Vibrio harveyi is the main pathogen of the European abaloneHaliotis tuberculata, and recently caused important mortalities at theproduction sites of this marine gastropod in France. In the present work, the monthlyantibacterial activity of two red seaweed species from the French Atlantic coast, thenative Palmaria palmata and the introduced Grateloupiaturuturu, were investigated against the abalone pathogen Vibrio harveyistrain ORM4. Water-soluble extracts were screened using the microplate method.Grateloupia turuturu showed an antibacterial activity with a maximalgrowth inhibition in spring of around 16%. In contrast, Palmaria palmatawas inactive, as further growth of the bacteria was observed. Preliminaryone-dimensional proton nuclear magnetic-resonance (1H NMR) profiles identified thedifferences between the two water-soluble extracts.
