Bacteriavariationin Litopenaeus vannamei high level ponds and its relation withphysical-chemical factors

From April to August, 2008, we had collected water sample in high level ponds of Litopenaeus vannamei at Honghai Bay, Shanwei, Guangdong to studyits significant bacterial population and physical-chemical factors, and to analyze the variation of bacterial population and its relation with environmental factors during the culture period. The results show that the amounts of heterotrophic bacteria, Vibrio and Bacillus in water change rather greatly. Specifically, the heterotrophic bacteria range from 1.35104 cfumL-1 to 1.39106 cfumL-1, 4.73105cfumL-1 on average; as for Vibrio, the range is 1.05103~5.20104 cfumL-1, 1.80104 cfumL-1 on average; and for Bacillus, the range is 0.11103~4.30103 cfumL-1, 6.6102 cfumL-1 on average; the amount of fecal coliform is generally less than 1.0102 cfuL-1 with an average of 0.97102 cfuL-1, which is muchbelow the standardfor pollution-free food and aquaculture water quality. Additionally, the correlation analysis between bacteria amount and physical-chemical factors reveals that the heterotrophic bacteria amount and DO show a significant negative correlation (P0.05), while Vibrio amount shows a very significant negative correlation with pH (P0.01) and a significant positive correlation with COD and TP (P0.05). The multi-factor partial correlation analysis shows that the correlation between heterotrophic bacteria, Vibrio and DO, pH, COD, TP is not significant (P0.05). To sum up, L.vannamei grows well in the investigated ponds, which is proved to be a safe and relatively healthy system, and the bacteria amount in water environment is affected and restricted by biological, environmental and artificial factors.