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

Abstract

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 (GA₃) 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. GA₃ 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 GA₃ 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 GA₃ priming under varied seed conditions. As a simple, transferable pre-treatment, GA₃ 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 GA₃ 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.