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The dynamics of microplastic pollution in coastal zones, in the context of climate change, is a crucial global environmental issue. This study investigated and analyzed changes in microplastic abundance, composition, and diversity in beach sediments in Xiamen City before and after Typhoon "Haikui." The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon "Haikui" was 251.5 ± 27.9 n·kg−1, which significantly decreased to 127.0 ± 18.8 n·kg−1 post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches exhibited distinct variations. 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 the Pielou's evenness index increased. Based on the results of this study and previous research, it is concluded that heavy rainfall is the driving factor behind the changes in microplastic abundance and composition on Xiamen's beaches caused by Typhoon "Haikui." The impact of typhoons on the dynamics of microplastic pollution in coastal zones results from the coupling of multiple physical processes, influenced by a complex combination of factors, such as dynamic conditions, sediment physical and chemical factors, and topography. In the future, it will be necessary to conduct long-term monitoring of hydrological and meteorological data, and to carry out more in-depth, systematic, and comprehensive research on the underlying mechanisms.
The dynamics of microplastic pollution in coastal zones, in the context of climate change, is a crucial global environmental issue. This study investigated and analyzed changes in microplastic abundance, composition, and diversity in beach sediments in Xiamen City before and after Typhoon "Haikui." The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon "Haikui" was 251.5 ± 27.9 n·kg−1, which significantly decreased to 127.0 ± 18.8 n·kg−1 post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches exhibited distinct variations. 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 the Pielou's evenness index increased. Based on the results of this study and previous research, it is concluded that heavy rainfall is the driving factor behind the changes in microplastic abundance and composition on Xiamen's beaches caused by Typhoon "Haikui." The impact of typhoons on the dynamics of microplastic pollution in coastal zones results from the coupling of multiple physical processes, influenced by a complex combination of factors, such as dynamic conditions, sediment physical and chemical factors, and topography. In the future, it will be necessary to conduct long-term monitoring of hydrological and meteorological data, and to carry out more in-depth, systematic, and comprehensive research on the underlying mechanisms.
, Available online ,
doi: 10.12284/hyxb2025032
Abstract:
Based on observations in the Bohai Sea (BS) and North Yellow Sea (NYS) obtained during the late summer and early autumn of 2021, the hypoxic characteristics and influencing factors were explored by analyzing the spatial patterns of temperature, salinity, density, dissolved oxygen (DO) and nutrients, revealing the regulation mechanisms of hydro-biogeochemical processes on the distributions of DO and hypoxia. A narrow hypoxic zone (with the minimum DO mass concentration of 2.18 mg/L) in a southwest-northeast orientation, which was characterized by a high apparent oxygen consumption (AOU) (＞4 mg/L), was observed within the bottom cold water-dominated region in the western BS; a low-DO area with a small scope existed in the northeastern region off the Bohai Bay mouth at 10-m layer. DO concentrations in the NYS were overall higher than that in the BS, and a relatively high DO level was maintained within the Bottom Cold Water Mass (BCWM) in the central NYS, although there was a high AOU (＞2.5 mg/L). The low-lying topography and higher stratification intensity within the bottom cold water-dominated region in the western BS provided the basis for the formation and maintenance of bottom hypoxia, and the fronts around this cold water significantly controlled the boundary and extension scope of the hypoxic zone. The low-DO area at 10-m layer in the northeastern region off the Bohai Bay mouth was caused by the uplift of the hypoxic cold water from the bottom. The presence of an anticyclonic eddy in the shallow bank of the central BS led to the formation of a DO-rich water (＞6 mg/L) at bottom. The decomposition of organic matter and related oxygen consumption in the context of stratification was an important material basis for the formation of hypoxia in the western BS, exactly corresponding to a high-nutrient area at bottom layer. In contrast, due to the higher background levels of DO within the BCWM and the lower AOU than that in the bottom layer of the western BS, it was difficult to form hypoxia in the central NYS even under the relatively high stratification strength; moreover, the deeper water depth was another factor responsible for this situation. This study could provide a scientific basis for understanding the multi-scale variations and regulation of DO in the BS and the NYS, laying a foundation for the subsequent refined simulation and prediction of hypoxia in this sea area.
Based on observations in the Bohai Sea (BS) and North Yellow Sea (NYS) obtained during the late summer and early autumn of 2021, the hypoxic characteristics and influencing factors were explored by analyzing the spatial patterns of temperature, salinity, density, dissolved oxygen (DO) and nutrients, revealing the regulation mechanisms of hydro-biogeochemical processes on the distributions of DO and hypoxia. A narrow hypoxic zone (with the minimum DO mass concentration of 2.18 mg/L) in a southwest-northeast orientation, which was characterized by a high apparent oxygen consumption (AOU) (＞4 mg/L), was observed within the bottom cold water-dominated region in the western BS; a low-DO area with a small scope existed in the northeastern region off the Bohai Bay mouth at 10-m layer. DO concentrations in the NYS were overall higher than that in the BS, and a relatively high DO level was maintained within the Bottom Cold Water Mass (BCWM) in the central NYS, although there was a high AOU (＞2.5 mg/L). The low-lying topography and higher stratification intensity within the bottom cold water-dominated region in the western BS provided the basis for the formation and maintenance of bottom hypoxia, and the fronts around this cold water significantly controlled the boundary and extension scope of the hypoxic zone. The low-DO area at 10-m layer in the northeastern region off the Bohai Bay mouth was caused by the uplift of the hypoxic cold water from the bottom. The presence of an anticyclonic eddy in the shallow bank of the central BS led to the formation of a DO-rich water (＞6 mg/L) at bottom. The decomposition of organic matter and related oxygen consumption in the context of stratification was an important material basis for the formation of hypoxia in the western BS, exactly corresponding to a high-nutrient area at bottom layer. In contrast, due to the higher background levels of DO within the BCWM and the lower AOU than that in the bottom layer of the western BS, it was difficult to form hypoxia in the central NYS even under the relatively high stratification strength; moreover, the deeper water depth was another factor responsible for this situation. This study could provide a scientific basis for understanding the multi-scale variations and regulation of DO in the BS and the NYS, laying a foundation for the subsequent refined simulation and prediction of hypoxia in this sea area.
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This article explores the distinctive marine environment of the West African coastal region, with a particular focus on bimodal waves-induced seabed response and stability around sloping breakwaters. Bimodal waves are a unique wave pattern observed in the West African Sea, influenced by distant swells from the North Atlantic. These waves present new challenges in marine engineering, particularly in the design and maintenance of breakwater structures. A complex numerical model has been developed to simulate the interaction between bimodal spectrum random waves and sloping breakwaters. This model is grounded in the Reynolds-averaged Navier-Stokes equations and employs the k-ω turbulence model to simulate the flow field and pressure distribution around the breakwater. Furthermore, the model incorporates Biot’s semi-dynamic porous medium theory (the u-p model) to assess wave-induced pore pressure and the liquefaction features of the seabed. The study found that the pore pressure response varies under different conditions, generally indicating that pore pressure increases with the swell energy ratio (SER). It was observed that low-frequency pore pressure becomes more pronounced with increasing depth and swell wave ratio. Analyzing the swell energy ratio revealed that the attenuation rate of low-frequency energy is lower than that of high-frequency energy. As the swell energy ratio increases, the pore pressure response in the seabed intensifies significantly, leading to an expansion in the range and depth of seabed liquefaction, especially noticeable at certain distances in front of the breakwater. Furthermore, the influence of high-frequency and low-frequency pore pressure on seabed liquefaction alternates with the increasing distance from the breakwater’s toe. This study provides a scientific basis for the design and stability assessment of sloping breakwaters.
This article explores the distinctive marine environment of the West African coastal region, with a particular focus on bimodal waves-induced seabed response and stability around sloping breakwaters. Bimodal waves are a unique wave pattern observed in the West African Sea, influenced by distant swells from the North Atlantic. These waves present new challenges in marine engineering, particularly in the design and maintenance of breakwater structures. A complex numerical model has been developed to simulate the interaction between bimodal spectrum random waves and sloping breakwaters. This model is grounded in the Reynolds-averaged Navier-Stokes equations and employs the k-ω turbulence model to simulate the flow field and pressure distribution around the breakwater. Furthermore, the model incorporates Biot’s semi-dynamic porous medium theory (the u-p model) to assess wave-induced pore pressure and the liquefaction features of the seabed. The study found that the pore pressure response varies under different conditions, generally indicating that pore pressure increases with the swell energy ratio (SER). It was observed that low-frequency pore pressure becomes more pronounced with increasing depth and swell wave ratio. Analyzing the swell energy ratio revealed that the attenuation rate of low-frequency energy is lower than that of high-frequency energy. As the swell energy ratio increases, the pore pressure response in the seabed intensifies significantly, leading to an expansion in the range and depth of seabed liquefaction, especially noticeable at certain distances in front of the breakwater. Furthermore, the influence of high-frequency and low-frequency pore pressure on seabed liquefaction alternates with the increasing distance from the breakwater’s toe. This study provides a scientific basis for the design and stability assessment of sloping breakwaters.
, Available online ,
doi: 10.12284/hyxb2024-00
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The 210Bi-210Pb radionuclide pair is considered to be a new radiotracer for particulate carbon dynamics. Due to the very short half-life of 210Bi and the difficulty of determination, we have very few knowledge about the biogeochemical behavior of 210Bi in the ocean and whether there is a 210Bi-210Pb activity disequilibrium. This paper reported the observation results of dissolved and particulate 210Po, 210Bi, and 210Pb and their activity ratios in seawaters in the East China Sea close to the Changjiang River Estuary during a red tide event on the spring scientific cruise from May 5 to 15, 2017. The results showed that the 210Po/210Pb activity ratio varied from 0.20 to 2.08, with an average of 0.82±0.58 (n=15) and the 210Bi/210Pb activity ratio changed between 0.31 and 3.72, showing an average of 1.38±0.79 (n=15). This phenomenon indicates that the activity disequilibrium of 210Po-210Pb and 210Bi-210Pb was ubiquitous in the seawater. More specifically, there is an obvious 210Po and 210Bi excess relative to 210Pb in deep seawater, which implied that 210Po and 210Bi might be released from sinking particles in the middle and deep layer of water column. By calculating the distribution coefficients and fractionation factors of 210Po, 210Bi, and 210Pb, it was found that suspended particles in seawater tended to preferentially scavenge and remove 210Po and 210Bi, comparing with 210Pb. Similar to 210Po, 210Bi showed a stronger particle affinity for marine suspended particles than 210Pb, and the increase of phytoplankton biomass can promote the fractionation behavior between 210Bi and 210Pb, supporting the idea that 210Bi-210Pb can be used to trace particle processes in the ocean.
The 210Bi-210Pb radionuclide pair is considered to be a new radiotracer for particulate carbon dynamics. Due to the very short half-life of 210Bi and the difficulty of determination, we have very few knowledge about the biogeochemical behavior of 210Bi in the ocean and whether there is a 210Bi-210Pb activity disequilibrium. This paper reported the observation results of dissolved and particulate 210Po, 210Bi, and 210Pb and their activity ratios in seawaters in the East China Sea close to the Changjiang River Estuary during a red tide event on the spring scientific cruise from May 5 to 15, 2017. The results showed that the 210Po/210Pb activity ratio varied from 0.20 to 2.08, with an average of 0.82±0.58 (n=15) and the 210Bi/210Pb activity ratio changed between 0.31 and 3.72, showing an average of 1.38±0.79 (n=15). This phenomenon indicates that the activity disequilibrium of 210Po-210Pb and 210Bi-210Pb was ubiquitous in the seawater. More specifically, there is an obvious 210Po and 210Bi excess relative to 210Pb in deep seawater, which implied that 210Po and 210Bi might be released from sinking particles in the middle and deep layer of water column. By calculating the distribution coefficients and fractionation factors of 210Po, 210Bi, and 210Pb, it was found that suspended particles in seawater tended to preferentially scavenge and remove 210Po and 210Bi, comparing with 210Pb. Similar to 210Po, 210Bi showed a stronger particle affinity for marine suspended particles than 210Pb, and the increase of phytoplankton biomass can promote the fractionation behavior between 210Bi and 210Pb, supporting the idea that 210Bi-210Pb can be used to trace particle processes in the ocean.
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Turbidity is a reliable indicator for assessing water quality conditions. Turbidity monitoring can effectively reflect the health status of water bodies and guarantee the sustainable development of ecosystems and the safe utilization of water resources. In this study, Sentinel-2 MSI images from 2016 to 2023 were employed in the construction of a quantitative inversion model based on measured data. The temporal and spatial distribution characteristics and variation rules of water turbidity in the Hong Kong coastal waters over the past eight years were analyzed, and the main influencing factors were explored. In comparison to the traditional empirical model, random forest (RF) model, gradient boosted decision tree (GBDT) model, and K Nearest Neighbor (KNN) model, the RF-based turbidity inversion model had the highest accuracy (R2 = 0.708, RMSE = 1.774 NTU, MAE = 1.439 NTU). The results demonstrate that the annual average turbidity of the water body fluctuates between 4.02 and 4.16 NTU, exhibiting a downward trend over the past eight years (-0.0243 NTU/a). Additionally, the spatial distribution is high in the north-west and low in the south-east. The seasonal average water turbidity, in descending order, was as follows: winter (4.54 NTU), autumn (4.03 NTU), spring (3.86 NTU) and summer (3.76 NTU). Utilizing meteorological data and investment data on sewage treatment in Hong Kong, we analyzed the factors affecting the spatial and temporal distribution of turbidity in terms of the natural environment and human activities. Turbidity in Hong Kong's offshore waters exhibits a negative correlation with inlet runoff and air temperature. Additionally, it is influenced by the anthropogenic factor of sewage treatment in Hong Kong. Furthermore, there is a significant correlation between precipitation and wind speed during the period of tropical cyclone activity and the change in turbidity in the water column.
Turbidity is a reliable indicator for assessing water quality conditions. Turbidity monitoring can effectively reflect the health status of water bodies and guarantee the sustainable development of ecosystems and the safe utilization of water resources. In this study, Sentinel-2 MSI images from 2016 to 2023 were employed in the construction of a quantitative inversion model based on measured data. The temporal and spatial distribution characteristics and variation rules of water turbidity in the Hong Kong coastal waters over the past eight years were analyzed, and the main influencing factors were explored. In comparison to the traditional empirical model, random forest (RF) model, gradient boosted decision tree (GBDT) model, and K Nearest Neighbor (KNN) model, the RF-based turbidity inversion model had the highest accuracy (R2 = 0.708, RMSE = 1.774 NTU, MAE = 1.439 NTU). The results demonstrate that the annual average turbidity of the water body fluctuates between 4.02 and 4.16 NTU, exhibiting a downward trend over the past eight years (-
, Available online ,
doi: 10.12284/hyxb2024001
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Underwater target detection is an important part of China's “transparent ocean” project. However, due to the complex and ever-changing underwater environment, achieving accurate and efficient detection of underwater targets remains a significant challenge. As a fixed offshore platform across the sea, the buoy is an important part of building a comprehensive and three-dimensional detection network, which can simultaneously meet the all-weather monitoring requirements of key locations in the ocean and achieve real-time information transmission, complementing more accurate and real-time underwater target information acquisition methods. Based on the summary of existing underwater target detection methods based on buoys, this article introduces optical detection, electromagnetic detection, communication relay, and other underwater target detection and information transmission technologies. It also combs and analyzes relevant technologies in combination with the application characteristics of buoys, with a view to providing useful inspiration and reference for the research and application of underwater target detection technology based on buoys.
Underwater target detection is an important part of China's “transparent ocean” project. However, due to the complex and ever-changing underwater environment, achieving accurate and efficient detection of underwater targets remains a significant challenge. As a fixed offshore platform across the sea, the buoy is an important part of building a comprehensive and three-dimensional detection network, which can simultaneously meet the all-weather monitoring requirements of key locations in the ocean and achieve real-time information transmission, complementing more accurate and real-time underwater target information acquisition methods. Based on the summary of existing underwater target detection methods based on buoys, this article introduces optical detection, electromagnetic detection, communication relay, and other underwater target detection and information transmission technologies. It also combs and analyzes relevant technologies in combination with the application characteristics of buoys, with a view to providing useful inspiration and reference for the research and application of underwater target detection technology based on buoys.
, Available online ,
doi: 10.12284/hyxb2024019
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Based on the hydrographic observations carried out in the austral summer during 2013 and 2015 from the continental shelf to the front regions of Vincennes Bay, East Antarctica, this study utilizes an optimum multiparameter analysis method to evaluate the export pathway of Vincennes Bay Bottom Water (VBBW) and its contribution rate to Antarctic bottom water (AABW). The results show that the freshest, coldest, and most oxygen-rich bottom water is distributed above the northwestern ridge of Vincennes Bay. The highest proportion of local Dense Shelf Water (DSW) on the bottom over this ridge was (28.58 ± 1.75)%, which exceeded the proportion observed at all other stations on the offshore side of the continental slope. The VBBW, a mixture of local DSW and modified Circumpolar Deep Water, was also maximized in the AABW layer on this northwestern ridge. The results suggest that topography plays an important role in guiding the outflow of local DSW and even VBBW, and the northwestern ridge could be the main pathway for VBBW export. In the vertical direction, the proportion of DSW decreases with the shallower depth at most stations, but patchy DSW contribution layers were commonly observed in the sub-bottom layers, which means that the proportion of DSW increases in some depth ranges. According to the anomaly distribution of seawater characteristics on the density surfaces, the DSW in the sub-bottom layers can also be exported along the isopycnals, manifested as thermohaline intrusion patches. These thermohaline intrusion patches have significantly colder, fresher, and oxygen-rich characteristics, which may contribute to the enhancement of sub-bottom ventilation. In addition, VBBW can reach the bottom of the Australia-Antarctic basin at depths deeper than4000 m but with a limited contribution rate, no more than 17%, and is mainly contributed by mCDW. This study helps understand the export pathway and contribution of bottom water from the medium bay to the bottom layer of the Australia-Antarctic Basin. It provides a reference for further study on the formation and modification of the AABW in this basin.
Based on the hydrographic observations carried out in the austral summer during 2013 and 2015 from the continental shelf to the front regions of Vincennes Bay, East Antarctica, this study utilizes an optimum multiparameter analysis method to evaluate the export pathway of Vincennes Bay Bottom Water (VBBW) and its contribution rate to Antarctic bottom water (AABW). The results show that the freshest, coldest, and most oxygen-rich bottom water is distributed above the northwestern ridge of Vincennes Bay. The highest proportion of local Dense Shelf Water (DSW) on the bottom over this ridge was (28.58 ± 1.75)%, which exceeded the proportion observed at all other stations on the offshore side of the continental slope. The VBBW, a mixture of local DSW and modified Circumpolar Deep Water, was also maximized in the AABW layer on this northwestern ridge. The results suggest that topography plays an important role in guiding the outflow of local DSW and even VBBW, and the northwestern ridge could be the main pathway for VBBW export. In the vertical direction, the proportion of DSW decreases with the shallower depth at most stations, but patchy DSW contribution layers were commonly observed in the sub-bottom layers, which means that the proportion of DSW increases in some depth ranges. According to the anomaly distribution of seawater characteristics on the density surfaces, the DSW in the sub-bottom layers can also be exported along the isopycnals, manifested as thermohaline intrusion patches. These thermohaline intrusion patches have significantly colder, fresher, and oxygen-rich characteristics, which may contribute to the enhancement of sub-bottom ventilation. In addition, VBBW can reach the bottom of the Australia-Antarctic basin at depths deeper than
, Available online ,
doi: 10.12284/hyxb2025038
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To investigate the survival, growth, and physiological responses of Zostera marina transplants to different water velocities and determine the optimal flow velocity range, an experiment was conducted. The study aimed to elucidate the effects of water velocity on Z. marina transplants by measuring and evaluating their survival rates, growth performance, and physiological indicators, as well as examining the interrelationships among these factors. Results indicated that the survival rate of transplanted Z. marina plants peaked at 0.4 m/s, being 1.1−2.4 times higher than those in the other treatments (P<0.05). Notably, all plants in the control group perished. Aboveground tissue growth decreased progressively with increasing water velocity, while belowground tissue growth increased gradually. Specifically, leaf elongation rate at 1 m/s was 24.0% lower compared to 0.2 m/s, whereas belowground dry weight at 0.4 m/s was 1.6 times higher than that at 0.2 m/s. Photosynthetic pigment and nonstructural carbohydrates contents in leaves reached their lowest levels between 0.4 and 0.6 m/s, decreasing by 0.8% to 18.5% relative to other treatments. Considering the survival and growth comprehensive income index and physiological index stability coefficient, the suitable flow velocity range for Z. marina transplants is 0.3 to 0.8 m/s, with an optimal range of 0.4 to 0.6 m/s. These findings suggest that moderately increasing water flow velocity can facilitate the rapid establishment and expansion of Z. marina transplants.
To investigate the survival, growth, and physiological responses of Zostera marina transplants to different water velocities and determine the optimal flow velocity range, an experiment was conducted. The study aimed to elucidate the effects of water velocity on Z. marina transplants by measuring and evaluating their survival rates, growth performance, and physiological indicators, as well as examining the interrelationships among these factors. Results indicated that the survival rate of transplanted Z. marina plants peaked at 0.4 m/s, being 1.1−2.4 times higher than those in the other treatments (P<0.05). Notably, all plants in the control group perished. Aboveground tissue growth decreased progressively with increasing water velocity, while belowground tissue growth increased gradually. Specifically, leaf elongation rate at 1 m/s was 24.0% lower compared to 0.2 m/s, whereas belowground dry weight at 0.4 m/s was 1.6 times higher than that at 0.2 m/s. Photosynthetic pigment and nonstructural carbohydrates contents in leaves reached their lowest levels between 0.4 and 0.6 m/s, decreasing by 0.8% to 18.5% relative to other treatments. Considering the survival and growth comprehensive income index and physiological index stability coefficient, the suitable flow velocity range for Z. marina transplants is 0.3 to 0.8 m/s, with an optimal range of 0.4 to 0.6 m/s. These findings suggest that moderately increasing water flow velocity can facilitate the rapid establishment and expansion of Z. marina transplants.
, Available online ,
doi: 10.12284/hyxb2025010
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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.
, 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/hyxb2025026
Abstract:
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/hyxb2025036
Abstract:
The freshwater discharges of the Changjiang (Yangtze) River into the sea largely control the extension range of the Changjiang Diluted Water in the estuary and the inherent biogeochemical behaviors of biogenic elements. In July 2023, a summer drought event occurred in the Changjiang River basin, with extremely lower river discharge. In order to study the distribution characteristics of nutrients in the Changjiang River Estuary in response to this drought, samples were collected from 32 stations in the Changjiang River Estuary that month, and the results were further compared with those obtained before and after the arrivals of the Changjiang River watershed floods occurring in the summers of 2016 and 2020. Under the drought condition in July 2023, the estuarine mixing area of freshwater and seawater greatly shrank, and the time and space for the occurrences of non-conservative processes of\begin{document}${{\rm {NO}}_3^-} $\end{document} ![]()
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The freshwater discharges of the Changjiang (Yangtze) River into the sea largely control the extension range of the Changjiang Diluted Water in the estuary and the inherent biogeochemical behaviors of biogenic elements. In July 2023, a summer drought event occurred in the Changjiang River basin, with extremely lower river discharge. In order to study the distribution characteristics of nutrients in the Changjiang River Estuary in response to this drought, samples were collected from 32 stations in the Changjiang River Estuary that month, and the results were further compared with those obtained before and after the arrivals of the Changjiang River watershed floods occurring in the summers of 2016 and 2020. Under the drought condition in July 2023, the estuarine mixing area of freshwater and seawater greatly shrank, and the time and space for the occurrences of non-conservative processes of
, Available online
Abstract:
A near-real-time version of the blended sea surface wind (BSSW) data product from multiple satellites, as well as the data processing method, and data accuracy analysis is introduced in this paper. The BSSW used sea surface winds provided by the virtual satellite constellation composed of HY-2 series satellites, Metop series satellites and DMSP series satellites as input. Error analysis, cross-calibration and 2D-Var processing is applied to blend these winds derived from different platform. With these methods, a near-real-time blended sea surface product with 6 hours interval and a spatial resolution of 25 kilometers is produced and released operationally by National Satellite Ocean Satellite Application Service. Comparing to buoy data, the RMSE is below 1.6 m/s for wind speed and below 19° for wind direction. While comparing to ERA5 data, the RMSE is below 1.2 m/s for wind speed and below 11° for wind direction. The validation results show that the BSSW is consistent with the buoy winds and ERA5 winds, indicating that BSSW can be of great importance to ocean and atmospheric numerical forecast model, marine disaster prevention and reduction, as well as scientific research on ocean.
A near-real-time version of the blended sea surface wind (BSSW) data product from multiple satellites, as well as the data processing method, and data accuracy analysis is introduced in this paper. The BSSW used sea surface winds provided by the virtual satellite constellation composed of HY-2 series satellites, Metop series satellites and DMSP series satellites as input. Error analysis, cross-calibration and 2D-Var processing is applied to blend these winds derived from different platform. With these methods, a near-real-time blended sea surface product with 6 hours interval and a spatial resolution of 25 kilometers is produced and released operationally by National Satellite Ocean Satellite Application Service. Comparing to buoy data, the RMSE is below 1.6 m/s for wind speed and below 19° for wind direction. While comparing to ERA5 data, the RMSE is below 1.2 m/s for wind speed and below 11° for wind direction. The validation results show that the BSSW is consistent with the buoy winds and ERA5 winds, indicating that BSSW can be of great importance to ocean and atmospheric numerical forecast model, marine disaster prevention and reduction, as well as scientific research on ocean.
, Available online
Abstract:
Beach erosion under the influence of frequent and severe storm events is generally increasing. Understanding the process of beach profile change under the influence of storm events is essential for the protection of sandy coast erosion. To clarify the response characteristics of the embayed beach profile to the storm, this study combined field observation during the typhoon and the XBeach model to reveal the profile morphological changes of the Dongsha beach in Zhujiajian Island, Zhejiang Province, under the influence of typhoon Tapah, and the influence of different factors on the beach storm response was discussed. The main results are as follows. Under the influence of typhoon Tapah, the profile of the Dongsha beach showed a significant pattern of erosion in the upper part of the profile and accretion in the lower part, and there was almost no change in the topography on the seaward side of the 400 m offshore (sand-mud transition). The calculation of different storm scenarios shows that the significant wave height controls the erosion and deposition amplitude of the profile, while the tidal level controls the position of erosion and deposition on the profile. When the storm wave height is large, the difference in profile changes caused by different settings of fine to medium sand grain size range is small. The offshore distance of the stop point of profile change is farther when there is beach nourishment. The results of this study can provide a scientific reference for the protection of storm erosion in the sandy coast.
Beach erosion under the influence of frequent and severe storm events is generally increasing. Understanding the process of beach profile change under the influence of storm events is essential for the protection of sandy coast erosion. To clarify the response characteristics of the embayed beach profile to the storm, this study combined field observation during the typhoon and the XBeach model to reveal the profile morphological changes of the Dongsha beach in Zhujiajian Island, Zhejiang Province, under the influence of typhoon Tapah, and the influence of different factors on the beach storm response was discussed. The main results are as follows. Under the influence of typhoon Tapah, the profile of the Dongsha beach showed a significant pattern of erosion in the upper part of the profile and accretion in the lower part, and there was almost no change in the topography on the seaward side of the 400 m offshore (sand-mud transition). The calculation of different storm scenarios shows that the significant wave height controls the erosion and deposition amplitude of the profile, while the tidal level controls the position of erosion and deposition on the profile. When the storm wave height is large, the difference in profile changes caused by different settings of fine to medium sand grain size range is small. The offshore distance of the stop point of profile change is farther when there is beach nourishment. The results of this study can provide a scientific reference for the protection of storm erosion in the sandy coast.
, 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
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/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.
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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.
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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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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.
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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.
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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.
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2024, 46(12): 1-12.
doi: 10.12284/hyxb2024107
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, the GLORYS12V1 reanalysis exhibits a northward deviation in the simulated horizontal extent of Atlantic Water, which results in an over estimation 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, the GLORYS12V1 reanalysis exhibits a northward deviation in the simulated horizontal extent of Atlantic Water, which results in an over estimation 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.
2024, 46(12): 13-25.
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 due to 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 due to 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
2024, 46(12): 26-39.
doi: 10.12284/hyxb2024129
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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 flux increasing as the flow flux 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 ebb 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 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 flux increasing as the flow flux 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 ebb 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 sediment movements driven by waves.
2024, 46(12): 40-52.
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 model 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 paleogeomorphology, medium sediment supply and strong 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 paleogeomorphology, 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 model 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 paleogeomorphology, medium sediment supply and strong 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 paleogeomorphology, 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.
2024, 46(12): 53-65.
doi: 10.12284/hyxb2024085
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 revealed the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibited 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 revealed the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibited 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.
2024, 46(12): 66-78.
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 E−W and NE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian. The third set of NW 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 of karstification, 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 E−W and NE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian. The third set of NW 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 of karstification, 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.
2024, 46(12): 79-86.
doi: 10.12284/hyxb2024111
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.
2024, 46(12): 87-99.
doi: 10.12284/hyxb2024117
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, and 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 cot α 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, and 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 cot α 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.
2024, 46(12): 100-110.
doi: 10.12284/hyxb2024115
Abstract:
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.
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.
2024, 46(12): 111-121.
doi: 10.12284/hyxb2024127
Abstract:
The prediction of El Niño-Southern Oscillation is one of the hot issues in climate change research. This paper combines swin-transformer model with spatio-temporal fusion attention mechanism, and uses CMIP6 multi-model simulation historical data from 1850 to 2014, SODA assimilated data from 1871 to 1979 and GODAS assimilated data from 1980 to 2023 to construct El Niño-Southern Oscillation prediction model—ENSO-STformer. The model was fully trained on CMIP6 and SODA datasets and evaluated on GODAS data. The results show that the average skill of this model in predicting the Niño3.4 index at 11-month lead times exceeds those of CanCM4, CCSM3, and GFDLaer04 by 5.1%, 21.6%, and 12.4% respectively. Meanwhile, the Niño3.4 index related skills of the proposed model are significantly better than other deep learning models in the medium and long term. Effective ENSO forecasts can be made for up to 24 months, and the 2015−2016 El Niño event simulation shows strong ability to cope with spring forecast obstacles.
The prediction of El Niño-Southern Oscillation is one of the hot issues in climate change research. This paper combines swin-transformer model with spatio-temporal fusion attention mechanism, and uses CMIP6 multi-model simulation historical data from 1850 to 2014, SODA assimilated data from 1871 to 1979 and GODAS assimilated data from 1980 to 2023 to construct El Niño-Southern Oscillation prediction model—ENSO-STformer. The model was fully trained on CMIP6 and SODA datasets and evaluated on GODAS data. The results show that the average skill of this model in predicting the Niño3.4 index at 11-month lead times exceeds those of CanCM4, CCSM3, and GFDLaer04 by 5.1%, 21.6%, and 12.4% respectively. Meanwhile, the Niño3.4 index related skills of the proposed model are significantly better than other deep learning models in the medium and long term. Effective ENSO forecasts can be made for up to 24 months, and the 2015−2016 El Niño event simulation shows strong ability to cope with spring forecast obstacles.
2024, 46(12): 122-134.
doi: 10.12284/hyxb2024119
Abstract:
Short-term precipitation nowcasting is a critical task in both meteorology and hydrology. However, current deep learning methods often yield ambiguous prediction results and exhibit significant cumulative errors. To address the limitations associated with these predictive methods, particularly the challenges of cumulative error and lack of clarity in prediction sequences, we propose a novel approach based on a Multi-scale Attention Encoding-Dynamic Decoding Network (MAEDDN) for short-term precipitation nowcasting. This method leverages the learning of spatiotemporal features from input data to accurately predict future precipitation scenarios. To obtain richer feature information from the input sequences, the encoding process employs convolutional blocks with spatial and channel attention for encoding. And a multi-scale fusion module is introduced to address the challenge of capturing both small-scale and large-scale information in precipitation distribution simultaneously. To enhance the clarity of the predicted sequences, the model needs to better understand the precipitation process. Therefore, in the decoding process, a dynamic decoding network is proposed in response to the generation and dissipation processes accompanying short-term precipitation. This network flexibly filters the decoding process by learning the intensity distribution and change trends of past input data. Experiments are conducted by using the precipitation data from the open-source SEVIR dataset, and comparisons are made with the best methods reported so far. The experimental results reveal that: (1) MAEDDN enhances the forecasting capability in areas with high-intensity precipitation, and (2) The clarity of the predicted image sequences by MAEDDN is significantly better than that of other models. The constructed multi-scale attention encoding captures the complex relationships in meteorological data more effectively, while the dynamic decoding adapts the decoding process based on different scenarios, resulting in more accurate prediction outcomes.
Short-term precipitation nowcasting is a critical task in both meteorology and hydrology. However, current deep learning methods often yield ambiguous prediction results and exhibit significant cumulative errors. To address the limitations associated with these predictive methods, particularly the challenges of cumulative error and lack of clarity in prediction sequences, we propose a novel approach based on a Multi-scale Attention Encoding-Dynamic Decoding Network (MAEDDN) for short-term precipitation nowcasting. This method leverages the learning of spatiotemporal features from input data to accurately predict future precipitation scenarios. To obtain richer feature information from the input sequences, the encoding process employs convolutional blocks with spatial and channel attention for encoding. And a multi-scale fusion module is introduced to address the challenge of capturing both small-scale and large-scale information in precipitation distribution simultaneously. To enhance the clarity of the predicted sequences, the model needs to better understand the precipitation process. Therefore, in the decoding process, a dynamic decoding network is proposed in response to the generation and dissipation processes accompanying short-term precipitation. This network flexibly filters the decoding process by learning the intensity distribution and change trends of past input data. Experiments are conducted by using the precipitation data from the open-source SEVIR dataset, and comparisons are made with the best methods reported so far. The experimental results reveal that: (1) MAEDDN enhances the forecasting capability in areas with high-intensity precipitation, and (2) The clarity of the predicted image sequences by MAEDDN is significantly better than that of other models. The constructed multi-scale attention encoding captures the complex relationships in meteorological data more effectively, while the dynamic decoding adapts the decoding process based on different scenarios, resulting in more accurate prediction outcomes.
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