Influence of substrate and burial on the development of Posidonia oceanica: implications for restoration

Posidonia oceanica is one of the few seagrasses that can colonize hard and soft substrates. To test whether substrate could affect root development of the seedlings, with a legacy effect upon transplantation to sand, we germinated seeds on hard (glass slide) versus soft (sand) substrates in microcosms. We found that sand favored root system development, with a compensatory slowing of leaf development, while glass had the opposite effect. After 4 months, we transplanted all seedlings to sand and tested for a legacy effect of initial substrate type. Leaves of seedlings germinated on sand and glass slides reached approximately the same length, but roots from seedlings germinated on glass did not develop fully. Seed burial (0–1.5 cm) did not affect seedling development. These results suggest that the culture of P. oceanica on sand prior to transplantation could enhance seedlings survival in restoration programs.