Vibrios associated with plankton in a coastal zone of the Adriatic Sea (Italy)

From April 1996 through March 1997, culturable vibrios associated with both large (>200 µm) and small (0.45–200 µm) size plankton collected in the Ancona, Italy, coastal zone of the Adriatic Sea were studied. Vibrio alginolyticus was readily cultured from large size plankton from July to September and represented the only Vibrio species that could be cultured under the conditions employed in the study. Crustaceans (mainly copepods) and tunicates ( Oikopleura spp.) comprised the larger sized plankton, with copepods being 90% of the total plankton population in the summer months. Diatoms ( Chaetoceros spp.) were also present but in lower numbers. Vibrios associated with smaller sized plankton comprised mainly V. alginolyticus during June—September and in March, whereas Vibrio vulnificus was isolated from samples collected in April, May, and March. The smaller size plankton comprised predominantly tintinnids, nauplii of crustaceans and exuvia of copepods. These results confirm the role of zooplankton as hosts of vibrios in the environment, and suggest that smaller sized plankton may serve as an important reservoir of these bacteria.