A quarterly study of mesozooplankton community structure and environmental variables in the Hangzhou Bay was conducted to examine the response of mesozooplankton community to the variation of water mass and environmen...A quarterly study of mesozooplankton community structure and environmental variables in the Hangzhou Bay was conducted to examine the response of mesozooplankton community to the variation of water mass and environmental condition. The southeast coast of China is a typical region under the intensive influence of Asia monsoon and freshwater discharge from rivers. The water mass and environmental condition of the Hangzhou Bay, which were influenced by the interaction of currents, freshwater discharge of the Qiantang River and Changjiang River Plume, showed significant seasonal variation. Our results showed that both biomass and abundance were significantly higher in summer（（247.7±148.8） mg/m^3 and（350.9±215.6） ind./m^3, respectively）than those in other seasons. Four eco-geographical regions were divided based on the cluster analysis of zooplankton community of the Hangzhou Bay throughout the year, except for winter. Monsoon and the dissolved inorganic nitrogen（DIN） input from freshwater discharge of the Qiantang River and Changjiang River resulted in temporal and spatial variations of environmental gradient in the Hangzhou Bay, which significantly influenced the structure of mesozooplankton community. Redundancy analysis（RDA） indicated that the mesozooplankton community structure was strictly correlated with the DIN gradient, while salinity gradient showed a weak influence in the Hangzhou Bay.展开更多
River plumes are the regions where the most intense river-sea-land interaction occurs, and they are char- acterized by complex material transport and biogeochemical processes. However, due to their highly dy- namic na...River plumes are the regions where the most intense river-sea-land interaction occurs, and they are char- acterized by complex material transport and biogeochemical processes. However, due to their highly dy- namic nature, global river plume areas have not yet been determined for use in synthetic studies of global oceanography. Based on global climatological monthly averaged salinity data from the NOAA World Ocean Atlas 2009 （WOA09）, and monthly averaged salinity contour maps of the East and South China Seas from the Chinese Marine Atlas, we extract the monthly plume areas of major global rivers using a geographic information system （GIS） technique. Only areas with salinities that are three salinity units lower than the average salinity in each ocean are counted. This conservative estimate shows that the minimum and max- imum monthly values of the total plume area of the world＇s 19 largest rivers are 1.72× 106 kin2 in May and 5.38× 106 klTl2 inAugust. The annual mean area of these river plumes （3.72× 106 knl2） takes up approximately 14.2% of the total continental shelves area worldwide （26.15 × 106 km2）. This paper also presents river plume areas for different oceans and latitude zones, and analyzes seasonal variations of the plume areas and their relationships with river discharge. These statistics describing the major global river plume areas can now provide the basic data for the various flux calculations in the marginal seas, and therefore will be of useful for many oceanographic studies.展开更多
Using sea surface salinity(SSS)observation from the soil moisture active passive(SMAP)mission,we analyzed the spatial distribution and seasonal variation of SSS around Changjiang River(Yangtze River)Estuary for the pe...Using sea surface salinity(SSS)observation from the soil moisture active passive(SMAP)mission,we analyzed the spatial distribution and seasonal variation of SSS around Changjiang River(Yangtze River)Estuary for the period of September 2015 to August 2018.First,we found that the SSS from SMAP is more accurate than soil moisture and ocean salinity(SMOS)mission observation when comparing with the in situ observations.Then,the SSS signature of the Changjiang River freshwater was analyzed using SMAP data and the river discharge data from the Datong hydrological station.The results show that the SSS around the Changjiang River Estuary is significantly lower than that of the open ocean,and shows significant seasonal variation.The minimum value of SSS appears in July and maximum SSS in December.The root mean square difference of daily SSS between SMAP observation and in situ observation is around 3 in both summer and winter,which is much lower than the annual range of SSS variation.In summer,the diffusion direction of the Changjiang River freshwater depicted by SSS from SMAP is consistent with the path of freshwater from in situ observation,suggesting that SMAP observation may be used in coastal seas in monitoring the diffusion and advection of freshwater discharge.展开更多
Based on microstructure measurements from a repeated sampling station southwest of the Jeju Island during summer,we studied the hydrography,pycnocline turbulence,and vertical salt fl ux in the Changjiang Diluted Water...Based on microstructure measurements from a repeated sampling station southwest of the Jeju Island during summer,we studied the hydrography,pycnocline turbulence,and vertical salt fl ux in the Changjiang Diluted Water(CDW).The water column was well stratifi ed with the CDW occupied the surface~20 m.Most of the large turbulent kinetic energy dissipation rate(ε)were found in the bottom boundary layer.Interestingly,intermittent strong turbulence(ε>10^(-6) W/kg)occurred in the pycnocline,which may induce strong mixing events and increase the vertical diff usive salt fl ux at the base of CDW by one order of magnitude.The daily-mean vertical diff usive salt fl ux could reach 4.3(2.1,8.9)×10^(-6) m/s.Both moored velocity measurements and associated wavelet analysis showed the presence of velocity fl uctuations when there was strong pycnocline turbulence.The moderate resolution imaging spectroradiometer(MODIS)satellite images further suggest that the velocity fl uctuations are induced by the prevailing internal solitary waves(ISWs)which are mainly generated at the shelf break of the East China Sea or the topographic features surrounding Jeju Island.The calculated gradient Richardson number denote the occurrence of shear instability in the pycnocline when strong turbulence presents.The presented results have strong implications for the importance of ISWs in infl uencing the vertical diff usion of CDW and changes in other properties.展开更多
Biogeochemical character of dissolved inorganic nitrogen and phosphate at plume front is studied based on the data, which were observed in the Changjiang River Estuary in 1988. The results are as follows: The concentr...Biogeochemical character of dissolved inorganic nitrogen and phosphate at plume front is studied based on the data, which were observed in the Changjiang River Estuary in 1988. The results are as follows: The concentrations of nitrate and phosphate change abruptly -2+4at plume front and halocline. The concentrations of NO and NH are very high at 10~25 -33-4m depth. The vertical circumfluence transports NO and PO , which are released from organisms at the bottom to phytoplankton.展开更多
Based on field hydrological,microstructural,and shipboard Acoustic Doppler Current Profiler data,we quantified the spatial and temporal variability of turbulent mixing in the near-field Changjiang(Yangtze)River plume....Based on field hydrological,microstructural,and shipboard Acoustic Doppler Current Profiler data,we quantified the spatial and temporal variability of turbulent mixing in the near-field Changjiang(Yangtze)River plume.The surface dissipation rate(ε)changed by three orders of magnitude from near-field(10^-4 W/kg)to far-field(10^-7 W/kg)plumes,indicating a decrease with distance from the river mouth.Below the river plume,εchanged with depth to 10^-8 W/kg,and increased to 10^-6 W/kg at the layer where the Taiwan Warm Current(TWC)intruded.Thus,εin the near-field plume showed three layers:surface layer in the river plume,middle layer,and lower TWC layer.In the river plume,the strongestεand turbulent diffusivity(Kz)were greater than 10^-4 W/kg and 10^-2 m^2/s,respectively,during strong ebb tides.A three-orders-of-magnitude change inεand Kz was observed in the tidal cycle.The depth of the halocline changed with tidal cycles,and stratification(N 2)varied by one order of magnitude.Stratification in the TWC layer followed the distribution of the halocline,which is opposite to the dissipation structure.Tidal currents led to intrusion and turbulent mixing in the TWC layer.During ebb tides,εand Kz were as strong as those measured in the river plume,but did not last as long.The structure of the velocity shear was similar to the dissipation rate in both the river plume and TWC layer,whereas the velocity shear in the TWC layer did not match the stratification structure.In the high dissipation rate area,the gradient Richardson number was smaller than the critical value(Ri g<1/4).The Ri g structure was consistent with shear and dissipation distributions,indicating that turbulent mixing in the near-field plume was controlled by a combination of shear induced by the discharged river flow and tidal current.展开更多
Coastal zones are active reactors of continental material including that transported by rivers via a series of microbiota-mediated reactions. Nevertheless, current knowledge of the ecology and functioning of the micro...Coastal zones are active reactors of continental material including that transported by rivers via a series of microbiota-mediated reactions. Nevertheless, current knowledge of the ecology and functioning of the microbiota in coastal areas affected by large riverine inputs remains insufficient on a global scale. Here, an investigation on sediment microbial composition, including taxonomy and metabolic network, as well as their relationship with major benthic reaction substrates, namely carbon, nitrogen, sulphur and phosphorus, was conducted in the continental shelf affected by the spread of the Changjiang River plume. Surface sediment samples(48 samples)were collected during March 2018, obtaining a mean Operational Taxonomic Units(OTUs) number of 3 341.Proteobacteria, Acidobacteria and Actinobacteria were abundant phyla in the studied sediments. Bray-Curtis distance analysis classified the 48 samples into 4 clusters(MG1 to MG4) at the phylum-level. MG1 and MG2 are found near the river mouth, receiving substantial land-derived particles from the Changjiang River runoff.Particle-attached microbes may be settled in these regions and influenced the observed sediment microbial diversity and biomass, e.g., increased Crenarchaeota relative abundance. The relative enrichment of these two groups in heterotrophic microbes further suggests a reliance of benthic microbiota on substrates with terrestrial origin, particularly specialized on processing sulphur-rich substrates. Regions MG3 and MG4 are located in the outer margin of the area affected by the Changjiang River plume, mainly fed by settling pelagic particles from phytoplankton. Compared to MG1 and MG2, a significant increase in the abundance of Thaumarcheota(phylumlevel) and Nitrosopumilus(genus-level) was found in MG3, suggesting nitrogen-related transformations as the key reactions to sustain microbial metabolism in this region. Coupled with the identified variations in the taxonomic composition, significant differences in the keystone taxa between MG1/MG2 and MG3/展开更多
基金China Ocean Mineral Resources Research and Development Association Program under contract No.DY125-14-E-01the Global Change and Air-Sea Interaction Program under contract No.GASI-03-01-03-02+2 种基金the National Natural Science Foundation of China under contract No.41406116the Marine Public Welfare Project of China Program under contract No.201005015the Project of the Chinese Offshore Investigation and Assessment Program under contract Nos 908-ST04-Ⅰand 908-ST04-Ⅱ
文摘A quarterly study of mesozooplankton community structure and environmental variables in the Hangzhou Bay was conducted to examine the response of mesozooplankton community to the variation of water mass and environmental condition. The southeast coast of China is a typical region under the intensive influence of Asia monsoon and freshwater discharge from rivers. The water mass and environmental condition of the Hangzhou Bay, which were influenced by the interaction of currents, freshwater discharge of the Qiantang River and Changjiang River Plume, showed significant seasonal variation. Our results showed that both biomass and abundance were significantly higher in summer（（247.7±148.8） mg/m^3 and（350.9±215.6） ind./m^3, respectively）than those in other seasons. Four eco-geographical regions were divided based on the cluster analysis of zooplankton community of the Hangzhou Bay throughout the year, except for winter. Monsoon and the dissolved inorganic nitrogen（DIN） input from freshwater discharge of the Qiantang River and Changjiang River resulted in temporal and spatial variations of environmental gradient in the Hangzhou Bay, which significantly influenced the structure of mesozooplankton community. Redundancy analysis（RDA） indicated that the mesozooplankton community structure was strictly correlated with the DIN gradient, while salinity gradient showed a weak influence in the Hangzhou Bay.
基金The National Basic Research Program of China (973 Program) under contract No. 2009CB421202the Public Science and Technology Research Funds Projects of Ocean under contract No. 200905012+1 种基金the National Natural Science Foundation of China under contract Nos41271378, 40976110 and 40706061the National High Technology Research and Development Program of China (863 Program) under contract No.2007AA092201
文摘River plumes are the regions where the most intense river-sea-land interaction occurs, and they are char- acterized by complex material transport and biogeochemical processes. However, due to their highly dy- namic nature, global river plume areas have not yet been determined for use in synthetic studies of global oceanography. Based on global climatological monthly averaged salinity data from the NOAA World Ocean Atlas 2009 （WOA09）, and monthly averaged salinity contour maps of the East and South China Seas from the Chinese Marine Atlas, we extract the monthly plume areas of major global rivers using a geographic information system （GIS） technique. Only areas with salinities that are three salinity units lower than the average salinity in each ocean are counted. This conservative estimate shows that the minimum and max- imum monthly values of the total plume area of the world＇s 19 largest rivers are 1.72× 106 kin2 in May and 5.38× 106 klTl2 inAugust. The annual mean area of these river plumes （3.72× 106 knl2） takes up approximately 14.2% of the total continental shelves area worldwide （26.15 × 106 km2）. This paper also presents river plume areas for different oceans and latitude zones, and analyzes seasonal variations of the plume areas and their relationships with river discharge. These statistics describing the major global river plume areas can now provide the basic data for the various flux calculations in the marginal seas, and therefore will be of useful for many oceanographic studies.
基金The National Key Research and Development Program of China under contract No.2016YFC1401600the Public Science and Technology Research Fund Projects for Ocean Research under contract No.201505003the 2015 Jiangsu Program of Entrepreneurship and Innovation Group under contract No.2191061503801/002
文摘Using sea surface salinity(SSS)observation from the soil moisture active passive(SMAP)mission,we analyzed the spatial distribution and seasonal variation of SSS around Changjiang River(Yangtze River)Estuary for the period of September 2015 to August 2018.First,we found that the SSS from SMAP is more accurate than soil moisture and ocean salinity(SMOS)mission observation when comparing with the in situ observations.Then,the SSS signature of the Changjiang River freshwater was analyzed using SMAP data and the river discharge data from the Datong hydrological station.The results show that the SSS around the Changjiang River Estuary is significantly lower than that of the open ocean,and shows significant seasonal variation.The minimum value of SSS appears in July and maximum SSS in December.The root mean square difference of daily SSS between SMAP observation and in situ observation is around 3 in both summer and winter,which is much lower than the annual range of SSS variation.In summer,the diffusion direction of the Changjiang River freshwater depicted by SSS from SMAP is consistent with the path of freshwater from in situ observation,suggesting that SMAP observation may be used in coastal seas in monitoring the diffusion and advection of freshwater discharge.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23050502)the National Natural Science Foundation of China(No.41906006)。
文摘Based on microstructure measurements from a repeated sampling station southwest of the Jeju Island during summer,we studied the hydrography,pycnocline turbulence,and vertical salt fl ux in the Changjiang Diluted Water(CDW).The water column was well stratifi ed with the CDW occupied the surface~20 m.Most of the large turbulent kinetic energy dissipation rate(ε)were found in the bottom boundary layer.Interestingly,intermittent strong turbulence(ε>10^(-6) W/kg)occurred in the pycnocline,which may induce strong mixing events and increase the vertical diff usive salt fl ux at the base of CDW by one order of magnitude.The daily-mean vertical diff usive salt fl ux could reach 4.3(2.1,8.9)×10^(-6) m/s.Both moored velocity measurements and associated wavelet analysis showed the presence of velocity fl uctuations when there was strong pycnocline turbulence.The moderate resolution imaging spectroradiometer(MODIS)satellite images further suggest that the velocity fl uctuations are induced by the prevailing internal solitary waves(ISWs)which are mainly generated at the shelf break of the East China Sea or the topographic features surrounding Jeju Island.The calculated gradient Richardson number denote the occurrence of shear instability in the pycnocline when strong turbulence presents.The presented results have strong implications for the importance of ISWs in infl uencing the vertical diff usion of CDW and changes in other properties.
基金We wish to thank the National Natural Science Foundation of China which has offerd us the financial support for this research (No: 49736220).
文摘Biogeochemical character of dissolved inorganic nitrogen and phosphate at plume front is studied based on the data, which were observed in the Changjiang River Estuary in 1988. The results are as follows: The concentrations of nitrate and phosphate change abruptly -2+4at plume front and halocline. The concentrations of NO and NH are very high at 10~25 -33-4m depth. The vertical circumfluence transports NO and PO , which are released from organisms at the bottom to phytoplankton.
基金the National Natural Science Foundation of China(NSFC)(No.41706012)the National Key Research and Development Program of China(No.2017YFC1403401)+1 种基金the National Natural Science Foundation of China(NSFC)Innovative Group Grant(No.41421005),the NSFC-Shandong Joint Fund for Marine Science Research Centers(No.U1406401)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA11020301)。
文摘Based on field hydrological,microstructural,and shipboard Acoustic Doppler Current Profiler data,we quantified the spatial and temporal variability of turbulent mixing in the near-field Changjiang(Yangtze)River plume.The surface dissipation rate(ε)changed by three orders of magnitude from near-field(10^-4 W/kg)to far-field(10^-7 W/kg)plumes,indicating a decrease with distance from the river mouth.Below the river plume,εchanged with depth to 10^-8 W/kg,and increased to 10^-6 W/kg at the layer where the Taiwan Warm Current(TWC)intruded.Thus,εin the near-field plume showed three layers:surface layer in the river plume,middle layer,and lower TWC layer.In the river plume,the strongestεand turbulent diffusivity(Kz)were greater than 10^-4 W/kg and 10^-2 m^2/s,respectively,during strong ebb tides.A three-orders-of-magnitude change inεand Kz was observed in the tidal cycle.The depth of the halocline changed with tidal cycles,and stratification(N 2)varied by one order of magnitude.Stratification in the TWC layer followed the distribution of the halocline,which is opposite to the dissipation structure.Tidal currents led to intrusion and turbulent mixing in the TWC layer.During ebb tides,εand Kz were as strong as those measured in the river plume,but did not last as long.The structure of the velocity shear was similar to the dissipation rate in both the river plume and TWC layer,whereas the velocity shear in the TWC layer did not match the stratification structure.In the high dissipation rate area,the gradient Richardson number was smaller than the critical value(Ri g<1/4).The Ri g structure was consistent with shear and dissipation distributions,indicating that turbulent mixing in the near-field plume was controlled by a combination of shear induced by the discharged river flow and tidal current.
基金The National Natural Science Foundation of China under contract Nos 31800079 and 41530960the Scientific Research Foundation of SKLEC under contract No. 2017RCDW04+1 种基金the Zhengzhou University Startup Foundation under contract No.32210876the China Postdoctoral Science Foundation under contract No. 2021M691018。
文摘Coastal zones are active reactors of continental material including that transported by rivers via a series of microbiota-mediated reactions. Nevertheless, current knowledge of the ecology and functioning of the microbiota in coastal areas affected by large riverine inputs remains insufficient on a global scale. Here, an investigation on sediment microbial composition, including taxonomy and metabolic network, as well as their relationship with major benthic reaction substrates, namely carbon, nitrogen, sulphur and phosphorus, was conducted in the continental shelf affected by the spread of the Changjiang River plume. Surface sediment samples(48 samples)were collected during March 2018, obtaining a mean Operational Taxonomic Units(OTUs) number of 3 341.Proteobacteria, Acidobacteria and Actinobacteria were abundant phyla in the studied sediments. Bray-Curtis distance analysis classified the 48 samples into 4 clusters(MG1 to MG4) at the phylum-level. MG1 and MG2 are found near the river mouth, receiving substantial land-derived particles from the Changjiang River runoff.Particle-attached microbes may be settled in these regions and influenced the observed sediment microbial diversity and biomass, e.g., increased Crenarchaeota relative abundance. The relative enrichment of these two groups in heterotrophic microbes further suggests a reliance of benthic microbiota on substrates with terrestrial origin, particularly specialized on processing sulphur-rich substrates. Regions MG3 and MG4 are located in the outer margin of the area affected by the Changjiang River plume, mainly fed by settling pelagic particles from phytoplankton. Compared to MG1 and MG2, a significant increase in the abundance of Thaumarcheota(phylumlevel) and Nitrosopumilus(genus-level) was found in MG3, suggesting nitrogen-related transformations as the key reactions to sustain microbial metabolism in this region. Coupled with the identified variations in the taxonomic composition, significant differences in the keystone taxa between MG1/MG2 and MG3/
