The Study On Living Coccolithophores Community Of The South China Sea In Inter-monsoon Period 2017

We carried out two investigations on living coccolithophores(LC)and their community structure in central South China Sea(10.0°N?22.0°N,110.0°E-118.5°E)in spring inter-monsoon period and western South China Sea(11.00N?19.50N,110.0?113.5°E)in autumn inter-monsoon period 2017.We set up 69 stations,including hydrological,chemical and biological parameters.In this study,we mainly discussed the species composition,cell abundance,dominant species and their distribution,water column integral biomass and community diversity of LC.In order to find the environmental factors that affect the growth distribution of the main species,we discussed niche characteristics of dominant species combined with the Canonical Correlation Analysis(CCA)in this survey.As the largest marginal sea in the western Pacific,the South China Sea located in the tropical monsoon climate zone,the surface seawater circulation is strongly driven by the monsoon.There is an invasion of Kuroshio near the Luzon Strait,and the South China Sea is a typical low nutrient sea area.Actually,there are many upwellings accompanied by cold vortex in coastal areas such as the coast of Guangdong,the eastern of Hainan Island and Vietnam.Another important physical phenomenon,mesoscale eddy,also brings rich nutrient from the deep seawater to the surface in the north of the South China Sea and open water of Vietnam.Which is conducive the gro,wtih of phytoplankton such as LC and will bring a high productivity zone.We used the polarized light microscope to identify and counted the cell abundance and species number of LC.Totally 34 stations and 201 samples in the spring of central South China Sea,and 36 LC taxa was diagnosed.Coccolith species were 28 and were dominated by Emiliania huxleyi,Gephyrocapsa oceanica,Florisphaera profunda,Helicosphaera carteri,Coronosphaera rrmediterranea and Umbilicosph.aera sibogae.The abundance of coccolith ranged was 0.202-1579.839x103 coccoliths/L and the mean was 106.922×103 coccoliths/L.The water column integral biomass of coccolith above 200 m ranged from 1.×4641 03 to 351.656×103 coccoliths/m2 and the average value was 115.225×103 coccoliths/m2.Coccolithophore species were 30 and were dominated by E.huxleyi,F.profunda,G.oceanica,Algirosphaera robusta,Oolithotus antillarum and Umbellosphaera tenuis.The abundance of coccolithophore ranged was 0.202?233.261 ×103 cells/L and the mean was 15.087×103 cells/L.The water column integral biomass of coccolith above 200 m ranged from 0.921 ×103 to 72.266×103 cells/m2 and the average value was 15.991 ×103 cells/m2 coccoliths/m2.The vertical distribution showed that the maximum abundance of coccolithophore appeared in 75 m layer,but coccolith tended to the layer of 75 m to 200 m.Meanwhile,we set up 34 stations and 201 samples in the autumn of western South China Sea,and 37 LC taxa was identified.Coccolith species were 25 and were dominated by E.huxleyi,G.oceanica,F.profunda,U.sibogae,H.carteri and Calcidiscus leptoporus.The abundance of coccolith ranged was 0-4671.407R×103 coccoliths/L and the mean was 221.343×103 coccoliths/L.The water column integral biomass of coccolith above 200 m ranged from 15.219 to 1394.765x103 coccoliths/m2 and the average value was 244.046×103 coccoliths/m2.Coccolithophore species were 30 and were dominated by E.huxleyi,F.profunda,G.oceanica,A.robusta,O.antillarum and U.tenuis.The abundance of coccolithophore ranged was 0-66.046x103 cells/L and the mean was 8.524x103 cells/L.The water column integral biomass of coccolith above 200 m ranged from 2.430 to 16.146×103 cells/m2 and the average value was 8.361×103 cells/m2 coccoliths/m2.The vertical distribution showed that the maximum abundance of coccolith appeared in 75 m layer,but coccolithophore tended to the layer of 50 m to 100 m.E.huxleyi,G.oceanica and F.profunda were dominant taxa commonly from the species composition at each station in the two cruises.E.huxleyi and G.oceanica were dominant in the near shore and F.profunda was the dominant species in the middle basin.The result of CCA showed that temperature,salinity,water depth and silicate were the control factors in the central South China Sea,but all the environment parameters could affect the distribution of species except ammonium.All this indicated that the main species have their distribution characteristics and physiological and ecological habits,the difference of seasons and sea area is not obvious.Three different niche types were found by analyzing the niche of dominant species based on environmental factors.A lot of researchers studied the LC communities in the South China Sea,this study can enhance the study of LC communities and its distribution of the South China Sea in order to make a contribution of basic data to the study of carbon cycle in the South China Sea.