Temporal And Spatial Distribution Of Bacterial Diversity In Seawater Of Changjiang Estuary And Adjacent Areas

The bacterial abundance,community composition,temporal and spatial distribution in the surface seawater of Changjiang Estuary and adjacent areas were studied by DAPI direct count,bacteria clone library and high-throughput sequencing technology.The relationship between bacterial community structure changes and environmental factors was also analyzed.We sampled surface seawater in 10 stations in Changjiang Estuary and adjacent areas,and studied the bacteria in seawater environment by DAPI direct count and bacteria clone library analysis.The results showing high abundance of bacteria in Changjiang Estuary and adjacent areas.But the variation of biomass was large,the trend of bacterial abundance increased from Changjiang Estuary to the open sea.In total,11 phyla were identified,including Proteobacteria,Bacteroidetes,Actinobacteria,Cyanobacteria,Firmicutes,Chloroflexi,Acidobacteria,Planctomycetes,Verrucomicrobia,Fibrobacteres and Tenericutes.Proteobacteria(60.61%)was the dominant group,followed by Bacteroidetes(15.18%)and Actinobacteria(14.79%).In addition,Tenericutes and SAR groups were very rare in the study area.Bacterial community of 10 stations were divided into 6 categories by MDS and cluster analysis.RDA results indicated that bacterial community structure was strongly correlated with TP,DO,pH and TSP.Therefore,the bacteria of Changjiang Estuary and adjacent areas was abundant and diversified in complicated structures,reflecting the impacts of local aquaculture activities and regional marine physical-chemical settings,for example,the oxygen depletion at sea bottom and Changjiang water dilution.We sampled 9 surface seawater samples in D03 anchor station in Changjiang Estuary and adjacent areas,and studied the diel variation of bacterial abundance and community structure by DAPI direct count and high-throughput sequencing technology.The results showing high abundance of bacteria in surface seawater,but the biomass was larger in the daytime than at night.The diel variation of bacterial abundance was mainly affected by pH and PO43-.In total,28 phyla were identified,including Proteobacteria,Bacteroidetes,Actinobacteria,Cyanobacteria,SAR406,Verrucomicrobia,Tenericutes,Chloroflexi,Acidobacteria and some groups of low abundance.Among them Proteobacteria was the dominant group of all samples,followed by Bacteroidetes and Actinobacteria.The variation trend of each bacterial group along with the diel fluctuation was different.The factors that result in the change of bacterial community structure were tides,light,nutrient,ingestion of zooplankton and viral lysis.These results fully indicated that the surface seawater of Changjiang Estuary with a high level of bacterial diversity.The change rule and influence factors of bacterial community structure along with the diel variation was very complex.