to SWAN. Its prediction accuracy in long-term forecasting scenarios is significantly better than RF and BPNN models. Adding future typhoon data to the input of the BO-LSTM model further improves the accuracy and duration of the model’s forecast. Its Bias, RMSE and R2 for predicting the next 24 h are −0.102 m, 0.494 m and 0.855, respectively. The research results provide a feasible approach for intelligent forecasting of typhoon waves under extreme weather conditions.
With the impact of climate change such as rising sea levels and intensified storms, it is particularly important to quickly and accurately predict typhoon wave heights for coastal protection and marine disaster prevention. This article first generates a large number of virtual typhoons based on the TCWiSE model, uses the SWAN numerical model to calculate the significant wave height at the observation station during the typhoon, and constructs a sample database of typhoon waves; then evaluates and selects the input factors and hyperparameters of the BO-LSTM neural network model, and trains and tests it using a sample database. The results show that the constructed virtual typhoon has good similarity with historical typhoons, which can provide sufficient data basis for the construction of intelligent typhoon wave height prediction models. The BO-LSTM model built can quickly achieve intelligent prediction of typhoon wave height at a single station, and has prediction accuracy comparable to SWAN. Its prediction accuracy in long-term forecasting scenarios is significantly better than RF and BPNN models. Adding future typhoon data to the input of the BO-LSTM model further improves the accuracy and duration of the model’s forecast. Its Bias, RMSE and R2 for predicting the next 24 h are −0.102 m, 0.494 m and 0.855, respectively. The research results provide a feasible approach for intelligent forecasting of typhoon waves under extreme weather conditions.
2024, 46(10): 117-128.
doi: 10.12284/hyxb2024097
Abstract:
The sea ice in Bohai Sea in winter affects the safety production activities of oil platform and ship navigation, as well as the safety of offshore engineering and construction. Spaceborne SAR is not affected by weather and has high resolution, which can be used for sea ice disaster monitoring in Bohai Sea. Based on deep learning model UNet++, this paper introduces Convolutional attention module (CBAM) and uses cross loss function to optimize the model, and establishes a high-precision sea ice detection model for Sentinel-1 SAR data in the Liaodong Bay (AUNet++). And it is compared with PSPNet, Deeplabv3+, DAU-Net and other deep learning methods. The experimental results show that AUNet++ sea ice detection method achieves 97.56%, 97.53%, 95.19% and 95.07% in OA, AA, MIoU and Kappa coefficients, respectively, which is superior to other deep learning methods. This method can extract accurate sea ice information from sea ice edge and smooth ice surface under the interference of high wind speed, and can provide technical support for large-scale and high-precision sea ice detection in Liaodong Bay area.
The sea ice in Bohai Sea in winter affects the safety production activities of oil platform and ship navigation, as well as the safety of offshore engineering and construction. Spaceborne SAR is not affected by weather and has high resolution, which can be used for sea ice disaster monitoring in Bohai Sea. Based on deep learning model UNet++, this paper introduces Convolutional attention module (CBAM) and uses cross loss function to optimize the model, and establishes a high-precision sea ice detection model for Sentinel-1 SAR data in the Liaodong Bay (AUNet++). And it is compared with PSPNet, Deeplabv3+, DAU-Net and other deep learning methods. The experimental results show that AUNet++ sea ice detection method achieves 97.56%, 97.53%, 95.19% and 95.07% in OA, AA, MIoU and Kappa coefficients, respectively, which is superior to other deep learning methods. This method can extract accurate sea ice information from sea ice edge and smooth ice surface under the interference of high wind speed, and can provide technical support for large-scale and high-precision sea ice detection in Liaodong Bay area.
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