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, Available online , doi: 10.12284/hyxb2025067
Abstract:
Sea surface gusts play a critical role in the utilization of ocean resources, marine research, and the safety of maritime transportation and offshore construction. However, current observation methods are limited, resulting in significant data gaps in surface gust measurements. Lin Jing et al. corrected sea surface wind speeds based on the difference in backscattering coefficients between the C and Ku bands observed by the HY-2B radar altimeter, thereby deriving gust wind speeds at nadir points, although the spatial coverage remained relatively limited. Building upon this approach, the present study employs the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) mission, whose observational principles are similar to those of radar altimeters. By utilizing the difference in Ku- and Ka-band backscattering coefficients and using ERA5 sea surface wind speed as a reference, surface wind speeds are corrected to retrieve gust speeds, aiming to expand observation coverage and improve observational efficiency. Validation against ERA5 gust data yields a correlation coefficient (r) of 0.96, a root mean square error (RMSE) of 1.79 m/s, a mean bias (Bias) of 0.73 m/s, and a standard deviation (Std) of 1.64 m/s. Comparison with simultaneous NDBC buoy observations shows an r of 0.91, an RMSE of 1.50 m/s, a Bias of −0.15 m/s, and a Std of 1.50 m/s, indicating that gust wind speeds retrieved from DPR data demonstrate good reliability. Furthermore, by replacing ERA5 sea surface wind speeds with NDBC buoy measurements, the r increases to 0.95, the RMSE decreases to 1.10 m/s, the Bias is −0.07 m/s, and the Std remains at 1.50 m/s, further improving the retrieval results. These findings highlight that accurate sea surface wind speeds have a significant positive impact on the accuracy of gust wind retrievals.
Sea surface gusts play a critical role in the utilization of ocean resources, marine research, and the safety of maritime transportation and offshore construction. However, current observation methods are limited, resulting in significant data gaps in surface gust measurements. Lin Jing et al. corrected sea surface wind speeds based on the difference in backscattering coefficients between the C and Ku bands observed by the HY-2B radar altimeter, thereby deriving gust wind speeds at nadir points, although the spatial coverage remained relatively limited. Building upon this approach, the present study employs the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) mission, whose observational principles are similar to those of radar altimeters. By utilizing the difference in Ku- and Ka-band backscattering coefficients and using ERA5 sea surface wind speed as a reference, surface wind speeds are corrected to retrieve gust speeds, aiming to expand observation coverage and improve observational efficiency. Validation against ERA5 gust data yields a correlation coefficient (r) of 0.96, a root mean square error (RMSE) of 1.79 m/s, a mean bias (Bias) of 0.73 m/s, and a standard deviation (Std) of 1.64 m/s. Comparison with simultaneous NDBC buoy observations shows an r of 0.91, an RMSE of 1.50 m/s, a Bias of −0.15 m/s, and a Std of 1.50 m/s, indicating that gust wind speeds retrieved from DPR data demonstrate good reliability. Furthermore, by replacing ERA5 sea surface wind speeds with NDBC buoy measurements, the r increases to 0.95, the RMSE decreases to 1.10 m/s, the Bias is −0.07 m/s, and the Std remains at 1.50 m/s, further improving the retrieval results. These findings highlight that accurate sea surface wind speeds have a significant positive impact on the accuracy of gust wind retrievals.
, Available online , doi: 10.12284/hyxb2025057
Abstract:
Mixed waves in the ocean typically consist of wind waves and swell in varying proportions. Due to research and application needs, it is often necessary to separate the wind waves from the swell. This paper focuses on four existing representative one-dimensional spectral wind-sea separation methods (1D methods): the PM method (Pierson-Moskowitz), the improved PM method, the JP method (Jesús-Portilla), and the spectral integral method. Using two-dimensional wave spectrum data provided by the spectrometer onboard the China-France Oceanography Satellite, a comparative analysis of the separation results under four wave-dominant conditions—pure wind waves, wind wave-dominant, swell-dominant, and pure swell—was conducted. The results show that: (1) The PM method and the improved PM method perform better under wind wave-dominant and swell-dominant conditions, respectively. (2) The JP method performs poorly overall and is insensitive to different wave-dominant conditions; the spectral integral method performs better when wind waves dominate. (3) As the proportion of swell in mixed waves increases, appropriately increasing the frequency ratio coefficient in the PM method can improve separation accuracy. Based on this, a piecewise PM method is proposed, which adjusts the frequency ratio coefficient. Under wind wave-dominant and swell-dominant conditions, using coefficients of 1.03 and 1.1, respectively, results in more accurate separation.
Mixed waves in the ocean typically consist of wind waves and swell in varying proportions. Due to research and application needs, it is often necessary to separate the wind waves from the swell. This paper focuses on four existing representative one-dimensional spectral wind-sea separation methods (1D methods): the PM method (Pierson-Moskowitz), the improved PM method, the JP method (Jesús-Portilla), and the spectral integral method. Using two-dimensional wave spectrum data provided by the spectrometer onboard the China-France Oceanography Satellite, a comparative analysis of the separation results under four wave-dominant conditions—pure wind waves, wind wave-dominant, swell-dominant, and pure swell—was conducted. The results show that: (1) The PM method and the improved PM method perform better under wind wave-dominant and swell-dominant conditions, respectively. (2) The JP method performs poorly overall and is insensitive to different wave-dominant conditions; the spectral integral method performs better when wind waves dominate. (3) As the proportion of swell in mixed waves increases, appropriately increasing the frequency ratio coefficient in the PM method can improve separation accuracy. Based on this, a piecewise PM method is proposed, which adjusts the frequency ratio coefficient. Under wind wave-dominant and swell-dominant conditions, using coefficients of 1.03 and 1.1, respectively, results in more accurate separation.
, Available online
Abstract:
The coastal estuarine ecosystem is a unique ecosystem formed at the confluence of rivers and oceans. It has high primary productivity, can provide food and habitat for many organisms, and plays an important role in maintaining the stability of ecosystem structure. In order to explore the temporal and spatial dynamics of phytoplankton community and its environmental impact factors in Liuqing River Bay, four cruises were carried out at seven sampling sites in Liuqing River Bay in winter (March), spring (May), summer (August) and autumn (October) of 2023. The results showed that a total of 97 species of phytoplankton belonging to 56 genera and 3 phyla were identified in the four cruises. The phytoplankton community structure was mainly composed of diatoms and dinoflagellates. The cell abundance of phytoplankton in Liuqing River Bay has obvious temporal and spatial dynamic changes. From the time dimension, the average abundance of phytoplankton in the four seasons from high to low is winter, autumn, summer and spring.In terms of spatial distribution, the phytoplankton abundance in Liuqing Bay reflects seasonal spatial distribution differences. The high abundance areas in spring, autumn and winter are concentrated in the northeast coastal waters, which are mainly driven by terrestrial input. The low abundance area is continuously distributed in the northwest sea area, which is mainly related to turbulent mixing. The overall spatial pattern is characterized by near-shore enrichment and offshore decline. The dominant species mainly include Cladophora in Bacillariophyta, Coscinodiscus in Ophiales, Chaetoceros capillipes, Chaetoceros spiralis, Coscinodiscus astromboides, Coscinodiscus grijsii and Chaetoceros capillipes, Chaetoceros tricornis in Pyrrophyta. The biodiversity in summer and autumn was significantly higher than that in spring and winter. The results of redundancy analysis showed that salinity, DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphorus) were the key environmental factors affecting the changes of phytoplankton community structure.
The coastal estuarine ecosystem is a unique ecosystem formed at the confluence of rivers and oceans. It has high primary productivity, can provide food and habitat for many organisms, and plays an important role in maintaining the stability of ecosystem structure. In order to explore the temporal and spatial dynamics of phytoplankton community and its environmental impact factors in Liuqing River Bay, four cruises were carried out at seven sampling sites in Liuqing River Bay in winter (March), spring (May), summer (August) and autumn (October) of 2023. The results showed that a total of 97 species of phytoplankton belonging to 56 genera and 3 phyla were identified in the four cruises. The phytoplankton community structure was mainly composed of diatoms and dinoflagellates. The cell abundance of phytoplankton in Liuqing River Bay has obvious temporal and spatial dynamic changes. From the time dimension, the average abundance of phytoplankton in the four seasons from high to low is winter, autumn, summer and spring.In terms of spatial distribution, the phytoplankton abundance in Liuqing Bay reflects seasonal spatial distribution differences. The high abundance areas in spring, autumn and winter are concentrated in the northeast coastal waters, which are mainly driven by terrestrial input. The low abundance area is continuously distributed in the northwest sea area, which is mainly related to turbulent mixing. The overall spatial pattern is characterized by near-shore enrichment and offshore decline. The dominant species mainly include Cladophora in Bacillariophyta, Coscinodiscus in Ophiales, Chaetoceros capillipes, Chaetoceros spiralis, Coscinodiscus astromboides, Coscinodiscus grijsii and Chaetoceros capillipes, Chaetoceros tricornis in Pyrrophyta. The biodiversity in summer and autumn was significantly higher than that in spring and winter. The results of redundancy analysis showed that salinity, DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphorus) were the key environmental factors affecting the changes of phytoplankton community structure.
, Available online , doi: 10.12284/hyxb2025050
Abstract:
To understand the characteristics of fish communities in the upwelling waters of the West-central South China Sea, data from the 2014 summer light falling-net fishery resources survey were utilized to study the species composition, biodiversity, and community structure of phototropic pelagic fish communities. There are 13 fish species in the upwelling core region, belonging to 11 genera in 3 orders and 8 families, with the dominant species being the Cubiceps squamiceps; 11 species of fish were collected from the upwelling periphery region, belonging to 10 genera in 2 orders and 8 families, with the dominant species being the Auxis thazard and Thunnus obesus. The fish diversity index, richness index, and evenness index were lower in the upwelling core region than in the periphery waters. The average catch rate in the upwelling core region was 45.9 kg/h, 1.63 times higher than that in the periphery region. PERMANOVA analysis showed that the fish communities in the upwelling core region and the periphery region had marginally significant differences in fish communities, with the main divergent species being Cubiceps squamiceps, Auxis thazard, Decapterus macrosoma, Thunnus obesus, and Auxis rochei. Correlation analysis showed that sea surface chlorophyll a mass concentration was the most important environmental factor influencing the spatial distribution of fish abundance.
To understand the characteristics of fish communities in the upwelling waters of the West-central South China Sea, data from the 2014 summer light falling-net fishery resources survey were utilized to study the species composition, biodiversity, and community structure of phototropic pelagic fish communities. There are 13 fish species in the upwelling core region, belonging to 11 genera in 3 orders and 8 families, with the dominant species being the Cubiceps squamiceps; 11 species of fish were collected from the upwelling periphery region, belonging to 10 genera in 2 orders and 8 families, with the dominant species being the Auxis thazard and Thunnus obesus. The fish diversity index, richness index, and evenness index were lower in the upwelling core region than in the periphery waters. The average catch rate in the upwelling core region was 45.9 kg/h, 1.63 times higher than that in the periphery region. PERMANOVA analysis showed that the fish communities in the upwelling core region and the periphery region had marginally significant differences in fish communities, with the main divergent species being Cubiceps squamiceps, Auxis thazard, Decapterus macrosoma, Thunnus obesus, and Auxis rochei. Correlation analysis showed that sea surface chlorophyll a mass concentration was the most important environmental factor influencing the spatial distribution of fish abundance.
, Available online , doi: 10.12284/hyxb2025086
Abstract:
To evaluate whether the “ensemble approach” can enhance the predictive performance of Species Distribution Models (SDMs) in dynamically changing estuarine environments, this study utilized eight single models based on different algorithms to construct an Ensemble Model (EM) for the habitat of Harpadon nehereus, a dominant species in the Changjiang River Estuary. The data used for modeling were derived from marine biological resource surveys conducted in the Changjiang River Estuary from 2013 to 2021. The results showed that: (1) All single models outperformed the random distribution model, with the EM demonstrating the highest predictive accuracy and robustness (Area Under receiver operating character Curve, AUC = 0.875; True skill statistic, TSS = 0.650; KAPPA = 0.560; Overall accuracy, OA = 0.867). (2) The EM accurately identified both presence and absence stations of H. nehereus, clearly differentiated suitability levels in unsampled regions, and predicted areas of high suitability shared by different models. (3) Finally, the EM accurately identified the key environmental requirements of H. nehereus and reflected the central tendency across multiple models. The most suitable habitat for H. nehereus was found in waters with salinity, temperature, and chemical oxygen demand ranges of 2.754−30.300, 28.278−30.934℃, and 4.605−8.080 mg/L, respectively. This study provides a more reliable research method for the sustainable utilization and habitat protection of H. nehereus resources in the Changjiang River Estuary.
To evaluate whether the “ensemble approach” can enhance the predictive performance of Species Distribution Models (SDMs) in dynamically changing estuarine environments, this study utilized eight single models based on different algorithms to construct an Ensemble Model (EM) for the habitat of Harpadon nehereus, a dominant species in the Changjiang River Estuary. The data used for modeling were derived from marine biological resource surveys conducted in the Changjiang River Estuary from 2013 to 2021. The results showed that: (1) All single models outperformed the random distribution model, with the EM demonstrating the highest predictive accuracy and robustness (Area Under receiver operating character Curve, AUC = 0.875; True skill statistic, TSS = 0.650; KAPPA = 0.560; Overall accuracy, OA = 0.867). (2) The EM accurately identified both presence and absence stations of H. nehereus, clearly differentiated suitability levels in unsampled regions, and predicted areas of high suitability shared by different models. (3) Finally, the EM accurately identified the key environmental requirements of H. nehereus and reflected the central tendency across multiple models. The most suitable habitat for H. nehereus was found in waters with salinity, temperature, and chemical oxygen demand ranges of 2.754−30.300, 28.278−30.934℃, and 4.605−8.080 mg/L, respectively. This study provides a more reliable research method for the sustainable utilization and habitat protection of H. nehereus resources in the Changjiang River Estuary.
, Available online , doi: 10.12284/hyxb2025078
Abstract:
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
Abstract:
Accurate parameterization of the momentum flux plays a decisive role in ocean and atmospheric hazards and climate change. However, the Wave Coherent (WC) stress, as one of the uncertainties factors, modulates the momentum flux severely. In this paper, the WC stress is extracted from the observation obtained from the South China Sea in 2012. The observation shows that the contribution of WC stress to total wind stress relies on the angle difference between wind and wave direction: it approaches zero when the angle difference is 90° and accounts for 20～25% when the angle is ～180°. To describe the WC stress, the scheme of Janssen (J91) and Zou et al. (2024) (Z24) is compared. The result shows that J91 can underestimate the WC stress by about 1～2 orders of magnitude, while Z24 behaves better. The WC stress given by J91 decreases with height, leading to a non-effect on wind profile; while WC stress given by Z24 first increases then decreases, with the height of its maximum being influenced by atmospheric stability, which leads to higher wind speeds near (or away from) the sea surface under stable (or unstable) conditions compared to the J91 scheme when swell exerted upward momentum flux. A new method to parameterize the momentum flux is also given by including the WC stress in this paper; the result shows that it has a high correlation coefficient in the wind speed range of 3–7 m/s and a smaller overall sample bias than the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.5.
Accurate parameterization of the momentum flux plays a decisive role in ocean and atmospheric hazards and climate change. However, the Wave Coherent (WC) stress, as one of the uncertainties factors, modulates the momentum flux severely. In this paper, the WC stress is extracted from the observation obtained from the South China Sea in 2012. The observation shows that the contribution of WC stress to total wind stress relies on the angle difference between wind and wave direction: it approaches zero when the angle difference is 90° and accounts for 20～25% when the angle is ～180°. To describe the WC stress, the scheme of Janssen (J91) and Zou et al. (2024) (Z24) is compared. The result shows that J91 can underestimate the WC stress by about 1～2 orders of magnitude, while Z24 behaves better. The WC stress given by J91 decreases with height, leading to a non-effect on wind profile; while WC stress given by Z24 first increases then decreases, with the height of its maximum being influenced by atmospheric stability, which leads to higher wind speeds near (or away from) the sea surface under stable (or unstable) conditions compared to the J91 scheme when swell exerted upward momentum flux. A new method to parameterize the momentum flux is also given by including the WC stress in this paper; the result shows that it has a high correlation coefficient in the wind speed range of 3–7 m/s and a smaller overall sample bias than the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.5.
, Available online
Abstract:
Observations indicate that the substantial freshwater transported to the southern part of the Makassar Strait by the South China Sea Throughflow (SCSTF) can influence the Indonesian Throughflow (ITF) via the “Freshwater Plug” effect. This article has conducted a series of numerical experiments and discovered that when the salinity in the Karimata Strait increased to that in the Makassar Strait, the volume and freshwater transport through the Karimata Strait are 3.52 Sv and 184.03 mSv, with an increase of 4.31% and a decrease of 27.27% compared with the control experiment, respectively. In the meantime, the volume transport in the upper 50m of the Makassar Strait is 0.11 Sv, with an increase of 34.69%. When the salinity in the Karimata Strait decreased by 0.1−0.6 psu, the volume and freshwater transport through the Karimata Strait are 3.37 Sv and 294.44 mSv, with a decrease of 1.57% and an increase of 16.37% compared with the control experiment, respectively. Also, the volume transport in the upper 50m of the Makassar Strait is 0.07 Sv, with a decrease of 34.69%. These have proved the influence of freshwater transported by SCSTF on ITF. Comparing the salinity relaxation experiment with the topography closed experiment, the salinity relaxation experiment allows for significant changes in the freshwater transport through the Karimata Strait while only modestly affecting the volume transport. This enables an analysis of the impact of SCSTF’s surface water with low salinity on ITF. Meanwhile, we have compared the salinity relaxation experiment with the rainfall closed experiment, and the important impact of low salinity water transport in the South China Sea through the Karimata Strait to the Java Sea on the ITF in boreal winter is further verified.
Observations indicate that the substantial freshwater transported to the southern part of the Makassar Strait by the South China Sea Throughflow (SCSTF) can influence the Indonesian Throughflow (ITF) via the “Freshwater Plug” effect. This article has conducted a series of numerical experiments and discovered that when the salinity in the Karimata Strait increased to that in the Makassar Strait, the volume and freshwater transport through the Karimata Strait are 3.52 Sv and 184.03 mSv, with an increase of 4.31% and a decrease of 27.27% compared with the control experiment, respectively. In the meantime, the volume transport in the upper 50m of the Makassar Strait is 0.11 Sv, with an increase of 34.69%. When the salinity in the Karimata Strait decreased by 0.1−0.6 psu, the volume and freshwater transport through the Karimata Strait are 3.37 Sv and 294.44 mSv, with a decrease of 1.57% and an increase of 16.37% compared with the control experiment, respectively. Also, the volume transport in the upper 50m of the Makassar Strait is 0.07 Sv, with a decrease of 34.69%. These have proved the influence of freshwater transported by SCSTF on ITF. Comparing the salinity relaxation experiment with the topography closed experiment, the salinity relaxation experiment allows for significant changes in the freshwater transport through the Karimata Strait while only modestly affecting the volume transport. This enables an analysis of the impact of SCSTF’s surface water with low salinity on ITF. Meanwhile, we have compared the salinity relaxation experiment with the rainfall closed experiment, and the important impact of low salinity water transport in the South China Sea through the Karimata Strait to the Java Sea on the ITF in boreal winter is further verified.
, Available online , doi: 10.12284/hyxb2025061
Abstract:
El Niño-Southern Oscillation (ENSO), as the most prominent interannual variability signal in the climate system, exerts significant impacts on global weather and climate. Under global warming, ENSO evolution has increasingly exhibited the characteristics of complex and diverse rendering its simulation and prediction a particularly challenging subject within climatology. This study introduces 3D-Geoformer, an advanced multi-variable intelligent prediction model for the tropical sea-air system based on Transformer architecture, to conduct error analysis and correction research for ENSO predictions. Unlike many existing models that focus solely on univariate fields or time series related to ENSO, the 3D-Geoformer model achieves accurate characterization and prediction of the multi-variable three-dimensional field of the tropical Pacific sea-air system while preserving the integrity of the physical processes essential for ENSO prediction. To address specific issues in ENSO predictions by the 3D-Geoformer model, such as low spring forecasting skills, weak SST forecasting ability in the western equatorial Pacific, and inadequate forecasting intensity for extreme ENSO events, this study proposes a seasonal forecasting error correction technique based on empirical orthogonal function (EOF) decomposition. This method is applied to correct the prediction results of the 3D-Geoformer model. During the construction phase of the correction relationship, EOF analysis was used to establish the linear relationship between the principal component sequences of the multivariable prediction field and the prediction error field from 1983 to 2009. Subsequently, this relationship was utilized for subsequent error corrections. In the testing phase, the EOF principal component coefficients of the prediction field and their linear relationships with the main components of the error were employed to calculate the corresponding principal components of the prediction error, thereby obtaining the prediction error field and the corrected prediction field. The experimental results indicate that when the 3D-Geoformer model is employed for forecasting the sea - surface temperature (SST) in the western equatorial Pacific, the prediction error remains below 0.15 °C. Notably, the prediction bias of the 3D-Geoformer model regarding the sea temperature in the western equatorial Pacific, induced by the “cold tongue bias” inherent in climate models, is substantially mitigated. Concurrently, there is a remarkable 46.7% reduction in the prediction error of the sea-surface temperature (SST) in the central and eastern equatorial Pacific. Through a meticulous comparison of the disparities in the anomaly correlation coefficients (ACC) between the SST prediction outcomes of the 3D-Geoformer model with and without Empirical Orthogonal Function (EOF) correction in the equatorial Pacific, it is discerned that positive-value regions are consistently present in the ACC differences. This finding strongly suggests that the EOF-corrected model exhibits enhanced prediction accuracy, effectively alleviating the “cold tongue bias” issue arising from the utilization of climate model data from the Sixth Coupled Model Inter-comparison Project (CMIP6) during the training phase of the 3D-Geoformer model. For the 2015−2016 El Niño event, forecast corrections made 12 months in advance show that the SST error in the western equatorial Pacific is controlled within 0.5°C, and the SST error in the eastern equatorial Pacific is reduced by approximately 75%, with the error range narrowed to within ±0.5°C. This study underscores the application value of the seasonal forecast error correction method based on EOF decomposition in enhancing model prediction accuracy, providing a novel approach to improving the precision of ENSO intelligent predictions, and offering new insights into simulation prediction and error analysis in earth science.
El Niño-Southern Oscillation (ENSO), as the most prominent interannual variability signal in the climate system, exerts significant impacts on global weather and climate. Under global warming, ENSO evolution has increasingly exhibited the characteristics of complex and diverse rendering its simulation and prediction a particularly challenging subject within climatology. This study introduces 3D-Geoformer, an advanced multi-variable intelligent prediction model for the tropical sea-air system based on Transformer architecture, to conduct error analysis and correction research for ENSO predictions. Unlike many existing models that focus solely on univariate fields or time series related to ENSO, the 3D-Geoformer model achieves accurate characterization and prediction of the multi-variable three-dimensional field of the tropical Pacific sea-air system while preserving the integrity of the physical processes essential for ENSO prediction. To address specific issues in ENSO predictions by the 3D-Geoformer model, such as low spring forecasting skills, weak SST forecasting ability in the western equatorial Pacific, and inadequate forecasting intensity for extreme ENSO events, this study proposes a seasonal forecasting error correction technique based on empirical orthogonal function (EOF) decomposition. This method is applied to correct the prediction results of the 3D-Geoformer model. During the construction phase of the correction relationship, EOF analysis was used to establish the linear relationship between the principal component sequences of the multivariable prediction field and the prediction error field from 1983 to 2009. Subsequently, this relationship was utilized for subsequent error corrections. In the testing phase, the EOF principal component coefficients of the prediction field and their linear relationships with the main components of the error were employed to calculate the corresponding principal components of the prediction error, thereby obtaining the prediction error field and the corrected prediction field. The experimental results indicate that when the 3D-Geoformer model is employed for forecasting the sea - surface temperature (SST) in the western equatorial Pacific, the prediction error remains below 0.15 °C. Notably, the prediction bias of the 3D-Geoformer model regarding the sea temperature in the western equatorial Pacific, induced by the “cold tongue bias” inherent in climate models, is substantially mitigated. Concurrently, there is a remarkable 46.7% reduction in the prediction error of the sea-surface temperature (SST) in the central and eastern equatorial Pacific. Through a meticulous comparison of the disparities in the anomaly correlation coefficients (ACC) between the SST prediction outcomes of the 3D-Geoformer model with and without Empirical Orthogonal Function (EOF) correction in the equatorial Pacific, it is discerned that positive-value regions are consistently present in the ACC differences. This finding strongly suggests that the EOF-corrected model exhibits enhanced prediction accuracy, effectively alleviating the “cold tongue bias” issue arising from the utilization of climate model data from the Sixth Coupled Model Inter-comparison Project (CMIP6) during the training phase of the 3D-Geoformer model. For the 2015−2016 El Niño event, forecast corrections made 12 months in advance show that the SST error in the western equatorial Pacific is controlled within 0.5°C, and the SST error in the eastern equatorial Pacific is reduced by approximately 75%, with the error range narrowed to within ±0.5°C. This study underscores the application value of the seasonal forecast error correction method based on EOF decomposition in enhancing model prediction accuracy, providing a novel approach to improving the precision of ENSO intelligent predictions, and offering new insights into simulation prediction and error analysis in earth science.
, Available online , doi: 10.12284/hyxb2025063
Abstract:
Based on actual wave measurement data, combined with stochastic wave theory and the JONSWAP spectrum, the probability of freak waves in the northwest part of the South China Sea was conducted. The characteristics of the number of freak waves and wave elements in the sea area were statistically analyzed by the buoy observation data, and the correlation characteristics between the effective wave height and the main parameters such as period and wind speed were explored. The results indicate that the occurrence probability of freak waves in the northwestern South China Sea is0.0059 %. Analyzing the distribution of the significant wave steepness δ in different seasons of this area, it was found that the frequency of swells in the waves is relatively high during the spring transition period and the southwest monsoon season, which may be one of the reasons for the relatively high probability of freak wave occurrences in these two seasons. Regarding the annual distribution characteristics, there is a high correlation between significant wave height and mean period, while freak waves show virtually no correlation. The correlation coefficient between annual significant wave height and wind speed is 0.83, and for freak waves, it is 0.63, indicating that the annual distribution of waves is greatly influenced by wind waves. The relative proportion of swells in the mixed zone of wind waves and swells may have a certain impact on the generation of freak waves.
Based on actual wave measurement data, combined with stochastic wave theory and the JONSWAP spectrum, the probability of freak waves in the northwest part of the South China Sea was conducted. The characteristics of the number of freak waves and wave elements in the sea area were statistically analyzed by the buoy observation data, and the correlation characteristics between the effective wave height and the main parameters such as period and wind speed were explored. The results indicate that the occurrence probability of freak waves in the northwestern South China Sea is
, Available online
Abstract:
Symbiodiniaceae are indispensable partners in the coral symbiotic system, and different species exhibit varying sensitivities to environmental stress, thereby influencing the environmental adaptability of their coral hosts. This study investigates the stress response patterns of two widely distributed coral symbiotic Symbiodiniaceae species—environmentally sensitive Cladocopium goreaui (C. goreaui) and environmentally tolerant Durusdinium trenchii (D. trenchii)—under heat stress from the perspective of lipid metabolism. The results showed that heat stress significantly affected their cell density, photosynthetic pigment content, photochemical efficiency of photosystem II (Fv/Fm), and antioxidant activity, with statistically significant differences (P < 0.05). Lipidomics revealed that lipid-differentiated metabolites such as phosphatidylcholine, triglycerides, phosphatidylethanolamine and lysophosphatidylcholine were significantly enriched in glycerophospholipid metabolism, triglyceride metabolism, and polyunsaturated fatty acid-related metabolic pathways in response to heat stress in C. goreaui and D. trenchii. Notably, the two species exhibited significant differences in sphingolipid metabolism: D. trenchii downregulated ceramide levels to reduce oxidative stress damage, regulate autophagy, and adapt to changes in membrane fluidity, whereas C. goreaui primarily upregulated lipid molecules rich in polyunsaturated fatty acids to maintain membrane stability and regulate signal transduction. A deeper understanding of the lipid metabolic stress response mechanisms of Symbiodiniaceae with different environmental sensitivities under heat stress provides new insights into enhancing coral adaptability to environmental changes from a symbiotic partner perspective.
Symbiodiniaceae are indispensable partners in the coral symbiotic system, and different species exhibit varying sensitivities to environmental stress, thereby influencing the environmental adaptability of their coral hosts. This study investigates the stress response patterns of two widely distributed coral symbiotic Symbiodiniaceae species—environmentally sensitive Cladocopium goreaui (C. goreaui) and environmentally tolerant Durusdinium trenchii (D. trenchii)—under heat stress from the perspective of lipid metabolism. The results showed that heat stress significantly affected their cell density, photosynthetic pigment content, photochemical efficiency of photosystem II (Fv/Fm), and antioxidant activity, with statistically significant differences (P < 0.05). Lipidomics revealed that lipid-differentiated metabolites such as phosphatidylcholine, triglycerides, phosphatidylethanolamine and lysophosphatidylcholine were significantly enriched in glycerophospholipid metabolism, triglyceride metabolism, and polyunsaturated fatty acid-related metabolic pathways in response to heat stress in C. goreaui and D. trenchii. Notably, the two species exhibited significant differences in sphingolipid metabolism: D. trenchii downregulated ceramide levels to reduce oxidative stress damage, regulate autophagy, and adapt to changes in membrane fluidity, whereas C. goreaui primarily upregulated lipid molecules rich in polyunsaturated fatty acids to maintain membrane stability and regulate signal transduction. A deeper understanding of the lipid metabolic stress response mechanisms of Symbiodiniaceae with different environmental sensitivities under heat stress provides new insights into enhancing coral adaptability to environmental changes from a symbiotic partner perspective.
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This study is based on survey data of fish communities in the Zhoushan fishing ground and uses a resampling technique to simulate the random loss of rare and common species. It also employs a biomass proportion reduction method to simulate scenarios of biomass loss, in order to explore the mechanisms by which the loss of different ecological groups affects functional diversity in fish communities. The results show that although rare species account for only 3% of the total community biomass, their species richness constitutes nearly 40% of the community, indicating an important ecological niche within the community structure. The simulation of species loss scenarios revealed that the loss of rare species’ richness directly impacts the functional diversity indices, specifically leading to a decrease in functional richness and an increase in functional evenness, while functional divergence and Rao’s quadratic entropy indices showed no significant changes. In contrast, the loss of common species’ richness resulted in a decline in functional richness, while the other three functional diversity indices remained relatively stable. Under the biomass loss scenarios, the reduction in rare species’ biomass led to unchanged functional richness but declines in functional evenness, functional divergence, and Rao’s quadratic entropy indices. The functional evenness index exhibited a nonlinear decline that started slowly and then accelerated, while the other two indices showed linear decreasing patterns. In contrast, the loss of common species’ biomass caused the latter three indices to decline in a pattern that started rapidly and then slowed down. Rare species occupy unique functional niches in the community, with their functional traits distributed at the edges of the multidimensional functional space. They play a unique role in maintaining community functional diversity. Strengthening the protection of rare species and their habitats is a key strategy for maintaining regional ecosystem diversity and stability.
This study is based on survey data of fish communities in the Zhoushan fishing ground and uses a resampling technique to simulate the random loss of rare and common species. It also employs a biomass proportion reduction method to simulate scenarios of biomass loss, in order to explore the mechanisms by which the loss of different ecological groups affects functional diversity in fish communities. The results show that although rare species account for only 3% of the total community biomass, their species richness constitutes nearly 40% of the community, indicating an important ecological niche within the community structure. The simulation of species loss scenarios revealed that the loss of rare species’ richness directly impacts the functional diversity indices, specifically leading to a decrease in functional richness and an increase in functional evenness, while functional divergence and Rao’s quadratic entropy indices showed no significant changes. In contrast, the loss of common species’ richness resulted in a decline in functional richness, while the other three functional diversity indices remained relatively stable. Under the biomass loss scenarios, the reduction in rare species’ biomass led to unchanged functional richness but declines in functional evenness, functional divergence, and Rao’s quadratic entropy indices. The functional evenness index exhibited a nonlinear decline that started slowly and then accelerated, while the other two indices showed linear decreasing patterns. In contrast, the loss of common species’ biomass caused the latter three indices to decline in a pattern that started rapidly and then slowed down. Rare species occupy unique functional niches in the community, with their functional traits distributed at the edges of the multidimensional functional space. They play a unique role in maintaining community functional diversity. Strengthening the protection of rare species and their habitats is a key strategy for maintaining regional ecosystem diversity and stability.
, Available online , doi: 10.12284/hyxb2025053
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This paper studies the asymmetric characteristics and mechanism of the anticyclonic jet at the bottom of seamounts by using the mooring observation data collected at the Caiwei seamount (CS) in the tropical western Pacific Ocean and an ideal two-layer model. The observation of bottom currents shows that there is an asymmetric anticyclonic jet phenomenon in the east-west direction at the bottom of the seamount. The two-layer model reproduces the bottom flow field and its asymmetric characteristics of the ideal seamount and CS, suggesting that the main source of asymmetry is the vorticity change caused by the energy input of background currents and the geostrophic and topographic β effects. The flow field characteristics are analyzed through the principle of potential vorticity conservation, and the mechanism of vorticity change affecting the bottom jet and its asymmetric characteristics is explained. In addition, this paper also discusses the influence of other environmental parameters on the bottom anticyclonic jet.
This paper studies the asymmetric characteristics and mechanism of the anticyclonic jet at the bottom of seamounts by using the mooring observation data collected at the Caiwei seamount (CS) in the tropical western Pacific Ocean and an ideal two-layer model. The observation of bottom currents shows that there is an asymmetric anticyclonic jet phenomenon in the east-west direction at the bottom of the seamount. The two-layer model reproduces the bottom flow field and its asymmetric characteristics of the ideal seamount and CS, suggesting that the main source of asymmetry is the vorticity change caused by the energy input of background currents and the geostrophic and topographic β effects. The flow field characteristics are analyzed through the principle of potential vorticity conservation, and the mechanism of vorticity change affecting the bottom jet and its asymmetric characteristics is explained. In addition, this paper also discusses the influence of other environmental parameters on the bottom anticyclonic jet.
, Available online
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Global warming and extreme thermal events have induced widespread coral bleaching, leading to the rapid degradation of coral reef ecosystems across the globe. Identifying functional genes associated with thermotolerance is crucial for elucidating coral adaptation mechanisms to climate warming and enabling scientific predictions regarding coral reef ecosystem trajectories. However, the current understanding of the molecular mechanism of coral holobiont in response to heat stress is very insufficient. Therefore, this paper reviews the research progress of functional genes related to coral thermal adaptation. Initially, pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), play a crucial role in detecting heat stress and activating downstream signaling cascades, thereby initiating the immune response process. These responses primarily involve: upregulation of heat shock proteins (HSPs) to facilitate the refolding of denatured polypeptides; induction of antioxidant protein genes to mitigate oxidative damage caused by reactive oxygen species (ROS); genes associated with apoptosis and pyroptosis play a crucial role in eliminating "harmful" cells. As thermal stress intensifies, corals initiate a sophisticated network of cellular processes to maintain. As heat stress intensifies, corals initiate a series of complex processes to jointly maintain cellular homeostasis. This includes: rapid activation of photoprotective protein genes to repair the photosynthetic apparatus of Symbiodiniaceae; expression of host fluorescent proteins to maintain redox balance; calcium channel proteins maintain the stability of intracellular Ca2+ levels; modulation of metabolic pathways to ensure adequate nutrient supply; inhibition of cell cycle progression to conserve energy; maintenance of cytoskeletal integrity to preserve structural stability; and regulation of ubiquitin-proteasome system for protein quality control. Furthermore, recurrent thermal stress events can induce acclimatization in corals, potentially enhancing their thermal tolerance through multiple mechanisms: downregulation of host metabolic rate, protection of heat-sensitive proteins, and upregulation of antioxidant enzymes and ammonium assimilation pathways.
Global warming and extreme thermal events have induced widespread coral bleaching, leading to the rapid degradation of coral reef ecosystems across the globe. Identifying functional genes associated with thermotolerance is crucial for elucidating coral adaptation mechanisms to climate warming and enabling scientific predictions regarding coral reef ecosystem trajectories. However, the current understanding of the molecular mechanism of coral holobiont in response to heat stress is very insufficient. Therefore, this paper reviews the research progress of functional genes related to coral thermal adaptation. Initially, pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), play a crucial role in detecting heat stress and activating downstream signaling cascades, thereby initiating the immune response process. These responses primarily involve: upregulation of heat shock proteins (HSPs) to facilitate the refolding of denatured polypeptides; induction of antioxidant protein genes to mitigate oxidative damage caused by reactive oxygen species (ROS); genes associated with apoptosis and pyroptosis play a crucial role in eliminating "harmful" cells. As thermal stress intensifies, corals initiate a sophisticated network of cellular processes to maintain. As heat stress intensifies, corals initiate a series of complex processes to jointly maintain cellular homeostasis. This includes: rapid activation of photoprotective protein genes to repair the photosynthetic apparatus of Symbiodiniaceae; expression of host fluorescent proteins to maintain redox balance; calcium channel proteins maintain the stability of intracellular Ca2+ levels; modulation of metabolic pathways to ensure adequate nutrient supply; inhibition of cell cycle progression to conserve energy; maintenance of cytoskeletal integrity to preserve structural stability; and regulation of ubiquitin-proteasome system for protein quality control. Furthermore, recurrent thermal stress events can induce acclimatization in corals, potentially enhancing their thermal tolerance through multiple mechanisms: downregulation of host metabolic rate, protection of heat-sensitive proteins, and upregulation of antioxidant enzymes and ammonium assimilation pathways.
, Available online
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Nearshore coral reefs are frequently subjected to prolonged exposure to high levels of suspended particulate matter (SPM). However, the tolerance threshold of scleractinian corals to SPM remains inadequatedly understood, complicating the protection and management of nearshore scleractinian coral communities. In this study, we investigated the physiological responses of Dipsastraea speciosa and Cyphastrea sp., the dominant species of scleractinian corals in the Dongshan waters, which represent the northern distribution limit of scleractinian coral communities, under varying SPM concentrations (0 mg/L, 35 mg/L, 50 mg/L and 100 mg/L). A SPM-controlled simulated system was employed by injecting SPM into experimental tanks to regulate its concentration over a 28-day period. Morphological characteristics and a series of photosynthetic physiological parameters were used as indicators. The results indicated that the polyps of both coral species exposed to three groups of SPM treatments exhibited shrinkageduring the initial stages of the experiment, but quickly recovered over time. No individual of coral bleaching or mortality were observed. Additionally, both coral species demonstrated significant photosynthetic physiological plasticity, evidenced by rising ΦPSII values with SPM concentration increased, reaching a maximum at 100 mg/L. This suggests that the two coral species can mitigate light shading by enhancing their photosynthetic efficiency in response to high SPM concentrations. Furthermore, Fv/Fm ratios, chlorophyll content, and zooxanthella density for both coral species remained relatively stable under high SPM exposure, indicating that their photosynthetic performance remained healthy despite elevated SPM levels. This implies that the tolerance threshold of these two scleractinian corals to SPM may exceed 100 mg/L. This study is the first experiment in China to successfully maintain high SPM levels over an extended period, and the findings provide essential data for the protection and management of scleractinian coral communities in China.
Nearshore coral reefs are frequently subjected to prolonged exposure to high levels of suspended particulate matter (SPM). However, the tolerance threshold of scleractinian corals to SPM remains inadequatedly understood, complicating the protection and management of nearshore scleractinian coral communities. In this study, we investigated the physiological responses of Dipsastraea speciosa and Cyphastrea sp., the dominant species of scleractinian corals in the Dongshan waters, which represent the northern distribution limit of scleractinian coral communities, under varying SPM concentrations (0 mg/L, 35 mg/L, 50 mg/L and 100 mg/L). A SPM-controlled simulated system was employed by injecting SPM into experimental tanks to regulate its concentration over a 28-day period. Morphological characteristics and a series of photosynthetic physiological parameters were used as indicators. The results indicated that the polyps of both coral species exposed to three groups of SPM treatments exhibited shrinkageduring the initial stages of the experiment, but quickly recovered over time. No individual of coral bleaching or mortality were observed. Additionally, both coral species demonstrated significant photosynthetic physiological plasticity, evidenced by rising ΦPSII values with SPM concentration increased, reaching a maximum at 100 mg/L. This suggests that the two coral species can mitigate light shading by enhancing their photosynthetic efficiency in response to high SPM concentrations. Furthermore, Fv/Fm ratios, chlorophyll content, and zooxanthella density for both coral species remained relatively stable under high SPM exposure, indicating that their photosynthetic performance remained healthy despite elevated SPM levels. This implies that the tolerance threshold of these two scleractinian corals to SPM may exceed 100 mg/L. This study is the first experiment in China to successfully maintain high SPM levels over an extended period, and the findings provide essential data for the protection and management of scleractinian coral communities in China.
, Available online , doi: 10.12284/hyxb2025084
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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 , doi: 10.12284/hyxb2025072
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Mytilus coruscus is renowned for its delicious taste and rich nutritional content, making it one of the significant economic shellfish along the coast of China. The critical period for M. coruscus seedling cultivation lies in its larval metamorphosis stage. However, the larval development of M. coruscus is a dynamic and complex process, involving the participation of numerous genes and various intricate biological processes. In this study, we based on high-throughput transcriptome sequencing technology, conducted transcriptome sequencing on larval samples of M. coruscus at five key developmental stages (Trocophore, D-veliger, Umbo, Pediveliger, and Post-larvae), identifying a total of 20 894 differentially expressed genes. Weighted gene co-expression network analysis and time-course difference analysis were performed on the differentially expressed genes, followed by joint analysis. Six key submodules conforming to specific temporal developmental patterns were selected, identifying a total of 2 395 genes. Gene Ontology enrichment analysis and protein network interaction analysis were conducted on genes within each submodule. Thirty hub genes related to the growth and development process of M. coruscus were identified, such as Fen1, Ndufab1b, Ndufs8a, Pcan, Rnaseh2a; Cdh1, Cacng4b, Cav1, Blm, Ryr1a; Mars1, Cdc42, Aasdh, Apoba, Cav1; Kif11, Cdc20, Ubc, Kif23, Cdc6; Ubc, Rps16, Rpl23, Rpsa, Rps27a; Cdc20, Setd2, Ssrp1a, Cav1, Rab8a. They playing major regulatory roles in larval development, including regulation of DNA replication and cell division processes, mitochondrial and ribosomal functions, and protein synthesis processes. This study explores the molecular mechanisms underlying the regulation of M. coruscus larval development at the transcriptome level, providing important theoretical guidance for studying functional genes in M. coruscus and subsequent molecular breeding practices aimed at cultivating new varieties with superior phenotypic traits.
Mytilus coruscus is renowned for its delicious taste and rich nutritional content, making it one of the significant economic shellfish along the coast of China. The critical period for M. coruscus seedling cultivation lies in its larval metamorphosis stage. However, the larval development of M. coruscus is a dynamic and complex process, involving the participation of numerous genes and various intricate biological processes. In this study, we based on high-throughput transcriptome sequencing technology, conducted transcriptome sequencing on larval samples of M. coruscus at five key developmental stages (Trocophore, D-veliger, Umbo, Pediveliger, and Post-larvae), identifying a total of 20 894 differentially expressed genes. Weighted gene co-expression network analysis and time-course difference analysis were performed on the differentially expressed genes, followed by joint analysis. Six key submodules conforming to specific temporal developmental patterns were selected, identifying a total of 2 395 genes. Gene Ontology enrichment analysis and protein network interaction analysis were conducted on genes within each submodule. Thirty hub genes related to the growth and development process of M. coruscus were identified, such as Fen1, Ndufab1b, Ndufs8a, Pcan, Rnaseh2a; Cdh1, Cacng4b, Cav1, Blm, Ryr1a; Mars1, Cdc42, Aasdh, Apoba, Cav1; Kif11, Cdc20, Ubc, Kif23, Cdc6; Ubc, Rps16, Rpl23, Rpsa, Rps27a; Cdc20, Setd2, Ssrp1a, Cav1, Rab8a. They playing major regulatory roles in larval development, including regulation of DNA replication and cell division processes, mitochondrial and ribosomal functions, and protein synthesis processes. This study explores the molecular mechanisms underlying the regulation of M. coruscus larval development at the transcriptome level, providing important theoretical guidance for studying functional genes in M. coruscus and subsequent molecular breeding practices aimed at cultivating new varieties with superior phenotypic traits.
, Available online , doi: 10.12284/hyxb2025070
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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 chlorophylla concentration (Chla) 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-Chla 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 chlorophylla concentration (Chla) 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-Chla 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.
, Available online , doi: 10.12284/hyxb2025080
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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 , doi: 10.12284/hyxb2025068
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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.
, Available online , doi: 10.12284/hyxb2025082
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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)Tg/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 Changjiang 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)Tg/a, and the Yellow Sea carbon sinks are relatively small, (−2.1±0.9)Tg/a. The smallest carbon source appeared in the Bohai Sea is (+0.3±0.1)Tg/a, while the largest carbon source intensity appeared in the South China Sea is (+2.0±0.9)Tg/a. According to seasonal change, the carbon sink intensity in winter is the highest in the China margin seas, with (−45.7±19.7)Tg/a, and weaker in spring, at (−16.9±7.3)Tg/a. In summer and autumn, China's marginal seas as a whole are carbon sources, with an average of (+11.9±5.1)Tg/a and (+9.9±4.3)Tg/a respectively. The average uncertainty of carbon source sink strength in China marginal seas is ±43.0% (±4.4 Tg/a) 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\begin{document}$P_{\mathrm{CO}_2} $\end{document} ![]()
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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)Tg/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 Changjiang 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)Tg/a, and the Yellow Sea carbon sinks are relatively small, (−2.1±0.9)Tg/a. The smallest carbon source appeared in the Bohai Sea is (+0.3±0.1)Tg/a, while the largest carbon source intensity appeared in the South China Sea is (+2.0±0.9)Tg/a. According to seasonal change, the carbon sink intensity in winter is the highest in the China margin seas, with (−45.7±19.7)Tg/a, and weaker in spring, at (−16.9±7.3)Tg/a. In summer and autumn, China's marginal seas as a whole are carbon sources, with an average of (+11.9±5.1)Tg/a and (+9.9±4.3)Tg/a respectively. The average uncertainty of carbon source sink strength in China marginal seas is ±43.0% (±4.4 Tg/a) 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
, Available online , doi: 10.12284/hyxb2025076
Abstract:
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.
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Abstract:
The Zhaiying carbonate-type Mn deposit belongs to the black shale hosted marine manganese(Mn)-bearing formations within the Datangpo Formation in the Nanhua Rift Basin in South China. Unlike other Mn deposits of the Datangpo Formation, parts of the Mn ores in the Zhaiying deposit bear unique bubble structures. To elucidate the metallogenic mechanism of the Zhaiying marine Mn-bearing formation, in this study, petrographic and whole-rock geochemical analyses, including measurements of major and trace elements, organic carbon isotopes, and carbonate carbon stable isotopes, were conducted using the bubble and massive Mn ores as well as host rocks (black shales). The main results are as follows: 1) The PAAS-normalized rare-earth element pattern of the Zhaiying Mn ores exhibits a “hat-shaped” plot. The Mn ores exhibit obvious positive Ce anomalies and are depleted in U and V, implying that the primary depositional environment of the Mn ores was oxidative. Primary Mn oxidizing precipitation has a mechanism similar to marine hydrogenous Mn–Fe nodules and crusts. However, the obvious absence of Ce anomalies and enrichment of pyrites in the host rocks indicate an anoxic depositional environment. 2) The Mn ores are enriched in light δ13Ccarb (−8.53‰ to −10.60‰, averaging at −9.45‰), similar to those belonging to major carbonate-type Mn deposits during geological time. This indicates that primary Mn oxides, as electron acceptors, oxidized organic matter to provide HCO3− for Mn carbonate formation. Moreover, the Zhaiying Mn ores have more negative δ13Ccarb values than other Mn deposits (δ13Ccarb: −8‰ to −6‰) of the Datangpo Formation owing to the greater contribution of carbon from organic matter. 3) The Mn ores have positive Eu anomalies and minor amounts of terrigenous detrital elements (Al, Ti), indicating that the Mn source was hydrothermal. In summary, the results show that the Zhaiying Mn deposit has deposition and mineralizing processes similar to other Mn deposits of the Datangpo Formation in the Nanhua Rift Basin.
The Zhaiying carbonate-type Mn deposit belongs to the black shale hosted marine manganese(Mn)-bearing formations within the Datangpo Formation in the Nanhua Rift Basin in South China. Unlike other Mn deposits of the Datangpo Formation, parts of the Mn ores in the Zhaiying deposit bear unique bubble structures. To elucidate the metallogenic mechanism of the Zhaiying marine Mn-bearing formation, in this study, petrographic and whole-rock geochemical analyses, including measurements of major and trace elements, organic carbon isotopes, and carbonate carbon stable isotopes, were conducted using the bubble and massive Mn ores as well as host rocks (black shales). The main results are as follows: 1) The PAAS-normalized rare-earth element pattern of the Zhaiying Mn ores exhibits a “hat-shaped” plot. The Mn ores exhibit obvious positive Ce anomalies and are depleted in U and V, implying that the primary depositional environment of the Mn ores was oxidative. Primary Mn oxidizing precipitation has a mechanism similar to marine hydrogenous Mn–Fe nodules and crusts. However, the obvious absence of Ce anomalies and enrichment of pyrites in the host rocks indicate an anoxic depositional environment. 2) The Mn ores are enriched in light δ13Ccarb (−8.53‰ to −10.60‰, averaging at −9.45‰), similar to those belonging to major carbonate-type Mn deposits during geological time. This indicates that primary Mn oxides, as electron acceptors, oxidized organic matter to provide HCO3− for Mn carbonate formation. Moreover, the Zhaiying Mn ores have more negative δ13Ccarb values than other Mn deposits (δ13Ccarb: −8‰ to −6‰) of the Datangpo Formation owing to the greater contribution of carbon from organic matter. 3) The Mn ores have positive Eu anomalies and minor amounts of terrigenous detrital elements (Al, Ti), indicating that the Mn source was hydrothermal. In summary, the results show that the Zhaiying Mn deposit has deposition and mineralizing processes similar to other Mn deposits of the Datangpo Formation in the Nanhua Rift Basin.
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Abstract:
The concentration of dissolved carbon dioxide in seawater affects global climate change, the growth of marine organisms and controls the formation of submarine carbonates, it is one of the most important indices in the marine environment and mineral resource survey. It has important academic value for the exploration of seabed minerals, monitoring of marine environment, the study of carbon cycle in seabed sediments and even the global carbon cycle. Titration and Henrys are used to determine the concentration of dissolved carbon dioxide in seawater. The Henrys is more suitable for seawater, especially for a great deal of seawater samples collected from the same sea area on board ships, the results are mainly based on the theoretical Henry's constant of carbon dioxide in seawater, in fact, the Henry’s Law Constants of carbon dioxide in different seawater are different. In order to achieve higher measurement accuracy and precision, the Henry’s Law Constants of carbon dioxide in seawater have to be determined first. An experimental plan is designed and D-value of Multi Balance Systems is put forward in this article, which is used to determine the Henry’s Law Constants of carbon dioxide in seawater. D-value of Multi Balance Systems is based on the principle of mass conservation and the dissolution behavior of carbon dioxide in seawater. In D-value of Multi Balance Systems, multiple gas-liquid balance systems with different masses and volumes are constructed in advance, then the Henry’s Law Constant of carbon dioxide is derived on the basis of the different mass of carbon dioxide between the balance systems. The Henry's values of carbon dioxide in 24 stratified seawater samples from the South China Sea's Shenhu Sea are determined by D-value of Multi Balance Systems. At last the scientificalness and feasibility of D-value of Multi Balance Systems are proved by multiple system conversion coincidence experiments.
The concentration of dissolved carbon dioxide in seawater affects global climate change, the growth of marine organisms and controls the formation of submarine carbonates, it is one of the most important indices in the marine environment and mineral resource survey. It has important academic value for the exploration of seabed minerals, monitoring of marine environment, the study of carbon cycle in seabed sediments and even the global carbon cycle. Titration and Henrys are used to determine the concentration of dissolved carbon dioxide in seawater. The Henrys is more suitable for seawater, especially for a great deal of seawater samples collected from the same sea area on board ships, the results are mainly based on the theoretical Henry's constant of carbon dioxide in seawater, in fact, the Henry’s Law Constants of carbon dioxide in different seawater are different. In order to achieve higher measurement accuracy and precision, the Henry’s Law Constants of carbon dioxide in seawater have to be determined first. An experimental plan is designed and D-value of Multi Balance Systems is put forward in this article, which is used to determine the Henry’s Law Constants of carbon dioxide in seawater. D-value of Multi Balance Systems is based on the principle of mass conservation and the dissolution behavior of carbon dioxide in seawater. In D-value of Multi Balance Systems, multiple gas-liquid balance systems with different masses and volumes are constructed in advance, then the Henry’s Law Constant of carbon dioxide is derived on the basis of the different mass of carbon dioxide between the balance systems. The Henry's values of carbon dioxide in 24 stratified seawater samples from the South China Sea's Shenhu Sea are determined by D-value of Multi Balance Systems. At last the scientificalness and feasibility of D-value of Multi Balance Systems are proved by multiple system conversion coincidence experiments.
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Stable carbon (δ13C) and nitrogen (δ15N) isotope compositions are powerful tools for elucidating fish physiology, trophic interactions, and origin. However, pretreatment methods can substantially influence isotopic results, and the underlying mechanisms remain poorly understood. This study investigates the effects of lipid removal from muscle and acid leaching of scales on the δ13C and δ15N values of large yellow croaker (Larimichthys crocea), a major mariculture species in China. We found that lipid extraction significantly increased muscle δ13C, while acid leaching decreased scale δ13C. An isotope mixing model effectively explained these δ13C variations. Conversely, both pretreatments increased δ15N, suggesting potential losses of specific nitrogen isotope signals. Utilizing a dynamic equilibrium model, we established a theoretical relationship between carbon and nitrogen isotopes in muscle and scales, validating scales as a muscle proxy for nitrogen isotope analysis. This research provides critical baseline data for understanding stable isotope heterogeneity in large yellow croaker, contributes to our understanding of inter-tissue metabolic dynamics, and supports the application of non-lethal sampling in fish stable isotope studies.
Stable carbon (δ13C) and nitrogen (δ15N) isotope compositions are powerful tools for elucidating fish physiology, trophic interactions, and origin. However, pretreatment methods can substantially influence isotopic results, and the underlying mechanisms remain poorly understood. This study investigates the effects of lipid removal from muscle and acid leaching of scales on the δ13C and δ15N values of large yellow croaker (Larimichthys crocea), a major mariculture species in China. We found that lipid extraction significantly increased muscle δ13C, while acid leaching decreased scale δ13C. An isotope mixing model effectively explained these δ13C variations. Conversely, both pretreatments increased δ15N, suggesting potential losses of specific nitrogen isotope signals. Utilizing a dynamic equilibrium model, we established a theoretical relationship between carbon and nitrogen isotopes in muscle and scales, validating scales as a muscle proxy for nitrogen isotope analysis. This research provides critical baseline data for understanding stable isotope heterogeneity in large yellow croaker, contributes to our understanding of inter-tissue metabolic dynamics, and supports the application of non-lethal sampling in fish stable isotope studies.
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Satellite altimetry data provides large-scale, long-term stable ocean flow field information, but its low resolution may affect the accuracy of Lagrangian fluid particle trajectories calculated from it. In this study, a comparative approach using buoy trajectories and chlorophyll structure evolution was employed to systematically assess the reliability of Lagrangian fluid particle trajectories derived from altimetry data.The results indicate that this method effectively characterizes mesoscale oceanic motions, with fluid particle trajectories closely matching the overall trends of actual buoy trajectories, particularly demonstrating strong tracking capability in rotational motion patterns. However, the sensitivity of these trajectories to mesoscale and sub-mesoscale motions is relatively low, with slower movement speeds making it difficult to accurately capture short-period perturbations.Further analysis reveals that fluid particle trajectories can reliably track the evolution of chlorophyll structures over a 30-day period, suggesting their applicability in mesoscale oceanic studies. This research provides a scientific basis for the application of altimetry data in Lagrangian analysis and offers valuable insights for the study of ocean circulation and ecological processes.
Satellite altimetry data provides large-scale, long-term stable ocean flow field information, but its low resolution may affect the accuracy of Lagrangian fluid particle trajectories calculated from it. In this study, a comparative approach using buoy trajectories and chlorophyll structure evolution was employed to systematically assess the reliability of Lagrangian fluid particle trajectories derived from altimetry data.The results indicate that this method effectively characterizes mesoscale oceanic motions, with fluid particle trajectories closely matching the overall trends of actual buoy trajectories, particularly demonstrating strong tracking capability in rotational motion patterns. However, the sensitivity of these trajectories to mesoscale and sub-mesoscale motions is relatively low, with slower movement speeds making it difficult to accurately capture short-period perturbations.Further analysis reveals that fluid particle trajectories can reliably track the evolution of chlorophyll structures over a 30-day period, suggesting their applicability in mesoscale oceanic studies. This research provides a scientific basis for the application of altimetry data in Lagrangian analysis and offers valuable insights for the study of ocean circulation and ecological processes.
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For the past two thousand years, the southern bank of the Yangtze River estuary has basically shown an evolutionary trend of "Shoal extension", with a rate of about 1 km of siltation and development towards the sea every 40 years. It is the most important land growth area and tidal wetland resource in Shanghai, and the research significance is significant. This paper studies the evolution characteristics of Nanhui Shoal in the past 60 years based on indicators such as scouring and silting characteristics, isobath changes and mudflat migration rate from 1958 to 2019, and discusses its growth mode, driving factors and development trend through space-time comparison. The results showed that: (1) From 1958 to 2019, the Nanhuibian Shoal exhibited four stages of gradual siltation, rapid siltation, near siltation and far erosion, and comprehensive erosion. During this stage, the fastest siltation and erosion rates were 460 m/a and 270 m/a, respectively. (2) Human activities have become the main controlling factors affecting the evolution of the Nanhui Shoal at the mouth of the Yangtze River. Among them, variable factors such as watershed dam construction, Yangtze River estuary bifurcation control engineering, Shoal reclamation and land reclamation, and channel dredging and sand mining have greatly affected the evolution of the Nanhui Shoal. The correlation between Shoal reclamation and terrain evolution is strong, with a correlation coefficient of 0.73. (3) With the strict control of land reclamation by the government and Shanghai, the Nanhui Beach will gradually reach a new balance of erosion and deposition in the future. It is recommended to study the protection and management measures of estuarine tidal wetlands as soon as possible to cope with possible coastal disasters in the future.
For the past two thousand years, the southern bank of the Yangtze River estuary has basically shown an evolutionary trend of "Shoal extension", with a rate of about 1 km of siltation and development towards the sea every 40 years. It is the most important land growth area and tidal wetland resource in Shanghai, and the research significance is significant. This paper studies the evolution characteristics of Nanhui Shoal in the past 60 years based on indicators such as scouring and silting characteristics, isobath changes and mudflat migration rate from 1958 to 2019, and discusses its growth mode, driving factors and development trend through space-time comparison. The results showed that: (1) From 1958 to 2019, the Nanhuibian Shoal exhibited four stages of gradual siltation, rapid siltation, near siltation and far erosion, and comprehensive erosion. During this stage, the fastest siltation and erosion rates were 460 m/a and 270 m/a, respectively. (2) Human activities have become the main controlling factors affecting the evolution of the Nanhui Shoal at the mouth of the Yangtze River. Among them, variable factors such as watershed dam construction, Yangtze River estuary bifurcation control engineering, Shoal reclamation and land reclamation, and channel dredging and sand mining have greatly affected the evolution of the Nanhui Shoal. The correlation between Shoal reclamation and terrain evolution is strong, with a correlation coefficient of 0.73. (3) With the strict control of land reclamation by the government and Shanghai, the Nanhui Beach will gradually reach a new balance of erosion and deposition in the future. It is recommended to study the protection and management measures of estuarine tidal wetlands as soon as possible to cope with possible coastal disasters in the future.
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A series of seawater culture experiments were conducted to simulate the degradation of Ulva prolfiera in coastal area under the influence of exogenous degradation microbial consortia The degradation mechanism of Ulva prolifera in seawater under the influence of the exogenous degradation microbial consortia was investigated by tracking the time-dependent changes of lipid biomarkers in culture system. The results showed that for most of the fatty acids (14:0, i-15:0 + a-15:0, 16:0, 16:1ω7, 17:0, 18:0, 18:1ω7, 18:1ω9, 18:3, 18:4, 20:0, 22:0) and neutral lipids of Ulva Prolifera in different forms, their contents presented trends of first rapid decline and followed by a slow decline or maintain stability in the culture system with and without exogenous microbial consortia. Under the influence of exogenous microbial consortia, the degradation efficiency of fatty acid was generally increased by 10%−20%, while that of neutral lipids increased by 15−25%. The multi-G model was applied to fit the degradation processes of several fatty acids and neutral lipids, the results showed that the lipids could be divided into fast and slow degradation fractions in the culture system, and their degradation rates were improved in different degrees, with the range of 20% to 30% with the addition of the exogenous microbial consortia. Under the influence of the exogenous microbial consortia, there was no significant difference in the degradation efficiency and rates of different fatty acids in Ulva prolifera. In seawater, the degradation efficiency and rates of lipids in bound forms were significantly higher than that of their free forms, indicating that the existence forms of lipids of Ulva prolifera had significant effect on their degradation processes. The addition of exogenous degradation microbial consortia increased the degradation rate constants of the slow degradation fractions of the lipids in Ulva Prolifera, thereby promoted its overall degradation .
A series of seawater culture experiments were conducted to simulate the degradation of Ulva prolfiera in coastal area under the influence of exogenous degradation microbial consortia The degradation mechanism of Ulva prolifera in seawater under the influence of the exogenous degradation microbial consortia was investigated by tracking the time-dependent changes of lipid biomarkers in culture system. The results showed that for most of the fatty acids (14:0, i-15:0 + a-15:0, 16:0, 16:1ω7, 17:0, 18:0, 18:1ω7, 18:1ω9, 18:3, 18:4, 20:0, 22:0) and neutral lipids of Ulva Prolifera in different forms, their contents presented trends of first rapid decline and followed by a slow decline or maintain stability in the culture system with and without exogenous microbial consortia. Under the influence of exogenous microbial consortia, the degradation efficiency of fatty acid was generally increased by 10%−20%, while that of neutral lipids increased by 15−25%. The multi-G model was applied to fit the degradation processes of several fatty acids and neutral lipids, the results showed that the lipids could be divided into fast and slow degradation fractions in the culture system, and their degradation rates were improved in different degrees, with the range of 20% to 30% with the addition of the exogenous microbial consortia. Under the influence of the exogenous microbial consortia, there was no significant difference in the degradation efficiency and rates of different fatty acids in Ulva prolifera. In seawater, the degradation efficiency and rates of lipids in bound forms were significantly higher than that of their free forms, indicating that the existence forms of lipids of Ulva prolifera had significant effect on their degradation processes. The addition of exogenous degradation microbial consortia increased the degradation rate constants of the slow degradation fractions of the lipids in Ulva Prolifera, thereby promoted its overall degradation .
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The relationship between the marine biological carbon pump(BCP) and paleoclimate is a central scientific issue in carbon cycle research. This study utilizes the ecological characteristics implied by total organic carbon (TOC) and key lipid compounds in Ross Sea sediments, specifically molecular biomarkers that can influence the composition of the seabed carbon reservoir and the efficiency of the marine BCP (including the biological pump BP and the microbial carbon pump MCP), tracing the evolution of the ancient marine biological carbon pump (with a focus on BP and MCP) since the Last Glacial Maximum (27ka BP～0.6ka BP) and its connection to significant geological events. The research findings indicate: (1) the relatively high TOC and low C/N ratios in surface sediments of the Ross Sea, along with characteristics such as normal alkane chromatographic peak shapes, dominant carbon, molecular composition features with low to high carbon number ratios (L/H) and(nC21+nC22)/(nC28+nC29)ratios, low n-alkanes(nC15+nC17+nC19), mid-chain alkanes(nC21+nC23+nC25), high-chain alkanes (nC27+nC29+nC31), bacterial (BrGDGT), and lower terrigenous input index (BIT), collectively indicate a predominance of marine-derived organic matter contributing to the seabed through the effects of the marine BP and MCP, facilitating long-term carbon storage. The Pr/Ph ratio combined with Ph/nC18 and Ph/nC17 ratios suggest that surface sediments represent a reducing to strongly reducing anoxic environment conducive to organic carbon sequestration on the seafloor, closely linked to sea ice melt. (2) By employing a low-temperature correction formula\begin{document}$ {\mathrm{T}\mathrm{E}\mathrm{X}}_{86}^{\mathrm{L}} $\end{document} ![]()
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The relationship between the marine biological carbon pump(BCP) and paleoclimate is a central scientific issue in carbon cycle research. This study utilizes the ecological characteristics implied by total organic carbon (TOC) and key lipid compounds in Ross Sea sediments, specifically molecular biomarkers that can influence the composition of the seabed carbon reservoir and the efficiency of the marine BCP (including the biological pump BP and the microbial carbon pump MCP), tracing the evolution of the ancient marine biological carbon pump (with a focus on BP and MCP) since the Last Glacial Maximum (27ka BP～0.6ka BP) and its connection to significant geological events. The research findings indicate: (1) the relatively high TOC and low C/N ratios in surface sediments of the Ross Sea, along with characteristics such as normal alkane chromatographic peak shapes, dominant carbon, molecular composition features with low to high carbon number ratios (L/H) and(nC21+nC22)/(nC28+nC29)ratios, low n-alkanes(nC15+nC17+nC19), mid-chain alkanes(nC21+nC23+nC25), high-chain alkanes (nC27+nC29+nC31), bacterial (BrGDGT), and lower terrigenous input index (BIT), collectively indicate a predominance of marine-derived organic matter contributing to the seabed through the effects of the marine BP and MCP, facilitating long-term carbon storage. The Pr/Ph ratio combined with Ph/nC18 and Ph/nC17 ratios suggest that surface sediments represent a reducing to strongly reducing anoxic environment conducive to organic carbon sequestration on the seafloor, closely linked to sea ice melt. (2) By employing a low-temperature correction formula
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A self-developed separation and enrichment device was employed to investigate the pretreatment method for isolating and concentrating 15 trace elements (Al, Sc, V, Fe, Co, Ni, Cu, Zn, Ga, Cd, Nd, Pb, Bi, Th, and U) from seawater using Toyopearl AF-Chelate 650M chelating resin. Key parameters including sample loading pH, washing solution composition and volume, and eluent type and volume were optimized. High-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was used for accurate determination. The results demonstrated that when 8.92 mL of seawater sample was mixed with acetic acid-ammonium acetate buffer solution at a 1:1 ratio (loading pH = 5.25) and loaded onto the resin, matrix impurities could be effectively removed by washing with 8.0 mL of Milli-Q water. After matrix removal, the adsorbed trace elements were quantitatively recovered by elution with 2.25 mL of 0.8 mol/L HNO3. Rh was added as an internal standard to the eluent prior to HR-ICP-MS analysis. Method blanks ranged from 0.27 pg (Cd) to 52.5 pg (Al), with method detection limits between 0.06 ng/L (Cd) and 1.67 ng/L (Zn). Excellent linearity (R2 > 0.999) was achieved across the concentration range of 0.01−50.0 μg/L. The method was validated using certified reference materials GBW(E)080040 and CASS-6. For GBW(E)080040, measured concentrations of Cu, Zn, Cd and Pb agreed well with certified values (relative error < 4.1%, RSD < 4.1%), with spike recoveries of 92.6%−107% for all 15 elements. Results for CASS-6 also showed good agreement with certified and reported values (RSD < 6.4%). This method features simple and rapid pretreatment, efficient matrix removal, low detection limits, high accuracy and good precision, making it suitable for simultaneous determination of trace elements in various water matrices including natural freshwater, drinking water, estuarine and marine waters.
A self-developed separation and enrichment device was employed to investigate the pretreatment method for isolating and concentrating 15 trace elements (Al, Sc, V, Fe, Co, Ni, Cu, Zn, Ga, Cd, Nd, Pb, Bi, Th, and U) from seawater using Toyopearl AF-Chelate 650M chelating resin. Key parameters including sample loading pH, washing solution composition and volume, and eluent type and volume were optimized. High-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was used for accurate determination. The results demonstrated that when 8.92 mL of seawater sample was mixed with acetic acid-ammonium acetate buffer solution at a 1:1 ratio (loading pH = 5.25) and loaded onto the resin, matrix impurities could be effectively removed by washing with 8.0 mL of Milli-Q water. After matrix removal, the adsorbed trace elements were quantitatively recovered by elution with 2.25 mL of 0.8 mol/L HNO3. Rh was added as an internal standard to the eluent prior to HR-ICP-MS analysis. Method blanks ranged from 0.27 pg (Cd) to 52.5 pg (Al), with method detection limits between 0.06 ng/L (Cd) and 1.67 ng/L (Zn). Excellent linearity (R2 > 0.999) was achieved across the concentration range of 0.01−50.0 μg/L. The method was validated using certified reference materials GBW(E)080040 and CASS-6. For GBW(E)080040, measured concentrations of Cu, Zn, Cd and Pb agreed well with certified values (relative error < 4.1%, RSD < 4.1%), with spike recoveries of 92.6%−107% for all 15 elements. Results for CASS-6 also showed good agreement with certified and reported values (RSD < 6.4%). This method features simple and rapid pretreatment, efficient matrix removal, low detection limits, high accuracy and good precision, making it suitable for simultaneous determination of trace elements in various water matrices including natural freshwater, drinking water, estuarine and marine waters.
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Abstract:
Calcium carbonate (CaCO3), as a major component of shells, interacts with the organic matter framework to form shells and provide protection for mollusks. Ca2+ is an important component of CaCO3, and its acquisition, transport, and precipitation processes can significantly affect calcium carbonate deposition in mollusks. However, there is still a lack of clarity regarding the process of calcium carbonate deposition and mechanism of related genes in forming shells. Calmodulin (CaM) is a protein widely found in eukaryotic cells and specifically binds to Ca2+, which is mainly involved in a variety of physiological processes such as cellular signal transduction, regulation of target enzyme activities and regulation of Ca2+ homeostasis. In order to investigate the relationship between CaM gene and calcium carbonate deposition in shells, we performed molecular identification and expression characterization of CaM gene in Sinonovacula constricta (ScCaM), and investigated the Ca2+-binding activity of the recombinant protein ScCaM and its role in calcium carbonate deposition. The results showed that the ScCaM gene encoded a total of 149 amino acids and contained four consecutive EF-hand structural domains. ScCaM was expressed in all tissues, with the expression level in gill and mantle tissues being significantly higher than in foot, siphon, adductor muscle and hepatopancreas tissues (P < 0.05). Furthermore, the content of calcium carbonate in shells was positively proportional to their shell weight. Meanwhile, individuals with larger shell weights had higher expression levels of ScCaM. ScCaM recombinant protein had calcium ion binding activity, which can accelerate the rate of calcium carbonate deposition, and the promotion effect showed an obvious protein concentration dependence. The results showed that ScCaM gene/protein expression was closely related to shell calcium carbonate content: elevated ScCaM gene/protein expression could enhance Ca2+ transport efficiency, promote shell calcium carbonate deposition, and thus increase shell weight. This study preliminarily investigated the role of ScCaM gene in shell calcium carbonate deposition, and provided a theoretical basis for analyzing the molecular mechanism of shell formation in S. constricta.
Calcium carbonate (CaCO3), as a major component of shells, interacts with the organic matter framework to form shells and provide protection for mollusks. Ca2+ is an important component of CaCO3, and its acquisition, transport, and precipitation processes can significantly affect calcium carbonate deposition in mollusks. However, there is still a lack of clarity regarding the process of calcium carbonate deposition and mechanism of related genes in forming shells. Calmodulin (CaM) is a protein widely found in eukaryotic cells and specifically binds to Ca2+, which is mainly involved in a variety of physiological processes such as cellular signal transduction, regulation of target enzyme activities and regulation of Ca2+ homeostasis. In order to investigate the relationship between CaM gene and calcium carbonate deposition in shells, we performed molecular identification and expression characterization of CaM gene in Sinonovacula constricta (ScCaM), and investigated the Ca2+-binding activity of the recombinant protein ScCaM and its role in calcium carbonate deposition. The results showed that the ScCaM gene encoded a total of 149 amino acids and contained four consecutive EF-hand structural domains. ScCaM was expressed in all tissues, with the expression level in gill and mantle tissues being significantly higher than in foot, siphon, adductor muscle and hepatopancreas tissues (P < 0.05). Furthermore, the content of calcium carbonate in shells was positively proportional to their shell weight. Meanwhile, individuals with larger shell weights had higher expression levels of ScCaM. ScCaM recombinant protein had calcium ion binding activity, which can accelerate the rate of calcium carbonate deposition, and the promotion effect showed an obvious protein concentration dependence. The results showed that ScCaM gene/protein expression was closely related to shell calcium carbonate content: elevated ScCaM gene/protein expression could enhance Ca2+ transport efficiency, promote shell calcium carbonate deposition, and thus increase shell weight. This study preliminarily investigated the role of ScCaM gene in shell calcium carbonate deposition, and provided a theoretical basis for analyzing the molecular mechanism of shell formation in S. constricta.
, Available online , doi: 10.12284/hyxb2025074
Abstract:
Volatile organic compounds (VOCs) in phytoplankton refer to low-molecular-weight compounds with high vapor pressure that are either absorbed from the aquatic environment or metabolized within the organisms. This study aimed to reveal the composition characteristics and seasonal variation patterns of water quality parameters and volatile organic compounds (VOCs) in phytoplankton from different large yellow croaker aquaculture net cages. Three sampling sites were selected, namely Dongtou (DT), Nanji (NJ), and Ningde (ND), and phytoplankton samples were collected from the net cages during the summer and autumn. The composition of VOCs was analyzed using automated headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), and its correlation with water quality parameters was examined. The results showed that the VOCs in the net cage phytoplankton of large yellow croaker were mainly composed of aromatics, hydrocarbons, esters, and ketones. The total VOC content and types were significantly higher in winter than in summer, with higher levels in DT and NJ compared to ND. In winter, the levels of naphthalene, and in summer, 2,4-di-tert-butylphenol and Z-2-dodecenol were significantly higher in ND than in DT and NJ, indicating the stronger influence of human activities and potential ecological risks in ND. In summer, the levels of dihydro-2-methyl-3(2H)-furanone, 2-hexanal, and linalool were higher in the phytoplankton of the DT and NJ net cages than in ND, while no detectable levels were found in the net cages of all three aquaculture zones in winter. These aromatic VOCs may accumulate in the muscle tissue of large yellow croaker through the food chain, enhancing its flavor quality. Water quality parameters such as total nitrogen, active phosphate, total phosphorus, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, pH, and dissolved oxygen exhibited significant differences across seasons and regions, and were closely related to the production and distribution of VOCs. The findings provide new insights into the understanding of marine net cage water quality health and offer important references for the development of VOCs as environmental monitoring biomarkers and optimizing the quality of large yellow croaker aquaculture.
Volatile organic compounds (VOCs) in phytoplankton refer to low-molecular-weight compounds with high vapor pressure that are either absorbed from the aquatic environment or metabolized within the organisms. This study aimed to reveal the composition characteristics and seasonal variation patterns of water quality parameters and volatile organic compounds (VOCs) in phytoplankton from different large yellow croaker aquaculture net cages. Three sampling sites were selected, namely Dongtou (DT), Nanji (NJ), and Ningde (ND), and phytoplankton samples were collected from the net cages during the summer and autumn. The composition of VOCs was analyzed using automated headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), and its correlation with water quality parameters was examined. The results showed that the VOCs in the net cage phytoplankton of large yellow croaker were mainly composed of aromatics, hydrocarbons, esters, and ketones. The total VOC content and types were significantly higher in winter than in summer, with higher levels in DT and NJ compared to ND. In winter, the levels of naphthalene, and in summer, 2,4-di-tert-butylphenol and Z-2-dodecenol were significantly higher in ND than in DT and NJ, indicating the stronger influence of human activities and potential ecological risks in ND. In summer, the levels of dihydro-2-methyl-3(2H)-furanone, 2-hexanal, and linalool were higher in the phytoplankton of the DT and NJ net cages than in ND, while no detectable levels were found in the net cages of all three aquaculture zones in winter. These aromatic VOCs may accumulate in the muscle tissue of large yellow croaker through the food chain, enhancing its flavor quality. Water quality parameters such as total nitrogen, active phosphate, total phosphorus, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, pH, and dissolved oxygen exhibited significant differences across seasons and regions, and were closely related to the production and distribution of VOCs. The findings provide new insights into the understanding of marine net cage water quality health and offer important references for the development of VOCs as environmental monitoring biomarkers and optimizing the quality of large yellow croaker aquaculture.
, Available online
Abstract:
To address the issue of complex sound speed profile (SSP) structures and significantly large reconstruction errors within mesoscale eddies, this study proposes the PIRF-DEN model by integrating multi-source satellite remote sensing data and Argo profiles with a random forest algorithm and a unified mesoscale eddy structure model. By utilizing sea surface temperature, height anomaly, salinity, density, and other environmental parameters at the sea surface, along with Argo density data as inputs, the model establishes a "surface-to-underwater" sound speed mapping relationship. Additionally, it reconstructs the density field within eddies based on the unified mesoscale eddy structure model and incorporates both surface environmental parameters and reconstructed eddy densities into the mapping relationship to reconstruct the SSP within the eddies. The results demonstrate that the PIRF-DEN model markedly enhances the accuracy of SSP reconstruction, reducing the Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) to0.8324 m/s and 1.3869 m/s, respectively. This represents an 87.3% and 83.7% reduction compared to the traditional sEOF-r method. Furthermore, the sound speed reconstruction accuracy and stability of the PIRF-DEN model surpass those of existing models.
To address the issue of complex sound speed profile (SSP) structures and significantly large reconstruction errors within mesoscale eddies, this study proposes the PIRF-DEN model by integrating multi-source satellite remote sensing data and Argo profiles with a random forest algorithm and a unified mesoscale eddy structure model. By utilizing sea surface temperature, height anomaly, salinity, density, and other environmental parameters at the sea surface, along with Argo density data as inputs, the model establishes a "surface-to-underwater" sound speed mapping relationship. Additionally, it reconstructs the density field within eddies based on the unified mesoscale eddy structure model and incorporates both surface environmental parameters and reconstructed eddy densities into the mapping relationship to reconstruct the SSP within the eddies. The results demonstrate that the PIRF-DEN model markedly enhances the accuracy of SSP reconstruction, reducing the Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) to
, Available online
Abstract:
: Chlorophyll-a (Chl-a) concentration in the ocean is an important indicator of the marine phytoplankton biomass and serves as a direct reflection of marine ecological and environmental changes. Accurate and efficient estimation of Chl-a is essential for oceanographic research. Satellite remote sensing facilitates large-scale, high-frequency monitoring of Chl-a, offering important support for understanding evolution of marine ecosystem. However, due to the complex bio-optical properties, remote sensing retrievals of Chl-a in coastal, turbid waters are often uncertain, requiring the use of extensive in situ observations for validation and optimization. In this study, in situ Chl-a observations from 45 cruises conducted between 2010 and 2023 were integrated with synchronous satellite remote sensing reflectance data to develop a machine learning (ML) model for estimating Chl-a concentrations in the Yellow River Estuary adjacent sea areas. The results demonstrate that, compared to traditional standard algorithms and previous regional models, ML algorithms achieve higher accuracy. Among ML models, the Gaussian Process Regression (GPR) model yielded the best performance (R2 = 0.62, RMSE = 0.21 mg/m3), effectively capturing the spatial temporal Chl-a patterns of this area. The chlorophyll-a (Chl-a) concentration in this sea area demonstrates a spatial pattern of nearshore areas being higher than offshore areas, with seasonal variation showing a distinct single-peak structure characterized by higher values in summer and lower values in winter. From 2003 to 2023, the average Chl-a concentration increased at an annual rate of 0.02 mg/m3. This research advances remote sensing retrieval algorithms for Chl-a concentration in coastal waters, expands the application of ML models, and provides both methodological and data supports for evaluating the marine ecological environment in the Yellow River Estuary and its adjacent areas.
: Chlorophyll-a (Chl-a) concentration in the ocean is an important indicator of the marine phytoplankton biomass and serves as a direct reflection of marine ecological and environmental changes. Accurate and efficient estimation of Chl-a is essential for oceanographic research. Satellite remote sensing facilitates large-scale, high-frequency monitoring of Chl-a, offering important support for understanding evolution of marine ecosystem. However, due to the complex bio-optical properties, remote sensing retrievals of Chl-a in coastal, turbid waters are often uncertain, requiring the use of extensive in situ observations for validation and optimization. In this study, in situ Chl-a observations from 45 cruises conducted between 2010 and 2023 were integrated with synchronous satellite remote sensing reflectance data to develop a machine learning (ML) model for estimating Chl-a concentrations in the Yellow River Estuary adjacent sea areas. The results demonstrate that, compared to traditional standard algorithms and previous regional models, ML algorithms achieve higher accuracy. Among ML models, the Gaussian Process Regression (GPR) model yielded the best performance (R2 = 0.62, RMSE = 0.21 mg/m3), effectively capturing the spatial temporal Chl-a patterns of this area. The chlorophyll-a (Chl-a) concentration in this sea area demonstrates a spatial pattern of nearshore areas being higher than offshore areas, with seasonal variation showing a distinct single-peak structure characterized by higher values in summer and lower values in winter. From 2003 to 2023, the average Chl-a concentration increased at an annual rate of 0.02 mg/m3. This research advances remote sensing retrieval algorithms for Chl-a concentration in coastal waters, expands the application of ML models, and provides both methodological and data supports for evaluating the marine ecological environment in the Yellow River Estuary and its adjacent areas.
, Available online , doi: 10.12284/hyxb2025058
Abstract:
To explore the characteristics and changes of zooplankton community structure in Tieshan Bay area of the Beibu Gulf, the abundance, biomass, species composition, dominant species and their relationship with environmental factors were analyzed based on the investigation conducted during April 2018 (spring), July 2018 (summer), October 2018 (autumn) and July 2022 (summer). A total of 162 species (classes) of zooplankton were identified. In 2018, the abundance and biomass of zooplankton were higher in summer [(274.58 ± 221.15) ind./m3, (152.09 ± 142.97) mg/m3], higher than in autumn [(215.72 ± 114.81) ind./m3, (87.65 ± 46.70) mg/m3], and higher than in spring [(193.75 ± 185.81) ind./m3, (60.95 ± 47.96) mg/m3]. There were 15 dominant species. The dominant species had obvious seasonal variation. In spring, the dominant species were offshore species such as Muggiaea atlantica and Dolioletta gegenbauri. Pleurobrachia globosa was dominant species only in summer. Nearshore warm-water species such as Acartia pacifica and Temora turbinata dominated in autumn. Compared with the summer of 2018, the temperature and chlorophyll a mass concentration in the summer of 2022 increased, which increased the proportion of jellyfish in the zooplankton community structure. The seasonal and interannual differences of zooplankton community structure in Tieshan Bay were mainly affected by temperature, salinity and Chl a concentration. The study also shows that the community structure of zooplankton tends to be miniaturized and the community stability is poor.
To explore the characteristics and changes of zooplankton community structure in Tieshan Bay area of the Beibu Gulf, the abundance, biomass, species composition, dominant species and their relationship with environmental factors were analyzed based on the investigation conducted during April 2018 (spring), July 2018 (summer), October 2018 (autumn) and July 2022 (summer). A total of 162 species (classes) of zooplankton were identified. In 2018, the abundance and biomass of zooplankton were higher in summer [(274.58 ± 221.15) ind./m3, (152.09 ± 142.97) mg/m3], higher than in autumn [(215.72 ± 114.81) ind./m3, (87.65 ± 46.70) mg/m3], and higher than in spring [(193.75 ± 185.81) ind./m3, (60.95 ± 47.96) mg/m3]. There were 15 dominant species. The dominant species had obvious seasonal variation. In spring, the dominant species were offshore species such as Muggiaea atlantica and Dolioletta gegenbauri. Pleurobrachia globosa was dominant species only in summer. Nearshore warm-water species such as Acartia pacifica and Temora turbinata dominated in autumn. Compared with the summer of 2018, the temperature and chlorophyll a mass concentration in the summer of 2022 increased, which increased the proportion of jellyfish in the zooplankton community structure. The seasonal and interannual differences of zooplankton community structure in Tieshan Bay were mainly affected by temperature, salinity and Chl a concentration. The study also shows that the community structure of zooplankton tends to be miniaturized and the community stability is poor.
, Available online , doi: 10.12284/hyxb2025041
Abstract:
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) a, 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) a, 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 , doi: 10.12284/hyxb2025048
Abstract:
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.
, Available online , doi: 10.12284/hyxb2025025
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.
Spatial distribution of Arctic tidal dynamics and analysis of tidal wave propagation characteristics
, Available online , doi: 10.12284/hyxb2025045
Abstract:
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.
, Available online , doi: 10.12284/hyxb2025056
Abstract:
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/(m2·a), 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/(m2·a), 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.
, Available online , doi: 10.12284/hyxb2025016
Abstract:
To investigate the feeding effects of Acanthaster cf. solaris on Pocillopora damicornis and its molecular regulatory mechanisms, this study focused on the typical P. 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 A. cf. solaris. The results showed that the expression of chemical receptor genes in the A. cf. solaris significantly changed during the feeding process on P. 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 P. 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 P. 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 A. cf. solaris. The results showed that the expression of chemical receptor genes in the A. cf. solaris significantly changed during the feeding process on P. 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 P. 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.
, Available online , doi: 10.12284/hyxb2025052
Abstract:
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
, Available online , doi: 10.12284/hyxb2025035
Abstract:
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.
, Available online , doi: 10.12284/hyxb2025033
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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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Abstract:
Sediment oxygen consumption (SOC) is a key parameter for quantifying organic carbon mineralization in sediments, crucial for understanding the marine carbon cycle. The oxygen consumption of sediments in marginal seas account for approximately 60% of global marine sediments. Temperature is a major factor influencing microbial respiration in sediments. However, there is a lack of research on the differences in temperature responses of sediment oxygen consumption across various estuaries and nearshore areas, which may lead to inaccuracies in our understanding of sediment oxygen consumption and mineralization, especially in the context of global warming and rising sea temperatures. This study examined sediment from the Yangtze River Estuary, the Yellow River Estuary, and the Yellow Sea nearshore, measuring sediment oxygen consumption across a temperature range of 2−45 ℃ with 2−3 ℃ increments. Results showed an exponential increase in sediment oxygen consumption with temperature in all three regions. The apparent activation energy (Eaʹ) of sediment oxygen consumption in the Yangtze River Estuary is in the range of 69−77 kJ/mol, and the temperature coefficient (Q10 (15−25℃)) is 2.6−3.0, similar to sediments in the Weser Estuary of Germany. In the Yellow River Estuary and the coastal area of the Yellow Sea, the Eaʹ is 51−58 kJ/mol, and the Q10 (15−25℃) value is 2.0−2.3, comparable to data from shallow sediments in the Canada Bay. The Eaʹ and Q10 (15−25℃) of sediment oxygen consumption in the Yangtze River Estuary are significantly higher than those in the Yellow River Estuary and the Yellow Sea nearshore (AVONA, P<0.01), likely due to higher labile organic carbon content. The range of sediment oxygen consumption Q10 (15−25℃) is 2.5 ± 0.3, basically in line with that of sediment oxygen consumption on a global scale (2.4 ± 0.4), consistent with the range of Q10 being 2−3 for most biological reactions. This study provides critical data on the temperature response and differences in SOC, offering insights into the feedback between carbon mineralization in estuarine and nearshore sediments and global climate change.
Sediment oxygen consumption (SOC) is a key parameter for quantifying organic carbon mineralization in sediments, crucial for understanding the marine carbon cycle. The oxygen consumption of sediments in marginal seas account for approximately 60% of global marine sediments. Temperature is a major factor influencing microbial respiration in sediments. However, there is a lack of research on the differences in temperature responses of sediment oxygen consumption across various estuaries and nearshore areas, which may lead to inaccuracies in our understanding of sediment oxygen consumption and mineralization, especially in the context of global warming and rising sea temperatures. This study examined sediment from the Yangtze River Estuary, the Yellow River Estuary, and the Yellow Sea nearshore, measuring sediment oxygen consumption across a temperature range of 2−45 ℃ with 2−3 ℃ increments. Results showed an exponential increase in sediment oxygen consumption with temperature in all three regions. The apparent activation energy (Eaʹ) of sediment oxygen consumption in the Yangtze River Estuary is in the range of 69−77 kJ/mol, and the temperature coefficient (Q10 (15−25℃)) is 2.6−3.0, similar to sediments in the Weser Estuary of Germany. In the Yellow River Estuary and the coastal area of the Yellow Sea, the Eaʹ is 51−58 kJ/mol, and the Q10 (15−25℃) value is 2.0−2.3, comparable to data from shallow sediments in the Canada Bay. The Eaʹ and Q10 (15−25℃) of sediment oxygen consumption in the Yangtze River Estuary are significantly higher than those in the Yellow River Estuary and the Yellow Sea nearshore (AVONA, P<0.01), likely due to higher labile organic carbon content. The range of sediment oxygen consumption Q10 (15−25℃) is 2.5 ± 0.3, basically in line with that of sediment oxygen consumption on a global scale (2.4 ± 0.4), consistent with the range of Q10 being 2−3 for most biological reactions. This study provides critical data on the temperature response and differences in SOC, offering insights into the feedback between carbon mineralization in estuarine and nearshore sediments and global climate change.
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To study the community characteristics of meiofauna in the mangrove wetland of Beihai, Guangxi, quantitative sampling of meiofauna and environmental factors was conducted in January (winter) and July (summer) of 2021. Three sections with nine stations were set up in the mangrove wetland. The results showed that the average abundance of meiofauna in winter and summer were (2 617.17±973.13) ind./10 cm2 and (1 173.69±535.75) ind./10 cm2. The average abundance of meiofauna in mangrove section was the highest (2 398.23±1 502.71) ind./10 cm², and the section of the bare section is the lowest, which is (1 539.55±731.04) ind./10 cm², and the cultivation section is (1 748.50±469.20) ind./10 cm². The average biomass of meiofauna was (3 686.93±1 096.40) μg dwt/10 cm² in winter and (2 258.18±1 019.48) μg dwt/10 cm² in summer. The average biomass of meiofauna in bare section was the highest, which was (3 650.13±1 188.95) μg dwt/10 cm². The lowest cultivation section was (272.32±531.48) μg dwt/10 cm². The mangrove section is (2 995.21±1 499.03) μg dwt/10 cm². Ten groups of meiofauna were identified in each season and each section. Marine nematodes were the most dominant group. The composition of groups in the bare section was more uniform. The meiofauna community in bare section was the most unique, characterized by its lowest abundance, highest biomass, higher uniformity in group composition and greater difference in overall community structure than the other two sections. This is related to the unique environmental characteristics of bare section, especially the influence of larger sediment particles, higher temperature and lower water content, and the overall environmental condition is the best. According to the evaluation results of N/C ratio, the environmental condition of the study area is generally good.
To study the community characteristics of meiofauna in the mangrove wetland of Beihai, Guangxi, quantitative sampling of meiofauna and environmental factors was conducted in January (winter) and July (summer) of 2021. Three sections with nine stations were set up in the mangrove wetland. The results showed that the average abundance of meiofauna in winter and summer were (2 617.17±973.13) ind./10 cm2 and (1 173.69±535.75) ind./10 cm2. The average abundance of meiofauna in mangrove section was the highest (2 398.23±1 502.71) ind./10 cm², and the section of the bare section is the lowest, which is (1 539.55±731.04) ind./10 cm², and the cultivation section is (1 748.50±469.20) ind./10 cm². The average biomass of meiofauna was (3 686.93±1 096.40) μg dwt/10 cm² in winter and (2 258.18±1 019.48) μg dwt/10 cm² in summer. The average biomass of meiofauna in bare section was the highest, which was (3 650.13±1 188.95) μg dwt/10 cm². The lowest cultivation section was (272.32±531.48) μg dwt/10 cm². The mangrove section is (2 995.21±1 499.03) μg dwt/10 cm². Ten groups of meiofauna were identified in each season and each section. Marine nematodes were the most dominant group. The composition of groups in the bare section was more uniform. The meiofauna community in bare section was the most unique, characterized by its lowest abundance, highest biomass, higher uniformity in group composition and greater difference in overall community structure than the other two sections. This is related to the unique environmental characteristics of bare section, especially the influence of larger sediment particles, higher temperature and lower water content, and the overall environmental condition is the best. According to the evaluation results of N/C ratio, the environmental condition of the study area is generally good.
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Abstract:
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.
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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.
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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.
, 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.
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Abstract:
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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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:
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.
, Available online
Abstract:
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
Abstract:
A near-real-time version of the blended sea surface wind (BSSW) data product from multiple satellites, as well as the data processing method, and data accuracy analysis is introduced in this paper. The BSSW used sea surface winds provided by the virtual satellite constellation composed of HY-2 series satellites, Metop series satellites and DMSP series satellites as input. Error analysis, cross-calibration and 2D-Var processing is applied to blend these winds derived from different platform. With these methods, a near-real-time blended sea surface product with 6 hours interval and a spatial resolution of 25 kilometers is produced and released operationally by National Satellite Ocean Satellite Application Service. Comparing to buoy data, the RMSE is below 1.6 m/s for wind speed and below 19° for wind direction. While comparing to ERA5 data, the RMSE is below 1.2 m/s for wind speed and below 11° for wind direction. The validation results show that the BSSW is consistent with the buoy winds and ERA5 winds, indicating that BSSW can be of great importance to ocean and atmospheric numerical forecast model, marine disaster prevention and reduction, as well as scientific research on ocean.
A near-real-time version of the blended sea surface wind (BSSW) data product from multiple satellites, as well as the data processing method, and data accuracy analysis is introduced in this paper. The BSSW used sea surface winds provided by the virtual satellite constellation composed of HY-2 series satellites, Metop series satellites and DMSP series satellites as input. Error analysis, cross-calibration and 2D-Var processing is applied to blend these winds derived from different platform. With these methods, a near-real-time blended sea surface product with 6 hours interval and a spatial resolution of 25 kilometers is produced and released operationally by National Satellite Ocean Satellite Application Service. Comparing to buoy data, the RMSE is below 1.6 m/s for wind speed and below 19° for wind direction. While comparing to ERA5 data, the RMSE is below 1.2 m/s for wind speed and below 11° for wind direction. The validation results show that the BSSW is consistent with the buoy winds and ERA5 winds, indicating that BSSW can be of great importance to ocean and atmospheric numerical forecast model, marine disaster prevention and reduction, as well as scientific research on ocean.
, Available online , doi: 10.12284/hyxb2025006
Abstract:
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
, Available online
Abstract:
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
, Available online
Abstract:
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
, Available online
Abstract:
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
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