TITLE: Re-immersion time for reduction of Vibrio parahaemolyticus and Vibrio vulnificus to ambient concentrations in Eastern Oysters
NOAA NERTO Mentor: John Jacobs, NCCOS/Oxford, NOAA NOS
Oyster aquaculture is an important industry in the State of Maryland. When oysters are grown in submerged cages fouling organisms attach to the cage and oysters, impacting water flow and feeding. To reduce fouling, farmers remove cages and oysters from the water for a desiccation period for up to 24 hours. This has been recognized to elevate levels of Vibrio spp., heterotrophic bacteria found in coastal waters world-wide.
Some species such as V. vulnificus cause illness in people associated with consumption of raw shellfish including gastroenteritis, and in more extreme cases, mortality. Oysters can depurate Vibrio, and a 14-day re-immersion period has been suggested as adequate to return to background levels. Currently, there have been no studies specific to Maryland waters that examine Vibrio levels following antifouling dry periods and re-immersion for various intervals.
To address this information gap, we initiated ISSC-sponsored research to determine the time needed to return V. vulnificus levels to background and to determine whether salinity, temperature, or intersite differences impact depuration rates. V. vulnificus levels were measured using the most-probable number enrichment protocol followed by real-time PCR to determine presence/absence. Preliminary data from one site suggests that a 7-10 day period is sufficient to reduce Vibrio vulnificus levels to background; data from other sites is being processed.