A simple and effective protocol for cryopreservation of germplasm of the bull kelp, <i>Nereocystis luetkeana</i> (Phaeophyceae)

Kelps are large brown seaweeds that can form three-dimensional underwater forests that provide food and habitat for a wide diversity of marine organisms. They also provide a wealth of ecosystem services to humans and may be able to help combat climate change through blue carbon. However, kelps are currently in decline in many parts of the world, most likely due to rising ocean temperatures, and conservation action is needed quickly to preserve kelp biodiversity. One kelp conservation strategy that needs further development is biobanking, the storage of biological material. In particular, the development of cryopreservation protocols would permit easier storage of large quantities of kelp germplasm under stable conditions. In this paper, we compare the effectiveness of different cryoprotective agents-chemicals that mitigate the damaging effects of freezing on living tissue-for use in cryopreservation of gametophyte tissue of the bull kelp, Nereocystis luetkeana. We observed that when cryopreserved in a solution of 10% ethylene glycol + 9% sorbitol, Nereocystis gametophytes of both sexes showed excellent survivorship 6 weeks after removal from cryogenic conditions. Although kelp cryopreservation protocols still need to be further researched, we believe that these methods have great potential to improve and expand kelp biobanking, and we would encourage the development of protocols for more kelp species as well as more widespread adoption of cryopreservation by existing kelp biobanking efforts.