Such organization of the microbiota in abalone digestive gland consists of two groups of bacteria: one resident group comprising the dominant bacteria and another one comprising the less abundant diet-specific bacteria and rarer bacteria which are transient over the year. Dominance of few bacterial taxa in the digestive microbiota may contribute to holobiont health and, as proposed in the case of human gut microbiota, such stability may allow for a certain resiliency in response to invasive pathogens or other exogenous microbes [1, 3]. Further, the presence of less abundant taxa may also participate in abalone holobiont health. Previous studies on human lung- or plant-associated microbes showed that rare species were also involved in host protection against pathogens [66, 67]. On another hand, in a case of a disturbance strong enough to destabilize the core microbiota, these rarer OTUs may become more abundant and fill the niche previously occupied by the dominant bacterial community. They can either fill the same functions as the core microbiota and contribute to holobiont health or become pathogens [3, 68].