Climate warming and atmospheric nitrogen(N)deposition have profound influences on the terrestrial biosphere.However,how these two global change drivers affect phytoplankton which are important primary producers in wet...Climate warming and atmospheric nitrogen(N)deposition have profound influences on the terrestrial biosphere.However,how these two global change drivers affect phytoplankton which are important primary producers in wetlands with large carbon stocks and complex hydrological fluctuations remain largely unclear.As part of a two-year field experiment in a freshwater wetland,this study was conducted to investigate the effects of nighttime warming and N addition on phytoplankton biomass in the North China Plain.The results showed that neither nighttime warming nor N addition influenced the Shannon-Wiener index of phytoplankton community.Nighttime warming did not change phytoplankton biomass,likely due to the different warming impacts on dominant phyla and in different seasons.Decreased phytoplankton biomass in spring because of the increased water pH and submerged plant coverage was compensated by the enhanced biomass in autumn due to the reduced dissolved oxygen and submerged plant coverage,leading to the neutral change of phytoplankton biomass under warming.Nitrogen addition elevated phytoplankton biomass by 11.6%,which could be attributed to the enhanced nutrient availability and reduced submerged plant coverage.Positive relationships of methane(CH4)emission rates at the water-air interface with phytoplankton biomass indicated the potentially crucial role of phytoplankton in mediating wetland CH4 cycling through photosynthesis-driven metabolisms.The findings suggested the seasonal variation of phytoplankton and their potential responses to nighttime warming and N deposition,which may provide a more accurate basis for assessing the global change-carbon feedback in wetland ecosystems.展开更多
Polynyas and their adjacent seasonal ice zones(SIZs)represent the most productive regions in the Southern Ocean,supporting unique food webs that are highly sensitive to climate change.Understanding the dynamics of phy...Polynyas and their adjacent seasonal ice zones(SIZs)represent the most productive regions in the Southern Ocean,supporting unique food webs that are highly sensitive to climate change.Understanding the dynamics of phytoplankton and the carbon pool in these areas is crucial for assessing the role of the Southern Ocean in global carbon cycling.During the late stage of an algal bloom,seawater samples at 14 stations were collected in the Amundsen Sea Polynya(ASP)and adjacent SIZ.Using nutrients,phytoplankton pigments,organic carbon(OC),remote sensing data,and physicochemical measurements,as well as CHEMTAX model simulations,we investigated the response of the phytoplankton crops,taxonomic composition,and OC pool to environmental factors.Our analyses revealed that hydrodynamic regimes of the polynya,adjacent SIZs and open sea were regulated by the regionally varying intrusion of Circumpolar Deep Water,photosynthetically active radiation and sea ice melt water.The ASP exhibited the highest seasonal nutrient utilization rates[ΔN=(1059±386)mmol/m^(2),ΔP=(50±17)mmol/m^(2) andΔSi=(956±904)mmol/m^(2)],while the open sea had lower rates.The integrated chlorophyll a(Chl a)concentration at depths of 0–200 m ranged from 20.4 mg/m^(2) to 1420.0 mg/m^(2) and peaked in the polynya.In the study area,Haptophytes Phaeocystis antarctica was the dominant functional group(34%±27%),and diatoms acted as a secondary contributor(23%±14%).The major functional group and particulate OC(POC)contributor varied from diatoms(36%±12%)in the open sea to haptophytes(48%±31%)in the polynya waters.Strong light conditions and microelement limitations promoted the dominance of P.antarctica(low Fe forms)dominance in the ASP.The strong correlations between the POC and Chl a depth-integrated concentration suggest that the POC was primarily derived from phytoplankton,while dissolved OC(DOC)was influenced by consumer activity and water mass transport.In addition,the transport of OC in the upper 200 m of the water column within the ASP was quantified,revealing the predominantly westward fluxes for both DOC[9.0 mg/(m^(2)·s)]and POC[7.2 mg/(m^(2)·s)].The latitudinal transport exhibited the northward transport of DOC[8.1 mg/(m^(2)·s)]and southward transport of POC[4.3 mg/(m^(2)·s)]movement.These findings have significant implications for enhancing our understanding of how hydrodynamics influence OC cycling in polynya regions.展开更多
This study systematically examined phytoplankton community structure and its spatial distribution across euphotic and deep-water layers in the northeastern South China Sea(ne-SCS),elucidating their responses to physic...This study systematically examined phytoplankton community structure and its spatial distribution across euphotic and deep-water layers in the northeastern South China Sea(ne-SCS),elucidating their responses to physical processes including eddy dynamics and Kuroshio intrusions.Our observations revealed a significant reorganization in phytoplankton community structure,with the harmful algal bloom(HAB)—forming dinoflagellate Scrippsiella acuminata now dominating euphotic zone assemblages,followed by Nitzschia spp.The pronounced shift toward HAB species dominance elevates ecological risks associated with dinoflagellate blooms,while the concurrent decline in diatom abundance may indicate reduced marine primary productivity.Phytoplankton communities displayed clear spatial segregation,characterized by cyanobacterial dominance in Kuroshio intrusion zones,preferential distribution of dinoflagellates in warm eddy regions,and diatom prevalence in cold eddy systems and deep-current environments.Phytoplankton community composition showed distinct spatial patterns,driven primarily by temperature and nutrient gradients.Deep-sea phytoplankton communities,characterized by elevated diatom-to-dinoflagellate ratios and dominance of fast-sinking species,play a significant role in organic carbon export and biogeochemical cycling processes.展开更多
Tuojiang River Basin is a first-class tributary of the upper reaches of the Yangtze River—which is the longest river in China.As phytoplankton are sensitive indicators of trophic changes inwater bodies,characterizing...Tuojiang River Basin is a first-class tributary of the upper reaches of the Yangtze River—which is the longest river in China.As phytoplankton are sensitive indicators of trophic changes inwater bodies,characterizing phytoplankton communities and their growth influencing factors in polluted urban rivers can provide new ideas for pollution control.Here,we used direct microscopic count and environmental DNA(eDNA)metabarcoding methods to investigate phytoplankton community structure in Tuojiang River Basin(Chengdu,Sichuan Province,China).The association between phytoplankton community structure and water environmental factors was evaluated by Mantel analysis.Additional environmental monitoring data were used to pinpoint major factors that influenced phytoplankton growth based on structural equation modeling.At the phylum level,the dominant phytoplankton taxa identified by the conventional microscopic method mainly belonged to Bacillariophyta,Chlorophyta,and Cyanophyta,in contrast with Chlorophyta,Dinophyceae,and Bacillariophyta identified by eDNA metabarcoding.Inα-diversity analysis,eDNA metabarcoding detected greater species diversity and achieved higher precision than the microscopic method.Phytoplankton growth was largely limited by phosphorus based on the nitrogen-to-phosphorus ratios>16:1 in all water samples.Redundancy analysis and structural equation modeling also confirmed that the nitrogen-to-phosphorus ratio was the principal factor influencing phytoplankton growth.The results could be useful for implementing comprehensive management of the river basin environment.It is recommended to control the discharge of point-and surface-source pollutants and the concentration of dissolved oxygen in areas with excessive nutrients(e.g.,Jianyang-Ziyang).Algae monitoring techniques and removal strategies should be improved in 201 Hospital,Hongrihe Bridge and Colmar Town areas.展开更多
Diel investigations of water environments are one means to holistically understand the dynamics and functional roles of phytoplankton,bacteria and viruses in these ecosystems.They have the potential to substantially i...Diel investigations of water environments are one means to holistically understand the dynamics and functional roles of phytoplankton,bacteria and viruses in these ecosystems.They have the potential to substantially impact carbon(C),nitrogen(N)and phosphorus(P)biogeochemistry through their respective roles.This study characterizes the phytoplankton,bacteria and virus communities and the elemental composition of various C,N and P nutrients flow over three diel cycles in tropical urban lake.Our results show that ratios of C:N:P fluctuated strongly from the lack of dissolved organic phosphorus(DOP)and PO_(4).Specifically,green algae peaked during day time and exudate dissolved organic matter(DOM)that strongly modulate dissolved organic carbon(DOC):DOP ratio to diel DOP limitation.Multiple linear regression and Stella modelling emphasize the roles of viruses together with Synechococcus as important nutrient recyclers of NH_(4)and PO_(4)in nutrients-limited waters.Respective normalised surface PO_(4)and combined surface and bottom NH_(4)concentration selected both viruses and Synechococcus as important drivers.Process model of N and P biogeochemical cycles can achieve 69%and 57%similar to observed concentration of NH_(4)and PO_(4),respectively.A short latent period of 9 hr was calculated,in addition to the calibrated high infectivity of viruses to Synechococcus.Taken together,the rapid turn-over between Synechococcus and viruses has biogeochemical significance,where the rapid recycling of essential nutrients allows for shortcuts in the N and P cycle,supporting a wide range of microbes.展开更多
To better understand the spatial variations in phytoplankton abundance and community structure and their relationship with environmental parameters in Jiaozhou Bay,Yellow Sea,in Shandong,East China,observations were c...To better understand the spatial variations in phytoplankton abundance and community structure and their relationship with environmental parameters in Jiaozhou Bay,Yellow Sea,in Shandong,East China,observations were conducted to estimate abundance of net-phytoplankton and key groups along with environmental parameters in three typical sites in seasonal survey from 2004 to 2016 in the bay.The spatial patterns of phytoplankton abundance differed obviously between the inner and the outer bay.The abundance of total phytoplankton and diatoms increased obviously in the northern part of the bay,while decreased in the southern part and outer bay.An increase in dinoflagellate abundance was obvious in the outer bay.Variations in the dynamics of phytoplankton abundance could be largely explained by the succession of chain-forming diatoms and dinoflagellates.The key chain forming diatom groups Chaetoceros and Thalassiosira increased markedly,especially in winter in the northern part of the bay,while in the southern part and the outer bay,Chaetoceros declined.Besides,the key dinoflagellate groups Ceratium and Noctiluca increased noticeably,resulting in a significant increase in the dinoflagellate/diatom ratio in the outer bay.These variations has a significant correlation with environmental variables of surface seawater temperature,phosphorus,nitrogen,salinity,and N/Si ratio(P<0.05).For the key groups,temperature was the primary driver of dinoflagellate abundance,while the N/P ratio was critical for chain-forming diatoms.The abundance of phytoplankton showed a clear spatial pattern and associated obviously with environmental factors in the marine ecosystems,offering insights into coastal ecosystem management and conservation strategies.展开更多
Pigments are widely used as indices for estimation of phytoplankton biomass and composition,and many protocols have been developed to analyze pigments in phytoplankton.Different protocols were compared using four solv...Pigments are widely used as indices for estimation of phytoplankton biomass and composition,and many protocols have been developed to analyze pigments in phytoplankton.Different protocols were compared using four solvents(methanol,95%methanol,dimethylformamide,and 90%acetone)and two instruments(fluorometer and high-performance liquid chromatography(HPLC)coupled with diode array detector).Analysis of chlorophyll a(Chl a)with fluorometer could lead to over-or underestimation due to the interference from its derivatives in all probability.Among the four extractants,90%acetone had a high recovery for chlorophylls.In contrast,95%methanol was a poor extractant for chlorophylls due to the degradation of Chl a,especially in diatoms.The 95%methanol,however,had high extraction efficiencies for most diagnostic xanthophylls.Therefore,the selection of pigment analytical protocols should follow the specific purpose of phytoplankton study.In addition to fluorometry,an HPLC method with 90%acetone as extractant shall be a good choice for the analysis of Chl a to estimate phytoplankton biomass,especially for diatom-dominated samples,while an HPLC method with 95%methanol as extractant be more suitable to characterize different taxa in phytoplankton communities.展开更多
Polycyclic aromatic hydrocarbons(PAHs)are of great concern because they threaten pri-mary productivity,but their specific effects on ecosystem functioning are scarce,hindering a comprehensive understanding of their ec...Polycyclic aromatic hydrocarbons(PAHs)are of great concern because they threaten pri-mary productivity,but their specific effects on ecosystem functioning are scarce,hindering a comprehensive understanding of their ecological risks,especially in eutrophicwaters.The present study was conducted by adding PAHs to four marine phytoplankton species and showed that naphthalene(Nap)and phenanthrene(Phe)induced both stimulatory and in-hibitory effects(>50%)on urea and NO_(3)−uptake by phytoplankton species.In addition,the apparent stimulative effects(>50%)for NH_(4)^(+)were also observed.Overall,38.9%of the sam-ples exhibited stimulation effects after 24 h exposure,which increased to 61.1%after 96 h exposure.This suggested the existence of a lag period,during which a tolerant cell popula-tion could adapt to PAHs.Significant positive correlations(P<0.01)between low and high concentrations of PAH individuals demonstrated that the mode of action for both pollutants on nitrogen uptake by phytoplankton was the same.Species-specific responses were also observed,with 19.0%of Thalassiosira sp.and 24.0%of Tetraselmis sp.exhibited inhibition effects greater than 50%,while 40.9%of Karlodinium veneficum and 27.3%of Rhodomonas salina demonstrated stimulation effects exceeding 50%,providing a unique perspective for exploring the harmful algal bloom of the mixotrophic K.veneficum,in addition to the original consideration of nutrients.The internal mechanisms may lie in differences in energy consumption between N-forms,exposure time and chemical concentrations,aswell as mor-phological characteristics and biochemical structures of the species,which require further investigation.展开更多
The functional diversity index of a phytoplankton body has gradually become a new mean of measuring and research.To explore the response of phytoplankton taxonomy and the functional diversity index to interannual envi...The functional diversity index of a phytoplankton body has gradually become a new mean of measuring and research.To explore the response of phytoplankton taxonomy and the functional diversity index to interannual environmental changes,a survey on the structure of the phytoplankton community and water physicochemical characteristics of the water was carried out at 28 sampling points in the Harbin section of the Songhua River for three consecutive years in every May from 2021 to 2023.The taxonomy diversity index and the functional diversity index were calculated.Firstly,The relationship between the structure of the characteristics of the community and environmental factors was explored;secondly,we reveal the responses of taxonomic and functional diversity indices to different habitats between years;finally,we explore the main environmental factors that control the taxonomic and functional diversity indices of phytoplankton.Results show that,initially,environmental factors in water changes caused by different water levels between years affected the composition of phytoplankton communities.Subsequently,by comparing the taxonomic diversity index and the functional diversity index on a time scale,we found that the taxonomic diversity index was more responsive to environmental changes.Ultimately,the main environmental factors on the phytoplankton taxonomic diversity index were dissolved oxygen,Taxonomic diversity index,and specific conductivity,and the main environmental factors that affected the functional diversity index were dissolved oxygen,turbidity,and water temperature.This study reveals the important role of the taxonomic diversity index in river water quality evaluation,obtained new information on the relative precision of the taxonomic diversity index and the functional diversity index in the evaluation of ecological health of the water,and provided a reliable tool for monitoring river water quality based on aquatic organisms.展开更多
Phytoplankton play a pivotal role in the Southern Ocean ecosystem.This study examines the phytoplankton community structure and the environmental factors driving it in the Cosmonaut Sea,based on samples collected usin...Phytoplankton play a pivotal role in the Southern Ocean ecosystem.This study examines the phytoplankton community structure and the environmental factors driving it in the Cosmonaut Sea,based on samples collected using a net during the summer of 2020/2021.We identified 99 phytoplankton species,predominantly comprising diatoms and dinoflagellates.Among these,diatoms-notably Pseudo-nitzschia,Chaetoceros,and Fragilariopsis,dominated the community in terms of species richness,abundance,and biomass.Endemic species of the Southern Ocean,such as Corethron pennatum,Proboscia alata,and Cylindrotheca closterium,also made significant contributions.Phytoplankton abundance and biomass showed similar spatial distribution patterns,with hotspots in the northern section of the survey area that gradually diminished towards the coastal regions.The oceanic area exhibited low phytoplankton diversity but pronounced regional variations in community distribution,with the northern region emerging as a key zone for abundance,biomass,and diversity.Nutrient distribution was identified as the primary environmental driver shaping the phytoplankton community,with silicate levels having a significant negative impact on overall phytoplankton abundance and the dominant species.展开更多
Seasonal cycles of phytoplankton blooms are crucial to marine ecosystems and highly sensitive to environmental fluctuations.Rapid climate change has a profound impact on regional environmental conditions,thereby affec...Seasonal cycles of phytoplankton blooms are crucial to marine ecosystems and highly sensitive to environmental fluctuations.Rapid climate change has a profound impact on regional environmental conditions,thereby affecting seasonal blooms at both regional and global scales.The western Antarctic Peninsula(WAP)is one of the most productive regions in the Southern Ocean and has experienced accelerated climate change in recent decades.However,the impact of climate change on bloom dynamics in this region remains uncertain due to regional variability and the complex interplay of environmental factors.Using 26 a(1998−2023)of satellite data,this study examines patterns and trends in bloom seasonal metrics on the southern WAP,and further explores the impact of large-scale climate drivers.A key finding was a clear shift in bloom timing,with earlier and longer blooms observed during 2012−2023.These shifts were associated with reduced spring sea ice extent(SIE),which correlated with warming spring sea surface air temperatures(SAT).Atmospheric teleconnections,particularly the El Niño-Southern Oscillation(ENSO)and Southern Annular Mode(SAM)in spring,were linked to changes in SAT and sea ice dynamics.This study highlights the role of climate drivers in altering bloom dynamics,potentially affecting local marine food webs,and underscores the need for further research to understand Antarctic ecosystem evolution under future climate scenarios.展开更多
Phytoplankton play a crucial role in maintaining the health of river ecosystems,and their communities are closely linked to river hydrodynamics.In inland waterways,disturbances generated by ship propellers alter flow ...Phytoplankton play a crucial role in maintaining the health of river ecosystems,and their communities are closely linked to river hydrodynamics.In inland waterways,disturbances generated by ship propellers alter flow dynamics and may affect phytoplankton communities.To clarify it,phytoplankton communities in the Zhenjiang section of the Beijing-Hangzhou Grand Canal(BHGC)in China,the world's longest canal,were studied and compared them with its undisturbed tributaries.The results revealed major alternations in seasonal patterns of phytoplankton communities in the BHGC,shifting the peak of phytoplankton density from spring to autumn and the lowest diversity from summer to autumn.Ship disturbances increased water turbidity and created optimal N/P ratios,which provided Cyanobacteria with a competitive advantage in autumn.The proliferation of Cyanobacteria resulted in a phytoplankton density in the BHGC,exceeding that in the tributaries by more than tenfold,accompanied by a decrease in diversity to its lowest level.Due to habitat alterations,functional groups emerged that are resilient to strong disturbances and high turbidity.The findings add to the understanding of the impact of ship traffic on river ecosystems.展开更多
Understanding the response of the phytoplankton community to climate change is essential for reservoir management.We analyzed a long-term data series(2009–2020)on the phytoplankton community in a large mesotrophic re...Understanding the response of the phytoplankton community to climate change is essential for reservoir management.We analyzed a long-term data series(2009–2020)on the phytoplankton community in a large mesotrophic reservoir in the wet season to investigate the impacts of temperature and precipitation increases caused by climate change on the functioning and trait composition of the phytoplankton community.Over the last twelve years,the 3-month accumulative precipitation increased from 291.03 mm to 590.91 mm,and the surface water temperature increased from 25.06℃to 26.49℃in wet season,respectively.These changes caused a higher water level,stronger thermal stratification and lower nitrogen concentration in Daxi Reservoir.The dynamic equilibrium model indicated that the increased precipitation and water temperature-related environmental changes would result in a more diverse and productive phytoplankton community.The effects of increasing water temperature and precipitation on the niche complementarity and selection effects within the phytoplankton community were analyzed using structural equation model by means of the functional divergence index and functional evenness index,respectively,elucidating the reasons for the increase in cyanobacteria in the absence of a significant increase in nutrient levels.Based on these results,it is advisable that more stringent phosphorus control standards might be conducted to reduce the risks of cyanobacteria proliferation in the context of global warming.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
The property of water mass plays an important role in determining the distribution of phytoplankton in the ocean.In the Yellow Sea,summer stratification constrains water exchange and differentiates the properties of t...The property of water mass plays an important role in determining the distribution of phytoplankton in the ocean.In the Yellow Sea,summer stratification constrains water exchange and differentiates the properties of the Yellow Sea Cold Water Mass(YSCWM)and surface water,which in turn affects the spatiotemporal patterns of phytoplankton communities.Here,based on four summer cruises in the Yellow Sea,we examined the response of phytoplankton pigment assemblages to three water masses,including surface water(water massⅠ,WM-Ⅰ),thermocline water(WM-Ⅱ),and the YSCWM(WM-Ⅲ).Based on the opportunities for group dominance across the four cruises,Cyanophyceae,Haptophyceae,Chlorophyceae,and Cryptophyceae preferred living in WM-Ⅰ,characterized by relatively higher temperature and light intensity but lower nutrients;Bacillariophyceae,Chlorophyceae,Cyanophyceae,and Dinophyceae dominated in WM-Ⅲ,with relatively lower temperature and light intensity but higher nutrients.In comparison,the highest diversity of the dominant pigment groups was observed in WM-Ⅱ with intermediate temperature,light,and nutrient levels.The Dirichlet regression model identified the key environmental factors driving changes in phytoplankton assemblages in WM-Ⅰ,Ⅱ,and Ⅲ as dissolved inorganic phosphate(DIP),DIP and light,and temperature and ammonium,respectively.Under the impact of global environmental change,the fluctuations of key driving forces and their potential ecological implications need further investigation.展开更多
Water level fluctuations(WLFs)constituted a dominant factor controlling the structure and function of freshwater ecosystems but the mechanism of WLFs on phytoplankton community structure was still unknown.We investiga...Water level fluctuations(WLFs)constituted a dominant factor controlling the structure and function of freshwater ecosystems but the mechanism of WLFs on phytoplankton community structure was still unknown.We investigated the characteristics of phytoplankton community structure in Xiangxi Bay from January 2017 to December 2020.Results indicated water level(WL)of the Three Gorges Reservoir was divided into four distinct stages:the decreasing stage(DS),the low water level stage(LS),the storage stage(SS),and the high water level stage(HS).Notably,Cyanophyta predominated during the LS,with Microcystis sp.being the dominant species.Bacillariophyta was predominant in other three WL stages,with Melosira sp.and Cyclotella sp.as the dominant species.The highest biomass appeared in LS,whereas the lowest appeared in HS.Moreover,alpha diversity appeared to be lower in both HS and LS compared to DS and SS.Redundancy analysis showed WL as the key driver of phytoplankton community.Partial least squares path model analyses demonstrated that WL not only altered chemical factors(path coefficient=-0.62,P<0.01),thereby leading to changes in phytoplankton biomass(path coefficient=0.56,P<0.01),but also changed the physical factors(path coefficient=-0.69,P<0.01)and consequently had an impact on phytoplankton biomass(path coefficient=0.33,P<0.01).Furthermore,WL influenced phytoplankton diversity by altering chemical and physical factors.In conclusion,WL was an important factor influencing phytoplankton community,which implied that reservoir operation was the potential strategy to regulate phytoplankton communities.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 major phytoplankton was investigated and analyzed in landscape water of six campuses in Nanjing Xianlin University Town,and water quality was evaluated by single factor assessment method and comprehensive weighted...The major phytoplankton was investigated and analyzed in landscape water of six campuses in Nanjing Xianlin University Town,and water quality was evaluated by single factor assessment method and comprehensive weighted evaluation method.The result showed that the major phytoplankton groups were Cyanophyta,Chlorophyta and Bacillariophyta.Besides,each evaluation indicator showed that waterbodies in four campuses were eutrophicated and result of single factor evaluation showed water quality all belonged to poor category V.The result of comprehensive weighted assessment showed that waters in Nanjing Normal University and Nanjing University of Posts and Telecommunications were seriously polluted,cyanobacterial bloom appearing.Waters in Nanjing University of Chinese Medicine and Nanjing Forest Police College hadn't been eutrophicated.展开更多
The cell density, species composition and distribution of phytoplankton, and their relations to environmental factors in Prydz Bay and its adjacent sea area, Antarctica (69degrees-77degrees E, 62degrees-70degrees S) d...The cell density, species composition and distribution of phytoplankton, and their relations to environmental factors in Prydz Bay and its adjacent sea area, Antarctica (69degrees-77degrees E, 62degrees-70degrees S) during the austral summer of 1998/1999 were investigated. A total of 48 taxa belonging to 21 genera of phytoplankton in the sea area were identified. The average cell density of phytoplankton was 22.46 x 10(3) cells/dm(3), of which diatoms were predominant (84.51%). The highest cell density of phytoplankton occurred in Prydz Bay and the adjacent continental shelf where the average cell density was 46.03 x 10(3) cells/dm(3). The lowest cell density (3.34 x 10(3) cells/dm(3)) occurred in deep sea area. The dominant species of phytoplankton was Fragilariopsis curta. The vertical distribution of phytoplankton density was highest in the upper part of 0-50 in depth, lower in 100 in and lowest in 150 in. The species composition and cell density of phytoplankton were influenced by water circulation. The cell density was positively correlated with water temperature and salinity, and negatively correlated with the concentration of nutrients.展开更多
This paper analyzed how nutrient silicon and water temperature influenced the variation of phytoplankton growth and the change of its assemblage structure, and probed the different characteristics of the variation of ...This paper analyzed how nutrient silicon and water temperature influenced the variation of phytoplankton growth and the change of its assemblage structure, and probed the different characteristics of the variation of phytoplankton growth and the different profiles of the change of its assemblage structure influenced by nutrient silicon and water temperature. Taking Jiaozhou Bay for example, this paper showed the process of both the variation of phytoplankton growth and the change of its assemblage structure, unveiled the mechanism of nutrient silicon and water temperature influencing the variation of phytoplankton growth and the change of its assemblage structure, and determined that nutrient silicon and water temperature were the motive power for the healthy running of the marine ecosystem.展开更多
基金supported by the Science and Technology Project of Hebei Education Department(No.QN2023028)the Natural Science Foundation of Hebei Province(No.C2022201042)+1 种基金the High-level Talent Research Funding Project of Hebei University(Nos.521000981405 and 521000981186)the Collaborative Innovation Center for Baiyangdian Basin Ecological Protection and Beijing-Tianjin-Hebei Sustainable Development.
文摘Climate warming and atmospheric nitrogen(N)deposition have profound influences on the terrestrial biosphere.However,how these two global change drivers affect phytoplankton which are important primary producers in wetlands with large carbon stocks and complex hydrological fluctuations remain largely unclear.As part of a two-year field experiment in a freshwater wetland,this study was conducted to investigate the effects of nighttime warming and N addition on phytoplankton biomass in the North China Plain.The results showed that neither nighttime warming nor N addition influenced the Shannon-Wiener index of phytoplankton community.Nighttime warming did not change phytoplankton biomass,likely due to the different warming impacts on dominant phyla and in different seasons.Decreased phytoplankton biomass in spring because of the increased water pH and submerged plant coverage was compensated by the enhanced biomass in autumn due to the reduced dissolved oxygen and submerged plant coverage,leading to the neutral change of phytoplankton biomass under warming.Nitrogen addition elevated phytoplankton biomass by 11.6%,which could be attributed to the enhanced nutrient availability and reduced submerged plant coverage.Positive relationships of methane(CH4)emission rates at the water-air interface with phytoplankton biomass indicated the potentially crucial role of phytoplankton in mediating wetland CH4 cycling through photosynthesis-driven metabolisms.The findings suggested the seasonal variation of phytoplankton and their potential responses to nighttime warming and N deposition,which may provide a more accurate basis for assessing the global change-carbon feedback in wetland ecosystems.
基金The National Polar Special Program under contract Nos IRASCC 01-01-02 and IRASCC 02-02the National Natural Science Foundation of China under contract Nos 41976228,42276255,41976227,42176227,and 42076243+1 种基金the International Cooperation Key Project of the Ministry of Science and Technology under contract No.2022YFE0136500the Scientific Research Fund of the Second Institute of Oceanography,Ministry of Natural Resources,under contract Nos JG2011,JG2211,JG2013,and JG1805.
文摘Polynyas and their adjacent seasonal ice zones(SIZs)represent the most productive regions in the Southern Ocean,supporting unique food webs that are highly sensitive to climate change.Understanding the dynamics of phytoplankton and the carbon pool in these areas is crucial for assessing the role of the Southern Ocean in global carbon cycling.During the late stage of an algal bloom,seawater samples at 14 stations were collected in the Amundsen Sea Polynya(ASP)and adjacent SIZ.Using nutrients,phytoplankton pigments,organic carbon(OC),remote sensing data,and physicochemical measurements,as well as CHEMTAX model simulations,we investigated the response of the phytoplankton crops,taxonomic composition,and OC pool to environmental factors.Our analyses revealed that hydrodynamic regimes of the polynya,adjacent SIZs and open sea were regulated by the regionally varying intrusion of Circumpolar Deep Water,photosynthetically active radiation and sea ice melt water.The ASP exhibited the highest seasonal nutrient utilization rates[ΔN=(1059±386)mmol/m^(2),ΔP=(50±17)mmol/m^(2) andΔSi=(956±904)mmol/m^(2)],while the open sea had lower rates.The integrated chlorophyll a(Chl a)concentration at depths of 0–200 m ranged from 20.4 mg/m^(2) to 1420.0 mg/m^(2) and peaked in the polynya.In the study area,Haptophytes Phaeocystis antarctica was the dominant functional group(34%±27%),and diatoms acted as a secondary contributor(23%±14%).The major functional group and particulate OC(POC)contributor varied from diatoms(36%±12%)in the open sea to haptophytes(48%±31%)in the polynya waters.Strong light conditions and microelement limitations promoted the dominance of P.antarctica(low Fe forms)dominance in the ASP.The strong correlations between the POC and Chl a depth-integrated concentration suggest that the POC was primarily derived from phytoplankton,while dissolved OC(DOC)was influenced by consumer activity and water mass transport.In addition,the transport of OC in the upper 200 m of the water column within the ASP was quantified,revealing the predominantly westward fluxes for both DOC[9.0 mg/(m^(2)·s)]and POC[7.2 mg/(m^(2)·s)].The latitudinal transport exhibited the northward transport of DOC[8.1 mg/(m^(2)·s)]and southward transport of POC[4.3 mg/(m^(2)·s)]movement.These findings have significant implications for enhancing our understanding of how hydrodynamics influence OC cycling in polynya regions.
基金The National Natural Science Foundation of China under contract No.32501444.
文摘This study systematically examined phytoplankton community structure and its spatial distribution across euphotic and deep-water layers in the northeastern South China Sea(ne-SCS),elucidating their responses to physical processes including eddy dynamics and Kuroshio intrusions.Our observations revealed a significant reorganization in phytoplankton community structure,with the harmful algal bloom(HAB)—forming dinoflagellate Scrippsiella acuminata now dominating euphotic zone assemblages,followed by Nitzschia spp.The pronounced shift toward HAB species dominance elevates ecological risks associated with dinoflagellate blooms,while the concurrent decline in diatom abundance may indicate reduced marine primary productivity.Phytoplankton communities displayed clear spatial segregation,characterized by cyanobacterial dominance in Kuroshio intrusion zones,preferential distribution of dinoflagellates in warm eddy regions,and diatom prevalence in cold eddy systems and deep-current environments.Phytoplankton community composition showed distinct spatial patterns,driven primarily by temperature and nutrient gradients.Deep-sea phytoplankton communities,characterized by elevated diatom-to-dinoflagellate ratios and dominance of fast-sinking species,play a significant role in organic carbon export and biogeochemical cycling processes.
基金supported by the National Natural Science Foundation of China (No.72091511)the Science Fund for Distinguished Young Scholars of Hebei Province (No.E2022402064).
文摘Tuojiang River Basin is a first-class tributary of the upper reaches of the Yangtze River—which is the longest river in China.As phytoplankton are sensitive indicators of trophic changes inwater bodies,characterizing phytoplankton communities and their growth influencing factors in polluted urban rivers can provide new ideas for pollution control.Here,we used direct microscopic count and environmental DNA(eDNA)metabarcoding methods to investigate phytoplankton community structure in Tuojiang River Basin(Chengdu,Sichuan Province,China).The association between phytoplankton community structure and water environmental factors was evaluated by Mantel analysis.Additional environmental monitoring data were used to pinpoint major factors that influenced phytoplankton growth based on structural equation modeling.At the phylum level,the dominant phytoplankton taxa identified by the conventional microscopic method mainly belonged to Bacillariophyta,Chlorophyta,and Cyanophyta,in contrast with Chlorophyta,Dinophyceae,and Bacillariophyta identified by eDNA metabarcoding.Inα-diversity analysis,eDNA metabarcoding detected greater species diversity and achieved higher precision than the microscopic method.Phytoplankton growth was largely limited by phosphorus based on the nitrogen-to-phosphorus ratios>16:1 in all water samples.Redundancy analysis and structural equation modeling also confirmed that the nitrogen-to-phosphorus ratio was the principal factor influencing phytoplankton growth.The results could be useful for implementing comprehensive management of the river basin environment.It is recommended to control the discharge of point-and surface-source pollutants and the concentration of dissolved oxygen in areas with excessive nutrients(e.g.,Jianyang-Ziyang).Algae monitoring techniques and removal strategies should be improved in 201 Hospital,Hongrihe Bridge and Colmar Town areas.
文摘Diel investigations of water environments are one means to holistically understand the dynamics and functional roles of phytoplankton,bacteria and viruses in these ecosystems.They have the potential to substantially impact carbon(C),nitrogen(N)and phosphorus(P)biogeochemistry through their respective roles.This study characterizes the phytoplankton,bacteria and virus communities and the elemental composition of various C,N and P nutrients flow over three diel cycles in tropical urban lake.Our results show that ratios of C:N:P fluctuated strongly from the lack of dissolved organic phosphorus(DOP)and PO_(4).Specifically,green algae peaked during day time and exudate dissolved organic matter(DOM)that strongly modulate dissolved organic carbon(DOC):DOP ratio to diel DOP limitation.Multiple linear regression and Stella modelling emphasize the roles of viruses together with Synechococcus as important nutrient recyclers of NH_(4)and PO_(4)in nutrients-limited waters.Respective normalised surface PO_(4)and combined surface and bottom NH_(4)concentration selected both viruses and Synechococcus as important drivers.Process model of N and P biogeochemical cycles can achieve 69%and 57%similar to observed concentration of NH_(4)and PO_(4),respectively.A short latent period of 9 hr was calculated,in addition to the calibrated high infectivity of viruses to Synechococcus.Taken together,the rapid turn-over between Synechococcus and viruses has biogeochemical significance,where the rapid recycling of essential nutrients allows for shortcuts in the N and P cycle,supporting a wide range of microbes.
基金Supported by the Laoshan Laboratory(No.LSKJ202204005)the International Partnership Program of Chinese Academy of Sciences(No.121311KYSB20190029)+1 种基金the National Natural Science Foundation of China(Nos.U2006206,32371619)the International Partnership Program of Chinese Academy of Sciences(No.133137KYSB20200002)。
文摘To better understand the spatial variations in phytoplankton abundance and community structure and their relationship with environmental parameters in Jiaozhou Bay,Yellow Sea,in Shandong,East China,observations were conducted to estimate abundance of net-phytoplankton and key groups along with environmental parameters in three typical sites in seasonal survey from 2004 to 2016 in the bay.The spatial patterns of phytoplankton abundance differed obviously between the inner and the outer bay.The abundance of total phytoplankton and diatoms increased obviously in the northern part of the bay,while decreased in the southern part and outer bay.An increase in dinoflagellate abundance was obvious in the outer bay.Variations in the dynamics of phytoplankton abundance could be largely explained by the succession of chain-forming diatoms and dinoflagellates.The key chain forming diatom groups Chaetoceros and Thalassiosira increased markedly,especially in winter in the northern part of the bay,while in the southern part and the outer bay,Chaetoceros declined.Besides,the key dinoflagellate groups Ceratium and Noctiluca increased noticeably,resulting in a significant increase in the dinoflagellate/diatom ratio in the outer bay.These variations has a significant correlation with environmental variables of surface seawater temperature,phosphorus,nitrogen,salinity,and N/Si ratio(P<0.05).For the key groups,temperature was the primary driver of dinoflagellate abundance,while the N/P ratio was critical for chain-forming diatoms.The abundance of phytoplankton showed a clear spatial pattern and associated obviously with environmental factors in the marine ecosystems,offering insights into coastal ecosystem management and conservation strategies.
基金Supported by the Joint Project of Guangxi Provincial and China National Natural Science Foundations(Nos.U 20 A 20104,42306152)the Taishan Scholars Program to Prof.Rencheng YU。
文摘Pigments are widely used as indices for estimation of phytoplankton biomass and composition,and many protocols have been developed to analyze pigments in phytoplankton.Different protocols were compared using four solvents(methanol,95%methanol,dimethylformamide,and 90%acetone)and two instruments(fluorometer and high-performance liquid chromatography(HPLC)coupled with diode array detector).Analysis of chlorophyll a(Chl a)with fluorometer could lead to over-or underestimation due to the interference from its derivatives in all probability.Among the four extractants,90%acetone had a high recovery for chlorophylls.In contrast,95%methanol was a poor extractant for chlorophylls due to the degradation of Chl a,especially in diatoms.The 95%methanol,however,had high extraction efficiencies for most diagnostic xanthophylls.Therefore,the selection of pigment analytical protocols should follow the specific purpose of phytoplankton study.In addition to fluorometry,an HPLC method with 90%acetone as extractant shall be a good choice for the analysis of Chl a to estimate phytoplankton biomass,especially for diatom-dominated samples,while an HPLC method with 95%methanol as extractant be more suitable to characterize different taxa in phytoplankton communities.
基金supported by the National Natural Science Foundation of China(No.42277404)the State Environmental Protection Key Laboratory of Aquatic Ecosystem Health in the Middle and Lower Reaches of Yangtze River(No.AEHKF2023004)+2 种基金the National Key Research and Development Programof China(No.2022YFC3202703)the International Collaboration Program of Chinese Academy of Sciences(Nos.SAJC202403,067GJHZ2023034MI)the Autonomous Deployment Project of Key Laboratory of Lake andWatershed Science for Water Security(No.NKL2023-KP01).
文摘Polycyclic aromatic hydrocarbons(PAHs)are of great concern because they threaten pri-mary productivity,but their specific effects on ecosystem functioning are scarce,hindering a comprehensive understanding of their ecological risks,especially in eutrophicwaters.The present study was conducted by adding PAHs to four marine phytoplankton species and showed that naphthalene(Nap)and phenanthrene(Phe)induced both stimulatory and in-hibitory effects(>50%)on urea and NO_(3)−uptake by phytoplankton species.In addition,the apparent stimulative effects(>50%)for NH_(4)^(+)were also observed.Overall,38.9%of the sam-ples exhibited stimulation effects after 24 h exposure,which increased to 61.1%after 96 h exposure.This suggested the existence of a lag period,during which a tolerant cell popula-tion could adapt to PAHs.Significant positive correlations(P<0.01)between low and high concentrations of PAH individuals demonstrated that the mode of action for both pollutants on nitrogen uptake by phytoplankton was the same.Species-specific responses were also observed,with 19.0%of Thalassiosira sp.and 24.0%of Tetraselmis sp.exhibited inhibition effects greater than 50%,while 40.9%of Karlodinium veneficum and 27.3%of Rhodomonas salina demonstrated stimulation effects exceeding 50%,providing a unique perspective for exploring the harmful algal bloom of the mixotrophic K.veneficum,in addition to the original consideration of nutrients.The internal mechanisms may lie in differences in energy consumption between N-forms,exposure time and chemical concentrations,aswell as mor-phological characteristics and biochemical structures of the species,which require further investigation.
基金Supported by the National Natural Science Foundation of China(No.32370215)。
文摘The functional diversity index of a phytoplankton body has gradually become a new mean of measuring and research.To explore the response of phytoplankton taxonomy and the functional diversity index to interannual environmental changes,a survey on the structure of the phytoplankton community and water physicochemical characteristics of the water was carried out at 28 sampling points in the Harbin section of the Songhua River for three consecutive years in every May from 2021 to 2023.The taxonomy diversity index and the functional diversity index were calculated.Firstly,The relationship between the structure of the characteristics of the community and environmental factors was explored;secondly,we reveal the responses of taxonomic and functional diversity indices to different habitats between years;finally,we explore the main environmental factors that control the taxonomic and functional diversity indices of phytoplankton.Results show that,initially,environmental factors in water changes caused by different water levels between years affected the composition of phytoplankton communities.Subsequently,by comparing the taxonomic diversity index and the functional diversity index on a time scale,we found that the taxonomic diversity index was more responsive to environmental changes.Ultimately,the main environmental factors on the phytoplankton taxonomic diversity index were dissolved oxygen,Taxonomic diversity index,and specific conductivity,and the main environmental factors that affected the functional diversity index were dissolved oxygen,turbidity,and water temperature.This study reveals the important role of the taxonomic diversity index in river water quality evaluation,obtained new information on the relative precision of the taxonomic diversity index and the functional diversity index in the evaluation of ecological health of the water,and provided a reliable tool for monitoring river water quality based on aquatic organisms.
基金funded by National Science Foundation of China(Grant no.42276238)Impact and Response of Antarctic Seas to Climate Change(Grant nos.IRASCC 01-02-01D,01-01-02A)Taishan Scholars Program.
文摘Phytoplankton play a pivotal role in the Southern Ocean ecosystem.This study examines the phytoplankton community structure and the environmental factors driving it in the Cosmonaut Sea,based on samples collected using a net during the summer of 2020/2021.We identified 99 phytoplankton species,predominantly comprising diatoms and dinoflagellates.Among these,diatoms-notably Pseudo-nitzschia,Chaetoceros,and Fragilariopsis,dominated the community in terms of species richness,abundance,and biomass.Endemic species of the Southern Ocean,such as Corethron pennatum,Proboscia alata,and Cylindrotheca closterium,also made significant contributions.Phytoplankton abundance and biomass showed similar spatial distribution patterns,with hotspots in the northern section of the survey area that gradually diminished towards the coastal regions.The oceanic area exhibited low phytoplankton diversity but pronounced regional variations in community distribution,with the northern region emerging as a key zone for abundance,biomass,and diversity.Nutrient distribution was identified as the primary environmental driver shaping the phytoplankton community,with silicate levels having a significant negative impact on overall phytoplankton abundance and the dominant species.
基金The National Natural Science Foundation of China under contract Nos 42325602 and 41976164the National Key Research and Development Program of China under contract No.2022YFC2807601.
文摘Seasonal cycles of phytoplankton blooms are crucial to marine ecosystems and highly sensitive to environmental fluctuations.Rapid climate change has a profound impact on regional environmental conditions,thereby affecting seasonal blooms at both regional and global scales.The western Antarctic Peninsula(WAP)is one of the most productive regions in the Southern Ocean and has experienced accelerated climate change in recent decades.However,the impact of climate change on bloom dynamics in this region remains uncertain due to regional variability and the complex interplay of environmental factors.Using 26 a(1998−2023)of satellite data,this study examines patterns and trends in bloom seasonal metrics on the southern WAP,and further explores the impact of large-scale climate drivers.A key finding was a clear shift in bloom timing,with earlier and longer blooms observed during 2012−2023.These shifts were associated with reduced spring sea ice extent(SIE),which correlated with warming spring sea surface air temperatures(SAT).Atmospheric teleconnections,particularly the El Niño-Southern Oscillation(ENSO)and Southern Annular Mode(SAM)in spring,were linked to changes in SAT and sea ice dynamics.This study highlights the role of climate drivers in altering bloom dynamics,potentially affecting local marine food webs,and underscores the need for further research to understand Antarctic ecosystem evolution under future climate scenarios.
基金Jiangsu Provincial Carbon-peak and Carbonneutralization Technology Innovation Project,Grant/Award Number:BK20220041National Natural Science Foundation of China,Grant/Award Numbers:42477073,42277060。
文摘Phytoplankton play a crucial role in maintaining the health of river ecosystems,and their communities are closely linked to river hydrodynamics.In inland waterways,disturbances generated by ship propellers alter flow dynamics and may affect phytoplankton communities.To clarify it,phytoplankton communities in the Zhenjiang section of the Beijing-Hangzhou Grand Canal(BHGC)in China,the world's longest canal,were studied and compared them with its undisturbed tributaries.The results revealed major alternations in seasonal patterns of phytoplankton communities in the BHGC,shifting the peak of phytoplankton density from spring to autumn and the lowest diversity from summer to autumn.Ship disturbances increased water turbidity and created optimal N/P ratios,which provided Cyanobacteria with a competitive advantage in autumn.The proliferation of Cyanobacteria resulted in a phytoplankton density in the BHGC,exceeding that in the tributaries by more than tenfold,accompanied by a decrease in diversity to its lowest level.Due to habitat alterations,functional groups emerged that are resilient to strong disturbances and high turbidity.The findings add to the understanding of the impact of ship traffic on river ecosystems.
基金Supported by the National Natural Science Foundation of China(Nos.U22A20616,32071573)。
文摘Understanding the response of the phytoplankton community to climate change is essential for reservoir management.We analyzed a long-term data series(2009–2020)on the phytoplankton community in a large mesotrophic reservoir in the wet season to investigate the impacts of temperature and precipitation increases caused by climate change on the functioning and trait composition of the phytoplankton community.Over the last twelve years,the 3-month accumulative precipitation increased from 291.03 mm to 590.91 mm,and the surface water temperature increased from 25.06℃to 26.49℃in wet season,respectively.These changes caused a higher water level,stronger thermal stratification and lower nitrogen concentration in Daxi Reservoir.The dynamic equilibrium model indicated that the increased precipitation and water temperature-related environmental changes would result in a more diverse and productive phytoplankton community.The effects of increasing water temperature and precipitation on the niche complementarity and selection effects within the phytoplankton community were analyzed using structural equation model by means of the functional divergence index and functional evenness index,respectively,elucidating the reasons for the increase in cyanobacteria in the absence of a significant increase in nutrient levels.Based on these results,it is advisable that more stringent phosphorus control standards might be conducted to reduce the risks of cyanobacteria proliferation in the context of global warming.
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(No.42030402)the Program of Shanghai Subject Chief Scientist(No.23XD1401200)collected onboard of R/Vs Dongfanghong 2 and Lanhai 101 implementing the open research cruises(Cruise Nos.NORC 2013-01,NORC 2015-01,NORC 2018-01,NORC 2021-01)supported by NSFC Shiptime Sharing Project(Nos.41249901,41449901,41749901,42049901)。
文摘The property of water mass plays an important role in determining the distribution of phytoplankton in the ocean.In the Yellow Sea,summer stratification constrains water exchange and differentiates the properties of the Yellow Sea Cold Water Mass(YSCWM)and surface water,which in turn affects the spatiotemporal patterns of phytoplankton communities.Here,based on four summer cruises in the Yellow Sea,we examined the response of phytoplankton pigment assemblages to three water masses,including surface water(water massⅠ,WM-Ⅰ),thermocline water(WM-Ⅱ),and the YSCWM(WM-Ⅲ).Based on the opportunities for group dominance across the four cruises,Cyanophyceae,Haptophyceae,Chlorophyceae,and Cryptophyceae preferred living in WM-Ⅰ,characterized by relatively higher temperature and light intensity but lower nutrients;Bacillariophyceae,Chlorophyceae,Cyanophyceae,and Dinophyceae dominated in WM-Ⅲ,with relatively lower temperature and light intensity but higher nutrients.In comparison,the highest diversity of the dominant pigment groups was observed in WM-Ⅱ with intermediate temperature,light,and nutrient levels.The Dirichlet regression model identified the key environmental factors driving changes in phytoplankton assemblages in WM-Ⅰ,Ⅱ,and Ⅲ as dissolved inorganic phosphate(DIP),DIP and light,and temperature and ammonium,respectively.Under the impact of global environmental change,the fluctuations of key driving forces and their potential ecological implications need further investigation.
基金supported by the National Natural Science Foundation of China(No.U2040210).
文摘Water level fluctuations(WLFs)constituted a dominant factor controlling the structure and function of freshwater ecosystems but the mechanism of WLFs on phytoplankton community structure was still unknown.We investigated the characteristics of phytoplankton community structure in Xiangxi Bay from January 2017 to December 2020.Results indicated water level(WL)of the Three Gorges Reservoir was divided into four distinct stages:the decreasing stage(DS),the low water level stage(LS),the storage stage(SS),and the high water level stage(HS).Notably,Cyanophyta predominated during the LS,with Microcystis sp.being the dominant species.Bacillariophyta was predominant in other three WL stages,with Melosira sp.and Cyclotella sp.as the dominant species.The highest biomass appeared in LS,whereas the lowest appeared in HS.Moreover,alpha diversity appeared to be lower in both HS and LS compared to DS and SS.Redundancy analysis showed WL as the key driver of phytoplankton community.Partial least squares path model analyses demonstrated that WL not only altered chemical factors(path coefficient=-0.62,P<0.01),thereby leading to changes in phytoplankton biomass(path coefficient=0.56,P<0.01),but also changed the physical factors(path coefficient=-0.69,P<0.01)and consequently had an impact on phytoplankton biomass(path coefficient=0.33,P<0.01).Furthermore,WL influenced phytoplankton diversity by altering chemical and physical factors.In conclusion,WL was an important factor influencing phytoplankton community,which implied that reservoir operation was the potential strategy to regulate phytoplankton communities.
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Supported by National Foundation for Fostering Talents in Basic Science(J0730650)~~
文摘The major phytoplankton was investigated and analyzed in landscape water of six campuses in Nanjing Xianlin University Town,and water quality was evaluated by single factor assessment method and comprehensive weighted evaluation method.The result showed that the major phytoplankton groups were Cyanophyta,Chlorophyta and Bacillariophyta.Besides,each evaluation indicator showed that waterbodies in four campuses were eutrophicated and result of single factor evaluation showed water quality all belonged to poor category V.The result of comprehensive weighted assessment showed that waters in Nanjing Normal University and Nanjing University of Posts and Telecommunications were seriously polluted,cyanobacterial bloom appearing.Waters in Nanjing University of Chinese Medicine and Nanjing Forest Police College hadn't been eutrophicated.
文摘The cell density, species composition and distribution of phytoplankton, and their relations to environmental factors in Prydz Bay and its adjacent sea area, Antarctica (69degrees-77degrees E, 62degrees-70degrees S) during the austral summer of 1998/1999 were investigated. A total of 48 taxa belonging to 21 genera of phytoplankton in the sea area were identified. The average cell density of phytoplankton was 22.46 x 10(3) cells/dm(3), of which diatoms were predominant (84.51%). The highest cell density of phytoplankton occurred in Prydz Bay and the adjacent continental shelf where the average cell density was 46.03 x 10(3) cells/dm(3). The lowest cell density (3.34 x 10(3) cells/dm(3)) occurred in deep sea area. The dominant species of phytoplankton was Fragilariopsis curta. The vertical distribution of phytoplankton density was highest in the upper part of 0-50 in depth, lower in 100 in and lowest in 150 in. The species composition and cell density of phytoplankton were influenced by water circulation. The cell density was positively correlated with water temperature and salinity, and negatively correlated with the concentration of nutrients.
文摘This paper analyzed how nutrient silicon and water temperature influenced the variation of phytoplankton growth and the change of its assemblage structure, and probed the different characteristics of the variation of phytoplankton growth and the different profiles of the change of its assemblage structure influenced by nutrient silicon and water temperature. Taking Jiaozhou Bay for example, this paper showed the process of both the variation of phytoplankton growth and the change of its assemblage structure, unveiled the mechanism of nutrient silicon and water temperature influencing the variation of phytoplankton growth and the change of its assemblage structure, and determined that nutrient silicon and water temperature were the motive power for the healthy running of the marine ecosystem.
