Performances of common UV disinfection processes for biosecurity in shellfish hatcheries holding tetraploid Pacific oysters

Aquaculture today must meet the objectives of sustainable development. To avoid the dissemination of the tetraploid material from Magallana gigas cupped oysters, used in shellfish hatcheries for the production of triploid oysters, the producers must ensure biosecurity of their effluents in accordance with a French ministerial order. The objective of this study is to determine the specific UltraViolet doses required to inactivate gametes and larvae of tetraploid oysters, using low and medium pressure lamps. The experimental protocol includes the development of analytical methods by flow cytometry (markers of membrane integrity and apoptosis) and biological verifications by counting and characterization of the germinal cells under the microscope. Effective UV inactivation doses are 75 mJ/cm² for oocytes and 50 mJ/cm² for spermatozoa, using medium pressure lamps. With low-pressure lamp technologies, delivering twice the UV dose was required to achieve the same level of effectiveness. The differences observed between the two UV technologies could be probably due to the larger wavelength spectrum of medium pressure lamps. In the case of larvae, a higher and same dose of 150 mJ/cm² is required for both UV technologies. Further experiments should be conducted on larger samples of gametes, at doses between 75 and 150 mJ/cm² for larvae at different stages of development and using Light-Emitting-Diode Ultraviolet technology in order to save energy.