Impacts of oyster culture on microphytobenthos and its photosynthetic performances, benthic macrofauna and the role of estuarine erosion in oyster spat Crassostrea gigas mortality related to OsHV-1 μVar

• Main Author: Vanhuysse, Charles
• Other Authors: Normandie, Orvain, Francis
• Format: Thesis
• Language: French
• Published: 2019
• Subjects: Microphytobenthos; Macrozoobenthos; OsHV-1 µVar virus; Crassostrea gigas mortality; Sediment; Erosion; envir; geo; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: http://www.theses.fr/2019NORMC262/document

Since 2008, the mortality of Pacific oyster spat Crassostrea gigas has mainly been linked to the Ostreid herpesvirus 1 μvariant (OsHV-1 μVar). Environmental parameters favoring the persistence and spread of the virus could affect its propagation dynamics. The objectives of this thesis were to study in situ the interactions between oyster spat and their benthic environment during an episode of mortality. The photobiology of the microphytobenthos beneath the tables seemed to be in a better state compared to that observed in aisles that could promote viral resilience. The oyster tables attenuated light, temperature and desiccation, thus avoiding thermo and photoinhibition of the microphytobenthos. The benthic habitat environmental quality indices based on the macrozoobenthic community showed a degradation of the environment following the influx of organic matter induced by oyster spat mortalities and strandings of the macroalgae. A significant amount of OsHV-1 was found on the surface of the biofilm before the mortalities. Resuspension was preferentially associated with microphytobenthic particles with small currents. Depuis 2008, la mortalité des naissains d'huîtres Pacifique Crassostrea gigas est principalement liée au virus de l’ostreid herpesvirus 1 µvariant (OsHV-1 µVar). Les paramètres environnementaux favorisant la persistance et la diffusion du virus pourraient jouer sur sa dynamique de propagation. Les objectifs de cette thèse étaient d’étudier in situ les interactions entre les naissains d’huîtres et leur environnement benthique lors d’un épisode de surmortalité. La photobiologie du microphytobenthos sous les tables semblait en meilleur état comparé à celle observée dans les allées pouvant favoriser la résilience virale. Les tables à huîtres atténuaient la lumière, la température et la dessication évitant ainsi une thermo et photoinhibition du microphytobenthos. Les indices de la qualité environnementale de l’habitat benthique basés sur la communauté macrozoobenthique ont traduit une dégradation du ...