The mangrove oyster (Crassostrea gasar) feeds by filtering suspended organic particles, microalgae, phytoplankton and bacteria, which provide essential nutrients for the mollusk's growth and survival. The process of bacterial colonization in the oyster gut is complex and directly influenced by the microbiome of the aquatic habitat. The C. gasar species is indigenous to the Atlantic coast of Brazil and is prevalent in the mangrove ecosystems of the Amazon region, where it is farmed. Oysters are a globally consumed seafood, and = farming this species in the Amazon contributes to the economy and livelihoods of traditional communities. In this study, we employed a high phylogenetic resolution metabarcoding approach to describe the richness, structure and dynamics of the bacterial communities associated with the oyster gut and the aquatic habitat in which they reside.