The Mai Po Nature Reserve and Inner Deep Bay Ramsar site are an important area of unique ecology and high biodiversity. In this study, environmental strains of Aeromonas hydrophila MP-2, A. salmonicida MP-3, Vibrio vulnificus MP-4 and V. cholerae MP-1 were isolated and examined for their responses to UV exposure, ferric (Fe³⁺) ions and H₂O ₂ challenge under laboratory conditions. In addition, microbial growth data were used to obtain important parameters of bacterial growth including lag phase, specific growth rate and maximum biomass yield for comparison. It was found that V. vulnificus MP-4 was the most sensitive to UV and Fe³⁺ treatments. A. salmonicida MP-3 was only inhibited by 100 mM H₂O₂ while the other three strains did not show any growth at 10 mM H₂O ₂. Our experimental results indicated that environmental isolates of Aeromonas spp. and Vibrio spp. possess different responses for survival under these treatment conditions.