The Study On The Characteristics Of Microbial Community In Intertidal Mudflat Of The Yellow River Estuary

The Yellow River estuary intertidal area located in a transitional zone of the junction of land and sea which the environment is complicated undered physical and chemical factors. Microorganisms as an important part of the mudflats environmental ecological system, the role of the microbial community structure characteristics and environmental factors are inseparable. In this paper, we surveyed the Yellow River estuary intertidal area in May, August, November of2012and March2013to study the total number of bacteria, microbial activities distribution characteristics, and to investigate specific functional microbes, secondly to research the structure of the microbial diversity and species richness and the dynamic change regularity of population structure by using polymerase chain reaction-modified gradient gel electrophoresis (PCR-DGGE) analysis method. Results show that:(1) The range of total number of bacteria in August2012, November2012and March2013were0.71×104～8.07×104/g dry sediment,0.84×104～2.04×104/g dry sediment and0.80×104～2.61×104/g dry sediment, average were3.18×104/g dry sediment1.29×104/g dry sedimentå'Œ1.49×104/g dry sediment. In August2012, the total number of bacteria present the trend of in the direction away from the shore increases then reduced, in November2012from north to south four section shows the tendency of increasing, in March2013the trends were different with the section changing. Temperature is the most important factor that results in the change of the total number of bacteria. The number of total bacteria in the Yellow River estuary intertidal area overall is low, the surface layer of vegetation coverage is one of the important factors.(2) The range of microbial activities in August2012, November2012and March2013were1.85-2.53μg/g dry sediment,1.80-2.04μg/g dry sediment and1.67-1.92μg/g dry sediment, average were2.20μg/g dry sediment,1.88μg/g dry sediment and1.78μg/g dry sediment. In August2012, microbial activity showed a trend of decrease after the first increase in offshore directions;In November2012and March2013there were no significant fluctuations.(3) About specific functional microbes, the sulfate reducing bacteria is the main microbial species (communities), the highest number was3.19-3.59xl04/g dry sediment in August8, ammonifying bacteria number is less in general, only in August2012has obvious detection. In November2012three kinds of bacteria were all less except several sections.(4) The microbial community structure in the Yellow River estuary intertidal area has obvious space-time distribution features, the PCR-DGGE fingerprint technique can reflect the characteristics of the distribution of microbial community structure, using this method can effectively obtain information about some characteristics of microorganisms in the region, according to the PCR-DGGE fingerprint and stripe of the DNA in mudflats environment of surface sediment showed the diversity of surface sediment bacteria is relatively abundant, the number of repeated stripes were not high, each station existed certain differences. The sequencing results of predominance bands showed that the advantage species belonging to the Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes and Deinococcus-Thermus, mainly Bacteroidetes. In vertical direction the advantage species belonging to the Proteobacteria, Firmicutes and Bacteroidetes, mainly Proteobacteria. The seasonal variation characteristics in the Yellow River estuary intertidal area showed the microbial community structure in addition to the D2section basically in the close season difference decreases, and when the similarity degree is higher, the farther season interval, the bigger the difference.Temperature have a certain screening effect for microbial community, the temperature change may cause variations of microbial community. The total number of bacteria and microbial activities all has a significant positive correlation with temperature (r=0.4828,0.7327).(5) Using redundancy analysis method (RDA) to determine the influence of environmental factors on the microbial distribution shows that temperature, chlorophyll a, grain size, salinity and TOC are all important factors that influencing the microbial distribution. The primary factor that influencing the microbial community structure distribution characteristics is the geographical position, followed by temperature, the influence of the tidal effect is relatively small. Surface vegetation coverage leading to microbial community on the horizontal distribution of low similarity. And vertical distribution has high similarity, environment changed with depth, lead to the surface and at the bottom of the bigger difference. The research results showed that the influence of particle size on the total number of bacteria and microbial activities is weak (r=0.2005,0.3541). And they both negatively related to the content of chlorophyll a(r=0.3589,0.5394), the latter than the former.