Effect of water treatment on the growth potential of Vibrio cholerae and Vibrio parahaemolyticus in seawater

In laboratory experiments we added Vibrio cholerae and Vibrio parahaemolyticus to bottles with seawater previously treated by filtration, UV, chlorine or ozone. The purpose was to investigate the influence of different treatment techniques on the growth potential of these bacteria in simulated ballast water tanks. Residual oxidants were removed before inoculation, and the bottles were incubated at 21 ± 1 °C. The growth potential of the vibrios was investigated in two different experimental setups, i.e. in presence and absence of added natural microorganisms. In general, V. cholerae and V. parahaemolyticus rapidly lost their culturability after inoculation and storage in untreated seawater, but showed increased survival or growth in the treated water. Highest growth was observed in water previously exposed to high concentrations of ozone. Addition of natural microorganisms reduced the growth of V. cholerae and V. parahaemolyticus.

► We added Vibrio cholerae and Vibrio parahaemolyticus to seawater and treated seawater.
► The vibrio concentrations decreased in untreated seawater over time.
► Growth or increased survival of the vibrios were observed in treated water.
► Native microorganisms reduced growth of vibrios.
► Treatment of ballast water may alter the growth potential of pathogenic bacteria.