show Abstracthide AbstractWater samples were collected in the Northern Adriatic Sea (Gulf of Trieste) at the location of the oceanographic buoy 'Vida' during monthly sampling (from October 2018 to February 2016 to December 2021). Seawater (~ 1L) was filtered onto 0.2 µm polyethersulphonic filters. DNA was extracted and the hypervariable V4-V5 region (515F-Y, 926R) of the bacterial 16S rRNA was amplified. Sequencing was performed on the Illumina Miseq platform (2 × 300 bp pair-end).