Wet season and monsoon rain events are associated with increased abundance of potentially pathogenic Vibrio spp. in a tropical estuary

The Vibrionaceae are found in most estuaries world-wide. Warming oceans have enabled the opportunistic pathogens, Vibrio parahaemolyticus and V. vulnificus, to occupy an increasing range of environments for longer periods of the year in temperate climate zones. However, little is known about their ecology in tropical regions. We studied spatio-temporal patterns and environmental drivers of abundance in V. parahaemolyticus and V. vulnificus in the monsoon tropics in water, sediment and the edible mangrove snail Telescopium telescopium . V. parahaemolyticus and V. vulnificus were more abundant during the wet season in three macro-tidal creek locations and all sample types, and this increase in abundance was associated with temperature. Interestingly, the abundance of V. parahaemolyticus in the sediment-grazing snail T. telescopium was correlated to V. parahaemolyticus concentrations in sediment rather than water. V. parahaemolyticus and V. vulnificus abundance were highest during a monsoonal rain event and some of these samples were positive for V. parahaemolyticus virulence genes. Our results suggest that the wet season, and in particular, times of extreme weather events when environmental conditions change rapidly, are potentially periods of high risk for vibriosis in tropical Australia, an area which is predicted to experience more frequent severe weather events. This work also expands our current understanding of the factors driving the abundance of potentially pathogenic Vibrio spp. in tropical estuaries. • V. parahaemolyticus and V. vulnificus levels are elevated in the wet season tropics. • Edible snail V. parahaemolyticus levels relate more to sediment than water. • Abundance peaks during monsoonal rains, with virulence genes detected. • High vibriosis risk in wet seasons, notably during severe weather events. • Climate extremes require ongoing Vibrio monitoring to reduce vibriosis risk.