Analysis On Microbial Community Characteristics In The Typical Sea Areas In Guangdong Province

Microorganisms play an important role in the material cycle and transformation process ofmarine ecosystem. Two typical sea areas of Guangdng Province, Guishan Island in Zhuhaiwhich was mainly affected by human activities and Nan’ao Island in Shantao whichoperated large-scale mariculture activities, were chosen in present study. The phylogeneticand metabolic features of microbial communities in these two areas were analyzed usingcommunity-level physiological profiling (CLPP) and denaturing gradient gelelectrophoresis (DGGE). In addition, potential probiotics were isolated and screened fromseaweed Gracilaria lemaneiformis cultivation system. Combining the bioremediationroles of seaweed and probiotic, the purification effects of Gracilaria-probioticcollaborative system on water quality was explored. These results will provide the datasupport and technical reference for environmental remediation and the sustainabledevelopment of mariculture.The main results of the present research are as followed.1. Microbial community structure and environmental characteristic in the water andsediment from12sampling sites (S1~S12) of Guishan Island were analyzed using CLPPand DGGE. The results showed that microbial community metabolic activity and diversityindex of the surface sea waters in the mariculture areas (S6, S7, S8) and the sites affectedby human activities (S11, S12) were higher than that in the other sites. The dominantbacteria in the surface water belonged to Proteobacteria, especially γ-Proteobacteria andα-Proteobacteria. Except for S10and S12, the dominant bacteria specie wasPseudoalteromonas sp., which belonged to γ-Proteobacteria. In the sediment,17dominantbacteria belonged to γ-Proteobacteria,-Proteobacteria, Bacteroidetes, Acidobacteria andActinobacteria, with percentages of27.8%,19.8%,23.1%,22.2%and7%, respectively.γ-Proteobacteria was the only common predominant group occurring both in surface waterand sediment.The result of redundancy analysis (RDA) based on CLPP and DGGE withenvironmental factors showed that total phosphorus (TP) and salinity were the majorenvironmental factors influencing the microbial community structures in the surface waterin Guishan Island. The bacterial community structures in the mariculture areas and thesites affected by human activities (S6, S8, S11and S12) are greatly influenced by TP,salinity and TN. Furthermore, the relative percentage of-Proteobacteria in the sediment and the concentrations of heavy metals (Ni, Cr, Fe, Pb and so on) had significantlypositive correlation (P <0.05).2. The phylogenetic and metabolic characteristics of microbial communities insurface water and sediment of Baisha Bay mariculture areas in Nan’ao Island wereexplored in February,2012. G. lemaneiformis cultivation zone (GZ), fish culture zone (FZ)and control zone (CZ) were chosen. The results showed that the bacterial communities inGZ had higher microbial metabolic capabilities and phylogenetic diversities. Forty-fourdominant bacterial species belonged to seven major phylogenetic groups (α-Proteobacteria,Flavobacteria, γ-Proteobacteria, β-Proteobacteria, Cyanobacteria, Firmicutes andActinobacteria). The most dominant bacteria in CZ and GZ were α-Proteobacteria (39.9%and34.5%), while that was Flavobacteria in FZ, with the percentage of32.2%. Moreover,the concentrations of nitrogen, phosphorus and COD in GZ were lower than that in FZ.Microbial communities in surface sediment in FZ had the highest metabolic activitiesand utilization for six kinds of carbon source. The dominant bacterial species belonged tonine major phylogenetic groups (α-Proteobacteria, γ-Proteobacteria, δ-Proteobacteria,ε-Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, Bacteroidetes andPlanctomycetes). γ-Proteobacteria and δ-Proteobacteria were the predominant group, andthe percentage were39.6%and19.9%in GZ. The phylum of Proteobacteria in CZ, GZand FZ were account for60.1%,68.8%and66.8%, respectively. The concentrations of TN,TP and TOC in surface sediment of FZ were significantly higher than that of GZ and CZ(P<0.05). Microbial community composition was influenced by the TOC, TP and TN inthe sediments.3. Six strains of Bacillus (three Bacillus pumilus GS6, GS11, GS12and three Bacilluslicheniformis GS4, EGW1, EGS4) were isolated and screened from Gracilaria cultivationsystem. According to the utilization of carbon source, B. pumilus GS11was selected forthe research on purifying effect of Gracilaria-probiotic collaborative system.The purifying effect of Gracilaria-probiotic collaborative system showed that B.pumilus GS11could grow well in the feed leaching liquor in the group ofGracilaria-bacteria added directly and the group of bacteria immersed. The growth ratesof Gracilaria-bacteria collaborative group were significantly higher than the group ofGracilaria (P<0.05) after7d cultivation, with12.2%and11.7%, respectively. In thesetwo collaborative groups, nitrate, nitrite, ammonia, phosphate and COD in the feedleaching liquor were absorbed or degraded. The degradation effect on ammonia, phosphateand COD were significant in these two groups, with the percentage of51.3%and54.4%, 63.0%and61.3%,53.6%and52.1%, respectively. Furthermore, the microbial metaboliccapabilities in the feed leaching liquor in two collaborative groups were significantlyhigher than that of the control group and Gracilaria group (P<0.05). Given to thecharacteristics of mariculture ecosystem, Gracilaria cultivation system with probioticimmersed bacteria would be a possible way to improve the mariculture environment.