Dynamics of bacterial and Vibrio communities in Blacklip Rock Oysters in the seasonal tropics

Cultivation of the tropical Blacklip Rock Oyster (BRO) (Saccostrea spathulata) is an emerging Indigenous-led aquaculture industry in the seasonal tropics of northern Australia. However, little is currently known about the potential for pathogen outbreaks in this species. We conducted a year-long study in order to establish a microbial baseline to identify potential oyster and human health risks to inform future food safety decision making in this nascent industry. In healthy oysters, we identified both the core microbiome of this oyster species and the presence of potential oyster and human pathogens. The core bacteriome comprised of nine bacterial families, while the core vibriome comprised of Vibrio harveyi and V. owensii, which are known animal pathogens. The potential human pathogen V. parahaemolyticus was detected in some oysters during the wet season, during periods of increased rainfall, turbidity and total nitrogen. The bacteriome and vibriome of oysters was significantly different to the adjacent seawater and therefore we conclude that seawater is not an appropriate surrogate for pathogen risk surveillance in this developing industry. These results will inform monitoring methods, harvesting and shellfish quality compliance in this emerging Indigenous-led industry.