ENVIRONMENTAL ASSESSMENT OF DELAWARE BAY WATER AND OYSTER Crassostrea virginica FOR TOTAL BACTERIA AND TOTAL VIBRIO

Primary objective of this project is to investigate relationship between water quality and total bacteria and Vibrio concentrations. The presence of total bacteria and total Vibrio in seawater and oyster samples collected monthly from three sites in the Delaware Bay near the mouth of the Broadkill River in Lewes, Mispillion River in Slaughter Beach, and Murderkill River in Bowers Beach was determined from June through October 2016. Lewes, Slaughter Beach, and Bowers Beach are located 8, 24, and 40 km away from the Atlantic Coast, respectively and have different habitat characteristics.  Previous research findings show a positive correlation between increased water temperature and the abundance of Vibrio vulnificus and Vibrio parahaemolyticus, while a correlation between the Vibrio species and salinity is not apparent.  Our research indicated that Bowers Beach had the highest number of colony forming units  (cfu) of  total bacteria (with the exception of October) and total Vibrio (Vibrio vulnificus and Vibrio parahaemolyticus) in both seawater and oyster samples  even though the salinity was the lowest of all three sites (Figures 1a-d).  An exponential increase in cfu on 21-June seemed to have no correlation to temperature or salinity. On 10-October, the abnormally higher numbers of total bacteria and Vibrio cfu in water samples from the Lewes site have been attributed to a severe weather system that brought in excess of 30 cm of rain in 24 hours to the area on 3-October, and heavy thunderstorms on 9-October. Our research findings confirm that there are other water quality attributes different than temperature and salinity such as turbidity or particulates plays some roles with presence and concentration of total bacteria and Vibrio.