Cold priming of Saccharina latissima gametophytes promotes sporophyte growth

Abstract Seaweed cultivation represents an emerging industry in Europe, where most biomass is still derived from wild harvesting. A potential approach to establishing a sustainable seaweed production industry involves improving seaweed strains. Temperature priming, introducing moderate stress to enhance subsequent performance, offers a rapid approach for improving growth. We examined the effect of three weeks temperature priming (0, 10, 20 °C) of gametophytes of Saccharina latissima on the early life stages (gametophyte growth, sporophyte recruitment, juvenile sporophyte growth). Cold priming (0 °C) stimulated gametogenesis and produced significantly larger microscopic sporophytes. This size advantage of the juvenile sporophytes was carried through a temperature gradient experiment (0–21 °C) over two weeks, especially under optimum temperatures (5–15 °C). In a second experiment with a similar gametophyte priming approach, we cultivated sporophytes for six months in mariculture and investigated size, biomass and biochemical composition. Biomass of sporophytes from 0 °C primed gametophytes was twofold higher than of 10, and fourfold higher than of 20 °C-primed gametophytes. The difference in mineral composition in sporophyte blades between priming treatments was variable. Heavy metals (As, Cd) were lower under warm priming (20 °C) and few macro- and trace elements (K, P, S, Mn) significantly increased under cold priming. The results demonstrate a transgenerational carry-over effect from haploid gametophytes to diploid sporophytes and underscore the significance of gametophyte cold exposure for the growth of S. latissima sporophytes. It suggests that cold priming of gametophytes may serve as a form of winter mimicry to enhance growth and to modify biochemical composition in kelp cultivation.