Study On Marine Oil Snow(MOS) Formation And Microbial Community Structure In Bioremediation Of Oil-Stained Beach

Oil spill events occur repeatedly in the oceans,though after a series of physical and chemical ways of emergency treatment,some oil still spilt to the beaches with the hydrodynamic effect and polluted the beaches,which seriously affected the ecological and landscape environment of coastal polluted regions.In the wave erosion and tidal effects,part of the oil,suspended substances,and marine micro-organisms can gather to form Marine Oil Snow(MOS).The MOS increased bioavailability of oil and resulted in a degree of natural restoration of contaminated beaches.However,this natural restoration process is relatively slow,in order to speed up the process,we considered adding clay mineral particles to increase the concentration of suspended particulates,which can promote MOS’s generation,this way is called reinforced natural restoration.The final degradation of marine oil is achieved by the role of marine oil degrading bacteria,the formation of MOS is also closely related to the diversity of marine microbial community structures.In this paper,the formation and influence factors of MOS under natural repair condition were studied by a batch of shake flask experiments.Then the effects of kaolin,bentonite,diatomite and different amount of kaolin on the formation of MOS were studied under the condition of natural restoration.Finally,molecular biology techniques were used to analyze the different microbial community structure under different repair conditions(natural restoration and reinforced natural restoration),different phases(solid phase MOS flocs,liquid water environment).The main conclusions are as follows:(1)In the natural restoration,four kinds of MOS could be observed,they are velevty,fibrous,reticular and dendritic;The average sedimentation rate was 0.3451cm/s;The average number of TEPs with a diameter more than 50 μm is 8 and the average total surface area is 1.6×108μm2;The more suitable natural salinity,pH,mixed energy(shaker speed)to form MOS were 35‰,8,160 r/min.(2)In the reinforced natural restoration.Three kinds of clay granite kaolin,bentonite and diatomite promoted the formation of MOS to some extent,among which kaolin had the most obvious effect,and the optimum dosage of kaolin was 5mg/100ml.(3)In the natural restoration,The richness of microbial community in water is larger than that in MOS flocs,and species distribution is also more uniform;the dominant genus of the top three relative abundance microbes are same in two phases;The water contains five unique genus,but MOS flocs do not contain the unique genus.(4)In the reinforced natural restoration,The richness of microbial community in the flocs is greater than that in the water,but the species distribution in the water is more uniform;The dominant genus of the top two relative abundance microbes were Alcanivorax,Idiomarina and Alcanivorax,Paraglaciecola respectively.The MOS contain three unique strains while the water contains only one unique genus(5)The comparative analysis of microbial community in MOS flocs between natural restoration and reinforced natural remediation showed that,the reinforced natural restoration of adding kaolin increased the abundance and evenness of microbial community in MOS flocs;When it comes to the comparative analysis of microbial community in water between natural restoration and reinforced natural remediation;The reinforced natural restoration also increased the abundance and evenness of microbial community in water.(6)The comparative analysis of the overall microbial community between natural restoration and reinforced natural restoration showed that,the reinforced natural restoration increased the abundance and evenness of overall microbial community;and it reduced the abundance of Pseudoalteromonas,Pseudomonas,Amorphus and Flavobacterium significantly,while increased the abundance of Idiomarina,norank_f_ODP1230B8.23,and unclassified_f_Flavobacteriaceae.(7)At the level of the class,the main classes of natural remediation were Gammaproleobacteria,Alphaproteobacteria,Flavobacteria and Bacillus,the main classes of reinforced natural remediation were Gammaproteobacteria,Flavobacteria,Alphaproteobacteria,Clostridia;Theirs common oil degrading bacteria are Alcanivorax,Pseudoalteromonas,Idiomarina,Pseudomonas,Vitellibacter,Paraglaciecola,Flavobacterium,Sulfitobacter and Cycloclasticus.