Gibberellic acid priming enhances Zostera marina seed germination: implications for restoration

Eelgrass ( Zostera marina ) meadows are foundational marine habitats that support biodiversity and provide key ecosystem services, including carbon sequestration, fisheries production, and shoreline stabilization. Yet, their global decline demands expanded restoration efforts. Seed-based restoration offers a scalable alternative to labor-intensive transplantation, but low germination and seedling emergence remain major constraints. Here, we tested gibberellic acid (GA 3 ) priming on dormant Z. marina seeds from three temperate North Atlantic populations (one intertidal annual population and two subtidal perennial populations) differing in origin, age, and handling history. GA 3 priming consistently improved germination success and reduced time to germination across all populations, with optimal responses at 9 and 20 mg L - ¹. Positive effects in the older seed cohort (stored for approximately 16 months) and in sterilized seeds suggest that GA 3 can mitigate physiological constraints associated with long-term storage or handling. Although the experimental design does not separate ecological from geographic influences, including populations from contrasting habitats provides a valuable test of GA 3 priming under varied seed conditions. As a simple, transferable pre-treatment, GA 3 priming shows strong potential to enhance seed readiness and increase nursery or restoration seed stocks, supporting more sustainable use of limited Z. marina seed resources. We further outline how GA 3 priming can be incorporated as a short immersion step within existing seed-handling workflows and provide a back-of-the-envelope consumables cost estimate to contextualize scale-up potential.