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, Available online , doi: 10.12284/hyxb2025006
Abstract:
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, which significantly decreased to (127.0 ± 18.8) n/kg 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, which significantly decreased to (127.0 ± 18.8) n/kg 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
Abstract:
Abstracts: Mangroves represent the most productive ecosystem along the coastline. The mangrove forest is a source of diverse organic carbon, which contributes to the complexity of the trophic structure of the benthic food web. This study employed the benthic animals in the mangroves along Yanpu Bay as the research object, analysing the community trophic structure and determining the potential food sources through the utilisation of the stable isotope technique in conjunction with the Stable Isotope Bayesian Ellipses (SIBER) model and the Stable Isotope Mixing Models (Simmr). The study demonstrated that the carbon stable isotope (δ13C) values of benthic animals ranged from −22.04‰ to −11.27‰, while the nitrogen stable isotope (δ15N) values ranged The trophic levels ranged from 1.33 (Cerithidea rhizophorarum) to 3.95 (Periophthalmus cantonensis), with carbon stable isotope (δ13C) values from 5.86‰ to 16.21‰. The trophic level of fish is relatively high, ranging from 2.38 to 3.95, while that of crustaceans is 2.61 to 3.52. In contrast, the trophic level of mollusc is relatively low, ranging from 1.33 to 3.15. These differences are related to the feeding preferences of the different groups. The analysis of the nutritional structure indicates that the length of the food chain and the nutritional diversity of fish are greater than those of crustaceans and mollusc. The diversity of food sources and nutritional uniformity of crustaceans are the highest, while the nutritional diversity and similarity of mollusc are the highest. Overall, there is a varying degree of overlap between the core nutritional niches of fish, crustaceans and mollusc. An analysis of the potential food sources of benthic animals based on a Simmr mixed model revealed that SOM was the primary carbon source, accounting for 78.2% of the total, followed by phytoplankton, which constituted 21.6% of the total, while litter and POM represented the lowest proportions, at 3.7% and 3.3%, respectively. The findings of this study enhance our comprehension of the trophic relationships of benthic animals in mangrove ecosystems along the northern coast of China. They will facilitate more effective conservation and restoration of mangrove biodiversity from a trophic regulation perspective.
Abstracts: Mangroves represent the most productive ecosystem along the coastline. The mangrove forest is a source of diverse organic carbon, which contributes to the complexity of the trophic structure of the benthic food web. This study employed the benthic animals in the mangroves along Yanpu Bay as the research object, analysing the community trophic structure and determining the potential food sources through the utilisation of the stable isotope technique in conjunction with the Stable Isotope Bayesian Ellipses (SIBER) model and the Stable Isotope Mixing Models (Simmr). The study demonstrated that the carbon stable isotope (δ13C) values of benthic animals ranged from −22.04‰ to −11.27‰, while the nitrogen stable isotope (δ15N) values ranged The trophic levels ranged from 1.33 (Cerithidea rhizophorarum) to 3.95 (Periophthalmus cantonensis), with carbon stable isotope (δ13C) values from 5.86‰ to 16.21‰. The trophic level of fish is relatively high, ranging from 2.38 to 3.95, while that of crustaceans is 2.61 to 3.52. In contrast, the trophic level of mollusc is relatively low, ranging from 1.33 to 3.15. These differences are related to the feeding preferences of the different groups. The analysis of the nutritional structure indicates that the length of the food chain and the nutritional diversity of fish are greater than those of crustaceans and mollusc. The diversity of food sources and nutritional uniformity of crustaceans are the highest, while the nutritional diversity and similarity of mollusc are the highest. Overall, there is a varying degree of overlap between the core nutritional niches of fish, crustaceans and mollusc. An analysis of the potential food sources of benthic animals based on a Simmr mixed model revealed that SOM was the primary carbon source, accounting for 78.2% of the total, followed by phytoplankton, which constituted 21.6% of the total, while litter and POM represented the lowest proportions, at 3.7% and 3.3%, respectively. The findings of this study enhance our comprehension of the trophic relationships of benthic animals in mangrove ecosystems along the northern coast of China. They will facilitate more effective conservation and restoration of mangrove biodiversity from a trophic regulation perspective.
, Available online
Abstract:
Research based on observation and machine learning shows that the average annual carbon sink intensity of the China marginal seas (Bohai Sea, Yellow Sea, East China Sea and South China Sea) is −10.2±4.4 TgC/a. The Yellow Sea, the East China Sea and the northern region of the South China Sea absorb atmospheric CO2, while the Bohai Sea, the southern South China Sea and the Yangtze River Estuary release CO2 into the atmosphere. The East China Sea carbon sinks are the strongest, with an average flux of −10.5±4.5 TgC/a, and the Yellow Sea carbon sinks are relatively small, −2.1±0.9 TgC/a. The smallest carbon source appeared in the Bohai Sea is +0.3±0.1 TgC/a, while the largest carbon source intensity appeared in the South China Sea is +2.0±0.9 TgC/a. According to seasonal change, the carbon sink intensity in winter is the highest in the China margin seas, with −45.7±19.7 TgC/a, and weaker in spring, at −16.9±7.3 TgC/a. In summer and autumn, China's marginal seas as a whole are carbon sources, with an average of +11.9±5.1 TgC/a and +9.9±4.3 TgC/a respectively. The average uncertainty of carbon source sink strength in China marginal seas is ±43.0% (±4.4 TgC a−1) in the estimation results of constructing lattiness data based on observation data and machine learning, which is 47.5% of the reduced uncertainty less than 90.5% of the average uncertainty by only regional observation data. The difference of PCO2 at the sea-air interface and the difference in the CO2 exchange rate caused by wind speed are the key controlling factors of carbon source/sink in the China marginal seas. In fact, they are controlled by the basic factors and processes such as hydrodynamics, land-based source input, plankton communities and ocean-shelf transportation.
Research based on observation and machine learning shows that the average annual carbon sink intensity of the China marginal seas (Bohai Sea, Yellow Sea, East China Sea and South China Sea) is −10.2±4.4 TgC/a. The Yellow Sea, the East China Sea and the northern region of the South China Sea absorb atmospheric CO2, while the Bohai Sea, the southern South China Sea and the Yangtze River Estuary release CO2 into the atmosphere. The East China Sea carbon sinks are the strongest, with an average flux of −10.5±4.5 TgC/a, and the Yellow Sea carbon sinks are relatively small, −2.1±0.9 TgC/a. The smallest carbon source appeared in the Bohai Sea is +0.3±0.1 TgC/a, while the largest carbon source intensity appeared in the South China Sea is +2.0±0.9 TgC/a. According to seasonal change, the carbon sink intensity in winter is the highest in the China margin seas, with −45.7±19.7 TgC/a, and weaker in spring, at −16.9±7.3 TgC/a. In summer and autumn, China's marginal seas as a whole are carbon sources, with an average of +11.9±5.1 TgC/a and +9.9±4.3 TgC/a respectively. The average uncertainty of carbon source sink strength in China marginal seas is ±43.0% (±4.4 TgC a−1) in the estimation results of constructing lattiness data based on observation data and machine learning, which is 47.5% of the reduced uncertainty less than 90.5% of the average uncertainty by only regional observation data. The difference of PCO2 at the sea-air interface and the difference in the CO2 exchange rate caused by wind speed are the key controlling factors of carbon source/sink in the China marginal seas. In fact, they are controlled by the basic factors and processes such as hydrodynamics, land-based source input, plankton communities and ocean-shelf transportation.
, Available online
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Marine reservoirs ages are of great value for the calibration of marine radiocarbon dates and the reconstruction of ocean circulation. Tephras from explosive volcanic eruptions can link marine and terrestrial radiocarbon-dated samples, aiding in the reconstruction of past marine reservoir ages. However, factors such as bioturbation and ice-rafted debris increase the complexity of the tephra chronostratigraphy, especially in study areas located far from the source volcano. This study analyzes the abundance and geochemical composition of tephras in a high-deposition-rate core from the mid-latitude North Atlantic, demonstrating its correlation with North Atlantic Ash Zone I from higher latitudes. By combining radiocarbon dating results with evidence from other sediment cores in the North Atlantic, we systematically evaluated the reliability of the Vedde Ash isochron in the mid- to high-latitude North Atlantic and inferred a transport mechanism for the Vedde Ash via sea ice to the Northwest Atlantic. Our high-resolution tephra abundance stratigraphy confirms the effect of bioturbation on the distribution of thin tephra layers in sediment cores, further emphasizing the importance of bioturbation correction in marine sediment records. After bioturbation correction, the marine reservoir age estimated for the core region during the Younger Dryas is 758±58 14C yr, which is in good agreement with the marine reservoir age distribution in the subpolar North Atlantic during the same period. Our study shows that, after evaluating the reliability of the tephra chronostratigraphy, Vedde and other tephras from the high-latitude North Atlantic can be applied over a wider spatial range.
Marine reservoirs ages are of great value for the calibration of marine radiocarbon dates and the reconstruction of ocean circulation. Tephras from explosive volcanic eruptions can link marine and terrestrial radiocarbon-dated samples, aiding in the reconstruction of past marine reservoir ages. However, factors such as bioturbation and ice-rafted debris increase the complexity of the tephra chronostratigraphy, especially in study areas located far from the source volcano. This study analyzes the abundance and geochemical composition of tephras in a high-deposition-rate core from the mid-latitude North Atlantic, demonstrating its correlation with North Atlantic Ash Zone I from higher latitudes. By combining radiocarbon dating results with evidence from other sediment cores in the North Atlantic, we systematically evaluated the reliability of the Vedde Ash isochron in the mid- to high-latitude North Atlantic and inferred a transport mechanism for the Vedde Ash via sea ice to the Northwest Atlantic. Our high-resolution tephra abundance stratigraphy confirms the effect of bioturbation on the distribution of thin tephra layers in sediment cores, further emphasizing the importance of bioturbation correction in marine sediment records. After bioturbation correction, the marine reservoir age estimated for the core region during the Younger Dryas is 758±58 14C yr, which is in good agreement with the marine reservoir age distribution in the subpolar North Atlantic during the same period. Our study shows that, after evaluating the reliability of the tephra chronostratigraphy, Vedde and other tephras from the high-latitude North Atlantic can be applied over a wider spatial range.
, Available online
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Mytilus coruscus is an economically significant shellfish cultivated in China, with its life and behavior greatly influenced by light conditions. However, much remains unknown about its opsin genes. In this study, seven opsins were identified based on whole-genome sequencing data of M. coruscus, and sequence analysis classified them into five types: r-opsin, c-opsin, Go-opsin, neuropsin, and peropsin. Chromosomal localization analysis revealed that opsin genes of the same subfamily are located on the same chromosome. Bioinformatics analysis showed that, except for r-opsin, all identified proteins are hydrophobic. The conserved motifs revealed high sequence conservation among opsin subfamily members, while inter-subfamily comparisons identified specific divergent residues. The expression profiles of opsin genes were examined across five developmental stages using real-time quantitative PCR, which demonstrated significant expression differences at various developmental stages. Notably, c-opsin4 and r-opsin were significantly upregulated during the eyespot stage, suggesting their crucial roles during this period.This study provides insights into the molecular characteristics of opsins in M. coruscus and preliminarily explores the expression patterns of opsin genes during its development. Additionally, it contributes to the understanding of visual formation mechanisms in M. coruscus and offers a scientific basis for further exploration of the regulatory role of opsins in the metamorphosis process.
Mytilus coruscus is an economically significant shellfish cultivated in China, with its life and behavior greatly influenced by light conditions. However, much remains unknown about its opsin genes. In this study, seven opsins were identified based on whole-genome sequencing data of M. coruscus, and sequence analysis classified them into five types: r-opsin, c-opsin, Go-opsin, neuropsin, and peropsin. Chromosomal localization analysis revealed that opsin genes of the same subfamily are located on the same chromosome. Bioinformatics analysis showed that, except for r-opsin, all identified proteins are hydrophobic. The conserved motifs revealed high sequence conservation among opsin subfamily members, while inter-subfamily comparisons identified specific divergent residues. The expression profiles of opsin genes were examined across five developmental stages using real-time quantitative PCR, which demonstrated significant expression differences at various developmental stages. Notably, c-opsin4 and r-opsin were significantly upregulated during the eyespot stage, suggesting their crucial roles during this period.This study provides insights into the molecular characteristics of opsins in M. coruscus and preliminarily explores the expression patterns of opsin genes during its development. Additionally, it contributes to the understanding of visual formation mechanisms in M. coruscus and offers a scientific basis for further exploration of the regulatory role of opsins in the metamorphosis process.
, Available online
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Global warming has led to frequent large-scale coral bleaching events, accelerating the degradation of coral reef ecosystems. Internationally, coral transplantation is commonly employed as a method to restore degraded coral reefs, with Acropora species constituting the majority of the transplanted corals. However, fast-growing branching Acropora corals are more sensitive to heat, which affects their restoration efficacy in the increasingly warming marine environment. To understand the thermal response patterns and thermal tolerance differences of Acropora, this study conducted high-temperature stress experiments on Acropora muricata and Acropora hyacinthus from Weizhou Island, Guangxi. Through the analysis of physiological and biochemical indicators, it was observed that after high-temperature stress, A. muricata exhibited tentacle retraction and color fading, and the activity levels of antioxidants (superoxide dismutase, glutathione, catalase), ammonium assimilation enzyme (glutamine synthetase), and cysteinyl aspartate specific proteinase-3 (caspase-3) showed a trend of initially increasing and then decreasing. A. hyacinthus showed a similar response pattern, except for superoxide dismutase and glutamine synthetase. At 34℃, A. hyacinthus performed better in physiological indicators, with superoxide dismutase, ammonium assimilation enzyme, and caspase-3 maintained high activity and sensitive response, indicating that A. hyacinthus resists high-temperature environments by increasing the activity of these proteases, and it is more heat-tolerant than A. muricata. This study revealed the physiological response patterns of the two Acropora species under high-temperature stress and compared their thermal tolerance differences, providing a theoretical basis for the selection of heat-tolerant corals and the ecological restoration of coral reefs.
Global warming has led to frequent large-scale coral bleaching events, accelerating the degradation of coral reef ecosystems. Internationally, coral transplantation is commonly employed as a method to restore degraded coral reefs, with Acropora species constituting the majority of the transplanted corals. However, fast-growing branching Acropora corals are more sensitive to heat, which affects their restoration efficacy in the increasingly warming marine environment. To understand the thermal response patterns and thermal tolerance differences of Acropora, this study conducted high-temperature stress experiments on Acropora muricata and Acropora hyacinthus from Weizhou Island, Guangxi. Through the analysis of physiological and biochemical indicators, it was observed that after high-temperature stress, A. muricata exhibited tentacle retraction and color fading, and the activity levels of antioxidants (superoxide dismutase, glutathione, catalase), ammonium assimilation enzyme (glutamine synthetase), and cysteinyl aspartate specific proteinase-3 (caspase-3) showed a trend of initially increasing and then decreasing. A. hyacinthus showed a similar response pattern, except for superoxide dismutase and glutamine synthetase. At 34℃, A. hyacinthus performed better in physiological indicators, with superoxide dismutase, ammonium assimilation enzyme, and caspase-3 maintained high activity and sensitive response, indicating that A. hyacinthus resists high-temperature environments by increasing the activity of these proteases, and it is more heat-tolerant than A. muricata. This study revealed the physiological response patterns of the two Acropora species under high-temperature stress and compared their thermal tolerance differences, providing a theoretical basis for the selection of heat-tolerant corals and the ecological restoration of coral reefs.
, Available online
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In the process of marine integrated geophysical surveys, in the absence of an acoustic synchronizer, acoustic pulses emitted by multibeam and other acoustic equipment become noise for sub-bottom profiling, severely affecting the signal-to-noise ratio and resolution of sub-bottom data as a form of interference. These types of noise have frequencies similar to those of effective signals, exhibit strong amplitudes, and can appear anywhere on seismic records. Although existing median filtering techniques can suppress such interference waves, they may also degrade the effective signals to a certain extent. This paper proposes an improved switching median filtering method. The method first identifies the location of the interference waves in the sub-bottom profile using the Median Absolute Deviation (MAD) criterion, and then applies median filtering to denoise signals in the vicinity of interference, while leaving noise-free signals unaltered. Applying this method to sub-bottom profiles obtained from the South Yellow Sea shelf showed that the proposed improved switching median filter could effectively attenuate acoustic interference similar to multibeam pulses while minimizing the loss of effective signals compared to previous methods.
In the process of marine integrated geophysical surveys, in the absence of an acoustic synchronizer, acoustic pulses emitted by multibeam and other acoustic equipment become noise for sub-bottom profiling, severely affecting the signal-to-noise ratio and resolution of sub-bottom data as a form of interference. These types of noise have frequencies similar to those of effective signals, exhibit strong amplitudes, and can appear anywhere on seismic records. Although existing median filtering techniques can suppress such interference waves, they may also degrade the effective signals to a certain extent. This paper proposes an improved switching median filtering method. The method first identifies the location of the interference waves in the sub-bottom profile using the Median Absolute Deviation (MAD) criterion, and then applies median filtering to denoise signals in the vicinity of interference, while leaving noise-free signals unaltered. Applying this method to sub-bottom profiles obtained from the South Yellow Sea shelf showed that the proposed improved switching median filter could effectively attenuate acoustic interference similar to multibeam pulses while minimizing the loss of effective signals compared to previous methods.
, Available online
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To investigate the mobility and transformation of mercury (Hg) in the wetlands of Changjiang Estuary, microcosm incubation experiments were conducted under different redox conditions over a long period (252 days). Four sediments collected from different wetlands were added with dissolved Hg(NO3)2 to simulate recent Hg inputs to wetlands, resulting in sediment total Hg increased by 109.7−275.1%. (1) The results showed that the concentrations of methylmercury (MeHg) in sediments increased by 1.9−361.5% (on average 183.0%) over the course of incubation. Amendment of litterfall after 140 days incubation, anaerobic degradation of litter can significantly enhance MeHg production with a larger increase (on average 260.2%) compared to those in the control. These results suggest that soluble Hg is easily methylated to MeHg, especially with labile organic matter inputs, and the aging processes of Hg could be significantly influenced by labile organic matter. Furthermore, MeHg/THg (%), as an estimate of long-term MeHg production were significantly different among sediments for all sampling time points, which was most probably due to the differences of the Hg methylating bacteria in sediments. (2) During oxidation stage of the sediments, a significant negative correlation between the MeHg concentrations and the redox potential (Eh) was observed. The results indicate that MeHg demethylation occurred under oxic resuspension conditions, which was enhanced in the presence of labile organic matter. This was most probably due to the combination of biotic demethylation with aerobic microorganisms and abiotic demethylation associated with reactive oxygen species from oxygenation of Fe(II)-bearing particles. The role of the abiotic pathways and mechanisms in the degradation of methylmercury in estuaries, coasts and other natural aquatic systems needs to be further investigated. (3) Most of the Hg accumulated in the ＜8 μm fractions, probably due to the formation of Hg-organic matter complexes that was aggregated with metal (oxyhydr)oxides and clay minerals. Thus, very fine particles may be the main carriers of Hg in Changjiang Estuary.
To investigate the mobility and transformation of mercury (Hg) in the wetlands of Changjiang Estuary, microcosm incubation experiments were conducted under different redox conditions over a long period (252 days). Four sediments collected from different wetlands were added with dissolved Hg(NO3)2 to simulate recent Hg inputs to wetlands, resulting in sediment total Hg increased by 109.7−275.1%. (1) The results showed that the concentrations of methylmercury (MeHg) in sediments increased by 1.9−361.5% (on average 183.0%) over the course of incubation. Amendment of litterfall after 140 days incubation, anaerobic degradation of litter can significantly enhance MeHg production with a larger increase (on average 260.2%) compared to those in the control. These results suggest that soluble Hg is easily methylated to MeHg, especially with labile organic matter inputs, and the aging processes of Hg could be significantly influenced by labile organic matter. Furthermore, MeHg/THg (%), as an estimate of long-term MeHg production were significantly different among sediments for all sampling time points, which was most probably due to the differences of the Hg methylating bacteria in sediments. (2) During oxidation stage of the sediments, a significant negative correlation between the MeHg concentrations and the redox potential (Eh) was observed. The results indicate that MeHg demethylation occurred under oxic resuspension conditions, which was enhanced in the presence of labile organic matter. This was most probably due to the combination of biotic demethylation with aerobic microorganisms and abiotic demethylation associated with reactive oxygen species from oxygenation of Fe(II)-bearing particles. The role of the abiotic pathways and mechanisms in the degradation of methylmercury in estuaries, coasts and other natural aquatic systems needs to be further investigated. (3) Most of the Hg accumulated in the ＜8 μm fractions, probably due to the formation of Hg-organic matter complexes that was aggregated with metal (oxyhydr)oxides and clay minerals. Thus, very fine particles may be the main carriers of Hg in Changjiang Estuary.
, Available online
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We conducted two surveys on the carbonate system in Xiaohai, the largest lagoon on Hainan Island, during April and October 2023. The aims were to evaluate the seasonal differences in riverine inorganic carbon export flux, air-sea carbon dioxide (CO2) flux, and coastal acidification as well as their controlling mechanisms. The results indicate that the surrounding major rivers deliver 0.682×109 mol dissolved inorganic carbon (DIC), 0.571×109 mol total alkalinity, and 0.195×109 mol calcium ions to Xiaohai Lagoon annually, and multiple factors result in a high DIC areal yield among other estuaries around the world (47/134). The lagoon water was a CO2 source in April, but turned into a sink in October, with an annual mean CO2 flux (0.9 mol·m−2·yr−1) significantly lower than most tropical lagoons worldwide. In April, some acidification events occurred in the southeastern lagoon and the northern tidal channel. In October, strong photosynthesis by benthic seagrass, macroalgae, and phytoplankton alleviated estuarine acidification, resulting in a supersaturation of dissolved oxygen (107%−136%), a deficit of partial pressure of CO2 as low as 116 μatm, and an elevated pH (8.41±0.14) significantly higher than the offshore seawater. Our study will provide scientific support for the carbon cycle in tropical lagoons and ecological environment management in Xiaohai Lagoon.
We conducted two surveys on the carbonate system in Xiaohai, the largest lagoon on Hainan Island, during April and October 2023. The aims were to evaluate the seasonal differences in riverine inorganic carbon export flux, air-sea carbon dioxide (CO2) flux, and coastal acidification as well as their controlling mechanisms. The results indicate that the surrounding major rivers deliver 0.682×109 mol dissolved inorganic carbon (DIC), 0.571×109 mol total alkalinity, and 0.195×109 mol calcium ions to Xiaohai Lagoon annually, and multiple factors result in a high DIC areal yield among other estuaries around the world (47/134). The lagoon water was a CO2 source in April, but turned into a sink in October, with an annual mean CO2 flux (0.9 mol·m−2·yr−1) significantly lower than most tropical lagoons worldwide. In April, some acidification events occurred in the southeastern lagoon and the northern tidal channel. In October, strong photosynthesis by benthic seagrass, macroalgae, and phytoplankton alleviated estuarine acidification, resulting in a supersaturation of dissolved oxygen (107%−136%), a deficit of partial pressure of CO2 as low as 116 μatm, and an elevated pH (8.41±0.14) significantly higher than the offshore seawater. Our study will provide scientific support for the carbon cycle in tropical lagoons and ecological environment management in Xiaohai Lagoon.
, Available online
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To understand the spatio-temporal variation characteristics of zooplankton communities in the Nanji Islands sea area, three voyage surveys of aquatic organisms and hydrological factors were conducted in November 2022, May 2023, and September 2023, respectively. Laboratory experimental results showed that a total of 93 species of zooplankton were identified, including 20 species of plankton larvae. The 2023.09 voyage recorded the highest species richness (63 species), while the 2022.11 voyage had the lowest (45 species). Among these, 19 dominant species (Y ≥ 0.02) included Sagitta bedoti, Flaccisagitta enflata, Calanus sinicus, Acartia pacifica, and others. The average abundance of zooplankton was 512.84 ind./m³, and the average biomass was 614.82 mg/m³, with significant differences among the voyages. The 2023.09 voyage had the highest abundance and biomass, while the 2022.11 voyage had the lowest. The average values of the Shannon-Wiener diversity index (H'), species evenness index (J'), and richness index (D) for zooplankton were 1.64, 0.55, and 2.57, respectively. Results from Spearman correlation analysis 、Non-metric Multidimensional Scaling Analysis and Canonical Correspondence Analysis indicated that salinity, temperature, total nitrogen content, nitrate concentration, and phytoplankton abundance were important environmental factors influencing the biomass of dominant zooplankton species in the Nanji Islands sea area.
To understand the spatio-temporal variation characteristics of zooplankton communities in the Nanji Islands sea area, three voyage surveys of aquatic organisms and hydrological factors were conducted in November 2022, May 2023, and September 2023, respectively. Laboratory experimental results showed that a total of 93 species of zooplankton were identified, including 20 species of plankton larvae. The 2023.09 voyage recorded the highest species richness (63 species), while the 2022.11 voyage had the lowest (45 species). Among these, 19 dominant species (Y ≥ 0.02) included Sagitta bedoti, Flaccisagitta enflata, Calanus sinicus, Acartia pacifica, and others. The average abundance of zooplankton was 512.84 ind./m³, and the average biomass was 614.82 mg/m³, with significant differences among the voyages. The 2023.09 voyage had the highest abundance and biomass, while the 2022.11 voyage had the lowest. The average values of the Shannon-Wiener diversity index (H'), species evenness index (J'), and richness index (D) for zooplankton were 1.64, 0.55, and 2.57, respectively. Results from Spearman correlation analysis 、Non-metric Multidimensional Scaling Analysis and Canonical Correspondence Analysis indicated that salinity, temperature, total nitrogen content, nitrate concentration, and phytoplankton abundance were important environmental factors influencing the biomass of dominant zooplankton species in the Nanji Islands sea area.
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Marine magnetic data are susceptible to interference from factors such as navigation errors, instrument malfunctions, and transcript mistakes, leading to frequent outliers. These outliers not only distort the magnetic anomaly patterns but also disrupt the continuity of magnetic stripes, severely affecting data quality and the reliability of subsequent interpretations. Therefore, outlier detection and removal are crucial steps in marine magnetic data processing. However, traditional methods often fail to effectively distinguish between different types of outliers, especially contextual outliers. Additionally, manual detection is time-consuming, prone to errors, and inefficient. To address this issue, this study proposes a weighted Hampel filter based on a local median weighting strategy. This method dynamically adjusts the weights of data points to more accurately identify and remove outliers in marine magnetic data, especially performing well in regions with significant data heterogeneity. Compared to other methods such as autoregression, isolation forest, and autoencoder, weighted Hampel filter not only effectively detects and removes global and contextual outliers but also better preserves the original features of the data, significantly improving detection accuracy. In validation with real data from the Magellan Rise in the Central Pacific Ocean, weighted Hampel filter consistently achieved higher F1 scores than other methods, demonstrating its superiority in outlier detection. This method provides important technical support for improving the quality and interpretability of marine magnetic data and lays a foundation for the future automated processing of large-scale data.
Marine magnetic data are susceptible to interference from factors such as navigation errors, instrument malfunctions, and transcript mistakes, leading to frequent outliers. These outliers not only distort the magnetic anomaly patterns but also disrupt the continuity of magnetic stripes, severely affecting data quality and the reliability of subsequent interpretations. Therefore, outlier detection and removal are crucial steps in marine magnetic data processing. However, traditional methods often fail to effectively distinguish between different types of outliers, especially contextual outliers. Additionally, manual detection is time-consuming, prone to errors, and inefficient. To address this issue, this study proposes a weighted Hampel filter based on a local median weighting strategy. This method dynamically adjusts the weights of data points to more accurately identify and remove outliers in marine magnetic data, especially performing well in regions with significant data heterogeneity. Compared to other methods such as autoregression, isolation forest, and autoencoder, weighted Hampel filter not only effectively detects and removes global and contextual outliers but also better preserves the original features of the data, significantly improving detection accuracy. In validation with real data from the Magellan Rise in the Central Pacific Ocean, weighted Hampel filter consistently achieved higher F1 scores than other methods, demonstrating its superiority in outlier detection. This method provides important technical support for improving the quality and interpretability of marine magnetic data and lays a foundation for the future automated processing of large-scale data.
Spatial distribution of Arctic tidal dynamics and analysis of tidal wave propagation characteristics
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The Arctic has become a global strategic focal point due to its rich mineral resources, navigational routes, and unique geopolitical landscape. Understanding the tidal dynamics in Arctic waters is key to assessing its environmental patterns and resource development potential. This study analyzes the primary tidal characteristics and tidal wave propagation in the Arctic Ocean using oceanographic statistical methods, based on the Arc5km2018 Arctic tidal model and the ArcTiCA tidal dataset. The results show that semi-diurnal tides dominate the region, with the M2 tidal constituent being the most significant, reaching amplitudes of up to 1.2 m, while the central areas exhibit much smaller amplitudes (less than 0.1 m). In coastal and archipelago regions, shallow-water tides significantly influence tidal asymmetry, with the absolute value of the tidal asymmetry coefficient exceeding 0.2. Due to complex topography and coastlines, multiple counterclockwise amphidromic points and tidal convergence zones, formed by the confluence of various tidal waves, are present in the Arctic. Tidal waves primarily propagate from the Norwegian Sea into the Barents Sea, and from the Greenland Sea toward the East Siberian Sea, Chukchi Sea, and the Parry Archipelago, with propagation speeds generally not exceeding 200 m/s, and being positively correlated with the square root of water depth. The amplitude gradient is generally below 5 × 10−3 km−1. This study provides critical data to support the integrated management and resource development of the Arctic region.
The Arctic has become a global strategic focal point due to its rich mineral resources, navigational routes, and unique geopolitical landscape. Understanding the tidal dynamics in Arctic waters is key to assessing its environmental patterns and resource development potential. This study analyzes the primary tidal characteristics and tidal wave propagation in the Arctic Ocean using oceanographic statistical methods, based on the Arc5km2018 Arctic tidal model and the ArcTiCA tidal dataset. The results show that semi-diurnal tides dominate the region, with the M2 tidal constituent being the most significant, reaching amplitudes of up to 1.2 m, while the central areas exhibit much smaller amplitudes (less than 0.1 m). In coastal and archipelago regions, shallow-water tides significantly influence tidal asymmetry, with the absolute value of the tidal asymmetry coefficient exceeding 0.2. Due to complex topography and coastlines, multiple counterclockwise amphidromic points and tidal convergence zones, formed by the confluence of various tidal waves, are present in the Arctic. Tidal waves primarily propagate from the Norwegian Sea into the Barents Sea, and from the Greenland Sea toward the East Siberian Sea, Chukchi Sea, and the Parry Archipelago, with propagation speeds generally not exceeding 200 m/s, and being positively correlated with the square root of water depth. The amplitude gradient is generally below 5 × 10−3 km−1. This study provides critical data to support the integrated management and resource development of the Arctic region.
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There are complex interactions between the sediment components of silty-muddy tidal flats and benthic microalgae, which affect the stability of the tidal flat ecosystem and geomorphological evolution. In order to explore the influence law of benthic microalgae on sediment components, this study took the typical silty-muddy tidal flat in Tiaozini, Jiangsu Province as the research object. Through field observations and laboratory analyses, the temporal and spatial variations and the interrelationships between benthic microalgae and sediment components were revealed. The research results show that there are temporal and spatial differences in the biomass of benthic microalgae and the particle size distribution of sediments. The biomass of benthic microalgae in autumn and winter is higher than that in spring and summer, and it is distributed in the surface layer of 0−1 cm. The median particle size in spring and summer is larger than that in autumn and winter. The difference in hydrodynamic forces on both sides of tidal channels leads to the synchronous mutation phenomenon of the biomass of benthic microalgae and sediment components. The biomass of microalgae in the convex bank area is relatively high and the sediment particle size is smaller, while in the concave bank area, the erosion is intense and the biomass decreases. Environmental conditions (such as temperature and light) and the composition of microalgae communities jointly drive the temporal and spatial changes in the relationship between benthic microalgae and sediment components. In summer, the diverse microalgae communities enhance the biostabilization effect on various sediment components, while in winter, the dominant position of diatoms strengthens the selectivity for clay and fine silt.
There are complex interactions between the sediment components of silty-muddy tidal flats and benthic microalgae, which affect the stability of the tidal flat ecosystem and geomorphological evolution. In order to explore the influence law of benthic microalgae on sediment components, this study took the typical silty-muddy tidal flat in Tiaozini, Jiangsu Province as the research object. Through field observations and laboratory analyses, the temporal and spatial variations and the interrelationships between benthic microalgae and sediment components were revealed. The research results show that there are temporal and spatial differences in the biomass of benthic microalgae and the particle size distribution of sediments. The biomass of benthic microalgae in autumn and winter is higher than that in spring and summer, and it is distributed in the surface layer of 0−1 cm. The median particle size in spring and summer is larger than that in autumn and winter. The difference in hydrodynamic forces on both sides of tidal channels leads to the synchronous mutation phenomenon of the biomass of benthic microalgae and sediment components. The biomass of microalgae in the convex bank area is relatively high and the sediment particle size is smaller, while in the concave bank area, the erosion is intense and the biomass decreases. Environmental conditions (such as temperature and light) and the composition of microalgae communities jointly drive the temporal and spatial changes in the relationship between benthic microalgae and sediment components. In summer, the diverse microalgae communities enhance the biostabilization effect on various sediment components, while in winter, the dominant position of diatoms strengthens the selectivity for clay and fine silt.
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Investigating the relationship between fishery resources and environmental factors, along with understanding species distribution response mechanisms to environmental changes, provides fundamental insights for fisheries conservation and sustainable management. While both resource abundance and species distribution are influenced by multiple environmental factors, existing research has primarily emphasized direct environmental effects, with insufficient attention to inter-factor interactions. This study examines the mechanisms through which diverse environmental factors affect shrimp resources along Madagascar's western coast, utilizing shrimp trawl fishery data (2014−2020) and Bayesian network analysis to investigate relationships between precipitation, runoff, marine environmental factors, and catch per unit effort (CPUE) of three key shrimp species. Our analysis identified critical drivers of CPUE variation under combined environmental influences. Results demonstrated that precipitation, runoff, sea surface height anomaly (SSHA), and sea surface temperature (SST) predominantly influenced Fenneropenaeus indicus CPUE. For Metapenaeus monoceros and Penaeus semisulcatus, runoff, SSHA, SST, and chlorophyll-a concentration (Chl-a) constituted primary controlling factors. Precipitation exerted indirect effects on all species' CPUE through environmental mediators: impacting F. indicus via runoff-SST-SSHA pathways, while influencing M. monoceros and P. semisulcatus through runoff-SST-SSHA-Chl-a interactions. These findings clarify both direct effects of precipitation and marine environmental factors on shrimp CPUE, and reveal cascading indirect impacts where precipitation modulates population dynamics through environmental intermediaries, elucidating pathway mechanisms underlying these ecological relationships.
Investigating the relationship between fishery resources and environmental factors, along with understanding species distribution response mechanisms to environmental changes, provides fundamental insights for fisheries conservation and sustainable management. While both resource abundance and species distribution are influenced by multiple environmental factors, existing research has primarily emphasized direct environmental effects, with insufficient attention to inter-factor interactions. This study examines the mechanisms through which diverse environmental factors affect shrimp resources along Madagascar's western coast, utilizing shrimp trawl fishery data (2014−2020) and Bayesian network analysis to investigate relationships between precipitation, runoff, marine environmental factors, and catch per unit effort (CPUE) of three key shrimp species. Our analysis identified critical drivers of CPUE variation under combined environmental influences. Results demonstrated that precipitation, runoff, sea surface height anomaly (SSHA), and sea surface temperature (SST) predominantly influenced Fenneropenaeus indicus CPUE. For Metapenaeus monoceros and Penaeus semisulcatus, runoff, SSHA, SST, and chlorophyll-a concentration (Chl-a) constituted primary controlling factors. Precipitation exerted indirect effects on all species' CPUE through environmental mediators: impacting F. indicus via runoff-SST-SSHA pathways, while influencing M. monoceros and P. semisulcatus through runoff-SST-SSHA-Chl-a interactions. These findings clarify both direct effects of precipitation and marine environmental factors on shrimp CPUE, and reveal cascading indirect impacts where precipitation modulates population dynamics through environmental intermediaries, elucidating pathway mechanisms underlying these ecological relationships.
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Scopimera globosa is a typical sediment-feeding filter-feeding crab, a common species in the intertidal zone. In recent years, its population has declined significantly, leading to its inclusion on the regional Red List. Currently, domestic and foreign scholars have focused on the biology and basic ecology of this species, and have obtained some basic cognition. The paper summarizes the biological characteristics and adaptive behaviors of this species, including feeding behavior, burrowing and domain behavior, reproduction behavior, population recruitment, and wandering behavior. The population dynamics of S. globosa are less affected by biological factors and are mainly affected by environmental factors, such as salinity, organic matter content, and sediment grain size. In contrast, biological factors have a relatively limited influence. Currently, research on the behavior of this species in different habitats is still scarce, especially in the species-environment relationship. Therefore, it is urgent to conduct systematic research on the relationship between the crab and its habitat, to deeply explore its ecological adaptation mechanisms, to provide scientific basis for the ecological protection of this species, and provide theoretical support for the conservation and habitat management of sympatric filter-feeding crabs.
Scopimera globosa is a typical sediment-feeding filter-feeding crab, a common species in the intertidal zone. In recent years, its population has declined significantly, leading to its inclusion on the regional Red List. Currently, domestic and foreign scholars have focused on the biology and basic ecology of this species, and have obtained some basic cognition. The paper summarizes the biological characteristics and adaptive behaviors of this species, including feeding behavior, burrowing and domain behavior, reproduction behavior, population recruitment, and wandering behavior. The population dynamics of S. globosa are less affected by biological factors and are mainly affected by environmental factors, such as salinity, organic matter content, and sediment grain size. In contrast, biological factors have a relatively limited influence. Currently, research on the behavior of this species in different habitats is still scarce, especially in the species-environment relationship. Therefore, it is urgent to conduct systematic research on the relationship between the crab and its habitat, to deeply explore its ecological adaptation mechanisms, to provide scientific basis for the ecological protection of this species, and provide theoretical support for the conservation and habitat management of sympatric filter-feeding crabs.
, Available online , doi: 10.12284/hyxb2025029
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Submarine landslide, as a prevalent natural disaster, brings substantial hazards to ocean engineering. Moreover, the secondary disasters triggered by submarine landslides will exert a significant influence on the social and economic development in coastal areas. Consequently, researching the motion process of submarine landslides is of great significance. In this paper, a multiphase flow numerical model of submarine landslides is established with Comsol. The Herschel-Bulkley-Papanastasiou (HBP) viscous fluid model is utilized to simulate the landslide, while the surrounding water is modeled by the classical Newtonian fluid model. The numerical model results are compared with the experimental data from the literature to verify the accuracy of the numerical model. It is shown that the Comsol simulation results are consistent with the data in the literature, which indicates that this model has a certain degree of accuracy and can be used for the study and prediction of submarine landslides. Furthermore, in order to further conduct research and analysis on submarine landslides, this paper simulates the Zhujiajian submarine landslide and predicts the front-side velocity and sliding distance of the landslide mass. This study can serve as a reference for the prediction and prevention of submarine landslides.
Submarine landslide, as a prevalent natural disaster, brings substantial hazards to ocean engineering. Moreover, the secondary disasters triggered by submarine landslides will exert a significant influence on the social and economic development in coastal areas. Consequently, researching the motion process of submarine landslides is of great significance. In this paper, a multiphase flow numerical model of submarine landslides is established with Comsol. The Herschel-Bulkley-Papanastasiou (HBP) viscous fluid model is utilized to simulate the landslide, while the surrounding water is modeled by the classical Newtonian fluid model. The numerical model results are compared with the experimental data from the literature to verify the accuracy of the numerical model. It is shown that the Comsol simulation results are consistent with the data in the literature, which indicates that this model has a certain degree of accuracy and can be used for the study and prediction of submarine landslides. Furthermore, in order to further conduct research and analysis on submarine landslides, this paper simulates the Zhujiajian submarine landslide and predicts the front-side velocity and sliding distance of the landslide mass. This study can serve as a reference for the prediction and prevention of submarine landslides.
, Available online , doi: 10.12284/hyxb2025017
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The surf zone eddies play a vital role in material transport, coastal morphology, and ecological environment. However, the formation mechanisms and evolution characteristics of surf zone eddies, especially their spatiotemporal evolution under strong wave-induced currents, remain insufficiently understood. This study integrates pollutant tracer experiments and numerical simulations using the Funwave model based on the Boussinesq equations to investigate the evolution of surf zone eddies under strong wave-driven currents. The experimental results demonstrate that large eddy patches form both onshore and offshore within the surf zone under strong wave-induced currents, exhibiting transient behavior. Onshore eddies are constrained by the shoreline, whereas offshore eddies gradually expand and migrate seaward. The numerical simulations indicate that strong eddies concentrate near the breaking line, with the surf zone eddy field characterized by upstream and downstream shear zones, both exhibiting similar alongshore spacing and eddy structures. Vorticity positively correlates with wave height and period, and the stronger eddies are shifted to the seaward side. Under irregular wave conditions, vorticity decreases, accompanied by a shoreward shift in the locations of maximum vorticity.
The surf zone eddies play a vital role in material transport, coastal morphology, and ecological environment. However, the formation mechanisms and evolution characteristics of surf zone eddies, especially their spatiotemporal evolution under strong wave-induced currents, remain insufficiently understood. This study integrates pollutant tracer experiments and numerical simulations using the Funwave model based on the Boussinesq equations to investigate the evolution of surf zone eddies under strong wave-driven currents. The experimental results demonstrate that large eddy patches form both onshore and offshore within the surf zone under strong wave-induced currents, exhibiting transient behavior. Onshore eddies are constrained by the shoreline, whereas offshore eddies gradually expand and migrate seaward. The numerical simulations indicate that strong eddies concentrate near the breaking line, with the surf zone eddy field characterized by upstream and downstream shear zones, both exhibiting similar alongshore spacing and eddy structures. Vorticity positively correlates with wave height and period, and the stronger eddies are shifted to the seaward side. Under irregular wave conditions, vorticity decreases, accompanied by a shoreward shift in the locations of maximum vorticity.
, Available online , doi: 10.12284/hyxb2025042
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This study aimed to investigate the allelopathic effects of Sesuvium portulacastrum (Aizoaceae) on typical red tide algae and identify the sources of the active compounds. Three red tide algae species, Prorocentrum micans, Karenia mikimotoi, and Alexandrium catenella, were selected as test subjects. The planting water of the coastal salt-tolerant plant Sesuvium portulacastrum served as the research material. Root exudates from the plant were adsorbed using a C18 solid-phase extraction column and then extracted with methanol, ethyl acetate, dichloromethane, and n-hexane. The four extracts exhibited varying degrees of inhibition on the growth of the algae, with the dichloromethane extract showing the most significant inhibitory effect. At a concentration of 10 g·L−1, the inhibition rates for the three algae species were 50.83%, 97.30%, and 81.41%, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis identified 19 fatty acids and their derivatives. Among these, stearic acid, oleamide, and docosanol exhibited algicidal activity, with docosanol showing the strongest effect. At a concentration of 2 mg·L−1, the inhibition rates for the three algae species were 90%, 100%, and 81.04%, respectively. These results indicate that Sesuvium portulacastrum can release fatty acids and their derivatives to inhibit the growth of red tide algae, demonstrating its potential as a plant-based tool for red tide control and environmental remediation.
This study aimed to investigate the allelopathic effects of Sesuvium portulacastrum (Aizoaceae) on typical red tide algae and identify the sources of the active compounds. Three red tide algae species, Prorocentrum micans, Karenia mikimotoi, and Alexandrium catenella, were selected as test subjects. The planting water of the coastal salt-tolerant plant Sesuvium portulacastrum served as the research material. Root exudates from the plant were adsorbed using a C18 solid-phase extraction column and then extracted with methanol, ethyl acetate, dichloromethane, and n-hexane. The four extracts exhibited varying degrees of inhibition on the growth of the algae, with the dichloromethane extract showing the most significant inhibitory effect. At a concentration of 10 g·L−1, the inhibition rates for the three algae species were 50.83%, 97.30%, and 81.41%, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis identified 19 fatty acids and their derivatives. Among these, stearic acid, oleamide, and docosanol exhibited algicidal activity, with docosanol showing the strongest effect. At a concentration of 2 mg·L−1, the inhibition rates for the three algae species were 90%, 100%, and 81.04%, respectively. These results indicate that Sesuvium portulacastrum can release fatty acids and their derivatives to inhibit the growth of red tide algae, demonstrating its potential as a plant-based tool for red tide control and environmental remediation.
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Typhoons, as one of the common natural disasters in coastal zones, have severe impacts on tidal flats. However, there is a significant lack of field data on typhoons, and studies on how salt marsh vegetation protects tidal flats during typhoon events are still very limited.. This study selected Chongming Dongtan in the Yangtze River Estuary as the research site. During the passage of Typhoon "In-Fa" in July 2021, hydrodynamic instruments and UAV photogrammetry (elevation measurements) were used to monitor hydrodynamics and sediment in both salt marsh and the marsh front areas, as well as to monitor the salt marsh ecosystem before and after the typhoon. The findings are as follows: (1) During the typhoon, wind speed, water depth, and wave height were 1.1 to 2.8 times those before and after the typhoon, and the hydrodynamic forces in the marsh front area were higher than those in the salt marsh area, with water depth, wave height, and flow velocity being 1.3 times, 1.2 times, and 1.9 times those of the salt marsh area, respectively; (2) Under the influence of Typhoon "In-Fa," vegetation patches at the marsh front, directly exposed to strong winds and waves, experienced hydrodynamic forces such as water depth and wave height that were 1.1 to 1.9 times those of the salt marsh area, resulting in erosion at the marsh front being 1.2 to 1.8 times that of the inland vegetation patches under the same vegetation coverage conditions; (3) In the marsh-front area, densely vegetated patches demonstrated stronger sediment accretion capacity compared to sparsely vegetated patches, with the maximum accretion thickness in densely vegetated areas reaching 45 cm, whereas sparse patches were mainly subject to erosion, with a maximum erosion depth of 17 cm. This indicates that the density of vegetation patches directly affects the sedimentation and erosion dynamics of the tidal flat. This study reveals that the arrangement and location of vegetation patches are crucial to the sedimentation and erosion of tidal flats under extreme weather events, which has significant implications for tidal flat management and ecological protection. It also provides theoretical support for establishing a robust natural barrier in response to extreme weather conditions.
Typhoons, as one of the common natural disasters in coastal zones, have severe impacts on tidal flats. However, there is a significant lack of field data on typhoons, and studies on how salt marsh vegetation protects tidal flats during typhoon events are still very limited.. This study selected Chongming Dongtan in the Yangtze River Estuary as the research site. During the passage of Typhoon "In-Fa" in July 2021, hydrodynamic instruments and UAV photogrammetry (elevation measurements) were used to monitor hydrodynamics and sediment in both salt marsh and the marsh front areas, as well as to monitor the salt marsh ecosystem before and after the typhoon. The findings are as follows: (1) During the typhoon, wind speed, water depth, and wave height were 1.1 to 2.8 times those before and after the typhoon, and the hydrodynamic forces in the marsh front area were higher than those in the salt marsh area, with water depth, wave height, and flow velocity being 1.3 times, 1.2 times, and 1.9 times those of the salt marsh area, respectively; (2) Under the influence of Typhoon "In-Fa," vegetation patches at the marsh front, directly exposed to strong winds and waves, experienced hydrodynamic forces such as water depth and wave height that were 1.1 to 1.9 times those of the salt marsh area, resulting in erosion at the marsh front being 1.2 to 1.8 times that of the inland vegetation patches under the same vegetation coverage conditions; (3) In the marsh-front area, densely vegetated patches demonstrated stronger sediment accretion capacity compared to sparsely vegetated patches, with the maximum accretion thickness in densely vegetated areas reaching 45 cm, whereas sparse patches were mainly subject to erosion, with a maximum erosion depth of 17 cm. This indicates that the density of vegetation patches directly affects the sedimentation and erosion dynamics of the tidal flat. This study reveals that the arrangement and location of vegetation patches are crucial to the sedimentation and erosion of tidal flats under extreme weather events, which has significant implications for tidal flat management and ecological protection. It also provides theoretical support for establishing a robust natural barrier in response to extreme weather conditions.
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Global coral bleaching under heat stress has been identified as a major driver of coral reef degradation. The composition, metabolism and functional characteristics of microbial communities in coral holosomes under heat stress has been reported. However, the changes in microbial structure and composition throughout the entire process of coral health - bleaching - recovery have not been studied so far. In this study, Porites lutea in Shenzhen Sea area was selected as the research object. The process of coral health - bleaching - recovery under heat stress was simulated in the laboratory. High-throughput sequencing and macro-genome sequencing technologies were used to analyse the differences in coral microbial communities and functional gene changes during five characteristic phases of coral bleaching and restoration: healthy, beginning of bleaching, continued bleaching, beginning of recover, and recovered. With the increase of temperature, Proteobacteria increased significantly during the bleaching process and decreased during recovery; Bacteroidota etc. decreased during bleaching and increased during recovery. During the coral bleaching process, the abundance of bacteria associated with stress tolerance, biofilm formation, mobile elements, and potential pathogenicity significantly increases. Conversely, the abundance of bacteria involved in quorum sensing decreases. Notably,four kinds of microbes play a crucial role in coral bleaching: Acinetobacter, Rhodobacter, and Burkholderia are key differential taxa in warming-induced coral bleaching, while Delftia may modulate other bacterial assemblages via quorum sensing mechanisms to maintain the stability of coral microbial communities.This study revealed the changes of microbes and their functions in coral tissues under high temperature stress, which provided molecular basis for elucidating the interaction mechanism between microbes and hosts during coral bleaching.
Global coral bleaching under heat stress has been identified as a major driver of coral reef degradation. The composition, metabolism and functional characteristics of microbial communities in coral holosomes under heat stress has been reported. However, the changes in microbial structure and composition throughout the entire process of coral health - bleaching - recovery have not been studied so far. In this study, Porites lutea in Shenzhen Sea area was selected as the research object. The process of coral health - bleaching - recovery under heat stress was simulated in the laboratory. High-throughput sequencing and macro-genome sequencing technologies were used to analyse the differences in coral microbial communities and functional gene changes during five characteristic phases of coral bleaching and restoration: healthy, beginning of bleaching, continued bleaching, beginning of recover, and recovered. With the increase of temperature, Proteobacteria increased significantly during the bleaching process and decreased during recovery; Bacteroidota etc. decreased during bleaching and increased during recovery. During the coral bleaching process, the abundance of bacteria associated with stress tolerance, biofilm formation, mobile elements, and potential pathogenicity significantly increases. Conversely, the abundance of bacteria involved in quorum sensing decreases. Notably,four kinds of microbes play a crucial role in coral bleaching: Acinetobacter, Rhodobacter, and Burkholderia are key differential taxa in warming-induced coral bleaching, while Delftia may modulate other bacterial assemblages via quorum sensing mechanisms to maintain the stability of coral microbial communities.This study revealed the changes of microbes and their functions in coral tissues under high temperature stress, which provided molecular basis for elucidating the interaction mechanism between microbes and hosts during coral bleaching.
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In this study, we conducted comprehensive field surveys in the Bohai Sea’s seagrass beds at Caofeidian, Yellow River mouth, and Juehua Island, gathering data on seagrass growth, water and sediment quality, plankton, benthic life, and juvenile fish. An integrated assessment index system for the nursery function of nearshore seagrass beds was constructed. The seagrass biomass at Caofeidian and Juehua Island was measured at 371.22 g m−2 and 340.05 g m−2, respectively, both of which were significantly higher than that recorded at the Yellow River mouth (161.24 g m−2, p < 0.05). The average abundance and biomass of phytoplankton in each seagrass bed followed the order: Yellow River mouth > Caofeidian > Juehua Island, exhibiting significant spatial differences (p < 0.05). Regarding juvenile fish density, Juehua Island exhibited the highest density, followed by the Yellow River mouth, with Caofeidian showing the lowest density, also demonstrating significant spatial differences (p < 0.05). The nursery function of seagrass beds was best in Juehua Island seagrass bed, followed by Caofeidian seagrass bed and Yellow River mouth seagrass bed. Environmental and biological indicators with significant contributions varied spatially. The seagrass bed in Juehua Island has a good environmental and biological status, with high water transparency, abundant dissolved oxygen, and moderate inorganic nitrogen concentration, and the juvenile fish community indicators all performed well, contributing significantly to the nursery function. The seagrass bed in Yellow River Delta has relatively poor water environment and biological status, with low water transparency, high pH value, and excessive inorganic nitrogen. The biological indicators showed poor plankton diversity characteristics and low proportion of juvenile fish, which became the main negative factors for its nursery function assessment result of only average. The environmental status in Caofeidian seagrass bed is good, with factors such as temperature, inorganic nitrogen, and inorganic phosphorus concentration contributing significantly. However, its biological status is average, and the low number of planktonic animals and juvenile fish is the main negative factor in the nursery function assessment of this area. This study helps to deeply understand and recognize the spatial and temporal differences and driving factors of the nursery function of typical seagrass beds in the Bohai Sea area, and provides effective scientific basis and data support for the protection of seagrass bed ecosystems and the sustainable development of marine fishery resources in China.
In this study, we conducted comprehensive field surveys in the Bohai Sea’s seagrass beds at Caofeidian, Yellow River mouth, and Juehua Island, gathering data on seagrass growth, water and sediment quality, plankton, benthic life, and juvenile fish. An integrated assessment index system for the nursery function of nearshore seagrass beds was constructed. The seagrass biomass at Caofeidian and Juehua Island was measured at 371.22 g m−2 and 340.05 g m−2, respectively, both of which were significantly higher than that recorded at the Yellow River mouth (161.24 g m−2, p < 0.05). The average abundance and biomass of phytoplankton in each seagrass bed followed the order: Yellow River mouth > Caofeidian > Juehua Island, exhibiting significant spatial differences (p < 0.05). Regarding juvenile fish density, Juehua Island exhibited the highest density, followed by the Yellow River mouth, with Caofeidian showing the lowest density, also demonstrating significant spatial differences (p < 0.05). The nursery function of seagrass beds was best in Juehua Island seagrass bed, followed by Caofeidian seagrass bed and Yellow River mouth seagrass bed. Environmental and biological indicators with significant contributions varied spatially. The seagrass bed in Juehua Island has a good environmental and biological status, with high water transparency, abundant dissolved oxygen, and moderate inorganic nitrogen concentration, and the juvenile fish community indicators all performed well, contributing significantly to the nursery function. The seagrass bed in Yellow River Delta has relatively poor water environment and biological status, with low water transparency, high pH value, and excessive inorganic nitrogen. The biological indicators showed poor plankton diversity characteristics and low proportion of juvenile fish, which became the main negative factors for its nursery function assessment result of only average. The environmental status in Caofeidian seagrass bed is good, with factors such as temperature, inorganic nitrogen, and inorganic phosphorus concentration contributing significantly. However, its biological status is average, and the low number of planktonic animals and juvenile fish is the main negative factor in the nursery function assessment of this area. This study helps to deeply understand and recognize the spatial and temporal differences and driving factors of the nursery function of typical seagrass beds in the Bohai Sea area, and provides effective scientific basis and data support for the protection of seagrass bed ecosystems and the sustainable development of marine fishery resources in China.
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Abstract:
Based on the Jason series satellite data from 2002 to 2020, the wind speed information of 431 hurricanes was obtained by using a high wind speed calculation method. On this basis, the best track data sets of hurricanes in the Atlantic and Northeast Pacific of the United States hurricane center based on reanalysis are compared and analyzed, and the high wind speed calculation method is comprehensively evaluated. The calculation and evaluation results show that the wind speed RMSE of 8.03-66.93 m/s hurricane is better than 4 m/s; the correlation coefficient between satellite wind speed and NHC hurricane best path data is above 0.9. This shows that the method in this paper is reliable and has the ability to observe the high wind speed of tropical cyclone. At the same time, the analysis results in the paper show that the hurricane observation period is almost accompanied by different degrees of rainfall. When the wind speed is greater than 50 m/s, the satellite observation points are in the moderate to heavy rain environment. The research in this paper proves the feasibility of using satellite radar altimeter and calibration radiometer to jointly obtain wind speed information in extreme marine environment, which provides a potential technical means for improving the wind speed observation ability of typhoon or hurricane. In addition, the statistical results show that there is also a good correlation between wind speed and pressure during the hurricane. This relationship can be used to quickly calculate the central pressure of tropical cyclone based on the high wind speed information obtained by satellite, which will form the satellite's ability to synchronously acquire the wind speed and central pressure of tropical cyclone.
Based on the Jason series satellite data from 2002 to 2020, the wind speed information of 431 hurricanes was obtained by using a high wind speed calculation method. On this basis, the best track data sets of hurricanes in the Atlantic and Northeast Pacific of the United States hurricane center based on reanalysis are compared and analyzed, and the high wind speed calculation method is comprehensively evaluated. The calculation and evaluation results show that the wind speed RMSE of 8.03-66.93 m/s hurricane is better than 4 m/s; the correlation coefficient between satellite wind speed and NHC hurricane best path data is above 0.9. This shows that the method in this paper is reliable and has the ability to observe the high wind speed of tropical cyclone. At the same time, the analysis results in the paper show that the hurricane observation period is almost accompanied by different degrees of rainfall. When the wind speed is greater than 50 m/s, the satellite observation points are in the moderate to heavy rain environment. The research in this paper proves the feasibility of using satellite radar altimeter and calibration radiometer to jointly obtain wind speed information in extreme marine environment, which provides a potential technical means for improving the wind speed observation ability of typhoon or hurricane. In addition, the statistical results show that there is also a good correlation between wind speed and pressure during the hurricane. This relationship can be used to quickly calculate the central pressure of tropical cyclone based on the high wind speed information obtained by satellite, which will form the satellite's ability to synchronously acquire the wind speed and central pressure of tropical cyclone.
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COD is an critical parameter for measuring the degree of organic pollution in water bodies. Using remote sensing inversion to quickly obtain the spatiotemporal distribution of COD concentration is essential for aquaculture pollution control and nearshore ecological environment protection. This study used Sentinel-2 extracted single band, vegetation index (NDVI), and water index (NDWI) to evaluate the performance of six models, including catboost regression (CBR), gradient boost regression (GBR), k-nearest neighbor regression (KNNR), light generalized boosted regression (LGBM), random forest (RF), and extreme gradient boosting regression (XGBR). The performance of each model was evaluated with the coefficient of determination (R2) and root mean square error (RMSE). The spatiotemporal distribution characteristics of COD concentration Maowei Sea and its coastal aquaculture ponds were analyzed. The results showed that: (1) The XGBR model had the best predictive performance, with a test set R2 of0.9432 and an RMSE of 1.4033 mg/L. (2) B8a, B2, and NDVI contributed significantly to the XGBR inversion model. (3) During the period of 2019-2023, the annual average concentration of COD in the aquaculture pond water ranged from 16.23 to 17.39 mg/L, with a relatively uniform spatial distribution pattern; The annual average concentration of COD in Maowei Sea ranged from 2.30 to 2.88 mg/L, showing a distribution pattern of decreasing from the inner bay to the outer bay and higher near the shore than far shore. This study has validated the remarkable universal applicability of the XGBR model when applied simultaneously to COD inversion in two specific aquatic environments: aquaculture waters and their coastal seas. The relevant findings not only provide valuable insights for COD inversion under various complex water quality conditions but also offer robust technical support and a solid theoretical foundation for aquaculture activities and environmental management in coastal areas.
COD is an critical parameter for measuring the degree of organic pollution in water bodies. Using remote sensing inversion to quickly obtain the spatiotemporal distribution of COD concentration is essential for aquaculture pollution control and nearshore ecological environment protection. This study used Sentinel-2 extracted single band, vegetation index (NDVI), and water index (NDWI) to evaluate the performance of six models, including catboost regression (CBR), gradient boost regression (GBR), k-nearest neighbor regression (KNNR), light generalized boosted regression (LGBM), random forest (RF), and extreme gradient boosting regression (XGBR). The performance of each model was evaluated with the coefficient of determination (R2) and root mean square error (RMSE). The spatiotemporal distribution characteristics of COD concentration Maowei Sea and its coastal aquaculture ponds were analyzed. The results showed that: (1) The XGBR model had the best predictive performance, with a test set R2 of
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Abstract:
Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) has excellent potential for obtaining water depth information around islands and reefs. However, due to the influence of laser, atmospheric scattering and other factors, ICESat-2 data contains a lot of noise. Combining multiscale analysis with the quadtree algorithm, we propose a new photon-counting LiDAR denoising method to discard the large amount of noise in ICESat-2 data. First, Kernel Density Estimation (KDE) is performed using a Gaussian kernel function and the K-fold cross validation to set threshold values that separate sea surface photons from seafloor photons. Second, abnormal photons are removed using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) with adaptive parameters, yielding rough denoising results. Finally, for the seafloor photon partition window, accurate seafloor signal photons are extracted across multiple scales using the pre-judgment quadtree. The study used ICESat-2 photon-counting data from typical islands and reefs, comparing it with in situ water depth measurements. The coefficient of determination (R²) in the study area reaches 95% and 98%, with root mean square errors (RMSE) of 1.01 m and 0.77 m, respectively. The results show that the proposed method can accurately extract underwater topographic information, providing a solid foundation for the inversion of shallow marine topography.
Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) has excellent potential for obtaining water depth information around islands and reefs. However, due to the influence of laser, atmospheric scattering and other factors, ICESat-2 data contains a lot of noise. Combining multiscale analysis with the quadtree algorithm, we propose a new photon-counting LiDAR denoising method to discard the large amount of noise in ICESat-2 data. First, Kernel Density Estimation (KDE) is performed using a Gaussian kernel function and the K-fold cross validation to set threshold values that separate sea surface photons from seafloor photons. Second, abnormal photons are removed using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) with adaptive parameters, yielding rough denoising results. Finally, for the seafloor photon partition window, accurate seafloor signal photons are extracted across multiple scales using the pre-judgment quadtree. The study used ICESat-2 photon-counting data from typical islands and reefs, comparing it with in situ water depth measurements. The coefficient of determination (R²) in the study area reaches 95% and 98%, with root mean square errors (RMSE) of 1.01 m and 0.77 m, respectively. The results show that the proposed method can accurately extract underwater topographic information, providing a solid foundation for the inversion of shallow marine topography.
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Mangrove wetlands are efficient coastal blue carbon sinks and play an important role in regulating the global carbon cycle. In this study, using grain size distribution, total organic carbon / total nitrogen (TOC/TN) ratio, δ13C values, and 210Pb chronological parameter, we investigated the sources of organic carbon (OC) and the temporal trends in sediment deposition and OC burial fluxes in the mangrove wetland of Tieshangang Bay, Guangxi. The results indicated that the sediment grain size was dominated by silt and sand, with TOC content and δ13C ranging from 0.26% to 3.96% and from −27.4 to −21.4‰, respectively. There was a strong correlation between TOC, TN, and δ13C values. The sedimentary organic matter in Tieshangang Bay had mainly a mixed signature with an average terrigenous contribution of 35.0%, marine sources 30.5% and mangrove contributions 34.5%, respectively. The average sediment OC flux over the past 100 years is 87.6 g C·m−2·a−1, and the carbon storage in sediments over the upper 50 cm can account for 65.3% of the total storage over the 95 cm depth. After 1961, there was a general decrease in sediment flux due to the construction of reservoir dams. Between 1961 and 1999, more terrestrial sources of OC were imported and buried due to climate and human disturbances around the watershed. Between 1999 and 2020, mangrove wetlands were destroyed and degraded due to extreme weather and natural factors. Degradation of mangrove wetlands under extreme weather and natural factors reduced the TOC content and OC burial fluxes. Since 2010, TOC content in the sediments has increased, probably due to higher water content, accumulation of litter and root growth. The OC source is dominated by the contribution from mangrove sources.
Mangrove wetlands are efficient coastal blue carbon sinks and play an important role in regulating the global carbon cycle. In this study, using grain size distribution, total organic carbon / total nitrogen (TOC/TN) ratio, δ13C values, and 210Pb chronological parameter, we investigated the sources of organic carbon (OC) and the temporal trends in sediment deposition and OC burial fluxes in the mangrove wetland of Tieshangang Bay, Guangxi. The results indicated that the sediment grain size was dominated by silt and sand, with TOC content and δ13C ranging from 0.26% to 3.96% and from −27.4 to −21.4‰, respectively. There was a strong correlation between TOC, TN, and δ13C values. The sedimentary organic matter in Tieshangang Bay had mainly a mixed signature with an average terrigenous contribution of 35.0%, marine sources 30.5% and mangrove contributions 34.5%, respectively. The average sediment OC flux over the past 100 years is 87.6 g C·m−2·a−1, and the carbon storage in sediments over the upper 50 cm can account for 65.3% of the total storage over the 95 cm depth. After 1961, there was a general decrease in sediment flux due to the construction of reservoir dams. Between 1961 and 1999, more terrestrial sources of OC were imported and buried due to climate and human disturbances around the watershed. Between 1999 and 2020, mangrove wetlands were destroyed and degraded due to extreme weather and natural factors. Degradation of mangrove wetlands under extreme weather and natural factors reduced the TOC content and OC burial fluxes. Since 2010, TOC content in the sediments has increased, probably due to higher water content, accumulation of litter and root growth. The OC source is dominated by the contribution from mangrove sources.
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To investigate the feeding effects of Acanthaster cf. solaris on Pocillopora damicornis and its molecular regulatory mechanisms, this study focused on the typical Pocillopora damicornis in the South China Sea, combining behavioral experiments, transcriptome sequencing, and enzyme activity assays of stomach tissue to systematically analyze the role of olfactory receptors in the feeding behavior of Acanthaster cf. solaris. The results showed that the expression of chemical receptor genes in the Acanthaster cf. solaris significantly changed during the feeding process on Pocillopora damicornis, with 89 genes being significantly upregulated and 335 genes being significantly downregulated. Further exploration of the upregulated genes revealed that five olfactory receptor genes suggested by the transcriptome, including gamma-aminobutyric acid type B receptor subunit 1-like and olfactory receptor 13-like, may play crucial roles in the recognition and feeding on Pocillopora damicornis. Meanwhile, feeding behavior significantly activated cellulase activity in the stomach tissues (p < 0.05), whereas the activities of phosphoenolpyruvate carboxykinase and lipase showed an increasing trend but did not reach statistical significance. This suggests that cellulase may be involved in the digestive process by enhancing the degradation of coral skeletons and zooxanthella cell walls. This study provides preliminary insights into the mediation of feeding behavior by key olfactory receptors in Acanthaster cf. solaris and offers important scientific references for further understanding the mechanisms behind population outbreaks.
To investigate the feeding effects of Acanthaster cf. solaris on Pocillopora damicornis and its molecular regulatory mechanisms, this study focused on the typical Pocillopora damicornis in the South China Sea, combining behavioral experiments, transcriptome sequencing, and enzyme activity assays of stomach tissue to systematically analyze the role of olfactory receptors in the feeding behavior of Acanthaster cf. solaris. The results showed that the expression of chemical receptor genes in the Acanthaster cf. solaris significantly changed during the feeding process on Pocillopora damicornis, with 89 genes being significantly upregulated and 335 genes being significantly downregulated. Further exploration of the upregulated genes revealed that five olfactory receptor genes suggested by the transcriptome, including gamma-aminobutyric acid type B receptor subunit 1-like and olfactory receptor 13-like, may play crucial roles in the recognition and feeding on Pocillopora damicornis. Meanwhile, feeding behavior significantly activated cellulase activity in the stomach tissues (p < 0.05), whereas the activities of phosphoenolpyruvate carboxykinase and lipase showed an increasing trend but did not reach statistical significance. This suggests that cellulase may be involved in the digestive process by enhancing the degradation of coral skeletons and zooxanthella cell walls. This study provides preliminary insights into the mediation of feeding behavior by key olfactory receptors in Acanthaster cf. solaris and offers important scientific references for further understanding the mechanisms behind population outbreaks.
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Zhoushan Fishing Ground (ZFG) is the largest fishing ground in China, with rich fishery resources. Under the effects of climate changes and anthropogenic disturbances, changes in local marine environment and selective fishing have increased spatial heterogeneity of habitat and function of the fish communities, and futher result in instability of ecosystem. Traditional studies were major focus on the spatial patterns of the fish communities based on taxonomic level in the ZFG. However, there are still knowledge gaps about the spatial patterns of the functional structure of the fish communities because of shortage in functional data of fishes. Here, we investigate the spatial patterns of the taxonomic and functional structures of the fish communities and their seasonal variations in ZFG, as well as their correlations with environmental variables. The fishery surveys were conducted in 4 seasons during 2006-2007. To measure the functional compositions of the fish communities, community-weighted mean trait values (CWMs) were calculated for each functional trait of fishes. β diversities were calculated to measure the spatial heterogeneity of the fish communities. Our results indicated that most of CWMs showed significant difference between at least two seasons. Taxonomic and functional β diversities showed high values with range from0.7423 ～0.8396 and 0.7184 ～0.7824 , respectively, indicating that the taxonomic and functional structures have high levels of spatial heterogeneity. In addition, the taxonomic β diversities showed significant change with seasons, and significantly related to water depth, salinity, and chemical oxygen demand (COD), while functional β diversities showed different patterns. The results contribute to a better understanding of the spatial patterns of the fish communities and their seasonal dynamics in ZFG, and guilde for biodiversity conservation and fishery resource management.
Zhoushan Fishing Ground (ZFG) is the largest fishing ground in China, with rich fishery resources. Under the effects of climate changes and anthropogenic disturbances, changes in local marine environment and selective fishing have increased spatial heterogeneity of habitat and function of the fish communities, and futher result in instability of ecosystem. Traditional studies were major focus on the spatial patterns of the fish communities based on taxonomic level in the ZFG. However, there are still knowledge gaps about the spatial patterns of the functional structure of the fish communities because of shortage in functional data of fishes. Here, we investigate the spatial patterns of the taxonomic and functional structures of the fish communities and their seasonal variations in ZFG, as well as their correlations with environmental variables. The fishery surveys were conducted in 4 seasons during 2006-2007. To measure the functional compositions of the fish communities, community-weighted mean trait values (CWMs) were calculated for each functional trait of fishes. β diversities were calculated to measure the spatial heterogeneity of the fish communities. Our results indicated that most of CWMs showed significant difference between at least two seasons. Taxonomic and functional β diversities showed high values with range from
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The intrusion of the Kuroshio into the South China Sea (SCS) has important effects on its circulation, thermohaline balance, mesoscale eddies and local climate. Kuroshio intrusion into the SCS predominantly occurs in winter and is relatively weaker during the summer-autumn (May–October). However, an analysis of observational data in the northeastern SCS in 2023 reveals that cyclonic mesoscale eddies on the western side of the Luzon Strait can significantly enhance summer-autumn Kuroshio intrusion into the SCS. The maximum observed salinity in the northeastern SCS reached 34.80. Further analysis integrating satellite altimetry and reanalysis data confirms that cyclonic eddies can induce Kuroshio intrusion into the SCS during the summer-autumn. The advection of the cyclonic eddies transported 3.05×1013 m3 of Kuroshio water into the SCS. A statistical analysis further identifies 25 occurrences of cyclonic eddy-induced Kuroshio intrusion into the SCS from 1993 and 2023. Over the 31 years, the additional summer-autumn water flux induced by cyclonic eddies has reached approximately 0.29 Sv, accounting for 8.1% of the total upper-layer flux in the Luzon Strait during summer and autumn. The north-south velocity asymmetry of cyclonic eddies is likely the primary mechanism enhancing Kuroshio intrusion into the SCS. These findings highlight the significant role of cyclonic eddy-induced Kuroshio intrusion during summer and autumn in facilitating water exchange between the SCS and the Northwest Pacific.
The intrusion of the Kuroshio into the South China Sea (SCS) has important effects on its circulation, thermohaline balance, mesoscale eddies and local climate. Kuroshio intrusion into the SCS predominantly occurs in winter and is relatively weaker during the summer-autumn (May–October). However, an analysis of observational data in the northeastern SCS in 2023 reveals that cyclonic mesoscale eddies on the western side of the Luzon Strait can significantly enhance summer-autumn Kuroshio intrusion into the SCS. The maximum observed salinity in the northeastern SCS reached 34.80. Further analysis integrating satellite altimetry and reanalysis data confirms that cyclonic eddies can induce Kuroshio intrusion into the SCS during the summer-autumn. The advection of the cyclonic eddies transported 3.05×1013 m3 of Kuroshio water into the SCS. A statistical analysis further identifies 25 occurrences of cyclonic eddy-induced Kuroshio intrusion into the SCS from 1993 and 2023. Over the 31 years, the additional summer-autumn water flux induced by cyclonic eddies has reached approximately 0.29 Sv, accounting for 8.1% of the total upper-layer flux in the Luzon Strait during summer and autumn. The north-south velocity asymmetry of cyclonic eddies is likely the primary mechanism enhancing Kuroshio intrusion into the SCS. These findings highlight the significant role of cyclonic eddy-induced Kuroshio intrusion during summer and autumn in facilitating water exchange between the SCS and the Northwest Pacific.
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To address the scarcity of high-resolution ocean subsurface temperature field data in the South China Sea (SCS), this study proposes a Generative Adversarial Network (GAN) for reconstructing high-resolution three-dimensional ocean temperature field based on the spatiotemporal correlation between ocean surface remote sensing observations and subsurface ocean temperature. The proposed GAN model is trained by multi-source ocean surface remote sensing data from 2013 to 2017, including sea surface temperature, sea surface salinity, sea level anomaly, and sea surface wind. The three-dimensional ocean temperature fields for 19 depth layers shallower than 541 meters in SCS in 2018 are reconstructed using the trained model and ocean surface multi-source remote sensing data. The ocean temperature fields reconstruction results are compared with GLORYS12V1 reanalysis data and Argo profile data to assess the feasibility of the proposed model. The results of experiments show that the spatial distribution characteristics of the reconstructed temperature field at different depth layers are in good agreement with the GLORYS12V1 reanalysis data, and can reflect the seasonal variation features of typical vertical cross-sections in the central SCS. The comparison of ocean temperature time series at three different locations in the SCS verifies the stability and accuracy of the proposed model. The evaluation experiments based on Argo in-situ observations show that the model can accurately reconstruct the vertical variation of real ocean temperature, demonstrating the practical application value of the proposed method. The average RMSE of the reconstructed three-dimensional temperature field in the South China Sea for 2018 is 0.704℃, which outperforms the CNN (0.952℃) and U-net (0.863℃) models.
To address the scarcity of high-resolution ocean subsurface temperature field data in the South China Sea (SCS), this study proposes a Generative Adversarial Network (GAN) for reconstructing high-resolution three-dimensional ocean temperature field based on the spatiotemporal correlation between ocean surface remote sensing observations and subsurface ocean temperature. The proposed GAN model is trained by multi-source ocean surface remote sensing data from 2013 to 2017, including sea surface temperature, sea surface salinity, sea level anomaly, and sea surface wind. The three-dimensional ocean temperature fields for 19 depth layers shallower than 541 meters in SCS in 2018 are reconstructed using the trained model and ocean surface multi-source remote sensing data. The ocean temperature fields reconstruction results are compared with GLORYS12V1 reanalysis data and Argo profile data to assess the feasibility of the proposed model. The results of experiments show that the spatial distribution characteristics of the reconstructed temperature field at different depth layers are in good agreement with the GLORYS12V1 reanalysis data, and can reflect the seasonal variation features of typical vertical cross-sections in the central SCS. The comparison of ocean temperature time series at three different locations in the SCS verifies the stability and accuracy of the proposed model. The evaluation experiments based on Argo in-situ observations show that the model can accurately reconstruct the vertical variation of real ocean temperature, demonstrating the practical application value of the proposed method. The average RMSE of the reconstructed three-dimensional temperature field in the South China Sea for 2018 is 0.704℃, which outperforms the CNN (0.952℃) and U-net (0.863℃) models.
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The transport of phosphorus by suspended sediment plays a pivotal role as a nutrient and ecological factor in aquatic environments, particularly in the complex hydrodynamic and sedimentary settings of Jiangsu's coastal tidal flats, where diverse organic coatings on sediment surfaces further complicate sediment dynamics. Investigating the impact of organic matter on both sediment transport and phosphorus adsorption processes, therefore, is crucial for predicting phosphorus dynamics in coastal tidal flats and nearshore waters. To elucidate the influence of organic matter content and sediment initiation characteristics on aqueous phosphorus concentrations, this study employs xanthan as a model organic substance. Through sediment initiation-resuspension-adsorption experiments and constant-temperature oscillation tests, the study systematically examines how xanthan alters sediment mobility and phosphorus adsorption under varying flow conditions. The research findings are as follows: 1) Xanthan significantly impedes the initiation of sediment motion from the bed, enhancing the bed's resistance to erosive shear stress by approximately twofold. 2) Sediment initiation characteristics act as a direct determinant in the adsorption of phosphorus by the bed sediment, a marked increase in aqueous phosphorus concentration is observed only after substantial sediment initiation commences. 3) While xanthan itself has negligible direct impact on phosphorus adsorption, it indirectly suppresses phosphorus adsorption by the bed sediment through inhibiting sediment initiation.
The transport of phosphorus by suspended sediment plays a pivotal role as a nutrient and ecological factor in aquatic environments, particularly in the complex hydrodynamic and sedimentary settings of Jiangsu's coastal tidal flats, where diverse organic coatings on sediment surfaces further complicate sediment dynamics. Investigating the impact of organic matter on both sediment transport and phosphorus adsorption processes, therefore, is crucial for predicting phosphorus dynamics in coastal tidal flats and nearshore waters. To elucidate the influence of organic matter content and sediment initiation characteristics on aqueous phosphorus concentrations, this study employs xanthan as a model organic substance. Through sediment initiation-resuspension-adsorption experiments and constant-temperature oscillation tests, the study systematically examines how xanthan alters sediment mobility and phosphorus adsorption under varying flow conditions. The research findings are as follows: 1) Xanthan significantly impedes the initiation of sediment motion from the bed, enhancing the bed's resistance to erosive shear stress by approximately twofold. 2) Sediment initiation characteristics act as a direct determinant in the adsorption of phosphorus by the bed sediment, a marked increase in aqueous phosphorus concentration is observed only after substantial sediment initiation commences. 3) While xanthan itself has negligible direct impact on phosphorus adsorption, it indirectly suppresses phosphorus adsorption by the bed sediment through inhibiting sediment initiation.
, Available online , doi: 10.12284/hyxb2025032
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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.
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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/hyxb2025001
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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.
, Available online , doi: 10.12284/hyxb2025019
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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 than
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.
, Available online , doi: 10.12284/hyxb2025038
Abstract:
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
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.
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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
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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.
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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/hyxb2025005
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.
, 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.
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Abstract:
This study compiled data on the 239+240Pu concentration or specific ratio-activity, 240Pu/239Pu atom ratio, and 239+240Pu flux or inventory in seawater, corals, shells and sediment samples in the Northern South China Sea. The 239+240Pu sources and trends in surface seawater, water columns, surface sediments, and sediment cores in this area were presented. According to the two end member model, global fallout (GF) and the Pacific Proving Grounds (PPG) were currently the sources of 239+240Pu in environmental samples investigated from the northern South China Sea. Meanwhile, according to the migration model, it was found for the first time that a positive linear relationship between the water depth corresponding to the 239+240Pu peak concentration in the water column and its migration rate. The correlation between the organic matter content or particle size of surface sediments and the 239+240Pu specific ratio-activity had a segmented nature, showing positive and negative correlations, respectively. The numerical result of the 239+240Pu chrono-marker sedimentation rate in sediment core samples was usually greater than or equal to the maximum apparent diffusion rate of relatively exchangeable 239+240Pu in the same core sample, and there was a significant positive linear relationship between the sedimentation rate and the maximum apparent diffusion rate, the maximum apparent diffusion rate of relatively exchangeable 239+240Pu does not affect the sedimentation rate.
This study compiled data on the 239+240Pu concentration or specific ratio-activity, 240Pu/239Pu atom ratio, and 239+240Pu flux or inventory in seawater, corals, shells and sediment samples in the Northern South China Sea. The 239+240Pu sources and trends in surface seawater, water columns, surface sediments, and sediment cores in this area were presented. According to the two end member model, global fallout (GF) and the Pacific Proving Grounds (PPG) were currently the sources of 239+240Pu in environmental samples investigated from the northern South China Sea. Meanwhile, according to the migration model, it was found for the first time that a positive linear relationship between the water depth corresponding to the 239+240Pu peak concentration in the water column and its migration rate. The correlation between the organic matter content or particle size of surface sediments and the 239+240Pu specific ratio-activity had a segmented nature, showing positive and negative correlations, respectively. The numerical result of the 239+240Pu chrono-marker sedimentation rate in sediment core samples was usually greater than or equal to the maximum apparent diffusion rate of relatively exchangeable 239+240Pu in the same core sample, and there was a significant positive linear relationship between the sedimentation rate and the maximum apparent diffusion rate, the maximum apparent diffusion rate of relatively exchangeable 239+240Pu does not affect the sedimentation rate.
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Abstract:
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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