The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary. This suggests that the area is an emissive source of nitrous oxide. The acetylene inhib...The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary. This suggests that the area is an emissive source of nitrous oxide. The acetylene inhibition technique is employed to evaluate the rates of nitrification, denitrification and nitrate reduction by bacterial activities in the sediments at three sites. The average of nitrification, denitrification and nitrate reduction rates ranges from 0.32 to 2.43, 0.03 to 0.84 and 4.17 to 13.06 mmol/(m2·h), respectively. The ver- tical profiles of the sediments show that the nitrification and denitrification processes mainly take place in the depth from 0 to 4 cm and depend on regional conditions. The rates of nitrification, denitrification and nitrate reduction are dominated by Eh, nitrate and ammoni- um concentrations in sediments and DO in overlay water. There is a coupling between nitrification and denitrification.展开更多
A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pol...A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE ? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water qual展开更多
To investigate organic matter source and reactivity in the Zhujiang River (Pearl River) Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during t...To investigate organic matter source and reactivity in the Zhujiang River (Pearl River) Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during two cruises in July 1999 and July 2000 were measured. The highest POC and PHAA concentration was observed in the waters with maximum Chl a. The spectra distribution, relative content (dry weight in milligram per gram), PHAA-C% POC and other indicators such as the ratios of amino acids vs. amino sugars (AA/AS) and glucosamine vs. galactosamine (Glum/Gal) suggested that particulate amino acids in the water column and sediments in the Zhujiang River Estuary were mainly derived from biogenic processes rather than transported from terrestrial erosion. In inner estuary where high turbidity was often observable, organic matter was mainly contributed by re-suspension of bottom sediments with revealed zooplankton, microbial reworked characteristics, which suggest that these organic matters were relatively 'old'. In the estuarine brackish region, organic matter in water column is mainly contributed by relatively fresh, easily degradable phytoplankton derived organic matter. During physical - biological processes within the eastuary, organic matter derived from phytoplankton was subjected to alteration by zooplankton grazing and bacterial reworking.展开更多
The Zhujiang River Estuary is becoming eutrophic due to the impact of anthropogenic activities in the past decades.To understand nutrient dynamics and fluxes to the Lingdingyang water via four outlets(Humen,Jiaomen,Ho...The Zhujiang River Estuary is becoming eutrophic due to the impact of anthropogenic activities in the past decades.To understand nutrient dynamics and fluxes to the Lingdingyang water via four outlets(Humen,Jiaomen,Hongqimen and Hengmen),we investigated the spatial distribution and seasonal variation of dissolved nutrients in the Zhujiang River Estuary,based on fourteen cruises conducted from March 2015 to October 2017,covering both wet(April to September)and dry(October to March next year)seasons.Our results showed that riverine fluxes of dissolved inorganic nitrogen(DIN)and dissolved silicate(DSi)into the Lingdingyang water through four outlets varied seasonally due to the influence of river discharge,with the highest in spring and the lowest in winter.However,riverine flux of phosphate exhibited little significant seasonal variability.Riverine nutrients into the Lingdingyang water most resulted through Humen Outlet.The estuarine export fluxes of DIN out of the Zhujiang River Estuary derived from a box model were higher than fluxes of riverine nutrients in May,likely due to the influence of local sewage,while lower than riverine flux in August.The export fluxes of phosphate were higher than the fluxes of riverine phosphate in May and August.In contrast,large amounts of DSi were buried in the estuary in May and August.Although excess DIN was delivered into the Zhujiang River Estuary,eutrophication effect was not as severe as expected in the Zhujiang River Estuary,since the light limitation restricted the utilization of nutrients by phytoplankton.展开更多
The contents of total copper, total dissolved copper, particulate copper, and free ion copper in the Zhujiang River Estuary were investigated in July 2002 and January 2003 respectively, and the spatial distribution tr...The contents of total copper, total dissolved copper, particulate copper, and free ion copper in the Zhujiang River Estuary were investigated in July 2002 and January 2003 respectively, and the spatial distribution trend of these species of copper were compared in two cruises. It was found that, in summer, the total copper content in the Zhujiang River Estuary increased with salinity, while the content office ion copper decreased with salinity. However, in winter, the contents of total copper and free ion copper both decreased with salinity. So, it could be concluded that, copper content and speciation in the Zhujiang River Estuary were regulated by other factors than runoffdiffusion such as upwelling current. In order to prove the spatial trend of rice ion copper content in the Zhujiang River Estuary, the cultivation of Dunaliella tertiolecta in waters obtained from sampling stations with different salinities was carried out, and the copper uptake by algae cells was measured then. It was found that, the cells' uptake of copper increased with rice ion copper, not the content of total copper.展开更多
1. PREFACE Lingdingyang is a trumpet estuary. It accepts the runoff of the Dongjiang River, the Beijiang River, the Zhengjiang River and the Liusihe River. It also accepts a part of the runoff of the Xijiang River. It...1. PREFACE Lingdingyang is a trumpet estuary. It accepts the runoff of the Dongjiang River, the Beijiang River, the Zhengjiang River and the Liusihe River. It also accepts a part of the runoff of the Xijiang River. Its mean year runoff is 1.742×10" M^3. In resent ten years, industry and agriculture are developing rapidly in Guangzhou City, Dongguan City, Zhongshan City, Shunde County, Panyu County. Lingdingyang’s pollution is increesing. Water quality of lingdingyang is steadily deteriorated. In order to investigate the situation of water environment of Lingdingyang, we study its static environmental capacity of nitrogen and phosphorus. LANDSAT imageries are used in the study. The concentrations of nitrogen and phosphorous is detected by convention method.展开更多
To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21...To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21°N–23.5°N,111°E–117°E).Samples were collected from 65 stations including one for time-series sampling.A total of 212 phytoplankton taxa were identified from 61 genera belonging to 4 phyla.Among them,122 species identified from 42 genera of Bacillariophyta and 83 species from 15 genera of Pyrrophyta.Chain-forming diatoms dominated the phytoplankton community where Pseudonitzschia delicatissima,Guinardia striata,Thalassionema nitzschioides,and P.pungens comprised about 52%of the total abundance.However,higher cell abundances concentrated on both sides of the estuary,because of low salinity and high nutrients brought by diluted water.In addition,Canonical Correspondence Analysis revealed that salinity and dissolved inorganic nitrogen shaped the species composition in the study area.Furthermore,the Jaccard similarity index showed prevailing high similarity in the distribution of species in low-salinity diluted waters,and the Bray-Curtis similarity depicted distinguished grouping for phytoplankton assemblages along the salinity gradient.However,phytoplankton diel vertical cycles showed maximum abundance occurred at 2:00 am,which was mainly contributed by benthic phytoplankton species Pseudo-nitzschia spp.and T.nitzschioides.展开更多
Chemometric approach based on principal component analysis(PCA) was utilized to examine the spatial variances of environmental and ecological characteristics in the Zhujiang River(Pearl River) Estuary and adjacent...Chemometric approach based on principal component analysis(PCA) was utilized to examine the spatial variances of environmental and ecological characteristics in the Zhujiang River(Pearl River) Estuary and adjacent waters(ZREAW) in the South China Sea. The PCA result shows that the ZREAW can be divided into different zones according to the principal components and geographical locations of the study stations,and indicates that there are distinct regional variances on environmental features and the corresponding phytoplankton biomass and community structures among different areas. The spatial distribution of ecological features was implied to be influenced by various degrees of the different water resources,such as the Pearl River discharges,the coastal current and the oceanic water from the South China Sea. The variation of the biomass maximum zone and the complex impacts on the spatial distributions of phytoplankton biomass and production were also evaluated.展开更多
Real-time observations in the field and numerical simulations(with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum(TM) in the Zhujiang(Pearl R...Real-time observations in the field and numerical simulations(with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum(TM) in the Zhujiang(Pearl River) Estuary(ZE). The spatial distribution pattern of the TM varies with the longitudinal distributions of salinity and suspended sediment concentration(SSC). The SSC is enhanced and the TM is intensified during dry seasons,whereas the center of the TM moves upstream by a distance of 10 km during wet seasons. The formation of the TM is influenced by a complex combination of numerous factors, including tides, river discharges and topography, wherein sediment resuspension and vertical circulation dominate the formations and variability of the TM.展开更多
A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang(Pearl)River Estuary(ZRE)from ...A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang(Pearl)River Estuary(ZRE)from 1971 to 2012.It is shown that,during the wavy period,the large wave-induced bottom stress enhances sediment resuspension,resulting in an increase in the area of suspended sediment concentration(SSC)greater than 100 mg/L by 183.4%.On one hand,in spring tide,the change in shoreline reduces the area of SSC greater than 100 mg/L by 17.8%in the west shoal(WS)but increases the SSC,owing to the closer sediment source to the offshore and the stronger residual current at the Hengmeng(HEM)and Hongqili(HQL)outlets.The eastward Eulerian transport is enhanced in the WS and west channel(WC),resulting in a higher SSC there.The reclamation of Longxue Island(LXI)increases SSC on its east side and east shoal(ES)but decreases the SSC on its west and south sides.Moreover,in the WC,the estuarine turbidity maximum(ETM)is located near the saltwater wedge and moves southward,which is caused by the southward movement of the maximum longitudinal Eulerian transport.In neap tide,the changes are similar but relatively weaker.On the other hand,in spring tide,the change in bathymetry makes the SSC in the WS increase,and the area of SSC greater than 100 mg/L increases by 11.4%and expands eastward and southward,which is caused by the increases in wave-induced bottom stress and eastward Eulerian transport.On the east side of the WC,the eastward Eulerian transport decreases significantly,resulting in a smaller SSC in the middle shoal(MS).In addition,in the WC,the maximum SSC is reduced,which is caused by the smaller wave-induced bottom stress and a significant increase of 109.88%in southward Eulerian transport.The results in neap tide are similar to those in spring tide but with smaller changes,and the sediment transports northward in the WC owing to the northward Eulerian transport and vertical shear transport.This study may provide some references for marine ecological environment security and coastal management in the ZRE and other estuaries worldwide affected by strong human interventions.展开更多
The distributions of estuarine colored dissolved organic matter(CDOM)are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ d...The distributions of estuarine colored dissolved organic matter(CDOM)are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ data from four seasonal cruises,an algorithm is developed to estimate CDOM absorption coefficient at 400nm(aCDOM(400))in the Zhujiang(Pearl River)Estuary(ZJE).The algorithm uses band ratios of Rrs(667)/Rrs(443)and Rrs(748)/Rrs(412).By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite(MODIS/Aqua)data from 2002 to 2014,seasonal climatology aCDOM(400)in the ZJE is calculated.CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography.Along the section vertical to a water depth gradient,the seasonal aCDOM(400)exponentially decreased(y=aebx,b〈0),but with great differences among seasons.Riverine fresh water is the primary source of CDOM in the ZJE.Fulvic acid fraction decreases with increasing salinity.Using developed algorithms,conservative CDOM mixing equation,and river discharge,effective riverine end-member concentration and flux of dissolved organic carbon(DOC)in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data.Both effective riverine end-member DOC concentration and flux are positively related to the river discharge,significantly in summer with R-2 of 0.698 for concentration and 0.965 7 for flux.展开更多
The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determine...The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determined. The method of sequential extraction was used for separating the five bound forms.The main chemical form of the three elements in the sediments of the Zhujiang River and its estuarine zone is the residual one. The exchangeable form exists only in a small fraction.Correlationships between the concentration of a certain form of heavy metals and Eh. pH and salinity were discussed. The principles of geochemistry are used to explain the mechanism of heavy metal transport in the river.It was also found that the distribution rule of the chemical forms of Fe, Al and Mn in sediments in the lower reaches of the Zhujiang River was similar to the one in the lower reaches of the Yamaska River.展开更多
Sea surface temperature (SST) proxies including B/Ca, Mg/Ca, St/Ca, U/Ca and δ180 were analyzed in the skeleton of a Porites coral collected from the Zhujiang River (Pearl River) Estuary (ZRE). These geochemica...Sea surface temperature (SST) proxies including B/Ca, Mg/Ca, St/Ca, U/Ca and δ180 were analyzed in the skeleton of a Porites coral collected from the Zhujiang River (Pearl River) Estuary (ZRE). These geochemical proxies are influenced by river runoff and this area of the northern South China Sea is strongly affected by seasonal freshwater floods. We assessed the robustness of each SST proxy through comparison with the local instrumental SST. Coral St/Ca shows the highest correlation with SST variations (r2=0.59), suggesting St/Ca is the most robust SST proxy. In contrast, coral δ180 (r2=0.46), B/Ca (r2=0.43) and U/Ca (r2=0.41) ratios were only moderately correlated with SST variations, suggesting that they are disturbed by some other factors in addition to SST. The poor correlation (r2=0.27) between SST and Mg/Ca indicates that Mg/Ca in coral skeletons is not a simple function of SST variations. This may ultimately limit the use of Mg/Ca as a coral paleothermometer.展开更多
The performance and integrity of a cassette cross-flow ultrafilter (Pellicon 2, Millipore) are examined with a suite of macromolecules of different molecular masses. The retention coefficient during the cross-flow u...The performance and integrity of a cassette cross-flow ultrafilter (Pellicon 2, Millipore) are examined with a suite of macromolecules of different molecular masses. The retention coefficient during the cross-flow ultrafiltration experiments increases with increasing molecular mass and reaches 90% with 10 kDa dextran in both milli-Q water and ultrafiltered seawater media. Based on a 90% retention coefficient, the molecular mass cut-off for the ultrafiltration membrane is defined at 10 kDa, which is ten times (1 kDa) that rated by the manufacturer. To further validate the accuracy of the laboratory calibration, the samples from the lower Zhujiang River and the Jiulong River Estuary are ultrafiltered with the cassette ultrafiltration membrane and the colloidal organic carbon abundances in these samples are quantified with the ultrafiltration per- meation model based on time series permeation subsamples. The colloidal organic carbon abundances are 5.8%-21.1% in the Jiulong River Estuary and 5.6%-11.0% in the lower Zhujiang River. These are consistent with the reported values for both estuaries as well as with the colloidal organic carbon abundances in ma- rine environments over the coastal and open oceans with 10 kDa cut-off membranes. Therefore, these field data support the laboratory calibration result and indicate the validity of the experimental and quantification procedure adopted. The discrepancy between the nominal molecular mass cut-off and the actual pore size of the ultrafiltration membrane should be of great concern for research in colloidal and nanoparticle biogeochemistry. Careflfl examination of the membrane integrity should be taken during ultrafiltration ex- oeriments in order to avoid misleading molecular mass cut-off information.展开更多
The impacts of the Hong Kong-Zhuhai-Macao Bridge(HKZMB)on suspended sediment content(SSC)were analysed in the Zhujiang River Estuary based on data from HY-1C,which was launched in September 2018 in China,carrying Coas...The impacts of the Hong Kong-Zhuhai-Macao Bridge(HKZMB)on suspended sediment content(SSC)were analysed in the Zhujiang River Estuary based on data from HY-1C,which was launched in September 2018 in China,carrying Coastal Zone Imager(CZI)and Chinese Ocean Color and Temperature Scanner on it.A new SSC inversion model was established based on the relationship between in-situ SSC and the remote sensing reflectance in red and near-infrared bands of CZI image.HY-1C satellite data obtained from October to December 2019 were applied to retrieve SSC in the Zhujiang River Estuary.The results show that SSC around the HKZMB is ranging from 20 mg/L to 95 mg/L.SSC change obviously on two sides of the bridge.During flooding and ebbing period,SSC increases obviously downstream of the bridge.SSC difference between upstream and downstream is ranging from 5 mg/L to 20 mg/L.Currents flowing across the HKZMB,the change trend of SSC in most places upstream and downstream is almost the same that SSC downstream of the bridge is higher than SSC upstream.The tidal currents interact with bridge piers,inducing vortexes downstream,leading the sediment to re-suspend downstream of the bridge piers.Other factors,including seafloor topography and wind,can also contribute to the distribution of SSC in the Zhujiang River Estuary.展开更多
Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes.Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across enviro...Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes.Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across environments.However,empirical leucine-to-carbon conversion factors(e CFs) are seldom determined in situ because of time consuming and little is known on regulating factors for the e CFs.During May 2015 to January 2016,fourteen dilution experiments were conducted,from the Zhujiang(Pearl River) Estuary to the coast of the northern South China Sea,to determine spatiotemporal variability in the e CFs and its potential controlling factors along an environmental gradient.The e CFs showed clear spatial variations with the highest(1.27–1.69(kg C)/(mol Leu)) in low salinity waters(salinity〈15),intermediate(1.03–1.25(kg C)/(mol Leu)) in moderate salinity(salinity of 15–25),and the lowest(0.48–0.85(kg C)/(mol Leu)) in high salinity waters(salinity〉25).Substrate availability was responsible for spatial variability in the e CFs.In the pristine coastal waters,low e CFs was related to substrate limitation and leucine incorporated was respired to maximize the survival rather than bacterial production.Hence,the e CFs measurement was needed for estimating bacterial production accurately in various marine environments.展开更多
基金supported by the Knowledge Innovation Engineering of Chinese Academy of Sciences under contract No.KZCX3-SW-214,KSCX2-SW-132the Natural Science Foundation of Guangdong Province under contract No.032622.
文摘The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary. This suggests that the area is an emissive source of nitrous oxide. The acetylene inhibition technique is employed to evaluate the rates of nitrification, denitrification and nitrate reduction by bacterial activities in the sediments at three sites. The average of nitrification, denitrification and nitrate reduction rates ranges from 0.32 to 2.43, 0.03 to 0.84 and 4.17 to 13.06 mmol/(m2·h), respectively. The ver- tical profiles of the sediments show that the nitrification and denitrification processes mainly take place in the depth from 0 to 4 cm and depend on regional conditions. The rates of nitrification, denitrification and nitrate reduction are dominated by Eh, nitrate and ammoni- um concentrations in sediments and DO in overlay water. There is a coupling between nitrification and denitrification.
文摘A tracer model with random diffusion coupled to the hydrodynamic model for the Zhujiang River Estuary (Pearl River Estuary, PRE) is to examine the effect of circulations on the transport of completely conservative pollutants. It is focused on answering the following questions: (1) What role does the estuarine plume front in the winter play in affecting the pollutants transport and its distribution in the PRE ? (2) What effect do the coastal currents driven by the monsoon have on the pollutants transport? The tracer experiment results show that: (1) the pollutant transport paths strongly depend on the circulation structures and plume frontal dynamics of the PRE and coastal waters; (2) during the summer when a southwesterly monsoon prevails, the pollutants from the four easterly river inlets and those from the bottom layer of offshore stations will greatly influence the water quality in Hong Kong waters, however, the pollutants released from the four westerly river-inlets will seldom affect the water qual
文摘To investigate organic matter source and reactivity in the Zhujiang River (Pearl River) Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during two cruises in July 1999 and July 2000 were measured. The highest POC and PHAA concentration was observed in the waters with maximum Chl a. The spectra distribution, relative content (dry weight in milligram per gram), PHAA-C% POC and other indicators such as the ratios of amino acids vs. amino sugars (AA/AS) and glucosamine vs. galactosamine (Glum/Gal) suggested that particulate amino acids in the water column and sediments in the Zhujiang River Estuary were mainly derived from biogenic processes rather than transported from terrestrial erosion. In inner estuary where high turbidity was often observable, organic matter was mainly contributed by re-suspension of bottom sediments with revealed zooplankton, microbial reworked characteristics, which suggest that these organic matters were relatively 'old'. In the estuarine brackish region, organic matter in water column is mainly contributed by relatively fresh, easily degradable phytoplankton derived organic matter. During physical - biological processes within the eastuary, organic matter derived from phytoplankton was subjected to alteration by zooplankton grazing and bacterial reworking.
基金The Special Project for Marine Economic Development(Six Major Marine Industries)of Guangdong Province under contract No.GDNRC[2020]064the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract Nos GML2019ZD0303,GML2019ZD0305 and GML2019ZD0402+2 种基金the Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences under contract Nos ISEE2019ZR02 and ISEE2019ZR03the National Natural Science Foundation of China under contract Nos 41676075 and 41706085the Department of Science and Technology of Guangdong Province under contract No.2018B030320005。
文摘The Zhujiang River Estuary is becoming eutrophic due to the impact of anthropogenic activities in the past decades.To understand nutrient dynamics and fluxes to the Lingdingyang water via four outlets(Humen,Jiaomen,Hongqimen and Hengmen),we investigated the spatial distribution and seasonal variation of dissolved nutrients in the Zhujiang River Estuary,based on fourteen cruises conducted from March 2015 to October 2017,covering both wet(April to September)and dry(October to March next year)seasons.Our results showed that riverine fluxes of dissolved inorganic nitrogen(DIN)and dissolved silicate(DSi)into the Lingdingyang water through four outlets varied seasonally due to the influence of river discharge,with the highest in spring and the lowest in winter.However,riverine flux of phosphate exhibited little significant seasonal variability.Riverine nutrients into the Lingdingyang water most resulted through Humen Outlet.The estuarine export fluxes of DIN out of the Zhujiang River Estuary derived from a box model were higher than fluxes of riverine nutrients in May,likely due to the influence of local sewage,while lower than riverine flux in August.The export fluxes of phosphate were higher than the fluxes of riverine phosphate in May and August.In contrast,large amounts of DSi were buried in the estuary in May and August.Although excess DIN was delivered into the Zhujiang River Estuary,eutrophication effect was not as severe as expected in the Zhujiang River Estuary,since the light limitation restricted the utilization of nutrients by phytoplankton.
基金This work was supported by the Innovative Program of Chinese Academy of Sciences under contract No.kzcx3-sw-227 to Dr.Chen ShaoyongGuangdong Province Natural Science Fund under contract Nos 021560,04001313+1 种基金the Innovation Program of South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.50601-32 to Long AiminScience and Technology Planning Program under contract No.2004B33201001 to Dr.Yan Wen and Long Aimin.
文摘The contents of total copper, total dissolved copper, particulate copper, and free ion copper in the Zhujiang River Estuary were investigated in July 2002 and January 2003 respectively, and the spatial distribution trend of these species of copper were compared in two cruises. It was found that, in summer, the total copper content in the Zhujiang River Estuary increased with salinity, while the content office ion copper decreased with salinity. However, in winter, the contents of total copper and free ion copper both decreased with salinity. So, it could be concluded that, copper content and speciation in the Zhujiang River Estuary were regulated by other factors than runoffdiffusion such as upwelling current. In order to prove the spatial trend of rice ion copper content in the Zhujiang River Estuary, the cultivation of Dunaliella tertiolecta in waters obtained from sampling stations with different salinities was carried out, and the copper uptake by algae cells was measured then. It was found that, the cells' uptake of copper increased with rice ion copper, not the content of total copper.
文摘1. PREFACE Lingdingyang is a trumpet estuary. It accepts the runoff of the Dongjiang River, the Beijiang River, the Zhengjiang River and the Liusihe River. It also accepts a part of the runoff of the Xijiang River. Its mean year runoff is 1.742×10" M^3. In resent ten years, industry and agriculture are developing rapidly in Guangzhou City, Dongguan City, Zhongshan City, Shunde County, Panyu County. Lingdingyang’s pollution is increesing. Water quality of lingdingyang is steadily deteriorated. In order to investigate the situation of water environment of Lingdingyang, we study its static environmental capacity of nitrogen and phosphorus. LANDSAT imageries are used in the study. The concentrations of nitrogen and phosphorous is detected by convention method.
基金Supported by the National Key Research and Development Program of China(No.2015CB954002)the National Natural Science Foundation of China(Nos.41876134,41676112,41276124)+2 种基金the University Innovation Team Training Program for Tianjin(No.TD12-5003)the Tianjin 131 Innovation Team Program(No.20180314)the Changjiang Scholar Program of Chinese Ministry of Education(No.T2014253)to Jun SUN。
文摘To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21°N–23.5°N,111°E–117°E).Samples were collected from 65 stations including one for time-series sampling.A total of 212 phytoplankton taxa were identified from 61 genera belonging to 4 phyla.Among them,122 species identified from 42 genera of Bacillariophyta and 83 species from 15 genera of Pyrrophyta.Chain-forming diatoms dominated the phytoplankton community where Pseudonitzschia delicatissima,Guinardia striata,Thalassionema nitzschioides,and P.pungens comprised about 52%of the total abundance.However,higher cell abundances concentrated on both sides of the estuary,because of low salinity and high nutrients brought by diluted water.In addition,Canonical Correspondence Analysis revealed that salinity and dissolved inorganic nitrogen shaped the species composition in the study area.Furthermore,the Jaccard similarity index showed prevailing high similarity in the distribution of species in low-salinity diluted waters,and the Bray-Curtis similarity depicted distinguished grouping for phytoplankton assemblages along the salinity gradient.However,phytoplankton diel vertical cycles showed maximum abundance occurred at 2:00 am,which was mainly contributed by benthic phytoplankton species Pseudo-nitzschia spp.and T.nitzschioides.
基金The Knowledge Innovation Project of Chinese Academy of Sciences under contract Nos KZCX2-YW-Q07, KZCX2-YW-T001, KZCX2-YW-213 and SQ200805the National Natural Science Foundation of China under contract Nos U0633007, 40906057 and 40531006
文摘Chemometric approach based on principal component analysis(PCA) was utilized to examine the spatial variances of environmental and ecological characteristics in the Zhujiang River(Pearl River) Estuary and adjacent waters(ZREAW) in the South China Sea. The PCA result shows that the ZREAW can be divided into different zones according to the principal components and geographical locations of the study stations,and indicates that there are distinct regional variances on environmental features and the corresponding phytoplankton biomass and community structures among different areas. The spatial distribution of ecological features was implied to be influenced by various degrees of the different water resources,such as the Pearl River discharges,the coastal current and the oceanic water from the South China Sea. The variation of the biomass maximum zone and the complex impacts on the spatial distributions of phytoplankton biomass and production were also evaluated.
基金The Ocean Special Funds for Scientific Research on Public Causes under contract No.201105001-2the National Basic Research Program(973 Program)of China under contract No.2013CB956502the National Natural Science Foundation of China under contract Nos 41376044,41276083 and 41476049
文摘Real-time observations in the field and numerical simulations(with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum(TM) in the Zhujiang(Pearl River) Estuary(ZE). The spatial distribution pattern of the TM varies with the longitudinal distributions of salinity and suspended sediment concentration(SSC). The SSC is enhanced and the TM is intensified during dry seasons,whereas the center of the TM moves upstream by a distance of 10 km during wet seasons. The formation of the TM is influenced by a complex combination of numerous factors, including tides, river discharges and topography, wherein sediment resuspension and vertical circulation dominate the formations and variability of the TM.
基金The National Natural Science Foundation of China under contract No.41890851the Key Research Program of Frontier Sciences+3 种基金Chinese Academy of Sciences,under contract No.QYZDJ-SSW-DQC034the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract No.GML2019ZD0304the fund of Chinese Academy of Sciences under contract No.ISEE2021PY01the project of Department of Natural Resources of Guangdong Province under contract No.[2020]017。
文摘A wave-current-sediment coupled numerical model is employed to study the responses of suspended sediment transport in the wet season to changes in shoreline and bathymetry in the Zhujiang(Pearl)River Estuary(ZRE)from 1971 to 2012.It is shown that,during the wavy period,the large wave-induced bottom stress enhances sediment resuspension,resulting in an increase in the area of suspended sediment concentration(SSC)greater than 100 mg/L by 183.4%.On one hand,in spring tide,the change in shoreline reduces the area of SSC greater than 100 mg/L by 17.8%in the west shoal(WS)but increases the SSC,owing to the closer sediment source to the offshore and the stronger residual current at the Hengmeng(HEM)and Hongqili(HQL)outlets.The eastward Eulerian transport is enhanced in the WS and west channel(WC),resulting in a higher SSC there.The reclamation of Longxue Island(LXI)increases SSC on its east side and east shoal(ES)but decreases the SSC on its west and south sides.Moreover,in the WC,the estuarine turbidity maximum(ETM)is located near the saltwater wedge and moves southward,which is caused by the southward movement of the maximum longitudinal Eulerian transport.In neap tide,the changes are similar but relatively weaker.On the other hand,in spring tide,the change in bathymetry makes the SSC in the WS increase,and the area of SSC greater than 100 mg/L increases by 11.4%and expands eastward and southward,which is caused by the increases in wave-induced bottom stress and eastward Eulerian transport.On the east side of the WC,the eastward Eulerian transport decreases significantly,resulting in a smaller SSC in the middle shoal(MS).In addition,in the WC,the maximum SSC is reduced,which is caused by the smaller wave-induced bottom stress and a significant increase of 109.88%in southward Eulerian transport.The results in neap tide are similar to those in spring tide but with smaller changes,and the sediment transports northward in the WC owing to the northward Eulerian transport and vertical shear transport.This study may provide some references for marine ecological environment security and coastal management in the ZRE and other estuaries worldwide affected by strong human interventions.
基金The National Key Research and Development Progam of China under contract No.2017YFA0603003the National Basic Research Program(973 Program)of China under contract No.2015CB954002+3 种基金the Public Science and Technology Research Funds Project of Ocean under contract No.201505003the National Natural Science Foundation of China under contract Nos41676170,41676172,41476155,41621064 and 41406202the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,State Oceanic Administration of China under contract No.SOEDZZ1801the Research Startup Project of Nanjing Instiute of Geography and Limnology,Chinese Academy of Sciences under contract No.Y7SL051001
文摘The distributions of estuarine colored dissolved organic matter(CDOM)are the combined results of physicalbiogeochemical processes.Remote sensing is needed to monitor highly dynamically estuarine CDOM.Using in situ data from four seasonal cruises,an algorithm is developed to estimate CDOM absorption coefficient at 400nm(aCDOM(400))in the Zhujiang(Pearl River)Estuary(ZJE).The algorithm uses band ratios of Rrs(667)/Rrs(443)and Rrs(748)/Rrs(412).By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite(MODIS/Aqua)data from 2002 to 2014,seasonal climatology aCDOM(400)in the ZJE is calculated.CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography.Along the section vertical to a water depth gradient,the seasonal aCDOM(400)exponentially decreased(y=aebx,b〈0),but with great differences among seasons.Riverine fresh water is the primary source of CDOM in the ZJE.Fulvic acid fraction decreases with increasing salinity.Using developed algorithms,conservative CDOM mixing equation,and river discharge,effective riverine end-member concentration and flux of dissolved organic carbon(DOC)in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data.Both effective riverine end-member DOC concentration and flux are positively related to the river discharge,significantly in summer with R-2 of 0.698 for concentration and 0.965 7 for flux.
文摘The five chemical bound forms of Fe, Al and Mn in sediments in the main channel of the Zhujiang River.and its estuary, namely, exchangeable, carbonic, oxidative, organic and residual (in crystal) forms, were determined. The method of sequential extraction was used for separating the five bound forms.The main chemical form of the three elements in the sediments of the Zhujiang River and its estuarine zone is the residual one. The exchangeable form exists only in a small fraction.Correlationships between the concentration of a certain form of heavy metals and Eh. pH and salinity were discussed. The principles of geochemistry are used to explain the mechanism of heavy metal transport in the river.It was also found that the distribution rule of the chemical forms of Fe, Al and Mn in sediments in the lower reaches of the Zhujiang River was similar to the one in the lower reaches of the Yamaska River.
基金The National Basic Research Program(973 program) of China under contract No.2013CB956104the National Natural Science Foundation of China under contract Nos 41106054,41306109 and 41476038
文摘Sea surface temperature (SST) proxies including B/Ca, Mg/Ca, St/Ca, U/Ca and δ180 were analyzed in the skeleton of a Porites coral collected from the Zhujiang River (Pearl River) Estuary (ZRE). These geochemical proxies are influenced by river runoff and this area of the northern South China Sea is strongly affected by seasonal freshwater floods. We assessed the robustness of each SST proxy through comparison with the local instrumental SST. Coral St/Ca shows the highest correlation with SST variations (r2=0.59), suggesting St/Ca is the most robust SST proxy. In contrast, coral δ180 (r2=0.46), B/Ca (r2=0.43) and U/Ca (r2=0.41) ratios were only moderately correlated with SST variations, suggesting that they are disturbed by some other factors in addition to SST. The poor correlation (r2=0.27) between SST and Mg/Ca indicates that Mg/Ca in coral skeletons is not a simple function of SST variations. This may ultimately limit the use of Mg/Ca as a coral paleothermometer.
基金The National Basic Research Program(973 Program)sponsored by the Ministry of Science and Technology under contract Nos 2014CB953700 and 2014CB953702the National Natural Science Foundation of China under contract Nos 40906040 and 41276063+3 种基金the Fundamental Research Funds for the Central Universities of Chinathe Natural Science Foundation of Fujian Province of China under contract No.2011J01277the Laboratory of Marine Ecosystem and Biogeochemistry of State Oceanic Administration of China under contract No.LMEB201103the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Education of Ministry of China
文摘The performance and integrity of a cassette cross-flow ultrafilter (Pellicon 2, Millipore) are examined with a suite of macromolecules of different molecular masses. The retention coefficient during the cross-flow ultrafiltration experiments increases with increasing molecular mass and reaches 90% with 10 kDa dextran in both milli-Q water and ultrafiltered seawater media. Based on a 90% retention coefficient, the molecular mass cut-off for the ultrafiltration membrane is defined at 10 kDa, which is ten times (1 kDa) that rated by the manufacturer. To further validate the accuracy of the laboratory calibration, the samples from the lower Zhujiang River and the Jiulong River Estuary are ultrafiltered with the cassette ultrafiltration membrane and the colloidal organic carbon abundances in these samples are quantified with the ultrafiltration per- meation model based on time series permeation subsamples. The colloidal organic carbon abundances are 5.8%-21.1% in the Jiulong River Estuary and 5.6%-11.0% in the lower Zhujiang River. These are consistent with the reported values for both estuaries as well as with the colloidal organic carbon abundances in ma- rine environments over the coastal and open oceans with 10 kDa cut-off membranes. Therefore, these field data support the laboratory calibration result and indicate the validity of the experimental and quantification procedure adopted. The discrepancy between the nominal molecular mass cut-off and the actual pore size of the ultrafiltration membrane should be of great concern for research in colloidal and nanoparticle biogeochemistry. Careflfl examination of the membrane integrity should be taken during ultrafiltration ex- oeriments in order to avoid misleading molecular mass cut-off information.
基金The Zhejiang Key Science and Technology Project under contract No.2020C02004the National Key Research and Development Program of China under contract Nos 2017YFA0604901 and 2017YFA0604902+3 种基金the Basic Public Welfare Research Program of Zhejiang Province under contract No.LGF21D010004the National Key Research and Development Program of China under contract No.2016YFC1401605the National Natural Science Foundation of China under contract No.41776183the Curriculum Ideological and Political Teaching Research Project in the Universities of Zhejiang Province(Grouped Ideological and Political Teaching Model Research in the Subject of Marine Remote Sensing)。
文摘The impacts of the Hong Kong-Zhuhai-Macao Bridge(HKZMB)on suspended sediment content(SSC)were analysed in the Zhujiang River Estuary based on data from HY-1C,which was launched in September 2018 in China,carrying Coastal Zone Imager(CZI)and Chinese Ocean Color and Temperature Scanner on it.A new SSC inversion model was established based on the relationship between in-situ SSC and the remote sensing reflectance in red and near-infrared bands of CZI image.HY-1C satellite data obtained from October to December 2019 were applied to retrieve SSC in the Zhujiang River Estuary.The results show that SSC around the HKZMB is ranging from 20 mg/L to 95 mg/L.SSC change obviously on two sides of the bridge.During flooding and ebbing period,SSC increases obviously downstream of the bridge.SSC difference between upstream and downstream is ranging from 5 mg/L to 20 mg/L.Currents flowing across the HKZMB,the change trend of SSC in most places upstream and downstream is almost the same that SSC downstream of the bridge is higher than SSC upstream.The tidal currents interact with bridge piers,inducing vortexes downstream,leading the sediment to re-suspend downstream of the bridge piers.Other factors,including seafloor topography and wind,can also contribute to the distribution of SSC in the Zhujiang River Estuary.
基金The National Key Research and Development Program under contract No.2016YFA0601203the National Natural Science Foundation of China under contract Nos 41476137 and 41676075+1 种基金the Project of State Key Laboratory of Tropical Oceanography under contract No.LTOZZ1504-1the Hundred Talent Program of Chinese Academy of Sciences under contract No.Y35L041001
文摘Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes.Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across environments.However,empirical leucine-to-carbon conversion factors(e CFs) are seldom determined in situ because of time consuming and little is known on regulating factors for the e CFs.During May 2015 to January 2016,fourteen dilution experiments were conducted,from the Zhujiang(Pearl River) Estuary to the coast of the northern South China Sea,to determine spatiotemporal variability in the e CFs and its potential controlling factors along an environmental gradient.The e CFs showed clear spatial variations with the highest(1.27–1.69(kg C)/(mol Leu)) in low salinity waters(salinity〈15),intermediate(1.03–1.25(kg C)/(mol Leu)) in moderate salinity(salinity of 15–25),and the lowest(0.48–0.85(kg C)/(mol Leu)) in high salinity waters(salinity〉25).Substrate availability was responsible for spatial variability in the e CFs.In the pristine coastal waters,low e CFs was related to substrate limitation and leucine incorporated was respired to maximize the survival rather than bacterial production.Hence,the e CFs measurement was needed for estimating bacterial production accurately in various marine environments.