Experimental evaluation of survival of Vibrio parahaemolyticus in fertilized cold‐water sediment

Aims: This experimental study focuses on survival and consistence of Vibrio parahaemolyticus in cold‐water sediments and how increasing temperature and nutritional availability can affect growth. Methods and Results: A pathogenic strain of V. parahaemolyticus was inoculated in seawater microcosms containing bottom sediment. Gradually, during 14 days, the temperature was upregulated from 8 to 21°C. Culturable V. parahaemolyticus was only found in the sediment but declined over time and did not recover even after another 2 days at 37°C. Numbers of culturable bacteria matched the amount found by q‐PCR indicating that they did not enter a dormant state, contrary to those in the water layer. After adding decaying phytoplankton as fertilizer to the microcosms of 8 and 21°C for 7 and 14 days, the culturability of the bacteria increased significantly in the sediments at both temperatures and durations of exposure. Conclusion: The study showed that V. parahaemolyticus can stay viable in cold‐water sediment and growth was stimulated by fertilizers rather than by temperature. Significance and Impact of the Study: Vibrio parahaemolyticus is a common cause of seafood‐borne gastroenteritis and is today recognized in connection to increasing ocean temperature. The results indicate that this pathogen should be considered a risk in well‐fertilized environments, such as aquacultures, even during cold periods.