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Environmental influences on the seasonal distribution of Vibrio parahaemolyticus in the Pacific Northwest of the USA
Citation:
Paranjpye, R., W. Nilsson, M. Liermann, E Hilborn, BJ George, Q. Li, B. Bill, V. Trainer, M. Strom, AND P. Sandifer. Environmental influences on the seasonal distribution of Vibrio parahaemolyticus in the Pacific Northwest of the USA. FEMS Microbiology Ecology. Elsevier Science Ltd, New York, NY, 91(12):1, (2015).
Impact/Purpose:
Pathogenic Vibrio spp. are environmental contaminants of marine and estuarine waters. Occurrence has been reported to be positively correlated to water temperature. Therefore an increase in Vibrio occurrence and exposure was a concern for continued climate change during which coastal water temperatures are expected to increase. We sampled sites in and around Puget Sound for evidence of Vibrio over a two year period. In contrast to the literature, although Vibrio occurrence was highest in summer months, Vibrio was not associated with temperature in multivariable models, but silicate was identified as being negatively associated with Vibrio occurrence. Interestingly, Vibrio binds to chitin in aquatic chitin –producing organisms, which may increase chitin production in low silicate environments. While Vibrio is expected to increase in occurrence as climate change progresses, the reasons may not be simply that warmer waters support greater Vibrio concentrations; predictors of Vibrio occurrence are complex, and feedback loops in the aquatic community may enhance occurrence.
Description:
Populations of Vibrio parahaemolyticus in the environment can be influenced by numerous factors. We assessed the correlation of total (tl+) and potentially virulent (tdh+) V. parahaemolyticus in water with three harmful algal bloom (HAB) genera (Pseudo-nitzschia, Alexandrium and Dinophysis), the abundance of diatoms and dinoflagellates, chlorophyll-a and temperature, salinity and macronutrients at five sites in Washington State from 2008-2009. The variability in V. parahaemolyticus density was explained predominantly by strong seasonal trends where maximum densities occurred in June, 2 months prior to the highest seasonal water temperature. In spite of large geographic differences in temperature, salinity and nutrients, there was little evidence of corresponding differences in V. parahaemolyticus density. In addition, there was no evident relationship between V. parahaemolyticus and indices of HAB genera, perhaps due to a lack of significant HAB events during the sampling period. The only nutrient significantly associated with V. parahaemolyticus density after accounting for the seasonal trend was silicate. This negative relationship may be caused by a shift in cell wall structure for some diatom species to a chitinous substrate preferred by V. parahaemolyticus. Results from our study differ from those in other regions corroborating previous findings that environmental factors that trigger vibrio and HAB events may differ depending on geographic locations. Therefore caution should be used when applying results from one region to another.
