Gametophyte adherence

<b>How sticky is sticky? A note on gametophyte adherence of the macroalga </b><b><i>Saccharina latissima</i></b><b> (Phaeophyceae)</b>Eoghan Mánus Cunningham^1,2*, Pamela J. Walsh^1,2, Louise Kregting³Temperate marine systems are ideal environments for expanding global seaweed aquaculture, yet high costs, particularly from macroalgal nursery facilities, have become a limiting factor for industry development. Recent research has explored the use of binder-seeding, whereby juvenile kelp life stages are seeded directly onto rope using adhesive solutions and deployed directly at sea. This method is used to reduce our reliance on nursery facilities and reduce aquaculture costs. While binder-seeding has shown mixed results, a more simplistic approach by Klaus Lüning has received less attention. Klaus Lüning (1979) commented that kelp gametophytes were naturally ‘sticky’ and attach to substrata within ‘a short time’, potentially highlighting a natural and more cost-effective seeding technique. Here, we explored the natural adherence of <i>Saccharina latissima </i>gametophytes to aquaculture twine. Cultures were sprayed onto twine and left to adhere for eight increasing time periods, before being submerged in seawater and measured after 10 weeks of growth. Gametophytes were found to adhere and grow successfully on twine after immediate submergence in seawater, however significant differences in sporophyte lengths and density after 10 weeks growth were observed among time treatments. Sporophyte lengths and densities were found to be highest when the culture was left to adhere for 30 minutes prior to submergence in seawater, potentially highlighting a time-sensitive sweet spot for natural gametophyte seeding. Further, we confirm that Lüning’s observation of kelp gametophytes sticking to substrata after a ‘short time’ was in fact ‘immediate’, thereby shorter than previously thought.