A brief morphometric study of the recent planktonic foraminifera in the eastern Indian Ocean was provided with the taxonomic key to species, synonyms, SEM microphotographs of shells and chamber arrays. By recent class...A brief morphometric study of the recent planktonic foraminifera in the eastern Indian Ocean was provided with the taxonomic key to species, synonyms, SEM microphotographs of shells and chamber arrays. By recent classification, currently 20 species representing 13 genera and 6 families （Canderinidae, Heterohelicoidae, Hedbergellidae, Higerigerinoidae, Globigerinoidae, and Globorotaloidae） identified from the planktonic material of the eastern Indian Ocean up to a depth of 200 m. Their distribution in water （0-200 m） also reports on the new range of expansion in the eastern Indian Ocean, with Dentigloborotalia anfracta, Hastigerina pelagica, Streptochilus globigerus, Globigerinella calida, Globigerinella adamsi, Orcadia reidelii, Tenuitella parkerae, Tenuitella compressa, reported for the first time in this study area. In general, only around 50 planktonic species are valid worldwide, more specifically the species, e.g., H. pelagica, G. calida, G. adamsi, S. globigerus, O. riedeli, T. parkerae, T. compressa, which occur in the eastern Indian Ocean to fill the the paucity of the recent regional taxonomic literature and the problematic identification from the eastern Indian Ocean. This work aims to bridge this gap and help scientists, managers, educators and students to identify plankton foraminifers by using species notes and images.展开更多
Epipont peritrich ciliates are one of the most sessilie protists that attached to the substrate of zooplankton communities especially copepods and crustaceans. Peritrich ciliates can be solitary or colonial form found...Epipont peritrich ciliates are one of the most sessilie protists that attached to the substrate of zooplankton communities especially copepods and crustaceans. Peritrich ciliates can be solitary or colonial form found from the coastal zones and embayment around the world. Present research report is the first snapshot study of the peritrich ciliates and the horizontal distribution in open waters from surface to 200 m depth in the eastern Indian Ocean. Recently, five peritrich ciliates, e.g., Vorticella oceanica, Zootharnnium alternans, Z. alrasheidi, Z. pelagicum, and Z. marinum were collected from plankton net tow samples during the cruise from April 10 to May 13, 2014. The characteristics of the peritrich ciliate were determined according to the shape of the zooids, the ciliary structure and the stalks. The morphometric shape, sizes and characters also explained by examination under light/scanning electron microscopy. Vorticella oceanica and Z. pelagicum showed their association with host such as diatom （i.e, Chaetoceros coarctatus） and copepod （Oithona brevicornis） including some individuals around the dinoflagellate species （Ceraitum tripose）. The distribution of these sessilid ciliates was dominated by the V. oceanica, Z. pelagicum and Z. rnarinurn at the southeast zone while the large colonies of Z. alrasheidi observed at the Bay of Bengal. This distribution can be influenced by substrate availability like diatom （Ch. coarctatus） and copepods （O. brevicornis）.展开更多
One strain of unicellular greenish algae embedded by mucilage was successfully isolated from equatorial area in the Indian Ocean. Microscopic observation, ultrastructure features and genetic identification confirmed t...One strain of unicellular greenish algae embedded by mucilage was successfully isolated from equatorial area in the Indian Ocean. Microscopic observation, ultrastructure features and genetic identification confirmed that the strain was closely related to Cyanothece sp., which was a cyanobacteria species with great ecological significance. Cells were solitary with oval or bacilliform shapes. Diameters of this strain were relatively small, ranging from 2.5 to 6.5 μm on average. Ultrastructure of cells was simple. Thylakoids were arranged parietal and keritomized content were observed in the thylakoid region. Various electron-transparent granules with low electron-dense region as well as cyanophycin or glycogen granules-like organelle and carbonxysomes were also observed. For pigment composition, the dominant pigments were chlorophyll α, β-Carotene, Zeaxanthin and an unknown pigment, contributing 23.8%, 26.1%, 14.7% and 15.7% to total pigments respectively. The phylogenetic analysis of 16S rRNA gene and n/fH gene confirmed that Strain EIO409 was closely related with Cyanothece sp..展开更多
Living coccolithophores(LCs)are regarded as a group of calcifiers and play important roles in global carbon cycle.This study used microscopic observations of LCs in the western Pacific Ocean to investigate their commu...Living coccolithophores(LCs)are regarded as a group of calcifiers and play important roles in global carbon cycle.This study used microscopic observations of LCs in the western Pacific Ocean to investigate their community structure and biodiversity,especially to test whether local physical traits(mesoscale eddies)could explain their biogeographic distributions during autumn of 2017.The coccolithophore calcite inventory based on carbon-volume transformation was estimated in this study.A total of 28 taxa of coccospheres and 19 types of coccoliths were identified from 161 samples.Gephyrocapsa oceanica was the most predominant species in all the coccolithophore community,followed by Florisphaera profunda,Emiliania huxleyi,Umbilicosphaera sibogae,Gladiolithusflabellatus and Umbellosphaera tenuis.The abundance of coccospheres and coccoliths ranged from 0 to 26.8×10^(3)cells/L and from 0 to 138.5×10^(3)coccoliths/L,averaged at 4.2×10^(3)cells/L and 10.9×10^(3)coccoliths/L,respectively.This study indicated that coccolithophore community in the survey area can be clustered into four groups.Three ecological niches of coccolithophores were characterized by their vertical profiles and multivariate statistical analysis.Coccolithophore abundance and species composition were remarkably different among warm-eddy region,G.oceanica dominated warm-eddy region,while F.profunda dominated warm-eddy and none-eddy region.The average values of estimated particulate inorganic carbon,particulate organic carbon were0.197μg/L and 0.140μg/L,respectively.The current field study widened the dataset of coccolithophores in western Pacific Ocean.展开更多
Ocean acidifi cation(OA)and global warming-induced water column stratification can signifi cantly alter phytoplankton-related biological activity in the marine ecosystem.Yet how these changes may play out in the tropi...Ocean acidifi cation(OA)and global warming-induced water column stratification can signifi cantly alter phytoplankton-related biological activity in the marine ecosystem.Yet how these changes may play out in the tropical Indian Ocean remains unclear.This study investigated the ecological and metabolic responses of the different phytoplankton functional groups to elevated CO_(2) partial pressure and nitrate deficiency in two different environments of the eastern Indian Ocean(EIO).It is revealed that phytoplankton growth and metabolic rates are more sensitive to inorganic nutrients rather than CO_(2).The combined interactive effects of OA and N-limitation on phytoplankton populations are functional groupspecific.In particular,the abundance and calcification rate of calcifying coccolithophores are expected to be enhanced in the future EIO.The underlying mechanisms for this enhancement may be ascribed to coccolithophore’s lower carbon concentrating mechanisms(CCMs)efficiency and OA-induced[HCO^(-)_(3)]increase.In comparison,the abundance of non-calcifying microphytoplankton(e.g.,diatoms and dinoflagellates)and primary productivity would be inhibited under those conditions.Diff erent from previous laboratory experiments,interspecifi c competition for resources would be an important consideration in the natural phytoplankton populations.These combined factors would roughly determine calcifying coccolithophores as“winners”and non-calcifying microphytoplankton as“losers”in the future ocean scenario.Due to the large species-specific differences in phytoplankton sensitivity to OA,comprehensive investigations on oceanic phytoplankton communities are essential to precisely predict phytoplankton ecophysiological response to ocean acidification.展开更多
To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21...To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21°N–23.5°N,111°E–117°E).Samples were collected from 65 stations including one for time-series sampling.A total of 212 phytoplankton taxa were identified from 61 genera belonging to 4 phyla.Among them,122 species identified from 42 genera of Bacillariophyta and 83 species from 15 genera of Pyrrophyta.Chain-forming diatoms dominated the phytoplankton community where Pseudonitzschia delicatissima,Guinardia striata,Thalassionema nitzschioides,and P.pungens comprised about 52%of the total abundance.However,higher cell abundances concentrated on both sides of the estuary,because of low salinity and high nutrients brought by diluted water.In addition,Canonical Correspondence Analysis revealed that salinity and dissolved inorganic nitrogen shaped the species composition in the study area.Furthermore,the Jaccard similarity index showed prevailing high similarity in the distribution of species in low-salinity diluted waters,and the Bray-Curtis similarity depicted distinguished grouping for phytoplankton assemblages along the salinity gradient.However,phytoplankton diel vertical cycles showed maximum abundance occurred at 2:00 am,which was mainly contributed by benthic phytoplankton species Pseudo-nitzschia spp.and T.nitzschioides.展开更多
To understand the influence of Kuroshio intrusion on the phytoplankton community,a field investigation was conducted in spring 2017 in the East China Sea(ECS),and 130 seawater samples were collected and analyzed.Trich...To understand the influence of Kuroshio intrusion on the phytoplankton community,a field investigation was conducted in spring 2017 in the East China Sea(ECS),and 130 seawater samples were collected and analyzed.Trichodesmium comprised the highest cell abundance contributing about 66%of the total phytoplankton followed by diatoms(17%)and dinoflagellates(16%).The dominance of the Kuroshio Waters(KW)and the Taiwan Warm Currents(TWC)were higher than the Coastal Waters(CW).The vertical distribution of physicochemical parameters depicted the intrusion of KW at the bottom layer,but it failed to reach the surface as strong upwelling was not initiated.Therefore,the dissolved inorganic phosphate(DIP)concentrations and P/N ratios were the lowest in the CW and the upper water layers,which limited the diatom growth in this area.Besides,the dinoflagellates cell abundance was also lower except in the surface and CW,though they comprised the maximum richness of species among the phytoplankton community.However,the unique characteristics such as diazotrophy and gas vacuoles of Trichodesmium made the situation advantageous,and they comprised the maximum cell abundance in this area especially in KW and the TWC.Temperature,DIP and P/N ratios appeared to be the major environmental drivers for Trichodesmium proliferation in the ECS during the study period.展开更多
Marine picophytoplankton(Pico)as a major contributor to primary productivity in oligotrophic waters,play a very important role in marine material cycle and energy conversion,and their key role in the carbon cycle and ...Marine picophytoplankton(Pico)as a major contributor to primary productivity in oligotrophic waters,play a very important role in marine material cycle and energy conversion,and their key role in the carbon cycle and global climate change is increasingly emphasized.To study the factors aff ecting the dynamic distribution of Synechococcus,Prochlorococcus,and picoeukaryotes in the East China Sea(ECS),a marginal sea of the Northwest Pacific,we investigated 27 stations in May 2017,and collected 148 samples of Pico and nutrients from the surface to the bottom.By means of flow cytometry,the abundance of Pico was measured,and then we estimated the carbon biomass and analyzed the distribution of Pico.Finally,combined with the ECS unique geographical situation and hydrological regime,we evaluated various factors aff ecting the Pico in the ECS.In Pico community,the picoeukaryotes cell abundance was between 0.49×10^(2)-1.44×10^(4) cells/mL.Prochlorococcus ranged from 1.36×10^(3)-3.47×10^(4) cells/mL and Synechococcus ranged from 0.69×10^(3)-1.15×105 cells/mL.Synechococcus was the most,both in abundance and in carbon biomass.Picoeukaryotes were the least in abundance,but has larger contribution to carbon biomass than Prochlorococcus.Water temperature,salinity,and stability of water column influenced Pico distribution.Picoeukaryotes were abundant in the shelf sea,whereas Synechococcus and Prochlorococcus were detected in the northeast of Taiwan,China.This study provided basic information for the study of Pico communities in the ECS and its adjacent marine ecosystem.展开更多
To further understand the effect of Kuroshio intrusion on phytoplankton community structure in the northeastern South China Sea(NSCS,14°–23°N,114°–124°E),one targeted cruise was carried out from ...To further understand the effect of Kuroshio intrusion on phytoplankton community structure in the northeastern South China Sea(NSCS,14°–23°N,114°–124°E),one targeted cruise was carried out from July to August,2017.A total of 79 genera and 287 species were identified,mainly including Bacillariophyta(129 species),Pyrrophyta(150 species),Cyanophyta(4 species),Chrysophyta(3 species)and Haptophyta(1 species).The average abundance of phytoplankton was 2.14×10~3 cells/L,and Cyanobacterium was dominant species accounting for 86.84%of total phytoplankton abundance.The abundance and distribution of dominant Cyanobacterium were obviously various along the flow of the Kuroshio,indicating the Cyanobacterium was profoundly influenced by the physical process of the Kuroshio.Therefore,Cyanobacterium could be used to indicate the influence of Kuroshio intrusion.In addition,the key controlling factors of the phytoplankton community were nitrogen,silicate,phosphate and temperature,according to Canonical Correspondence Analysis.However,the variability of these chemical parameters in the study water was similarly induced by the physical process of circulations.Based on the cluster analysis,the similarity of phytoplankton community is surprisingly divided by the regional influence of the Kuroshio intrusion,which indicated Kuroshio intrusion regulates phytoplankton community in the NSCS.展开更多
Concentrations of biogenic silica(BSi) in the southern Yellow Sea were determined during four cruises(spring:April–May 2014;autumn: November 2014;summer: August–September 2015;winter: January 2016). Samples of BSi w...Concentrations of biogenic silica(BSi) in the southern Yellow Sea were determined during four cruises(spring:April–May 2014;autumn: November 2014;summer: August–September 2015;winter: January 2016). Samples of BSi were measured using the double extraction method. Seasonal and spatial variations of BSi and the potential correlation between chlorophyll a(Chl a) content and BSi in four seasons were measured in this study. Significant spatial variability was observed in seawater BSi concentrations. The average concentration of BSi was highest in winter and lowest in spring. Furthermore, the relationships between concentrations of BSi and hydrological parameters were also discussed. There was a significant positive correlation between Chl a and BSi. The concentrations of BSi showed significant relationships with temperature and the concentrations of silicates, total inorganic nitrogen and total inorganic phosphorus, indicating that distribution of BSi was affected by temperature and nutrient level.展开更多
Phytoplankton growth rates and mortality rates were experimentally examined at 21 stations during the 2017 spring intermonsoon(April to early May)in the northern and central South China Sea(SCS)using the dilution tech...Phytoplankton growth rates and mortality rates were experimentally examined at 21 stations during the 2017 spring intermonsoon(April to early May)in the northern and central South China Sea(SCS)using the dilution technique,with emphasis on a comparison between the northern and central SCS areas which had different environmental factors.There had been higher temperature but lower nutrients and chlorophyll a concentrations in the central SCS than those in the northern SCS.The mean rates of phytoplankton growth(μ0)and microzooplankton grazing(m)were(0.88±0.33)d–1 and(0.55±0.22)d–1 in the central SCS,and both higher than those in the northern SCS with the values ofμ0((0.81±0.16)d–1)and m((0.30±0.09)d–1),respectively.Phytoplankton growth and microzooplankton grazing rates were significantly coupled in both areas.The microzooplankton grazing impact(m/μ0)on phytoplankton was also higher in the central SCS(0.63±0.12)than that in the northern SCS(0.37±0.06).The microzooplankton abundance was significantly correlated with temperature in the surface.Temperature might more effectively promote the microzooplankton grazing rate than phytoplankton growth rate,which might contribute to higher m and m/μ0 in the central SCS.Compared with temperature,nutrients mainly affected the growth rate of phytoplankton.In the nutrient enrichment treatment,the phytoplankton growth rate(μn)was higher thanμ0 in the central SCS,suggesting phytoplankton growth in the central SCS was nutrient limited.The ratio ofμ0/μn was significantly correlated with nutrients concentrations in the both areas,indicating the limitation of nutrients was related to the concentrations of background nutrients in the study stations.展开更多
The quantification of transparent exopolymer particles(TEP) by colorimetric method is of large error and low repeatability,one major reason of which is related to the absence of clear definition and evaluation for par...The quantification of transparent exopolymer particles(TEP) by colorimetric method is of large error and low repeatability,one major reason of which is related to the absence of clear definition and evaluation for part steps of the original method.It is obscure that the 80% sulfuric acid solution,acted as the extraction solution in the determination of TEP,is prepared based on a volume ratio or mass ratio.Furthermore,the change of solubility of recently available Gum Xanthan(GX) from the market means that the original protocol is no longer applicable,and the grinding of GX stock solution with a tissue grinder is replaced by shaking with a rotating shaker in the study to prevent the excessive dissolution of GX.We found that different preparation techniques could result in the varied concentrations of 80% H_(2)SO_(4).The duration of shaking during the preparation of standard solution significantly affected the slope of the calibration curve,which caused different correction results of TEP.The impacts of different extraction solution concentrations and shaking time of GX solution on the quantification of TEP were investigated based on the field sampling and laboratory analysis.The extraction capacities of H_(2)SO_(4) with different concentrations for Alcian Blue were distinct,but had limited effect on the final measuring result of TEP.The change of the standard curve slope came along with the variation of shaking time,which markedly altered the detection limit and calibration result,and the extended shaking time was in favor of the determination of low-concentration TEP.It was suggested that the extraction solution concentration,shaking time and filtration volume of standard solution are required to be well controlled and selected to obtain more accurate results for TEP with different concentrations.展开更多
Microgels are plankton-derived transparent exopolymer particles(TEP)and have a significant impact on global marine carbon cycle.We investigated the influence of biogeochemical variables on the pattern of TEP abundance...Microgels are plankton-derived transparent exopolymer particles(TEP)and have a significant impact on global marine carbon cycle.We investigated the influence of biogeochemical variables on the pattern of TEP abundance and its associated carbon(TEP C)distribution through a vertical transect of the northern South China Sea(nSCS)during summer,2014.The average TEP concentration was 58.32±30.56μg Xeq./L.Vertically,it was higher in the subsurface water column and lower at 200-m water depths.As chlorophyll a(chl a),TEP,and TEP C were highly concentrated at the bottom of the study transect,mainly on the continental shelf bottom and slope regions.Among biotic factors,cyanobacteria,especially Trichodesmium thiebautii showed significant positive correspondences with TEP through studied water columns in nSCS.In addition,TEP showed a positive correlation with chl-a distribution and clustered closely with diatom as well.It indicates a combined contribution of them on TEP sourcing accordingly.Nutrient concentrations were also high due to estuarine diluted water from Zhujiang(Pearl)River in the season that may intrigue those scenarios.Significant positive correlation(P<0.05)among biotic and abiotic parameters also supported the statement.Furthermore,mentionable contribution of TEP-derived TEP C was found after comparing the particulate organic carbon data,which may signify the importance of TEP in local carbon cycle in the nSCS.展开更多
N2 fixation rates(NFR,in terms of N)in the northern South China Sea(nSCS)and the East China Sea(ECS)were measured using the acetylene reduction assay in summer and winter,2009.NFR of the surface water ranged from 1.14...N2 fixation rates(NFR,in terms of N)in the northern South China Sea(nSCS)and the East China Sea(ECS)were measured using the acetylene reduction assay in summer and winter,2009.NFR of the surface water ranged from 1.14 nmol/(L·d)to 10.40 nmol/(L·d)(average at(4.89±3.46)nmol/(L·d),n=11)in summer and 0.74 nmol/(L·d)to 29.45 nmol/(L·d)(average at(7.81±8.50)nmol/(L·d),n=15)in winter.Significant spatio-temporal heterogeneity emerged in our study:the anticyclonic eddies(AE)(P<0.01)and the Kuroshio Current(KC)(P<0.05)performed significantly higher NFR than that in the cyclonic eddies or no-eddy area(CEONE),indicating NFR was profoundly influenced by the physical process of the Kuroshio and mesoscale eddies.The depth-integrated N2 fixation rates(INF,in terms of N)ranged from 52.4μmol/(m2·d)to 905.2μmol/(m2·d)(average at(428.9±305.5)μmol/(m2·d),n=15)in the winter.The contribution of surface NFR to primary production(PP)ranged from 1.7%to 18.5%in the summer,and the mean contribution of INF to new primary production(NPP)in the nSCS and ECS were estimated to be 11.0%and 36.7%in the winter.The contribution of INF to NPP(3.0%–93.9%)also decreased from oligotrophic sea toward the eutrophic waters affected by runoffs or the CEONE.Furthermore,we observed higher contributions compared to previous studies,revealing the vital roles of nitrogen fixation in sustaining the carbon pump of the nSCS and ECS.展开更多
The influence of typhoon and Kuroshio intrusion process on the natural phytoplankton assemblages in the northeastern South China Sea(neSCS)was examined during a cruise in summer 2017.One hundred ninety-six seawater sa...The influence of typhoon and Kuroshio intrusion process on the natural phytoplankton assemblages in the northeastern South China Sea(neSCS)was examined during a cruise in summer 2017.One hundred ninety-six seawater samples were collected and analyzed in the neSCS.In total,299 species were identified belonging to 82 genera,mostly dominated by Bacillariophyta(159),followed by Dinophyta(132),Cyanophyta(4)and Chrysophyta(4).Among all,Thalassionema nitzschioides,Thalassionema frauenfeldii,Thalassiosira minima,in Bacillariophyta,Prorocentrum lenticulatum,Prorocentrum compressum in Dinophyta,and Trichodesmium thiebautii,in the Cyanophyta were the most dominated species,respectively.Correlation analysis shows compared with other groups Bacillariophyta was mostly influenced by silicate,whereas,Dinophyta and Cyanophyta showed significant correlation with temperature,salinity,phosphate,and nitrate.After the typhoon,the higher abundance of Dinophyta was observed,whereas it was lower in case of Bacillariophyta and Cyanophyta,shows typhoon“Roke“and”Haitang”had a significant influence on the phytoplankton assemblages,which could be manifested by the variations of total phytoplankton abundance in the surface water of neSCS.Overall,our present study provides the latest in-depth information about how the environmental factors influencing the phytoplankton density and diversity in the neSCS during summer.展开更多
Marine bacterial community plays a vital role in the formation of the hypoxia zone in coastal oceans.Yet,their dynamics in the seasonal hypoxia zone of the Bohai Sea(BHS)are barely studied.Here,the 16S r RNA gene-base...Marine bacterial community plays a vital role in the formation of the hypoxia zone in coastal oceans.Yet,their dynamics in the seasonal hypoxia zone of the Bohai Sea(BHS)are barely studied.Here,the 16S r RNA gene-based high-throughput sequencing was used to explore the dynamics of their diversity,structure,and function as well as driving factors during the gradual deoxygenation process in the BHS.Our results evinced that the bacterial community was dominated by Proteobacteria,followed by Bacteroidetes,Firmicutes,Actinobacteria,and Cyanobacteria,etc.The abundant subcommunity dominated in the number of sequences(49%)while the rare subcommunity dominated in the number of species(99.61%).Although abundant subcommunity accounted for most sequences,rare subcommunity possessed higher diversity,richness and their population dramatically changed(higher turnover)during the hypoxia transition.Further,co-occurrence network analysis proved the vital role of rare subcommunity in the process of community assembly.Additionally,beta diversity partition revealed that both subcommunities possessed a higher turnover component than nestedness and/or richness component,implying species replacement could explain a considerable percentage of community variation.This variation might be governed by both environmental selection and stochastic processes,and further,it influenced the nitrogen cycle(PICRUSt-based prediction)of the hypoxia zone.Overall,this study provides insight into the spatial-temporal heterogeneity of bacterial and their vital role in biogeochemical cycles in the hypoxia zone of the BHS.These findings will extend our horizons about the stabilization mechanism,feedback regulation,and interactive model inside the bacterial community under oxygen-depleted ecosystems.展开更多
基金The National Natural Science Foundation of China under contract Nos 41876134,41676112,41276124 and 41406155the University Innovation Team Training Program for Tianjin under contract No.TD12-5003the Changjiang Scholar Program of Chinese Ministry of Education of China to Jun Sun
文摘A brief morphometric study of the recent planktonic foraminifera in the eastern Indian Ocean was provided with the taxonomic key to species, synonyms, SEM microphotographs of shells and chamber arrays. By recent classification, currently 20 species representing 13 genera and 6 families （Canderinidae, Heterohelicoidae, Hedbergellidae, Higerigerinoidae, Globigerinoidae, and Globorotaloidae） identified from the planktonic material of the eastern Indian Ocean up to a depth of 200 m. Their distribution in water （0-200 m） also reports on the new range of expansion in the eastern Indian Ocean, with Dentigloborotalia anfracta, Hastigerina pelagica, Streptochilus globigerus, Globigerinella calida, Globigerinella adamsi, Orcadia reidelii, Tenuitella parkerae, Tenuitella compressa, reported for the first time in this study area. In general, only around 50 planktonic species are valid worldwide, more specifically the species, e.g., H. pelagica, G. calida, G. adamsi, S. globigerus, O. riedeli, T. parkerae, T. compressa, which occur in the eastern Indian Ocean to fill the the paucity of the recent regional taxonomic literature and the problematic identification from the eastern Indian Ocean. This work aims to bridge this gap and help scientists, managers, educators and students to identify plankton foraminifers by using species notes and images.
基金The NSFC Open Cruise for the Eastern Indian Ocean during March–May 2014the National Natural Science Foundation of China under contract Nos 41876134,41676112,41276124 and 41406155+1 种基金the University Innovation Team Training Program for Tianjin under contract No.TD12-5003the Changjiang Scholar Program of Chinese Ministry of Education of China to Jun Sun
文摘Epipont peritrich ciliates are one of the most sessilie protists that attached to the substrate of zooplankton communities especially copepods and crustaceans. Peritrich ciliates can be solitary or colonial form found from the coastal zones and embayment around the world. Present research report is the first snapshot study of the peritrich ciliates and the horizontal distribution in open waters from surface to 200 m depth in the eastern Indian Ocean. Recently, five peritrich ciliates, e.g., Vorticella oceanica, Zootharnnium alternans, Z. alrasheidi, Z. pelagicum, and Z. marinum were collected from plankton net tow samples during the cruise from April 10 to May 13, 2014. The characteristics of the peritrich ciliate were determined according to the shape of the zooids, the ciliary structure and the stalks. The morphometric shape, sizes and characters also explained by examination under light/scanning electron microscopy. Vorticella oceanica and Z. pelagicum showed their association with host such as diatom （i.e, Chaetoceros coarctatus） and copepod （Oithona brevicornis） including some individuals around the dinoflagellate species （Ceraitum tripose）. The distribution of these sessilid ciliates was dominated by the V. oceanica, Z. pelagicum and Z. rnarinurn at the southeast zone while the large colonies of Z. alrasheidi observed at the Bay of Bengal. This distribution can be influenced by substrate availability like diatom （Ch. coarctatus） and copepods （O. brevicornis）.
基金The National Natural Science Foundation of China under contract Nos 41876134,41676112,41276124,41406155 and 41506182the Natural Science Foundation of Tianjin under contract No.17JCZDJC40000+1 种基金the Exploration Program of Ocean with Science and Technology of Tianjin under contract No.KJXH2013-22the Changjiang Scholar Program of Chinese Ministry of Education of China to Jun Sun
文摘One strain of unicellular greenish algae embedded by mucilage was successfully isolated from equatorial area in the Indian Ocean. Microscopic observation, ultrastructure features and genetic identification confirmed that the strain was closely related to Cyanothece sp., which was a cyanobacteria species with great ecological significance. Cells were solitary with oval or bacilliform shapes. Diameters of this strain were relatively small, ranging from 2.5 to 6.5 μm on average. Ultrastructure of cells was simple. Thylakoids were arranged parietal and keritomized content were observed in the thylakoid region. Various electron-transparent granules with low electron-dense region as well as cyanophycin or glycogen granules-like organelle and carbonxysomes were also observed. For pigment composition, the dominant pigments were chlorophyll α, β-Carotene, Zeaxanthin and an unknown pigment, contributing 23.8%, 26.1%, 14.7% and 15.7% to total pigments respectively. The phylogenetic analysis of 16S rRNA gene and n/fH gene confirmed that Strain EIO409 was closely related with Cyanothece sp..
基金The National Natural Science Foundation of China under contract Nos 41876134,41676112,41276124the University Innovation Team Training Program for Tianjin under contract No.TD12-5003+1 种基金the Tianjin 131 Innovation Team Program under contract No.20180314the Changjiang Scholar Program of Chinese Ministry of Education under contract No.T2014253。
文摘Living coccolithophores(LCs)are regarded as a group of calcifiers and play important roles in global carbon cycle.This study used microscopic observations of LCs in the western Pacific Ocean to investigate their community structure and biodiversity,especially to test whether local physical traits(mesoscale eddies)could explain their biogeographic distributions during autumn of 2017.The coccolithophore calcite inventory based on carbon-volume transformation was estimated in this study.A total of 28 taxa of coccospheres and 19 types of coccoliths were identified from 161 samples.Gephyrocapsa oceanica was the most predominant species in all the coccolithophore community,followed by Florisphaera profunda,Emiliania huxleyi,Umbilicosphaera sibogae,Gladiolithusflabellatus and Umbellosphaera tenuis.The abundance of coccospheres and coccoliths ranged from 0 to 26.8×10^(3)cells/L and from 0 to 138.5×10^(3)coccoliths/L,averaged at 4.2×10^(3)cells/L and 10.9×10^(3)coccoliths/L,respectively.This study indicated that coccolithophore community in the survey area can be clustered into four groups.Three ecological niches of coccolithophores were characterized by their vertical profiles and multivariate statistical analysis.Coccolithophore abundance and species composition were remarkably different among warm-eddy region,G.oceanica dominated warm-eddy region,while F.profunda dominated warm-eddy and none-eddy region.The average values of estimated particulate inorganic carbon,particulate organic carbon were0.197μg/L and 0.140μg/L,respectively.The current field study widened the dataset of coccolithophores in western Pacific Ocean.
基金Supported by the National Natural Science Foundation of China(Nos.41876134,41676112,41276124,41706184)the Changjiang Scholar Program of Chinese Ministry of Education of China(No.T2014253)to Jun SUN。
文摘Ocean acidifi cation(OA)and global warming-induced water column stratification can signifi cantly alter phytoplankton-related biological activity in the marine ecosystem.Yet how these changes may play out in the tropical Indian Ocean remains unclear.This study investigated the ecological and metabolic responses of the different phytoplankton functional groups to elevated CO_(2) partial pressure and nitrate deficiency in two different environments of the eastern Indian Ocean(EIO).It is revealed that phytoplankton growth and metabolic rates are more sensitive to inorganic nutrients rather than CO_(2).The combined interactive effects of OA and N-limitation on phytoplankton populations are functional groupspecific.In particular,the abundance and calcification rate of calcifying coccolithophores are expected to be enhanced in the future EIO.The underlying mechanisms for this enhancement may be ascribed to coccolithophore’s lower carbon concentrating mechanisms(CCMs)efficiency and OA-induced[HCO^(-)_(3)]increase.In comparison,the abundance of non-calcifying microphytoplankton(e.g.,diatoms and dinoflagellates)and primary productivity would be inhibited under those conditions.Diff erent from previous laboratory experiments,interspecifi c competition for resources would be an important consideration in the natural phytoplankton populations.These combined factors would roughly determine calcifying coccolithophores as“winners”and non-calcifying microphytoplankton as“losers”in the future ocean scenario.Due to the large species-specific differences in phytoplankton sensitivity to OA,comprehensive investigations on oceanic phytoplankton communities are essential to precisely predict phytoplankton ecophysiological response to ocean acidification.
基金Supported by the National Key Research and Development Program of China(No.2015CB954002)the National Natural Science Foundation of China(Nos.41876134,41676112,41276124)+2 种基金the University Innovation Team Training Program for Tianjin(No.TD12-5003)the Tianjin 131 Innovation Team Program(No.20180314)the Changjiang Scholar Program of Chinese Ministry of Education(No.T2014253)to Jun SUN。
文摘To examine the phytoplankton assemblages and the effect of diluted waters on them,a research cruise was conducted from July 19 to August 7,2015 in the Zhujiang(Pearl)River estuary in the northern South China Sea(21°N–23.5°N,111°E–117°E).Samples were collected from 65 stations including one for time-series sampling.A total of 212 phytoplankton taxa were identified from 61 genera belonging to 4 phyla.Among them,122 species identified from 42 genera of Bacillariophyta and 83 species from 15 genera of Pyrrophyta.Chain-forming diatoms dominated the phytoplankton community where Pseudonitzschia delicatissima,Guinardia striata,Thalassionema nitzschioides,and P.pungens comprised about 52%of the total abundance.However,higher cell abundances concentrated on both sides of the estuary,because of low salinity and high nutrients brought by diluted water.In addition,Canonical Correspondence Analysis revealed that salinity and dissolved inorganic nitrogen shaped the species composition in the study area.Furthermore,the Jaccard similarity index showed prevailing high similarity in the distribution of species in low-salinity diluted waters,and the Bray-Curtis similarity depicted distinguished grouping for phytoplankton assemblages along the salinity gradient.However,phytoplankton diel vertical cycles showed maximum abundance occurred at 2:00 am,which was mainly contributed by benthic phytoplankton species Pseudo-nitzschia spp.and T.nitzschioides.
基金Supported by the National Key Research and Development Project of China(No.2019YFC1407805)the National Natural Science Foundation of China(Nos.41876134,41676112,41276124)+3 种基金the Key Project of Natural Science Foundation for Tianjin(No.17JCZDJC40000)the University Innovation Team Training Program for Tianjin(No.TD12-5003)the Tianjin 131 Innovation Team Program(No.20180314)the Changjiang Scholar Program of Chinese Ministry of Education(No.T2014253)to SUN Jun。
文摘To understand the influence of Kuroshio intrusion on the phytoplankton community,a field investigation was conducted in spring 2017 in the East China Sea(ECS),and 130 seawater samples were collected and analyzed.Trichodesmium comprised the highest cell abundance contributing about 66%of the total phytoplankton followed by diatoms(17%)and dinoflagellates(16%).The dominance of the Kuroshio Waters(KW)and the Taiwan Warm Currents(TWC)were higher than the Coastal Waters(CW).The vertical distribution of physicochemical parameters depicted the intrusion of KW at the bottom layer,but it failed to reach the surface as strong upwelling was not initiated.Therefore,the dissolved inorganic phosphate(DIP)concentrations and P/N ratios were the lowest in the CW and the upper water layers,which limited the diatom growth in this area.Besides,the dinoflagellates cell abundance was also lower except in the surface and CW,though they comprised the maximum richness of species among the phytoplankton community.However,the unique characteristics such as diazotrophy and gas vacuoles of Trichodesmium made the situation advantageous,and they comprised the maximum cell abundance in this area especially in KW and the TWC.Temperature,DIP and P/N ratios appeared to be the major environmental drivers for Trichodesmium proliferation in the ECS during the study period.
基金Supported by the National Key Research and Development Project of China(No.2019YFC1407805)the National Natural Science Foundation of China(Nos.41876134,41676112,41276124)+3 种基金the Key Project of Natural Science Foundation for Tianjin(No.17JCZDJC40000)the University Innovation Team Training Program for Tianjin(No.TD12-5003)the Tianjin 131 Innovation Team Program(No.20180314)the Changjiang Scholar Program of Chinese Ministry of Education(No.T2014253)to SUN Jun。
文摘Marine picophytoplankton(Pico)as a major contributor to primary productivity in oligotrophic waters,play a very important role in marine material cycle and energy conversion,and their key role in the carbon cycle and global climate change is increasingly emphasized.To study the factors aff ecting the dynamic distribution of Synechococcus,Prochlorococcus,and picoeukaryotes in the East China Sea(ECS),a marginal sea of the Northwest Pacific,we investigated 27 stations in May 2017,and collected 148 samples of Pico and nutrients from the surface to the bottom.By means of flow cytometry,the abundance of Pico was measured,and then we estimated the carbon biomass and analyzed the distribution of Pico.Finally,combined with the ECS unique geographical situation and hydrological regime,we evaluated various factors aff ecting the Pico in the ECS.In Pico community,the picoeukaryotes cell abundance was between 0.49×10^(2)-1.44×10^(4) cells/mL.Prochlorococcus ranged from 1.36×10^(3)-3.47×10^(4) cells/mL and Synechococcus ranged from 0.69×10^(3)-1.15×105 cells/mL.Synechococcus was the most,both in abundance and in carbon biomass.Picoeukaryotes were the least in abundance,but has larger contribution to carbon biomass than Prochlorococcus.Water temperature,salinity,and stability of water column influenced Pico distribution.Picoeukaryotes were abundant in the shelf sea,whereas Synechococcus and Prochlorococcus were detected in the northeast of Taiwan,China.This study provided basic information for the study of Pico communities in the ECS and its adjacent marine ecosystem.
基金The National Natural Science Foundation of China under contract Nos 41876134,41676112 and 41276124the Key Project of Natural Science Foundation for Tianjin under contract No.17JCZDJC40000+3 种基金the University Innovation Team Training Program for Tianjin under contract No.TD12-5003the Tianjin 131 Innovation Team Program under contract No.20180314the Changjiang Scholar Program of Chinese Ministry of Education under contract No.T2014253 to Jun SunWe thank the Open Cruise Project in northeastern South China Sea of National Nature Science Foundation of China(NORC2017-07)for sharing their ship time.We also thank our colleagues Jianyu Hu from Xiamen University who provided the temperature and salinity data,and Weifang Chen from Xiamen University for her assistance on cruise coordination.
文摘To further understand the effect of Kuroshio intrusion on phytoplankton community structure in the northeastern South China Sea(NSCS,14°–23°N,114°–124°E),one targeted cruise was carried out from July to August,2017.A total of 79 genera and 287 species were identified,mainly including Bacillariophyta(129 species),Pyrrophyta(150 species),Cyanophyta(4 species),Chrysophyta(3 species)and Haptophyta(1 species).The average abundance of phytoplankton was 2.14×10~3 cells/L,and Cyanobacterium was dominant species accounting for 86.84%of total phytoplankton abundance.The abundance and distribution of dominant Cyanobacterium were obviously various along the flow of the Kuroshio,indicating the Cyanobacterium was profoundly influenced by the physical process of the Kuroshio.Therefore,Cyanobacterium could be used to indicate the influence of Kuroshio intrusion.In addition,the key controlling factors of the phytoplankton community were nitrogen,silicate,phosphate and temperature,according to Canonical Correspondence Analysis.However,the variability of these chemical parameters in the study water was similarly induced by the physical process of circulations.Based on the cluster analysis,the similarity of phytoplankton community is surprisingly divided by the regional influence of the Kuroshio intrusion,which indicated Kuroshio intrusion regulates phytoplankton community in the NSCS.
基金The National Key Research and Development Project of China under contract No.2019YFC1407805the National Natural Science Foundation of China under contract Nos 41876134 and 41676112+3 种基金the Changjiang Scholar Program of Chinese Ministry of Education under contract No.T2014253 to Jun Sunthe NSFC Shiptime Sharing Project under contract Nos NORC2014-01 and NORC2015-01the Tianjin Education Commission Research Plan under contract No.2018KJ100the Foundation of Tianjin Key Laboratory of Marine Resources and Chemistry(Tianjin University of Science&Technology)under contract No.201802
文摘Concentrations of biogenic silica(BSi) in the southern Yellow Sea were determined during four cruises(spring:April–May 2014;autumn: November 2014;summer: August–September 2015;winter: January 2016). Samples of BSi were measured using the double extraction method. Seasonal and spatial variations of BSi and the potential correlation between chlorophyll a(Chl a) content and BSi in four seasons were measured in this study. Significant spatial variability was observed in seawater BSi concentrations. The average concentration of BSi was highest in winter and lowest in spring. Furthermore, the relationships between concentrations of BSi and hydrological parameters were also discussed. There was a significant positive correlation between Chl a and BSi. The concentrations of BSi showed significant relationships with temperature and the concentrations of silicates, total inorganic nitrogen and total inorganic phosphorus, indicating that distribution of BSi was affected by temperature and nutrient level.
基金The National Key Research and Development Program of China under contract No.2019YFC1407805the National Natural Science Foundation of China under contract Nos 41876134 and 41676112+2 种基金the University Innovation Team Training Program for Tianjin under contract No.TD12-5003the Tianjin 131 Innovation Team Program under contract No.20180314the Changjiang Scholar Program of Chinese Ministry of Education to Jun Sun under contract No.T2014253。
文摘Phytoplankton growth rates and mortality rates were experimentally examined at 21 stations during the 2017 spring intermonsoon(April to early May)in the northern and central South China Sea(SCS)using the dilution technique,with emphasis on a comparison between the northern and central SCS areas which had different environmental factors.There had been higher temperature but lower nutrients and chlorophyll a concentrations in the central SCS than those in the northern SCS.The mean rates of phytoplankton growth(μ0)and microzooplankton grazing(m)were(0.88±0.33)d–1 and(0.55±0.22)d–1 in the central SCS,and both higher than those in the northern SCS with the values ofμ0((0.81±0.16)d–1)and m((0.30±0.09)d–1),respectively.Phytoplankton growth and microzooplankton grazing rates were significantly coupled in both areas.The microzooplankton grazing impact(m/μ0)on phytoplankton was also higher in the central SCS(0.63±0.12)than that in the northern SCS(0.37±0.06).The microzooplankton abundance was significantly correlated with temperature in the surface.Temperature might more effectively promote the microzooplankton grazing rate than phytoplankton growth rate,which might contribute to higher m and m/μ0 in the central SCS.Compared with temperature,nutrients mainly affected the growth rate of phytoplankton.In the nutrient enrichment treatment,the phytoplankton growth rate(μn)was higher thanμ0 in the central SCS,suggesting phytoplankton growth in the central SCS was nutrient limited.The ratio ofμ0/μn was significantly correlated with nutrients concentrations in the both areas,indicating the limitation of nutrients was related to the concentrations of background nutrients in the study stations.
基金The National Key Research and Development Project of China under contract No.2019YFC1407805the National Natural Science Foundation of China under contract Nos 41876134, 41676112 and 41276124+1 种基金the Tianjin 131 Innovation Team Program under contract No.20180314the Changjiang Scholar Program of Chinese Ministry of Education under contract No.T2014253。
文摘The quantification of transparent exopolymer particles(TEP) by colorimetric method is of large error and low repeatability,one major reason of which is related to the absence of clear definition and evaluation for part steps of the original method.It is obscure that the 80% sulfuric acid solution,acted as the extraction solution in the determination of TEP,is prepared based on a volume ratio or mass ratio.Furthermore,the change of solubility of recently available Gum Xanthan(GX) from the market means that the original protocol is no longer applicable,and the grinding of GX stock solution with a tissue grinder is replaced by shaking with a rotating shaker in the study to prevent the excessive dissolution of GX.We found that different preparation techniques could result in the varied concentrations of 80% H_(2)SO_(4).The duration of shaking during the preparation of standard solution significantly affected the slope of the calibration curve,which caused different correction results of TEP.The impacts of different extraction solution concentrations and shaking time of GX solution on the quantification of TEP were investigated based on the field sampling and laboratory analysis.The extraction capacities of H_(2)SO_(4) with different concentrations for Alcian Blue were distinct,but had limited effect on the final measuring result of TEP.The change of the standard curve slope came along with the variation of shaking time,which markedly altered the detection limit and calibration result,and the extended shaking time was in favor of the determination of low-concentration TEP.It was suggested that the extraction solution concentration,shaking time and filtration volume of standard solution are required to be well controlled and selected to obtain more accurate results for TEP with different concentrations.
文摘Microgels are plankton-derived transparent exopolymer particles(TEP)and have a significant impact on global marine carbon cycle.We investigated the influence of biogeochemical variables on the pattern of TEP abundance and its associated carbon(TEP C)distribution through a vertical transect of the northern South China Sea(nSCS)during summer,2014.The average TEP concentration was 58.32±30.56μg Xeq./L.Vertically,it was higher in the subsurface water column and lower at 200-m water depths.As chlorophyll a(chl a),TEP,and TEP C were highly concentrated at the bottom of the study transect,mainly on the continental shelf bottom and slope regions.Among biotic factors,cyanobacteria,especially Trichodesmium thiebautii showed significant positive correspondences with TEP through studied water columns in nSCS.In addition,TEP showed a positive correlation with chl-a distribution and clustered closely with diatom as well.It indicates a combined contribution of them on TEP sourcing accordingly.Nutrient concentrations were also high due to estuarine diluted water from Zhujiang(Pearl)River in the season that may intrigue those scenarios.Significant positive correlation(P<0.05)among biotic and abiotic parameters also supported the statement.Furthermore,mentionable contribution of TEP-derived TEP C was found after comparing the particulate organic carbon data,which may signify the importance of TEP in local carbon cycle in the nSCS.
基金The National Natural Science Foundation of China under contract Nos 41876134 and 41406155the University Innovation Team Training Program for Tianjin under contract No.TD12-5003+3 种基金the Tianjin 131 Innovation Team Program under contract No.20180314the Changjiang Scholar Program of Chinese Ministry of Education to Jun Sun under contract No.T2014253the Tianjin Municipal Education Commission Research Program under contract No.2017KJ012the Open Fund of Tianjin Key Laboratory of Marine Resources and Chemistry under contract Nos 201506 and 201801
文摘N2 fixation rates(NFR,in terms of N)in the northern South China Sea(nSCS)and the East China Sea(ECS)were measured using the acetylene reduction assay in summer and winter,2009.NFR of the surface water ranged from 1.14 nmol/(L·d)to 10.40 nmol/(L·d)(average at(4.89±3.46)nmol/(L·d),n=11)in summer and 0.74 nmol/(L·d)to 29.45 nmol/(L·d)(average at(7.81±8.50)nmol/(L·d),n=15)in winter.Significant spatio-temporal heterogeneity emerged in our study:the anticyclonic eddies(AE)(P<0.01)and the Kuroshio Current(KC)(P<0.05)performed significantly higher NFR than that in the cyclonic eddies or no-eddy area(CEONE),indicating NFR was profoundly influenced by the physical process of the Kuroshio and mesoscale eddies.The depth-integrated N2 fixation rates(INF,in terms of N)ranged from 52.4μmol/(m2·d)to 905.2μmol/(m2·d)(average at(428.9±305.5)μmol/(m2·d),n=15)in the winter.The contribution of surface NFR to primary production(PP)ranged from 1.7%to 18.5%in the summer,and the mean contribution of INF to new primary production(NPP)in the nSCS and ECS were estimated to be 11.0%and 36.7%in the winter.The contribution of INF to NPP(3.0%–93.9%)also decreased from oligotrophic sea toward the eutrophic waters affected by runoffs or the CEONE.Furthermore,we observed higher contributions compared to previous studies,revealing the vital roles of nitrogen fixation in sustaining the carbon pump of the nSCS and ECS.
基金This research was financially supported by National Natural Science Foundation of China grants(41876134,41676112 and 41276124)the Changjiang Scholar Program of Chinese Ministry of Education(T2014253)to Jun SunWe would also like to thank the Open Cruise Project in northeastern South China Sea of National Natural Science Foundation of China(NORC2017-07)for sharing their ship time.
文摘The influence of typhoon and Kuroshio intrusion process on the natural phytoplankton assemblages in the northeastern South China Sea(neSCS)was examined during a cruise in summer 2017.One hundred ninety-six seawater samples were collected and analyzed in the neSCS.In total,299 species were identified belonging to 82 genera,mostly dominated by Bacillariophyta(159),followed by Dinophyta(132),Cyanophyta(4)and Chrysophyta(4).Among all,Thalassionema nitzschioides,Thalassionema frauenfeldii,Thalassiosira minima,in Bacillariophyta,Prorocentrum lenticulatum,Prorocentrum compressum in Dinophyta,and Trichodesmium thiebautii,in the Cyanophyta were the most dominated species,respectively.Correlation analysis shows compared with other groups Bacillariophyta was mostly influenced by silicate,whereas,Dinophyta and Cyanophyta showed significant correlation with temperature,salinity,phosphate,and nitrate.After the typhoon,the higher abundance of Dinophyta was observed,whereas it was lower in case of Bacillariophyta and Cyanophyta,shows typhoon“Roke“and”Haitang”had a significant influence on the phytoplankton assemblages,which could be manifested by the variations of total phytoplankton abundance in the surface water of neSCS.Overall,our present study provides the latest in-depth information about how the environmental factors influencing the phytoplankton density and diversity in the neSCS during summer.
基金supported by the National Key Research and Development Project of China(No.2019YFC1407803)the National Natural Science Foundation of China(No.41876134)+1 种基金the Changjiang Scholar Program of Chinese Ministry of Education(No.T2014253)to Jun Sunthe Endowment Fund from Stroud Water Research Center to Jinjun Kan。
文摘Marine bacterial community plays a vital role in the formation of the hypoxia zone in coastal oceans.Yet,their dynamics in the seasonal hypoxia zone of the Bohai Sea(BHS)are barely studied.Here,the 16S r RNA gene-based high-throughput sequencing was used to explore the dynamics of their diversity,structure,and function as well as driving factors during the gradual deoxygenation process in the BHS.Our results evinced that the bacterial community was dominated by Proteobacteria,followed by Bacteroidetes,Firmicutes,Actinobacteria,and Cyanobacteria,etc.The abundant subcommunity dominated in the number of sequences(49%)while the rare subcommunity dominated in the number of species(99.61%).Although abundant subcommunity accounted for most sequences,rare subcommunity possessed higher diversity,richness and their population dramatically changed(higher turnover)during the hypoxia transition.Further,co-occurrence network analysis proved the vital role of rare subcommunity in the process of community assembly.Additionally,beta diversity partition revealed that both subcommunities possessed a higher turnover component than nestedness and/or richness component,implying species replacement could explain a considerable percentage of community variation.This variation might be governed by both environmental selection and stochastic processes,and further,it influenced the nitrogen cycle(PICRUSt-based prediction)of the hypoxia zone.Overall,this study provides insight into the spatial-temporal heterogeneity of bacterial and their vital role in biogeochemical cycles in the hypoxia zone of the BHS.These findings will extend our horizons about the stabilization mechanism,feedback regulation,and interactive model inside the bacterial community under oxygen-depleted ecosystems.
