Seawater pond polyculture with shrimp,crab and shellfish is a popular culturing model along the east coast of China,and is a relatively closed ecosystem.In such an ecosystem,the main energy and material flows carried through the microbial web are easily affected by cultured species and bait types.By Illumina Miseq analyzing the bacterial V4-V5 region on 16S ribosomal DNA,we have found a complex and diverse bacterial community structure.