Water motion as a conditioning mechanism to improve the yield of the sugar kelp Saccharina latissima (Phaeophyceae)

Mariculture grown seaweed production still falls short of the demand needed for traditional and novel applications of seaweed. When growing seaweeds, some water motion (wave and/or current), as opposed to static conditions, has been shown to enhance seaweed growth in an aquaculture setting. Hence, we aimed to determine how water motion influences the growth of Saccharina latissima in the nursery stage of seaweed aquaculture. We exposed seeded gametophytes of S. latissima to either oscillatory water motion or static water conditions during the early-life nursery setting and tested how this affected overall growth in a follow-up field study. At the end of the initial nursery experiment, we found that water motion increased the overall density of sporophytes, whereas the static conditions increased sporophyte length. During the field harvest, only the stipe length of the seaweeds differed significantly between treatments, however, both the total sporophyte biomass and density were significantly higher, ~17 and ~13 %, respectively, in kelps that were pre-conditioned in oscillatory water motion in the nursery. We demonstrate that oscillatory water motion at the nursery phase can increase the yield of sea-grown kelp in a mariculture setting, as it may have allowed them to adapt and grow more efficiently once deployed at sea.