Relationship between bacterial density and the physical and chemical factors in higher-place ponds of Litopenaeus vannamei

Through continuous periodic sampling, determination and analysis, the varying regulation of the density of heterotrophic bacteria and vibrio in two intensive shrimp(Litopennaus vannamei) higher-place ponds was investigated. At the same time, the correlation between the physical and chemical factors and the density of heterotrophic bacteria and vibrio were analysed. The result showed that there was a continuously slow rise in the amount of heterotrophic bacteria, which altered in the range of 9.07×103 ~ 2.13×105cfu/mL, averanging 6.45×104 cfu/mL. The amount of vibrio in two ponds demonstrated a consistent trend, while the amount changed in the range of 2.12×102 ~ 2.91×103cfu/mL, the level of vibrio amount increased from the early stage to the middle stage during the culture period, and then decreased in the later stage because of increasing water exchange. The correlation analysis indicated that the amount of heterotrophic bacteria and vibrio had a remarkably negative correlation with transparency, the value of DO and pH. Positive correlation with the content of COD and TSS, and the same positive correlation with the amount of vibrio and content of TSS(P<0.05) were also observed.