Depuration rates of northern quahogs, Mercenaria mercenaria (Linnaeus, 1758) and eastern oysters Crassostrea virginica (Gmelin, 1791) in ozone- and ultraviolet light-disinfected seawater systems

The relative elimination rates of a diverse group of indicator microorganisms from hard-shelled clams (Mercenaria mercenaria ) and eastern oysters (Crassostrea virginica ) were evaluated in ultraviolet light and ozone-disinfected seawater systems. The indicator organisms included vegetative bacteria (fecal coliforms, Escherichia coli , and enterococci), a spore-forming, anaerobic bacterium (Clostridium perfringens ), and a group of bacterial viruses (male-specific bacteriophages). The addition of ozone to seawater resulted in the rapid inactivation of both the vegetative bacteria and viral indicators. Of the indicators used in this study, C. perfringens was the least affected by ozone. Inactivation and elimination rates, however, were not higher in shellfish placed in ozonated tanks than in shellfish in the ultraviolet light treated control tanks. Bacteriophages were eliminated at a much slower rate than were vegetative or spore-forming bacteria. Regardless of the disinfection system, bacteriophages persisted in depurating shellfish for more than 2 weeks.