Survival of hatchery grown native oysters is associated with specific gut-associated bacteria at various locations within the Puget Sound

The Olympia oyster (Ostrea lurida) of the Puget Sound suffered a dramatic population crash, but restoration efforts hope to revive this native species. One overlooked variable in the process of assessing ecosystem health is association of bacteria with marine organisms and the environments they occupy. Oyster microbiomes are known to differ significantly between species, tissue type, and the habitat in which they are found. The goals of this study were to determine the impact of field site and habitat on the oyster microbiome and to identify core oyster-associated bacteria in the Puget Sound. Olympia oysters from one parental family were deployed at four sites in the Puget Sound both inside and outside of eelgrass (Zostera marina) beds. Using 16S rRNA gene amplicon sequencing of the oyster gut, shell, surrounding seawater and sediment, we demonstrate that gut-associated bacteria are distinct from the surrounding environment and vary by field site. Furthermore, regional differences in the gut microbiota are associated with the survival rates of oysters at each site after two months of field exposure. However, habitat type had no influence on microbiome diversity. Further work is needed to identify the specific bacterial dynamics that are associated with oyster physiology and survival rates. ImportanceThe outcomes of this study demonstrate the need to monitor microbial ecology at potential oyster restoration sites, specifically for the native Olympia oyster in the Puget Sound. Some areas of Puget Sound may be less amenable to Olympia oyster restoration than others due to microbiome colonization trends. Furthermore, this study puts the oyster microbiome in the context of its surroundings, providing a holistic perspective on the factors that may influence oyster performance and microbial ecology.