In-Culture Selection and the Potential Effects of Changing Sex Ratios on the Reproductive Success of Multiannual Delayed Gametophytes of Saccharina latissima and Alaria esculenta

Abstract

Multiannual delayed gametophyte cultures can stay vegetative for years, while also having the ability to grow. This study aims to investigate whether male and female multiannual delayed gametophyte strains of the species Saccharina latissima and Alaria esculenta grow at different rates in culture. We furthermore assessed how changing sex ratios can affect the reproductive yields of these cultures. The results indicate that the reproductive yield of cultures declines with decreasing male:female ratios, a correlation that becomes especially apparent at higher culture densities for both species. Female gametophyte densities in particular affected the observed reproductive yield of the cultures, with S. latissima cultures showing a clear reproductive optimum (sporophytes·mL−1) at 0.013 mg·mL−1 DW female gametophyte biomass, while the reproductive success of A. esculenta peaked at a density of 0.025 mg·mL−1 DW of female gametophyte biomass, after which the reproductive yield started to decline in both species. The results show that the sex ratio of a gametophyte culture is an important biotic life cycle control, with higher amounts of female gametophyte biomass halting gametophyte reproduction. Understanding how these changing sex ratios in gametophyte cultures affect reproduction is especially important in the aquaculture of kelp, where reliable preforming cultures are key to long-term success.

Thermal performance curves identify seasonal and site‐specific variation in the development of Ecklonia radiata (Phaeophyceae) gametophytes and sporophytes

“…The usefulness of these findings for aquaculture nurseries both in a commercial or restoration context mostly depends on the persistence of the observed differences in gametophyte growth into the sporophyte life stage (Gauci et al., 2022; Liesner et al., 2020). Effects of long‐term vegetative cultivation, such as selection based on different growth rates of male and female gametophytes, are further complicating factors that might prohibit the retention of initial beneficial properties of the collected strains in the long term (Ebbing, Fivash, et al., 2021). The observed variation, furthermore, highlights the importance of diverse gametophyte cultures from multiple parents and, ideally, multiple populations collected at various times of year for aquaculture nurseries as well as the need to consider temporal and spatial variation in gametophyte performance when modeling kelp populations.…”

The sugar kelp Saccharina latissima II: Recent Advances in farming and applications

“…This method is advantageous as incubation facilities can be shortened by several weeks or omitted completely by direct seeding using a binder to adhere the propagules to the substrate. A considerable amount of research has been undertaken over the recent years to understand the gametophyte biology, development and quality relating to several biotic and abiotic factors, such as age, density, seasonality, sex ratio, light, temperature, and nutrients (Nielsen et al 2016a;Ebbing et al 2020Ebbing et al , 2021aRaymond and Stekoll 2021;Boderskov et al 2022). A bioreactor system that overcomes several implementation challenges for this controlled reproductive method, expanding the possibility of clonal gametophyte cultivation outside of expensive laboratory settings, has been validated (Ebbing et al 2022).…”