In order to depict the distribution of diatom fossils in surface sediments and to establish a reliable reference data for further paleoenvironmental study in the Changjiang (Yangtze) River estuary and its adjacent wat...In order to depict the distribution of diatom fossils in surface sediments and to establish a reliable reference data for further paleoenvironmental study in the Changjiang (Yangtze) River estuary and its adjacent waters, the diatom fossils from 34 surface sediment samples and their relationship with environmental variables were analyzed by principal component analysis and redundancy correspondence analysis. The diversity and abundance of diatom fossils were analyzed. Some annual average parameters of the overlying water (salinity, temperature, turbidity, dissolved oxygen, depth, dissolved inorganic nitrogen, dissolved inorganic phosphate and dissolved inorganic silicate) were measured at each sampling site. A total of 113 diatom taxa and one silicoflagellate species were identified in the investigation area. Diatom fossils were better preserved in fine sediments. The absolute abundance of diatom fossils did not significantly diff er between inshore and off shore areas, the species diversity decreased from inshore to off shore. This may be because high nutrients and low salinity promoted the growth of more brackish species in coastal waters. The diatom taxa were divided into three groups, on the basis of their response and indication to environmental changes. For example, Actinocyclus ehrenbergii and Cyclotella stylorum were dominant in coastal waters (Group 1 and Group 3) with high nutrients and low salinity;the relative abundances of Paralia sulcata and Podosira stelliger were significantly higher in off shore sites (Group 2, average 39.5%), which were characterized by high salinity and deep water. Four environmental variables (salinity, dissolved inorganic nitrogen, temperature and water depth) explained the composition and distribution of diatom taxa independently ( P< 0.05), this finding can be applied in further paleoenvironmental reconstruction research in this area.展开更多
Harmful algal blooms（HABs） have been increasingly frequent in coastal waters around the world over the last several decades. Accelerated coastal eutrophication, resulting from the increased anthropogenic loadings of...Harmful algal blooms（HABs） have been increasingly frequent in coastal waters around the world over the last several decades. Accelerated coastal eutrophication, resulting from the increased anthropogenic loadings of nutrients, is commonly assumed to be the primary cause of this increase. However, although important,accelerated coastal eutrophication may not be the only explanation for the increasing blooms or toxic outbreaks in estuarine waters. Changes in riverine material fluxes other than nutrients, such as sediment load, may significantly affect biological activities and HAB incidence in estuarine and coastal waters. A case study off the Changjiang（Yangtze River） Estuary indicated that with the increasing riverine loadings of nutrients, the sediment load from the Changjiang River has been reduced by 70% over the past four decades. A comparison of long-term data revealed that the phytoplankton biomass maximum has expanded to a region of much lower salinity due to the drastic reduction in riverine sediment load and the subsequent improvement in light penetration in the Changjiang River plume. Furthermore, there was an apparent mirror-image relationship between the sediment load from the Changjiang River and the HAB incidence off the Changjiang Estuary over the past four decades, and the number of HAB incidents was significantly negatively correlated with the sediment load. Therefore, it is argued that the drastic decline in sediment load from the Changjiang River reduced turbidity in the Changjiang Estuary and thus contributed to the increased frequency of HABs in the buoyant discharge plumes.展开更多
This study aimed to evaluate the potential impacts of an introduced clam Mercenaria mercenaria on estuarine ecosystem, and implications for the niche competition with a native clam Meretrix meretrix. The biodeposition...This study aimed to evaluate the potential impacts of an introduced clam Mercenaria mercenaria on estuarine ecosystem, and implications for the niche competition with a native clam Meretrix meretrix. The biodeposition, respiration, and excretion rates of 34. mercenaria were determined seasonally using a sediment trap and a closed respirator in field. The biodeposition rates ofM. mercenaria were 0.06-0.37 g/ （ind.·d）, and the respiration rates were 0.31-14.66 mg/（ind.·d）. The ammonia and phosphate excretion rates were 0.18-36.70 and 1.44-14.87 μg/（ind.·d）, respectively. The hard clam M. mercenaria may discharge dry deposits up to 2.1 × 10^5 t, contribute 18.3 t ammonia and 9.0 t phosphate to culture ponds, and consume 7.9×10^3 t O2 from ponds annually. It suggested that the hard clam M. mercenaria might play an important role in pelagic-benthic coupling in pond ecosystem through biodeposition and excretion. A comparison of the key physiological parameters of the introduced clam M. mercenaria and the native clam Meretrix meretrix suggested that M. mercenaria had a niche similar to that of Meretrix meretrix in Shuangtaizi estuary and might have a potential competition with Meretrix meretrix for habitat and food ifM. mercenaria species escaped from the culture pond or artificially released in estuarine ecosystem.展开更多
Tidal marshes are an important habitat and nursery area for fi sh.In the past few decades,rapid economic development in the coastal areas of China has led to the interruption and destruction of an increasing number of...Tidal marshes are an important habitat and nursery area for fi sh.In the past few decades,rapid economic development in the coastal areas of China has led to the interruption and destruction of an increasing number of tidal marshes.The growing interest in tidal marsh restoration has increased the need to understand the relationship between geomorphological features and fi sh assemblages in the design of marsh restoration projects.We studied temporal variations in,and the effects of creek geomorphological features on,the estuarine tidal creek fi sh community.Using modifi ed channel nets,we sampled fi sh monthly from March 2007 to February 2008 from seven tidal creeks along an intertidal channel system in Chongming Dongtan National Nature Reserve.Fourteen creek geomorphological variables were measured or derived to characterize intertidal creek geomorphological features.The Gobiidae,with 10 species,was the most speciesrich family.The most abundant fi sh species were Liza affi nis,Chelon haematocheilus,and Lateolabrax maculatus.The fi sh community was dominated by juvenile marine transients,which comprised about 80% of the total catch.The highest abundance of fi sh occurred in June and July,and the highest biomass occurred in December.Canonical redundancy analyses demonstrated that depth,steepness,cross-sectional area,and volume signifi cantly affected the fi sh species assemblage.L.affi nis favored small creeks with high elevations.Synechogobius ommaturus,Acanthogobius luridus,and Carassius auratus preferred deep,steep creeks with a large cross-sectional area and volume.These fi ndings indicate that the geomorphological features of tidal creeks should be considered in the conservation and sustainable management of fi sh species and in the restoration of salt marshes.展开更多
Fish communities in a （third-order） intertidal creek in Dongtan marsh in the Changjiang （Yangtze） River estuary were investigated seasonally for one year. A total of 1 996 fish specimens （10 967.8 g） comprising ...Fish communities in a （third-order） intertidal creek in Dongtan marsh in the Changjiang （Yangtze） River estuary were investigated seasonally for one year. A total of 1 996 fish specimens （10 967.8 g） comprising 26 species and 15 families were collected. Abundances of fish communities in the intertidal salt marsh creek were primarily dominated by Boleophthalmus pectinirostris （19.8%）, Collichthys lucidus （18.6%）, Periophthalmus magnuspinnatus （18.2%）, Liza haematocheilus （17.9%）, and secondarily by Mugilogobius abel （8.5%）, L. carinatus （7.2%）, Odontamblyopus lacepedii （4.3%）, and Acanthogobius ommaturus （3.9%）; another 18 species were present only occasionally. Non-MDS ordination and SIMPER analysis indicated that there were two fish communities in the intertidal salt marsh creek. In spring, the communities were dominated by B. pectinirostris, P. magnuspinnatus, C. lucidus and M. abei; in summer, autumn, and winter by L. haematocheilus, L. carinatus, A. ommaturus and O. lacepedii. Some species showed strong habitat selection; L. carinatus and P magnuspinnatus were distributed mainly in the upper and middle creek, while B. pectinirostris, M. abei and O. lacepedii inhabited the middle and lower creek. The study indicated that the salt marshes of the Changjiang River estuary are an important nursery and feeding habitat for many fishes and should be protected.展开更多
To study the stratified stability of a water column in the North Passage of the Yangtze River Estuary,a numerical model of the hydrodynamics of this estuary is established using the EFDC model.On the basis of EFDC res...To study the stratified stability of a water column in the North Passage of the Yangtze River Estuary,a numerical model of the hydrodynamics of this estuary is established using the EFDC model.On the basis of EFDC results,this paper derives and pro-vides the discriminative index of water body stability caused by salinity and analyzes the along-range variation in water body strati-fication stability in the North Passage of the Yangtze River Estuary and the periodic variation at a key location(bend area)based on the simulation results of the numerical model.This work shows that the water body in the bend area varies between mixed and strati-fied types,and the vertical average flow velocity has a good negative correlation with the differential velocity between the surface and bottom layers of the water body.The model simulation results validate the formulae for the stratified stability discriminant during spring tides.展开更多
The use patterns of salt marsh habitats by fish assemblages were investigated in two welldeveloped intertidal creeks in the Changjiang(Yangtze)River estuary on spatial and temporal scales.Samples were collected using ...The use patterns of salt marsh habitats by fish assemblages were investigated in two welldeveloped intertidal creeks in the Changjiang(Yangtze)River estuary on spatial and temporal scales.Samples were collected using fyke nets at two sites during day and night in each season throughout four years.Notable changes in fish assemblages were detected over seasonal and interannual cycles,with many more marine species present in winter assemblages,whereas freshwater and estuarine species characterized the other seasonal samplings.The appearance of catadromous species in intertidal creeks mainly depended upon their specific physiological requirements,such as spawning migration.No significant diel shifts were observed in fish assemblages.This diel pattern may be a combined consequence of avian predation pressure and other drivers(i.e.,inherent living behaviors,food availability,and predation by piscivorous fishes).The spatial difference in fish community was insignificant even though the two intertidal creeks were different in size.Intertidal creeks with different size could possess similar ecological value for fish fauna.Redundancy analysis(RDA)showed that biological factors exerted greater effects on fish assemblages than physical variables.Temporal variations were strongly facilitated by food availability,but negatively impacted by avian predation.Salinity,water temperature,and river runoff had weak influence on temporal variations of fish communities.The lengthfrequency distribution showed that the fish collected in these two sites mainly consisted of young-of-year and juvenile fish,which confirmed that the creeks provided important nursery and forage roles in the process of fish ontogenetic development.Further,we proposed that salt marsh conservation management should be equally applied to all well-developed intertidal creeks regardless of creek size.展开更多
Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and drivers.By revisiting t...Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and drivers.By revisiting the repeated surveys of dissolved oxygen(DO) and other relevant hydrographic parameters along the section from the Changjiang River Estuary to the Jeju-do in the summer from 1997 to 2014,rather different trends were revealed for the dual low-DO cores.The nearshore low-DO core,located close to the river mouth and relatively stable,shows that hypoxia has become more severe with the lowest DO descen ding at a rate of -0.07 mg/(L·a) and the thickness of low-DO zone rising at a rate of 0.43 m/a.The offshore core,centered around 40-m isobath but moving back and forth between 123.5°-125°E,shows large fluctuations in the minimum DO concentration,with the thickness of low-DO zone falling at a rate of -1.55 m/a.The probable factors affecting the minimum DO concentration in the two regions also vary.In the nearshore region,the decreasing minimum DO is driven by the increase in both stratification and primary productivity,with the enhanced extension of the Changjiang River Diluted Water(CDW) strengthening stratification.In the offshore region,the fluctuating trend of the minimum DO concentration indicates that both DO loss and DO supplement are distinct.The DO loss is primarily attributed to bottom apparent oxygen utilization caused by the organic matter decay and is also relevant to the advection of low-DO water from the nearshore region.The DO supplement is primarily due to weakened stratification.Our analysis also shows that the minimum DO concentration in the nearshore region was extremely low in 1998,2003,2007 and 2010,related to El Ni?o signal in these summers.展开更多
The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted ...The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted during the summer of 2022 in the Changjiang River(Yangtze River) Estuary(CJE) and its adjacent waters.The settling column method was employed to measure the sinking velocity(SV) of different size fractions of phytoplankton at the surface of the sea and to analyze their environmental control mechanisms.The findings reveal significant spatial variation in phytoplankton SV(-0.55-2.41 m/d) within the CJE.High-speed sinking was predominantly observed in phosphate-depleted regions beyond the CJE front.At the same time,an upward trend was more commonly observed in the phosphate-rich regions near the CJE mouth.The SV ranges for different sizefractionated phytoplankton,including micro-(>20 μm),nano-(2-20 μm),and picophytoplankton(0.7-2 μm),were-0.50-4.74 m/d,-1.04-1.59 m/d,and-1.24-1.65 m/d,respectively.Correlation analysis revealed a significant negative correlation between SV and dissolved inorganic phosphorus(DIP),implying that the influence of DIP contributes to SV.The variations in phytoplankton alkaline phosphatase activity suggested a significant increase in SV across all size fractions in the event of phosphorus limitation.Phytoplankton communities with limited photo synthetic capacity(maximum photochemical efficience,Fv/Fm <0.3) were found to have higher SV than that of communities with strong capacity,suggesting a link between sinking and alterations in physiological conditions due to phosphate depletion.The findings from the in situ phosphate enrichment experiments confirmed a marked decrease in SV following phosphate supplementation.These findings suggest that phosphorus limitation is the primary driver of elevated SV in the CJE.This study enhances the comprehension of the potential mechanisms underlying hypoxic zone formation in the CJE,providing novel insights into how nearshore eutrophication influences organic carbon migration.展开更多
Marine sediments collected from the Zhujiang(Pearl) River Estuary(ZRE) and South China Sea(SCS) were utilized to study the occurrence and spatial distribution of tetrabromobisphenol A(TBBPA) and hexabromocyclododecane...Marine sediments collected from the Zhujiang(Pearl) River Estuary(ZRE) and South China Sea(SCS) were utilized to study the occurrence and spatial distribution of tetrabromobisphenol A(TBBPA) and hexabromocyclododecane(HBCDD).The levels of TBBPA and HBCDD in sediments ranged from not detected(nd) to 6.14 ng/g dry weight(dw) and nd to 0.42 ng/g dw.TBBPA concentrations in marine sediments were substantially higher than HBCDD.The concentrations of TBBPA and HBCDD in the ZRE sediments were significantly greater than those in the SCS.α-HBCDD(48.7%) and γ-HBCDD(46.2%) were the two main diastereoisomers of HBCDD in sediments from the ZRE,with minor contribution of β-HBCDD(5.1%).HBCDD were only found in one sample from the northern SCS.The enantiomeric fraction of α-HBCDD in sediments from the ZRE was obviously greater than 0.5,indicating an accumulation of(+)-α-HBCDD.The enantiomers of HBCDD were not measured in sediments from the SCS.This work highlighted the environmental behaviors of TBBPA and HBCDD in marine sediments.展开更多
Massive bodies of low-oxygen bottom waters are found in coastal areas worldwide,which are detrimental to coastal ecosystems.In summer 2020,the response of coastal hypoxia to extreme weather events,including a catastro...Massive bodies of low-oxygen bottom waters are found in coastal areas worldwide,which are detrimental to coastal ecosystems.In summer 2020,the response of coastal hypoxia to extreme weather events,including a catastrophic flooding,an extreme marine heatwave,and Typhoon Bavi,is investigated based on multiple satellite,four cruises,and mooring observations.The extensive fan-shaped hypoxia zone presents significant northward extension during July-September 2020,and is estimated as large as 13 000 km^(2) with rather low oxygen minimum(0.42 mg/L) during its peak in 28-30 August.This severe hypoxia is attributed to the persistent strong stratification,which is indicated by flood-induced larger amount of riverine freshwater input and subsequent marine heatwave off the Changjiang River Estuary.Moreover,the Typhoon Bavi has limited effect on the marine heatwave and coastal hypoxia in summer 2020.展开更多
A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare e...A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.展开更多
基金Supported by the National Natural Science Foundation of China(No.41506142)the NSFC-Shandong Joint Fund for Marine Science Research Centers(No.U1606404)the Sino-Australian Centre for Healthy Coasts of National Key Research and Development Plan(No.2016YFE0101500)
文摘In order to depict the distribution of diatom fossils in surface sediments and to establish a reliable reference data for further paleoenvironmental study in the Changjiang (Yangtze) River estuary and its adjacent waters, the diatom fossils from 34 surface sediment samples and their relationship with environmental variables were analyzed by principal component analysis and redundancy correspondence analysis. The diversity and abundance of diatom fossils were analyzed. Some annual average parameters of the overlying water (salinity, temperature, turbidity, dissolved oxygen, depth, dissolved inorganic nitrogen, dissolved inorganic phosphate and dissolved inorganic silicate) were measured at each sampling site. A total of 113 diatom taxa and one silicoflagellate species were identified in the investigation area. Diatom fossils were better preserved in fine sediments. The absolute abundance of diatom fossils did not significantly diff er between inshore and off shore areas, the species diversity decreased from inshore to off shore. This may be because high nutrients and low salinity promoted the growth of more brackish species in coastal waters. The diatom taxa were divided into three groups, on the basis of their response and indication to environmental changes. For example, Actinocyclus ehrenbergii and Cyclotella stylorum were dominant in coastal waters (Group 1 and Group 3) with high nutrients and low salinity;the relative abundances of Paralia sulcata and Podosira stelliger were significantly higher in off shore sites (Group 2, average 39.5%), which were characterized by high salinity and deep water. Four environmental variables (salinity, dissolved inorganic nitrogen, temperature and water depth) explained the composition and distribution of diatom taxa independently ( P< 0.05), this finding can be applied in further paleoenvironmental reconstruction research in this area.
基金The National Natural Science Foundation of China under contract No.41576084the Natural Science Foundation of ChinaShandong Joint Fund for Marine Ecology and Environmental Sciences under contract No.U1406403the Key Project of Fundamental Research Funds for the First Institute of Oceanography,State Oceanic Administration under contract No.GY0215G12
文摘Harmful algal blooms（HABs） have been increasingly frequent in coastal waters around the world over the last several decades. Accelerated coastal eutrophication, resulting from the increased anthropogenic loadings of nutrients, is commonly assumed to be the primary cause of this increase. However, although important,accelerated coastal eutrophication may not be the only explanation for the increasing blooms or toxic outbreaks in estuarine waters. Changes in riverine material fluxes other than nutrients, such as sediment load, may significantly affect biological activities and HAB incidence in estuarine and coastal waters. A case study off the Changjiang（Yangtze River） Estuary indicated that with the increasing riverine loadings of nutrients, the sediment load from the Changjiang River has been reduced by 70% over the past four decades. A comparison of long-term data revealed that the phytoplankton biomass maximum has expanded to a region of much lower salinity due to the drastic reduction in riverine sediment load and the subsequent improvement in light penetration in the Changjiang River plume. Furthermore, there was an apparent mirror-image relationship between the sediment load from the Changjiang River and the HAB incidence off the Changjiang Estuary over the past four decades, and the number of HAB incidents was significantly negatively correlated with the sediment load. Therefore, it is argued that the drastic decline in sediment load from the Changjiang River reduced turbidity in the Changjiang Estuary and thus contributed to the increased frequency of HABs in the buoyant discharge plumes.
基金Supported by the National Special Research Fund for Non-Profit Marine Sector(No.201305043)the Key Laboratory for Ecological Environment in Coastal Areas,State Oceanic Administration(No.201311)+1 种基金the Collaborative Innovation Center for Zhejiang Marine High-Efficiency and Healthy Aquaculturethe K.C.Wong Magna Fund at Ningbo University
文摘This study aimed to evaluate the potential impacts of an introduced clam Mercenaria mercenaria on estuarine ecosystem, and implications for the niche competition with a native clam Meretrix meretrix. The biodeposition, respiration, and excretion rates of 34. mercenaria were determined seasonally using a sediment trap and a closed respirator in field. The biodeposition rates ofM. mercenaria were 0.06-0.37 g/ （ind.·d）, and the respiration rates were 0.31-14.66 mg/（ind.·d）. The ammonia and phosphate excretion rates were 0.18-36.70 and 1.44-14.87 μg/（ind.·d）, respectively. The hard clam M. mercenaria may discharge dry deposits up to 2.1 × 10^5 t, contribute 18.3 t ammonia and 9.0 t phosphate to culture ponds, and consume 7.9×10^3 t O2 from ponds annually. It suggested that the hard clam M. mercenaria might play an important role in pelagic-benthic coupling in pond ecosystem through biodeposition and excretion. A comparison of the key physiological parameters of the introduced clam M. mercenaria and the native clam Meretrix meretrix suggested that M. mercenaria had a niche similar to that of Meretrix meretrix in Shuangtaizi estuary and might have a potential competition with Meretrix meretrix for habitat and food ifM. mercenaria species escaped from the culture pond or artificially released in estuarine ecosystem.
基金Supported by the National Basic Research Program of China(973 Program)(No.2013CB430404)the National Science and Technology Ministry(No.2010BAK69B14)the Science and Technology Department of Shanghai(No.10dz1200700)
文摘Tidal marshes are an important habitat and nursery area for fi sh.In the past few decades,rapid economic development in the coastal areas of China has led to the interruption and destruction of an increasing number of tidal marshes.The growing interest in tidal marsh restoration has increased the need to understand the relationship between geomorphological features and fi sh assemblages in the design of marsh restoration projects.We studied temporal variations in,and the effects of creek geomorphological features on,the estuarine tidal creek fi sh community.Using modifi ed channel nets,we sampled fi sh monthly from March 2007 to February 2008 from seven tidal creeks along an intertidal channel system in Chongming Dongtan National Nature Reserve.Fourteen creek geomorphological variables were measured or derived to characterize intertidal creek geomorphological features.The Gobiidae,with 10 species,was the most speciesrich family.The most abundant fi sh species were Liza affi nis,Chelon haematocheilus,and Lateolabrax maculatus.The fi sh community was dominated by juvenile marine transients,which comprised about 80% of the total catch.The highest abundance of fi sh occurred in June and July,and the highest biomass occurred in December.Canonical redundancy analyses demonstrated that depth,steepness,cross-sectional area,and volume signifi cantly affected the fi sh species assemblage.L.affi nis favored small creeks with high elevations.Synechogobius ommaturus,Acanthogobius luridus,and Carassius auratus preferred deep,steep creeks with a large cross-sectional area and volume.These fi ndings indicate that the geomorphological features of tidal creeks should be considered in the conservation and sustainable management of fi sh species and in the restoration of salt marshes.
基金Supported by Special Research Fund for the National Non-profit Institutes (East China Sea Fisheries Research Institute) (No.2007M03) and Administration Bureau of Virescence of Shanghai Municipality
文摘Fish communities in a （third-order） intertidal creek in Dongtan marsh in the Changjiang （Yangtze） River estuary were investigated seasonally for one year. A total of 1 996 fish specimens （10 967.8 g） comprising 26 species and 15 families were collected. Abundances of fish communities in the intertidal salt marsh creek were primarily dominated by Boleophthalmus pectinirostris （19.8%）, Collichthys lucidus （18.6%）, Periophthalmus magnuspinnatus （18.2%）, Liza haematocheilus （17.9%）, and secondarily by Mugilogobius abel （8.5%）, L. carinatus （7.2%）, Odontamblyopus lacepedii （4.3%）, and Acanthogobius ommaturus （3.9%）; another 18 species were present only occasionally. Non-MDS ordination and SIMPER analysis indicated that there were two fish communities in the intertidal salt marsh creek. In spring, the communities were dominated by B. pectinirostris, P. magnuspinnatus, C. lucidus and M. abei; in summer, autumn, and winter by L. haematocheilus, L. carinatus, A. ommaturus and O. lacepedii. Some species showed strong habitat selection; L. carinatus and P magnuspinnatus were distributed mainly in the upper and middle creek, while B. pectinirostris, M. abei and O. lacepedii inhabited the middle and lower creek. The study indicated that the salt marshes of the Changjiang River estuary are an important nursery and feeding habitat for many fishes and should be protected.
基金supported by the National Natural Science Foundation of China(Nos.42176166,41776024).
文摘To study the stratified stability of a water column in the North Passage of the Yangtze River Estuary,a numerical model of the hydrodynamics of this estuary is established using the EFDC model.On the basis of EFDC results,this paper derives and pro-vides the discriminative index of water body stability caused by salinity and analyzes the along-range variation in water body strati-fication stability in the North Passage of the Yangtze River Estuary and the periodic variation at a key location(bend area)based on the simulation results of the numerical model.This work shows that the water body in the bend area varies between mixed and strati-fied types,and the vertical average flow velocity has a good negative correlation with the differential velocity between the surface and bottom layers of the water body.The model simulation results validate the formulae for the stratified stability discriminant during spring tides.
基金Supported by the Science and Technology Commission of Shanghai Municipality (Nos.21DZ1200900,22DZ1202600)the National Natural Science Foundation of China (No.31772405)+3 种基金the Natural Science Foundation of Shanghai (No.19ZR1416200)the Resources Monitoring Project of Shanghai Chongming Dongtan National Nature Reserve (No.CMDT-JC202101)the Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station (No.K202205)the Fundamental Research Funds for the Central Universities。
文摘The use patterns of salt marsh habitats by fish assemblages were investigated in two welldeveloped intertidal creeks in the Changjiang(Yangtze)River estuary on spatial and temporal scales.Samples were collected using fyke nets at two sites during day and night in each season throughout four years.Notable changes in fish assemblages were detected over seasonal and interannual cycles,with many more marine species present in winter assemblages,whereas freshwater and estuarine species characterized the other seasonal samplings.The appearance of catadromous species in intertidal creeks mainly depended upon their specific physiological requirements,such as spawning migration.No significant diel shifts were observed in fish assemblages.This diel pattern may be a combined consequence of avian predation pressure and other drivers(i.e.,inherent living behaviors,food availability,and predation by piscivorous fishes).The spatial difference in fish community was insignificant even though the two intertidal creeks were different in size.Intertidal creeks with different size could possess similar ecological value for fish fauna.Redundancy analysis(RDA)showed that biological factors exerted greater effects on fish assemblages than physical variables.Temporal variations were strongly facilitated by food availability,but negatively impacted by avian predation.Salinity,water temperature,and river runoff had weak influence on temporal variations of fish communities.The lengthfrequency distribution showed that the fish collected in these two sites mainly consisted of young-of-year and juvenile fish,which confirmed that the creeks provided important nursery and forage roles in the process of fish ontogenetic development.Further,we proposed that salt marsh conservation management should be equally applied to all well-developed intertidal creeks regardless of creek size.
基金The National Key Research&Development Program of China under contract No.2023YFC3108003 in Project No.2023YFC3108000the National Natural Science Foundation of China under contract No.41876026+3 种基金the Scientific Research Fund of the Second Institute of Oceanography,Ministry of Natural Resources under contract No.YJJC2201the National Programme on Global Change and Air–Sea Interaction Phase Ⅱ under contract No.GASI-01-CJKthe Zhejiang Provincial Ten Thousand Talents Program under contract No.2020R52038the Project of State Key Laboratory of Satellite Ocean Environment Dynamics under contract No.SOEDZZ2105。
文摘Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and drivers.By revisiting the repeated surveys of dissolved oxygen(DO) and other relevant hydrographic parameters along the section from the Changjiang River Estuary to the Jeju-do in the summer from 1997 to 2014,rather different trends were revealed for the dual low-DO cores.The nearshore low-DO core,located close to the river mouth and relatively stable,shows that hypoxia has become more severe with the lowest DO descen ding at a rate of -0.07 mg/(L·a) and the thickness of low-DO zone rising at a rate of 0.43 m/a.The offshore core,centered around 40-m isobath but moving back and forth between 123.5°-125°E,shows large fluctuations in the minimum DO concentration,with the thickness of low-DO zone falling at a rate of -1.55 m/a.The probable factors affecting the minimum DO concentration in the two regions also vary.In the nearshore region,the decreasing minimum DO is driven by the increase in both stratification and primary productivity,with the enhanced extension of the Changjiang River Diluted Water(CDW) strengthening stratification.In the offshore region,the fluctuating trend of the minimum DO concentration indicates that both DO loss and DO supplement are distinct.The DO loss is primarily attributed to bottom apparent oxygen utilization caused by the organic matter decay and is also relevant to the advection of low-DO water from the nearshore region.The DO supplement is primarily due to weakened stratification.Our analysis also shows that the minimum DO concentration in the nearshore region was extremely low in 1998,2003,2007 and 2010,related to El Ni?o signal in these summers.
基金The National Programme on Global Change and Air-Sea Interaction (PhaseⅡ)—Hypoxia and Acidification Monitoring and Warning Project in the CE under contract No.GASI-01-CJKthe Science Foundation of Donghai Laboratory under contract No.DH-2022KF0215+3 种基金the Oceanic Interdisciplinary Program of Shanghai Jiao Tong UniversityScientific Research Fund of the Second Institute of Oceanography,MNR under contract No.SL2022ZD207the National Key R&D Program of China under contract No.2021YFC3101702the Long-term Observation and Research Plan in the Changjiang Estuary and Adjacent East China Sea (LORCE)Project under contract No.SZ2001。
文摘The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted during the summer of 2022 in the Changjiang River(Yangtze River) Estuary(CJE) and its adjacent waters.The settling column method was employed to measure the sinking velocity(SV) of different size fractions of phytoplankton at the surface of the sea and to analyze their environmental control mechanisms.The findings reveal significant spatial variation in phytoplankton SV(-0.55-2.41 m/d) within the CJE.High-speed sinking was predominantly observed in phosphate-depleted regions beyond the CJE front.At the same time,an upward trend was more commonly observed in the phosphate-rich regions near the CJE mouth.The SV ranges for different sizefractionated phytoplankton,including micro-(>20 μm),nano-(2-20 μm),and picophytoplankton(0.7-2 μm),were-0.50-4.74 m/d,-1.04-1.59 m/d,and-1.24-1.65 m/d,respectively.Correlation analysis revealed a significant negative correlation between SV and dissolved inorganic phosphorus(DIP),implying that the influence of DIP contributes to SV.The variations in phytoplankton alkaline phosphatase activity suggested a significant increase in SV across all size fractions in the event of phosphorus limitation.Phytoplankton communities with limited photo synthetic capacity(maximum photochemical efficience,Fv/Fm <0.3) were found to have higher SV than that of communities with strong capacity,suggesting a link between sinking and alterations in physiological conditions due to phosphate depletion.The findings from the in situ phosphate enrichment experiments confirmed a marked decrease in SV following phosphate supplementation.These findings suggest that phosphorus limitation is the primary driver of elevated SV in the CJE.This study enhances the comprehension of the potential mechanisms underlying hypoxic zone formation in the CJE,providing novel insights into how nearshore eutrophication influences organic carbon migration.
基金The Guangdong Basic and Applied Basic Research Foundation under contract Nos 2021B1515020040 and 2021A1515011526the National Natural Science Foundation of China under contract Nos 42277246 and U2244221+1 种基金the Hainan Provincial Natural Science Foundation of China under contract No.422CXTD533the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) under contract No.2019BT02H594。
文摘Marine sediments collected from the Zhujiang(Pearl) River Estuary(ZRE) and South China Sea(SCS) were utilized to study the occurrence and spatial distribution of tetrabromobisphenol A(TBBPA) and hexabromocyclododecane(HBCDD).The levels of TBBPA and HBCDD in sediments ranged from not detected(nd) to 6.14 ng/g dry weight(dw) and nd to 0.42 ng/g dw.TBBPA concentrations in marine sediments were substantially higher than HBCDD.The concentrations of TBBPA and HBCDD in the ZRE sediments were significantly greater than those in the SCS.α-HBCDD(48.7%) and γ-HBCDD(46.2%) were the two main diastereoisomers of HBCDD in sediments from the ZRE,with minor contribution of β-HBCDD(5.1%).HBCDD were only found in one sample from the northern SCS.The enantiomeric fraction of α-HBCDD in sediments from the ZRE was obviously greater than 0.5,indicating an accumulation of(+)-α-HBCDD.The enantiomers of HBCDD were not measured in sediments from the SCS.This work highlighted the environmental behaviors of TBBPA and HBCDD in marine sediments.
基金The National Natural Science Foundation of China under contract Nos U23A2033 and 42230404the National Program on Global Change and Air–Sea Interaction (PhaseⅡ) under contract No.GASI-01-CJK+5 种基金the Key Research&Development Program of Zhejiang Province under contract No.2022C03044the Joint Funds of the Zhejiang Provincial Natural Science Foundation of China under contract No.LZJMZ23D050001the Long Term Observation and Research Plan in the Changjiang River Estuary and the Adjacent East China Sea Project under contract No.SZZ2007the Project of State Key Laboratory of Satellite Ocean Environment Dynamics under contract No.SOEDZZ2105the Zhejiang Provincial Natural Science Foundation under contract No.LR16D060001the Zhejiang Provincial Ten Thousand Talents Plan under contract No.2020R52038。
文摘Massive bodies of low-oxygen bottom waters are found in coastal areas worldwide,which are detrimental to coastal ecosystems.In summer 2020,the response of coastal hypoxia to extreme weather events,including a catastrophic flooding,an extreme marine heatwave,and Typhoon Bavi,is investigated based on multiple satellite,four cruises,and mooring observations.The extensive fan-shaped hypoxia zone presents significant northward extension during July-September 2020,and is estimated as large as 13 000 km^(2) with rather low oxygen minimum(0.42 mg/L) during its peak in 28-30 August.This severe hypoxia is attributed to the persistent strong stratification,which is indicated by flood-induced larger amount of riverine freshwater input and subsequent marine heatwave off the Changjiang River Estuary.Moreover,the Typhoon Bavi has limited effect on the marine heatwave and coastal hypoxia in summer 2020.
基金Supported by the China Institute of Water Resources and Hydropower Research(No.K20231586)the Water Conservancy Bureau of Yunyang County(No.YYX24C00008)+1 种基金the Ecological Forestry Development Center of Lishui City(No.2021ZDZX03)the Asia-Pacific Network for Global Change Research(No.CRRP2020-06MY-Loh)。
文摘A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.
