Crassostrea virginica play a significant role in the ecosystem and food chain. The filtration of water by the oysters results in the removal of sediments, bacteria, and nutrients which leads to the bioaccumulation of different types of microorganisms in oysters such as Vibrio spp. Of various Vibrio species found in the aquatic environment common human pathogens, including Vibrio vulnificus, and Vibrio parahaemolyticus, cause wound infections, and gastrointestinal diseases. Other Vibrio spp., such as Vibrio coralliilyticus and Vibrio tubiashii are known as shellfish pathogens. Slaughter Beach, Delaware, USA has been considered as a potential area to establish an oyster hatchery. However, Vibrio spp. and water quality parameters remain unknown in this region. The aims of this study are to investigate and evaluate the Vibrio spp., in seawater and oysters and determine the relationship between water quality and total Vibrio spp., levels in oysters and seawater. Water samples were collected from three different sites (DuPont Nature Center, Cedar Creek, and Boat ramp) from June to November 2021 at high and low tides in Slaughter Beach, Delaware. The samples were collected bimonthly. The YSI 556 Multiprobe (Yellow Spring, Ohio, USA) was used to monitor (temperature (°C), salinity (g/L), dissolved oxygen in mg/L, and while a YSI 9500 Photometer was used to monitor chemical water quality (nitrate, nitrite, ammonia, phosphate). Vibrio spp. was monitored from oysters and water samples collected from these three study sites by using Thiosulfate Citrate Bile Salts Sucrose (TCBS. Our preliminary results revealed that the highest presumptive larval pathogenic Vibrio in the seawater was observed in July, August, and October in sites 2 and 3 with a peak at 95 ± 7.2 CFU/100 mL for site 2, and the highest presumptive human pathogenic Vibrio in the seawater was recorded during early July at site 2 (148 ± 40 CFU/100 mL). The highest human pathogenic vibrio in oysters was observed at site 2 during September (3.39 ± 0.01 Log cfu/100ml) and October (2.27 ± 0.03 Log cfu/100ml). Monitoring the pH of the seawater during the high tide and low tide at different sites from July to October demonstrated that the pH remained almost stable in a range from 7.22 to 8.89. Analyzing the seawater temperature from July to October revealed the highest sea temperature during high tide and low tide at site 2 during July with a peak of 28.96 ± 0.56 °C.
Key words: Crassostrea virginica, Vibrio spp., water quality, aquatic ecosystem, oyster hatchery.
Acknowledgments: We acknowledge Delaware EPSCoR NSF Award# 1301765 “Meeting Delaware’s 21st Century Water and Energy Challenges through Research, Education, and Innovation (WICCED)” for funding this project.