The biofouling of surfaces submerged in the marine environment includes primary colonization of the substrate by microorganisms including bacteria, microalgae, and microscopic reproductive propagules of macroorganisms such as algal zoospores. The present study reports the evaluation of the inhibitory potential of biofilms and extracellular products (EP) of the indigenous bacterium Alteromonas sp strain Ni1-LEM on the settlement of marine biofouling such as: (i) eight marine benthic diatoms and (ii) zoospores of the alga Ulva lactuca, as well as the germination of these zoospores and was compared with reference strains with proven antifouling properties, Halomonas marina (ATCC 25374) and Pseudoalteromonas tunicata. Highest antifouling activity was found for the indigenous strain. In attempts to better define the chemical nature of the *Corresponding author antifouling substance in the EP of the Alteromonas sp strain Ni1-LEM, the culture filtrates were tested for activity after heat treatment, enzymatic treatments, dialysis through semipermeable membranes, and separation into polar (aqueous) and non-polar (organic) fractions. The results suggested that the antifouling substance in the culture filtrates to be protein or peptide in nature, thermostable, hydrophilic, and equal to or greater than 3500 daltons in molecular size. Antifouling substances from bacteria may lead to the development of novel antifouling agents in the future.Living and inert surfaces immersed in the marine environment are usually rapidly colonized by microorganisms, the first step of which includes attachment of bacteria, diatoms, fungi, and protozoans. These are often

In this study, we evaluate the use of macroalgae as vectors of probiotics bacteria into the digestive tract of abalone to improve their survival and growth. It is shown that when abalone Haliotis rufescens of di¡erent sizes were fed with a natural diet composed of fronds of the macroalga Macrocystis integrifolia supplemented with a mixture of Vibrio sp. C21-UMA, Agarivorans albus F1-UMA and Vibrio sp. F15-UMA bacteria, there was a signi¢cant increase (Po0.05) in the average monthly growth rate and survival (%)in a period of 210 days, compared with the control without a probiotic supplement. The permanence of the probiotics in the digestive tract of the animals was monitored, and it was found that the number of culturable C21-UMA and F1-UMA bacteria decreased signi¢cantly (Po0.05) in recently weaned and adult abalone, and they almost disappeared completely on day 19 of the bioassay. However, the culturableVibrio sp. F15-UMA disappeared completely from the digestive tract on day 22 of the bioassay, and these were the bacteria that remained at the highest concentration compared with the other two bacterial strains over the experimental period. It is therefore shown that it is feasible to use a probiotic mixture to improve the pro¢tability of the H. rufescens culture.

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