The Effects of Temperature and Salinity on Vibrio Species in Breton Sound Estuary

Abstract

Vibrio vulnificus and V. parahaemolyticus are Gram negative bacteria indigenous to estuarine and marine environments. Both species of Vibrio are human pathogens known to cause infections that, in severe cases, can lead to death in humans through consumption and direct contact with water. The purpose of this study is to determine the spatial and temporal dynamics of total V. parahaemolyticus and V. vulnificus in response to temperature and salinity, and to establish a statistical relationship between Vibrio spp. concentrations and salinity and temperature. Water samples were collected from seven sample locations within the Breton Sound Estuary from February 2011 to March 2012. Results from the study indicated that concentrations of total Vibrio spp., V. parahaemolyticus, and V. vulnificus were positively correlated with temperature. There was no correlation between mean concentrations of Vibrio spp., V. parahaemolyticus, and V. vulnificus per sample date and salinity. However, while it was not statistically significant, the mean concentrations of Vibrio spp., V. parahaemolyticus, and V. vulnificus per sample location were positively correlated with salinity. Statistical analyses were conducted to investigate the interactions between salinity and temperature and how they affect concentrations of Vibrio. A two-way ANOVA indicated there was a statistically significant interaction between the effects of salinity and temperature on V. parahaemolyticus and V. vulnificus. An ANCOVA was conducted to analyze the effects salinity had on V. parahaemolyticus and V. vulnificus, while controlling the effects of temperature. The results of the ANCOVA revealed statistically significant positive correlations between temperature and the abundances of V. parahaemolyticus and V. vulnificus cultured from waters exceeding a salinity level of 2.4. The ANCOVA results also showed that although not statistically significant, there was a negative correlation between temperature and the abundances of V. parahaemolyticus and V. vulnificus cultured from waters with salinity levels less than 2.4. This study illustrated the importance of simultaneously assessing the effects of salinity and temperature on V. parahaemolyticus and V. vulnificus abundance. While this study proved there is an interaction between salinity and temperature effects on the abundances of V. parahaemolyticus and V. vulnificus, further research should be conducted in to determine how the dynamics of the temperature/salinity relationship differ in different climate zones.