Comparison Of Microbial Communities Between Sediments And Water Columns From The Yellow River Estuary

Microorganisms,especially the bacteria and archaea,play critical roles in global biogeochemical cycling,energy flowing and ecology balancing.Estuary,as the confluence of river and marine,marine and land,has violently gradients change of salinities and substances concentrations,and bears great ecological pressures.Fortunately,microbes,as the most important participant keeping balance of estuarine ecology,play irreplaceable parts in eliminating the estuary ecological loads.The Yellow River Estuary(YRE)is the confluence of Yellow River,Bohai Sea and Laizhou Bay,and is near the Shengli Oil Field.Amounts of sediments,pollutants and surrounding anthropogenic activities lead to extreme complexities of environment in YRE.So far,microbial researches on the YRE are very limited,and a comprehensive study about microbial abundance and diversity in water and sediment samples from YRE is never reported.In the present study,we sampled water and sediment samples from five different typical sites in YRE,then studied their bacterial and archaeal abundance and diversity using quantitative PCR(q PCR)and high-throughput sequencing targeted the 16 S r RNA gene.The main results are as follows:(1)The q PCR results indicated that sediments' bacterial 16 S r RNA gene abundance ranged from 6.44×107 to 1.74×109 copies/g,while archaeal 16 S r RNA gene abundance varied from 7.86×105 to 2.12×107 copies/g among sites.For water samples,the bacterial 16 S r RNA gene abundance ranged from 6.23×105 to 1.16×107 copies/m L,and archaeal 16 S r RNA gene abundance varied from 2.13×103 to 4.10×104 copies/m L.Microbial abundance in sediments was higher than that in comparative water columns.Bacterial diversity was higher than archaeal in the same type of sample.The ratio of bacterial and archaeal 16 S r RNA gene abundance was closely related with the sample type,which is <100 in sediment samples and >200 in water samples.Microbial abundance in water samples was more sensitive to the environmental factors(such as the p H,dissolved oxygen and the ammonia).(2)High-throughput sequencing obtained 201836 valid bacterial sequences and 86,849 archaeal sequences,had an average of about 20000 valid bacterial and 8700 archaeal sequences for each sample.We divided OTUs(Operational Taxonomic Units)using a threshold of 97% similarity of sequences,and obtained 35378 bacterial and 6704 archaeal OTUs.After classification of the OTUs,a total of 27 bacterial and 4 archaeal phyla and some unclassified microbes were obtained.(3)Dominant microbial communities which sequence relative ratio was more than 1% were compared between sediment and water samples.On the dominant bacterial phylum(class)level,Alphaproteobacteria,Actinobacteria,Cyanobacteria,and Verrucomicrobia were more dominant than those in sediment.While in sediment,Deltaproteobacteria,Acidobacteria,Chloroflexi,Planctomycetes,Gemmatimonadetes,Nitrospirae,Spirochaetes,Chlorobi and Unclassified Bacteria were more predominant than those in water.Meanwhile,Betaproteobacteria,Gammaproteobacteria,Bacteroidetes,Firmicutes,Deferribacteres and Lentisphaerae had no significant differences of relative abundance.On the dominant bacterial family level,Comamonadaceae,Methylophilaceae,Rhodobacteraceae and Flavobacteriaceae were more dominant in water than those in sediment.In sediment,Sinobacteraceae,Anaerolineaceae,Nitrosomonadaceae,Streptococcaceae,Desulfobacteraceae,Desulfobulbaceae,Nitrospiraceae were more predominant.For archaea,Euryarchaeota and Thaumarchaeota were the predominant phyla,which were nearly accounted for 50% of the total sequences,respectively.On archaeal class level,only the Halobacteria and Thermoplasmata had significant distribution differences in water and sediment samples(P<0.05).On archaeal genus level,the dominant archaea mainly distributed in sediments and the site E of water sample,such as Methanosaeta,Methanosarcina,Nitrososphaera,Methanoregula,and Nitrosoarchaeum.Among water samples,site A,B,C and E had the most dominant genus of Nitrosopumilus(45.52%-50.87%).Most of the dominant microbes were closely related to the high efficient metabolism of carbon,nitrogen and sulphur,which indicated that microbes of YRE played very important roles in eliminating pollutants and keeping ecological balance in the Yellow River Estuary.(4)OTU-based ?-diversity results showed that bacterial diversity was higher than archaeal diversity,and there was higher microbial diversity in sediment than water from the YRE.Sampling sites near the land exhibited a higher microbial diversity than those sites which were far away from land.Hierarchical clustering trees of dominant microbial communities(phylum,class,family or genus level)in samples from YRE indicated that there was notably bacterial but not archaeal communities differences between water and sediment.OTU-based ?-diversity showed that water sample from site E had more species similarity with sediment samples but not with other water samples.(5)Pearson correlation analysis and the RDA(Redundancy Analysis)indicated that microbes in water samples were more sensitive to the environmental factors than sediment samples from YRE,and p H,salinity,dissolved oxygen,nitrate and ammonia were the key factors to influence the microbial communities in the Yellow River Estuary.