Significant mortality of Crassostrea gigas juveniles is observed systematically every year worldwide. Pacific Oyster Mortality Syndrome (POMS) is caused by Ostreid Herpesvirus 1 (OsHV-1) infection leading to immune suppression, followed by bacteraemia caused by a consortium of opportunistic bacteria. Using an in-situ approach and pelagic chambers, our aim in this study was to identify pathogen dynamics in oyster flesh and in the water column during the course of a mortality episode in the Mediterranean Thau lagoon (France). OsHV-1 concentrations in oyster flesh increased before the first clinical symptoms of the disease appeared, reached maximum concentrations during the moribund phase and the mortality peak. The structure of the bacterial community associated with oyster flesh changed in favour of bacterial genera previously associated with oyster mortality including Vibrio, Arcobacter, Psychrobium, and Psychrilyobacter. During the oyster mortality episode, releases of OsHV-1 and opportunistic bacteria were observed, in succession, in the water surrounding the oyster lanterns. These releases may favour the spread of disease within oyster farms and potentially impact other marine species, thereby reducing marine biodiversity in shellfish farming areas.

全世界每年系统地观察到Crassostrea gigas幼鱼的大量死亡。太平洋牡蛎死亡率综合症（POMS）是由Ostreid疱疹病毒1（OsHV-1）感染引起的，导致免疫抑制，其次是由机会细菌联合体引起的菌血症。使用原位方法和中上层室，我们在这项研究中的目的是在地中海Thau泻湖（法国）死亡期间识别牡蛎肉和水柱中的病原体动态。牡蛎肉中的OsHV-1浓度在该病的首次临床症状出现之前就已经增加，在垂死期和死亡高峰期达到最大浓度。与牡蛎肉有关的细菌群落结构发生了变化，有利于以前与牡蛎死亡率有关的细菌属，包括弧菌，弧菌，Psychrobium和Psychrilyobacter。在牡蛎死亡期间，在牡蛎灯笼周围的水中连续观察到OsHV-1和机会细菌的释放。这些释放可能促进疾病在牡蛎养殖场内的传播，并可能影响其他海洋物种，从而减少贝类养殖区域的海洋生物多样性。