Microbial Community Composition Of Liaohein Seawater And Pearl River Estuary In Sediment

Estuary plays an important position in the global ecosystem, and the carbon and nitrogen cycle of estuary plays a key role in the global material circulation and energy flow, because microorganisms almost can participate in all of the biogeochemical cycles. Study of microbial community structure and abundance in estuary seawaters and sediments can provide the basic data to understand the ecosystem in the region.The occurrence of total and culturable bacteria in Pearl River estuary seawater sample in August 2014 was studied using 2216 E plates and flow cytometry,and the abundance and production of bacteria with the ircorrelations with envrionmental factors were investigated.The abundance of culturable bacteria range from 3.70×102 to 1.42×103 CFUs/ml, the abundance of total bacteria range from 5.12×105 to 1.61×106 cells/ml, the bacterial production range from 0.03 to 0.40 mg/m3/h from the pearl River estuary to the northern South China Sea in the horizontal direction. The abundance of culturable bacteria range from 1.08×103 to.00×103 CFUs/ml, the bacterial production range from 0.01 to 0.08 mg/m3/h in the vertical direction,and the surface layer bacteria in seawater productivity was significantly higher than the bottom. Relativity and redundancy analysis suggest that temperature, salinity, nitrate, silicate, nitrite and phosphate were highly statistically significant factors to total bacteria and bacterial production with the surface layer seawater in the horizontal direction?P<0.05?. The nitrite was highly statistically significant factors to culturable bacteria?P<0.05?, temperature, salinitywere highly statistically significant factors to bacterial production in the vertical direction?P<0.05?. Oobviously, the abundance of total bacteria were general 2³ order of magnitude higher than that of culturable bacteria which reprensented many unculturable bacteria in there sea area,and the sea surface with life activity was higher than bottom.To elucidate the diversity of CO₂ fixation and its relationship with environmental factors in surface water of northern South China Sea, the coding gene form I?cbbL?and form II?cbbM?(that encodes Ribulose-1,5-biphosphate carboxylase/oxygenase?RubisCO?were chosen as biomarkers in Calvin-Benson-Bassham cycle?a common carbon fixation pathway for chemolithoautotrophic microorganisms?to analyze the Carbon sequestration genetic diversity. The Illumina Miseq sequencing method and multivariate statistical analysis were employed. The cbbM gene was not detected in any of samples, while the cbbL gene was found in all samples. The cbbL-containing genetic communities were dominated by Proteobacteria, Cyanobacteria and Firmicutes, in which ?-Proteobacteria?45.3%?, Cyanobacteria?30.9%?, ?-Proteobacteria?23.8%?were predominant subpopulation. There were some kinds of differences between the nearshore station of A9 with other stations, in which Allochromatiu,Thiobacillus and Thiohalomonas were unique species existing in A9 station. Relativity and redundancy analysis suggest that water temperature, salinity, Nitrate, Nitrite, Silicate were highly statistically significant factors. Temperature and salinity were positively?P<0.01?, while the other three factors negatively influenced CO2 fixation gene of cbbL gene abundance?P<0.01?.The present study focused on the external of the Liaohe estuary waters, but absented systematic research to the ecological functions of archaea in the brackish mixing zone. The Illumina Miseq sequencing and Real time PCR method analysis were employed to explored archaeal community structure and abundance under salinay gradient.The results show that:Thaumarchaeota and Euryarchaeota were dominated archaeal groups in liaohe estuary. The salinay and temperature were dominate factors to influence archaeal community structure in liaohe estuary. The mouth of low salinity zone was nitrogen fixation and carbon sequestration, but in the high salt waters was mainly nitrogen fixation. Archaeal 16 S rRNA gene abundance was 5.1×105³.8×106copies/g in sediments in liaohe estuary, which showed the large number of archaeal groups to distribute in liaohe estuary. Temperature and salinityand Archaeal 16 S rRNA gene abundance were significant positivelyNO3-, SiO32-and Archaeal 16 S rRNA gene abundance were significant negatively, indicating temperature, salinity, NO3- and SiO32-concentration was mainly factors to influence the distributon of archaeal abundance.