In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fr...In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific,is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products.Mooring observations were conducted from September 13,2017 to August 15,2018 in the COMRA contact area(10°N,154°W).The results were as follows:(1)At depths below 200 m,the kinetic energy of intra-seasonal variability(20-100 d)accounts for more than 40%of the overall low-frequency variability,while the ratio reaches more than 50%below 2000 m.(2)At depths below 200 m,currents show a synchronous oscillation with a characteristic time scale of 30 d,lasting from October to the following January;the energy of the 30-d oscillation increases with depth until the layer of approximately 4616 m,and the maximum velocity is approximately 10 cm/s.(3)The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.展开更多
The Clarion-Clipperton Zone(CCZ)hosts one of the largest known oceanic nodule fields worldwide and is regulated by the International Seabed Authority.A baseline assessment of diversity and distribution patterns is ess...The Clarion-Clipperton Zone(CCZ)hosts one of the largest known oceanic nodule fields worldwide and is regulated by the International Seabed Authority.A baseline assessment of diversity and distribution patterns is essential for reliable predictions of disturbed ecosystem response scenarios for sustained commercial activities in the future.In the present study,the spatial patterns and diversity of phytoplankton communities were analyzed along with upper ocean biogeochemistry,in the licensed China Ocean Mineral Resources R&D Association(COMRA)contract area and the surrounding western CCZ between August 21 and October 8,2017.Results indicated this was a typical low-nutrient low-chlorophyll a(Chl a)environment,characterized by low levels of phytoplankton abundance and diversity.In total 112 species belonging to 4 phyla were recorded(>10μm),with species counts including 82 diatoms,27 dinoflagellates,1 cyanobacteria and 2 chrysophyte.Dominant taxa in successive order of descending abundance and occurrence included Nizschia marina,Cyclotella stylorum,Dactyliosolen mediterraneus,Rhizosolenia setigera,Pseudo-nitzschia delicatissima,Thalassiothrix frauenfeldii,Synedra sp.,Chaetoceros simplex and Pseudo-nitzschia circumpora.The depth-averaged abundance and Chl a concentrations were(265±233)cells/L and(0.27±0.30)μg/L,respectively.Diatoms accounted for 90.94%of the community with(241±223)cells/L,while dinoflagellates accounted for 5.67%and(15±13)cells/L.The distribution pattern exhibited the same trend as abundance,Chl a and species richness,showing subsurface maximum levels at around 100 m,with stations near 10°N having higher levels than in the north.Cluster analysis was performed in two assemblages,relating to geographic locations to the south and north of 12°N.The subsurface maximum of abundance,Chl a,species richness,dissolved oxygen and nitrite were generally corresponding to the presence of high salinity North Pacific Central Water at depths of 50-120 m.Higher availability of nitrate,phosphate and silicic acid in the subsurface may account for the shift in phytoplankton distribution,as shown by redundancy correspondence and spearman correlation analysis.Diel variation in an anchor station demonstrated prominent species succession without significant differences in oceanographic variables,among which diatoms succession resulted from the light limitation,while dinoflagellate diel variation mainly related to lateral transport of water masses.The observed patchiness in spatial phytoplankton distributional patterns was attributed to upper ocean environmental gradients in the CCZ.The baseline generated in this study could be analyzed using current conservation strategy programs associated with deep-sea mining.展开更多
The flux of settling particles in the ocean has been widely explored since 1980s due to its important role in biogenic elements cycling,especially in the transport of particulate organic carbon(POC)in the deep sea.How...The flux of settling particles in the ocean has been widely explored since 1980s due to its important role in biogenic elements cycling,especially in the transport of particulate organic carbon(POC)in the deep sea.However,research in the seamount area of the oligotrophic subtropical Northwest Pacific Ocean is lacking.In this work,two sediment traps were deployed at the foot and another two at the hillside of Niulang Guyot from August2017 to July 2018.The magnitude and composition of particle fluxes were measured.The main factors influencing the spatial variations of the fluxes were evaluated.Our results indicated a low particulate flux from Niulang Guyot area in the Northwest Pacific Ocean,reflecting low primary productivity of the oligotrophic ocean.The total mass flux(TMF)decreased from 2.57 g/(m^(2)·a)to 0.56 g/(m^(2)·a)with increasing depth from 600 m to 4850 m.A clear seasonal pattern of TMF was observed,with higher flux in summer than that in winter.The peak flux of 26.52 mg/(m^(2)·d)occurred in August at 600 m,while the lowest value of 0.07 mg/(m^(2)·d)was shown in February at 4850 m.The settling particles at the deep layers had similar biochemical composition,with calcium carbonate(CaCO_(3))accounting for up to 90%,followed by organic matter and opal,characteristics of Carbonate Ocean.The POC flux decreased more rapidly in the twilight layer because of faster decomposition,remineralization,and higher temperature.A small fraction of POC was transported into the deep ocean by biological pump.Particle fluxes were mainly controlled by the calcareous ballasts besides the primary productivity of the surface water.The advection may be another important factor affecting the flux in the seamount area.The combination of settled matters rich in foraminiferal tests with topography and currents may be the reason for regulating the local abundance of benthos on seamounts.Our results will fill in the knowledge gap of sedimentation flux,improve the understanding of ecosystem in Niulang Guyot area,and eventually provide data support for the optimization of regional ecological modeling.展开更多
Based upon cruise observations broadly covering the tropical North Pacific during July-November 2017,together with data obtained from the World Ocean Circulation Experiment Hydrographic Program,this study examined the...Based upon cruise observations broadly covering the tropical North Pacific during July-November 2017,together with data obtained from the World Ocean Circulation Experiment Hydrographic Program,this study examined the distribution of dissolved inorganic nitrogen(DIN,nitrate(NO_(3)^(-))+nitrite(NO_(2)^(-))),dissolved inorganic phosphorus(DIP)and related N^(*)(nitrogen-anomaly,N^(*)=N-16P+2.9,where N and P are the concentrations of DIN(>1.0μmol/L)and DIP(>0.1μmol/L)),used as an index of N2fixation,in the upper 1000 m of the water column.Nutrient concentrations displayed distinct spatial variability in the upper ocean but became relatively constant at a depth of 1000 m:they were high at low latitudes and in the eastern region,with an obvious nutricline at~150 m(DIN,~32.0μmol/L;DIP,~2.4μmol/L)and then generally increased with depth;they decreased markedly(DIN,~1.2μmol/L;DIP,~0.1μmol/L;at~150 m)at high latitudes and in the western region,where a nutricline was not apparent.The N^(*)index showed significant meridional and zonal variation,with the most negative values located at low latitudes and in the eastern region(~10°N,~150°-170°E),while becoming positive towards the northwest(the north of~18°N,~160°E westward).A N^(*)concentration larger than 2.0μmol/L which often used as an indicator of N2fixation,was observed between 155°E and 165°E;N^(*)values were 2.0μmol/L to6.0μmol/L at~15°-28°N,i.e.,much higher than those in the southern sector(0-2.0μmol/L at~5°-10°N).Zonally,N^(*)decreased gradually from west(-2.0μmol/L to 4.0μmol/L,~145°-165°E)to east(-2.0μmol/L to-8.0μmol/L,~155°W)along~10°N,which was consistent with the distribution of Trichodesmium abundance and N2fixation rates.Furthermore,since such region was also supplied with aeolian deposition,high N^(*)was probably not only induced by N2fixation but also influenced by iron and/or nitrogen deposition.展开更多
基金The Fund of China Ocean Mineral Resources R&D Association under contract No.DY135-E2-5-01the National Program on Global Change and Air-Sea InteractionⅡunder contract No.GASI-04-WLHY-01。
文摘In this paper,the intra-seasonal variability of the abyssal currents in the China Ocean Mineral Resources Association(COMRA)polymetallic nodule contact area,located in the western part of the Clarion and Clipperton Fraction Zone in the tropical East Pacific,is investigated using direct observations from subsurface mooring instruments as well as sea-surface height data and reanalysis products.Mooring observations were conducted from September 13,2017 to August 15,2018 in the COMRA contact area(10°N,154°W).The results were as follows:(1)At depths below 200 m,the kinetic energy of intra-seasonal variability(20-100 d)accounts for more than 40%of the overall low-frequency variability,while the ratio reaches more than 50%below 2000 m.(2)At depths below 200 m,currents show a synchronous oscillation with a characteristic time scale of 30 d,lasting from October to the following January;the energy of the 30-d oscillation increases with depth until the layer of approximately 4616 m,and the maximum velocity is approximately 10 cm/s.(3)The 30-d oscillation of deep currents is correlated with the tropical instability waves in the upper ocean.
基金The Project of Monitoring and Protection of Ecosystem in the East Pacific Ocean Sponsored by COMRA under contract No.DY135-E2-5-03the National Natural Science Foundation of China under contract Nos 41506217 and 41506136the Project of Ministry of Science and Technology under contract No.GASI-01-02-04。
文摘The Clarion-Clipperton Zone(CCZ)hosts one of the largest known oceanic nodule fields worldwide and is regulated by the International Seabed Authority.A baseline assessment of diversity and distribution patterns is essential for reliable predictions of disturbed ecosystem response scenarios for sustained commercial activities in the future.In the present study,the spatial patterns and diversity of phytoplankton communities were analyzed along with upper ocean biogeochemistry,in the licensed China Ocean Mineral Resources R&D Association(COMRA)contract area and the surrounding western CCZ between August 21 and October 8,2017.Results indicated this was a typical low-nutrient low-chlorophyll a(Chl a)environment,characterized by low levels of phytoplankton abundance and diversity.In total 112 species belonging to 4 phyla were recorded(>10μm),with species counts including 82 diatoms,27 dinoflagellates,1 cyanobacteria and 2 chrysophyte.Dominant taxa in successive order of descending abundance and occurrence included Nizschia marina,Cyclotella stylorum,Dactyliosolen mediterraneus,Rhizosolenia setigera,Pseudo-nitzschia delicatissima,Thalassiothrix frauenfeldii,Synedra sp.,Chaetoceros simplex and Pseudo-nitzschia circumpora.The depth-averaged abundance and Chl a concentrations were(265±233)cells/L and(0.27±0.30)μg/L,respectively.Diatoms accounted for 90.94%of the community with(241±223)cells/L,while dinoflagellates accounted for 5.67%and(15±13)cells/L.The distribution pattern exhibited the same trend as abundance,Chl a and species richness,showing subsurface maximum levels at around 100 m,with stations near 10°N having higher levels than in the north.Cluster analysis was performed in two assemblages,relating to geographic locations to the south and north of 12°N.The subsurface maximum of abundance,Chl a,species richness,dissolved oxygen and nitrite were generally corresponding to the presence of high salinity North Pacific Central Water at depths of 50-120 m.Higher availability of nitrate,phosphate and silicic acid in the subsurface may account for the shift in phytoplankton distribution,as shown by redundancy correspondence and spearman correlation analysis.Diel variation in an anchor station demonstrated prominent species succession without significant differences in oceanographic variables,among which diatoms succession resulted from the light limitation,while dinoflagellate diel variation mainly related to lateral transport of water masses.The observed patchiness in spatial phytoplankton distributional patterns was attributed to upper ocean environmental gradients in the CCZ.The baseline generated in this study could be analyzed using current conservation strategy programs associated with deep-sea mining.
基金The Global Change and Air-sea Interaction II Project under contract Nos GASI-04-HYST-01 and GASI-01-NPACSTsumthe Eastern Pacific Eco-environment Monitoring and Protection Project under contract No.DY135-E2-5-02+1 种基金the Fund of COMRA-45 Cruise under contract No.DY-HC-135-45the Scientific Research Foundation of Third Institute of Oceanography,Ministry of Natural Resources of the People’s Republic of China under contract No.2017014。
文摘The flux of settling particles in the ocean has been widely explored since 1980s due to its important role in biogenic elements cycling,especially in the transport of particulate organic carbon(POC)in the deep sea.However,research in the seamount area of the oligotrophic subtropical Northwest Pacific Ocean is lacking.In this work,two sediment traps were deployed at the foot and another two at the hillside of Niulang Guyot from August2017 to July 2018.The magnitude and composition of particle fluxes were measured.The main factors influencing the spatial variations of the fluxes were evaluated.Our results indicated a low particulate flux from Niulang Guyot area in the Northwest Pacific Ocean,reflecting low primary productivity of the oligotrophic ocean.The total mass flux(TMF)decreased from 2.57 g/(m^(2)·a)to 0.56 g/(m^(2)·a)with increasing depth from 600 m to 4850 m.A clear seasonal pattern of TMF was observed,with higher flux in summer than that in winter.The peak flux of 26.52 mg/(m^(2)·d)occurred in August at 600 m,while the lowest value of 0.07 mg/(m^(2)·d)was shown in February at 4850 m.The settling particles at the deep layers had similar biochemical composition,with calcium carbonate(CaCO_(3))accounting for up to 90%,followed by organic matter and opal,characteristics of Carbonate Ocean.The POC flux decreased more rapidly in the twilight layer because of faster decomposition,remineralization,and higher temperature.A small fraction of POC was transported into the deep ocean by biological pump.Particle fluxes were mainly controlled by the calcareous ballasts besides the primary productivity of the surface water.The advection may be another important factor affecting the flux in the seamount area.The combination of settled matters rich in foraminiferal tests with topography and currents may be the reason for regulating the local abundance of benthos on seamounts.Our results will fill in the knowledge gap of sedimentation flux,improve the understanding of ecosystem in Niulang Guyot area,and eventually provide data support for the optimization of regional ecological modeling.
基金The Eastern Pacific Environment Monitoring and Protection Project under contract No.DY135-E2-5-02the Global Change and Air-Sea Interaction Project+1 种基金the National Natural Science Foundation of China under contract No.42103077the Natural Science Foundation of Fujian Province of China under contract No.2020J05077。
文摘Based upon cruise observations broadly covering the tropical North Pacific during July-November 2017,together with data obtained from the World Ocean Circulation Experiment Hydrographic Program,this study examined the distribution of dissolved inorganic nitrogen(DIN,nitrate(NO_(3)^(-))+nitrite(NO_(2)^(-))),dissolved inorganic phosphorus(DIP)and related N^(*)(nitrogen-anomaly,N^(*)=N-16P+2.9,where N and P are the concentrations of DIN(>1.0μmol/L)and DIP(>0.1μmol/L)),used as an index of N2fixation,in the upper 1000 m of the water column.Nutrient concentrations displayed distinct spatial variability in the upper ocean but became relatively constant at a depth of 1000 m:they were high at low latitudes and in the eastern region,with an obvious nutricline at~150 m(DIN,~32.0μmol/L;DIP,~2.4μmol/L)and then generally increased with depth;they decreased markedly(DIN,~1.2μmol/L;DIP,~0.1μmol/L;at~150 m)at high latitudes and in the western region,where a nutricline was not apparent.The N^(*)index showed significant meridional and zonal variation,with the most negative values located at low latitudes and in the eastern region(~10°N,~150°-170°E),while becoming positive towards the northwest(the north of~18°N,~160°E westward).A N^(*)concentration larger than 2.0μmol/L which often used as an indicator of N2fixation,was observed between 155°E and 165°E;N^(*)values were 2.0μmol/L to6.0μmol/L at~15°-28°N,i.e.,much higher than those in the southern sector(0-2.0μmol/L at~5°-10°N).Zonally,N^(*)decreased gradually from west(-2.0μmol/L to 4.0μmol/L,~145°-165°E)to east(-2.0μmol/L to-8.0μmol/L,~155°W)along~10°N,which was consistent with the distribution of Trichodesmium abundance and N2fixation rates.Furthermore,since such region was also supplied with aeolian deposition,high N^(*)was probably not only induced by N2fixation but also influenced by iron and/or nitrogen deposition.
