Spatial And Temporal Distribution Of Picoplankton And Their Correlation With Environmental Factors In Different Functional Divisions In The Coastal Waters Near Zhoushan

Picoplankton refers to marine plankton with a ball diameter between 0.2?m and 2?m,including:picophytoplankton(prochlorococcus,Synechococcus,Picoeukaryotes),virioplankton,heterotrophic bacteria.They contribute greatly to the global primary production,and were paid much attention by researchers in recent years.To understand the spatiotemporal distribution of picoplankton between different functional areas in the sea area near Zhou Shan,six typical stations were designed in different functional zoning of the coastal waters near Zhou Shan,in the winter of 2017,the spring of 2018,the summer and the fall of 2018,and 24 samples obtained.The abundance of picoplankton was examined with flow cytometry,and their spatial and temporal distribution characteristics were analyzed.To understand the diversity and community structure of heterotrophic bacteria in the coastal waters of Zhoushan,six stations were designed in the middle area between Qingbang Island and Miaozihu Island,and sampled for four seasons from October 2015 to August 2016,24 samples obtained.16S r RNA high-throughput sequencing was performed,and evolutionary trees was constructed using differences in bases between sequences,and the correlationship between heterotrophic bacteria abudance and environmental factors was analyzed.The analysis of the abundance of picophytoplankton showed that Synechococcus(Syn)abundance decreased from winter to spring,autumn and summer in turn,and picoeukaryotes(Euk)abundance decreased from summer to autumn,winter,and spring in turn.Correlation analysis showed that both chlorella and picophytoplankton had a significant positive correlation with p H(P<0.05),and Picoeukaryotes had a significant positive correlation with COD(P<0.05)in spring.Picoeukaryotes had significant positive correlations with NH₄⁺,NO₂^-,and Chl-a(P<0.05)in autumn.Picoeukaryotes and Synechococcus both showed significant correlation with Chl-a Positive correlation(P<0.05)in winter.The analysis results of the abundance of virioplankton and heterotrophic bacteria showed that the seasonal distribution of virioplankton(Vir)was as follows:summer>autumn>winter>spring,and the seasonal distribution of heterotrophic bacteria(HB)was as follows:summer>spring>autumn>winter.Correlation analysis showed that virioplankton and heterogeneous bacteria had a significant positive correlation with p H,a significant negative correlation with COD,and virioplankton had a significant positive correlation with VBR in spring.Heterotrophic bacteria correlated positively with Chl-a in summer and significantly negatively with COD.Virioplankton showed a positive correlation with Chl-a,and a negative correlation with COD in autumn;heterotrophic bacteria showed a positive correlation with p H,and a significantly negative correlation with Si O₃^2-and COD in autumn;virioplankton correlated positively with Chl-a,heterotrophic bacteria had a positive correlation with p H and a significantly negative correlation with COD in winter.This study indicated that the abundance of marine picoplankton is higher in the far-shore waters than in the near-shore waters,and the abundance of picoplankton is lower in the polluted seas than in the clear seas.The abundance of marine picoplankton can directly or indirectly reflect the pollution of the sea area and can be used as one of the indicators for detecting water pollution.The above results are expected to provide valuable reference materials for the protection of the ecological environment and a basic information for a more comprehensive study of the ecological environment in the coastal areas of Zhoushan.894803 effective sequences were obtained by 16S r RNA high-throughput sequencing,including:34 phylums,75 classes,169 orders,336 families,667 genera,1147 species.By contrasting with sequences of higher homology,the heterotrophic bacteria in the 16S r RNA clone library mainly belong to 6 major groups:Alphaproteobacteria,Gammaproteobacteria,Cytophaga-Flavobacteria,Cyanobacteria,Actinobacteria,Betaproteobacteria.The results of RDA analysis indicated that the composition of bacterial communities will change with changes in environmental factors.Actinomycetes had a significantly negative correlation with salinity.Proteobacteria were greatly affected by temperature.The functional prediction analysis showed that the phytoplankton community in Zhoushan fishing ground had prominent functions in the transportation and metabolism of amino acid and carbohydrate,and in the translation and transcription of ribosome structure.More accurate analysis of marine bacterial community structures could be performed with high-throughput sequencing.