SEXPRIME_submitted.xlsx

Kelps are ecologically and economically important species, serving various purposes such as in the production of food, fertilizer, and bioplastics. As climate change alters ocean temperatures, optimization of kelp hatchery practices is essential for enhancing yield and resilience. This study investigates how maternal effects, driven by thermal priming, influence offspring growth and thermal tolerance. Clonal female and male gametophytes were exposed to 0°C, 10°C, and 20°C for three weeks in a common-garden experiment before crossing at 10°C. Fatty acid profiles of female gametophytes at the end of priming were analysed to investigate potential lipid provisioning. Sporophyte growth was monitored for 17 days at 10°C, followed by a 10-day heat stress at 23°C to assess thermal tolerance. Our findings showed that warm-primed female gametophytes had higher levels of neutral lipids, especially saturated fatty acids, while polar lipids, particularly polyunsaturated fatty acids, were lower. The fastest growing sporophytes originated from cold-primed gametophytes, but warm-primed gametophytes produced more sporophytes and enhanced their thermal tolerance. Maternal gametophytes were the main driver of offspring phenotypes with 14x higher explained variance for growth and 6x higher explained variance for thermal tolerance than paternal gametophytes. Cold priming of gametophytes in hatchery is recommended for higher yield in seaweed farming, while warm priming may aid restoration efforts in warming oceans, offering a cost-effective alternative complementary to selective breeding.