The highest amount of bacterial genera strains identified in this study comprised of Vibrio, Clostridum, and Pseudoalteromonas, while Nocardia, Fusobacterium, Mycobacterium and Planctomycetes were detected at lower levels. The high incidence of Vibrio spp., Clotridium spp., and Pseudoalteromonas spp., may indicate the influence of environmental factors in oyster groups. Of particular interest was the absence of Vibrio in atrazine treated groups, and the subsequent colonization by Nocardia, a known oyster pathogen. Conversely, none of the control groups (Acetone or non-exposed) exhibited an association with Nocardia. The only groups in which the presence of Nocardia was detected was those treated with atrazine at all three concentrations.