Stochastic processes dominate marine free-living Vibrio community assembly in a subtropical gulf.

Understanding the effects of eutrophication on heterotrophic bacteria, a primary responder to eutrophication, is critical for predicting the responses of ecosystems to marine environmental pollution. Vibrio are indigenous in coastal water and of significance to geochemical cycling and public health. In this study, we investigated the diversity and assembly features of Vibrio, as well as their relationship with the environmental factors in the subtropical Beibu Gulf. We found that the alpha diversity of Vibrio increased in parallel with the trophic state they occupy. A Mantel test indicated that the trophic state was correlated to Vibrio beta diversity and the correlation gradually strengthened at higher trophic states. Variation partitioning analysis suggested that the geographic distance was an important factor impacting the variables of Vibrio communities in all the samples, but nutrients exerted more influence in the more highly eutrophic samples. Our results demonstrated that stochastic processes govern the turnover of marine Vibrio communities in the Beibu Gulf and that ecological drift was the most important process for assembly of the Vibrio communities.