Multi-species seagrass transplantation in salt-production lagoons: lessons for design, cultivation and restoration

Seagrasses are marine flowering plants that form meadows across shallow seabottoms worldwide. These communities provide essential ecosystem services, including coastal protection, support to fisheries, high biodiversity, and carbon sequestration. However, global seagrass decline contrasts with the limited scalability of current restoration efforts, which often rely on harvesting material from natural donor meadows or small-scale cultivation/nursery facilities. This dependency limits restoration potential and places additional pressures on vulnerable ecosystems. This study focuses on establishing seagrass habitats within salt-production lagoons in southern Portugal. The approach aims to create long-term seagrass sanctuaries in underused lagoons while assessing their seagrass cultivation potential. Three native species, Cymodocea nodosa, Zostera marina, and Nanozostera noltei, were introduced and monitored. Standardized experiments tested different transplantation densities and fragment spacing configurations for C. nodosa and Z. marina to assess establishment success and cultivation approaches, including handling practices. For N. noltei, transplantation followed a chessboard approach, transferring material from intertidal donor meadow into subtidal lagoon conditions. Preliminary results suggest that sheltered lagoons can provide favourable conditions for early-stage establishment by reducing hydrodynamic stress while enabling survival and growth monitoring. At the same time, practical challenges emerged, including plant loss, breakage, herbivory, and maintaining suitable lagoon conditions. This work highlights the potential of sheltered lagoon systems to support long-term seagrass establishment while providing practical insights into seagrass cultivation, transplantation density and fragment handling. The findings contribute to the development of scalable and low-impact approaches that can support European restoration targets and future seagrass conservation and restoration efforts across dynamic coastal systems.