Association of Vibrio community with the Atlantic Mediterranean invasive alga Caulerpa cylindracea

In aquatic environments, vibrios are among the most abundant culturable microbes found either as free-living or associated with several marine organisms. The diseases due to some pathogenic vibrios are increasing worldwide thus the understanding of the mechanisms related to their spread is critically needed. In the present study, the abundance as well as the diversity of culturable vibrios associated to the surfaces of the green alga Caulerpa cylindracea (Sonder) were analyzed during different stages of algal development. The Vibrio densities ranged from 1.9 x 10(3) CFU to 2.2 x 10(4) CFU mL(-1). The Vibrio strains isolated from C. cylindracea surfaces were assigned to: Vibrio tubiashii, Vibrio neptunius, Vibrio rotiferianus, Vibrio communis, Vibrio owensii, Vibrio jasicida, Vibrio harveyi, Vibrio maritimus, Vibrio diabolicus, Vibrio campbellii, Vibrio pomeroyi, Vibrio crassostreae, and Vibrio aestivus. Although some of the species recovered can be pathogenic to benthic marine organisms, none is considered human pathogens. Only few of the isolated vibrios (V. campbellii, V. aestivus, V. pomeroyi and V. crassostreae) have a sporadic presence on the algal surfaces (i.e. they were found only during one sampling event) while most of the isolates were found in all the four sampling times. The association of these last Vibrio species and the surfaces of C cylindracea needs to be elucidated in order also to ascertain whether vibrios might contribute to the successful spreading of the algal species.