Optimising nursery conditions to promote seagrass production for large-scale restoration

Seagrass meadows are vital marine ecosystems that support biodiversity, stabilize sediments, and sequester carbon. However, their global decline has increased the urgency for effective restoration strategies. Seagrass nurseries offer a promising solution by supplying plant and seed material while reducing pressure on natural populations. Yet, nutrient limitation can constrain nursery productivity, highlighting the need for efficient, low-impact fertilization strategies. This study evaluated the role of nutrient enrichment in enhancing Zostera muelleri production in a nursery setting. The effects of different fertilizers (Osmocote and struvite) and the soil amendment zeolite on plant growth and photo-physiology were assessed. The aim was to identify nursery best practices to promote seagrass productivity for large-scale restoration. Here, Osmocote, even at low concentrations, significantly increased leaf surface area, shoot density, biomass and rhizome elongation, while no effect of struvite addition was observed. Zeolite enhanced Osmocote’s effect, likely by improving nitrogen retention and uptake. No significant effects on photosynthetic efficiency were observed following nutrient enrichment. These findings can be used to guide the development of effective Z. muelleri nursery protocols. Optimizing fertilization strategies can ultimately enhance the production of vegetative material and seeds for use in large-scale restoration efforts, contributing to the recovery of degraded seagrass meadows.