New consumer trends, market demands, and opportunities for multiple uses of macroalgae such as food, bioactive components for functional food and feed ingredients, fertilizers, and biofuels have strengthened the motivation for industrial macroalgae cultivation in Europe. The cultivation of kelp in sea requires production of seedlings on substrate to be deployed at sea farms. There are three main strategies for seedling production of kelp, aiming for seeding of the growth substrate with spores, gametophytes, or small sporophytes, whereof seeding with spores and gametophytes so far is the most incorporated techniques. Seeding with spores requires fertile sporophytes and this is seasonally dependent if these are collected in natural habitats, but fertility can also be induced by artificial day rhythm, and thus enables access to spores independent of natural seasons. Gametophytes can be kept in continuous cultures and be available for year-through seeding or production of microscopic sporophytes for direct seeding. This is advantageous as the use of incubation facilities on land can be shortened by several weeks or, in the case of direct seeding, omitted completely. The presented protocol focuses on Saccharina latissima seedlings production from spores and gametophytes and is adapted to the infrastructure and equipment that are available at typical aquaculture research laboratories, although some adjustments may be necessary to meet the needs of the different life stages.

Keywords: Saccharina latissima, cultivation, seeding, laboratory protocol, gametophyte cultures, contamination control, deployment