Influence of OSHV-1 oyster mortality episode on dissolved inorganic fluxes: An ex situ experiment at the individual scale

• Published in: Aquaculture
• Main Authors: Richard, M, Bourreau, J, Montagnani, Caroline, Ouisse, V., Le Gall, P., Fortune, M., Munaron, D., Messiaen, G., Callier, M.D., Roque d'Orbecastel, E.
• Other Authors: MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Interactions Hôtes-Pathogènes-Environnements (IHPE), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Perpignan Via Domitia (UPVD)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Crassostrea gigas; Mortality; Ostreid herpesvirus 1; Juvenile; Spat; Mineralisation; Oxygen consumption; Nutrient fluxes; [SDV.BID.EVO]Life Sciences [q-bio]/Biodiversity/Populations and Evolution [q-bio.PE]
• Online Access: https://hal.archives-ouvertes.fr/hal-01510942; https://hal.archives-ouvertes.fr/hal-01510942/document; https://hal.archives-ouvertes.fr/hal-01510942/file/Richard-2017-Aquacult-Influence-MANUSCRIT.pdf; https://doi.org/10.1016/j.aquaculture.2017.03.026

International audience Ostreid herpesvirus 1 (OsHV-1 μvar) infection has caused significant mortalities in juvenile oysters (Crassostrea gigas). In contrast to the practices of other animal production industries, sick and dead oysters are not separated from live ones and are left to decay in the surrounding environment, with unknown consequences on fluxes of dissolved materials. A laboratory approach was used in this study to test the influence of oyster mortality episode on dissolved inorganic fluxes at the oyster interface, dissociating (i) the effect of viral infection on metabolism of juvenile oysters and (ii) the effect of flesh decomposition on oxygen consumption and nutrient releases at the individual scale. Nine batches of juvenile oysters (Individual Total wet weight 1 g) were infected via injection of OsHV-1 enriched inoculums at different viral loads (108 and 109 OsHV-1 DNA copies per oyster) to explore infection thresholds. Oysters injected with filtered seawater were used as controls (C). Oysters were maintained under standard conditions to avoid stress linked to hypoxia, starvation, or ammonia excess. Before, after the injection and during the mortality episode, i.e. at days 1, 3, 7, 10 and 14, nine oysters per treatment were incubated in individual metabolic chambers to quantify oxygen, ammonium and phosphate fluxes at the seawater-oyster interface. Nine empty chambers served as a reference. Injections of the two viral loads of OsHV-1 induced similar mortality rates (38%), beginning at day 3 and lasting until day 14. The observed mortality kinetics were slower than those reported in previous experimental pathology studies, but comparable to those observed in the field (Thau lagoon, France). This study highlights that oxygen and nutrient fluxes significantly varied during mortality episode. Indeed (i) OsHV-1 infection firstly modifies oyster metabolism, with significant decreases in oxygen consumption and ammonium excretion, and (ii) dead oysters lead to a strong increase of ammonium (6 fold) and ...