Semester of Graduation

December 2009


Master of Science (MS)


Environmental Sciences

Document Type



Vibrio vulnificus and Vibrio parahaemolyticus are halophilic gram-negative bacteria that are found in warm coastal waters. These two species are the leading cause of fatal shellfish poisoning. The objective of this study was to determine the population dynamics of V. vulnificus and V. parahaemolyticus as impacted by temperature and salinity in Breton Sound and Barataria Bay of Louisiana. Water samples were collected from each water body along s salinity gradient transect monthly from September 2007 through July 2009. Furthermore, from March 2008 through July 2009 sediment and live oyster samples were collected exclusively from the Breton Sound. The population of V. vulnificus and V. parahaemolyticus was measured using the most probable number (MPN) method and plating method. The abundance of putative V. parahaemolyticus and V. vulnificus in Barataria Bay and Breton Sound waters was seasonally dominated by water temperature, but spatially controlled by salinity level. The plate counts indicated that V. vulnificus appeared less abundant in the Gulf waters during colder months than V. parahaemolyticus. Based on the laboratory testing, V. parahaemolyticus appeared to grow better overall at higher salinity levels. The average annual population of putative V. parahaemolyticus and V. vulnificus over all the sampling sites in Breton Sound was slightly higher than that in Barataria Bay. Like that in the waters of Breton Sound, the population of putative V. parahaemolyticus and V. vulnificus in Breton Sound sediments also followed a trend. This research has shown a clear picture of the dynamics of putative V. parahaemolyticus and V. vulnificus populations in Breton Sound Estuary and Barataria Bay. However, further work is needed to (1) continue the PCR confirmation of V. parahaemolyticus and V. vulnificus, and (2) carry out statistical analysis for the relationships between environmental parameters and V. vulnificus and V. parahaemolyticus populations. The work would eventually lead to the establishment of a statistical relationship between the Vibrio concentrations and environmental parameters, in particular salinity and temperature, under a range of tidal, wind, and freshwater input conditions, which could be used to quantify the temporal and spatial variations of the Vibrio distributions in response to the environmental parameters.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Hou, Aixin