1. Epimicrobial communities on seaweed surfaces usually contain not only potentially pathogenic, but also potentially beneficial microorganisms. Capacity of terrestrial plants for chemically mediated recruitment i.e. ‘gardening’ of bacterial communities in the rhizosphere was recently demonstrated. Empirical evidence directly linking such chemical ‘gardening’ with the beneficial role of gardened microbes in terrestrial plants is rare and largely missing for aquatic macrophytes. 2. Here we demonstrate that our model invasive seaweed holobiont Agarophyton vermiculophyllum possesses beneficial...