Typhoons are strong air–sea interactions that significantly affect the physical and biogeochemical processes of the upper ocean. Based on the Regional Ocean Modeling System-Carbon–Silicate–Nitrate Ecosystem coupled...Typhoons are strong air–sea interactions that significantly affect the physical and biogeochemical processes of the upper ocean. Based on the Regional Ocean Modeling System-Carbon–Silicate–Nitrate Ecosystem coupled model, the influence of Typhoon Bolaven(2012) on physical and ecological variables in the East China Sea and the underlying mechanisms were investigated. The results showed that the typhoon induced intense vertical mixing in the upper ocean,leading to sea surface cooling, increased salinity, nutrient concentrations, and phytoplankton blooms. Conversely, warming,reduced salinity, and decreased nutrient concentrations occurred in the subsurface layer. In the Yangtze River Estuary, the passage of typhoons effectively affected wind and current directions, shaping the dipole distribution patterns of the environmental elements. Diagnostic analysis indicated that tropical cyclone-induced horizontal advection is key in driving changes in both the physical and ecological variables within the estuary region. This study provides novel insights into the physical-ecological coupling processes and driving mechanisms governing oceanic environmental changes during typhoon events, particularly in the waters adjacent to the Yangtze River Estuary.展开更多
Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary....Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary. Concentrations of dissolved organic carbon （DOC） and dissolved inorganic carbon （DIC） in the Yellow River during dry seasons were higher than those during wet seasons. The effective concentrations of DOC （CDOC＊） were higher than the observed DOC at zero salinity. This input of DOC in the Yellow River estuary was due to sediment desorption processes in low salinity regions. In contrast to DOC, the effective concen- trations of DIC were 10% lower than the DIC measured at freshwater end, and the loss of DIC was caused by CaCO3 precipitation in low salinity region, Particulate organic carbon （POC） and particulate inorganic carbon （PIC） contents of the particles stabilized to constant values （0.5%：t：0.05% and 1.8%--0.2%, respectively） within the turbidity maximum zone （TMZ） and showed no noticeable seasonal variations. A rapid drop of PIC and rise of POC occurred simultaneously outside the TMZ due to an intense dilution of riv- erine inorganic-rich particles being transported into a pool of aquatic organic-poor particles outside the TMZ. Annually, the Yellow River transported 6.95× 10^5 t of DIC, 0.64× 10^5 t of DOC, 78.58× 10^5 t of PIC and 2.29× 10^5 t of POC to the sea.展开更多
A macro-tidal tropical estuary with high fluvial discharge is characterized by both fragility and remarkable dynamism.This study utilizes the Salween River Delta(SRD)as a case example to examine the interplay between ...A macro-tidal tropical estuary with high fluvial discharge is characterized by both fragility and remarkable dynamism.This study utilizes the Salween River Delta(SRD)as a case example to examine the interplay between morphology and vegetation under similar tidal conditions.Our analysis of correlations and inferences revealed several significant trends in the SRD:(1)an overall expansion of land area and intertidal vegetation,with the most pronounced changes occurring in the eastern sector;(2)the predominance of river discharge influencing the southwestern and northern sectors,contrasted with the primary impact of storm surges in the eastern sector;and(3)three distinct causal relationships among estuarine morphology,vegetation,storm surges,and river discharge:a direct model where river discharge shapes estuarine morphology,a progressive model in which river discharge affects vegetation distribution,subsequently influencing estuarine morphology,and a hybrid model where storm surges directly impact vegetation and indirectly modify its distribution through changes in estuarine morphology.The stability of sediment supply and the role of intertidal vegetation are crucial for the continuous seaward advance,providing a vital foundation for the protection and development of estuarine deltas.展开更多
Spartina alterniflora invasions seriously threaten the structure and functions of coastal wetlands in China.In this study,the Suaeda salsa community in the Yellow River Estuary wetland was monitored using long-term La...Spartina alterniflora invasions seriously threaten the structure and functions of coastal wetlands in China.In this study,the Suaeda salsa community in the Yellow River Estuary wetland was monitored using long-term Landsat satellite images acquired from 1997 to 2020 to quantify the impact of changes in hydrological connectivity induced by S.alterniflora on neighboring vegetation com-munities.The results showed that S.alterniflora rapidly expanded in the estuary area at a rate of 4.91 km^(2)/yr from 2010 to 2020.At the same time,the hydrological connectivity of the area and the distribution of S.salsa changed significantly.Small tidal creeks dominated the S.alterniflora landscape.The number of tidal creeks increased significantly,but their average length decreased and they tended to develop in a horizontal tree-like pattern.Affected by the changes in hydrological connectivity due to the S.alterniflora invasion,the area of S.salsa decreased by 41.1%,and the degree of landscape fragmentation increased from 1997 to 2020.Variations in the Largest Patch Index(LPI)indicated that the S.alterniflora landscape had become the dominant landscape type in the Yellow River Estuary.The res-ults of standard deviation ellipse(SDE)and Pearson’s correlation analyses indicated that a well-developed hydrological connectivity could promote the maintenance of the S.salsa landscape.The degradation of most S.salsa communities is caused by the influence of S.alterniflora on the morphological characteristics of the hydrological connectivity of tidal creek systems.展开更多
Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process.Based on prediction of sea level rise over the 21st centu...Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process.Based on prediction of sea level rise over the 21st century,the Zhujiang(Pearl River)Estuary was chosen as a prototype to study the responses of the estuary to potential sea level rise.The numerical model results show that the average salt content,saltwater intrusion distance,and stratification will increase as the sea level rises.The changes of these parameters have obvious seasonal variations.The salt content in the Lingdingyang shows more increase in April and October(the transition periods).The saltwater intrusion distance has larger increase during the low-flow periods than during the highflow periods in the Lingdingyang.The result is just the opposite in Modaomen.The stratification and its increase are larger during the low-flow periods than during the high-flow periods in Lingdingyang.The response results of transport processes to sea level rise demonstrate that:(1)The time of vertical transport has pronounced increase.The increased tidal range and currents would reinforce the vertical mixing,but the increased stratification would weaken the vertical exchange.The impact of stratification changes overwhelms the impact of tidal changes.It would be more difficult for the surface water to reach the bottom.(2)The lengthways estuarine circulation would be strengthened.Both the offshore surface residual current and inshore bottom residual current will be enhanced.The whole meridional resident flow along the transect of the Lingdingyang would be weakened.These phenomena are caused by the decrease of water surface slope(WWS)and the change of static pressure with the increase of water depth under sea level rise.展开更多
As China’s second longest river,the Yellow River(YR)carries a large volume of fresh water into the Bohai Sea with abundant nutrients and,thus,plays a crucial role in regulating the temperature and salinity near the Y...As China’s second longest river,the Yellow River(YR)carries a large volume of fresh water into the Bohai Sea with abundant nutrients and,thus,plays a crucial role in regulating the temperature and salinity near the YR Delta.In this study,using the runoff data and the Finite Volume Community Ocean Model,we simulated the salinity distribution near the YR Estuary for 2013-2022.We investigated the effect of the YR runoff on salinity dispersion and established the relationship between salinity distribution and the river’s runoff volume.Additionally,we analyzed the relationship between fish eggs and salinity distribution using fish egg da-ta.Findings indicated that the freshwater discharged from the YR converged into Laizhou Bay under the influence of tide.The sever-al years of simulation results(2013-2022)showed that the salinity field near the YR Estuary changed with the variations of river runoff entering the sea.Simultaneously,we found a positive correlation between the area of low-salinity zones(below 27)and the monthly average river runoff,and this relation could be expressed as Y_(s)=0.7457X_(r)+78.904.The characteristics of fish egg distribution revealed that fish eggs were primarily distributed in the areas characterized by salinity in the range of 25-29.展开更多
Macrobenthos can serve as an indicator of hypoxia in the estuarine ecosystem.This comparative study surveyed macrobenthos from hypoxic and non-hypoxic areas of the Zhujiang(Pearl)River Estuary(PRE),and explores the ef...Macrobenthos can serve as an indicator of hypoxia in the estuarine ecosystem.This comparative study surveyed macrobenthos from hypoxic and non-hypoxic areas of the Zhujiang(Pearl)River Estuary(PRE),and explores the effects of environmental factor on the macrobenthos community structure.In July 2020,49 macrobenthos species were collected from the hypoxic area,contrasting with 91 species found in the non-hypoxic area.July 2021 recorded 51 species in the hypoxic area and 76 in the non-hypoxic area.Analysis of similarities(ANOSIM)and non-metric multidimentional scaling(NMDS)showed no significant difference in the macrobenthos community structure between the two areas.However,Polychaeta displays higher species richness,abundance,and biomass in the hypoxic zone,negatively correlating to dissolved oxygen(DO).Canonical correspondence analysis(CCA)also showed that the abundance of Polychaeta was negatively correlated with that of Crustacea.Interestingly,despite the differences in Polychaeta,macrobenthos community structure remains stable between hypoxic and non-hypoxic samples.This study suggests Polychaeta’s potential adaptation to hypoxic conditions in the PRE’s hypoxic area.Finally,Spearman correlation analysis showed that DO have a significant negative correlation with total phosphorus(TP),total nitrogen(TN)and total organic carbon(TOC)in the PRE,indicating that water eutrophication would exacerbate the occurrence of hypoxia.展开更多
Nitrification,the process by which ammonia is oxidized to nitrite(ammonia oxidation,AO)and subsequently to nitrate(nitrite oxidation,NO),plays a critical role in the nitrogen cycle by linking the oxidized and reduced ...Nitrification,the process by which ammonia is oxidized to nitrite(ammonia oxidation,AO)and subsequently to nitrate(nitrite oxidation,NO),plays a critical role in the nitrogen cycle by linking the oxidized and reduced forms of nitrogen.This process consumes dissolved oxygen,releases protons,and produces the potent greenhouse gas nitrous oxide(N2O),rendering it highly relevant to various environmental challenges,especially in coastal seas with high anthropogenic nitrogen input.Despite its importance,research has predominantly focused on AO,with fewer studies simultaneously investigating ammonia oxidation rates(AOR)and nitrite oxidation rates(NOR).This study measured AOR and NOR using the 15N tracer technique in the Changjiang(Yangtze)River Estuary(CRE)during the summer of 2022,a season when bottom-water hypoxia occurred frequently.Overall,our findings showed that AOR exceeded NOR across different estuarine conditions.Specifically,higher ammonium and total suspended matter(TSM)concentrations significantly boosted AOR.Notably,despite lower TSM levels compared to previous studies,AOR remained high,suggesting that smaller particles may offer more surface area for ammonia-oxidizing microorganisms.In addition,surface productivity,indicated by the concentration of chlorophyll a(Chl a),was positively correlated with bottom-water nitrification and oxygen consumption.This suggested that increased surface productivity could enhance deep-water microbial nitrification,intensifying oxygen demand and promoting hypoxia,particularly during summer stratification when vertical oxygen replenishment was limited.These findings underscored the complex coupling between particle dynamics,primary production,and microbial nitrogen transformations,and offered important insights for hypoxia mitigation and estuarine ecosystem management.展开更多
Oyster aquaculture farm(OAF)with dense wooden stakes,one of the prevalent large-scale marine culture facilities in estuaries,has the potential to influence estuarine hydrodynamics,sediment dynamics,geomorphological ev...Oyster aquaculture farm(OAF)with dense wooden stakes,one of the prevalent large-scale marine culture facilities in estuaries,has the potential to influence estuarine hydrodynamics,sediment dynamics,geomorphological evolution,and sustainable development.This study investigated these impacts in the Moyang River Estuary(Guangdong Province,China)by combining a two-dimentional coupled current-wave-sediment numerical model with field observations based on the TELEMAC-MASCARET numerical simulation system.The wooden stakes of OAF were represented as rigid cylinders in the model,and key parameters were calibrated through field observations,including stake diameter(0.1 m),spacing(3 m),height(6 m),and drag coefficient.Simulations comparing scenarios with and without OAF quantified the responses of sediment dynamics to estuarine OAF.Tidal currents in the channel were strengthened,with velocity increased by 20%-70%,while currents within the OAF weakened,with the maximum reduction exceeding 0.45 m/s.Significant wave height rapidly attenuated within OAF,with the wave attenuation coefficient exceeding 50%.Concurrently,due to the effects of stronger ebb dynamics caused by OAF,sediments in the channel were eroded,inducing a larger rate of seaward residual transport over a tidal cycle.Additionally,more sediments in the middle bar were resuspended,promoting the formation of a high-concentration zone of suspended sediment(estuarine turbidity maximum)during the ebb period.These changes in sediment dynamics caused by OAF significantly influenced the geomorphological evolution of the mouth bar,driving seaward channel extension and deepening,while causing progressive vertical accretion and lateral expansion in the top and outer slope of the middle bar.Sediment resuspension and redistribution within the mouth bar facilitated net transport and redeposition along the OAF periphery.Furthermore,it is crucial to appropriately increase the stakes spacing in the management of oyster farms to ensure a stable flow of water within the OAF.These findings provide a transferable framework for investigating sediment dynamics and a scientific basis for evaluating marine aquaculture practices in other estuaries with OAF or similar anthropogenic structures worldwide.展开更多
Pollution of transboundary rivers can result from anthropogenic activities in their watersheds.In this study,sediment traps were deployed to determine the fluxes,concentrations,and health risks associated with arsenic...Pollution of transboundary rivers can result from anthropogenic activities in their watersheds.In this study,sediment traps were deployed to determine the fluxes,concentrations,and health risks associated with arsenic,cadmium,mercury,lead,and iron in the estuaries of three transboundary rivers(Comoé,Bia,and Tanoé)in West Africa.Thus,the analysis of metal-associated sedimentation particle samples collected in rainy,flood,and dry seasons was required.Sediment traps were used to calculate the metal fluxes associated with sedimentation particles towards the Atlantic Ocean.Finally,the carcinogenic and non-carcinogenic risks of ingestion and dermal contact associated with sedimentation particles were assessed.The results showed that the total concentrations of trace metals in particulate matter were higher than in the UCC(Upper Crust Continental),with the exception of lead.The highest fluxes of lead,mercury,iron and arsenic associated with sedimented particles were observed during flood periods in the estuary of the Comoé,Bia and Tanoérivers.Cadmium fluxes associated with sedimentation particles were highest in the rainy season in the Bia and Comoéestuaries and in the flood season in the Tanoéestuary.Pearson’s correlation analysis and the enrichment factor showed that the trace metals were derived from anthropogenic activities such as mining and farming.In addition,contamination indices showed that sediment particles in the estuaries of the three rivers were severely contaminated with mercury.However,the results of potential human health risks associated with trace metals show that there is no probability of exposure of the community to harmful and carcinogenic effects through ingestion and dermal absorption of sediment particles.It is essential to integrate the information from this study into policy-and decision-making processes for better management of transboundary river water resources in coastal countries,particularly the Côte d’Ivoire.展开更多
The turbidity maximum zone(TMZ)is a distinctive aquatic environment marked by consistently higher turbidity compared to upstream and downstream section.In the TMZ,physicochemical properties such as intense light limit...The turbidity maximum zone(TMZ)is a distinctive aquatic environment marked by consistently higher turbidity compared to upstream and downstream section.In the TMZ,physicochemical properties such as intense light limitation,abundant nutrients,and rapid salinity shifts play a crucial role in shaping phytoplankton dynamics.The Qiantang River estuary-Hangzhou Bay(QRE-HZB)is a macrotidal estuary system known for its exceptionally high suspended solids concentration.To investigate the impact of TMZ on the standing crop and size structure of phytoplankton in the QRE-HZB,we conducted three cruises in dry,wet,and dry-to-wet transition seasons during 2022-2023,by assessing parameters including size fractionated chlorophyll a(chl a),turbidity,Secchi depth,temperature,salinity,nutrients,and mesozooplankton.Results reveal significant variations in the TMZ and associated environmental factors in different periods,which markedly influenced the phytoplankton chl-a concentration,size structure,and cell activity(pheophytin/chl a).The chl-a concentration was high with micro-phytoplankton predominance in wet season,while nano-phytoplankton dominated in dry season.Within the TMZ,lower chl-a concentrations and pico-chl-a contributions,alongside higher pheophytin/chl-a and micro-chl-a contributions,were observed.The Spearman’s rank correlation and generalized additive model analyses indicated strong correlations of chl-a concentrations with turbidity,nutrients,and mesozooplankton.Redundancy analysis further revealed that salinity,nutrients,and turbidity significantly regulated variations in size structure.Phytoplankton mortality within the TMZ was primarily driven by high turbidity and salinity fluctuations,reflecting the vigorous resuspension and mixing of freshwater and seawater in the QRE-HZB.These findings highlight that the standing crop and size structure of phytoplankton were strongly regulated by the TMZ and associated physicochemical factors in the macrotidal QRE-HZB.展开更多
Global warming underscores the urgent need to enhance carbon sinks to mitigate climate change,yet the role of coastal shellfish aquaculture area as either carbon sinks or sources remains unclear.In this study,we condu...Global warming underscores the urgent need to enhance carbon sinks to mitigate climate change,yet the role of coastal shellfish aquaculture area as either carbon sinks or sources remains unclear.In this study,we conducted high-resolution profiling observations of CO_(2)dynamics and net community production(NCP)in a mussel farm located in the Changjiang(Yangtze)River estuary(CRE)during early autumn.Results indicate that the partial pressure of CO_(2)(pCO_(2))in the water column was consistently higher than the atmospheric level,averaging 74.75±2.44 Pa,signaling that the mussel farm acted as a CO_(2)source.The average air-water CO_(2)exchange flux(FCO_(2))averaged-1.91±1.16 mmol/(m^(2)·h),and NCP in the water column(NCPCOL)averaged-6.66±12.81 mmol/(m^(2)·h),revealing a heterotrophic condition.A significant inverse correlation was found between NCPCOLand sea surface pCO_(2)with a lag time of approximately 3.31 h,highlighting the influence of biological activity in modulating CO_(2)dynamics.Physical processes such as freshwater inputs,vertical mixing,and wind patterns,also played a crucial role in shaping pCO_(2)variations.The study emphasizes the complexity of CO_(2)dynamics in costal aquaculture areas and the need for long-term,high-resolution monitoring to better understand their contribution to climate change mitigation.The high-resolution profiling system provided novel insights into the dynamics of NCP and CO_(2)fluxes,showing its potential as an advanced tool for studying aquaculture systems.Future research should focus on expanding the geographic and temporal scope of studies,combining observational and modeling approaches to better predict the responses of aquaculture systems to environmental changes.展开更多
Oyster farming provides substantial ecological and economic benefits but is often constrained by the challenges of selecting suitable sites in dynamic coastal environments.This study presents a tailored oyster suitabi...Oyster farming provides substantial ecological and economic benefits but is often constrained by the challenges of selecting suitable sites in dynamic coastal environments.This study presents a tailored oyster suitability index(OSI)for the Zhujiang(Pearl)River Estuary(PRE),developed using Landsat satellite imagery and in situ observations collected from 2013 to 2023.Key environmental parameters,including sea surface temperature(SST),salinity,turbidity,and chlorophyll-a(Chl-a)concentration,were integrated for OSI retrieval.Optimal algorithms for each parameter were identified through evaluation using field measurements,yielding high accuracy,as evidenced by strong determination coefficients(R^(2))and low root mean square error(RMSE):R^(2)=0.98,RMSE=0.74℃for SST;R^(2)=0.94,RMSE=0.50 for salinity;R^(2)=0.95,RMSE=1.21 mg/m^(3)for Chl-a;R^(2)=0.91,RMSE=1.48 NTU for turbidity.The OSI revealed pronounced seasonal and spatial variability,with the highest suitability observed during winter and the lowest during summer.Validation results demonstrated strong alignment between OSI predictions and existing oyster farming zones.These findings underscore the value of remote sensing for scalable,near-real-time aquaculture site assessments.The OSI framework provides a robust decision-support tool for optimizing oyster cultivation,promoting sustainable aquaculture development in dynamic estuarine systems such as the PRE and beyond.展开更多
The compositions and distributions of monoterpenes,isoprene,aromatics and sesquiterpene SOA tracers(SOAM,SOAI,SOAA and SOAS,respectively)at an island site(Da Wan Shan Island,DWS)were investigated in the context of the...The compositions and distributions of monoterpenes,isoprene,aromatics and sesquiterpene SOA tracers(SOAM,SOAI,SOAA and SOAS,respectively)at an island site(Da Wan Shan Island,DWS)were investigated in the context of the influence of continental and marine air masses over the Pearl River Estuary(PRE)region in winter 2021.The sum concentration of SOA tracers was 6.2–132.8 ng m^(−3),with SOAM and SOAI as the main components in both continental(scenarios A1 and A2)and marine air masses(scenario A3),as well as their combination(scenario A4).The highest and lowest levels of SOAM were observed in A1 and A3,respectively,which were mainly related to the variations in meteorological conditions,precursor concentrations,and the degree of photochemical processes.Higher MBTCA/HGA(3-methyl-1,2,3-butanetricarboxylic acid/3-hydroxyglutaric acid)ratios suggested a less significant contribution fromα-pinene to SOAM.The variations of SOAI in the different scenarios were associated with differences in relative humidity,particle acidity,and isoprene/NOx ratios.The respective highest and lowest concentrations of aromatics SOA tracers in A1 and A3 revealed the influence of anthropogenic precursors from upwind continental areas,which was confirmed by the correlation among biogenic and anthropogenic precursors.The results of the tracer-based-method suggested dominant contributions of SOAs from aromatics and monoterpenes,with the highest concentrations in A1.A WRF-Chem simulation revealed that the SOAs from the above precursors only contributed 12%–25%to the total SOA at DWS,while the spatial distributions of SOAs further highlighted that the abundance of SOAs over the PRE region in winter is highly associated with air masses transported from upwind continental areas.展开更多
Mangrove forests are critical ecosystems for carbon sequestration,effectively capturing atmospheric carbon and permanently storing soil organic carbon(SOC)in coastal wetlands.Recent restoration and afforestation initi...Mangrove forests are critical ecosystems for carbon sequestration,effectively capturing atmospheric carbon and permanently storing soil organic carbon(SOC)in coastal wetlands.Recent restoration and afforestation initiatives have been undertaken to mitigate the rising atmospheric CO_(2) concentrations along tropical ocean coasts worldwide.The expansion of mangrove forests has garnered significant attention for elucidating their contributions to the permanent storage of carbon in both surface and subsoil layers.In this study,we investigated a recently expanding mangrove forest in the Beilun River Estuary of Guangxi Province,focusing on the abundance and sources of organic carbon(OC)in surface sediments.We also analyzed sediment grain size distribution,SOC,total nitrogen(TN)content,and stable carbon isotope composition(δ^(13)C).Additionally,we determined the molar ratio of SOC to nitrogen(C/N).The SOC content ranged from 0.25%to 6.58%,the C/N ratio varied from 9.85 to 17.73,δ^(13)C values spanned from-29.58‰to-24.93‰,andδ^(15)N values ranged from 3.10‰to 7.36‰.A strong correlation was observed between SOC and TN content.However,particle size did not significantly influence these relationships.In terms of SOC sources in the sediments,contributions from mangrove,terrestrial,and marine sources accounted for 37.1%to 99.5%,0.5%to 47.4%,and 0%to 17.6%,respectively.The findings of this study provide essential insights for evaluating and managing carbon sinks within the mangrove ecosystems of the Beibu Gulf region,contributing to more effective carbon management strategies in coastal areas.展开更多
The Changjiang River Estuary(CRE) and its offshore plumes host a diverse phytoplankton community;however, the spatiotemporal dynamics of these microorganisms and their environmental drivers remain poorly understood. T...The Changjiang River Estuary(CRE) and its offshore plumes host a diverse phytoplankton community;however, the spatiotemporal dynamics of these microorganisms and their environmental drivers remain poorly understood. This study aims to elucidate the spatiotemporal variations and environmental heterogeneity of phytoplankton communities in the CRE, as well as to understand the factors driving their assemblage. Utilizing ecological survey data collected from the CRE and adjacent waters during spring and summer from 2018 to 2020, we conducted a spatiotemporal analysis of phytoplankton β-diversity in the region. We decomposed β-diversity into species contributions to β-diversity(SCBD)and local contributions to β-diversity(LCBD) to examine spatial differences in phytoplankton diversity and the contributions of individual species within the community. Our findings reveal that spatial differences, primarily driven by water salinity and distance from the coastline, are key factors influencing the heterogeneity of phytoplankton community composition. Key species such as Skeletonema costatum, Melosira granulata, and M. granulata var.angustissima significantly affected β-diversity. Further, β-diversity decomposition reveals that community assembly is driven by interactive biogeochemical forces: salinity gradients shape spatial heterogeneity through runoff-seawater mixing, eutrophic conditions promote the dominance of nutrient-dependent taxa, and silica availability regulates diatom-to-flagellate succession. This study provides a methodological paradigm for analyzing phytoplankton community assembly mechanisms in estuaries, thereby offering scientific support for biogeography-based ecosystem management in the CRE.展开更多
The exchange flow structure was examined in the North Passage of Changjiang River Estuary,where a deep waterway project(DWP)was carried out to improve the navigability.Before the construction of the DWP,the friction e...The exchange flow structure was examined in the North Passage of Changjiang River Estuary,where a deep waterway project(DWP)was carried out to improve the navigability.Before the construction of the DWP,the friction effect played a significant role in shaping the transverse structure of the exchange flow.The turbulent eddy viscosity generated near the seabed can be transferred to the upper water column,which facilitated vertical momentum exchange.As a result,the landward inflow extended to–2 m below the water surface and the seaward outflow was concentrated on the shallow shoal on the southern side of the cross section.After the construction of the DWP,the turbulent mixing was suppressed as a result of density stratification.The friction felt by the water was constrained in the lower half of the water column and the vertical momentum exchange was reduced.Meanwhile,the channel became dynamically narrowed with a Kelvin number of 0.52.Therefore,the Coriolis played a minor role in shaping the transverse structure of the exchange flow.As a consequence,the exchange flow featured a vertically-sheared pattern,with outflow at the surface and inflow underneath.Additionally,the gravitational circulation was enhanced due to increase in along-channel density gradient and stratification.The exchange flow components associated with the lateral processes(residual currents induced by eddy viscosityshear covariance and lateral advective acceleration)were reduced,which suggests that lateral processes played a minor role in modifying the along-channel dynamics when the estuary becomes dynamically-narrowed.展开更多
The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen conce...The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.展开更多
The river plume front between the diluted ocean water and salty ocean water in the Changjiang(Yangtze)River Delta(CRD)is well studied.Comparatively,less is known about the estuarine front in the CRD,which is formed be...The river plume front between the diluted ocean water and salty ocean water in the Changjiang(Yangtze)River Delta(CRD)is well studied.Comparatively,less is known about the estuarine front in the CRD,which is formed between the riverine freshwater and the diluted ocean water and has the highest magnitude of salinity gradient(SG)in the CRD.Estuarine fronts are of great significance to the riverine material transport in the estuary.Many biogeochemical processes are enhanced in estuarine fronts,which have brought about environmental problems.In this study,the seasonal variations of the estuarine fronts in the CRD were studied in wet(July)and dry(January)seasons in 2017,based on model simulations with high spatiotemporal resolutions using the Finite-Volume Community Ocean Model(FVCOM).The estuarine front included several sharp fronts with a SG>4(/500 m),and was bottom-trapped on the submerged delta front.Seasonal changes mainly occurred off the Jiangsu coast,where a significant estuarine front was formed in July.The estuarine fronts generated around the submerged delta topography were accompanied by the offshore extension of older estuarine fronts,which were diluted and evolved into plume fronts over a tidal cycle.The simulated estuarine fronts had a salinity range of 6 to 22 in the dry season and 6 to 14 in wet season 2017.The estuarine fronts hindered the residual current by altering its flow direction to the southeast.展开更多
Sewage introduction into rivers has altered the physical and chemical properties of waters and also the microbial metabolism. This study aimed to evaluate the Escherichia coli and nutrient concentrations in the Maratu...Sewage introduction into rivers has altered the physical and chemical properties of waters and also the microbial metabolism. This study aimed to evaluate the Escherichia coli and nutrient concentrations in the Maratuãand Crumaú rivers (Santos Estuary, Brazil) during two periods with distinct magnitudes of freshwater runoff, verifying possible relation of abiotic changes with the microbial metabolism. Water sampling was performed in October/2012 (dry season) and January/2013 (rainy season) at two points in the Crumaú river (upstream and downstream zone) and one in the Maratuãriver (downstream zone). The water subsamples were obtained for E. coli and nutrient analyses while the velocity of water flow, water level, temperature, salinity, and dissolved oxygen were measured in situ. The E. coli concentrations were under the detection limit in the Maratuãdownstream during the dry season reaching a maximum value (1.47 × 10<sup>4</sup> CFU/100mL) in the Crumaú upstream during the rainy season. E. coli presented strong positive correlation with nutrients (ammoniacal-N and phosphate), evidencing the sewage source in the Crumaú upstream shown by this association. In both periods, the low oxygen saturation (100 μmol·L<sup>-1</sup>) indicated considerable predominance of heterotrophic metabolism in the Crumaú upstream. The low dissolved oxygen values in Crumaú River are corroborated to show a low self-depuration capacity in the rainy period due to maintenance of high nutrient and E. coli at two points in the Crumaú river (upstream and downstream zone) and one in the Maratuãriver (downstream zone). Besides, these results evidenced that the tendency of the metabolism changed from autotrophic to heterotrophic under high river flow events at this studied estuarine sector located at Santos estuarine complex.展开更多
基金National Natural Science Foundation of China(42192552,42475011)。
文摘Typhoons are strong air–sea interactions that significantly affect the physical and biogeochemical processes of the upper ocean. Based on the Regional Ocean Modeling System-Carbon–Silicate–Nitrate Ecosystem coupled model, the influence of Typhoon Bolaven(2012) on physical and ecological variables in the East China Sea and the underlying mechanisms were investigated. The results showed that the typhoon induced intense vertical mixing in the upper ocean,leading to sea surface cooling, increased salinity, nutrient concentrations, and phytoplankton blooms. Conversely, warming,reduced salinity, and decreased nutrient concentrations occurred in the subsurface layer. In the Yangtze River Estuary, the passage of typhoons effectively affected wind and current directions, shaping the dipole distribution patterns of the environmental elements. Diagnostic analysis indicated that tropical cyclone-induced horizontal advection is key in driving changes in both the physical and ecological variables within the estuary region. This study provides novel insights into the physical-ecological coupling processes and driving mechanisms governing oceanic environmental changes during typhoon events, particularly in the waters adjacent to the Yangtze River Estuary.
基金supported by the National Basic Research Program of China (No. 2002CB412504)
文摘Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary. Concentrations of dissolved organic carbon （DOC） and dissolved inorganic carbon （DIC） in the Yellow River during dry seasons were higher than those during wet seasons. The effective concentrations of DOC （CDOC＊） were higher than the observed DOC at zero salinity. This input of DOC in the Yellow River estuary was due to sediment desorption processes in low salinity regions. In contrast to DOC, the effective concen- trations of DIC were 10% lower than the DIC measured at freshwater end, and the loss of DIC was caused by CaCO3 precipitation in low salinity region, Particulate organic carbon （POC） and particulate inorganic carbon （PIC） contents of the particles stabilized to constant values （0.5%：t：0.05% and 1.8%--0.2%, respectively） within the turbidity maximum zone （TMZ） and showed no noticeable seasonal variations. A rapid drop of PIC and rise of POC occurred simultaneously outside the TMZ due to an intense dilution of riv- erine inorganic-rich particles being transported into a pool of aquatic organic-poor particles outside the TMZ. Annually, the Yellow River transported 6.95× 10^5 t of DIC, 0.64× 10^5 t of DOC, 78.58× 10^5 t of PIC and 2.29× 10^5 t of POC to the sea.
基金National Natural Science Foundation of China,No.41906148,No.42271086Rejuvenating Yunnan Talents Support Plan Young Talent Program,No.XDYC-QNRC-2023-0322。
文摘A macro-tidal tropical estuary with high fluvial discharge is characterized by both fragility and remarkable dynamism.This study utilizes the Salween River Delta(SRD)as a case example to examine the interplay between morphology and vegetation under similar tidal conditions.Our analysis of correlations and inferences revealed several significant trends in the SRD:(1)an overall expansion of land area and intertidal vegetation,with the most pronounced changes occurring in the eastern sector;(2)the predominance of river discharge influencing the southwestern and northern sectors,contrasted with the primary impact of storm surges in the eastern sector;and(3)three distinct causal relationships among estuarine morphology,vegetation,storm surges,and river discharge:a direct model where river discharge shapes estuarine morphology,a progressive model in which river discharge affects vegetation distribution,subsequently influencing estuarine morphology,and a hybrid model where storm surges directly impact vegetation and indirectly modify its distribution through changes in estuarine morphology.The stability of sediment supply and the role of intertidal vegetation are crucial for the continuous seaward advance,providing a vital foundation for the protection and development of estuarine deltas.
基金Under the auspices of Key Program of the National Natural Science Foundation of China(No.U2006215,U1806218)the National Key R&D Program of China(No.2017YFC0505902)。
文摘Spartina alterniflora invasions seriously threaten the structure and functions of coastal wetlands in China.In this study,the Suaeda salsa community in the Yellow River Estuary wetland was monitored using long-term Landsat satellite images acquired from 1997 to 2020 to quantify the impact of changes in hydrological connectivity induced by S.alterniflora on neighboring vegetation com-munities.The results showed that S.alterniflora rapidly expanded in the estuary area at a rate of 4.91 km^(2)/yr from 2010 to 2020.At the same time,the hydrological connectivity of the area and the distribution of S.salsa changed significantly.Small tidal creeks dominated the S.alterniflora landscape.The number of tidal creeks increased significantly,but their average length decreased and they tended to develop in a horizontal tree-like pattern.Affected by the changes in hydrological connectivity due to the S.alterniflora invasion,the area of S.salsa decreased by 41.1%,and the degree of landscape fragmentation increased from 1997 to 2020.Variations in the Largest Patch Index(LPI)indicated that the S.alterniflora landscape had become the dominant landscape type in the Yellow River Estuary.The res-ults of standard deviation ellipse(SDE)and Pearson’s correlation analyses indicated that a well-developed hydrological connectivity could promote the maintenance of the S.salsa landscape.The degradation of most S.salsa communities is caused by the influence of S.alterniflora on the morphological characteristics of the hydrological connectivity of tidal creek systems.
基金The National Natural Science Foundation of China under contract No.51409286the Scientific Research Innovation Project of Jiangsu Province Ordinary University Graduate Student under contract No.CXZZ12_0223the Open Fund Project of Zhujiang River Water Resources Commission of the Zhujiang River Water Conservancy Science Research Institute under contract No.[2013]KJ02
文摘Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process.Based on prediction of sea level rise over the 21st century,the Zhujiang(Pearl River)Estuary was chosen as a prototype to study the responses of the estuary to potential sea level rise.The numerical model results show that the average salt content,saltwater intrusion distance,and stratification will increase as the sea level rises.The changes of these parameters have obvious seasonal variations.The salt content in the Lingdingyang shows more increase in April and October(the transition periods).The saltwater intrusion distance has larger increase during the low-flow periods than during the highflow periods in the Lingdingyang.The result is just the opposite in Modaomen.The stratification and its increase are larger during the low-flow periods than during the high-flow periods in Lingdingyang.The response results of transport processes to sea level rise demonstrate that:(1)The time of vertical transport has pronounced increase.The increased tidal range and currents would reinforce the vertical mixing,but the increased stratification would weaken the vertical exchange.The impact of stratification changes overwhelms the impact of tidal changes.It would be more difficult for the surface water to reach the bottom.(2)The lengthways estuarine circulation would be strengthened.Both the offshore surface residual current and inshore bottom residual current will be enhanced.The whole meridional resident flow along the transect of the Lingdingyang would be weakened.These phenomena are caused by the decrease of water surface slope(WWS)and the change of static pressure with the increase of water depth under sea level rise.
基金supported by the Yantai City Science and Technology Innovation Development Plan Project(Nos.2023JCYJ097 and 2023JCYJ094)the Key Project of the National Natural Science Foundation of China(No.42330406).
文摘As China’s second longest river,the Yellow River(YR)carries a large volume of fresh water into the Bohai Sea with abundant nutrients and,thus,plays a crucial role in regulating the temperature and salinity near the YR Delta.In this study,using the runoff data and the Finite Volume Community Ocean Model,we simulated the salinity distribution near the YR Estuary for 2013-2022.We investigated the effect of the YR runoff on salinity dispersion and established the relationship between salinity distribution and the river’s runoff volume.Additionally,we analyzed the relationship between fish eggs and salinity distribution using fish egg da-ta.Findings indicated that the freshwater discharged from the YR converged into Laizhou Bay under the influence of tide.The sever-al years of simulation results(2013-2022)showed that the salinity field near the YR Estuary changed with the variations of river runoff entering the sea.Simultaneously,we found a positive correlation between the area of low-salinity zones(below 27)and the monthly average river runoff,and this relation could be expressed as Y_(s)=0.7457X_(r)+78.904.The characteristics of fish egg distribution revealed that fish eggs were primarily distributed in the areas characterized by salinity in the range of 25-29.
基金The Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311021004the Biodiversity Assessment of Key Marine Habitat in China under contract Nos PM-zx555-202107-208 and PM-zx555-202106-195.
文摘Macrobenthos can serve as an indicator of hypoxia in the estuarine ecosystem.This comparative study surveyed macrobenthos from hypoxic and non-hypoxic areas of the Zhujiang(Pearl)River Estuary(PRE),and explores the effects of environmental factor on the macrobenthos community structure.In July 2020,49 macrobenthos species were collected from the hypoxic area,contrasting with 91 species found in the non-hypoxic area.July 2021 recorded 51 species in the hypoxic area and 76 in the non-hypoxic area.Analysis of similarities(ANOSIM)and non-metric multidimentional scaling(NMDS)showed no significant difference in the macrobenthos community structure between the two areas.However,Polychaeta displays higher species richness,abundance,and biomass in the hypoxic zone,negatively correlating to dissolved oxygen(DO).Canonical correspondence analysis(CCA)also showed that the abundance of Polychaeta was negatively correlated with that of Crustacea.Interestingly,despite the differences in Polychaeta,macrobenthos community structure remains stable between hypoxic and non-hypoxic samples.This study suggests Polychaeta’s potential adaptation to hypoxic conditions in the PRE’s hypoxic area.Finally,Spearman correlation analysis showed that DO have a significant negative correlation with total phosphorus(TP),total nitrogen(TN)and total organic carbon(TOC)in the PRE,indicating that water eutrophication would exacerbate the occurrence of hypoxia.
基金The Hainan Provincial Natural Science Foundation of China under contract No.423RC438the Major Science and Technology Plan of Hainan Province under contract No.ZDKJ2021008+1 种基金the National Natural Science Foundation of China under contract Nos 42406041,92251306,42266002,41806062,and 42476032the Open Research Fund of Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention under contract No.GPKLMD2023004.
文摘Nitrification,the process by which ammonia is oxidized to nitrite(ammonia oxidation,AO)and subsequently to nitrate(nitrite oxidation,NO),plays a critical role in the nitrogen cycle by linking the oxidized and reduced forms of nitrogen.This process consumes dissolved oxygen,releases protons,and produces the potent greenhouse gas nitrous oxide(N2O),rendering it highly relevant to various environmental challenges,especially in coastal seas with high anthropogenic nitrogen input.Despite its importance,research has predominantly focused on AO,with fewer studies simultaneously investigating ammonia oxidation rates(AOR)and nitrite oxidation rates(NOR).This study measured AOR and NOR using the 15N tracer technique in the Changjiang(Yangtze)River Estuary(CRE)during the summer of 2022,a season when bottom-water hypoxia occurred frequently.Overall,our findings showed that AOR exceeded NOR across different estuarine conditions.Specifically,higher ammonium and total suspended matter(TSM)concentrations significantly boosted AOR.Notably,despite lower TSM levels compared to previous studies,AOR remained high,suggesting that smaller particles may offer more surface area for ammonia-oxidizing microorganisms.In addition,surface productivity,indicated by the concentration of chlorophyll a(Chl a),was positively correlated with bottom-water nitrification and oxygen consumption.This suggested that increased surface productivity could enhance deep-water microbial nitrification,intensifying oxygen demand and promoting hypoxia,particularly during summer stratification when vertical oxygen replenishment was limited.These findings underscored the complex coupling between particle dynamics,primary production,and microbial nitrogen transformations,and offered important insights for hypoxia mitigation and estuarine ecosystem management.
基金The Yangjiang Waterway Affairs Center of Guangdong Province Program under contract No.HLSJCG-20220103the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Program under contract No.SML2023SP220.
文摘Oyster aquaculture farm(OAF)with dense wooden stakes,one of the prevalent large-scale marine culture facilities in estuaries,has the potential to influence estuarine hydrodynamics,sediment dynamics,geomorphological evolution,and sustainable development.This study investigated these impacts in the Moyang River Estuary(Guangdong Province,China)by combining a two-dimentional coupled current-wave-sediment numerical model with field observations based on the TELEMAC-MASCARET numerical simulation system.The wooden stakes of OAF were represented as rigid cylinders in the model,and key parameters were calibrated through field observations,including stake diameter(0.1 m),spacing(3 m),height(6 m),and drag coefficient.Simulations comparing scenarios with and without OAF quantified the responses of sediment dynamics to estuarine OAF.Tidal currents in the channel were strengthened,with velocity increased by 20%-70%,while currents within the OAF weakened,with the maximum reduction exceeding 0.45 m/s.Significant wave height rapidly attenuated within OAF,with the wave attenuation coefficient exceeding 50%.Concurrently,due to the effects of stronger ebb dynamics caused by OAF,sediments in the channel were eroded,inducing a larger rate of seaward residual transport over a tidal cycle.Additionally,more sediments in the middle bar were resuspended,promoting the formation of a high-concentration zone of suspended sediment(estuarine turbidity maximum)during the ebb period.These changes in sediment dynamics caused by OAF significantly influenced the geomorphological evolution of the mouth bar,driving seaward channel extension and deepening,while causing progressive vertical accretion and lateral expansion in the top and outer slope of the middle bar.Sediment resuspension and redistribution within the mouth bar facilitated net transport and redeposition along the OAF periphery.Furthermore,it is crucial to appropriately increase the stakes spacing in the management of oyster farms to ensure a stable flow of water within the OAF.These findings provide a transferable framework for investigating sediment dynamics and a scientific basis for evaluating marine aquaculture practices in other estuaries with OAF or similar anthropogenic structures worldwide.
文摘Pollution of transboundary rivers can result from anthropogenic activities in their watersheds.In this study,sediment traps were deployed to determine the fluxes,concentrations,and health risks associated with arsenic,cadmium,mercury,lead,and iron in the estuaries of three transboundary rivers(Comoé,Bia,and Tanoé)in West Africa.Thus,the analysis of metal-associated sedimentation particle samples collected in rainy,flood,and dry seasons was required.Sediment traps were used to calculate the metal fluxes associated with sedimentation particles towards the Atlantic Ocean.Finally,the carcinogenic and non-carcinogenic risks of ingestion and dermal contact associated with sedimentation particles were assessed.The results showed that the total concentrations of trace metals in particulate matter were higher than in the UCC(Upper Crust Continental),with the exception of lead.The highest fluxes of lead,mercury,iron and arsenic associated with sedimented particles were observed during flood periods in the estuary of the Comoé,Bia and Tanoérivers.Cadmium fluxes associated with sedimentation particles were highest in the rainy season in the Bia and Comoéestuaries and in the flood season in the Tanoéestuary.Pearson’s correlation analysis and the enrichment factor showed that the trace metals were derived from anthropogenic activities such as mining and farming.In addition,contamination indices showed that sediment particles in the estuaries of the three rivers were severely contaminated with mercury.However,the results of potential human health risks associated with trace metals show that there is no probability of exposure of the community to harmful and carcinogenic effects through ingestion and dermal absorption of sediment particles.It is essential to integrate the information from this study into policy-and decision-making processes for better management of transboundary river water resources in coastal countries,particularly the Côte d’Ivoire.
基金Supported by the National Key Research and Development Program of China(No.2021 YFC 3101702)the Key R&D Program of Zhejiang(No.2022 C 03044)+2 种基金the Scientific Research Fund of the Second Institute of Oceanography,MNR(No.JG 1521)the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography(No.SOEDZZ 2202)the National Program on Global Change and Air-Sea Interaction(Phase Ⅱ)-Hypoxia and Acidification Monitoring and Warning Project in the Changjiang River estuary,and Long-term Observation and Research Plan in the Changjiang River estuary and Adjacent East China Sea(LORCE)Project(No.SZ 2001)。
文摘The turbidity maximum zone(TMZ)is a distinctive aquatic environment marked by consistently higher turbidity compared to upstream and downstream section.In the TMZ,physicochemical properties such as intense light limitation,abundant nutrients,and rapid salinity shifts play a crucial role in shaping phytoplankton dynamics.The Qiantang River estuary-Hangzhou Bay(QRE-HZB)is a macrotidal estuary system known for its exceptionally high suspended solids concentration.To investigate the impact of TMZ on the standing crop and size structure of phytoplankton in the QRE-HZB,we conducted three cruises in dry,wet,and dry-to-wet transition seasons during 2022-2023,by assessing parameters including size fractionated chlorophyll a(chl a),turbidity,Secchi depth,temperature,salinity,nutrients,and mesozooplankton.Results reveal significant variations in the TMZ and associated environmental factors in different periods,which markedly influenced the phytoplankton chl-a concentration,size structure,and cell activity(pheophytin/chl a).The chl-a concentration was high with micro-phytoplankton predominance in wet season,while nano-phytoplankton dominated in dry season.Within the TMZ,lower chl-a concentrations and pico-chl-a contributions,alongside higher pheophytin/chl-a and micro-chl-a contributions,were observed.The Spearman’s rank correlation and generalized additive model analyses indicated strong correlations of chl-a concentrations with turbidity,nutrients,and mesozooplankton.Redundancy analysis further revealed that salinity,nutrients,and turbidity significantly regulated variations in size structure.Phytoplankton mortality within the TMZ was primarily driven by high turbidity and salinity fluctuations,reflecting the vigorous resuspension and mixing of freshwater and seawater in the QRE-HZB.These findings highlight that the standing crop and size structure of phytoplankton were strongly regulated by the TMZ and associated physicochemical factors in the macrotidal QRE-HZB.
基金Supported by the National Natural Science Foundation of China(Nos.U23A2033,41976154)the Key R&D Program of Zhejiang Province,China(No.2023C03011)+2 种基金the Key R&D Program of Guangxi,China(No.Guike AB22080099)the Science Foundation of Donghai Laboratory(No.DH-2022KF0205)the Bureau of Science and Technology of Zhoushan(No.2022C81006)。
文摘Global warming underscores the urgent need to enhance carbon sinks to mitigate climate change,yet the role of coastal shellfish aquaculture area as either carbon sinks or sources remains unclear.In this study,we conducted high-resolution profiling observations of CO_(2)dynamics and net community production(NCP)in a mussel farm located in the Changjiang(Yangtze)River estuary(CRE)during early autumn.Results indicate that the partial pressure of CO_(2)(pCO_(2))in the water column was consistently higher than the atmospheric level,averaging 74.75±2.44 Pa,signaling that the mussel farm acted as a CO_(2)source.The average air-water CO_(2)exchange flux(FCO_(2))averaged-1.91±1.16 mmol/(m^(2)·h),and NCP in the water column(NCPCOL)averaged-6.66±12.81 mmol/(m^(2)·h),revealing a heterotrophic condition.A significant inverse correlation was found between NCPCOLand sea surface pCO_(2)with a lag time of approximately 3.31 h,highlighting the influence of biological activity in modulating CO_(2)dynamics.Physical processes such as freshwater inputs,vertical mixing,and wind patterns,also played a crucial role in shaping pCO_(2)variations.The study emphasizes the complexity of CO_(2)dynamics in costal aquaculture areas and the need for long-term,high-resolution monitoring to better understand their contribution to climate change mitigation.The high-resolution profiling system provided novel insights into the dynamics of NCP and CO_(2)fluxes,showing its potential as an advanced tool for studying aquaculture systems.Future research should focus on expanding the geographic and temporal scope of studies,combining observational and modeling approaches to better predict the responses of aquaculture systems to environmental changes.
基金The Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.SML2021SP308the National Natural Science Foundation of China under contract Nos 42176173 and 42476268+1 种基金the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311020004Guangdong Geographical Science Data Center under contract No.2021B1212100003.
文摘Oyster farming provides substantial ecological and economic benefits but is often constrained by the challenges of selecting suitable sites in dynamic coastal environments.This study presents a tailored oyster suitability index(OSI)for the Zhujiang(Pearl)River Estuary(PRE),developed using Landsat satellite imagery and in situ observations collected from 2013 to 2023.Key environmental parameters,including sea surface temperature(SST),salinity,turbidity,and chlorophyll-a(Chl-a)concentration,were integrated for OSI retrieval.Optimal algorithms for each parameter were identified through evaluation using field measurements,yielding high accuracy,as evidenced by strong determination coefficients(R^(2))and low root mean square error(RMSE):R^(2)=0.98,RMSE=0.74℃for SST;R^(2)=0.94,RMSE=0.50 for salinity;R^(2)=0.95,RMSE=1.21 mg/m^(3)for Chl-a;R^(2)=0.91,RMSE=1.48 NTU for turbidity.The OSI revealed pronounced seasonal and spatial variability,with the highest suitability observed during winter and the lowest during summer.Validation results demonstrated strong alignment between OSI predictions and existing oyster farming zones.These findings underscore the value of remote sensing for scalable,near-real-time aquaculture site assessments.The OSI framework provides a robust decision-support tool for optimizing oyster cultivation,promoting sustainable aquaculture development in dynamic estuarine systems such as the PRE and beyond.
基金supported by the State Key Program of the National Natural Science Foundation of China(Grant Nos.42230701,91644215)the National Natural ScienceFoundation of China(Grant Nos.42122062 and 42307137)+3 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515010852)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.23hytd002)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.SML2023SP218)L.M.acknowledges the Zhuhai Science and Technology Plan Project(Grant No.ZH22036201210115PWC).
文摘The compositions and distributions of monoterpenes,isoprene,aromatics and sesquiterpene SOA tracers(SOAM,SOAI,SOAA and SOAS,respectively)at an island site(Da Wan Shan Island,DWS)were investigated in the context of the influence of continental and marine air masses over the Pearl River Estuary(PRE)region in winter 2021.The sum concentration of SOA tracers was 6.2–132.8 ng m^(−3),with SOAM and SOAI as the main components in both continental(scenarios A1 and A2)and marine air masses(scenario A3),as well as their combination(scenario A4).The highest and lowest levels of SOAM were observed in A1 and A3,respectively,which were mainly related to the variations in meteorological conditions,precursor concentrations,and the degree of photochemical processes.Higher MBTCA/HGA(3-methyl-1,2,3-butanetricarboxylic acid/3-hydroxyglutaric acid)ratios suggested a less significant contribution fromα-pinene to SOAM.The variations of SOAI in the different scenarios were associated with differences in relative humidity,particle acidity,and isoprene/NOx ratios.The respective highest and lowest concentrations of aromatics SOA tracers in A1 and A3 revealed the influence of anthropogenic precursors from upwind continental areas,which was confirmed by the correlation among biogenic and anthropogenic precursors.The results of the tracer-based-method suggested dominant contributions of SOAs from aromatics and monoterpenes,with the highest concentrations in A1.A WRF-Chem simulation revealed that the SOAs from the above precursors only contributed 12%–25%to the total SOA at DWS,while the spatial distributions of SOAs further highlighted that the abundance of SOAs over the PRE region in winter is highly associated with air masses transported from upwind continental areas.
基金The National Natural Science Foundation of China under contract No.42476043the Guangxi Key Research and Development Project under contract No.AB21076016+2 种基金the Scientific Research and Technology Development Project of Qinzhou under contract No.202116623the Natural Science Foundation of Guangxi under contract No.2021GXNSFAA075013the China College Students’Innovation and Entrepreneurship Training Program Project under contract No.S202411607002。
文摘Mangrove forests are critical ecosystems for carbon sequestration,effectively capturing atmospheric carbon and permanently storing soil organic carbon(SOC)in coastal wetlands.Recent restoration and afforestation initiatives have been undertaken to mitigate the rising atmospheric CO_(2) concentrations along tropical ocean coasts worldwide.The expansion of mangrove forests has garnered significant attention for elucidating their contributions to the permanent storage of carbon in both surface and subsoil layers.In this study,we investigated a recently expanding mangrove forest in the Beilun River Estuary of Guangxi Province,focusing on the abundance and sources of organic carbon(OC)in surface sediments.We also analyzed sediment grain size distribution,SOC,total nitrogen(TN)content,and stable carbon isotope composition(δ^(13)C).Additionally,we determined the molar ratio of SOC to nitrogen(C/N).The SOC content ranged from 0.25%to 6.58%,the C/N ratio varied from 9.85 to 17.73,δ^(13)C values spanned from-29.58‰to-24.93‰,andδ^(15)N values ranged from 3.10‰to 7.36‰.A strong correlation was observed between SOC and TN content.However,particle size did not significantly influence these relationships.In terms of SOC sources in the sediments,contributions from mangrove,terrestrial,and marine sources accounted for 37.1%to 99.5%,0.5%to 47.4%,and 0%to 17.6%,respectively.The findings of this study provide essential insights for evaluating and managing carbon sinks within the mangrove ecosystems of the Beibu Gulf region,contributing to more effective carbon management strategies in coastal areas.
基金The program of opening ceremony to select the best candidates of the Key Laboratory of Marine Ecological Monitoring and Restoration Technologies,MNR under contract No. MEMRT2024JBGS01。
文摘The Changjiang River Estuary(CRE) and its offshore plumes host a diverse phytoplankton community;however, the spatiotemporal dynamics of these microorganisms and their environmental drivers remain poorly understood. This study aims to elucidate the spatiotemporal variations and environmental heterogeneity of phytoplankton communities in the CRE, as well as to understand the factors driving their assemblage. Utilizing ecological survey data collected from the CRE and adjacent waters during spring and summer from 2018 to 2020, we conducted a spatiotemporal analysis of phytoplankton β-diversity in the region. We decomposed β-diversity into species contributions to β-diversity(SCBD)and local contributions to β-diversity(LCBD) to examine spatial differences in phytoplankton diversity and the contributions of individual species within the community. Our findings reveal that spatial differences, primarily driven by water salinity and distance from the coastline, are key factors influencing the heterogeneity of phytoplankton community composition. Key species such as Skeletonema costatum, Melosira granulata, and M. granulata var.angustissima significantly affected β-diversity. Further, β-diversity decomposition reveals that community assembly is driven by interactive biogeochemical forces: salinity gradients shape spatial heterogeneity through runoff-seawater mixing, eutrophic conditions promote the dominance of nutrient-dependent taxa, and silica availability regulates diatom-to-flagellate succession. This study provides a methodological paradigm for analyzing phytoplankton community assembly mechanisms in estuaries, thereby offering scientific support for biogeography-based ecosystem management in the CRE.
基金The National Natural Science Foundation of China under contract Nos 51761135021,41576098 and 41980851the Fundamental Research Funds for the Central University under contract No.19LGPY96
文摘The exchange flow structure was examined in the North Passage of Changjiang River Estuary,where a deep waterway project(DWP)was carried out to improve the navigability.Before the construction of the DWP,the friction effect played a significant role in shaping the transverse structure of the exchange flow.The turbulent eddy viscosity generated near the seabed can be transferred to the upper water column,which facilitated vertical momentum exchange.As a result,the landward inflow extended to–2 m below the water surface and the seaward outflow was concentrated on the shallow shoal on the southern side of the cross section.After the construction of the DWP,the turbulent mixing was suppressed as a result of density stratification.The friction felt by the water was constrained in the lower half of the water column and the vertical momentum exchange was reduced.Meanwhile,the channel became dynamically narrowed with a Kelvin number of 0.52.Therefore,the Coriolis played a minor role in shaping the transverse structure of the exchange flow.As a consequence,the exchange flow featured a vertically-sheared pattern,with outflow at the surface and inflow underneath.Additionally,the gravitational circulation was enhanced due to increase in along-channel density gradient and stratification.The exchange flow components associated with the lateral processes(residual currents induced by eddy viscosityshear covariance and lateral advective acceleration)were reduced,which suggests that lateral processes played a minor role in modifying the along-channel dynamics when the estuary becomes dynamically-narrowed.
基金Supported by the Tianjin Key R&D Program(No.21YFSNSN00220)。
文摘The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.
基金Supported by the National Natural Science Foundation of China(No.U2240220)。
文摘The river plume front between the diluted ocean water and salty ocean water in the Changjiang(Yangtze)River Delta(CRD)is well studied.Comparatively,less is known about the estuarine front in the CRD,which is formed between the riverine freshwater and the diluted ocean water and has the highest magnitude of salinity gradient(SG)in the CRD.Estuarine fronts are of great significance to the riverine material transport in the estuary.Many biogeochemical processes are enhanced in estuarine fronts,which have brought about environmental problems.In this study,the seasonal variations of the estuarine fronts in the CRD were studied in wet(July)and dry(January)seasons in 2017,based on model simulations with high spatiotemporal resolutions using the Finite-Volume Community Ocean Model(FVCOM).The estuarine front included several sharp fronts with a SG>4(/500 m),and was bottom-trapped on the submerged delta front.Seasonal changes mainly occurred off the Jiangsu coast,where a significant estuarine front was formed in July.The estuarine fronts generated around the submerged delta topography were accompanied by the offshore extension of older estuarine fronts,which were diluted and evolved into plume fronts over a tidal cycle.The simulated estuarine fronts had a salinity range of 6 to 22 in the dry season and 6 to 14 in wet season 2017.The estuarine fronts hindered the residual current by altering its flow direction to the southeast.
文摘Sewage introduction into rivers has altered the physical and chemical properties of waters and also the microbial metabolism. This study aimed to evaluate the Escherichia coli and nutrient concentrations in the Maratuãand Crumaú rivers (Santos Estuary, Brazil) during two periods with distinct magnitudes of freshwater runoff, verifying possible relation of abiotic changes with the microbial metabolism. Water sampling was performed in October/2012 (dry season) and January/2013 (rainy season) at two points in the Crumaú river (upstream and downstream zone) and one in the Maratuãriver (downstream zone). The water subsamples were obtained for E. coli and nutrient analyses while the velocity of water flow, water level, temperature, salinity, and dissolved oxygen were measured in situ. The E. coli concentrations were under the detection limit in the Maratuãdownstream during the dry season reaching a maximum value (1.47 × 10<sup>4</sup> CFU/100mL) in the Crumaú upstream during the rainy season. E. coli presented strong positive correlation with nutrients (ammoniacal-N and phosphate), evidencing the sewage source in the Crumaú upstream shown by this association. In both periods, the low oxygen saturation (100 μmol·L<sup>-1</sup>) indicated considerable predominance of heterotrophic metabolism in the Crumaú upstream. The low dissolved oxygen values in Crumaú River are corroborated to show a low self-depuration capacity in the rainy period due to maintenance of high nutrient and E. coli at two points in the Crumaú river (upstream and downstream zone) and one in the Maratuãriver (downstream zone). Besides, these results evidenced that the tendency of the metabolism changed from autotrophic to heterotrophic under high river flow events at this studied estuarine sector located at Santos estuarine complex.
