We used ecological simulation to study changes in the population structure of bacteria in water during the decomposition of into a 500 L glass tank and measured chemical oxygen demand (COD) and heterotrophic bacteria and analyzed the structure of the bacteria population at different stages using PCR-DGGE. We observed an initial increase in DO, COD, and the abundance of aerobic heterotrophic bacteria as the degree of decomposition of increased, followed by a decrease in COD and aerobic heterotrophic bacteria abundance. The bacterial population in the water consisted primarily of ) and Proteobacteria (60.61. We observed a significant change in the species structure during the decomposition process. During the initial stage of decomposition, were dominant, but were replaced by α-, γ-, and ε-Proteobacteria during the latter stages of decomposition. Our results provide insight into predicting the influence of breakouts in marine environment.