Ecological determinants of the occurrence and dynamics of Vibrio parahaemolyticus in offshore areas

Abstract

The life cycle of Vibrio parahaemolyticus has been conventionally associated with estuarine areas characterized by moderate salinity and warm seawater temperatures. Recent evidence suggests that the distribution and population dynamics of V. parahaemolyticus may be shaped by the existence of an oceanic transport of communities of this organism mediated by zooplankton. To evaluate this possibility, the presence of V. parahaemolyticus in the water column of offshore areas of Galicia was investigated by PCR monthly over an 18-month period. Analysis of zooplankton and seawater showed that the occurrence of V. parahaemolyticus in offshore areas was almost exclusively associated with zooplankton and was present in 80% of the samples. The influence of environmental factors assessed by generalized additive models revealed that the abundance and seasonality of V. parahaemolyticus in zooplankton was favoured by the concurrence of downwelling periods that promoted the zooplankton patchiness. These results confirm that offshore waters may be common habitats for V. parahaemolyticus, including strains with virulent traits. Additionally, genetically related populations were found in offshore zooplankton and in estuaries dispersed along 1500 km. This finding suggests that zooplankton may operate as a vehicle for oceanic dispersal of V. parahaemolyticus populations, connecting distant regions and habitats, and thereby producing impacts on the local community demography and the spread of Vibrio-related diseases.

Dynamics of Vibrio with Virulence Genes Detected in Pacific Harbor Seals (Phoca vitulina richardii) Off California: Implications for Marine Mammal Health

“…The differences in related environmental factors suggest that Vibrio exposure in seals may be related to other factors not measured in this study. Furthermore, the lack of seasonal variation for Vibrio prevalence in seals may indicate that seals may frequent reservoirs of Vibrio that are decoupled from seasonally influenced environmental factors measured here [27,55,86].…”

“…Changes in temperature and salinity commonly relate to the seasonal abundance and distribution of Vibrio in the water column [17,19,39,45,52,55]. However, turbidity and/or salinity best predicted Vibrio occurrence in harbor seals, although the relationship differed with location.…”

“…The turbidity maximum zone of SFB where freshwater inputs from the delta meet seawater is dominated by aggregations of particle-associated bacteria and plankton [41,42]. Vibrio can associate with plankton [45,55,86], therefore blooms following nutrient loading from the delta may relate to the abundance of Vibrio in SFB. It is unknown whether Vibrio in SFB are free-living, or form aggregations with plankton or particulate matter in the sediment.…”

“…Vibrio parahaemolyticus was detected most often in seals from ES, and can be pathogenic in fish and humans. Vibrio parahaemolyticus was shown to occur less frequently than other species of Vibrio from water and invertebrates sampled from ES [59], and may persist in greater concentrations in sediment, offshore zooplankton, and fish [19,45,55,86]. Therefore, resources and habitat in MB may be a source of greater concentrations of Vibrio parahaemolyticus.…”

“…Vibrio may persist in the water column, although greater concentrations of some pathogenic species of Vibrio have been observed in sediment, zooplankton, mussels, and fish [19,21,43,45,55,78]. In humans, enteric Vibrio infections are acquired by ingesting water or raw seafood that is contaminated with virulent or pathogenic strains of…”