Improved Palmaria palmata hatchery methods for tetraspore release, even settlement and high seedling survival using strong water agitation and macerated propagules

Cultivated Palmaria palmata is highly valued as a nutritious source of biomass. Yet, current hatchery techniques using tetraspores show low spore-to-seedling efficiency, normally imposing a high requirement of sori for seeding in large-scale cultivation, and pointing to a need for developing current hatchery techniques.

This study shows new hatchery strategies to improve tetraspore release, efficiency of spore use as well as seedling distribution on seeded substrates for P. palmata cultivation, based on germination, maceration and agitation (GMA-method). We showed increased spore yield by using high-agitated sporulation tanks (67,906 ± 11,303 spores g FW−1) compared to calm water (17,889 ± 3652 spores g FW−1).

In addition, twine substrates cultured in high water agitation (2.5 L air min−1) resulted in highest settlement and dispersal of spores and seedlings compared to non-agitated cultures. Using alginate coated twine showed no effect after 70 days nursery growth, despite higher initial spore density after a 22 days spore release phase in some treatments.

Spore release time did not affect spore yield when comparing 1 and 3 h, whereas the yield increased during long-term sporulation (22 days) in some treatments. Released tetraspores settled in dense aggregates that germinated into a mixture of spores and seedlings (propagules) during 30 days and showed an ability of discoid re-attachment and growth after a maceration pretreatment.

Here, the level of water agitation affected the re-attachment success and 39% of the added seedlings reattached after 14 days of nursery. The cultivation strategies presented here provide a way to increase the overall spore-to-seedling survival and might serve as a new seeding strategy for P. palmata.

Present findings are important knowledge in the quest of optimizing large-scale hatchery production of P. palmata.