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, Available online ,
doi: 10.12284/hyxb2023040
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Spaceborne synthetic aperture radar (SAR) is able to collect observations under all kinds of weather during day and night. Such measurements have been proven to provide significant data support for the ocean dynamics study. While SAR imaging of ocean waves is a highly nonlinear process, leading the wave signal missing along the azimuth direction. The image cross-spectrum provides a way to help investigate the ocean wave features particularly for their propagation direction. In this study, we extended a recently defined parameter based on SAR image cross-spectrum and analyzed the correlation of different wave scales with the local wind speed. The range peak wavenumber (wavelength) extracted from the range spectral profile is also demonstrated at the global scale based on about 4 million SAR images. It is found that this new spectral parameter could to some extent reflect the coupling between wind and waves. The global pattern of range peak wavenumber also illustrates evident seasonality.
Spaceborne synthetic aperture radar (SAR) is able to collect observations under all kinds of weather during day and night. Such measurements have been proven to provide significant data support for the ocean dynamics study. While SAR imaging of ocean waves is a highly nonlinear process, leading the wave signal missing along the azimuth direction. The image cross-spectrum provides a way to help investigate the ocean wave features particularly for their propagation direction. In this study, we extended a recently defined parameter based on SAR image cross-spectrum and analyzed the correlation of different wave scales with the local wind speed. The range peak wavenumber (wavelength) extracted from the range spectral profile is also demonstrated at the global scale based on about 4 million SAR images. It is found that this new spectral parameter could to some extent reflect the coupling between wind and waves. The global pattern of range peak wavenumber also illustrates evident seasonality.
, Available online ,
doi: 10.12284/hyxb2024004
Abstract:
Natural gas hydrates have received widespread attention due to their enormous resource potential, but previous researches have focused mostly on the passive continental margin in the northern South China Sea, while rarely on the active continental margin in the eastern South China Sea. Based on the analysis of multi-channel seismic profiles in the active continental margin area of the Manila Trench in northeast of the South China Sea, this paper identified typical gas hydrate indicators such as bottom simulating reflector, blanking zone, polarity-reversal, and fluid migration channels, such as reverse fault and mud diapir are identified in this paper. The Orogenic Belt in southwestern Taiwan is an extension of the accretionary wedge of the Manila Trench. The associated gas of mud volcano is mainly CH4 and minorly showing high nitrogen anomaly. The geochemical characteristics of the associated gas show that natural gas in this area is mainly mature hydrocarbon gas of pyrolysis origin, and is mainly the contribution of Neogene thick marine sedimentary source rock. According to the analysis, the cause is that the plate subduction brought deep hydrocarbon into the accretionary wedge and formed a high-pressure environment. The thermally generated hydrocarbon gas migrated upward along mud diapir and reverse fault. During the migration, some natural gas was gradually transformed by decomposition of microorganisms and mixed with in-situ microbial gas. The thermogenic and biogenic methane eventually mixed in the suitable stable zone to form a mixed gas hydrate reservoir dominated by thermogenic and partly biogenic. In addition, with the change of external environment and the continuous activities of subduction movement, the stability of natural gas hydrate is damaged and decomposition leakage occurs, which may cause landslide. In the further exploration and development of natural gas hydrate resources in this area, we must pay attention to the potential geological disaster risk.
Natural gas hydrates have received widespread attention due to their enormous resource potential, but previous researches have focused mostly on the passive continental margin in the northern South China Sea, while rarely on the active continental margin in the eastern South China Sea. Based on the analysis of multi-channel seismic profiles in the active continental margin area of the Manila Trench in northeast of the South China Sea, this paper identified typical gas hydrate indicators such as bottom simulating reflector, blanking zone, polarity-reversal, and fluid migration channels, such as reverse fault and mud diapir are identified in this paper. The Orogenic Belt in southwestern Taiwan is an extension of the accretionary wedge of the Manila Trench. The associated gas of mud volcano is mainly CH4 and minorly showing high nitrogen anomaly. The geochemical characteristics of the associated gas show that natural gas in this area is mainly mature hydrocarbon gas of pyrolysis origin, and is mainly the contribution of Neogene thick marine sedimentary source rock. According to the analysis, the cause is that the plate subduction brought deep hydrocarbon into the accretionary wedge and formed a high-pressure environment. The thermally generated hydrocarbon gas migrated upward along mud diapir and reverse fault. During the migration, some natural gas was gradually transformed by decomposition of microorganisms and mixed with in-situ microbial gas. The thermogenic and biogenic methane eventually mixed in the suitable stable zone to form a mixed gas hydrate reservoir dominated by thermogenic and partly biogenic. In addition, with the change of external environment and the continuous activities of subduction movement, the stability of natural gas hydrate is damaged and decomposition leakage occurs, which may cause landslide. In the further exploration and development of natural gas hydrate resources in this area, we must pay attention to the potential geological disaster risk.
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Abstract:
Submarine fans developed in the middle Miocene Meishan formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores reveal the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibit good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.
Submarine fans developed in the middle Miocene Meishan formation possess significant potential for natural gas exploration. Most of scholars believed that these Miocene submarine fans were formed primarily by turbidity currents. However, drilling cores reveal the presence of pebbles with a particle size of up to 5 cm in the sandy conglomerates. These sandy conglomerates exhibit good roundness and poor sorting, indicating that the traditional turbidity formation mechanism cannot fully explain the origin of this type of sandy conglomerates. Furthermore, the classic submarine fan model has limitations in predicting the distribution of sand bodies. Through a comprehensive study involving core, thin section observation, and grain size analysis, we have conducted a systematic investigation of the petrological characteristics and sedimentary structures of submarine fan in the study area. Our findings suggest that submarine fans in the study area resulted from the interaction of turbidity and hyperpycnal flow deposits. We have identified distinct sequences of turbidites and hyperpycnalites within the submarine fan. Based on the paleogeomorphlogy of the study area, we have established a genetic evolution model for the submarine fan in Meishan Formation. This model reveals that the hyperpycnites dominated by feldspathic litharenite, exhibit low compositional maturity. Poor sorting and subangular-circular of the rocks indicate middle-to-high structural maturity. Typical features of hyperpycnal flow include orientated gravel within block sandy conglomerates, reverse-to-normal grain order bedding, parallel bedding, carbonaceous debris, and biological fossil fragments. Multi stage superimposed turbidite sequence and hyperpycnites sequence developed in submarine fan in the study area. The early Meishan period is primarily composed of turbidite submarine fan lobes, while the middle Meishan period is dominated by hyperpycnites submarine fan channels. The late Meishan period, on the other hand, is mainly composed of turbidite submarine fan channels. We predict that more favorable submarine fan sand bodies could be found in the southern part of the study area. The results can serve as a basis for predicting the distribution of favorable submarine fan reservoirs of the Qiongdongnan Basin, and they hold significance for selecting exploration and development targets for hydrocarbon exploration.
, Available online ,
doi: 10.12284/hyxb2024014
Abstract:
Reliable assessment of the impact and risk of typhoons on coastal areas is very important for scientific resistance to typhoon disasters. China has a detailed typhoon observation record with a history of only 60 years, which makes it limited in estimating extreme wind speed with a long recurrence period and corresponding extreme wave height and tide level. The insufficient records also limits the application of data-driven models in typhoon disaster prediction. Therefore, it is necessary to construct synthetic typhoons based on the actual typhoon travel law to overcome the problem of insufficient historical observations. In this paper, 18 671 synthetic typhoons were constructed in the Northwest Pacific Ocean by using the Empirical Path Model based on kernel density estimation, and the parameters such as the start and end position, frequency of occurrence, travel speed and direction of the synthetic typhoons were statistically compared and analyzed with historical typhoons. The results show that the synthetic typhoon constructed based on the proposed method is generally consistent with the traveling characteristics of historical typhoons in the Northwest Pacific Ocean. Through the construction of these synthetic typhoons, a synthetic typhoon database with sufficient data and reliable performance can be provided for the study of extreme wave and storm surge along the coast of China.
Reliable assessment of the impact and risk of typhoons on coastal areas is very important for scientific resistance to typhoon disasters. China has a detailed typhoon observation record with a history of only 60 years, which makes it limited in estimating extreme wind speed with a long recurrence period and corresponding extreme wave height and tide level. The insufficient records also limits the application of data-driven models in typhoon disaster prediction. Therefore, it is necessary to construct synthetic typhoons based on the actual typhoon travel law to overcome the problem of insufficient historical observations. In this paper, 18 671 synthetic typhoons were constructed in the Northwest Pacific Ocean by using the Empirical Path Model based on kernel density estimation, and the parameters such as the start and end position, frequency of occurrence, travel speed and direction of the synthetic typhoons were statistically compared and analyzed with historical typhoons. The results show that the synthetic typhoon constructed based on the proposed method is generally consistent with the traveling characteristics of historical typhoons in the Northwest Pacific Ocean. Through the construction of these synthetic typhoons, a synthetic typhoon database with sufficient data and reliable performance can be provided for the study of extreme wave and storm surge along the coast of China.
, Available online
Abstract:
Using multiple observational subsurface temperature and salinity datasets based on Argo, we analyze the trend of 0–1 500 m ocean heat content in the Pacific between 2004 and 2020. It was found that the long-term trend of the Pacific ocean heat content showed a shift in 2013. The ocean heat content in 2013–2020 increased rapidly compared with that in 2004–2012. The linear trend of the former reaches about 0.50 × 1022 J/a, which is significantly higher than that of the latter. The Pacific has recently experienced rapid warming. During 2013–2020, the largest linear trend of the ocean heat content in the Pacific appeared in the western North Pacific, followed by the Tropical Pacific and eastern North Pacific. While the ocean heat content in the entire South Pacific showed a slightly decreasing trend. In the western North Pacific, the rapid increase of ocean heat content was concentrated in the Kuroshio Extension areas, and this warming trend is likely to be caused by the northward shift of the Kuroshio Extension main axis. It is worth mentioning that there was a local decreasing trend of ocean heat content in the south of Japan, and this cooling trend is associated with the strengthening of the Kuroshio large meander. In the Tropical Pacific where the warming trend is the second largest, the rapid increase of ocean heat content is likely to be induced by the thermocline deepening. In addition, we point out that the rapid warming in the Pacific is reflected by the rapid rise of sea level. The linear trend of sea level per 1 cm/a corresponds to the linear trend of ocean heat content of 0.11 × 109 J/(m2·a). This study elucidates the rapid warming of the Pacific since the end of the global warming hiatus, deepening our understanding of recent thermal conditions in the Pacific.
Using multiple observational subsurface temperature and salinity datasets based on Argo, we analyze the trend of 0–1 500 m ocean heat content in the Pacific between 2004 and 2020. It was found that the long-term trend of the Pacific ocean heat content showed a shift in 2013. The ocean heat content in 2013–2020 increased rapidly compared with that in 2004–2012. The linear trend of the former reaches about 0.50 × 1022 J/a, which is significantly higher than that of the latter. The Pacific has recently experienced rapid warming. During 2013–2020, the largest linear trend of the ocean heat content in the Pacific appeared in the western North Pacific, followed by the Tropical Pacific and eastern North Pacific. While the ocean heat content in the entire South Pacific showed a slightly decreasing trend. In the western North Pacific, the rapid increase of ocean heat content was concentrated in the Kuroshio Extension areas, and this warming trend is likely to be caused by the northward shift of the Kuroshio Extension main axis. It is worth mentioning that there was a local decreasing trend of ocean heat content in the south of Japan, and this cooling trend is associated with the strengthening of the Kuroshio large meander. In the Tropical Pacific where the warming trend is the second largest, the rapid increase of ocean heat content is likely to be induced by the thermocline deepening. In addition, we point out that the rapid warming in the Pacific is reflected by the rapid rise of sea level. The linear trend of sea level per 1 cm/a corresponds to the linear trend of ocean heat content of 0.11 × 109 J/(m2·a). This study elucidates the rapid warming of the Pacific since the end of the global warming hiatus, deepening our understanding of recent thermal conditions in the Pacific.
, Available online ,
doi: 10.12284/hyxb2024050
Abstract:
Planktonic copepods is an important group of zooplankton. It is of great significance to study the distribution characteristics of planktonic copepods abundance and its correlation with various environmental indicators. In this study, we analyzed environmental monitoring data of Haizhou bay, Lianyungang, Jiangsu province, from 2003 to 2022 using generalized additive model (GAM), to investigate the spatiotemporal variation of planktonic copepods and its correlation with other sea water indicators. The results showed that the abundance of planktonic copepods varied significantly different between seasons (p < 0.01), and the mean value of copepods was greater in spring than in summer than in autumn. The spatial distribution of abundance was generally low in the artificial reef area and high in the southern coastal area. GAM analysis showed that the main influencing factors were different between seasons. The main influencing factors in spring were dissolved oxygen, Chlorophyll a,\begin{document}${\mathrm{SiO}}_3^- $\end{document} ![]()
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Planktonic copepods is an important group of zooplankton. It is of great significance to study the distribution characteristics of planktonic copepods abundance and its correlation with various environmental indicators. In this study, we analyzed environmental monitoring data of Haizhou bay, Lianyungang, Jiangsu province, from 2003 to 2022 using generalized additive model (GAM), to investigate the spatiotemporal variation of planktonic copepods and its correlation with other sea water indicators. The results showed that the abundance of planktonic copepods varied significantly different between seasons (p < 0.01), and the mean value of copepods was greater in spring than in summer than in autumn. The spatial distribution of abundance was generally low in the artificial reef area and high in the southern coastal area. GAM analysis showed that the main influencing factors were different between seasons. The main influencing factors in spring were dissolved oxygen, Chlorophyll a,
, Available online
Abstract:
The buried hill oil and gas reservoirs have become an important exploration field in China's marine basins. The northwestern area of Shaleitian area of Bohai Bay Basin is a typical carbonate buried hill zone. Due to the lack of research on the reservoir control effect of multiple stage fractures and their related karstification, the oil and gas exploration of carbonate buried hills is restricted. This paper conducts a detailed analysis of the development characteristics of the fracture-cave system in carbonate buried hill reservoirs in the northwestern Shaleitian Uplift, and studies the reservoir control effects of fractures and karst. The results indicate that the lower Paleozoic carbonate buried hills in the northwestern area of Shaleitian uplift belong to fracture related karst reservoirs. The reservoir space includes dissolution pores, structural fractures, and expansion pores along the structural fractures. High quality reservoirs have lithological selectivity, and fractures and dissolution pores developed in microlite crystalline dolomite and fine crystalline dolomite are better. The reservoir mainly develops three sets of fractures, with NW and NEE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian . The third set of WE oriented tensile fractures is related to the intracratonic movement during the Himalayan orogeny, and compression is the main mechanism for forming high-density fractures. The later stage of extension is a necessary condition for the relaxation of fractures to form reservoir spaces. The Lower Paleozoic carbonate buried hill reservoirs have undergone three stages ofkarstification, which are karstification in the steady Caledonian tectonic background, karstification in the Indosinian compressive background, and fault block-horst karstification in the Yanshanian-Himalayan extensional background. In summary, the carbonate buried hill reservoirs in the northwestern Shaleitian uplift are formed by multiple stages and multiple types of tectonic-karst processes, and the analysis of the differences in the degree of recombination in different structural parts is an important factor in understanding the reservoir formation mechanism.
The buried hill oil and gas reservoirs have become an important exploration field in China's marine basins. The northwestern area of Shaleitian area of Bohai Bay Basin is a typical carbonate buried hill zone. Due to the lack of research on the reservoir control effect of multiple stage fractures and their related karstification, the oil and gas exploration of carbonate buried hills is restricted. This paper conducts a detailed analysis of the development characteristics of the fracture-cave system in carbonate buried hill reservoirs in the northwestern Shaleitian Uplift, and studies the reservoir control effects of fractures and karst. The results indicate that the lower Paleozoic carbonate buried hills in the northwestern area of Shaleitian uplift belong to fracture related karst reservoirs. The reservoir space includes dissolution pores, structural fractures, and expansion pores along the structural fractures. High quality reservoirs have lithological selectivity, and fractures and dissolution pores developed in microlite crystalline dolomite and fine crystalline dolomite are better. The reservoir mainly develops three sets of fractures, with NW and NEE oriented shear fractures mainly related to two tectonic compressions during the Indosinian and Late Yanshanian . The third set of WE oriented tensile fractures is related to the intracratonic movement during the Himalayan orogeny, and compression is the main mechanism for forming high-density fractures. The later stage of extension is a necessary condition for the relaxation of fractures to form reservoir spaces. The Lower Paleozoic carbonate buried hill reservoirs have undergone three stages ofkarstification, which are karstification in the steady Caledonian tectonic background, karstification in the Indosinian compressive background, and fault block-horst karstification in the Yanshanian-Himalayan extensional background. In summary, the carbonate buried hill reservoirs in the northwestern Shaleitian uplift are formed by multiple stages and multiple types of tectonic-karst processes, and the analysis of the differences in the degree of recombination in different structural parts is an important factor in understanding the reservoir formation mechanism.
, Available online ,
doi: 10.12284/hyxb0000-00
Abstract:
Quantitative studies on the spatial distribution of geometric parameters of complex submarine sand waves in the developmental area are rare, and the correlation between the complex geometric parameters of sand waves and environmental variables has not been clarified. Based on measured data of water depth, sediment grain size, and flow velocity in the western area of Hainan Island, the environmental variables of the study area were quantified and extracted. The morphological parameters of complex submarine sand waves were calculated using an automated extraction and analysis method, and the correlation between sand wave geometric parameters and environmental variables was analyzed. The results show that the morphological characteristics of submarine sand waves in the study area are complex and variable, with an average wavelength ranging from 64 to 340 m and an average wave height ranging from 0.39 to 4.13 m. There is a strong positive correlation between wave height and steepness, as well as between wave height and the average angle of the lee side. There is also a strong positive correlation between wavelength and symmetry, and a strong positive correlation between median sediment grain size and the average angle of the lee side and wave height. The development of submarine sand waves in the study area is less influenced by water depth. Under the action of tidal currents, sediment transport is mainly by traction, and the erosion of submarine sand waves is relatively weak. The evolution of sand waves is mainly characterized by vertical growth and migration, with wave height growth prioritized over wavelength increase. Under stable tidal flow conditions, regional sediment supply and sediment grain size can both affect the scale of submarine sand waves.
Quantitative studies on the spatial distribution of geometric parameters of complex submarine sand waves in the developmental area are rare, and the correlation between the complex geometric parameters of sand waves and environmental variables has not been clarified. Based on measured data of water depth, sediment grain size, and flow velocity in the western area of Hainan Island, the environmental variables of the study area were quantified and extracted. The morphological parameters of complex submarine sand waves were calculated using an automated extraction and analysis method, and the correlation between sand wave geometric parameters and environmental variables was analyzed. The results show that the morphological characteristics of submarine sand waves in the study area are complex and variable, with an average wavelength ranging from 64 to 340 m and an average wave height ranging from 0.39 to 4.13 m. There is a strong positive correlation between wave height and steepness, as well as between wave height and the average angle of the lee side. There is also a strong positive correlation between wavelength and symmetry, and a strong positive correlation between median sediment grain size and the average angle of the lee side and wave height. The development of submarine sand waves in the study area is less influenced by water depth. Under the action of tidal currents, sediment transport is mainly by traction, and the erosion of submarine sand waves is relatively weak. The evolution of sand waves is mainly characterized by vertical growth and migration, with wave height growth prioritized over wavelength increase. Under stable tidal flow conditions, regional sediment supply and sediment grain size can both affect the scale of submarine sand waves.
, Available online ,
doi: 10.12284/hyxb2024008
Abstract:
There are also obvious inter-annual variations of the North Equatorial Countercurrent (NECC) during the occurrence and development of the El Niño-Southern Oscillation (ENSO), but its changing process in hydroecological conditions and response mechanism influenced by ENSO cycle are still unclear. Taking the NECC affected area in the tropical western Pacific as the study area, this paper analyzes the characteristics of the changes of hydroecoclimatic conditions at different stages during the ENSO cycle during autumn and winter transition period from 2006 to 2022. Results reveal that there are high chlorophyll concentration bands in the NECC source area and its path, which are formed by the combined influence of nutrients carried by the NECC from its source area and the New Guinea coastal Undercurrent. The upwelling of the Mindanao Dome also has a great influence on the nutrient supply. When El Niño events occurred, the westerly wind events in the tropical western Pacific increased, the NECC strengthened, a large amount of surface water moved eastward, the sea level in the study area decreased, the deep water recharge to the shallow layer increased, and the deep cold water rose. The jointly enhanced NECC, New Guinea Coastal Current, New Guinea Coastal Undercurrent and Mindanao Dome upwelling transport more nutrients to the sea surface from both horizontal and vertical levels, resulting in significant increases in surface chlorophyll concentration and primary organic carbon production by all types of phytoplankton. When La Niña events occurred, the changes of ecohydroclimatic conditions in the NECC affected area are almost opposite to those during El Niño events, but the degree of change is weaker than that during El Nino events. The combined weakening of the NECC, the New Guinea coastal undercurrent and the Mindanao Dome upwelling significantly reduce the nutrients delivered to the sea surface from the horizontal and vertical levels. The chlorophyll concentration and primary organic carbon production by all types of phytoplankton decreased significantly. This paper proposes a model of the response mechanism of the evolution of hydroecoclimatic conditions in the NECC affected area to El Niño and La Niña events, which is conducive to further analysis of the role of ENSO cycle in local ecological effects and hydroclimatic evolution. It has important significance for understanding the impact of global climate change on the material cycle.
There are also obvious inter-annual variations of the North Equatorial Countercurrent (NECC) during the occurrence and development of the El Niño-Southern Oscillation (ENSO), but its changing process in hydroecological conditions and response mechanism influenced by ENSO cycle are still unclear. Taking the NECC affected area in the tropical western Pacific as the study area, this paper analyzes the characteristics of the changes of hydroecoclimatic conditions at different stages during the ENSO cycle during autumn and winter transition period from 2006 to 2022. Results reveal that there are high chlorophyll concentration bands in the NECC source area and its path, which are formed by the combined influence of nutrients carried by the NECC from its source area and the New Guinea coastal Undercurrent. The upwelling of the Mindanao Dome also has a great influence on the nutrient supply. When El Niño events occurred, the westerly wind events in the tropical western Pacific increased, the NECC strengthened, a large amount of surface water moved eastward, the sea level in the study area decreased, the deep water recharge to the shallow layer increased, and the deep cold water rose. The jointly enhanced NECC, New Guinea Coastal Current, New Guinea Coastal Undercurrent and Mindanao Dome upwelling transport more nutrients to the sea surface from both horizontal and vertical levels, resulting in significant increases in surface chlorophyll concentration and primary organic carbon production by all types of phytoplankton. When La Niña events occurred, the changes of ecohydroclimatic conditions in the NECC affected area are almost opposite to those during El Niño events, but the degree of change is weaker than that during El Nino events. The combined weakening of the NECC, the New Guinea coastal undercurrent and the Mindanao Dome upwelling significantly reduce the nutrients delivered to the sea surface from the horizontal and vertical levels. The chlorophyll concentration and primary organic carbon production by all types of phytoplankton decreased significantly. This paper proposes a model of the response mechanism of the evolution of hydroecoclimatic conditions in the NECC affected area to El Niño and La Niña events, which is conducive to further analysis of the role of ENSO cycle in local ecological effects and hydroclimatic evolution. It has important significance for understanding the impact of global climate change on the material cycle.
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Abstract:
Tidal flats maintain a complex ecosystem, while its formation is driven by multi-factor interaction, including hydrodynamics, sediment transport, and biological processes. In particular, investigating tidal flat biological processes and elucidating their biological-physical effects are current research hotspots and challenges in the field of marine science. This study focused on intertidal biofilms, constructed a two-dimensional biomorphodynamic model which coupled biofilms with hydrodynamics, sediment transport, and bed level change, to explore the role of biofilms in sediment transport and geomorphological evolution. The biomorphodynamic model was validated using literature data, indicating that the constructed model can simulate the growth pattern and interannual variation of biofilms well. Model results show that tidal creeks with biofilm attachment are more fully extended towards the landward side, showing a branching distribution when hydrodynamics are weak, and biofilms were distributed on both sides of the intertidal zone. Through quantitative analysis of tidal creek morphology, it is found that the presence of biofilms promoted an increase in the number of tidal creek and their development in the vertical direction, while limiting the increase in their width. Compared to tidal flats without the influence of biofilms, the average depth of tidal creeks increases, the total area decreases, the total length increases, the average width decreases, and the overall volume increases. The research outcome of this study deepens the understanding of the role of biofilms on tidal flat evolution and provides a scientific basis for coastal zone protection and ecological restoration projects.
Tidal flats maintain a complex ecosystem, while its formation is driven by multi-factor interaction, including hydrodynamics, sediment transport, and biological processes. In particular, investigating tidal flat biological processes and elucidating their biological-physical effects are current research hotspots and challenges in the field of marine science. This study focused on intertidal biofilms, constructed a two-dimensional biomorphodynamic model which coupled biofilms with hydrodynamics, sediment transport, and bed level change, to explore the role of biofilms in sediment transport and geomorphological evolution. The biomorphodynamic model was validated using literature data, indicating that the constructed model can simulate the growth pattern and interannual variation of biofilms well. Model results show that tidal creeks with biofilm attachment are more fully extended towards the landward side, showing a branching distribution when hydrodynamics are weak, and biofilms were distributed on both sides of the intertidal zone. Through quantitative analysis of tidal creek morphology, it is found that the presence of biofilms promoted an increase in the number of tidal creek and their development in the vertical direction, while limiting the increase in their width. Compared to tidal flats without the influence of biofilms, the average depth of tidal creeks increases, the total area decreases, the total length increases, the average width decreases, and the overall volume increases. The research outcome of this study deepens the understanding of the role of biofilms on tidal flat evolution and provides a scientific basis for coastal zone protection and ecological restoration projects.
, Available online ,
doi: 10.12284/hyxb2024028
Abstract:
The Chukchi Borderland served as the critical gateway for the inflow of Atlantic Water (AW, which is the most important heat storage layer in the Arctic Ocean) into the Canada Basin in the western Arctic Ocean. One of the key issues is how the AW and Pacific Winter Water (PWW) interacts in this complex topography region. The answer to this question will shed light on the important role of AW in the Arctic Ocean. In this study, based on the multi-sources’ quality controlled hydrographic data during 1999−2021, the variation of AW, PWW and the double-diffusive staircases in the Chukchi Borderland are studied in details. We identified three anomalous warm events of AW that occurred in year 2000, 2012 and 2018 with the maximum potential temperature over 1°C. The vertical averaged heat content between the PWW and AW shows a warming trend in the central and eastern region of the Chukchi Borderland. The major reason for this is the warming of PWW. The depth of PWW is more sensitive to the shifting of the Beaufort Gyre (BG) than that of the AW. The combined changes of PWW and AW lead to the variation of double-diffusive staircases, which show a regime shift from large to small thickness and to largely decayed in the Canada Basin. Our results suggest that the major mechanism for this transition is the cooling of AW along with the stronger stratification that restricts the vertical mixing for all.
The Chukchi Borderland served as the critical gateway for the inflow of Atlantic Water (AW, which is the most important heat storage layer in the Arctic Ocean) into the Canada Basin in the western Arctic Ocean. One of the key issues is how the AW and Pacific Winter Water (PWW) interacts in this complex topography region. The answer to this question will shed light on the important role of AW in the Arctic Ocean. In this study, based on the multi-sources’ quality controlled hydrographic data during 1999−2021, the variation of AW, PWW and the double-diffusive staircases in the Chukchi Borderland are studied in details. We identified three anomalous warm events of AW that occurred in year 2000, 2012 and 2018 with the maximum potential temperature over 1°C. The vertical averaged heat content between the PWW and AW shows a warming trend in the central and eastern region of the Chukchi Borderland. The major reason for this is the warming of PWW. The depth of PWW is more sensitive to the shifting of the Beaufort Gyre (BG) than that of the AW. The combined changes of PWW and AW lead to the variation of double-diffusive staircases, which show a regime shift from large to small thickness and to largely decayed in the Canada Basin. Our results suggest that the major mechanism for this transition is the cooling of AW along with the stronger stratification that restricts the vertical mixing for all.
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Abstract:
In recent years, natural processes and human activities have significantly altered the Huanghe River channel and the coastal geomorphic pattern, while the impact of the dramatic geomorphic evolution on the coastal hydrodynamics has not been fully studied. Based on series images captured by the Landsat satellites and bathymetric measurements, this paper analyzed the shorelines and topography changes of the Huanghe River Delta from 1992 to 2020. Several sets of numerical models covering the entire Bohai Sea were established by TELEMAC-2D to investigate the response of tidal dynamics to geomorphic evolution and its depositional effects in the Huanghe River Delta. The results show that the erosion and deposition had significant spatial and temporal heterogeneity, and there were multiple siltation and erosion centers. The erosion center outside the old Qingshuigou Estuary moved 9.6 km to the south during 2000–2020, and the one outside the Diaokou Estuary moved 6.4 km to the east during 1992–2015. The tidal dynamics were dominated by the coastline and terrain changes on the medium and long time scales. The tidal range of the Diaokou estuary decreased, while the old and the new estuary increased. And the tidal range at –5 m depth had a maximum variation of 0.27 m. The K1 tidal amplitude increased significantly, while the M2 tidal amplitude was considerably reduced, and the amphidromic point near Dongying port eastward migration of 3.8 km. The high velocity outside the Diaokou estuary and the old estuary continued to weaken, and another high velocity area gradually developed outside the current estuary. The continuous and stable high velocity area caused the erosion of the subaqueous delta and the coarsening of sediment.
In recent years, natural processes and human activities have significantly altered the Huanghe River channel and the coastal geomorphic pattern, while the impact of the dramatic geomorphic evolution on the coastal hydrodynamics has not been fully studied. Based on series images captured by the Landsat satellites and bathymetric measurements, this paper analyzed the shorelines and topography changes of the Huanghe River Delta from 1992 to 2020. Several sets of numerical models covering the entire Bohai Sea were established by TELEMAC-2D to investigate the response of tidal dynamics to geomorphic evolution and its depositional effects in the Huanghe River Delta. The results show that the erosion and deposition had significant spatial and temporal heterogeneity, and there were multiple siltation and erosion centers. The erosion center outside the old Qingshuigou Estuary moved 9.6 km to the south during 2000–2020, and the one outside the Diaokou Estuary moved 6.4 km to the east during 1992–2015. The tidal dynamics were dominated by the coastline and terrain changes on the medium and long time scales. The tidal range of the Diaokou estuary decreased, while the old and the new estuary increased. And the tidal range at –5 m depth had a maximum variation of 0.27 m. The K1 tidal amplitude increased significantly, while the M2 tidal amplitude was considerably reduced, and the amphidromic point near Dongying port eastward migration of 3.8 km. The high velocity outside the Diaokou estuary and the old estuary continued to weaken, and another high velocity area gradually developed outside the current estuary. The continuous and stable high velocity area caused the erosion of the subaqueous delta and the coarsening of sediment.
Evaluation of benthic ecological quality status in the Yalu River estuary based on environmental DNA
, Available online ,
doi: 10.12284/hyxb2024058
Abstract:
Investigating the potential for application of environmental DNA to identify benthic organisms for evaluating ecological quality status collection of 17 benthic samples from the Yalu River estuary, environmental DNA and morphological identification and comparative analyses of the resulting ecological quality assessment indices (AMBI, BENTIX, Shannon-Wiener H', M-AMBI) were used, respectively. The results show: environmental DNA identification of organisms belonging to 10 class, 16 orders, 19 families, 20 genera and 22 species, morphological identification of organisms belonging to 9 class, 27 orders, 43 families, 55 genera and 57 species, with a total of 10 organisms; the two methods of identification yielded AMBI inter-index (R = 0.428, p = 0.043, y = 0.32x + 1.08), BENTIX inter-exponential (R = 0.430, p = 0.043, y = 0.28x + 3.59) significant consistency exists, while there was significant difference between the Shannon-Wiener H' indices; the two methods of identification yielded AMBI intergrade,M-AMBI intergrade higher similarity, 51.02 per cent, 44.90 per cent, respectively; the AMBI and M-AMBI grades from the two identification methods were more in line with the actual situation and evaluated the overall ecological quality status of the Yalu River estuary as good. This study demonstrates that the identification of benthic organisms based on environmental DNA to evaluate the ecological quality status has a high potential for application in marine environmental monitoring surveys.
Investigating the potential for application of environmental DNA to identify benthic organisms for evaluating ecological quality status collection of 17 benthic samples from the Yalu River estuary, environmental DNA and morphological identification and comparative analyses of the resulting ecological quality assessment indices (AMBI, BENTIX, Shannon-Wiener H', M-AMBI) were used, respectively. The results show: environmental DNA identification of organisms belonging to 10 class, 16 orders, 19 families, 20 genera and 22 species, morphological identification of organisms belonging to 9 class, 27 orders, 43 families, 55 genera and 57 species, with a total of 10 organisms; the two methods of identification yielded AMBI inter-index (R = 0.428, p = 0.043, y = 0.32x + 1.08), BENTIX inter-exponential (R = 0.430, p = 0.043, y = 0.28x + 3.59) significant consistency exists, while there was significant difference between the Shannon-Wiener H' indices; the two methods of identification yielded AMBI intergrade,M-AMBI intergrade higher similarity, 51.02 per cent, 44.90 per cent, respectively; the AMBI and M-AMBI grades from the two identification methods were more in line with the actual situation and evaluated the overall ecological quality status of the Yalu River estuary as good. This study demonstrates that the identification of benthic organisms based on environmental DNA to evaluate the ecological quality status has a high potential for application in marine environmental monitoring surveys.
, Available online
Abstract:
In this paper, a high spatial-temporal resolution sea ice concentration estimation method for the Arctic melting season is proposed, aiming to improve the overestimation of sea ice concentration in seawater by the Global Navigation Satellite System-Reflectometry (GNSS-R). The method utilizes machine learning algorithms to extract feature parameters from the Delay Doppler Maps (DDM) obtained through GNSS-R and combines them with sea surface temperature data to establish a LightGBM model. The inversion results are then subjected to correlation analysis and evaluation against reference sea ice concentration values. The model's performance is compared with the sea ice concentration product from OSI SAF, demonstrating good consistency, with correlation coefficient, mean absolute error, and root mean square error being 0.965, 0.061, and 0.090, respectively. This approach enables high-precision estimation of sea ice concentration in the Arctic marginal ice zone.
In this paper, a high spatial-temporal resolution sea ice concentration estimation method for the Arctic melting season is proposed, aiming to improve the overestimation of sea ice concentration in seawater by the Global Navigation Satellite System-Reflectometry (GNSS-R). The method utilizes machine learning algorithms to extract feature parameters from the Delay Doppler Maps (DDM) obtained through GNSS-R and combines them with sea surface temperature data to establish a LightGBM model. The inversion results are then subjected to correlation analysis and evaluation against reference sea ice concentration values. The model's performance is compared with the sea ice concentration product from OSI SAF, demonstrating good consistency, with correlation coefficient, mean absolute error, and root mean square error being 0.965, 0.061, and 0.090, respectively. This approach enables high-precision estimation of sea ice concentration in the Arctic marginal ice zone.
, Available online ,
doi: 10.12284/hyxb2024042
Abstract:
In order to explore the relationship between zooplankton community structure and environmental factors in Oujiang River Estuary, four voyages were conducted in March (winter), May (spring), August (summer) and November (autumn) in 2021 to investigate the zooplankton and other environmental factors such as sea temperature, salinity and chlorophyll-a in Oujiang River Estuary sea area. The results showed that 78 species of zooplankton were identified, including 16 species of larva, it belongs to 8 classes and 14 categories , with the highest number of species in summer (47 species) and the lowest number in winter (23 species). The dominant species (Y ≥ 0.02) include Calanus sinicus, Sinocalanus sinensis, Acartia pacifica, and Centropages dorsispinatus, 17 species. The average annual abundance of zooplankton was (162.95 ± 310.96) ind./m3, and the average annual biomass was (118.85 ± 62.80) mg/m3. The abundance and biomass of zooplankton were the highest in spring and the lowest in autumn. The abundance in winter was higher than that in summer, and the biomass was lower than that in summer. The average annual Shannon-Wiener diversity index (H'), Pielou evenness index (J') and Margalef richness index (D) were 1.500 ± 0.702, 0.656 ± 0.270 and 2.301 ± 1.087, respectively. Spearman correlation analysis and CCA canonical correspondence analysis showed that sea temperature, salinity, Chl a concentration and phytoplankton abundance were important environmental factors affecting the dominant abundance of zooplankton in the Oujiang River Estuary. It provides scientific reference for the study on the influence of seasonal environmental changes on zooplankton in Oujiang River Estuary, and provides basic data and theoretical basis for the sustainable development of biological resources in Oujiang River Estuary.
In order to explore the relationship between zooplankton community structure and environmental factors in Oujiang River Estuary, four voyages were conducted in March (winter), May (spring), August (summer) and November (autumn) in 2021 to investigate the zooplankton and other environmental factors such as sea temperature, salinity and chlorophyll-a in Oujiang River Estuary sea area. The results showed that 78 species of zooplankton were identified, including 16 species of larva, it belongs to 8 classes and 14 categories , with the highest number of species in summer (47 species) and the lowest number in winter (23 species). The dominant species (Y ≥ 0.02) include Calanus sinicus, Sinocalanus sinensis, Acartia pacifica, and Centropages dorsispinatus, 17 species. The average annual abundance of zooplankton was (162.95 ± 310.96) ind./m3, and the average annual biomass was (118.85 ± 62.80) mg/m3. The abundance and biomass of zooplankton were the highest in spring and the lowest in autumn. The abundance in winter was higher than that in summer, and the biomass was lower than that in summer. The average annual Shannon-Wiener diversity index (H'), Pielou evenness index (J') and Margalef richness index (D) were 1.500 ± 0.702, 0.656 ± 0.270 and 2.301 ± 1.087, respectively. Spearman correlation analysis and CCA canonical correspondence analysis showed that sea temperature, salinity, Chl a concentration and phytoplankton abundance were important environmental factors affecting the dominant abundance of zooplankton in the Oujiang River Estuary. It provides scientific reference for the study on the influence of seasonal environmental changes on zooplankton in Oujiang River Estuary, and provides basic data and theoretical basis for the sustainable development of biological resources in Oujiang River Estuary.
, Available online ,
doi: 10.12284/hyxb2024038
Abstract:
To understand the characteristics and distribution of benthic shellfish communities in the vicinity of the Nanji Islands, we conducted bottom trawl surveys in the surrounding waters during October 2022 (autumn) and March 2023 (spring). The findings reveal that a total of 49 benthic shellfish species were captured, spanning 2 classes, 6 orders, and 17 families. During spring, the average abundance of benthic shellfish was (2 429 ± 2 038) ind./Agt, with an average biomass of (4 849.79 ± 2 513.84) g/Agt. In autumn, the average abundance was (1 149 ± 1 589) ind./Agt, with an average biomass of (4 985.30 ± 2 159.23) g/Agt. The primary dominant species comprised Turritella bacillum, Murex trapa, Tegillarca nodifera, Inquisitor jeffreysii, Bufonaria rana, Cancellaria sinensis and Trigonaphera bocageana. Notably, Turritella bacillum emerged as a dominant species in both spring and autumn, with dominance significantly surpassing that of other species.The dominance of benthic shellfish communities in this marine area appears relatively stable, with the community's functionality and nature being primarily governed by a select few species. This study provides a reference basis for the dynamic changes in the marine ecosystem of the Nansha Islands and offers foundational data for the protection of marine ecological environments.
To understand the characteristics and distribution of benthic shellfish communities in the vicinity of the Nanji Islands, we conducted bottom trawl surveys in the surrounding waters during October 2022 (autumn) and March 2023 (spring). The findings reveal that a total of 49 benthic shellfish species were captured, spanning 2 classes, 6 orders, and 17 families. During spring, the average abundance of benthic shellfish was (2 429 ± 2 038) ind./Agt, with an average biomass of (4 849.79 ± 2 513.84) g/Agt. In autumn, the average abundance was (1 149 ± 1 589) ind./Agt, with an average biomass of (4 985.30 ± 2 159.23) g/Agt. The primary dominant species comprised Turritella bacillum, Murex trapa, Tegillarca nodifera, Inquisitor jeffreysii, Bufonaria rana, Cancellaria sinensis and Trigonaphera bocageana. Notably, Turritella bacillum emerged as a dominant species in both spring and autumn, with dominance significantly surpassing that of other species.The dominance of benthic shellfish communities in this marine area appears relatively stable, with the community's functionality and nature being primarily governed by a select few species. This study provides a reference basis for the dynamic changes in the marine ecosystem of the Nansha Islands and offers foundational data for the protection of marine ecological environments.
, Available online ,
doi: 10.12284/hyxb2024000
Abstract:
Beach nourishment, as a widely-adopted soft solution to coastal erosion, can effectively alleviate the beach erosion induced by the construction of artificial islands. This paper takes the nourished beaches on both sides of the wave shadow zone of an artificial island in Haikou Bay as an example. Based on the bimonthly surveys of beach profiles and shorelines since nourishment, the characteristics of beach erosion and accretion and the associated driving factors were analyzed by using Empirical Orthogonal Function (EOF) and Digital Shoreline Analysis System methods. The EOF results showed that the first two eigenvalues accounted for more than 90% of the total variance, which could reflect the main spatio-temporal changes of the beaches. The area with conspicuous changes, corresponding to the first spatial mode, was located between the outer edge of the beach berm to the mean sea level, in which there were significant differences between the nourished beaches on both sides of the wave shadow zone and the natural beach in the wave shadow zone. The temporal mode showed that the most significant changes of the nourished beaches occurred in the initial four months after nourishment, followed by mild profile changes. The second spatial mode demonstrated the impact of typhoons on the beaches, resulting in the accumulation and leveling of some low-lying sites on the beach berms in the wave shadow zone. This study found that the evolution of nourished beaches under the influence of an artificial island in Haikou Bay could be divided into two stages. The first stage was the adaptation period, during which the artificially designed beach profile adjusted to the equilibrium state for adapting to the local hydrodynamics. The equilibrium time of nourished profiles was approximately 4 months, during which beach changes were dominated by cross-shore sediment transport. The second stage was dominated by the longshore sediment transport induced by the artificial island, resulting in sediment transport from the eastern and western sides of the artificial island to the wave shadow zone. At that time, the nourished beach shoreline in Haikou Bay had not reached the equilibrium state. The beaches on both sides of the wave shadow zone would continue to retreat in the future, while the shoreline in the wave shadow zone would advance into the sea for about 690 m until it reaches the equilibrium. This study would be helpful for the analysis of the beach evolution and beach restoration of similar cases.
Beach nourishment, as a widely-adopted soft solution to coastal erosion, can effectively alleviate the beach erosion induced by the construction of artificial islands. This paper takes the nourished beaches on both sides of the wave shadow zone of an artificial island in Haikou Bay as an example. Based on the bimonthly surveys of beach profiles and shorelines since nourishment, the characteristics of beach erosion and accretion and the associated driving factors were analyzed by using Empirical Orthogonal Function (EOF) and Digital Shoreline Analysis System methods. The EOF results showed that the first two eigenvalues accounted for more than 90% of the total variance, which could reflect the main spatio-temporal changes of the beaches. The area with conspicuous changes, corresponding to the first spatial mode, was located between the outer edge of the beach berm to the mean sea level, in which there were significant differences between the nourished beaches on both sides of the wave shadow zone and the natural beach in the wave shadow zone. The temporal mode showed that the most significant changes of the nourished beaches occurred in the initial four months after nourishment, followed by mild profile changes. The second spatial mode demonstrated the impact of typhoons on the beaches, resulting in the accumulation and leveling of some low-lying sites on the beach berms in the wave shadow zone. This study found that the evolution of nourished beaches under the influence of an artificial island in Haikou Bay could be divided into two stages. The first stage was the adaptation period, during which the artificially designed beach profile adjusted to the equilibrium state for adapting to the local hydrodynamics. The equilibrium time of nourished profiles was approximately 4 months, during which beach changes were dominated by cross-shore sediment transport. The second stage was dominated by the longshore sediment transport induced by the artificial island, resulting in sediment transport from the eastern and western sides of the artificial island to the wave shadow zone. At that time, the nourished beach shoreline in Haikou Bay had not reached the equilibrium state. The beaches on both sides of the wave shadow zone would continue to retreat in the future, while the shoreline in the wave shadow zone would advance into the sea for about 690 m until it reaches the equilibrium. This study would be helpful for the analysis of the beach evolution and beach restoration of similar cases.
, Available online ,
doi: 10.12284/hyxb2024054
Abstract:
The deposition fluxes of 210Po, 210Bi and 210Pb in atmosphere are the basis for the application of radionuclide tracing in the ocean. In order to reveal the spatio-temporal variation of the activity of 210Po, 210Bi and 210Pb in nearshore areas and estimate their deposition fluxes into the sea, In this paper, sampling observation and analysis of two typical areas near the East China Sea in Shanghai and Xiamen in different periods are carried out.A time series study was conducted on the activity of 210Po, 210Pb and 210Bi in Shanghai and Xiamen from September 2016 to February 2017 and from September to December 2021, respectively. The residence time of particulate matter was calculated based on 210Po/210Pb and 210Bi/210Pb. Deposition fluxes of three nuclides were also estimated. This paper reported the activity of 210Po, 210Bi and 210Pb in Shanghai in autumn and winter of 2016.The activity ranges of 210Po, 210Pb and 210Bi were 0.11-1.27 mBq/m3, 0.45-1.83 mBq/m3 and 1.12-6.10 mBq/m3, respectively. In the fall of 2021, the activity ranges of 210Po, 210Bi and 210Pb in Xiamen were 0.05-0.85mBq/m3, 0.61-2.42mBq/m3 and 0.18-1.32mBq/m3, respectively.The activity of each nuclide in Shanghai was higher than that in Xiamen. The aerosol residence time (τPo-Pb) over Shanghai and Xiamen are 28-202d and 19-355d, respectively. In this paper, based on a one-dimensional simple aerosol deposition rate model, the atmospheric deposition fluxes of 210Pb, 210Bi and 210Po over Shanghai area into the East China Sea are estimated, and their variation ranges are 0.1-26.35Bq /m2/d, 0.04-7.91Bq /m2/d and 0.01-5.49 Bq /m2/d, respectively. The sedimentation fluxes of 210Po, 210Bi and 210Pb estimated based on the model are close to the actual observed values in the study area during the same period in winter within a certain range. The feasibility of estimating the deposition flux of nuclide into the sea with a simple one dimensional aerosol deposition rate model is verified.
The deposition fluxes of 210Po, 210Bi and 210Pb in atmosphere are the basis for the application of radionuclide tracing in the ocean. In order to reveal the spatio-temporal variation of the activity of 210Po, 210Bi and 210Pb in nearshore areas and estimate their deposition fluxes into the sea, In this paper, sampling observation and analysis of two typical areas near the East China Sea in Shanghai and Xiamen in different periods are carried out.A time series study was conducted on the activity of 210Po, 210Pb and 210Bi in Shanghai and Xiamen from September 2016 to February 2017 and from September to December 2021, respectively. The residence time of particulate matter was calculated based on 210Po/210Pb and 210Bi/210Pb. Deposition fluxes of three nuclides were also estimated. This paper reported the activity of 210Po, 210Bi and 210Pb in Shanghai in autumn and winter of 2016.The activity ranges of 210Po, 210Pb and 210Bi were 0.11-1.27 mBq/m3, 0.45-1.83 mBq/m3 and 1.12-6.10 mBq/m3, respectively. In the fall of 2021, the activity ranges of 210Po, 210Bi and 210Pb in Xiamen were 0.05-0.85mBq/m3, 0.61-2.42mBq/m3 and 0.18-1.32mBq/m3, respectively.The activity of each nuclide in Shanghai was higher than that in Xiamen. The aerosol residence time (τPo-Pb) over Shanghai and Xiamen are 28-202d and 19-355d, respectively. In this paper, based on a one-dimensional simple aerosol deposition rate model, the atmospheric deposition fluxes of 210Pb, 210Bi and 210Po over Shanghai area into the East China Sea are estimated, and their variation ranges are 0.1-26.35Bq /m2/d, 0.04-7.91Bq /m2/d and 0.01-5.49 Bq /m2/d, respectively. The sedimentation fluxes of 210Po, 210Bi and 210Pb estimated based on the model are close to the actual observed values in the study area during the same period in winter within a certain range. The feasibility of estimating the deposition flux of nuclide into the sea with a simple one dimensional aerosol deposition rate model is verified.
, Available online ,
doi: 10.12284/hyxb2024048
Abstract:
The “fairy circle” represents a unique form of spatial self-organization found within coastal salt marsh ecosystems, profoundly influencing the productivity, stability, and resilience of these wetlands. Unmanned Aerial Vehicle (UAV) imagery plays a pivotal role in precisely pinpointing the “fairy circle” locations and deciphering their temporal and spatial development trends. However, identifying “fairy circle” pixels within two-dimensional images poses a considerable technical challenge due to the subtle differences in color and shape characteristics between these pixels and their surroundings. Therefore, intelligently and accurately identify “fairy circle” pixels from two-dimensional images and form individual “fairy circle” for the identified pixels are the current technical difficulties. This paper introduces an innovative approach to extract “fairy circle” from UAV images by integrating the SAM (Segment Anything Model) visual segmentation model with random forest machine learning. This novel method accomplishes the recognition and extraction of individual “fairy circle” through a two-step process: segmentation followed by classification. Initially, we establish Dice (Sørensen-Dice coefficient) and IOU (Intersection Over Union) evaluation metrics, and optimize SAM’s pre-trained model parameters, which produces segmentation mask devoid of attribute information by fully automated image segmentation. Subsequently, we align the segmentation mask with the original image, and utilizes RGB (red, green, and blue) color channels and spatial coordinates to construct a feature index for the segmentation mask. These features undergo analysis and selection based on Out-of-Bag (OOB) error reduction and feature distribution patterns. Ultimately, the refined features are employed to train a random forest model, enabling the automatic identification and classification of “fairy circle” vegetation, common vegetation, and bare flat areas. The experimental results show that the average correct extraction rate of "fairy circle" is 96.1%, and the average wrong extraction rate is 9.5%, which provides methodological and technological support for the accurate depiction of the spatial and temporal pattern of "fairy circle" as well as the processing of coastal remote sensing images by UAVs.
The “fairy circle” represents a unique form of spatial self-organization found within coastal salt marsh ecosystems, profoundly influencing the productivity, stability, and resilience of these wetlands. Unmanned Aerial Vehicle (UAV) imagery plays a pivotal role in precisely pinpointing the “fairy circle” locations and deciphering their temporal and spatial development trends. However, identifying “fairy circle” pixels within two-dimensional images poses a considerable technical challenge due to the subtle differences in color and shape characteristics between these pixels and their surroundings. Therefore, intelligently and accurately identify “fairy circle” pixels from two-dimensional images and form individual “fairy circle” for the identified pixels are the current technical difficulties. This paper introduces an innovative approach to extract “fairy circle” from UAV images by integrating the SAM (Segment Anything Model) visual segmentation model with random forest machine learning. This novel method accomplishes the recognition and extraction of individual “fairy circle” through a two-step process: segmentation followed by classification. Initially, we establish Dice (Sørensen-Dice coefficient) and IOU (Intersection Over Union) evaluation metrics, and optimize SAM’s pre-trained model parameters, which produces segmentation mask devoid of attribute information by fully automated image segmentation. Subsequently, we align the segmentation mask with the original image, and utilizes RGB (red, green, and blue) color channels and spatial coordinates to construct a feature index for the segmentation mask. These features undergo analysis and selection based on Out-of-Bag (OOB) error reduction and feature distribution patterns. Ultimately, the refined features are employed to train a random forest model, enabling the automatic identification and classification of “fairy circle” vegetation, common vegetation, and bare flat areas. The experimental results show that the average correct extraction rate of "fairy circle" is 96.1%, and the average wrong extraction rate is 9.5%, which provides methodological and technological support for the accurate depiction of the spatial and temporal pattern of "fairy circle" as well as the processing of coastal remote sensing images by UAVs.
, Available online ,
doi: 10.12284/hyxb2024056
Abstract:
To clarify the composition and distribution characteristics of macrobenthic communities in Yantai Changdao Island marine ranch and evaluate the impact of marine ranching on these macrobenthos, sampling stations were set up inside and outside the marine ranch in October 2022. Surveys of macrobenthic animals and the characteristics of macrobenthic communities were analyzed. A total of 88 species of macrobenthic animals were collected and identified during this voyage. Although the number of species in the pasture and control area was similar, the dominant groups differed. In the pasture, 70 species were identified, with mollusks being the dominant group; whereas, in the control area, 69 species were identified, with annelids as the dominant group. Eight dominant species were found, including 3 mollusk species in the pasture and 6 species in the control area, comprising 2 mollusk species, 1 echinoderm species, and 3 annelid species. The average abundance and biomass of macrobenthic animals in the pasture were significantly higher than those in the control area. However, Margalef species richness index (d), Pielou evenness index (J'), and Shannon Wiener diversity index (H') values showed little difference between the pasture and the outside. The results of Cluster analysis (CLUSTER) and non-metric multidimensional scaling (NMDS) analysis indicated that relatively low similarity among each station inside and outside the marine ranch. The AMBI and m-AMBI analyses revealed that the overall pollution disturbance in the studied water area was relatively small, indicating good benthic ecological health. Combined with historical data, the analysis revealed a significant increase in species abundance and biomass of macrobenthic communities in the surveyed area. These results suggest that the development of marine pastures has a certain degree of impact on the growth and development of macrobenthic communities.
To clarify the composition and distribution characteristics of macrobenthic communities in Yantai Changdao Island marine ranch and evaluate the impact of marine ranching on these macrobenthos, sampling stations were set up inside and outside the marine ranch in October 2022. Surveys of macrobenthic animals and the characteristics of macrobenthic communities were analyzed. A total of 88 species of macrobenthic animals were collected and identified during this voyage. Although the number of species in the pasture and control area was similar, the dominant groups differed. In the pasture, 70 species were identified, with mollusks being the dominant group; whereas, in the control area, 69 species were identified, with annelids as the dominant group. Eight dominant species were found, including 3 mollusk species in the pasture and 6 species in the control area, comprising 2 mollusk species, 1 echinoderm species, and 3 annelid species. The average abundance and biomass of macrobenthic animals in the pasture were significantly higher than those in the control area. However, Margalef species richness index (d), Pielou evenness index (J'), and Shannon Wiener diversity index (H') values showed little difference between the pasture and the outside. The results of Cluster analysis (CLUSTER) and non-metric multidimensional scaling (NMDS) analysis indicated that relatively low similarity among each station inside and outside the marine ranch. The AMBI and m-AMBI analyses revealed that the overall pollution disturbance in the studied water area was relatively small, indicating good benthic ecological health. Combined with historical data, the analysis revealed a significant increase in species abundance and biomass of macrobenthic communities in the surveyed area. These results suggest that the development of marine pastures has a certain degree of impact on the growth and development of macrobenthic communities.
, Available online ,
doi: 10.12284/hyxb2024030
Abstract:
Coastal wetlands have important economic and ecological value. Rapid and accurate monitoring of the status of coastal wetlands is of great significance for the protection and management of coastal wetland resources. Due to factors such as the variability of the tide-level changes, similarity of vegetation spectra, and frequent cloud cover, remote sensing monitoring of coastal wetlands faced certain challenges. In this paper, we proposed a multi-technology coupled remote sensing classification method of coastal wetlands that considers tide-level changes and vegetation phenological characteristics. Based on the Google Earth Engine (GEE) platform, the Fmask (Function of mask) algorithm was first performed for cloud testing and cloud removal processing. Then, the S-G (Savitzky-Golay) filtering algorithm was used to reconstruct NDVI time series data and extract vegetation phenological characteristic parameters. In this phase, the random forest algorithm was applied for the classification of four vegetation types namely Phragmites australi (PA), Suaeda salsa (SS), Spartina alterniflora (SA), and Imperata cylindrical (IC). Finally, the Maximum Spectral Index Composite (MSIC) algorithm was used to generate composite images of the highest and lowest tide levels. The tidal flats and seawater were precisely extracted using the Otsu algorithm based on these two composite images. Combining these feature types, the refined remote sensing classification of coastal wetlands was ideally obtained. The results showed that start-of-season time, end-of-season time, length of season, base value, amplitude, and small seasonal integral were the six key vegetation phenological characteristic parameters for distinguishing different types of coastal wetland vegetation. Applying this method to classify coastal wetlands on the Yancheng coast, the overall classification accuracy was 96.50%, and the Kappa coefficient reached 0.957 1. Among the wetland vegetation, the highest user accuracy was 96.59% for SA, followed by PA and SS, and the lowest was 93.55% for IC. Compared with object-oriented methods, our method can extract the complete range of tidal flats, and the overall accuracy is improved by 10.25%, reflecting the potential application of vegetation phenological characteristics in remote sensing monitoring of dynamic changes in coastal wetlands.
Coastal wetlands have important economic and ecological value. Rapid and accurate monitoring of the status of coastal wetlands is of great significance for the protection and management of coastal wetland resources. Due to factors such as the variability of the tide-level changes, similarity of vegetation spectra, and frequent cloud cover, remote sensing monitoring of coastal wetlands faced certain challenges. In this paper, we proposed a multi-technology coupled remote sensing classification method of coastal wetlands that considers tide-level changes and vegetation phenological characteristics. Based on the Google Earth Engine (GEE) platform, the Fmask (Function of mask) algorithm was first performed for cloud testing and cloud removal processing. Then, the S-G (Savitzky-Golay) filtering algorithm was used to reconstruct NDVI time series data and extract vegetation phenological characteristic parameters. In this phase, the random forest algorithm was applied for the classification of four vegetation types namely Phragmites australi (PA), Suaeda salsa (SS), Spartina alterniflora (SA), and Imperata cylindrical (IC). Finally, the Maximum Spectral Index Composite (MSIC) algorithm was used to generate composite images of the highest and lowest tide levels. The tidal flats and seawater were precisely extracted using the Otsu algorithm based on these two composite images. Combining these feature types, the refined remote sensing classification of coastal wetlands was ideally obtained. The results showed that start-of-season time, end-of-season time, length of season, base value, amplitude, and small seasonal integral were the six key vegetation phenological characteristic parameters for distinguishing different types of coastal wetland vegetation. Applying this method to classify coastal wetlands on the Yancheng coast, the overall classification accuracy was 96.50%, and the Kappa coefficient reached 0.957 1. Among the wetland vegetation, the highest user accuracy was 96.59% for SA, followed by PA and SS, and the lowest was 93.55% for IC. Compared with object-oriented methods, our method can extract the complete range of tidal flats, and the overall accuracy is improved by 10.25%, reflecting the potential application of vegetation phenological characteristics in remote sensing monitoring of dynamic changes in coastal wetlands.
, Available online
Abstract:
As a national key construction sea area, the trend of offshore wind power construction in the Jiangsu sea area towards the open sea is the main trend of future development. The open sea areas have more surge components, and the wave spectrum often appears in the form of bimodal spectrum. Therefore, the wave characteristics of bimodal spectrum waves need further in-depth research to provide reference basis for offshore construction. Based on the observation data of the buoy station throughout 2018, 1223 bimodal spectral data were obtained through outlier testing and bimodal spectral identification. The bimodal spectral characteristics of waves in the Jiangsu sea area were studied, and different typical bimodal spectral types were compared. The fitting of the measured bimodal spectra was carried out, and the corrected spectral width parameters were proposed. The dependency relationship between the correction coefficient, peak rise factor, and spectral width parameters was explored, and the bimodal spectral fitting expression was obtained. The results indicate that the Ochi Hubble spectrum proposed based on the North Atlantic sea area and the Torsethaugen spectrum proposed based on the Norwegian sea area are not applicable to the bimodal spectrum type in the Jiangsu sea area. The bimodal JONSWAP fitting spectrum proposed in this paper has adaptability and can scientifically and reasonably describe the bimodal spectrum in the Jiangsu sea area, and is widely applied to different wind and terrain conditions in the sea area.
As a national key construction sea area, the trend of offshore wind power construction in the Jiangsu sea area towards the open sea is the main trend of future development. The open sea areas have more surge components, and the wave spectrum often appears in the form of bimodal spectrum. Therefore, the wave characteristics of bimodal spectrum waves need further in-depth research to provide reference basis for offshore construction. Based on the observation data of the buoy station throughout 2018, 1223 bimodal spectral data were obtained through outlier testing and bimodal spectral identification. The bimodal spectral characteristics of waves in the Jiangsu sea area were studied, and different typical bimodal spectral types were compared. The fitting of the measured bimodal spectra was carried out, and the corrected spectral width parameters were proposed. The dependency relationship between the correction coefficient, peak rise factor, and spectral width parameters was explored, and the bimodal spectral fitting expression was obtained. The results indicate that the Ochi Hubble spectrum proposed based on the North Atlantic sea area and the Torsethaugen spectrum proposed based on the Norwegian sea area are not applicable to the bimodal spectrum type in the Jiangsu sea area. The bimodal JONSWAP fitting spectrum proposed in this paper has adaptability and can scientifically and reasonably describe the bimodal spectrum in the Jiangsu sea area, and is widely applied to different wind and terrain conditions in the sea area.
, Available online
Abstract:
Based on the non-hydrostatic model SWASH, a numerical wave flume was established to systematically investigate the hydrodynamic characteristics of the interaction between waves, mangroves, and vertical sea dikes through a comparative experiment with and without mangroves. The study analyzed the influence of factors such as wave steepness, relative water depth, Ursell number, mangrove length, density, and characteristic diameter on the wave height in front of the sea dike and the maximum wave pressure on the windward side of the sea dike. The results indicate that in the absence of mangroves, the Goda formula cannot accurately estimate the impact load on the vertical sea dike. In a numerical experiment with a model scale of 1:10, a 2-meter wide mangroves in front of the dike was observed to reduce wave height by 6% to 45% and wave pressure by 11% to 74%. However, in conditions with relatively large wave heights and smaller characteristic parameters of the mangrove, an increase in the wave height in front of the dike by approximately 4% to 26% was noted. In the hydraulic conditions considered in this study, the maximum wave pressure decreased by 58% to 93% with a decrease in wave steepness, by 42% to 72% with an increase in relative water depth, and by 87% to 96% with a decrease in the Ursell number. The attenuation rates of wave height and wave pressure in front of the dike non-linearly increased with the increase in the width, density, and characteristic diameter of the mangroves. These findings provide a scientific basis for a deeper understanding of the wave-damping effects of mangroves, as well as for the design and planning of coastal protection projects combining mangrove ecosystems with sea dikes.
Based on the non-hydrostatic model SWASH, a numerical wave flume was established to systematically investigate the hydrodynamic characteristics of the interaction between waves, mangroves, and vertical sea dikes through a comparative experiment with and without mangroves. The study analyzed the influence of factors such as wave steepness, relative water depth, Ursell number, mangrove length, density, and characteristic diameter on the wave height in front of the sea dike and the maximum wave pressure on the windward side of the sea dike. The results indicate that in the absence of mangroves, the Goda formula cannot accurately estimate the impact load on the vertical sea dike. In a numerical experiment with a model scale of 1:10, a 2-meter wide mangroves in front of the dike was observed to reduce wave height by 6% to 45% and wave pressure by 11% to 74%. However, in conditions with relatively large wave heights and smaller characteristic parameters of the mangrove, an increase in the wave height in front of the dike by approximately 4% to 26% was noted. In the hydraulic conditions considered in this study, the maximum wave pressure decreased by 58% to 93% with a decrease in wave steepness, by 42% to 72% with an increase in relative water depth, and by 87% to 96% with a decrease in the Ursell number. The attenuation rates of wave height and wave pressure in front of the dike non-linearly increased with the increase in the width, density, and characteristic diameter of the mangroves. These findings provide a scientific basis for a deeper understanding of the wave-damping effects of mangroves, as well as for the design and planning of coastal protection projects combining mangrove ecosystems with sea dikes.
, 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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2024, 46(1): 1-11.
doi: 10.12284/hyxb2024002
Abstract:
Study on the coral reef canopy hydrodynamics not only provides guidance for the health of coral reef ecosystem and the ecological restoration project, but also supports the decision-making process for the reef coast hazard prevention and mitigation under extreme wave events such as the typhoons. Meanwhile, it also has significant value for predicting the sediment transport over the reef and the reef coast evolution. This paper reviews the state-of-the-art research on reef canopy hydrodynamics, and systematically summarize the research progress from three aspects: the flows inside and outside of reef canopy, the characteristics of canopy resistance as well as the simulation of canopy resistance. This paper finally proposes the further research directions as follows: future study can focus on the hydrodynamics under more severe wave condition or under combined action of wave and current. It should also fully consider the anisotropy of canopy skeleton. Moreover, it can solve the Navier-Stokes equations directly to reproduce the finer flow field at the canopy scale.
Study on the coral reef canopy hydrodynamics not only provides guidance for the health of coral reef ecosystem and the ecological restoration project, but also supports the decision-making process for the reef coast hazard prevention and mitigation under extreme wave events such as the typhoons. Meanwhile, it also has significant value for predicting the sediment transport over the reef and the reef coast evolution. This paper reviews the state-of-the-art research on reef canopy hydrodynamics, and systematically summarize the research progress from three aspects: the flows inside and outside of reef canopy, the characteristics of canopy resistance as well as the simulation of canopy resistance. This paper finally proposes the further research directions as follows: future study can focus on the hydrodynamics under more severe wave condition or under combined action of wave and current. It should also fully consider the anisotropy of canopy skeleton. Moreover, it can solve the Navier-Stokes equations directly to reproduce the finer flow field at the canopy scale.
2024, 46(1): 12-26.
doi: 10.12284/hyxb2024024
Abstract:
Beach is a common and vulnerable coastal ecosystem with huge ecological service functions. Due to the multiple impacts of climate change and human activities, beach ecosystem has been seriously damaged. Beach nourishment is an effective approach to prevent coastal erosion and improve the beach environment by using sand replenishment to restore beach morphology. Previous nourishments have often neglected the impacts on beach ecosystem. Many studies show that beach nourishment have multifaceted, multi-scale and complex impacts on beach ecosystem. Based on reviewing previous researches, the compositions, characteristics and functions of beach ecosystem are summarized. The basic characteristics of beach ecological damage, the impact process and mechanism of beach nourishment on beach ecosystem at various scales are analyzed. Then, some adaptive measures for beach nourishment are suggested from the perspective of reducing negative ecological impacts, which would support coastal management and sustainable utilization of beach.
Beach is a common and vulnerable coastal ecosystem with huge ecological service functions. Due to the multiple impacts of climate change and human activities, beach ecosystem has been seriously damaged. Beach nourishment is an effective approach to prevent coastal erosion and improve the beach environment by using sand replenishment to restore beach morphology. Previous nourishments have often neglected the impacts on beach ecosystem. Many studies show that beach nourishment have multifaceted, multi-scale and complex impacts on beach ecosystem. Based on reviewing previous researches, the compositions, characteristics and functions of beach ecosystem are summarized. The basic characteristics of beach ecological damage, the impact process and mechanism of beach nourishment on beach ecosystem at various scales are analyzed. Then, some adaptive measures for beach nourishment are suggested from the perspective of reducing negative ecological impacts, which would support coastal management and sustainable utilization of beach.
2024, 46(1): 101-110.
doi: 10.12284/hyxb2024005
Abstract:
To study the hydrodynamic performance of an oscillating-water-column (OWC) wave energy converter in a real sea, a two-dimensional nonlinear numerical model of the interaction between irregular waves and a land-based OWC device is developed based on the potential flow theory and the high-order boundary element method (HOBEM) in this paper. The irregular waves are generated based on the JONSWAP spectrum. The viscous damping is introduced on the water surface boundary conditions inside the air chamber to consider the energy dissipation due to water viscosity. And physical modeling experiments are carried out in the wave-current flume at Dalian University of Technology to validate the numerical model. It is found that the OWC hydrodynamic efficiency under irregular waves is reduced in comparison with that under regular waves, especially in the low-frequency wave region where the efficiency difference is the largest. The frequency corresponding to the peak efficiency under the action of irregular waves is larger than that under regular waves. The dimensionless surface elevation inside the chamber decreases, while the dimensionless air pressure inside the chamber increases with the significant wave heights. The OWC hydrodynamic efficiency is less affected by the significant wave height. The frequency corresponding to the peak efficiency is not dependent on wave nonlinearity. This work can provide a reference for the design of OWCs.
To study the hydrodynamic performance of an oscillating-water-column (OWC) wave energy converter in a real sea, a two-dimensional nonlinear numerical model of the interaction between irregular waves and a land-based OWC device is developed based on the potential flow theory and the high-order boundary element method (HOBEM) in this paper. The irregular waves are generated based on the JONSWAP spectrum. The viscous damping is introduced on the water surface boundary conditions inside the air chamber to consider the energy dissipation due to water viscosity. And physical modeling experiments are carried out in the wave-current flume at Dalian University of Technology to validate the numerical model. It is found that the OWC hydrodynamic efficiency under irregular waves is reduced in comparison with that under regular waves, especially in the low-frequency wave region where the efficiency difference is the largest. The frequency corresponding to the peak efficiency under the action of irregular waves is larger than that under regular waves. The dimensionless surface elevation inside the chamber decreases, while the dimensionless air pressure inside the chamber increases with the significant wave heights. The OWC hydrodynamic efficiency is less affected by the significant wave height. The frequency corresponding to the peak efficiency is not dependent on wave nonlinearity. This work can provide a reference for the design of OWCs.
2024, 46(1): 27-38.
doi: 10.12284/hyxb2024070
Abstract:
Based on the high-resolution oceanic numerical model product of MITgcm with a resolution of (1/48)°, the geostrophic balanced motion and unbalanced wave motion are decomposed via the frequency-wavenumber spectrum analysis method to analyze the distribution of submesoscale characteristics and diagnose the main factors affecting their seasonal variations in the Agulhas current system. The results show that the submesoscale processes in the Agulhas current system have a significant seasonal distribution with strong features in winter but weak features in summer. The mixed layer baroclinic instability is the main reason affecting the submesoscale seasonal differences in the area. In addition, the geostrophic balanced motions are predominant in the submesoscale process in the regions with stronger eddy kinetic energy (EKE) and have no obvious seasonality. For the regions with weaker EKE, the balanced and unbalanced geostrophic motions show significant seasonality, where the local mixing layer shallowness is responsible for the increase of the unbalanced kinetic energy in summer. Our analysis helps to further clarify the characteristics of submesoscale seasonal variation and its primary factors in the Agulhas current system. The effective separation of geostrophic balanced and unbalanced motion enhances our understanding of energy transformation between multiscale processes in the ocean.
Based on the high-resolution oceanic numerical model product of MITgcm with a resolution of (1/48)°, the geostrophic balanced motion and unbalanced wave motion are decomposed via the frequency-wavenumber spectrum analysis method to analyze the distribution of submesoscale characteristics and diagnose the main factors affecting their seasonal variations in the Agulhas current system. The results show that the submesoscale processes in the Agulhas current system have a significant seasonal distribution with strong features in winter but weak features in summer. The mixed layer baroclinic instability is the main reason affecting the submesoscale seasonal differences in the area. In addition, the geostrophic balanced motions are predominant in the submesoscale process in the regions with stronger eddy kinetic energy (EKE) and have no obvious seasonality. For the regions with weaker EKE, the balanced and unbalanced geostrophic motions show significant seasonality, where the local mixing layer shallowness is responsible for the increase of the unbalanced kinetic energy in summer. Our analysis helps to further clarify the characteristics of submesoscale seasonal variation and its primary factors in the Agulhas current system. The effective separation of geostrophic balanced and unbalanced motion enhances our understanding of energy transformation between multiscale processes in the ocean.
2024, 46(1): 39-52.
doi: 10.12284/hyxb2024018
Abstract:
The Sardinops melanostictus and the Scomber japonicus are important economic species in the northwestn Pacific Ocean, and exploring the correlation between their habitat changes is conducive to the rational development and management of fishery resources. This study utilizes fishery data of Sardinops melanostictus and Scomber japonicus in the northwestern Pacific Ocean from June to November between 2017 and 2021. By incorporating three key environmental variables, namely sea surface temperature, sea surface height, and chlorophyll a mass concentration, habitat models with different weights are constructed. The models are then validated using fishery data from 2021. The optimal models are selected to predict the most suitable habitat distribution of Sardinops melanostictus and Scomber japonicus under different El Niño-Southern Oscillation (ENSO) events. The study analyzes the differences and synchronicity in the spatial and temporal distribution of the most suitable habitat between the two species under different ENSO events. The results indicate that the suitable habitat area of Sardinops melanostictus (above 15%) was higher than that of Scomber japonicus (less than 6%) under different ENSO events; however, the growth rate of the most suitable habitat area for Sardinops melanostictus under La Niña events is higher than that of El Niño events. The former has a growth rate of 0.197 and the latter has a growth rate of 0.123, on the contrary, the growth rate of Scomber japonicus under the La Niña event is lower than that of El Niño event, the former has a growth rate of 1.114 and the latter has a growth rate of 2.082; additionally, when the distribution locations of Sardinops melanostictus and Scomber japonicus are close to each other, it promotes favorable conditions for their habitats. On the other hand, when the distribution locations are far apart, it somewhat inhibits the increase in the suitable habitat area for Scomber japonicus. The co-variation of suitable habitat areas for Sardinops melanostictus and Scomber japonicus under different ENSO events may be related to their interspecies relationship (competition/predation-prey) and the distribution of ocean currents in the northwestern Pacific Ocean.
The Sardinops melanostictus and the Scomber japonicus are important economic species in the northwestn Pacific Ocean, and exploring the correlation between their habitat changes is conducive to the rational development and management of fishery resources. This study utilizes fishery data of Sardinops melanostictus and Scomber japonicus in the northwestern Pacific Ocean from June to November between 2017 and 2021. By incorporating three key environmental variables, namely sea surface temperature, sea surface height, and chlorophyll a mass concentration, habitat models with different weights are constructed. The models are then validated using fishery data from 2021. The optimal models are selected to predict the most suitable habitat distribution of Sardinops melanostictus and Scomber japonicus under different El Niño-Southern Oscillation (ENSO) events. The study analyzes the differences and synchronicity in the spatial and temporal distribution of the most suitable habitat between the two species under different ENSO events. The results indicate that the suitable habitat area of Sardinops melanostictus (above 15%) was higher than that of Scomber japonicus (less than 6%) under different ENSO events; however, the growth rate of the most suitable habitat area for Sardinops melanostictus under La Niña events is higher than that of El Niño events. The former has a growth rate of 0.197 and the latter has a growth rate of 0.123, on the contrary, the growth rate of Scomber japonicus under the La Niña event is lower than that of El Niño event, the former has a growth rate of 1.114 and the latter has a growth rate of 2.082; additionally, when the distribution locations of Sardinops melanostictus and Scomber japonicus are close to each other, it promotes favorable conditions for their habitats. On the other hand, when the distribution locations are far apart, it somewhat inhibits the increase in the suitable habitat area for Scomber japonicus. The co-variation of suitable habitat areas for Sardinops melanostictus and Scomber japonicus under different ENSO events may be related to their interspecies relationship (competition/predation-prey) and the distribution of ocean currents in the northwestern Pacific Ocean.
2024, 46(1): 53-63.
doi: 10.12284/hyxb2024016
Abstract:
Based on the data from 56 acoustic survey sections in the southwestern Indian Ocean from 2011 to 2020, a total of 201 diel vertical migration were observed. The characteristics of diel vertical migration of the deep scattering layer and its spatiotemporal differences were analyzed. The research results show that the deep scattering layer in the southwestern India Ocean exhibits a stratification phenomenon, with the first scattering layer located in the shallow water layer below 200 m. The average depth of its nautical area scattering coefficient (NASC) peak is (58.66 ± 24.63) m, and there is a significant difference between summer and winter (p < 0.001); the second scattering layer is located in the water layer between 400 m and 700 m, with an average depth of (589.02 ± 66.33) m for its NASC peak. There is no significant difference between summer and winter (p = 0.51). The average time for the scattering layer to migrate upwards is 16:20, the average time for the end of migration is 18:31, and the average migration rate is (5.28 ± 1.53) cm/s; the average time for the scattering layer to start migrating downwards is 4:38, and the average time for the end of migration is 6:52. The average migration rate is (5.56 ± 2.13) cm/s. As latitude increases, the start time of downward migration become later and the migration rate slows down; as the longitude increases, the migration rate of the scattering layer also slows down, and there is a significant difference between different longitude sea areas (p < 0.001). Analysis suggests that studying the seasonal changes in the physical and chemical environment of the sea area, as well as the different life cycle stages of organisms in the scattering layer, are the main reasons for the spatiotemporal differences in the vertical structure and diurnal vertical migration characteristics of the scattering layer. They are of great significance in explaining the diurnal vertical migration behavior of tuna and indicating the distribution of tuna fishing grounds.
Based on the data from 56 acoustic survey sections in the southwestern Indian Ocean from 2011 to 2020, a total of 201 diel vertical migration were observed. The characteristics of diel vertical migration of the deep scattering layer and its spatiotemporal differences were analyzed. The research results show that the deep scattering layer in the southwestern India Ocean exhibits a stratification phenomenon, with the first scattering layer located in the shallow water layer below 200 m. The average depth of its nautical area scattering coefficient (NASC) peak is (58.66 ± 24.63) m, and there is a significant difference between summer and winter (p < 0.001); the second scattering layer is located in the water layer between 400 m and 700 m, with an average depth of (589.02 ± 66.33) m for its NASC peak. There is no significant difference between summer and winter (p = 0.51). The average time for the scattering layer to migrate upwards is 16:20, the average time for the end of migration is 18:31, and the average migration rate is (5.28 ± 1.53) cm/s; the average time for the scattering layer to start migrating downwards is 4:38, and the average time for the end of migration is 6:52. The average migration rate is (5.56 ± 2.13) cm/s. As latitude increases, the start time of downward migration become later and the migration rate slows down; as the longitude increases, the migration rate of the scattering layer also slows down, and there is a significant difference between different longitude sea areas (p < 0.001). Analysis suggests that studying the seasonal changes in the physical and chemical environment of the sea area, as well as the different life cycle stages of organisms in the scattering layer, are the main reasons for the spatiotemporal differences in the vertical structure and diurnal vertical migration characteristics of the scattering layer. They are of great significance in explaining the diurnal vertical migration behavior of tuna and indicating the distribution of tuna fishing grounds.
2024, 46(1): 64-76.
doi: 10.12284/hyxb2024020
Abstract:
The concept of ecosystem-based fisheries management has been widely recognized, but it’s application in the construction of marine ranch is still very rare. In this study, based on the data from a bottom trawl survey of fishery resources conducted in the waters of Wuzhizhou Island from 2020 to 2021, a marine ranch fish community size-spectrum model (SSM) was built, which reflects the complex structure of food webs and interspecies interactions in marine ranch, to assess the impacts of fishing on the fish community in marine ranch. The study analyzed the effects of changes in species-specific fishing death coefficient on fish community by simulating two management strategies (single-species management and multispecies management) and monitored the state of fish community characteristics using five community ecological indicators: the total biomass of the community, the slope of size spectrum, the mean maximum weight, the mean weight, and the large fish index. The results of the single-species management strategy showed that the marine ranch ecosystem of Wuzhizhou Island showed top-down control, and there was a strong regulatory effect of carnivorous fish on plankton-feeding fish. Complex interactions such as competitive predation among different species produce trophic cascade effects after changes in fishing death coefficient. The results of the multispecies management strategy showed that fishing death coefficient of Muraenesox cinereus had the greatest effect on the slope of size spectrum, and that fishing death coefficient of Trachiocephalus myops and Muraenesox cinereus had the greatest effect on fish community biomass and community structure and function. The results of this study have important implications for the conservation and stabilization of fish community, and can help managers to better understand the potential impacts of changes in fishing death coefficient rates on fish communities, so that viable and effective conservation and management strategies can be developed based on the importance of the species to the fishery.
The concept of ecosystem-based fisheries management has been widely recognized, but it’s application in the construction of marine ranch is still very rare. In this study, based on the data from a bottom trawl survey of fishery resources conducted in the waters of Wuzhizhou Island from 2020 to 2021, a marine ranch fish community size-spectrum model (SSM) was built, which reflects the complex structure of food webs and interspecies interactions in marine ranch, to assess the impacts of fishing on the fish community in marine ranch. The study analyzed the effects of changes in species-specific fishing death coefficient on fish community by simulating two management strategies (single-species management and multispecies management) and monitored the state of fish community characteristics using five community ecological indicators: the total biomass of the community, the slope of size spectrum, the mean maximum weight, the mean weight, and the large fish index. The results of the single-species management strategy showed that the marine ranch ecosystem of Wuzhizhou Island showed top-down control, and there was a strong regulatory effect of carnivorous fish on plankton-feeding fish. Complex interactions such as competitive predation among different species produce trophic cascade effects after changes in fishing death coefficient. The results of the multispecies management strategy showed that fishing death coefficient of Muraenesox cinereus had the greatest effect on the slope of size spectrum, and that fishing death coefficient of Trachiocephalus myops and Muraenesox cinereus had the greatest effect on fish community biomass and community structure and function. The results of this study have important implications for the conservation and stabilization of fish community, and can help managers to better understand the potential impacts of changes in fishing death coefficient rates on fish communities, so that viable and effective conservation and management strategies can be developed based on the importance of the species to the fishery.
2024, 46(1): 77-87.
doi: 10.12284/hyxb2024012
Abstract:
The semienclosed pyloric caecum of Larimichthys crocea is an ideal organ to perform the host source tracking, as it containes several local bacteria colonized during early development. The alpha diversity, relative abundance of core bacteria and network relationship of the pyloric caecum microbiota in L. crocea from Sansha Bay were analyzed using the Illumina high-throughput sequencing. Furthermore, the random forest model was used to predict the population source (the wild population or the farmed population). The results showed that the farmed fish had more unique OUT and higher alpha diversity than the wild one. The wild and farmed fish significantly differed in the relative abundance of dominant bacteria (Proteobacteria, Firmicutes, Bacteroidota, Actinobacteria and Acidobacteria) (p < 0.05). The result of network analysis showed that the wild fish had higher ratio of negative to positive edges and modularity, but fewer nodes and edges than the farmed fish. Furthermore, a random forest classification prediction model with the accuracy of 92.31%, the Kappa coefficient of 0.8452, and an area under the ROC curve of 0.952 4 was constructed. Using this prediction model, the accuracy of source identification for the wild and farmed fish was 91.67% and 92.86%, respectively. Overall, the structure of microbial communities in the pyloric caecum of L. crocea was different between the wild and farmed populations, making it a potential marker for host source tracking. Our findings provide new insights into distinguishing wild and farmed L. crocea.
The semienclosed pyloric caecum of Larimichthys crocea is an ideal organ to perform the host source tracking, as it containes several local bacteria colonized during early development. The alpha diversity, relative abundance of core bacteria and network relationship of the pyloric caecum microbiota in L. crocea from Sansha Bay were analyzed using the Illumina high-throughput sequencing. Furthermore, the random forest model was used to predict the population source (the wild population or the farmed population). The results showed that the farmed fish had more unique OUT and higher alpha diversity than the wild one. The wild and farmed fish significantly differed in the relative abundance of dominant bacteria (Proteobacteria, Firmicutes, Bacteroidota, Actinobacteria and Acidobacteria) (p < 0.05). The result of network analysis showed that the wild fish had higher ratio of negative to positive edges and modularity, but fewer nodes and edges than the farmed fish. Furthermore, a random forest classification prediction model with the accuracy of 92.31%, the Kappa coefficient of 0.8452, and an area under the ROC curve of 0.952 4 was constructed. Using this prediction model, the accuracy of source identification for the wild and farmed fish was 91.67% and 92.86%, respectively. Overall, the structure of microbial communities in the pyloric caecum of L. crocea was different between the wild and farmed populations, making it a potential marker for host source tracking. Our findings provide new insights into distinguishing wild and farmed L. crocea.
2024, 46(1): 88-100.
doi: 10.12284/hyxb2024010
Abstract:
The ocean acidification effect is increasing with the large amount of CO2 emissions. To investigate the effects of future seawater acidification on Ruditapes philippinarum, a control group (pH = 8.1) and acidification group (pH = 7.7, 7.1 and 6.4) were set up for 42 days. The changes in tissue structure, immune and antioxidant enzyme activities of Ruditapes philippinarum under acidification conditions were measured, as well as the effects produced at the molecular level. The results show that when Ruditapes philippinarum are placed in an acidified seawater environment, gill filament spacing expands with decreasing pH, gill filament cilia adhere, and the pipes and outer epidermal folds of the mantle gradually deepen. The activities of acid phosphatase (ACP) and superoxide dismutase (SOD) in gill tissues show a pattern of decreasing followed by increasing. Alkaline phosphatase (AKP) activities exhibit different trends in each group. Total antioxidant capacity (T-AOC), catalase (CAT), and lysozyme (LZM) activities show a pattern of increasing followed by decreasing. Glutathione peroxidase (GSH-Px) activities in gill and visceral masses show a continuous increase. LZM activity in the viscera group displays varying trends, while ACP activity shows a decreasing and then increasing pattern. AKP, SOD, and CAT activities exhibited an increasing and then decreasing pattern, while T-AOC activity shows a continuous decrease. Analysis of the transcriptome reveals that the GO functions in gill tissue are mainly enriched in DNA integration, integral components of the membrane, and RNA-directed DNA polymerase activity, among others. The KEGG pathway analysis shows enrichment in the phagosome pathway and pathways related to protein processing in the endoplasmic reticulum. The acidification of seawater caused varying degrees of damage to the tissues of Ruditapes philippinarum, disrupting its internal environmental homeostasis and altering metabolic levels and immune-related gene expression, and led to an increased risk of disease and even death in Ruditapes philippinarum.
The ocean acidification effect is increasing with the large amount of CO2 emissions. To investigate the effects of future seawater acidification on Ruditapes philippinarum, a control group (pH = 8.1) and acidification group (pH = 7.7, 7.1 and 6.4) were set up for 42 days. The changes in tissue structure, immune and antioxidant enzyme activities of Ruditapes philippinarum under acidification conditions were measured, as well as the effects produced at the molecular level. The results show that when Ruditapes philippinarum are placed in an acidified seawater environment, gill filament spacing expands with decreasing pH, gill filament cilia adhere, and the pipes and outer epidermal folds of the mantle gradually deepen. The activities of acid phosphatase (ACP) and superoxide dismutase (SOD) in gill tissues show a pattern of decreasing followed by increasing. Alkaline phosphatase (AKP) activities exhibit different trends in each group. Total antioxidant capacity (T-AOC), catalase (CAT), and lysozyme (LZM) activities show a pattern of increasing followed by decreasing. Glutathione peroxidase (GSH-Px) activities in gill and visceral masses show a continuous increase. LZM activity in the viscera group displays varying trends, while ACP activity shows a decreasing and then increasing pattern. AKP, SOD, and CAT activities exhibited an increasing and then decreasing pattern, while T-AOC activity shows a continuous decrease. Analysis of the transcriptome reveals that the GO functions in gill tissue are mainly enriched in DNA integration, integral components of the membrane, and RNA-directed DNA polymerase activity, among others. The KEGG pathway analysis shows enrichment in the phagosome pathway and pathways related to protein processing in the endoplasmic reticulum. The acidification of seawater caused varying degrees of damage to the tissues of Ruditapes philippinarum, disrupting its internal environmental homeostasis and altering metabolic levels and immune-related gene expression, and led to an increased risk of disease and even death in Ruditapes philippinarum.
2024, 46(1): 121-130.
doi: 10.12284/hyxb2024022
Abstract:
Based on the comprehensive fishery survey in the Chongming Island adjacent waters in November 2020, January 2021, April 2021, and August 2021, we used an open-source program Rpath to build a mass balance model containing 22 functional groups for this area. The ecosystem structure and characteristics in this sea area were then studied. Results showed that the trophic level for these 18 functional groups ranged from 1 to 4.32, with the highest trophic level of bottom carnivorous fish. The ecological transfer efficiency of small benthic organisms is the lowest (0.01), suggesting a bottleneck in their energy transfer to higher trophic levels and indicated it was the bottleneck to limit the energy transfer in the benthic food chain. The analysis of the overall characteristics of the ecosystem shows that the total system throughput of the Chongming Island adjacent waters ecosystem was 2 909.42 t/(km2·a), which was lower than that of the nearby marine ecosystem. Phytoplankton contributes 60% of the energy to the total primary productivity of the ecosystem and was the main nutrient source of this ecosystem. The total primary production/total respiration is 1.99 and the system omnivorous index is 0.18. This indicate that the Chongming Island adjacent waters ecosystem has low maturity, simple trophic interaction, and low recovery ability after disturbance. Sensitivity analysis showed that functional group biomass was the main index that affected the accuracy of ecosystem model output. The results of this study can provide a reference for the evaluation of the effect of the Changjiang River fishing ban.
Based on the comprehensive fishery survey in the Chongming Island adjacent waters in November 2020, January 2021, April 2021, and August 2021, we used an open-source program Rpath to build a mass balance model containing 22 functional groups for this area. The ecosystem structure and characteristics in this sea area were then studied. Results showed that the trophic level for these 18 functional groups ranged from 1 to 4.32, with the highest trophic level of bottom carnivorous fish. The ecological transfer efficiency of small benthic organisms is the lowest (0.01), suggesting a bottleneck in their energy transfer to higher trophic levels and indicated it was the bottleneck to limit the energy transfer in the benthic food chain. The analysis of the overall characteristics of the ecosystem shows that the total system throughput of the Chongming Island adjacent waters ecosystem was 2 909.42 t/(km2·a), which was lower than that of the nearby marine ecosystem. Phytoplankton contributes 60% of the energy to the total primary productivity of the ecosystem and was the main nutrient source of this ecosystem. The total primary production/total respiration is 1.99 and the system omnivorous index is 0.18. This indicate that the Chongming Island adjacent waters ecosystem has low maturity, simple trophic interaction, and low recovery ability after disturbance. Sensitivity analysis showed that functional group biomass was the main index that affected the accuracy of ecosystem model output. The results of this study can provide a reference for the evaluation of the effect of the Changjiang River fishing ban.
2024, 46(1): 111-120.
doi: 10.12284/hyxb2024006
Abstract:
Manganese (Mn) is an essential trace element for the marine ecosystem. As the transitional zone between rivers and oceans, estuaries have a significant effect on dissolved Mn and its terrigenous input. In this study, the distribution of dissolved Mn, investigated in the surface water of Changjiang River Estuary and its adjacent area during September 2019 (autumn), March 2021 (spring) and July 2021 (summer), was analyzed by automatic solid phase extraction and inductively coupled plasma mass spectrometry. The results indicated that the average concentration and estuarine behaviors of dissolved Mn showed seasonal variations between the three cruises: the maximum average concentration occurred in summer and dissolved Mn was removed firstly and then added with the increase of salinity; the medium average concentration occurred in autumn and dissolved Mn was mainly removed with the increase of salinity; the minimum average concentration occurred in spring and dissloved Mn was mainly conservative with the increase of salinity. The results of significance test indicated that only in the season when the fresh water had high concentrations, dissloved Mn carried by the Changjiang River had significant influence on the distribution of dissolved Mn in the Changjiang River Estuary and its adjacent area; the distribution of dissolved Mn was co-dominated by a variety of biogeochemical processes in the season when the concentrations were low in the fresh water. The high suspended particulate matter concentrations were the important factor of the removal of dissolved Mn in the Changjiang Estuary’s water with medium-low salinity. And the addition mechanism of dissolved Mn in water with high salinity needs further vestigation.
Manganese (Mn) is an essential trace element for the marine ecosystem. As the transitional zone between rivers and oceans, estuaries have a significant effect on dissolved Mn and its terrigenous input. In this study, the distribution of dissolved Mn, investigated in the surface water of Changjiang River Estuary and its adjacent area during September 2019 (autumn), March 2021 (spring) and July 2021 (summer), was analyzed by automatic solid phase extraction and inductively coupled plasma mass spectrometry. The results indicated that the average concentration and estuarine behaviors of dissolved Mn showed seasonal variations between the three cruises: the maximum average concentration occurred in summer and dissolved Mn was removed firstly and then added with the increase of salinity; the medium average concentration occurred in autumn and dissolved Mn was mainly removed with the increase of salinity; the minimum average concentration occurred in spring and dissloved Mn was mainly conservative with the increase of salinity. The results of significance test indicated that only in the season when the fresh water had high concentrations, dissloved Mn carried by the Changjiang River had significant influence on the distribution of dissolved Mn in the Changjiang River Estuary and its adjacent area; the distribution of dissolved Mn was co-dominated by a variety of biogeochemical processes in the season when the concentrations were low in the fresh water. The high suspended particulate matter concentrations were the important factor of the removal of dissolved Mn in the Changjiang Estuary’s water with medium-low salinity. And the addition mechanism of dissolved Mn in water with high salinity needs further vestigation.
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