INNOVATING METHODS FOR STAGGERING KELP OUTPLANTINGS BY MODIFYING SEED STRING GROWING CONDITIONS

Kelp farming has the potential to economically diversify coastal communities of Alaska while offering potential ecosystem services, including carbon sequestration and mitigating eutrophication. Our research is focused on identifying methods to control early life stages of kelps, including Saccharina latissima and Alaria marginata in order to optimize kelp seed production. Storage of seeded string could be used for staggering kelp outplanting from the kelp hatchery to ocean farm providing more flexibility and enabling more control of timing in the seeding and outplanting process. As part of this research we are addressing two questions.

1) How can we slow gametophyte growth and reproduction in a hatchery setting?

2) How does storage in conditions that stall gametophyte growth and reproduction affect the viability of the seed string when outplanted?

To evaluate question 1, we tested removing iron from the culture medium or filtering out blue light, varying light intensity and temperature. We found that low temperature is most effective at delaying both gametogenesis and slowing gametophyte growth subsequently is the best candidate condition for seed storage. We also found gametophyte growth to be highly dependent on the month of seeding (Fig. 1). Following these results, we approached question 2 by growing kelp seed string under a positive control and four storage treatments comprised a combination of low temperatures and varying nutrient conditions.

Preliminary results suggest one storage treatment (at low temperature and full nutrients) was successful. We extended seed storage for an additional 35 days beyond the positive control without adverse effects to sporophyte density and length at the time of outplanting and up to 3 weeks after outplanting. Our results provide a storage method for hatcheries that will give more flexibility and the ability to stagger kelp outplanting from the same sporophyte brood stock.