Abstract: Bacterium,as one of important factor to maintain aquaculture water stability,is often used to evaluate the quality of aquaculture water. Microecological preparations are widely applied in aquaculture water to remove harmful substances. This work aims to study the changes of bacterial community structure and bacteria diversity after adding microecological preparations into cultured seawater during different seasons,and to explore the effects of environmental factors of water quality on bacterial community. The high-throughput sequencing technology was used to amplify the bacterial 16S rRNA V3 and V4 regions,and the distribution and diversity of bacterial community in cultured seawater were analyzed after adding completely commercial microecological preparations in the winter,spring and summer. Redundancy analysis（RDA）was employed to analyze the relationship between water quality and bacterial communities in different seasons. The diversity was rich,the Proteobacteria and Bacteroides were main dominant bacteria shared in three seasons. Of them the Tenacibaculum（38.28%）,Zobellella（30.78%）and Halomonas（13.55%）were dominant in the winter,the Glycocaulis（34.00%）,Halomonas（11.36%）and Planktosalinus（9.67%）were dominant in the spring,and the Pseudofulvimonas（28.94%）,Zobellella（17.51%）,Planktosalinus（15.86%）,Marinobacter（12.30%）were dominant in the summer,the bacterial genera varied obviously in different seasons. RDA analysis showed that environmental factors at different stage affected bacterial community in various ways,and temperature,salinity,pH,and dissolved oxygen presented significant correlations with abundance of 10 dominant genera in 3 seasons;the dominant genera were positively correlated with salinity and dissolved oxygen in winter and spring,and positively correlated with temperature and pH in summer. In conclusion,microecological preparations demonstrate the great advantages in purifying aquaculture waters,each in whole may play each own regulation ability though the structure and diversity of bacterial community are changed in different seasons. This study provides new ideas for further treating cultured seawater and applying new microecological preparations.

Key words: cultured seawater, high-throughput sequencing, bacterial diversity, bacterial community structure